Solar Power World - MAY 2013

Project Review: How to Harvest Solar p.32

Engineering Developments: The Rise of Organic PV p.42

Business Issues: Buy vs. Lease: A Study p. 46

May 2013 www.solarpowerworldonline.com

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Editorial Advisory Board Natalie Holtgrefe Solectria Renewables Jose Gomez Ingeteam Steve Hogan Spire Devon Cichoski SolarWorld Marcelo Gomez Unirac Justin Barnes North Carolina (State University) Solar Center Scott Wiater Standard Solar

What do you think?

Discuss this, and other solar issues at www.engineering exchange.com

THE

FI RS T

WO RD

You Can’t Manage What You Don’t Monitor I thought 2013 was supposed to be a slow year for the solar industry.

The latest study from GTM Research and SEIA says the U.S. solar market grew a whopping 76% in 2012. That means solar has become the fastest-growing energy segment in the United States.

That’s a seriously impressive number. Congratulations to all of you for this momentous achievement. But as the prolific French philosopher and impertinent gadfly Voltaire once wrote, “With great power comes great responsibility.”

With so much solar being installed at an ever-increasing rate, it’s fair to ask: How are we going to track the performance of these systems so the long-term health of this growing industry isn’t undermined by poorly producing systems?

The answer is obvious if you think about it: Operators should monitor the systems they install.

“We have a saying around the office: What you monitor matters,” says Robert Schaefer, CEO of Also Energy in Boulder, Colo. “The financial folks in particular have a great deal of interest in getting this information. They’ve put the money up to fund these projects, and now they’re on the hook if they don’t perform as advertised.”

And that is the central issue facing installers, large and small, today. With the advent of leases and other third-party ownership options, it is increasingly coming back to the installation companies/leaseholders to make sure they are delivering the amount of power they commit to in their agreements.

“We like to refer to third-party operators like SunCity and others as fleet managers, just like companies who own fleets of cars,” says Adrian De Luca, VP of sales and marketing for Locus Energy in Hoboken, N.J. “They have incredible numbers of arrays to look after and ensure production. These are the companies who need this data most.”

Access to instantaneous information can certainly be a boon to electricity providers, but it also holds potential pitfalls, as anyone who has cable TV with 300 channels can attest. I firmly hold the belief that there is such a thing as too much information, and being overwhelmed by the data is a risk operators assume.

“Raw data, by itself, is largely useless,” says Richard Duong, product engineer for Moxa Americas in Brea, Calif. “You have to have it in context for it to be of any use to you.”

How well you monitor your installations could be the difference between having your business succeed or fail. Don’t let it fail — monitor and manage your systems.

You can hear more from Schaefer, De Luca and Duong in our cover story, “The Pressure to Perform.”

Frank Andorka

Editorial Director fandorka@solarpowerworldonline.com

www.solarpowerworldonline.com

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[ SO L AR

{

W OR K S ]

Solar Works Around The United States The solar industry is right to brag about 2012. Installations grew 76% last year, totaling 3.3 GW nationwide. SEIA attributes the growth in part to increased use of residential solar leases and the commissioning of mega-scale solar plants. Analysts say the industry can look forward to this year, too. “Solar will move into the No. 2 position in terms of new [generating capacity], second only to gas,” Recurrent CEO Arno Harris told Bloomberg News. This is what’s happening now:

This Farm Is A Winner Bainbridge Island, Wash.

Wind And Solar, Together Forever Grand Ridge, Ill.

Patriotic Panels Washington, D.C.

Romerkoff Farms made an aesthetic and energy conscious statement with a 12-kW solar array on a new barn. Installer A&R Solar chose SunPower modules because the cells’ blue hue contrasted with the roof’s red rust. The project won SunPower’s 2012 Residential Intelegant Award, which recognizes aesthetics, quality and performance.

When it opens, Invenergy’s 23-MW Grand Ridge Solar site will be the largest solar project in the Midwest. GE has supplied thin-film panels for the installation, which is being built by White Construction. The farm is adjacent to the Grand Ridge Wind project, which uses GE 1.5-MW turbines.

First Power and Light completed a 147-kW system at the 74-year-old Mary Switzer Building, which houses various government departments. Company sales manager Jerry Wenger says he had hoped the installation’s Motech panels, which are made in Delaware, would get recognition from Vice President Joe Biden.

Jail Time For Robot Dublin, Calif.

➛

Robot-maker QBotix unveiled its first commercial installation at the Alameda County Santa Rita Jail. The 48-kW project uses one SolBot, which adjusts panels to achieve maximum efficiency. Signal Energy developed the project.

Massive For Montana Missoula, Mont.

Sunelco Solar lifted 348 panels to the top of a downtown parking garage, building the largest solar project in the state. The 85-kW array will provide the garage with up to 80% of its electricity needs. NorthWestern Energy helped pay for the $245,000 project, which developers say was a local effort.

➛

➛ REC Solar has led installations at 12 public schools in the state, totaling 3.5 MW. The power will reduce schools’ electric bills by up to 20% and offer educational opportunities.

“Solar is a cost-effective upgrade for schools nationwide,” says Cary Hayes, REC’s director of business development.

The Laurel, a historic building downtown, is using 184 FlexLight laminate panels and a little Velcro to be more energy efficient. Kirberg Co. used Velcro to install the 25-kW system on a flat roof. “We were able to make the Laurel Building — and St. Louis — a better, greener place to live,” says company president Eric Kirberg.

Solar Elephants Knoxville, Tenn.

The Knoxville Zoo and partners installed 196 solar panels across the barn roof of the Stokely African Elephant Preserve habitat. ARiES Energy partnered with the zoo and local businesses Wampler’s Farm Sausage and Family Brands International to install the 50-kW system.

➛

Global EPC Comes Home Orlando, Fla. Florida-based ESA Renewables installed a 417-kW system at Orlando’s fleet maintenance building. Construction of the 1,392-module rooftop system brought 20 jobs to the city and will provide $800,000 in energy cost savings over its lifetime. Power is sold to the city’s utilities commission under a 25-year PPA.

www.solarpowerworldonline.com

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➛

The Laminated Laurel St. Louis, Mo.

Schools Save With Sun Power Tempe, Ariz.

➛

➛

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ASO FSO

Solar Fuse and Fuseholder Combo

gPV

October 2011 • vol 1 no 1 EDITORIAL

SALES

Editorial Director

Key Account Manager

Frank Andorka • 440.234.4531 x110 fandorka@wtwhmedia.com

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The ASO solar fuse protects PV Systems up to 1000 VDC according to the latest gPV requirements – – – – – –

meets both UL 2579 and IEC 60269-6 Standard midget 10.3 x 3.8mm Quick-acting according to UL 248-14 Current rating ranges from 1-30A @ 1000 VDC Breaking capacity 20kA Touch safe fuseholder mounts on DIN rail or accepts 8-14 AWG standard wire; 1-, 2-, or 3-poles available

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SOLAR POWER WORLD

10 • 2011

w w w. s o l a r p o w e r w o r l d o n l i n e . c o m

May

contents

58

D e pa r t m e n t s

03 Solar Works

10 Marketing 12 Training 14 Contractor’s Corner 58 Developments 62 Products 66

4 Questions

v o l

3

n o

2

F e at u r e s

01 The First Word

08 Future of Finance

•

22

16 Don’t Be Fooled Learn how to identify true AC solar modules from the pretenders.

About the Cover: AlsoEnergy of Boulder,

22 Aluminum Outfitting Apparel headquarters goes net-zero with solar carports.

06 Solar Snapshot

2 0 1 3

Colo., provided this photo of their monitoring system,

24 The Pressure To Perform Robust monitoring proves the efficacy of systems to consumers.

which we placed on an

28 Panels Pass The Test New test instrumentation verifies module quality and

mobile.

iPad to show how solar monitoring has gone

system performance.

32 How To Harvest The Sun

Farmers improve their viability by planting a

photovoltaic future.

38 Don’t Short Change Storage

The right battery can mean the difference between

68

Ad Index

success and failure.

42 The Rise Of Organic PV

Organic photovoltaics satisfy building functionality

and aesthetics.

46 Buy vs. Lease

Selection of financial models affects diffusion of solar in

residential markets.

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[S O LAR

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Sources: Information on this page was contributed from the Solar Energy Industries Association (SEIA) and GTM Research’s U.S. Solar Market Insight: Year-in-Review 2012 report, as well as from Ecotech Institute.

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“Solar Snapshot” provide a glimpse of the solar industry in pictures. If you have an infographic you’d like to see on this page, email it to Editorial Director Frank Andorka at fandorka@solarpowerworldonline.com.

www.solarpowerworldonline.com

4/22/13 1:19 PM

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[FUTURE OF FINANCE]

How Utilities Can Effectively Integrate Into The Solar Market As the U.S. solar energy market has developed,

Robert Sternthal

president of Reznick Capital Markets Securities

many utilities and IPPs are waking up to a new reality — their customers want solar. That means utilities need to figure out their role in this sector or risk losing their customers for 50 to 90% of their energy needs.

So how does a utility look at the U.S. solar market? What are the considerations for entering into the market as an owner as opposed to a provider? What part of the market should utilities be looking at — large-scale, distributed generation or residential?

Given the nature of today’s solar market, let’s ignore large-scale projects and save that discussion for another day because large-scale projects are going to require large tax-credit appetites. Few utilities have them, so they will need to find a way to secure it.

For the distributed generation and residential solar markets, the utility companies must decide between two things:

2. What does the platform look like? a. Where does it sit

geographically? b. What is the corporate make-up? c. How do you create all of

the documentation needed

to establish new customers and

process credit applications (for buyers

and internal credit committees)? d. How does it fit into the corporate organization?

3. How do you brand this new platform to gain marketshare? You are entering a fragmented but well-established market.

4. How do you manage systems once you own them? Who does the O&M? Now, let’s consider purchasing a platform. Here are the major considerations in such a scenario.

Naturally, some of these are also critical to growing a business organically.

• Buying a platform; or • Creating a platform through organic growth.

1.

For most of them, No. 2 is not an option. Why not? Here are a just few considerations if you are trying to create the business from scratch:

2.

3.

1.

You must hire employees. a. Who do you hire? There are few

people with the required experience. b. How many employees do you need? c. What is the cost of these employees? d. Do you put these employees

into the utility, or can they stay

as a separate unit?

4.

5.

Who do you buy? How do they fit into your corporate culture? Can you maintain their business as a separate entity?

What companies have actually executed the development of more than 25 MW and hold decent market share?

Are you looking for a nationally or locally successful company?

How much money are you willing to spend for a platform? a. Most developers and their

owners tend to overvalue

pipelines and portfolios of solar

assets, so are you willing to

overpay to gain a foothold into

the business?

How will you integrate the business into yours?

Robert Sternthal is president of Reznick Capital Markets Securities and has extensive experience in financing renewable energy transactions, whether they are in the wind, solar or biomass sectors. Working alongside CohnReznick LLP and CohnReznick Think Energy, Reznick Capital Markets Securities offers one of the most comprehensive financial advisory platforms in the industry.

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[FUTURE OF FINANCE]

6. How do they currently finance their projects? How efficient are they in securing financing for their projects?

Will you need them to continue securing tax equity, or can you provide the tax capacity needed?

7. How have they succeeded in the market to date? Can they continue in the same manner, or did their prior success depend upon unique factors – e.g., operating in markets with high SRECs? Both of these options are starting to seem rather intensive, aren’t they? So let me make another suggestion: If you are a major utility or IPP, why buy the business in the first place? If what you want are solar assets, then it would be easier to provide a pool of capital to

many of the established players, create a box that defines specific criteria and let them go out and source the deals for you.

This is already being done by several large players, although we could probably argue as to whether they are models of success or failure.

Yet I continue to believe that with the right guidance and oversight, creating a financing vehicle for ownership significantly reduces headaches in creating an entire platform and provides many of these players with the greatest probability of successfully growing ownership at a rapid pace. SPW

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[MARKETING]

3 Easy Ways to Improve Your Solar Conference Booth

Carter Lavin

Lavin is The Solar Marketing Group’s Business Development Manager and helps renewable energy companies analyze the market, articulate their messages and connect with their targeted audiences to achieve their marketing and communications goals.

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To connect with clients and strengthen their brands, companies spend tens of thousands of dollars on booth space at solar industry trade shows. While the first and one of the most costly steps to a successful trade show experience is getting (and building) a booth, the investment will either be recouped or lost depending on what is done with that space. Although a booth requires a large upfront investment, it’s necessary to stand out in a crowded industry with creativity and attention to detail.

There are many ways to improve your presence at a trade show, and staying on top of them can be overwhelming. Thankfully, managing your presence at a trade show is a lot like baking a pie: hard to do a great job, but easy to do a pretty good one. Here are three easy (and affordable) tips that will help you maximize your solar conference presence.

Layout that invites people in: The purpose of the booth is to invite visitors in and engage with them. When you are designing the layout of your booth, consider how people will approach it and what they will see when they do. Keep sightlines clear, and avoid furniture or signage that blocks the booth entrance. Too often companies put a big table at the main entry point, thereby directing people to stand on the perimeter rather than inside the exhibit space. You paid for that space. Use it.

Handouts other than your brochure: Your brochure is great. You update it regularly, the graphics are interesting and the copy is punchy yet tells your story eloquently. But it’s a one-size-fitsall collateral solution. Some people will be happy to take a copy of your brochure and put it in their bag of goodies, but many won’t have the space or interest to take all that paper with them. Having company literature in a variety of forms, both digital and hard copy, allows visitors to absorb your information in the way that they prefer.

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Booth staffers that speak solar: You need backup. Your booth should always have at least one person there if it’s a 10’ x 10’ and, if it’s bigger, it should have at least two people. Bring as many people from your sales, marketing and technical teams as you can manage. Companies can have trouble keeping a team member at the booth, since higher-value opportunities will invariably pull them away, leaving your booth unattended. But that means missed opportunities of unknown potential value. Having someone whose sole responsibility is to staff the booth ensures no opportunities will be missed.

A lot of companies recognize this need, so they hire third-party brand ambassadors through the conference organizers. They get professionals who have staffed conferences for industries ranging from Hobby Shops to Gaming. Often the staffers’ responsibilities are to be charming, collect business cards and distribute literature — and they are excellent at that. While this is much better than not having someone always at your booth, it’s not a full solution.

Our industry is technical and filled with nuance.

Brand ambassadors who know the difference between a microinverter and an integrated microinverter, or a thin-film from a polycrystalline module, will be much more ready to engage your visitors about your company’s specific values and products, assess their needs and tee them up for further discussion with your team members.

These are just some of the strategies that will help you get more out of your booth investment.

So remember, to have a great booth plan ahead, be creative and be inviting. SPW

www.solarpowerworldonline.com

4/16/13 2:08 PM

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[TRAINING]

Climbing The Ladder To Safe Solar The U.S. solar industry has another record

Sylvia Minton

Minton is senior vice president for MAGE Solar and a member of the board of directors for MAGE Solar Academy. She’s also a member of the Renewable Energy and Energy Efficiency Advisory Committee (RE&EEAC) at the U.S. Department of Commerce.

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growth year under its belt (76% annual growth and 119,000 Americans employed). More than 300,000 PV installations power homes, businesses and communities nationwide.

This rapid expansion of solar has sparked debate among fire departments who want to understand the technology for the sake of safety. For example, we recently broke ground on a 1.1-MW solar project for a high school. Among the well-wishers was the local fire chief, who stressed that the department must be trained on the new technology. “We need to know how to keep everybody safe,” he said.

Pleas like his echo others from thousands of fire departments across the country that are simply trying to do their jobs. As our industry grows, we must close a serious information gap. We must work to debunk the myths surrounding solar energy and ensure that the men and women who keep us safe are well informed and trained on solar technology, best practices and avoiding injury.

But before training can begin, we need to understand how important qualified installations are to reducing bad wiring, faulty grounding and bonding that could cause a fire. Installers should take advantage of courses like “PV Grounding and Bonding,” to keep their NABCEP CECs and trade knowledge current. PV field inspectors (the codekeeping “Knights of the Jedi Order” as we dubbed them in our last column) must be fully aware of what a quality install that is 100% compliant with local code and the NEC looks like.

For example, correct, sufficient and weatherresistant signage and markings on all conduit, cables and junction boxes can save valuable time in an emergency (it could even save lives). Installers should ensure that “emergency preparedness” is part of any service-and-maintenance call for a residential or commercial system. Simple things, such as clearly visible contact information at the breaker box or inverter can make a huge difference, allowing first responders to call a PV expert for guidance.

Reducing the guesswork around a PV system, thereby saving time, is well worth the effort. An average roof with lightweight metal trusses, for example, takes about 20 minutes to succumb to heat and cave in.

5 • 2013

Home and business owners can also be proactive and inform the local fire department of their solar PV array, its layout and any specifics they can provide. Fire departments are usually more than happy to know because it allows them to be briefed and prepared in an emergency before ever reaching the premises.

Any PV training for firefighters should include a thorough overview of various solar technologies and provide solid insights into the fundamentals of the systems and applications. What are the differences, peculiarities and each technology’s typical “behavior” in a fire or other kind of emergency? Which components can be shut down and isolated? Where are the shock hazards and in which environments do they exist? What should be considered when dealing with a battery back-up system? How do you make the array safe for other arriving emergency personnel, or for the next morning?

A safe-behavior guide based on familiarity with best installation practices, and a thorough awareness of common dangers is a tremendous asset in growing a safe and sustainable industry.

SPW

MAGE Solar Academy launches its Solar PV and Fire Safety Class in May. For further details visit www.magesolaracademy.com or contact msa@ magesolar.com. The academy also offers an 8-hour “Grounding and Bonding” course and a “PV Field Inspector” seminar.

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4/16/13 2:11 PM

Big solar is circling.

They don’t smell blood...they smell money. It’s yours.

Big changes are happening in solar. Companies are consolidating faster than ever, and soon there won’t be business left for independent installers.

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An offering can only be made by a prospectus filed first with the Department of Law of the State of New York.

Such filing does not constitute approval by the Department of Law. © Solar Universe, Inc., 1152 Stealth St., Livermore, CA 94551.

Solar Universe 3-13.indd 13

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[CONTRACTORS C O R N E R ]

Strata Solar, Chapel Hill, N.C.

John Morrison COO of Strata Solar

When Strata Solar, based in Chapel Hill, N.C., began its solar industry journey four years ago, it focused on the residential and small-scale commercial market in the center of the state.

The company evolved as a leading builder of ground-mount utility-scale projects, with 50 full-time employees and 450 contract employees. They build projects all around the state, including some hard-hit rural areas that need the power — and the jobs.

“We want to become a large solar installation and construction company,” says John Morrison, COO of Strata. “Our goal is to make solar power mainstream, in North Carolina and throughout the country.”

Strata Solar builds modest-sized (5-MW AC) utility-scale projects throughout North Carolina and increasingly into the wider Southeast, Morrison says.

In 2012, there were 131 MW of utility-scale solar built in the state, and Strata counted for more than 70 MW of that.

Operating under North Carolina’s renewable energy portfolio, Strata and other solar companies have thrived, but the current legislature does not seem to be as supportive of solar as the previous was.

“I find that bewildering,” Morrison says. “During the economic downturn, we were adding jobs and

Strata Solar Vital Statistics

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putting displaced construction workers back to work.

I’m baffled by the fact that our current legislature doesn’t recognize the job creation the solar industry has done in the state.”

The solar farms Strata builds are often in rural areas of the state (see the Editor’s Note below), which have often been bypassed by economic development.

Morrison says these construction projects not only create jobs in these depressed areas, but also increase the tax base of the municipalities and counties where the farms are built.

“During construction, we will drop nearly $500,000 into the local economy in direct expenditures,” Morrison says. “We hire 80% of our crews from the local area, and the rest is spending on fuel, lodging and supplies.”

Morrison says he enjoys watching solar energy go mainstream after nearly 30 years in the clean energy business.

“I’m almost giddy,” he says. “It’s finally happening.

After decades of promise, it’s finally here.” SPW

For the full interview with John Morrison of Strata Solar, go to www.solarpowerworldonline.com/ contractors-corner to hear the podcast.

Employees: 50 in-house, 450 contractors (and rising) in the field MW Installed (2012): About 72 MW MW Installed Overall: 125 MW Founded: 2009 Website: www.stratasolar.com

5 • 2013

(Editor’s Note: To find out how Strata managed to complete one of their projects in a little less than three months, check out the Project Review in the March 2013 issue of Solar Power World or find it online at www. solarpowerworldonline.com.)

www.solarpowerworldonline.com

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IN VER TER INS IDE R

Don’t Be Fooled ............

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4/19/13 10:22 AM

Editor’s Note: With the proliferation of ACPV systems in the United States, installers today must know how to tell the difference between true AC modules and DC modules with fieldattached microinverters. As is often the case in the solar industry, the devil is in the details — so here’s a quick overview of the regulatory, testing and manufacturing distinctions that make a true AC module.

............. {

By Steve Wurmlinger

Learn how to identify true AC solar modules from the pretenders

and Terence Parker

AC modules are defined in the U.S. National Electric Code (NEC) as “a complete, environmentally protected unit consisting of solar cells, optics, inverter and other components, exclusive of tracker, designed to generate AC power when exposed to sunlight.”

The NEC Article 690 requires equipment such as AC modules to be listed for the application.

Manufacturers and authorities having jurisdiction (AHJ’s) typically rely on Nationally Recognized Testing Laboratories (NRTLs) for this evaluation and Listing/Certification. A true AC module will be Listed/Certified as an AC module by a Nationally Recognized Testing Laboratory (NRTL).

The evaluation and listing of the AC module requires the use of two UL standards, UL1741

and UL1703. UL1741 contains the requirements for the combination of the inverter with the PV module and also references some tests from UL1703 depending on the mounting arrangement of the microinverter to the PV module. The components that make up the AC module assembly may also be individually evaluated and listed to these standards or requirements from these standards combined with requirements from other appropriate UL standards. For example, the PV module is evaluated to UL1703 and the microinverter is evaluated to UL1741 (including IEEE1547 to be identified as utility interactive) along with some of the environmental requirements from UL1703. UL has also recently released an outline of investigation for the AC connectors that combine connector requirements

Photo by Dennis Schroeder / NREL

»

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from other UL connector standards with UL1703 environmental tests.

The SolarBridge Pantheon microinverter was evaluated and certified by Canadian Standards Association (CSA), a U.S. NRTL, to UL 1741 2nd Edition (including IEEE1547) as a component for use with listed AC modules.

Additionally, the SolarBridge Pantheon microinverter is tested to environmental protection requirements from UL 1703 such as: Humidity Freeze, 10 cycles (HF10), followed by wet insulation resistance and dielectric strengthThermal Cycle 200 (TC200), followed by wet insulation resistance and dielectric strength Sequential TC200 and HF10 followed by dielectric and Ground Continuity test.

Assembly of an AC module should be performed in a factory under follow-

up inspection control of the NRTL that performed the evaluation/listing. Factory assembly with dedicated quality control is critical to ACPV reliability and allows for the AC module to maintain UL1741 listing. This is a major advantage over field-assembled ACPV systems consisting of PV modules and separate microinverters installed underneath or non-listed assemblies as discussed later in this article.

AC Module Cables AC modules with factory-integrated SolarBridge microinverters include SolarBridge special-use AC cables evaluated to various parts of UL’s AC Connector Standards and UL 1703 for use in outdoor PV applications.

The AC Connectors are locking type, suitable for disconnection under load and

are designed to withstand extreme outdoor conditions. They will not deform at high temperatures that can be encountered in ACPV applications, can tolerate complete immersion in water without failure and will withstand UL-standard impact tests at temperatures as low as -35°C. The jacketed multiconductor AC cables used are XLPE designated as Tray CableExtended Run (“TC-ER”) type, outdoor rated and designed for wiring in free air and/or for management within standard AC wiring components such as exterior wire tray.

Clips are provided for neat and secure cable management using the AC module frame.

ACPV Systems AC modules are connected together to form an ACPV system, and if the ACPV system is constructed using listed AC modules evaluated

Nordic’s Solar Solutions for Underground Electrical Distribution Fiberglass Sectionalizing Cabinets ● Sectionalizing/Junction cabinets are the solution for housing a ●

variety of 2, 3, or 4-point, 15, 25, or 35kV 200-600Amp load or deadbreak junctions with U-straps.

The exterior is covered with Munsell green gel-coat, which contains UV stabilizer and provides superior weather-ability and resistance to ultraviolet attack.

●

Sectionalizing Cabinets

PHH Series Hand Holes for Fiber Optic or Secondary Cables ● Penta-head bolt security and some models offering pad-locking provisions.

● Flush mount to grade, partially or fully buried.

Meter Pedestals ● Install up to 3 meter enclosures

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PHH Series Hand Holes

on the outside of the MPP-141480-MG

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27 POWER Warren,WORLD MN 56762 Tel: 218-745-5095 Fax: 218-745-4990 www.nordicfiberglass.com 1P.O. 8 Box SOLAR

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I NV E RT E R I NS I DE R

for the application, installers can look to Section 690.6 of the U.S. NEC for installation requirements. There are other installation designs, however, that can be called ACPV systems. These include designs where the microinverter is installed near the PV module (a “detached” microinverter) or, in some cases, bolted to the frame of the PV module at an assembly location off-site, or on-site just before installation (non-listed).

Section 690.6 (A) states “the requirements of Article 690 pertaining to PV source circuits (i.e. DC circuits) shall not apply to AC modules.” However, installers must follow all guidance provided throughout Article 690 when installing ACPV systems using detached microinverters or non-listed assemblies where the microinverter is bolted onto the PV module frame on-site or at some facility unassociated with the PV module manufacturer. This means that the installer will need to consider requirements such as: DC ground fault detection and interrupt, DC cable management, DC disconnecting means and DC grounding as well as the AC equipment grounding conductor to the inverter.

works closely with the module manufacturers to assure product safety requirements are met, the AC module is listed and the microinverter is paired correctly with the module (ratings and mounting). This includes evaluations to assure the PV module will pass rated loads after the inverter is attached. Improper mounting could impact the PV module rails or result in damage to the PV module back sheet material.

If the assembly is not evaluated and listed by a NRTL or constructed outside the PV-module factory, installers could be liable for installing unwarranted products that may not be safe and/or may not qualify for state or federal rebate/incentive programs. Installers and inspectors should always check the manufacturer’s product documentation and look for the AC module label on the back of the unit. SPW Steve Wurmlinger is senior regulatory engineer at SolarBridge Technologies.

Terence Parker is an applications engineering manager at SolarBridge Technologies.

Not Quite AC Modules Installers should be especially cautious with AC modules without any certification markings to support the assembled product.

Look for the NRTL Listing or Certification mark along with identification that it is an AC module evaluated to UL1741. The markings will include AC ratings and the term “utility interactive,” which identifies compliance to IEEE1547. AC modules will have at least one ratings/nameplate label with the AC module NRTL mark and AC ratings, but also may be provided with the DC PV module listing label and ratings.

PV modules that have inverters attached without an AC module evaluation by a NRTL may violate the original listing of the PV module and even void the warranty of the module.

AC modules powered by SolarBridge microinverters are covered by one warranty from the module manufacturer. SolarBridge

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2 More companies are choosing to tap sun power that was once wasted blacktop, making solar carports one of the fastest growing trends in the photovoltaic market. In this by-the-numbers diagram, engineers from Schletter, a manufacturer of solar mounting systems and other metal products, help us understand the essential components of solar carport systems. This particular system is the company’s B3 two-row arrangement. Read about a Schletter installation on page 22.

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Parking Lot

Power Up

5

Solar Carports By The Numbers

Foundation A concrete foundation is typical for solar carports.

Whether cast-inplace or drilled piers, concrete provides a secure foundation. Castin-place concrete is commonly used while pillars, which require less excavation, can be used for residential applications.

Micropile technology, which is gaining traction in the industry, makes for a faster installation, uses less concrete and is less of a hindrance to existing parking lots. Micropiles are especially useful for sites with restricted access or environmental sensitivity. Concrete can also be used above ground as a protective guard against cars that could damage the major support structure of the carport. An aboveground pedestal is built to be non-obtrusive to vehicles.

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Major Vertical Support Struts The major vertical support struts attach to the foundation and run upward toward the girders.

Two variables can affect the cost and longevity of the carport in regard to these struts: material and design. Major support structures made of aluminum with a mill finish require no maintenance and can exceed a 50year lifespan. They also weigh less, making them easier to install. Steel support structures must be powder-coated or painted. The weight of long cantilever steel beams may require heavy machinery and larger foundations.

Innovative designs, such as a W-shape support strut that was used in Sunlight Electric’s VF Corporation carport (see following page), allow for longer girder spans – exceeding 40 feet. Longer spans decrease the number of foundations needed, which can dramatically affect overall system cost. The design can also accommodate heights to allow full-size truck parking.

Girder

Purlin Rails

Clamps

Girders are the major lateral support and attach to the vertical support struts. In solar carports, rails are attached to the girders. The girder and support struts come in multiple sizes to accommodate various load regions and PV size requirements. When longer spans can be achieved, overall material costs and installation times are decreased, which reduces cost.

Solar carports include rails, which attach to the girder and are used to hold modules in place in either landscape or portrait orientation.

Wind load, snow load, tilt angle and the number of modules all impact the span that can be achieved.

Depending on load conditions, rails can span up to 27 feet for aluminum and up to 18 feet for typical steel structures. Longer spans translate to fewer support structures, which can reduce the overall cost of the system. To maximize usage area, rail lengths are typically designed in increments of 9 feet, the standard parking space width.

Module mounting clamps are a key component to fast installations. Unlike traditional groundmount and roofmount PV installations where there may be easy access to modules, installers of solar carports face limited module access.

Both the height of the carport and lack of a solid surface to work on mean installers must work on latters or other equipment.

This can increase the cost of labor and installation times. The easier a clamp is to work with, the less time installers will have to spend off of the ground installing modules. Choosing a clamp with integrated grounding can also help decrease costs by eliminating the need for additional work and material to ground the system.

Schletter’s Rapid2+ Module Clamp, which is ETL-certified, is a good example of a pre-assembled clamp that is easy to install and eliminates intricate wiring.

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Aluminum Outfitting Apparel headquarters goes net-zero with solar carports Steven Bushong/ A s s i sta nt Ed i to r

In 2011, clothier VF Corp. started construction on an eco-friendly headquarters for its outdoorsy JanSport, The North Face and lucy brands. Plans for the Alameda, Calif., office included a photovoltaic awning system to provide 8% of the site’s energy needs. “This campus will epitomize the brands’ outdoor ethos,” said Steve Rendle, VF’s vice president.

But after taking a look at the numbers, the VF’s sustainability group decided 8% just wasn’t good enough. After all, one of the brands, The North Face, recently began issuing public << Schletter’s Park@Sol solar carport comes in three primary design options. B1 is a single-row system for parking that runs east-to-west. B2 accommodates two rows of cars parked nose to nose. B3 is similar to B2, but its V-style roof structure allows the system to be more productive when the parking lot is running in a north-to-south orientation. It catches the sun as it’s rising and setting. Additional options include undersheeting waterproofing, understructure lighting and wire-management systems.

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sustainability reports. The group contacted San Francisco solar design firm Sunlight Electric and said they’d like to go all the way. They wanted a net-zero electricity building, and they had four roofs and a parking lot to make it happen.

They had some reservations about solar carports, though, explains Rob Erlichman, Sunlight Electric’s founder and president. They couldn’t lose parking spaces and, as a fashion headquarters, they didn’t want the system to be unattractive. “We started with a more conventional cold-rolled, box-steel, post-andbeam structure,” Erlichman says. “They asked us if there was anything that looked less industrial.”

Sunlight Electric turned to Schletter, a manufacturer of solar mounting systems and other metal products. The company makes the majority of its various carport systems from aluminum, as opposed to more-popular steel, says Justin Smith, a regional manager with the company. He says the lighter-weight metal makes installation easier.

“Steel allows larger spans, so you could do canopy structures with more than two rows of

www.solarpowerworldonline.com

4/19/13 8:52 AM

VF Corp. Solar: Total System Size: 856 kW

System Inverters: 12 to

Carport System Size: 600 kW

24-kW Refusol string inverters

PARKING LOT Carport

Design: Sunlight Electric

Structure: Schletter Park@Solar

Installer: Shamrock Renewable

BUILDING Rooftop Mounting:

Energy Services

Genmounts

Crew size: Variable from 6 to 26

System Panels:

Commission Date:

3,720 Hyundai 230W

December 2012

parking, but then you have to deal with the additional weight,” Smith says, adding that clients have told him aluminum is more aesthetic, too. It allows a carport architecture unlike others on the market, he says.

The 160,000-sq.-ft. VF building is located on land that was once the Naval Air Station Alameda, which closed in 1997. The area was a wetland until it was filled to make the airport in 1927.

These were important historical considerations for the design engineers. Typically, carports are built on pier footings, and this particular soil couldn’t support such a system.

To build a base, Sunlight Electric had a choice: Tear up the brand new parking lot to pour 13-feet-wide by 3-feet-deep concrete slabs or use helical screws, which drill into the ground 30 feet and are then surrounded by concrete. Sunlight took the latter option, and then poured concrete pedestals to serve as a mount for the carport. The pedestals also protect against wreckless drivers.

Other considerations included the traffic patterns at VF and municipality guidelines for emergency vehicle access. The structures were shifted so delivery trucks could make turns and avoid hitting the structures. “It’s important to figure that out on the front end, rather than having damaged structures later,” Smith says.

In the end, VF achieved net-zero status and forfeited zero parking spaces. The solar carports carry 70% of the building’s energy generation burden, proving to be the crux of the system.

Although these carports are in addition to a 256-kW rooftop array — and six vertical axis wind turbines that provide a sliver of energy — Smith says carports are often a simpler alternative to roof structures, which require structural analysis.

“Sometimes we’ll deal with customers, and their rooftop will be very complex,” he says. “You’ll start to see the dollar signs adding up in just the preliminary design. They may have a perfect parking lot, and we’ll go through the conversation, ‘Why not put your panels out there?’”

There are other benefits for a system owner, too. A carport offers shelter from the elements for employees and their vehicles. It is an obvious signal of environmental awareness. And — a fact that won’t be ignored by cost-conscious consumers – Schletter’s aluminum carports retain value. Owners can expect to cash-in at a recycling plant one day. SPW www.solarpowerworldonline.com

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S TAT E O F M O NITORING

As solar becomes more widely adopted, robust monitoring systems allow installers to prove the efficacy of systems to consumer s

The Pressure To

Perform W

By Frank Andorka • Editorial Director

hen the solar industry consisted of a sprinkling of residential sites in California, monitoring them didn’t seem essential.

Inverter manufacturers embedded systems to audit the performance of their products, but thanks to limitations in technology, the information wasn’t instantaneous. Additionally, most users were homeowners, who had neither the time nor the expertise to evaluate the data.

Since then, the solar industry has become the second-fastest growing energy source in the United States. It achieved 76% growth in 2012, according to GTM Research and the Solar Energy Industries Association (SEIA). These days, monitoring a system’s performance is quickly becoming less of an add-on, and more of a requirement.

The instantaneous transfer of information has radically changed the way the solar industry functions. After all, underperforming

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systems put the entire industry’s reputation at risk.

“A few years ago, most solar resources were owned and maintained by the end-user,” says Richard Duong, product engineer for Moxa Americas in Brea, Calif. “Now they’re being operated by companies who are owned by banks. Monitoring is absolutely critical in that scenario so companies and investors can make sure they are remaining profitable.”

Data Dump Until recently, most monitoring applications were designed to capture data from various solar-power-system components at regular, fixed intervals, Duong says. Then the information would be delivered, downloaded on a computer and set aside for analysis at a later time.

“That’s kind of the way it went when

we first entered the market,” Duong says. “People weren’t able to analyze the data immediately, and it became outdated quickly. What started as pure dataloggers are now becoming mini energy-management servers. No matter what computing platform you use, it has to be robust enough not to just gather information, but put it in context so people can use it.”

According to Adrian De Luca, VP of sales and marketing for Locus Energy, there are three types of monitoring systems in the market right now:

Inverter manufacturers typically sell inverter-based monitoring as an add-on. These are designed to provide basic transparency into inverter performance and generally

do not have robust fleet-management tools. In other words, the hardware and software are designed to highlight individual PV system generation data, but are not ideal for managing larger groups of systems.

are developed by solar-service providers and are only offered as part of a thirdparty ownership agreement. SolarCity and SunEdison are good examples. As two of the first providers of third-party owned solar systems, both companies created their own monitoring platforms because there were few off-the-shelf monitoring solutions available as they launched.

Generally, proprietary systems are fullfeatured, but are not available outside of their lease/PPA agreements.

• Proprietary monitoring systems

•

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STATE OF MONITORING

•

Independent monitoring systems are provided by companies that market solutions independent of OEMs and financing groups. These are typically the most full-featured platforms because the vendors focus all of their resources on building the best monitoring hardware and software. These solutions include a broad range of O&M tools for solar fleet operators as well as customized interfaces for end-users.

Real-time monitoring has value even before a project is commissioned, says Robert Schaefer, president and CEO of Also Energy in Boulder, Colo. Computer models allow the engineering, procurement and construction companies (EPCs) to test the arrays before they are commissioned. After they’re put into service, operations-and-maintenance (O&M) companies can monitor the sites to make sure they continue to perform at promised levels.

It would be easy to get overwhelmed by the amount of information today’s monitoring systems provide, but Schaefer says today’s systems also have alert protocols that pare it to the essentials.

“At some point, you need to rely on a robust alert system to let you know when something has gone wrong on your site,” Schaefer says.

“No one can monitor 1,000 sites. It’s just too much. If you can get specific alerts only when there’s something going wrong with the site, it becomes far more manageable.”

Make The Investment Locus Energy’s De Luca argues the people monitoring systems have changed over the years. No longer is the actual end-user getting dayto-day information about how their system is performing.

“In today’s market, people are not purchasing hard goods,” De Luca says. “They’re buying a service, so they no longer have a dayto-day vested interest in their system’s performance. That’s one of the things they pay their service providers to do. It’s the integrators, installers and O&M companies who are monitoring the systems to make sure they’re delivering the amount of power dictated in the agreement.”

De Luca refers to leasing companies like SunCity, Sunrun, Constellation Energy and One Roof as fleet managers. They have thousands of systems to track, and that’s how they make money. If fleet managers don’t monitor these systems, they risk rapid financial failure.

“For the end-user, monitoring is both a means of confirming that his solar-service provider is delivering power within the guidelines of the contract and a platform to demonstrate to friends and family the benefits of going solar,” De Luca says. “This last point can’t be overlooked. The cost of customer acquisition is high, making word of mouth and customer referrals key lead generators for service providers.”

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S TAT E O F M O N I TO R I N G

Monitoring provides such detailed information that it could potentially increase projects’ bankability, Also Energy’s Schaefer says. After all, you can’t manage what you don’t measure, and monitoring gives investors an increased sense of security because they can see their investments working.

“Financiers and operations-and-maintenance companies want to evaluate their systems, wherever they are, and make sure they’re performing as promised,” Schaefer says. “They can’t afford to have underperforming projects because they have committed to producing certain levels of electricity. Failure to produce those levels could be financially catastrophic.”

Protecting The Industry Moxa’s Duong says one of the biggest issues facing monitoring manufacturers is how to secure the data during transmission.

“As solar arrays become more popular inside communities, the power grid is going to need to control the inverters,” Duong says. “Once you open up these inverters to external control, the networks must be safe and secure. Think of it this way: We all have our bank accounts online, and that’s considered one of the most secure things around. The solar industry is moving toward more secure information while still allowing the critical analysis by the companies to happen.”

And whether the solar industry likes it or not, it is under intense scrutiny by solar-power skeptics, so monitoring and managing solar projects effectively becomes critical.

“Investors are making this industry go forward by putting up the money for these projects,” Also Energy’s Schaeffer says. “The last thing you want to do is give an investor a bad experience because solar is competing with every other investment opportunity in the world. We can’t afford not to deliver.” SPW

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M ODULE TE S TING

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Panels Pass The Test New solar PV test instrumentation verifies module quality and system performance

Ian Watson • C o n t r i b u t o r

C

omet Solar is an established solar installation company based in the British Overseas Territory of Anguilla. With some of the best beaches in the world, the local economy is largely focused on tourism. Comet has been successful in encouraging local hotels, resorts, property owners and businesses to invest in solar installations to offset the

effects of the economic downturn and rising energy costs.

“Cost is critical to our customers, so we tend to look for PV modules at bargain prices,” says Chris Mason, owner of Comet Solar. “Without any subsidies or incentives and facing aggressive resistance from the utilities, solar has been a difficult sell. It is only because the cost of electricity is $0.43/kWh that we have any customers at all. At that rate, and if we had net-metering, our payback on solar PV systems would be about three years.”

Comet customers tend to focus on price and return on investment, with aesthetics often low on the list of purchasing factors. However, buying bargain-priced solar PV modules brings its own challenges. Second-hand or refurbished modules are often used,

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M ODULE TE S TING

but in some cases the history of the modules and the original manufacturer is not known.

A lack of formal installation standards or regulations presents issues for installers.

For example, operating in a Caribbean jurisdiction means that Comet is not specifically required to perform the same tests that as a British or U.S.-based installation company .

Despite this, Comet always applies and meets the existing standards of the U.S. NEC code and performs best practices of the industry in the interests of maintaining installation quality.

To achieve this goal, the company recently invested in a Seaward Solar PV150 solar-installation test kit, along with a 200R irradiance meter to carry out effective quality control and customer-reassurance testing on its products and installations.

The Seaward Solar PV150 is a dedicated multifunction PV electrical tester designed specifically for solar installation. It performs open-circuit voltage measurements (Voc), short-circuit current measurements (Isc), earth continuity, insulation resistance and operating current, using AC/DC current clamps.

With the push of a single button, the new combination tester carries out the required sequence of electrical tests in a safe and controlled manner, avoiding the risk of contact with exposed live DC conductors.

Results can be recorded and stored in the tester for subsequent USB downloading to a PC. “To ensure the quality of the products we sell to our customers, we feel it is important to carry out testing thoroughly and effectively,” Mason says. “We owned standard test instruments and DC clamp meters but found that these manual methods were prone to error and were not particularly practical in the field. There is also no efficient way to record the results. We therefore decided to find a portable but capable testing system that would document the performance of each module in a recordable way.”

Recently Comet was offered a container of 170-W used monocrystalline solar panels and

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installed them in a 12-kW commercial flat-roof system.

These PV units had been replaced on their original system due to yellowing of the backing, but they were otherwise in perfect electrical and mechanical condition.

As the modules were used, Comet tested every unit prior to installation to ensure the quality and safety of the modules and to prevent subsequent dismantling for any troubleshooting required.

Comet constructed an improvised test bench at the installation site and tested every module as it came out of its packing. All

“Using the PV150 system on an installation in front of the client gives a sense of security that the installers are professional and are doing the project properly.” testing was carried out during the middle of the day to make use of full sun. Every one of the 66 modules were tested individually and no issues were found, with all units performing as expected with little variation between the modules, without ground faults or open circuits.

Most importantly, the speed of the test system allowed Comet to perform full tests on each module without impeding the work of the installation crew.

The test data for each module was downloaded and given to the owner as a system spreadsheet to prove that testing had been carried out thoroughly to verify the module quality and confirm anticipated system performance.

Comet’s latest solar PV installation project

is much larger and so requires different testing. The company is currently installing 500kW of Canadian Solar 240-W modules, purchased directly from the manufacturer.

Comet won’t pretest every module because of the modules’ known quality, but it will test each string at the combiner before installing fuses.

Working to NEC requirements does not allow for easy testing of the installation as it would be with a typical British system. The wiring is always in conduit and the combiner circuits are hard-wired, so there is no easy way to test installed strings on larger systems.

For these larger projects, Comet will be using 1000V-rated test leads with alligator clips.

“Using the PV150 system on an installation in front of the client gives a sense of security that the installers are professional and are doing the project properly,” Mason says. We are seeing the emergence of some less-thanprofessional installers in the region who perform poorly crafted installations, test nothing and do not give the customer any comfort that the work is being done properly.”

“Documenting system performance at commissioning gives us a baseline against which to retest in the case of a complaint or problem, both with customers and manufacturers,” Mason says. “For this use alone, the test kit and reporting system is invaluable.” SPW

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PROJE CT RE V IE W

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arvest H Sun Sun The author and assistant head to a turbine inspection at a wind farm in the U.K.

ow to

arvestthe

Farmers improve their viability by planting a photovoltaic future

Steven Bushong, Assistant Editor

F

or all their trouble with the weather and other forces beyond control, farmers have become some of America’s scrappiest business people. They’re always looking for a means to be more profitable and save money for the inevitable bad year.

When something goes well at a farm down the street, it isn’t long before other farmers hear about it and adopt the practice for themselves. It’s no surprise that solar PV has taken off in the agricultural space, solar developers say. It just makes sense.

Castle Rock Vineyards, a table grape grower in Delano, Calif., effectively took its cooler-and-storage facility off the grid when it installed a 2-acre solar array adjacent to rows of grape vines.

Nearby Peter Rabbit Farms, a fourthgeneration vegetable grower, heard about the success and soon took bids from installers for its own array. REC Solar built the farm’s 358-kW system, which provides enough power to shave an estimated $80,000 off the farm’s annual

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utility bills.

“I’ve been in this industry for 12 years, and farmers have gone from skeptical of to confident in solar technology,” says Ryan Park, director of business development at REC Solar, which has more than 9,000 solar installations nationwide. “They know this stuff works.”

Peter Rabbit Farms joined a growing group of more than 300 California farmers and ranchers who use solar energy to reduce utility bills. Agriculture represents nearly 30% of California’s commercial solar capacity, according to PV Solar Report, and experts anticipate the sector will continue to gain strength. Similar installations are popping up in Vermont, and there is no mistaking why.

“Farmers generally have open land,” says Andrew Savage, director of communications and public affairs at AllEarth Renewables in Vermont. “They’re acutely aware of energy costs in terms of their business, and they’re looking for ways to be more viable. Frankly, if you’re not a business-minded farmer at this point,

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The Richmond-based Vermont Youth Conservation Corps will supply all of its electric needs and feed excess to local schools with these AllSun Trackers produced by AllEarth Renewables.

concept. He says a solar system in California that costs $70,000 after tax credits could produce $14,000 worth of electricity annually. Many systems break even around the five-year mark, although that’s dependent on many

“

you can invest in solar and get five times those returns, why wouldn’t you do that?

They’re realizing the benefit.”

The Land

“

you’re probably struggling for survival.”

Developers say the finances work particularly well on farms, which have good years and notoriously bad ones.

A drought may wreak havoc on a farm’s revenue for years. To insulate

Farmers and farm owners often lease

If you’re going to put a solar array on farmland, then every effort should be

made to do so in a way that the land can be easily reclaimed for agriculture.

themselves, farmers often put goodyear profits into bonds, which can give them 2.5 to 3% returns. But solar is a lucrative alternative more farmers are discovering. In effect, they can have bonds on the roof of their barns.

Park of REC Solar illustrated the

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variables. After that, it’s 10 to 20% returns from a safe investment that comes with tax benefits.

“They’re willing to put their money in a money market account. They’re putting it away in bonds and CDs,” Park says incredulously. “Oh my goodness: If

land. In places with vast agricultural space, land may go for as little as $35 an acre, AllEarth’s Savage says. A solar array, then, is a gainful alternative. “We’re certainly not advocating for the wholesale buying of land for solar, but more the mixed use of solar in agricultural

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communities,” he says.

The company’s AllSun Solar Tracker, a pole-mounted dual-axis tracker, rises among 130 acres of apple trees at Champlain Orchards in Shoreham, Vt. The farm picks, packs and processes 3 million pounds of apples annually. The entire operation is now 100% renewable in its electric use.

“As farmers and businessowners that value independence, we wanted to do something that better uses our local resources,” says Bill Suhr, who owns the orchard with his wife Andrea Scott.

“This solar allows us to do just that.”

The University of Massachusetts has built arrays like Champlain’s for study. Its systems are placed on marginal soils, centralized towers or sloping roof structures.

The research project has three goals: It examines the results of implementing ground-mounted solar technology on farmland while simultaneously producing a crop. It produces a power source to offset usage at the research farm. Finally, the project demonstrates how this type of PV can be implemented by a farm cost-effectively.

The Neighbors The town of Hatfield, Mass. — population 3,249 — has the highest number of solar installations per capita in the state. Among residents with panels is Bob Wagner, the senior policy and program advisor for American Farmland Trust, a national organization that helps protect farmland. The trust hasn’t taken an official stand on solar development, but Wagner has his own thoughts — and 30 panels on his roof.

“If you’re going to put a solar array on farmland, then every effort should be made to do so in a way that the land can be easily

reclaimed for agriculture,” he says.

“Therefore, the solar array becomes a temporary use of the land, for the production of power from the sun as opposed to food.”

His ideas were highlighted recently because Hatfield is embroiled in a solar development controversy. At issue is a 2.4-MW installation planned for a 35-acre farm. Nineteen houses have a view of the land, which is zoned agricultureresidential, and the neighbors aren’t happy. “This is a power plant, a major one,” Michael Pill, an attorney representing the neighbors, recently told the Daily Hampshire Gazette.

“It does not belong in a residential neighborhood.”

While the scale of the plant can be debated, the concerns of the residents have prompted the Hatfield Agricultural Advisory Commission, chaired by Wagner, to create guidelines for solar installations on farmland. They appear here, shortened for space: • To the extent possible, arrays should be placed on existing farm buildings.

• If a land-based array is considered, use non-cropland areas.

• Every effort should be made to avoid prime farmland soils.

• If prime soil is to be used, keep disturbances of the existing soil to a minimum.

The commission believes these guidelines will help farmers benefit from and contribute to the production of renewable energy, while reducing the long-term impact to irreplaceable soils. The commission understands that solar is a profitable prospect for farmers. From Wagner’s perspective, a carefully installed solar array — what amounts to a temporary crop — is a lot better than a residential development. “That 35

Farmland Solar: 6 Topics To Think About Ryan Park, director of business development at REC Solar, offers advice on issues surrounding solar installations on farmland.

Permitting: “Many times, farms have a permit to perform commercial duties, even if it’s zoned agricultural. One of the reasons we’ve been successful working with farmers who have operations is because they usually have some empty space near a commercial facility. We can use that empty space to put in a ground-mount system.”

Transmission: “One big misconception when you look at farmland and see big transmission lines overhead is that it’s a great place to put solar. In reality, it can be cost-prohibitive unless you have a large enough project to interconnect at that high of voltage.”

Farmers: “First and foremost, farmers appreciate face-to-face communication and good old-fashioned business. A handshake and a look in the eye mean a lot. You don’t want to show up to a farm in a full suit and a tie. They’re going to think you’re overpriced.”

Timing: “Farming is seasonal. During harvesting, farms are like a busy freeway of 18-wheelers coming in and out. From an installation perspective, when you’re going to do the work is critical, and a lot of times, especially in Arizona and the Coachella Valley, you’re dealing with extreme heat, too.”

Soiling: “There’s no doubt about it: You’re going to get production losses from dirt and dust accumulation on panels. The credibility of the industry depends on accurate production estimations.”

Financing: “Farmers usually do not go the route of the PPA. They like the idea of owning the system.

That works on the investor side, too. Investors want to see a host with investment-rated credit. Farmers may have a lot of different companies, but they’re not out on Moody’s getting rated credit.”

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Peter Rabbit Farms, a fourth-generation family-run farm that grows carrots, lettuce, table grapes and other vegetables, worked with REC Solar to install a 358-kW solar system that provides enough power to offset 40% of their energy use.

acres could easily be 20 new homes,” he says. “Then that farmland is gone forever.”

The Wires Nathan Charles joined Paradise Energy Solutions, a Pennsylvania-based solar installer, about a year ago. Since then, he’s designed more than 20 farmland solar arrays, including a recent installation at Ferrell Farms, a grain-andpoultry farm in Henderson, Md. The system will pay for itself in 5 years, with a return on investment of nearly 20%.

Rural areas and smaller farms can present interesting challenges for installers, Charles says. For instance, while there may be plenty of land to work with or a big rooftop on which to install – sometimes at the perfect pitch thanks to common barn design – the electrical infrastructure can be unusual, to say the least.

Farms have different requirements for power and, in a rush to get the crop, handy farmers have made-do. A history of home-spun electricity modifications may accumulate, and an old farm could be littered from chicken coop to corn crib with faulty wiring and code violations. Part 36

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of Charles’ job is to make the solar power play nicely with the utility lines.

“As much as we’re able to, we try to bring things up to code,” Charles says.

“Sometimes we just have to work around certain things, though, because it’s not feasible.”

Farms may also lie alongside transmission lines that have challenging characteristics. Three-phase service allows installers to transmit power more easily, but a lot of rural areas aren’t equipped with it. Charles was working on a large farm recently with a 480-V open delta line, which he says is unusual but not necessarily bad.

“Rural systems, in my experience, tend to have fewer engineering requirements,” Charles says. “They tend to have larger existing services. Although it might be unusual, it’s easier to work within the scope of that.”

accumulation when they run models for a system’s output.

“The reason we’re getting the momentum we are in the agricultural space is because there have been a lot of success stories early on,” REC Solar’s Ryan Park says. “Farmers were getting the production the solar companies estimated. If you’re overstating the system, word will get around.”

Charles sees a lot of soiling happening on overshot roofs, popular on farms for their ventilation characteristics.

Unfortunately, the exhaust from the barn works to bring dirt to a resting place on panels. The problem is less urgent with many ground-mount systems, he says, which may be farther away from farm activity.

Smart modeling and an occasional cleaning should allay concerns and give farmers something to talk about at future industry events, where REC Solar and others often set up shop, waiting for the next farmer to consider sun power.

Farmers are industrious people. They have shifted their crops toward organics, opening a new market. They have joined community-supported agricultural groups (CSAs), letting neighbors buy rights to a certain take from the land and eliminating the middle man – all for higher profits. They have even installed methane digesters to create energy from manure. Now, they’re harvesting the sun.

“I mean, heck, we call them solar farms,” Savage says. “It’s a very natural extension for them.” SPW

Discuss This and other Solar issues at www.engineeringexchange.com

The Dirt Farms are dusty places. Cows can kick up enough dirt to affect an array’s output, and the only thing at stake is the whole industry’s credibility. Developers say engineers must account for dust

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Don’t ShortChange Storage

Selecting the right battery for commercial solar projects can mean the difference between success and failure

B y M i c h a e l R . Ku l e s k y

Photo Courtesy of SunPower Corporation

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s renewable installations increase worldwide, so does the need for reliable cycling batteries for energy storage. Correctly designing a powerand-backup system and selecting the right storage batteries for renewable applications can significantly affect overall performance, efficiency and longevity.

Solar applications are characterized by deep discharge-and-recharge cycles intermixed with partial state-of-charge (PSOC) cycles. As such, the batteries for these applications should exhibit the following performance characteristics: • • • •

Long cycle life Cycling in state of discharge Low rate of self-discharge Large electrolyte reserve

Often other factors such as cost, space and maintenance are given higher priority, complicating the purchasing decision.

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I N S TA L L AT I O N P R A C T I C E S Battery Type Advantages

-High reliability Flooded Lead Acid -Long life

-Easily recyclable

-Long life Valve Regulated Lead Acid -Easy to get back online

-No need to water, reduced

maintenance

Tubular Lead-Antimony -Long cycle life

-Long life

-Low rate of self discharge

(up to 2 years or 2 VPC) Thin-Plate Pure Lead -Quick charge cycle with

advanced electronics

-No need to water, reduced

maintenance

-High energy density

-Can handle elevated

temperatures guidelines. When the project exceeds the budget, the easiest way to reduce costs is to seek savings from the largest ticket items (in this case the solar panels).

In a solar installation, however, the solar panels are the only power-generation source.

Installing too few or improperly sized panels can have a direct effect on the life, as well as the short- and long-term performance, of the system components — especially the batteries.

Without enough power generation in the system, the batteries become depleted. With no recharge period, they plateau and discharge again, creating a downward “stair-step” cycle pattern. Continuously discharging lead-acid batteries more than 80% causes irreversible harm. Therefore, the more cycles anticipated, the lower the depth of discharge (DOD) should be designed into the battery system. For maximum investment, it is best to not discharge the battery more than 40 to 50% in a diurnal system.

batteries that provide excellent reliability and maximum cycling capability.

Grid and Plate Design: In general, the batteries marketed to the solar industry are manufactured with either flat or tubular plates.

Flat-plate designs are the principal type used in stationary utility and switchgear applications throughout North America. They consist of a grid structure of negatively and positively charged plates made of alloyed lead (either lead calcium (PbCa) or lead antimony) or pure lead in an electrolyte. The flat-plate structure has proven to be a robust, flexible design in which the plate characteristics, such as thickness, metal alloys, wire radius and placement, can be adjusted to create application-specific batteries delivering optimum performance in terms of float service, cycle service, duration and high rate.

Tubular-positive plate designs are widely used in solar and other demanding applications in which maximum cycling is key.

The current carrying lead metal in tubular designs is entirely surrounded by active material. This keeps the active material tightly against the spine and helps to ensure long life.

Battery Chemistry And Design Batteries have evolved over the past few decades to meet the specific needs of utilities and other industries. Solar applications require 4 0 SOLAR POWER WORLD

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Limitations -Heavy -Requires watering/high maintenance -Prone to corrosion -Reduced life in high temperatures -Requires minimal watering -Heavy -High rate of self discharge -Poor energy density -Longer charge cycle -Cost -Not a cycling battery with standard float charge cycle

Tubular batteries have either round or square tubes. In general, square tubes provide most surface area on the positive plate, exposing more positive-plate active material to the electrolyte. The square tube construction also prevents active material from dislodging away from the grid — a common failure mode in flat-plate designs that can lead to early failure due to sediment shorts. This combination of greater positive surface area and better paste adhesion allows for excellent cycling capacity.

To Alloy Or Not To Alloy?

Over the years, manufacturers have experimented to find the right materials to produce the positive plates in traditional lead-acid batteries. By itself, pure lead provides excellent performance. However, it is also malleable and requires special handling during manufacturing to ensure that the plates, grids and elements maintain their integrity. To address these issues, manufacturers have tested various alloys.

Alloying lead with calcium greatly facilitates manufacturing but results in higher corrosion rates. Other materials like cadmium, antimony

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and selenium improve cycle life and facilitate manufacturing but cause various negative attributes, such as issues with recycling and increased float current that causes internal heat buildup and lowers efficiency. For this reason, use of these alloys is limited to applications such as solar systems, in which the demand for frequent charge-discharge cycles overrides the disadvantages.

Over the past 20 years, manufacturing equipment has also evolved so that thin-plate, pure lead (TPPL) batteries are a viable and available option. They are ideal for backup applications because they are a smaller, lighter solution with a longer shelf life, service life and a higher-rate of efficiency than traditional alloyed technologies. They also have a low gassing rate, which reduces water usage and maintenance costs. However, TPPL battery manufacturing requires a high capital investment and a wealth of knowledge to manufacture. Therefore, they are primarily marketed as a premium solution for challenging applications ranging from submarines to telecommunications systems.

Flooded vs. Valve Regulated Lead-acid batteries are available in two containers — flooded or valve regulated.

Flooded batteries require rewatering and so are costly to maintain. They also require larger containers for the flooded electrolyte, making them less energy dense. Also, flooded batteries allow for visual monitoring of the cells, enabling operators to identify issues and preventative maintenance needs more readily than sealed, valve-regulated lead-acid (VRLA) batteries.

On the other hand, VRLA batteries are lighter weight, require lower maintenance and are more cost-efficient. To accommodate for corrosion in PbCa batteries and to prolong life, manufacturers increase grid thickness at the cost of reduced energy density and increased weight.

Climate And Environmental Considerations Many solar farms are located in desert locations with high daytime temperatures and dramatically cooler evening temperatures.

Temperature extremes — especially high heat — can damage batteries. While it is important to protect batteries from the effects of external temperature variations, it is even more important to monitor the critical internal-core temperatures of the batteries.

TPPL batteries, with a recommended operating range of -40 to 122˚F, outperform most other batteries in extreme temperatures.

Tubular lead-antimony batteries, with a recommended operating range of 5 to 113˚F, are moderately tolerant of temperature variations. Lead-alloy batteries such as these, however, fail more quickly in an overcharge situation than TPPL batteries. For example, when a lead-alloy battery warms up, it draws more current, which generates more heat. This can produce a vicious cycle that causes the battery to reach a critical stage in a matter of hours. TPPL batteries exhibit a more gradual increase in temperature, taking longer for a battery to reach a critical stage in the event of a malfunction of thermal protection circuitry. This offers more time for the problems to be discovered and remedied before the battery fails.

Many designers overlook the opportunity to use the ambient cold to their advantage. A venting system can use the night air to cool the batteries, yielding more positive effects than negative ones, while temperatures get much hotter during the day.

In general, battery cells should be maintained in clean, cool and dry environments that are free from water and dirt. They should be positioned so that there are minimal temperature variations between the cells. For example, battery lines should not be located near HVAC ducts, exhausts, heating sources or direct sunlight. Temperature variation will cause irregular core temperatures among different cells and will cause imbalance in state of charge.

Adequate ventilation in the battery compartment is also important to prevent hydrogen accumulation from exceeding 2% of the total volume of the battery area.

Pockets of trapped hydrogen gas, such as near the ceiling, can be extremely dangerous because it is highly combustible. Monitoring is essential, especially at remote locations,

Installation Practices 5-13_FINAL_Vs3.indd 41

where batteries can go unattended for long periods. These concerns can become more exaggerated in climates where extreme temperatures can affect battery performance at least part of the time.

Maintenance Following the manufacturer’s guidelines for monthly, quarterly and annual maintenance will ensure long battery life and strong performance. In addition, here are several key areas on which to focus to reduce irreversible harm: • Charging (charger output, torturing bolts, dirty solar panels, etc.)

• Watering flooded batteries (a must for life and safety) • Voltage (low voltage cells will eventually cause harm to good cells) • Visual inspection for bulging, leaking, cracking, etc.

Conclusion While it may be tempting to cut budgetary corners when designing commercial solar systems, it can have catastrophic results down the road in terms of poor performance, shortened battery life, outages or even worse.

For this reason, it’s best to invest smartly from the beginning, recognizing the true needs of the system and choosing generation and backup products that are best suited for the rigors of the solar-farm environment. SPW Michael R. Kulesky is the director of commercial marketing for telecommunications, utility and new technologies at EnerSys.

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The Rise of Organic PV Engineers and architects increasingly turn to organic photovoltaics to satisfy building functionality and aesthetics

By J. Patrick Thompson

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rchitectural design is changing. Energy costs and social trends are making sustainable buildings more attractive and valuable for designers, developers and owners. Sustainable buildings can be more efficient for net-energy usage through conservation technologies such as insulation and low-emissivity windows. These conservation technologies can be used in combination with energy-generating technologies, such as solar PV. Sustainable building practices, taken to their ultimate potential, can create net-zero buildings that use electricity and other resources extremely efficiently. Net-zero buildings generate the electricity they need from their structures. This trend reflects the need to combine aesthetics with functionality to optimize overall building operations.

Current systems sometimes intrude on the aesthetics of a building and will require complementary technologies. Building engineers and architects are looking to solar engineers to increase their options.

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New Energy Principal Scientist Dr. Scott R. Hammond works with scientists at The National Renewable Energy Laboratory (NREL) on organic photovoltaic technology

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ENGINEERING DEVELOPMENTS New Energy Technologies’ SolarWindow Technology

Emergence of Organic Photovoltaics Engineers and architects are excited about using organic photovoltaics (OPV) for net-zero buildings because they allow for design flexibility and can provide additional functionality for fixtures and materials.

Rather than a standard p-n junction used in inorganic semiconductor modules, OPV uses a blend of an organic conjugated polymer and a fullerene to form what is commonly referred to as an active layer.

These compounds, composed primarily of carbon and hydrogen, act as an electron donor and an electron acceptor to provide electron mobility. With this system, a photon interacts with the active layer to produce an excited electron-hole pair called an exciton, which consists of the negative electron and 4 4 SOLAR POWER WORLD

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positive hole and delivers the electrons to an electron transport layer (ETL). At the same time, it delivers the holes to a hole-transport layer (HTL).

There is more than just exciton physics that differentiate OPV from conventional PV. OPV has attributes that can be tweaked to adhere to specific performance criteria. Predominantly, these attributes are light absorption, open-circuit voltage, good performance under indoor-lighting conditions, low-capital expenditure and potentially low-energy production costs using printable techniques and methods. By fine-tuning light absorption, it is possible to absorb wavelengths of specific light, which in turn affects color and visual light transmission (VLT). By balancing light absorption and VLT, with the ability to

specify the open circuit voltage (Voc), the electrical performance of the device can be optimized. Interconnecting cells in series and parallel strings allow voltage and current to build power (wattage) within an OPV solar module.

OPV does not need direct solar (i.e., natural sunlight) irradiation to produce electrical power. OPV devices can produce electrical energy when exposed to artificial and reflected light. An example of this can be observed in prototypes such as New Energy Technologies’ SolarWindow, which operates by using natural and artificial light sources to produce electricity. SolarWindow technology, which is still under development, uses OPV to maintain high levels of VLT to produce a see-through coating that can be applied to windows. Since the technology

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Another attribute of OPV is that the coating can be applied on flexible substrates. This makes possible many potential applications and uses in building systems, and it’s expected to contribute as an option for netzero buildings and provide other electricitygenerating options in the non-architectural space.

There are also manufacturing advantages to OPV applications. With OPV it is possible to apply these materials in a solution process. While there are many coating methods available for OPV, New Energy’s SolarWindow coating can be applied at ambient conditions that do not require high temperature, pressure or vacuum processes. This has the potential for low cost, high-speed manufacturing.

Conventional silicon and thin-film PV, on the other hand, typically requires high electrical energy and high temperature, pressure or vacuum deposition techniques.

OPV Contributions To Sustainability OPV is expected to be a good fit for buildingintegrated photovoltaics (BIPV) and net-zero building construction and renovations.

Since glass is a primary component of most building envelopes, architects and builders are already familiar with its uses and function. With OPV, it will be possible to add functionality to building components without compromising aesthetics. This increases the value of sustainable architecture and net-zero buildings, as well as the value of the building itself. It is expected that OPV can be an important addition to the growing list of available technologies used in sustainablebuilding design. Conventional solar PV arrays in tall commercial structures must compete for space with other roof structures such as access points, and electrical and mechanical systems. Power generation is a function of power density and available real estate (area

or space). If we consider redefining “real estate” to include the vertical surfaces of tall buildings, urban environments may have an entirely new dimension to its potential electrical generation.

As market demand evolves, new technologies must continue to evolve as well to address these and other net-zero building requirements. OPV, and other products being developed for eventual commercialization, show that innovative companies are prepared to meet the challenging sustainable energy and market demands with new solutions.

Whatever the future may bring, we can expect that there will be technologies developed to address current and future sustainability goals as we move toward an energy autonomous society. SPW J. Patrick Thompson is VP of business and technology development at New Energy Technologies.

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BUSINE S S IS S UE S

Buyvs.

Lease in Residential PV Markets Varun Rai and Benjamin Sigrin How the individual selection of financial models affects the diffusion of solar energy in residential PV markets 4 6 SOLAR POWER WORLD

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e

Acknowledgements Varun Rai is a professor at the LBJ School of Public Affairs and the Mechanical Engineering Department, and Benjamin Sigrin is a professor in the LBJ School of Public Affairs at The University of Texas at Austin. Rai would like to acknowledge support from the Elspeth Rostow Memorial Fellowship and from the Center for International Energy and Environmental Policy (CIEEP) at the University of Texas at Austin. Benjamin Sigrin would like to acknowledge support from the LBJ School of Public Affairs and the Energy & Earth Resources Program at UT Austin.

Errors are ours alone.

This article originally appeared in the Environmental Research Letters journal. All material in IOP’s Open Access journals is, unless stated otherwise, published under a Creative Commons Attribution licence (CC-BY).Open Access articles published in Hybrid journals are made available under the same conditions. We used a rich dataset from the burgeoning residential PV market in Texas to study the nature of the consumer’s decision-making process in the adoption of solar technologies. In particular, focusing on the financial metrics and the information decisionwww.solarpowerworldonline.com

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BUS INE S S IS S UE S makers use to base their decisions, we study how the leasing and buying models affect individual choices and the adoption of capital-intensive energy technologies. Overall, our findings suggest that the leasing model more effectively addresses consumers’ informational requirements and, contrary to other studies, that buyers and lessees of PV do not necessarily differ significantly along socio-demographic variables. Instead, we find that the leasing model has opened up the residential PV market to a new, and potentially large, consumer segment — those with a tight cash flow.

Introduction Two questions prompted the work in this paper.

First, what can be learned from the diffusion of solar photovoltaics for improving existing solar programs and the design of others in newer markets? As policy support for these technologies is waning, this increases the pressure for incentive programs to become more efficient (U.S. DOE 2012; U.S. DOE 2008). Second, what lessons

can the residential PV market shed on the individual decision-making process? The scale of capital investment for solar PV is quite high relative to most other household investments. So presumably, the choice to adopt PV forces individuals to consider the (alternative) options more carefully than most investment decisions (Jager 2006).

Unpacking the decision to adopt PV, then, might provide insights into the nature of individual decision-making.

Understanding the nature of the decision-making has important practical implications for the design of mechanisms that encourage reduction of greenhouse gas (GHG) emissions from energy use. With 22.2% consumption of primary energy and 21.4% of the total GHG emissions (EIA 2010), the residential sector is a key target for reducing energy demand and GHG emissions.

Diffusion of microgeneration technologies, particularly rooftop PV, represents a key option in meeting demand and emissions reductions in the residential sector (U.S. DOE 2012). As different actors have tried to design programs and incentives to spread the adoption of more efficient and environmentally-friendly consumption and

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generation devices (Taylor 2008), the nature of the individual’s decision-making process has come to sharper focus (Allcott & Mullainathan 2010; Dietz 2010; Drury et al. 2011; Jager 2006; Keirstead 2007; Bollinger & Gillingham 2012). Therefore, the last few years of experience with residential PV provides an early opportunity to refine our understanding of how individual decision-making affects technology diffusion.

Three lines of theory are relevant to this work:

1 Decision-making at the individual level.

While the neoclassical microeconomic theory presumes that individual decision-makers are rational and information-prescient, there is increasing evidence that individual decision-makers depart significantly from the neoclassical model (Camerer et al. 2004; Frederick et al. 2002; Gintis 2000; Todd & Gigerenzer 2003; Wilson & Dowlatabadi 2007).

2 Empirical evidence of the use of high discount rates for future returns from energy-saving technologies (Gately 1980; Hausman 1979; Meier & Whittier 1983; Ruderman et al. 1987). Expectations of rapid technological change, information barriers and other non-monetary costs are some of the factors that give rise to the use of high implicit discount rates (Hassett & Metcalf 1993; Howarth & Sanstad 1995). In general, this phenomenon discourages the adoption of technologies whose benefits are spread over a long time horizon. The use of upfront capital subsidies have been proposed as a way to overcome this adoption barrier (Guidolin & Mortarino 2009; Hart 2010; Jager 2006; Johnson et al. 2011; Timilsina et al. 2011;).

3 Business models for accelerating the deployment of technologies by addressing market barriers (Gallagher & Muehlegger 2011; Margolis & Zuboy 2006; Sidiras & Koukios 2004) facing individual decisionmakers,in particular the leasing model.

Several researchers suggest that the option to lease a technology effectively addresses the high discount-rate problem (Coughlin &

Cory 2009; Drury et al. 2011), as well as some of the information failures associated with new technologies (Faiers & Neame 2006; Shih & Chou 2011).

Data Our analysis uses a new household-level dataset built through two complementary data streams: (i) a survey of residents who have adopted PV and (ii) program data for the same adopters obtained from utilities that administer PV rebate programs. The survey, among other factors, explores why PV adopters made the financial choices they did (say, buy vs. lease), and their own assessment of the attractiveness of their investment (Rai and McAndrews 2012). The survey was administered electronically in Texas during August-November 2011 and received 365 responses from the 922 PV owners contacted.

All survey respondents reported residing in areas of retail electricity choice in Texas (see Supplementary Information for spatial distribution).

The mean size of the PV system installed was 5.85 kW-DC and the average age of respondents was 52 years old. The mean household income was between $85,000 and $149,999 and 84.9% reported that at least one member of the household had achieved a college degree or higher level of education. Each of the prior demographics is significantly different from state-wide averages. That is, the survey population was wealthier, older and better-educated than the average Texas resident. No significant difference was found between lessees and buyers of PV on any demographic variable.

Of the 365 responses, we matched complementary program data for 210 respondents. The program data provides several data points, including (i) installed cost of the system, (ii) price and structure of lease payments if the system was leased, (iii) system capacity (kW, DC and AC), (iv) amount of rebates disbursed, (v) aggregate household electricity consumption from the prior year, (vi) retail electricity provider (REP), electric plan, and marginal cost of electricity consumption just prior to PV installation, and (vii) projected annual electricity generated by the system based on orientation, derating factor and geography.

Methodology Our strategy is to compare the financial metrics that PV adopters used to evaluate their investment decision (reported metrics) obtained through survey (above) with an “objective” assessment of those same metrics (modeled metrics). To enable the comparison, we built a financial model that calculates the expected lifecycle costs and revenues of PV system ownership for the residential buying and leasing business models (NREL 2009; Kollins et al. 2010). Our model is distinct in two ways. First, our unusually comprehensive dataset allows detailed cost and revenue calculations for each respondent (decision-maker). Second, it includes detailed features of household-level electricity consumption, electricity rates, and PV-based electricity generation, including time-of-day and monthly variations. Next, we provide an overview of our methodology.

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BUS I NE S S I SS U E S

Cash-Flow Model 3.1 For each PV adopter we calculate a series of monthly-expected costs (Ck) and revenues (Rk) accrued over the lifetime of the PV system, where k is the number of months since the PV system was installed. Therefore, cash flows (CFk) of the investment are: CFk = Rk - Ck

Using these cash flows we calculate the net present value (NPV) using a 10% annual discount rate, NPV per DC-kW, payback period for each household’s investment, and estimate each individual’s implicit discount rate.

System Costs 3.2 Costs (Ck) have three monthly components: (a) system payments (Csystemk) — either lease payments or loan payments when financed and a down payment as appropriate, (b) operations and maintenance costs (CO&Mk), and (c) cost of inverter replacement (CInverterk) where: Ck= Csystemk+CO&Mk+CInverter k System payments for buyers comprise a down payment in the first period and loan payments if the system was financed. The net system cost is the installed cost less the utility rebate reported in the program data less applicable federal tax credits. We assume that: (i) buyers will make periodic operation and maintenancerelated (O&M) expenses equivalent to 0 to 0.75%/year-1 of the system’s installed cost; these O&M costs are expensed equally each month, and (ii) inverters require replacement after 15 years of use and cost $0.70 to 0.95 per DC-Watt. In Section 3.4 we present a set of scenarios that systematically vary these parameters.

Lessees are not obligated to pay O&M or inverter replacement costs as this is a value-added service provided by the lessor (Mont 2004). Therefore, the only costs of ownership incurred are lease payments (up-front payment and monthly lease payments). Within the sample, 69% of lessees paid for their lease entirely through a ‘pre-paid’ down payment, 26% through only monthly payments and 4% through a combination of monthly payments and a down payment. For all leased systems analyzed, we use the actual lease payments being made by the lessees.

3.3 System Revenue PV systems generate value by reducing owners’ electricity-bill expenses during the life of the system. Therefore, the difference between electric bills the owner would have incurred without the system (BAU bill) and those with the PV system (PV bill) is effectively a monthly stream of revenues (Rk). The value of these revenues depends on the structure and rates of both bills. Our model forecasts these revenues over the system’s lifetime.

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3.3.1 Electricity Consumption and Generation Profiles Two central factors in the PV value proposition are seasonal and hourly variations in the system’s generation and the household’s consumption of electricity. For both factors, we use each respondent’s historic annual consumption and expected annual system production (kWh) as reported in the program data, but not individual consumption or generation patterns. To simulate these hourly and seasonal variations we used load profiles published by the Electricity Reliability Council of Texas (ERCOT) of average residential consumption patterns in north-central Texas in 2010 (ERCOT 2010) and a PV generation profile for the Dallas-Ft. Worth area taken from the PVWATTS model created by the U.S. National Renewable Energy Laboratory (NREL 2011).

Furthermore, we assume that patterns and quantities of electricity consumption are invariant over the lifetime of the PV system.

This is not a robust assumption per se, since we do not capture household-level patterns of consumption that differ from the ERCOT profile or that evolve over time. But, since the goal is to compare the objective and reported financial metrics, this assumption is robust enough for our analysis because any variations in consumption profiles will largely cancel out in the revenue calculations.

3.3.2 Electricity Rates Within the ERCOT deregulated electricity market customers freely choose retail electricity service among providers with varying rates and bill structures (TECEP 2012). An important factor is whether their Retail Electricity Provider (REP) offers a plan that credits any moment-to-moment excesses of PV generation over consumption outflowed to the grid (Darghouth et al. 2011; Mills et al.

2008). Unlike many retail-choice states, the ERCOT market does not mandate that REPs provide credits for these ‘outflows’ (PUCT 2012). Current practice is for REPs to credit outflows at a rate below the marginal price of electricity.

While it is tempting to assume that consumers will select electricity plans which

offer the highest value for their PV system, it is not obvious what depth of information finding and analysis decision-makers go through to determine which REP provides this greatest value (Conlisk 1996; Fuchs & Arentsen 2002; Gigerenzer & Todd 1999; Goett et al. 2000; Roe et al. 2001; Tversky & Kahneman 1974).

We account for this dilemma through a set of scenarios, discussed next.

3.4 Scenarios To account for uncertainty in the model’s parameters (Bergmann et al. 2006; Laitner et al. 2003), calculations are structured as a series of five scenarios — Very Conservative, Conservative, Baseline, Optimistic and Very Optimistic (Table 1). Scenarios employ progressively more optimistic assumptions that increase the value of solar to the consumer. Parameters varied were: (i) the annual growth rate in nominal retail electricity price (0 to 5%) (ii) if bought, lifetime of the system (20 or 25 years) (iii) system loss rate (0.75 to 0.25%/yr-1) (iii) O&M costs as a percentage of installed costs incurred per year (0.5 to 0% yr-1), and (iv) inverter replacement cost ($0.95 W-1 to $0 W-1). Note that these scenarios are not intended to represent likely or unlikely outcomes, but to explore how consumers’ differing assumptions would affect their evaluation of PV’s value.

Scenarios also vary the customer’s retail

Results We present here the results of our analysis.

Framing this analysis are the differences between buying and leasing consumers.

Contrary to Drury et al. (2011), we found no statistically significant differences between the two groups on demographic factors including income, age, education and race, as well as contextual factors such as the size of their system, annual electricity consumed or electricity rates. Based on these results and those that follow, our conclusion is that at this stage in the diffusion of residential PV buyers and leasers do not represent different demographic groups, but rather different consumer segments within the residential PV market.

Table 1. Description of the scenarios Scenario Elec. Cost Growth System Life System Loss Rate Maintenance Costs Inv. Replace.

Cost Electricity Plan After PV Adoption

(1) V. Conservative

(2) Conservative

(3) Baseline

(4) Optimistic

(5) V. Optimistic

0.0%/yr

2.6%/yr

2.6%/yr

3.3%/yr

5.0%/yr

20 yrs

20 yrs

25 yrs

25 yrs

25 yrs

0.75%/yr

0.5%/yr

0.5%/yr

0.5%/yr

0.25%/yr

0.5% /yr

0.25%

0.25%/yr

0.15%/yr

0%/yr

$0.95/W

$0.95/W

$0.7/W

$0.7/W

None

Keeps same REP and plan postinstallation; no outflows

Adopts solar plan if offered by current REP

Adopts solar plan if offered by current REP; min.

7.5¢/kWh outflow

Adopts plan with max. value among current market solar plans or BAU plan

Same as Scenario 4

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electricity plan post-installation. The most conservative scenario (Scenario 1) assumes that consumers remain on their pre-PV plan for the lifetime of the system, whereas the most optimistic scenario (Scenarios 4 and 5) assumes that the consumer actively researches and selects plans that minimize their electricity bill.

The baseline scenario (Scenario 3) assumes that consumers will adopt a ‘solar’ plan if offered by their REP, but will not transfer REPs. In addition, the consumer is credited 7.5 cents/ kWh-1 for outflows if their current REP does not offer a solar plan — since we believe that nearly all REPs will offer an outflow credit in the future. Indeed, most major REPs do so already.

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1

Distribution of modeled NPV per kW assuming baseline model parameters.

4.1 Installed Cost and Cost of Ownership Installed costs ($W-1) of leased systems (Mean = 8.3, Std. dev. = 0.53) were significantly more than those of bough systems (Mean = 6.2, Std. dev. = 1.4), and the mean differences were highly significant (t(201) = 16.08, p < 0.001). This corroborates similar installed cost differences for bought and leased systems nationally (Barbose et al. 2012). As discussed in Section 3.2, recall that while buyers’ cost of ownership is the installed cost less applicable rebates, the installed cost is generally not reflective of the lessees’ cost of ownership, which are only their lease payments.

Surprisingly, the mean lessees’ costs of ownership ($0.70 W-1) were substantially less than those of buyers ($2.64 W-1).1 Accordingly, we found that lessees had a statistically significant greater NPV per capacity ratio (NPV/DC-kW) than buyers in all but Scenario 5 (Figure 1; only baseline scenario shown).

How is it possible that leased systems are installed at higher costs than purchased systems, but that lessees face a lower cost of ownership than the equivalent bought system? As others have noted (for example see, Barbose et al. 2012), the installed cost reported to state and utility PV incentive programs is often the ‘fair market value’, or the appraised value, reported when applying for the 1603 Treasury Cash Grant or Federal ITC. Since the benefits of both the 1603 Treasury Cash Grant and tax benefits from MACRS increase with the appraised value of the system, it is plausible that some leasing companies might be inflating the appraised value — at least the incentive to do so clearly exists. Indeed the SEC and IRS recently began an investigation of several leading leasing firms to determine if the true fair market value of installed PV systems were materially lower than what the firms had historically claimed (SEC 2012). If proven true, one implication of this financial strategy would be that since additional system costs and company profits are recouped through the tax structure, leasing companies adopting such strategies would be able to offer lower rates 52

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to their customers (the lessees). The fact that we indeed find the cost of leasing PV systems (by the lessees) to be much lower than the cost of buying PV systems lends some support to the hypothesis that some leasing companies might be employing such financial strategies.

Therefore, we tentatively explain lower lessees’ costs of ownership through the following mechanisms: (i) maximization of federal tax benefits by leasing companies (lessors) through the financial strategy described above; (ii) in the current policy environment, lessors are able to access additional financial incentives that buyers cannot access, particularly accelerated depreciation (Bolinger 2009; Coughlin & Cory 2009); (iii) economies of scale present in the operation of a larger fleet of leased systems; (iv) ability for lessors to raise capital at a lower cost, which would increase their leveraged return on capital; and (v) since the lease contracts are typically only 15 to 20 years as compared to the generally reported lifetime of PV panels of 20 to 25 years, leased systems will likely have some residual value. In theory, the lessors could recoup the residual value at a later date, which would allow them to offer the leased systems at lower rates today. All of these mechanisms would lower costs faced by lessors and thereby reduce the size of the lease payments required to achieve a given rate of return. In a competitive leasing market, these mechanisms would translate into lower costs faced by lessees, just as we find. A deeper explanation of these aspects would require financial analysis of the leasing companies’ balance sheets, which is beyond the scope of this paper

If leasing is financially more attractive, why don’t more adopters choose to lease? For

many, the option didn’t exist. 73% of buyers reported not having the option to lease when making their decision. There is also evidence in the literature of conspicuous consumption for novel ‘green’ technologies (Dastrop et al.

2011; Sexton 2011); under this paradigm, consumers could derive additional utility from the status gained by owning, rather than leasing, their systems. Residence uncertainty was not a factor, as each group reported a similar (10-15 years) period that they expected to continue living in their homes. Finally, a majority of PV adopters who had the option to either buy or lease a PV system, but chose to buy, report concerns about potential difficulties with the leasing contract as a factor in their decision to buy. Considering all these factors, we conclude that buyers who did have the option to lease, but chose to buy, had adequate cash-flow such that they preferred the contractually simple buying option, even though the leasing option is nominally cheaper.

4.2 Payback Period Comparison Consistent with previous research (Camerer et al. 2004; Kempton & Montgomery 1982; Kirchler et al. 2008), the majority of respondents (66%) reported using payback period to evaluate the financial attractiveness of their investment as opposed to NPV (7%), internal rate of return (27%), net monthly savings (25%), or other metrics (6%). 10%

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2 made no estimate of the financial attractiveness. Respondents also reported the values of the metrics they used. These responses allow us to compare reported metric values (reported) to the values individually generated from the financial model (modeled) (Figure 2; only baseline scenario shown).

For buyers, Scenario 4 minimized the average absolute difference between reported and modeled payback period (M = 2.6 years, SD = 2.4), followed by Scenario 5 (M = 3.1, SD = 1.9). For lessees, Scenario 3 (M = 1.1, SD = 0.7) was the best fit, followed by Scenario 2 (M = 1.296, SD = 0.704). Scenario 1 was a poor fit overall. This suggests that buyers assumed parameters similar to those of Scenario 4 when evaluating their investment.

That is, buyers were optimistic when assessing the likely revenues and costs associated with their investment decision. By the same argument, lessees were more realistic and precise when making their investment decision. This is consistent with the fact that lessees receive much of this financial information from leasing companies, who use detailed and sophisticated financial models.

Comparison of reported and modeled payback period in scenario 3. Mean difference between modeled and consumer payback period: Buyers = 7.1 yrs-1; Leasers = 1.1 yrs-1.

estimates the respondent’s implied NPV by extrapolating how much more the respondent would have paid before becoming indifferent to purchasing the system or forgoing the investment (Figure 3).

Of the 210 respondents in our dataset, 92 responses were excluded from these calculations — 69 whose implied NPV was outside the range tested ($0 to $5,000), 7 responses which implied an increasing willingness to pay, and 16 non-responses. Of the excluded respondents, 55 respondents indicated they would have been willing to pay

at least $5,000 more for their system, of which 76% were buyers and 24% leasers. That is, a significant percent of the sample (26.2%) did assign a positive value to their investment, yet were not captured within this calculation because of insufficient data. In the end, there are 81 buyers and 37 lessees remaining for the discount-rate analysis reported in this section.

Using the implied NPV, we solve for the monthly discount rate (rm) required to equate the respondent’s

4.3 Implied Discount Rate For all calculations of NPV reported above a 10% annual discount rate was assumed.

In this section we present discount rates calculated separately for each individual respondent. Specifically, we first determine each respondent’s implied NPV and then back-calculate their discount rate using the implied NPV and their modeled cash flows.

To determine the implied NPV, respondents were asked on a 5-point Likert-scale how strongly they agreed with the following five statements: (i) “I would not have installed the PV system if it had cost me $1,000 more”… (v) “I would not have installed the PV system if it had cost me $5,000 more.” One expects respondents to increasingly agree that they would not have installed the PV system as the price increased. The above question

Distribution of implied NPV/kW for buyers and leasers; Difference of mean is not significantly different than zero.

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implied NPV with the cash flows modeled earlier:

[Rk — Ck]

NPVimplied = ΣCFk =Σ

(1+rm)k

The monthly discount rate is then annualized using: r = 1 + rm – 1 Thus, r represents each respondent’s discount rate implied by their willingness-to-pay and their modeled cash flows. As the cash flows vary with each scenario, implied discount rates also vary with scenarios.

Using baseline (Scenario 3) parameters, the mean discount rate for buyers was 7 ± 5% and for lessees was 21 ± 14% (± 1 σ ) (tables 2 and 3). The calculated implied discount rates are higher in the optimistic scenarios since cash flows increase as the scenarios become more optimistic. Across all scenarios and income levels lessees’ implied discount rates are significantly higher than buyers by 8 21%.

It’s important to note a similarity in the timing of leased and bought payments — the majority (69%) of lessee respondents chose to structure their leases as a single ‘prepaid’ down payment, which is similar to the financial structure of a bought system, but significantly smaller in the scale of investment. After taking all incentives into account, for lessees the upfront payment is on the order of $4000 and for buyers it is $15,000 for a 6 kW-DC system. Yet each group expects to receive a similar (normalized) NPV for their investment. That is possible only when these groups have differing cash urgencies. Indeed, in open-ended survey questions, 66.2% of lessees agreed or strongly agreed that tight cash-availability was one of the key factors in their decision to lease, whereas buyers generally did not have this problem. Given that there are little, if any, demographic differences between buyers and lessees, we infer that at this stage in the residential PV market buyers and lessees represent different consumer segments within 5 4 SOLAR POWER WORLD

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a similar socio-demographic makeup. Put differently, compared to the average buyer the average lessee is not lower income per se — the majority of the lessees have some cash availability, but not enough to outright buy their PV system.

In general, our point is that within populations with similar demographics, it’s possible that there are variations in disposable income, and those variations are a key factor in ownership model choices. Consistent with a large body of work in the diffusion of innovations tradition (Rogers 2003), our results suggest that there is a hierarchy within the population regarding the adoption of technologies. In early stages of technology diffusion, as is the case with PV now, information (awareness of products, interest in energy, etc.) is the precursor, which is more likely to be found in higher income, more educated segments of the population. Within those segments, those with tighter cash flows opt for leasing if the option is available. Thus, the leasing model appears to be especially effective in the early stages of a technology’s diffusion, as it unlocks the cash-strapped but information-aware segments of the market.

Put differently, the leasing model accelerates the early adoption stage of a technology’s diffusion, thereby quickly establishing a wider base upon which later adoption can build.

4.3.1 Discount Rate and Income Previous literature starting with Hausman

(1979) suggests that an inverse relationship exists between household income and consumer discount rate. That is, poorer consumers have more urgent needs for their cash than wealthy ones. At higher incomes, where one has a greater degree of spare income, the rate of return of investments (and hence, their discount rate) should converge to market returns. Our results are mixed in regard to these earlier findings.

A one-tailed t-test comparing the difference in mean discount rate among income groups for the baseline scenario was performed using the hypotheses Ho: DR1 = DR2, Ha: DR1 > DR2, and Ho: DR2 = DR3, Ha: DR2> DR3, where DR1 is the mean implied discount rate for income group 1 and so on.

This test was performed for both income pairs (DR1>DR2>DR2>DR3) since we expect the implied discount rate to monotonically decrease with income.

Even with a 90% confidence interval, we did not find a statistically significant relationship between income and discount rate for either buyers or lessees. We explain this discrepancy with two reasons. First, small sample size, particularly in the leasing sample, reduced our test’s statistical power. Second, both groups exhibit characteristics typical of early adopters — wealthier, more educated, etc. These characteristics could negate the relationship between income and discount rate for products in settled markets as early adopters typically derive additional utility

Table 2. Mean implied discount rate for buyers along income and scenarios with ±1σ

All Incomes N 81 Scen 2: 6% ± 6% Conservative Scen 3: 7% ± 5% Baseline Scen 4: 13% ± 6% Optimistic Scen 5: V. 18% ± 7% Optimistic

Buyers

$0 – $85k 22

$85k – $150k 37

$150k+ 22

6% ± 5%

6% ± 8%

7% ± 6%

7% ± 4%

6% ± 6%

7% ± 6%

12% ± 5%

13% ± 6%

13% ± 7%

17% ± 5%

18% ± 7%

17% ± 8%

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References Allcott, H. and Mullainathan, S, (2010). Behavior and energy policy. Science, 327, pp 1204 -1205.

Barbose, G, Darghouth, N., and Wiser, R. (2012). Tracking the sun V: A historical summary of the installed price of photovoltaics in the United States from 1998 to 2011. Environmental Energy Technologies Division, Lawrence Berkeley National Laboratory.

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Table 3. Mean implied discount rate for leasers along income and scenarios with ±1σ

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from adopting new technologies beyond financial benefits (Faiers et al. 2007; Labay & Kinnear 1981; Rogers 2003). In agreement with previous literature, we do find that discount rates for buyers in the conservative, baseline, and optimistic scenarios (Scenarios 2-4) ranges between 7 and 13%, which is close to market returns. This also supports our finding that buyers of PV systems are in a relatively comfortable cash-flow position.

Conclusion We have studied the economics of the decision-process of individual consumers, particularly their decision to buy or lease a residential PV system. Consistent with several other studies, we find that a majority of PV adopters used payback period — not net present value (NPV) — as the decisionmaking criterion. We also find that owing to the peculiarities of financing and incentive mechanisms, the pre-rebate installed costs of leased PV systems are significantly higher than the bought systems, yet lessees end up paying nominally much lower amounts than buyers of PV. We calculate individual-level discount rates across a range of scenarios, finding that buyers employ discount rates 8 to 21% lower than lessees. Those who lease typically have a tighter cash flow situation, which, in addition to less uncertainty about technological performance, are the main reasons for them to lease. As we do not find any significant variation between buyers and lessees on any socio-demographic dimension (income, age, etc.) this suggests that the www.solarpowerworldonline.com

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Camerer, C., Loewenstein, G., and Rabin M, eds, (2004).

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leasing model is making PV adoption possible for a new consumer segment — those with a tight cash-flow situation. As the diffusion of PV spreads to lower-income households, who generally experience tighter cash-flow than wealthier households, this implies that, ceteris paribus, moving forward the leasing model will likely be the predominant form of PV adoption.

From this perspective, the leasing model has opened a new market segment at existing prices and supply chain conditions — and represents a business model innovation. SPW

Coughlin, J. and Cory, K., (2009). Solar Photovoltaic Financing; Residential Sector Deployment. National Renewable Energy Laboratory Technical Report. NREL/TP-6A2-44853, March 2009.

Darghouth, N.R., Barbose, G., and Wiser, R, (2011). The impact of rate design and net metering on the bill savings from distributed PV for residential customers in California, Energy Policy, 39(9), September 2011, pp5243-5253, ISSN 0301-4215, 10.1016/j. enpol.2011.05.040.

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Note that the upfront cost-of-ownership does not reflect the operational life of PV systems or their performance over that lifetime. In general, most analyses assume an operational life for PV systems of 20-25 years, which is applicable to buyers of PV systems. Lease contracts typically terminate after 15-20 years. So the difference in the upfront cost-of-ownership of bought vs. leased systems should be put in this context.

However, as discussed below, NPV calculations incorporate this difference in the length of cash flows.

1

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Faiers, A. and Neame, C. (2006). Consumer attitudes toward domestic solar power systems. Energy Policy, 34(14), September 2006.

Frederick, S., Loewenstein G. and O’Donoghue ,T., (2002). Time discounting and time preference: a critical review, Journal of Economic Literature, American Economic Association, 40(2), pp 351-401.

Discuss This and other Solar issues at www.engineeringexchange.com

Fuchs, D.A. and Arentsen, M.J. (2002). Green electricity in the market place: the policy challenge. Energy Policy 30(6). pp.

525–538.

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Gallagher, K.S. and Muehlegger, E. (2011). Giving green to get green? incentives and consumer adoption of hybrid vehicle technology. J. of Environmental Economics and Management, 61, pp. 1-15.

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Gately, D, (1980), Individual discount rates and the purchase and utilization of energy-using durables: comment, Bell Journal of Economics, 11(1), p. 373-374.

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Contemporary Economic Policy, 13(3). July 1995, pp 101.

National Renewable Energy Laboratory (2009). Solar leasing for residential photovoltaic systems, NREL/FS-6A2-43572, http://www.nrel.gov/docs/fy09osti/43572.pdf, accessed October 7th, 2012.

Public Utility Commission of Texas (PUCT). (2012), Arrangements between qualifying facilities and electric utilities, §25.242, 2012.

Rai, V. and McAndrews, K., (2012). Decision-making and behavior change in residential adopters of solar PV. Proceedings of the World Renewable Energy Forum, Denver, Colorado, May 2012.

Roe, B., Teisl, M. F., Levy A., and Rissell, M., (2001). US consumers’ willingness to pay for green electricity. Energy Policy, 29(11), pp 917-925.

Rogers, E.M., (2003). Diffusion of innovations, 5th ed. New York: Free Press 2003.

Ruderman, H., Levine, M. and McMahon, J., (1987), The behavior of the market for energy efficiency in residential appliances including heating and cooling equipment, The Energy Journal, 8(1), pp. 101-124.

SEC (2012). Security and Exchange Commission Form S-1, SolarCity Corporation. October 5, 2012. Available from SEC online database. Accessed December 13th, 2012.

Sidiras, D.K. and Koukios, E.G. (2004). Solar systems diffusion in local markets.

Energy Policy, 32(18). pp. 2007–2018.

Jager, W. (2006) Stimulating the diffusion of photovoltaic systems: a behavioural perspective, Energy Policy, 34(14), September 2006, pp 1935-1943, ISSN 0301-4215, 10.1016/j.enpol.2004.12.022.

Johnson, K. et al (2012). Lessons learned from the field: key strategies for implementing successful on-the-bill financing programs. Energy Efficiency 5(1) February 2012. p. 109 119 DOI: 10.1007/s12053-011-9109-7

Sexton, S.E. (2011). Conspicuous conservation: the Prius effect and willingness to pay for environmental bona fides Working Paper. http://works.bepress.com/ sexton/11. Accessed October 7th, 2012.

Shih, L.H., and T.Y. Chou, (2011). Customer concerns about uncertainty and willingness to pay in leasing solar power systems. International Journal of Environmental Science and Technology, 8(3), pp 523-532.

Keirstead, J. (2007) Behavioural responses to photovoltaic systems in the UK domestic sector, Energy Policy, 35(8), August 2007, pp 4128-4141, ISSN 0301-4215, 10.1016/j. enpol.2007.02.019.

Todd, P.M. and Gigerenzer, G., (2003). Bounding rationality to the world. J. Econ. Psychol. 24, pp 143–65.

Kempton, W. and Montgomery, L. (1982) Folk quantification of energy, Energy, 7(10), October 1982, pp 817-827, ISSN 0360-5442, 10.1016/0360-5442(82)90030-5.

Tversky, A. and Kahneman, D. (1974). Judgment under uncertainty: heuristics and biases. Science 185, pp1124–31.

Kirchler, E., Hoelzl, E., and Kamleitner B. (2008). Spending and credit use in the private household, Journal of Socio-Economics, 37(2), pp 519-532.

Taylor, M. (2008). Beyond technology-push and demand-pull: lessons from California’s solar policy, Energy Economics, 30(6), November 2008, pp 28292854, ISSN 0140-9883, 10.1016/j.eneco.2008.06.004.

Kollins, K., Speer, B., and Cory, K. (2010). Solar PV project financing: regulatory and legislative challenges for third-party PPA system owners. National Renewable Energy Laboratory. Technical Report 6A2-46723. February 2010.

Labay, D.G. and Kinnear, T.C. (1981). Exploring the consumer decision process in the adoption of solar energy systems. Journal of Consumer Research, University of Chicago Press, 8(3), pp271-78, December.

Laitner, J.A. et al. (2003). Room for improvement: increasing the value of energy modeling for policy analysis, Utilities Policy, 11, 87-94.

Margolis, R. and Zuboy, J. (2006). Nontechnical barriers to solar energy use: review of recent literature. National Renewable Energy Laboratory Technical Report. NREL/TP520-40116, September 2006.

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U.S. Department of Energy (2012). Sunshot vision study. Washington, D.C.: Government Printing Office. http://www1.eere.energy.gov/solar/pdfs/47927.pdf U.S. Department of Energy (2008). Multi Year Program Plan 2008 – 2012.

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Wilson, C. and Dowlatabadi, H. (2007). Models of decision making and residential energy use. Annual Review of Environment and Resources, 32: 169-203, DOI: 10.1146/annurev.energy.32.053006.141137

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4/19/13 10:28 AM

[D EV ELOPMENTS ]

Solar-Powered Village Helps Women Overcome Trauma

The city of Bukavu in the Democratic Republic of the Congo, also known as the City of Joy, was established in 2012 as a refuge for female survivors of sexual violence, which has spread during decades of war in the region. The community houses more than 180 women and offers programs to help them become leaders in their communities and learn skills to provide for their families when they return to their villages.

But what makes the village even more fascinating is that it’s solar-powered. Previously, the City of Joy was powered by the Congo’s unstable national electric grid, which provided electricity for only a couple hours a day, and a backup diesel generator.

The generator was oversized for the community’s needs, loud, polluting and expensive to operate.

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[ DEVEL O P ME N T S ]

Solar Snow Management Last August, Green Empowerment, Global Green USA and V-Day partnered with companies like Trojan Battery Co., SMA, SunPower and Solartechnik Stiens to provide a 7.2-kW solar installation to power the city. The solar panels were installed on the roof of an existing walkway and provide clean energy to all of the buildings at the site.

By using an AC-coupled system design, the installation acts as a microgrid and allows the buildings to share the electricity from the array and batteries.

The grid-tied (with battery-backup) hybrid system allows the solar panels to convert sunlight into electricity during the day. Excess electricity produced by the solar panels, the national grid or a diesel generator is stored in Trojan deep-cycle batteries, so the community has reliable electricity 24 hours a day.

When operating at its full yearly capacity of 9,885 kWh, the solar system is estimated to save the City of Joy more than $6,000 per year by offsetting the cost of diesel fuel. The locals can operate and maintain it on their own.

The installation team faced some challenges while installing the system.

Lack of basic electrical equipment and tools like conduit, electrical boxes and wood made it difficult to work efficiently. There were hammers without nails and drills without drill bits, but after 10 days of hard work the solar system turned on. And when the power went out in the city that night, the City of Joy stood alone as a beacon of hope and a symbol of a sustainable future when the surrounding areas went dark.

SPW

Solar isn’t just for locations that are warm all year. Solar energy is rapidly catching on in areas such as the East Coast. This is great, but it does pose some problems you won’t find in California — like snow. One company has come up with a product that solves any issues with the white stuff.

The calculated snow load of a solar panel is approximately 800 lbs/panel (50 lbs/sq.ft. x 16 sq.ft. average panel). Solar panels (by their nature glass/hard roof surface, no friction) allow built-up snow to release in an avalanche manner, with the potential to cause serious injury, damage or even death.

But Alpine SnowGuards and EcoFasten Solar offer a system that is designed to clamp to the solar-panel frame.

The company says it does not penetrate or scuff the frame and, more importantly, does not shade the collector surface.

The Solar Snow Management system can serve as a pad-style system, pipestyle or both. The system allows snow and ice to melt and slowly slide off the panel’s surface, instead of releasing it suddenly. It uses a “T” nut clamping design that will fit between panels set as close together as 1/8-in. Moreover, a Solar Snow Pad can be incorporated during the initial array installation or can be retrofit into an existing system.

Solar Snow Pads add friction to a frictionless surface, allowing snow and ice to melt off the panel in a managed fashion. Snow accumulation on a solar panel will build up against, slump and then slide off the pad. Snow will fall from one pad and hit against another pad attached to the array lower on the roof.

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Solar snow retention can’t be used in areas where more than 50 lbs of snow fall annually.

The pads are designed to measure 1.25 inches off roof surface to prevent shading. Some shading will occur during the solstice, although not during the hours of collection. Rods cause little shading, making them an add-on option where a greater barrier is needed.

In some cases, the Solar Snow Pads may not be enough. A “barricade” system may be needed if any snow falling off the roof creates a dangerous situation. For optimum snow management, the company recommends choosing a solar/snow barricade design. For optimum solar panel function, it recommends a Solar Snow Pad. SPW

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[D EV ELOPMENTS ]

Wheelchairs Run On Solar

Sandro Buff

Electric wheelchairs are typically powered by the main utility grid and require two 12-V rechargeable batteries.

But 10 people at the Quimby Huus, a home for the physically disabled in St. Gallen, Switzerland, have chairs powered by something else. They are driven exclusively by solar.

Sandro Buff, a resident at the home, had used a wheelchair for more than a decade and wanted to derive power for it entirely from renewable energy. He quickly gained the support of the Quimby Huus manager.

After finding a sponsor to fund the project, Buff worked with energy adviser

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Peter Grau and installed a 3-kW solar power system with 12 Kyocera solar modules on the roof of the home. The power generated from this installation (about 3,000 kWh annually) enables the residents to travel approximately 1,500 km per year in their wheelchairs.

Moreover, an energy meter was installed to give inhabitants a clear picture of how much energy has been consumed, which increases their awareness of energy consumption and offers additional potential for conservation. The project also aims to serve as a motivation for others to implement their own initiatives.

Sandro Buff was awarded the 2012

Swiss Solar Prize for the project. He is convinced that everyone must play their part in reversing energy trends and believes that together society can face the challenge. SPW

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[PRODUCTS ]

Inverter Delivers 97.3% Efficiency

Protection Against Lightning

The Danfoss DLX UL PV transformer-

ABB’s new surge protection devices (SPDs)

based inverter series are UL and

will protect panels from direct and indirect

cUL-listed string inverters that deliver

lightning strikes. The PV-specific SPDs are

97.3% efficiency. Galvanic isolation

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voltages of 600, 800 and 1000 VDC, all with

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indoor or outdoor mounting. At 42 to 46 lbs., 2.0, 2.9, 3.8 and 4.4-kW models are available.

Frameless Module Resists Degradation

Danfoss www.danfoss.com

The 60-cell PDG5, a dual-rated frameless module, is resistant to induced degradation and microcracking, and doesn’t require grounding.

Trina Solar replaced traditional backsheet materials with heat-strengthened glass, allowing the module to withstand high temperatures and humidity. It also features increased resistance to module warping and degradation from UV rays, sand, alkali, acids and salt mist. With reduced glass thickness from industry-standard 3.2 mm to 2.5 mm, and an antireflective coating on the front glass, transmission is enhanced by an estimated 2.5%. The modules are for 1000V IEC and 1000V UL applications.

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[ PR O D U C T S ]

Troubleshoot With Thermal Cameras FLIR, maker of thermal imaging cameras, and Solmetric, manufacturer of measurement tools, teamed up to offer cameras specifically useful to the solar industry. Solmetric recommends FLIR’s i7 and E40 cameras for solar applications. A complete PVsystem commissioning, verification and troubleshooting kit should include an IR camera alongside an I-V curve tracer, shade-measurement tool and insulationresistance tester, the companies say. The cameras can help identify hot spots on modules, balance-of-system and non-producing modules and strings.

Solmetric www.solmetric.com

A Certain Disconnect X, T and L For Tight Spaces

Located at ground level, the Birdhouse emergency disconnect switch provides a safe means to disconnect high-voltage PV

ILSCO has made enhancements

arrays. The switch features a hard-wired

to its NIMBUS4FLEX line of

connection that gives positive feedback

pre-insulated solar connectors.

that the disconnect on the roof has actually

The three new configurations include an

been thrown. Connection is via 600/1000V

X, T and L. These new configurations may solve

Category 5 USE-2 cable. A voice confirms

space-constraint wiring issues when working in small

the level of safety to the person pushing

control panels or wiring troughs. Configurations include 2-,

the button. MidNite Solar says Birdhouse is

3- or 4-port design and come standard with ILSCO’s patented

firefighter approved.

screw design, which means the product is reusable. NIMBUS connectors are UL Listed, CSA Certified, RoHS Compliant and dual-rated for copper or aluminum conductors.

MidNite Solar www.midnitesolar.com

ILSCO www.ilsco.com www.solarpowerworldonline.com

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[PRODUCTS ]

A Power Block With More Amps The Bulk Fastening Power Block provides a series of fasteners to terminate numerous combinations of listed crimp lugs or flexible busbars to distribute power. Marathon Special Products’s power block can reliably terminate large, flexible-stranded wire. The product features a current carrying capacity up to 1605 amps, a voltage rating up to 1000V AC/DC, high short-circuit current ratings (SCCR) and meets the requirements for use in feeder circuits. The SCCR includes the industry’s first 35K approvals with no overcurrent protection requirement and 100K SCCR with specified overcurrent protection.

Marathon Special Products www.marathonsp.com

Telescoping Rafters For A Faster Install Sun Bear, a penetrating ground-mount system, includes four major components and zero loose fasteners.

PanelClaw says this results in fast installation times and reduced construction risks and costs. Struts can be attached to any Sun Bear foundation type, allowing for a range of soil conditions without needing to change the above-the-ground racking design. Integrated turnbuckles allow installers to adjust the system directly in the field to accommodate uneven terrain, adapt to foundations and level the array for a smooth appearance. The telescoping rafters of the Sun Bear frame slide out into a locked, squared position in-field, speeding up the installation process.

Panel Claw www.panelclaw.com 6 4 SOLAR POWER WORLD

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[ PR O D U C T S ]

Tracker Has Modular Design The wind-tunnel tested Solar FlexRack Tracker can increase PV-module energy production up to 25%. The system also includes advanced programming features that maximize output and assembles simply with just two people. The tracker has a modular design to simplify dealing with terrain obstacles and topography, +/-50 degrees rotation capabilities that produce 1 to 2% additional kWp, and can be customized to fit most PV panel sizes. The tracker features a dual-redundant Zigbee network, and a wireless network control allows for off-site monitoring.

Its backtracking feature eliminates inter-row shadowing and allows the installation of more trackers in a given area.

Solar FlexRack www.solarflexrack.com

Flat-Roof Mounting That Multi-Tasks To reduce system costs, each component of Schletter’s flat-roof mounting system Fix-EZ serves multiple purposes. The ballast blocks act as a support mechanism, and the rails serve as a windbreak. The system offers wind-tunnel testing, ETL-Listed integrated grounding and is 100% IBC code compliant. The ballast blocks have threaded steel inserts for a secure system connection. An L-Foot with KlickTop offers fast rail installation, and a Rapid 2+ clamp provides integrated grounding.

Schletter www.schletter.us www.solarpowerworldonline.com

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4Q

[FOUR QUESTIONS]

4 QUESTIONS: A New Kind Of Solar Garden (Editor’s Note: This conversation has been edited for space. For the full answers, check out our 4 Questions feature on www.solarpowerworldonline.com).

When Solar Power World heard about Green Roof Technology’s Sun-Root System, an integrated, nonpenetrative solar and green-roof system that optimizes photovoltaic energy production by creating a cooler surrounding microclimate through evaporation and evapotranspiration, we reached out to Ryan Miller, director of the company’s Baltimore office. He was kind enough to answer SPW’s 4 Questions.

SPW What is the concept behind the Sun-Root System?

Miller With rising energy costs and increasing federal and state incentives for solar panels, we now have a vehicle to show a client that you can make your money back in as little as three years. We can show them that you will save X amount on your energy bill and X

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amount on your upfront costs. We show them these numbers then say, “Oh yeah, let’s not forget about the green roof that reduces your stormwater footprint, increases your building’s efficiency and doubles or even triples the lifetime of your roof membrane.”

SPW

You have an unusual product in the Sun-Root System. Is it difficult to install?

Miller The Sun-Root System is simple to install with some basic knowledge of green roofing. Because each Sun-Root module weighs less than 5 pounds, they are easy to handle and maneuver. Modules are placed on top of a protection fabric and then properly orientated. Once in place, a capillary fabric is laid on top of each module and covered with an engineered soil (i.e. the growing media) that provides the ballast

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4/19/13 9:55 AM

4Q [FOUR QUESTIONS]

for the entire system. Each Sun-Root module is connected to the next by a dual horizontal photovoltaic panel-racking bar.

With the racking bars in place, the solar panels are mounted as you would for any traditional solar array. Once the modules are secured, you are ready to plant the vegetation, which is the icing on the cake.

SPW

How many installations do you have at this time and how many are in the pipeline?

Miller Currently in the United States, there is one project

installed at the 5-Boro’s Building on Randall’s Island in New York.

Four more larger scale projects are in the pipeline for 2013. Since the Sun-Root System’s development five years ago in Germany, it has been installed on over 150,000 sq. ft. of roof space.

SPW Why hasn’t anyone come up with something like this before?

Miller This idea of combining PVs with green roofs has been around since modern green-roof technology was developed 30 years ago in Germany. We have numerous pictures in our archives that demonstrate the myriad ways people have tried to integrate modules and green roofs. In the end, for more 25 years, PV racking arrays were simply installed above an extensive green roof with no integration.

Not until Optigrün AG put the time and money into R&D did a fully integrated solar green-roof materialize. The result was the Sun-Root System. It is the only solar green-roof system to integrate the mounting module directly into the drainage layer of the green roof. The module is engineered to promote evapotranspiration, in which the water stored in the green roof is released through evaporation, which cools the solar panels.

The final outcome is a solar green-roof system that supports healthy vegetation and strong enough to hold solar panels by using the weight of the green roof. The added benefit of a 10% increase in energy output, because we keep the panels cooler during the day, was just a bonus. SPW

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'ŽůĨ /Ŷ dŚĞ DŽƌŶŝŶŐ

ŽŵĞ ƚŽ ďĞĂƵƟĨƵů WĂůŵ ^ƉƌŝŶŐƐ͕ ŐŽůĨ Žƌ ƌĞůĂdž ŝŶ ƚŚĞ ŵŽƌŶŝŶŐ͕ ĂŶĚ ĂƩĞŶĚ ĐůĂƐƐ ŝŶ ƚŚĞ ůĂƚĞ ĂŌĞƌŶŽŽŶ͊ /Ŷ-ĚĞƉƚŚ ŬŶŽǁůĞĚŐĞ ŽĨ ĚĞͲ ƐŝŐŶ͕ ƐŝƚĞ ƐƵƌǀĞLJƐ͕ ƐĂůĞƐ ƚĞĐŚŶŝƋƵĞƐ͕ ĐŽƐƚ ĂŶĂůLJƐŝƐ͕ ŝŶĐĞŶƟǀĞƐ͕ ĂŶĚ ĞīĞĐƟǀĞ ĐƵƐƚŽŵĞƌ ĐŽŵŵƵŶŝĐĂƟŽŶ͘ dŚĞ ƉƵƌƉŽƐĞ͗ /ŶĐƌĞĂƐĞ ƐĂůĞƐ ĂŶĚ ĞŶƐƵƌĞ ĐƵƐƚŽŵĞƌ ƐĂƟƐĨĂĐƟŽŶ͘ dŚŝƐ ŝƐ ƚŚĞ ƉĞƌĨĞĐƚ ŽƉƉŽƌƚƵŶŝƚLJ ĨŽƌ ƐŽůĂƌ ĐŽŵƉĂŶŝĞƐ ƚŽ ƌĞǁĂƌĚ ĚĞĚŝͲ ĐĂƚĞĚ ƐĂůĞƐ ƐƚĂī ǁŚŝůĞ ŝŶĐƌĞĂƐŝŶŐ ƚŚĞŝƌ ŬŶŽǁůĞĚŐĞ ĂŶĚ ƐĂůĞƐ ƐƵĐĐĞƐƐ͘

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EĞdžƚ ĐůĂƐƐ͗ :ƵůLJ ϵ ƚŽ :ƵůLJ ϭϯ

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