Solar Power World - NOVEMBER 2012

November 2012 www.solarpowerworldonline.com

Technology • Development • Installation

INSIDE: >> Racking and mounting: NEW CELLS FOR ALCATRAZ Page 22

>> Solar Business: These companies support solar Page 34

>> Manufacturing Processes: Production Begins At Conception Page 38

The Capitalist Ca e for Solar Page 28

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Editorial Advisory Board Natalie Holtgrefe Solectria Renewables Jose Gomez Ingeteam Raheleh Folkerts Renewable Energy Systems Americas Steve Hogan Spire Gary Mull Westinghouse Solar 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

Now We Can Get Back To Business I’m writing this at the end of October. The election is still too close to call, but here is one thing I am certain about: Even I will be glad when it’s over.

We’ve spent much of the last 18 months (didn’t it seem like a decade?) debating, arguing and sometimes fighting about which candidate would be best for the solar industry. I made my position abundantly clear, and those on the opposite side of the political spectrum did, too. It was an incisive, spirited debate, and I’m glad to have taken part in it.

On Nov. 6, the American people will make their decision. Regardless of who wins, we’ll all get back to doing what we do best — working to further the best interests of the solar industry.

Here is my five-point list of items that should top our agenda in 2013: 1. Many of you may know that I’ve been on the subsidy bandwagon for more than a year, and I’ve taken a lot of heat for it. But I had a conversation with Peter Lynch, a board member of the Principal Solar Institute, who made a compelling case for a feed-in tariff instead. I’m now on board: Scrap the subsidies. Getting a national FiT should be our top priority in 2013.

2. We must find a (relatively painless) way to accelerate the industry’s inevitable consolidation. The slow drip of high-profile bankruptcies is drowning out the good-news message of our industry. It needs to end sooner rather than later.

3. The Chinese tariff decision, for better or worse, has been decided. It split the industry, and blood was spilt. Now it’s time to bind those wounds and unite again to push our industry forward with one voice.

4. We must have national licensing for solar installers. I’m not sure what body would be the most appropriate to do this, but the barriers to entry for this industry are too low. As my friend Yann Brandt articulated so well on his blog (and our website), “solar schemers” have the potential to sink the industry. We can’t allow that to happen.

5. We must hold the president’s (and Congress’) feet to the fire to make sure they build policies that support our industry, now and in the future. They won’t support what they don’t understand, so make your voices heard. By the time you read this, the election will be over — but advocacy on behalf of our industry should never stop.

I’d love to hear what’s on your solar priority list in 2013. Please drop me a line at fandorka@solarpowerworldonline.com or call me at 440-234-4531 (Ext. 110).

Frank Andorka

Editorial Director fandorka@solarpowerworldonline.com

www.solarpowerworldonline.com

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Industrial Wireless

Industrial Ethernet

Serial Connectivity and Networking

Embedded Computing

Smart Solar Ideas from Moxa

The IA3341 Series RISC-based Industrial Embedded Computer Moxa ART 32-bit ARM 9 Industrial Processor 4 DIs and 4 DOs with 3 KV digital isolation protection 2 AIs and 2 thermocouple inputs; sensor types J, K, T, E, R, S, B, N 2 software selectable RS-232/422/485 serial ports 50 bps to 921.6 Kbps serial speed, supporting non-standard baudrates Dual 10/100 Mbps Ethernet ports for network redundancy SD socket for storage expansion

Rcore Software Platform Moxa’s Rcore ready-to-run platform makes it easy for programmers to develop embedded software. Rcore includes easy-to-use application libraries, tested bug-free sample code, and requires less time for the concept validation and development cycle enabling a faster time-to-market that meets or exceeds customer requirements. The Rcore Community also offers our partners easy access to software and technical knowledge about embedded systems, along with an interactive forum to share knowledge with embedded computing professionals.

Visit http://rcorecommunity.moxa.com/ for details.

Supports Modbus TCP library to retrieve AI and thermocouple data

Use your Smart Phone to scan for more information.

Moxa, Inc.

Tel: 1-888-669-2872 Fax: 1-714-528-6778 usa@moxa.com www.moxa.com

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[ SO L AR

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Editor’s Note: Solar Power World is proud to introduce “Solar Snapshot,” a new department that provides 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.

State Rankings by Cumulative Installed Solar Electric Capacity as of Q2 2012 Installed Solar Electric Capacity 1-California 2-New Jersey 3-Arizona 4-Nevada 5-Colorado 6-New Mexico 7-Florida 8-Pennsylvania 9-New York 10-North Carolina 11-Hawaii 12-Massachusetts 13-Texas 14-Oregon 15-Ohio 16-Maryland 17-Tennessee 18-Illinois 19-Delaware 20-Connecticut 21-Wisconsin 22-Washington 23-Vermont 24-Missouri 25-DC Other

State Rankings by Q2 PV Installed Capacity Residential

Sources: (Clockwise from upper left) SEIA; SEIA and Vote Solar; SEIA and Vote Solar; SEIA; BarackObama.com

1-California 2-Arizona 3-New Jersey 4-Nevada 5-Texas 6-Illinois 7-North Carolina 8-Massachusetts 9-New Mexico 10-Hawaii 11-New York 12-Tennessee 13-Pennsylvania 14-Maryland 15-Colorado 16-Oregon 17-Ohio 18-Florida 19-Missouri 20-Washington 21-Connecticut 22-Delaware 23-Wisconsin 24-DC 25-Vermont Other

www.solarpowerworldonline.com

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Commercial

Utility 217 MW 173 MW

103 MW

Residential

Total = 94

Commercial

Total = 196

Utility

Total = 447

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November 2012 • vol 2 no 5 EDITORIAL

New MEDIA/WEB/ Business DevELOPMENT

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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

contents

12 D e pa r t m e n t s

2 0 1 2

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v o l

2

n o

5

38 F e at u r e s

28 The Capitalist Case for Solar

01 The First Word

N ovem ber

06 Developments 11 State of the States 12 Project Review

Despite its (false) reputation, solar is completely compatible with a free-market economy.

03 Solar Snapshot

34 Solar Means Business

18 Future of Finance

38 Taking Solar Products from Concept to Production

20 Training

22 Racking and Mounting

in Photovoltaic (PV) Inverter and the Mitigation Strategies.

56 Products 60 59

Contractors Corner

45 Harmonics and Noise

About the Cover:

50 Test and Verify

Done in the illustration

Will your solar array stand up to heavy winds? Here’s how you can find out.

50

Ad Index

capitalism’s greatest champion Ayn Rand, this imposing skyline made us think of Wall Street, capitalism’s humming hub.

Illustration: istockphoto.com

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[D EVELOP MEN T S

R ESI D ENT I A L] K at h ie Z ip p / As s o c i ate E di to r

The Largest Solar Neighborhood In The Southeast

In the 1940s, the St. Thomas Housing Project provided housing for lowincome residents of New Orleans. But by the 1980s, it had become one of the country’s most dangerous developments.

After Hurricane Katrina, the project received grants from several government agencies to revitalize the neighborhood.

The funds helped build affordable and sustainable housing where St. Thomas once stood.

The new housing, known as River Garden Apartments, is a mixed-income development that stretches eight blocks and spans almost a square mile. It’s also the largest solar project in Louisiana, as well as the largest solar neighborhood in the southeastern United States.

Pontchartrain Mechanical Co. installed 420 KW of photovoltaic systems on the development’s roofs.

Installing PV systems on multiple roofs, each with a specific configuration 6

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and mounting angle, posed a challenge for the company. Turning to SolarEdge’s power optimization system allowed using maximum roof space for optimum power harvesting, even in areas with partial shading or obstructions.

Generating maximum power from each module, independent of type, string length or mounting angle, was key to the project’s success, the company says.

The SolarEdge system monitors the numerous arrays through built-in, realtime performance data at the module level. The system automatically provides web-based alerts on underperforming modules and faults, and pinpoints affected modules on a virtual site layout map.

Also, the system’s SafeDC mechanism keeps residents, installers, maintenance personnel and firefighters safe. Damaged arrays could potentially start arc faults and home fires. SolarEdge guarantees a safe installation with its inverters and power

optimizers. This has special importance in hurricane-prone areas where flying debris resulting from high winds can damage solar installations.

The residents of the apartments pay $0.10/KWh of electricity. The solar installations on each home were combined, which enabled a volume discount for further reduced electricity costs. Residents are expected to save an average of $50 per month in utility bills.

“We overcame many challenging issues, specifically installing modules on multiple roofs and different angles, in a safe manner and with reduced maintenance costs,” says Micah Galy of Pontchartrain Mechanical Co. “This revitalized community is now able to sustain itself with reliable energy and will be able to stabilize their energy costs for the long term in a clean and sustainable way.” SPW SolarEdge www.solaredge.us

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Moxa Installs Solar At U.S. Headquarters Moxa, a manufacturer of industrial networking products, has partnered with So-Cal Solar to install a 35,000 square-foot solar power system at its global sales-and-marketing headquarters in Brea, Calif. The installation is one of the largest in Orange County and is expected to reduce green house gas emissions by 9,309 tons of CO2 over the next 25 years. The system includes rooftop and carport arrays, and it produces more than 311 KW DC, using 1,133 panels and a central inverter.

“It is important to Moxa to be environmentally mindful as a company through green product design, conservation of natural resources and compliance with ISO 14001 standards,” says Ben Chen, president of Moxa Americas.

Chen says Moxa has also implemented other resource conservation efforts such as low-flow aerators, rain sensors for irrigation and motion sensors for lighting. A Moxa team will research other means of conserving resources, such as retrofitting parking lights to LED, an electronic HVAC system and a building energy-management system.

The solar power system is also an opportunity for Moxa to provide education on solar technology and related Moxa solutions. Visitors can see a live-monitoring demonstration and learn about power output and system metrics. The demonstration incorporates Moxa’s own industrial switches, surveillance cameras, computers and I/O modules. A separate monitoring system is also on display to provide a bird’s-eye view of system productivity. SPW Moxa www.moxa.com

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Speedy Solar Installation At Thermalito Hard soil patches posed a challenge for installers

Project Overview Development Group: Elite Solar, City National Bank, Creotecc Solar Mounting Systems Commissioned: Aug. 17, 2012 Installation Time Frame: 45 Days (May 25 through June 10, 2012) High/Low Temperature: 115°F/12°F Annual AC Production: 708,994 KWh

working at a water treatment plant in the Thermalito Water and Sewer District in Oroville, Calif. But they were able to make up for lost time with quick module mounting.

Integrator Elite Solar chose Creotecc’s Creoterra mounting system because of its insertion-rail design, which holds modules without clamps. Instead, modules are inserted into rails, making installation easier than with other systems, the company says.

“I was impressed by how fast and easy the mechanical assembly was, and how quickly the modules installed without clamps,” says project foreman Rich Sanchez.

Creotecc says the Creoterra system suits almost all terrains and site conditions. A versatile pile bracket allows a tilt range of 10 to 50 degrees, and slot nut connectors are fully adjustable. This allows the system to meet demanding site conditions.

Creotecc also delivered the rail to the job site pre-cut. Sanchez estimated a time reduction of 50% when compared to other mounting systems he’s used on similar projects.

“Support from the team at Creotecc was there from the beginning of construction to commis­sioning,” says Kirk Short, owner of Elite Solar. “Creotecc will be my go-to racking based on ease of install, product support and cost. It will keep me competitive in this highly competitive field.”

The system at the treatment plant is expected to eliminate 100% of the district’s electricity bill, resulting in more than $3.8 million in positive cash flow over the 25-year life of the system. SPW Creotecc Solar Mounting Systems www.creotecc.com

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When the temperature is 1000°F Quality and Precision are Critical!

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Offering a variety of materials for challenging environmental conditions and the option of integrating several parts into one piece, Helical’s flexible couplings provide you the perfect design solution for accommodating angular misalignment, parallel offset, and axial motion.

With over 8,000 successful designs and 35,000 satisfied customers served, why not let Helical start coupling your dreams with reality today!

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[ S TAT E O F T H E S T A T E ]

The Solar State By State Reports: Arizona Solar Power World thanks our friends at Vote Solar for allowing us to help get the word out about what’s happening in the solar industry, state by state. Our first installment focuses on Arizona.

Arizona is a rising star in the race among states for solar leadership. It’s now third in the country for solar jobs, according to The Solar Foundation’s 2011 Jobs Census (behind California and Colorado). But given Arizona’s abundant sunshine and burgeoning solar manufacturing industry, the state has made good on only a small sliver of its solar potential. As of August 2012, Arizona had installed 448 MW of solar capacity, or enough to power 57,491 homes. The state ranks third in the United States, right behind California and New Jersey, in solar installed.

On the small-scale solar front, solar incentives are dropping quickly in 2012 as demand for solar soars. We are working with partners in the state to prepare for a “post-incentives” framework. We will focus on the details of solar rate design to ensure the small-scale solar market continues to grow apace.

On the large-scale solar front, we are working to site solar projects efficiently and responsibly.

The Arizona Bureau of Land Management (BLM) has released a first-of-its-kind proposal to map the best areas for renewable energy development throughout the state and to streamline permitting in those areas on BLM lands.

In February 2012, Arizona BLM released a draft environmental impact study (EIS) on its Restoration Design Energy Project (RDEP) website. In May, Vote Solar submitted comments to the BLM in partnership with Arizona utilities, land conservation groups and the solar industry, including detailed suggestions for how to make RDEP most effective at choosing the best BLM lands for solar and how to make the program a model for other states in the future.

Background On Oct. 31, 2006, the Arizona Corporation Commission voted 4-1 to expand the state’s renewable portfolio standard to require 15% renewable energy, and 30% of that to come from distributed generation resources. In 2012, the renewables goal is 3.5% of retail load.

We think much of the renewable energy standard will be met with solar. With a world-class solar resource and strong population growth, Arizona has the potential to emerge as a key solar market.

Arizona currently has no cap on the total amount of solar that can be net metered. Individual net-metered systems are not allowed to exceed 125% of the customer’s total connected load.

Policy Needs and Next Steps Utility implementation of the RES will be an ongoing issue, as will defending the standard from attacks by opponents of clean energy in the state legislature. Long-term, Arizona must keep increasing in-state demand for clean energy to compete with other western states for solar jobs.

Streamlining permitting on federal and private lands will also continue to be a priority. SPW Annie Lappé is Vote Solar’s lead for Arizona. She can be reached at annie@votesolar.org.

www.solarpowerworldonline.com

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Annie Lappé

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Setting The Standard For Solar Storage

Š SolarReserve

The Crescent Dunes Solar Energy Project will provide renewable power without intermittency

O

ne of the greatest issues with renewable energy generation is its intermittency. Utilities still need to provide people with power when the sun is not shining or the wind is not

blowing.

Many times, fossil fuels such as natural gas are used to provide back-up power when renewable sources alone can not generate enough electricity to meet demand. The ability for solar and wind facilities to provide consistent power like conventional coal or nuclear power plants is critical to the widespread success of renewables.

The key to obtaining it is storage, but this is easier said than done.

Many companies are working on such solutions, but one is already implementing its technology into a project that will be operational as soon as next year.

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Renewable Resources Welcome In Nevada Nevada’s great solar resource and renewable portfolio standard has attracted solar development in the state, including interest from Santa Monica, Calif.-based developer SolarReserve.

The local utility NV Energy took interest in the company’s project proposal, particularly because SolarReserve’s core concentrated solar power (CSP) technology has integrated energy storage, which provides the utility with reliable power when needed and solves the utility’s concerns with intermittency from its renewable generators.

Storage: The Holy Grail For Renewables SolarReserve uses molten-salt technology first developed by Pratt & Whitney Rocketdyne, rocket science engineers for NASA. SolarReserve now holds the exclusive worldwide license to commercialize this technology.

Basically, heliostats focus the sun’s energy to the receiver, which sits atop a central tower.

Liquid molten salt is pumped from the “cold” tank at 500 degrees Fahrenheit, up the tower to the receiver, where it collects the sun’s thermal energy. The molten salt is heated to 1,050 degrees Fahrenheit and pumped down the tower, where it is stored in the “hot” tank.

When needed, the thermal energy is released into a heat exchanger to create steam and power a standard steam turbine to generate electricity. In this way, the plant can operate just like a conventional power plant, providing 100% output at any given time — even when it’s not possible for other renewable energy generators to operate, such as in periods of cloud cover or at night.

SolarReserve’s CEO Kevin Smith says this is the Holy Grail for the renewable industry.

“Let’s say the sun shines from 6 a.m. to 5 p.m.,” Smith says. “The utility’s peak

© SolarReserve

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requirements are really noon to 10 p.m. or 11 p.m. — so they want us to run firm baseload during those periods to solve their peak power requirements. We can actually run 24 hours a day if the utility wants us to, and that’s unusual in the renewable energy sector.”

The technology also uses hybrid cooling that keeps water use at a strict minimum, which is especially important in a desert ecosystem like Nevada.

SolarReserve is using it to build the 110-MW Crescent Dunes project near Tonopah.

Crescent Dunes Challenges Though the new technology was intriguing, it took time to convince lenders to finance the project. SolarReserve applied to the U.S. Department of Energy (DOE) Loan Guarantee Program, so the DOE had third parties perform due diligence on the technology, SolarReserve as a developer, NV Energy as a utility and more.

SolarReserve’s Senior Vice President of Development Tom Georgis says ACS Cobra, the project’s engineering, procurement and construction (EPC) firm out of Spain,

reassured lenders with its willingness to guarantee the facility’s performance.

“That obviously makes any lender feel comfortable,” Georgis says. “They just want to make sure they get paid with interest.”

Critical components of the technology came from Pratt & Whitney Rocketdyne, which was at the time a part of United Technologies Corporation (UTC). UTC is a Fortune 30 company that built a pilot solar-tower plant with storage for the DOE to demonstrate its technology.

This also reassured the DOE, which approved a $737 million loan. SolarReserve was relieved to be able to take advantage of the DOE’s program and also the 1603 Treasury Grant Program, which has since expired.

“There was urgency around the financing because of the uncertainty and imposed deadlines on the DOE loan program and the treasury grant,” Georgis says. “We were always in danger of funding getting cut or appropriations not coming through.”

The loan, along with $260 million of private equity from SolarReserve, ACS Cobra and Banco Santander (a global

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REVIEW ]

© SolarReserve

[P Ro j e cT

bank out of Spain), was enough to finance the $997 million project.

Prior to even financing the project, challenges arose in the early stages of development, specifically through the siting and permitting phase. With much of area being federal land or military testing ranges, it was a process to find a location acceptable to all parties.

“We were fortunate not to have environmental or cultural issues for the site,” Smith says. “But we spent a fair amount of time working closely with Nellis Air Force Base and the Bureau of Land Management.”

The Air Force was concerned the 650-foot-tall tower would obstruct flying zones, and that the plant would interfere with its radar. So Georgis says even though the project would encompass only 1,500 acres, he and his team studied more than 20,000 acres to find a site satisfactory to all parties.

To make the site assessment even more challenging, some of the military’s issues were classified.

“It was difficult because we didn’t know exactly what some of the issues were,” Georgis says. “We brought on

a consultant to work with the Air Force’s scientific advisory board. The consultant had clearances to communicate the issues and advise us without disclosing anything. It was challenging dealing with an unknown.”

After adjusting the site a few times, finally a location was found that suited everyone.

But Georgis wasn’t frustrated by the process.

In fact, he viewed it as a great learning experience.

“No one had really built this kind of project on federal land — it was the first of its kind,” Georgis says. “But [Secretary of the Interior] Ken Salazar recognized the importance of this project for Nevada, which

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expedited the process.

Overall, it went pretty smoothly.”

The project began construction in September 2011.

“As far as solar projects in remote locations, it’s one of the easiest interconnects I’ve seen over the past five years,” Georgis says.

It should be generating consistent solar energy by December 2013. During a 25-year power purchase agreement, 100% of the electricity generated will be sold to NV Energy and used to power 75,000 homes during peak periods. It will generate 500,000 MWh annually, which is twice the amount of a similarly sized photovoltaic project.

The local residents of Nye County couldn’t be more thrilled by the economic development and job creation brought on by the Crescent Dunes solar project. During construction, the project will create 600 direct jobs on site, and over 4,300 direct, indirect and induced jobs across the supply chain, with a significant goal of hiring locally first. Once completed, the plant will employ about 50 fulltime workers and generate tax revenue for the region. Georgis says he is grateful for the community’s support.

“The community and elected officials have been fantastic throughout,” he says. “Anytime there was an issue or challenge they could weigh in on, they’ve been more than happy to do so.”

The Beginning Of A Beautiful Thing Though the Crescent Dunes Project isn’t yet finished, SolarReserve is 16

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© SolarReserve

Currently Under Construction

already looking forward to taking its technology to other markets. Smith says it has contracted the 150-MW Southern California Rice Solar Energy Project with Pacific Gas & Electric, has late stage developments in other states across the United States and is also active in areas like South Africa, Peru and China.

“We’re also seeing tremendous interest internationally,” Smith says.

“Utilities and governments want a consistent supply of power from renewable sources. The basis of renewable energy with storage that can provide consistent supply is really key.”

Georgis is also looking forward to the spread of SolarReserve’s moltensalt technology and cautions not to be deterred by the price.

“It certainly is more expensive than PV and wind,” he says. “But we don’t require natural gas-peaking facilities to come online when the sun goes down, or what will be costly transmission

system upgrade requirements to support all the PV and wind that’s coming online.

All of these costs need to be factored in.

This is kind of the best of both worlds — a renewable-energy resource that operates like a conventional power plant. The key issue for solar thermal and other technologies is scale. We need to have more projects financed, into construction and operating. We need to exercise the supply chain, and that’s how we’re going to reduce our costs.” SPW

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

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10/25/12 10:41 AM

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10/23/12 11:58 AM

[FUTURE OF FINANCE]

The Solar Market Post-1603 Grant: Can “Securitization” Make A Difference?

Robert Sternthal President of Reznick Capital Markets Securities

At the Solar Power International show in Orlando this past September, I moderated a panel of leading experts in the solar market representing the following companies: Washington Gas, SunEdison, Clean Power Finance, Martifer Solar and New Energy Finance. Among the many issues we discussed, one that aroused varied opinions was securitization. But prior to discussing it, let’s first define what it is.

As one of the panelists smartly pointed out, securitization means debt. Securitization is the issuance of bonds as a replacement for other potential debt you can use to lever transactions, either at the project or corporate level. The bonds typically have a longer tenor or lower interest rates, are of larger size or otherwise offer some additional advantage to the typical bank market. These bonds are also typically rated, whether publicly or privately, to ensure that insurance companies, banks and other long-term investors can own them with lower capital requirements than if they issued the debt directly.

As Chris Bailey from SunEdison rightly said, when we talk about securitization, we should also include private placements, which are privately placed bonds backed by either portfolios of deals or large single-asset deals like Mid-American’s Topaz issuance.

So my question to the panelists, who seemed to hold an extremely opposite viewpoint from mine, was: “Will securitization make a material difference in the market?”

Though they said yes, my answer was — and is — a resounding no.

Why not? If bondholders will accept longer tenors, lower-interest rates and more construction risks, why won’t securitization change the game for the solar industry in the United States?

Here are a few reasons why I don’t believe securitization is a game-changer: 1. Rating agencies aren’t yet prepared to rate portfolios of deals and, if they are, they will start with residential products prior to moving on to portfolios of commercial systems.

2. Fixed costs of securitization are expensive and are currently hard to overcome.

3. If the bond issuances are limited to less than $1 billion per asset-class annually, investors will continue to charge a premium because of a lack of liquidity of the bonds in the secondary market.

4. Investment banks need to warehouse the debt prior to issuance and the market needs to exist before they will demonstrate such interest.

5. Few sponsors have the balance sheet, track record and wherewithal to become acceptable issuers.

6. Mixing securitization with any sort of tax-equity financing will prove difficult.

Accordingly, for 90% of the solar market, securitization is but a mythological entity. Yes, it will exist. Yes, it will be magical for companies like SolarCity that may be able to avail themselves of it. But for your average or even better-thanaverage developer, sponsor, panel manufacturer or long-term owner, securitization is irrelevant.

As a consequence, I encourage our clients and those other developers in the market to continue to focus on the more conventional forms of financing, many of which are becoming even more commonplace and increasing in scope and scale, while the largest of sponsors figure out how to open up the securitization market for everyone.

SPW

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 Reznick Group and Reznick Think Energy, Reznick Capital Markets Securities offers one of the most comprehensive financial advisory platforms in the industry.

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10/23/12 11:59 AM

[TRAINING]

Accredited Solar Training Makes For A Successful Business The solar industry is young and growing

Sylvia Minton Senior Vice President for MAGE Solar Member of Board of Directors for MAGE Solar Academy

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fast. As a result, many of its professionals have had relatively short experience in the field. Many installers come from other trades and often possess a wealth of experience, which is tremendously valuable on the job. But it’s not solar expertise.

With installation prices around $6.23/W for projects less than 100 KW, according to SolarBuzz U.S. Deal Tracker, installer training is not a luxury anymore — it’s a company’s survival tactic. The more popular and mainstream solar becomes, the more a company must establish itself as a team of trustworthy, experienced professionals that works safely, focuses on quality, and delivers maximum yield and the highest return on the customer’s investment every time.

Why is this particularly vital for smaller installers, who primarily focus on the residential and smallscale commercial market? Because these companies are the heart of the solar industry. Nobody engages with the public more than these folks do. More than 78% of solar companies are installing residential systems, and more than 61% focus on commercial systems up to 50 KW, according to The Solar Foundation. That’s engaging with thousands of citizens on hundreds of installations, every day. For them, obtaining PV-training and certification may be the best long-term business investment they can make in the (potentially) largest solar PV market on the planet.

Dozens of providers offer traditional classes, but online courses, e-courses and crash courses are becoming increasingly common. The educational sector understands that every hour spent studying in the classroom or in front of the computer is time away from installations. Also, more detail-oriented courses are being developed to fill more varied knowledge niches (grounding and bonding, for example).

While meeting needs and accommodating convenience is important when selecting training courses, beware of attending dressed-up marketing classes. Opportunities to “learn” specific products should be provided for free, but they will not 11 • 2012

replace solid, product-agnostic training from a reputable educational facility.

Make sure that the course content is taught

by NABCEP or UL-certified instructors and, when possible, that the content is approved by a neutral authority like NABCEP, so the earned credit hours count toward certification.

Check that the classes are up-to-date in terms of technology, as well as National Electrical Code, or NEC, requirements. In an environment like solar with rapidly changing technology, this is a must.

The 2008 NEC won’t get you far anymore — a detail some providers “forget” to mention.

In the case of a PV 101 entry-level course, for example, evaluate if all relevant topics are covered, from design and construction, to wiring, site analysis, pulling permits, calculating ROI, securing financing, project management, troubleshooting and maintenance issues. If you’re not sure after reading the catalog, ask, and then ask again. Also, inquire about facilities for handson training and how much time is set aside from theoretical instruction to really get down and dirty. More is generally good, and there should be ample time to practice with assistance and feedback from a well-seasoned instructor.

Last, but not least, the best PV-training facilities deliver great after-sales service — the ones where you can go back and continue to ask questions, discuss specific problems encountered in the field or just keep in touch.

One of the best compliments we ever got was after a PV 101 class, when one of the students commented how much the class had enabled him to “take his business to the next level and grow with the future.” Back then, the gentlemen had just started a small PV installation business he was operating out of a garage.

While in class, he connected with an electrical engineer, and both of them soon found out they had similar ideas about what they wanted to pursue.

Today, they conduct a successful installation business and employ around a dozen people — proof positive that training does work. SPW

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10/23/12 11:59 AM

[RACKING

an d

m o u n t ing ]

Generator Jailbreak Racking company engineers system for high wind loads at Alcatraz

From 1934 to 1963, the Alcatraz Federal Penitentiary was the preeminent prison of the United States. Indeed, it was declared inescapable.

Surrounded by the cold, rapid waters of the San Francisco Bay, a mile from the coast and outfitted with advanced security systems, officials believed that inmates would never escape its concrete walls — at least not alive.

Five inmates, however, did escape. Their whereabouts remain unknown, and officially they are presumed drowned.

But a tourist, as he crosses the bay on a ferry from Fisherman’s Wharf, might consider an alternate ending. He looks up at the prison and down at the bay. He considers the water

Alcatraz Solar Installation: Roof Height: 40 feet Installation: 9/2011 to 6/2012 Product: SunLink RMS Entities Involved: About 10 System Size: 307 KW Number of Panels: 959 Module: SunPower

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temperature and the distance to the coast.

He thinks he could make it.

What’s important to the National Park Service is that, in this moment of wonder, he does not think about solar power. But as he and a million other tourists step foot onto Alcatraz Island this year, they are visiting a 100-year-old structure that is powered in part by a solar array. Only a lighthouse offers a view of the 959 SunPower panels on the cell-house roof, and officials say that’s the way it should be.

“Because Alcatraz is a historic landmark, we couldn’t alter that by putting on this massive installation of solar panels that were visible, even from the city,” says Alexandra Picavet, a spokesperson for the park service’s Golden Gate National Recreation Area. “All of the solar panels are below the parapet wall.”

That may sound simple enough. Just put the panels below the parapet wall. But when it came to the racking, engineering challenges came from two directions:

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environmental conditions — primarily the wind, which also contained corrosive salt — and the historical integrity of the building.

SunLink, a Bay Area balance-ofsystem components provider that prides itself on its ability to solve difficult engineering problems, was brought in to design the racking. The company had worked on other high-profile landmarks — Google headquarters, the San Francisco International Airport and the Atlantic City Convention Center — but nothing quite as well known as Alcatraz.

The prison sits high in the middle of a bay. The wind sweeps in from the Pacific Ocean, funnels through the steel beams of the Golden Gate Bridge and shoots directly at “The Rock.” “In engineering wind parlance, it’s in what’s called an ‘Exposure D,’” says SunLink CEO Chris Tilley. Wind exposure category D is a designation for areas that face the highest wind loads.

The prison roof reaches heights of 40 feet and experiences a wind load similar to a coastal lighthouse. Leaning on extensive research and development, SunLink went to work developing the best system for the former prison.

This wasn’t the first time the park service had tried to install solar on 24

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m o u n t ing ]

Alcatraz, according to the National Renewable Energy Laboratory, which collaborated on the solar projects then and now. In the 1990s, contractors had installed some mounting before a group protested the array, which would have been on the industries building, a place where Al Capone ran a sewing machine and Machine Gun Kelly did the laundry.

The protesters said the installation would be visible.

When funds became available through the American Recovery and Reinvestment Act, the $3.6 million project got a second chance. The park service and NREL sought to put a 307KW installation on the roof of the cell house. The electricity would run into 2,000-amp-hour battery strings (storing power for cloudy days) and supplanting energy created on the island by a pollution-spewing diesel generator. The island is not connected to the mainland for power, which a misplaced anchor took care of decades ago.

But in addition to challenges with wind and visibility, the cell house itself has quirks. It’s an ancient concrete structure that wasn’t built with the same building codes used today.

“When you put a solar system on a building like that, you need to make

sure you’re not damaging it in any way,” Tilley says. “Understanding what the materials are and how to attach from an engineering point of view — all of those things can be calculated based on tests or other things to make sure there won’t be a problem with the building.”

The company used its SunLink RMS mounting system as a base product, one which Tilley says has been extensively tested in wind tunnels and is made from aluminum and stainless steel. It also mounts panels at 5, 10, 15 and 20 degrees. At the time of the installation, RMS was SunLink’s primary product. The company now distributes Core RMS for tilts less than 10 degrees and in extreme conditions, and Precision RMS, with feet that adjust on-site to accommodate rooftop anomalies, enhancing the company’s ability to install at irregular sites.

Tilley says that each SunLink installation is specific to the project, though, because of the interchangeable components in each system. “You may have a strong link in one place because you really need it for this project, but the basic geometry of the system is the same,” he explains.

But the solution for Alcatraz also required custom components, which

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differentiates it from nearly all of SunLink’s previous installations. One such custom piece was the lateral link, which connects subsegments of an array. Because the park service wanted a certain size system on the roof, nearly all the available roof space had to be used to place solar panels. This custom lateral link allowed SunLink to maintain the structural integrity of the system and make it stronger, while installing over deep drainage crickets that installers would normally avoid.

“One of the key aspects of SunLink’s approach to designing mounting systems is trying to keep everything strongly interconnected,” Tilley says.

“The more interconnected a system can be — and by that I mean structural components going north, south, east and west — the better you can deal with loads.” The design is rated for high wind speeds that will both push and pull on the system.

The system also used customized short connector posts to keep a low profile and resolve waterproofing issues specific to the site. Special flashing and waterproof foot boxes were also used on the rooftop. Finally, the company chose a combination of 5- and 15-degree tilt angles to ensure the system was out 26

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of sight while maximizing efficiency in relation to roof slope.

After the mechanical matters were sorted out and the design was approved, it was simply a matter of planning — but it was not simple. Bryan Bucci, who was a project manager and now works in marketing for SunLink, was charged with coordinating all logistical components associated with the project.

“This was a huge project,” he says.

“When it was handed to me, I had to take a breath and be like, ‘All right’ — sort of get fired up for it.”

Bucci broke the project down to a daily plan. He set goals and kept priorities. He documented every e-mail and phone call. He organized weekly conference calls with a dozen of the system’s stakeholders. He says these things were essentially his role with any installation as a project manager, but Alcatraz required more.

With installation beginning in September 2011 and ending in June,

a barge — not the normal ferry — was required to transport the materials to the island. All the skids, pallets, boxes of metal and aluminum, combiner boxes and inverters then had to be craned to the roof, where the installation was staged.

The installers, who were not affiliated with SunLink, often arrived in the early morning, sometimes before sunlight and as fog obscured the bay. The wind was fierce, and workers sometimes had to tape their helmets to their heads.

Their fingers were nearly frozen from the morning chill. But they got the work done and were often leaving the island just as the first visitors arrived.

A sign that said solar was being installed greeted visitors as they arrived.

No one could see the project, though.

And today, the solar system is collecting energy and cutting down on the costly diesel generator’s use by 60%.

“This is fantastic for us because we’re a Bay Area company,” says Tilley. “It’s great for our employees to go across the Golden Gate Bridge and look down over there and know that’s one of our projects.” SPW

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10/25/12 10:49 AM

Solar FlexRack_9-12.indd 27

10/23/12 12:02 PM

Despite its (false) reputation, solar is completely compatible with a free-market economy.

Illustration: istockphoto.com

By Michael Gorton and Dan Bedell

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9 • 2012

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10/24/12 8:17 AM

The Capitalist Ca$e for Solar (For the purpose of this paper, it is assumed that that grid parity will occur when solar panels can be produced for under $0.70/watt with a total system cost under $2/watt.)

With solar costs on a strong decline, this clean renewable energy has emerged as a viable power partner for generating costeffective peak electricity generation was 4,361 billion kWh gross, with annual electricity demand projected to increase to 5,000 billion kWh 1 by 2030.

According to Energy Information Administration (EIA) data, 42% of the nation’s electricity is generated from coal-fired plants, 25% from natural gas, 19% nuclear and 6.5% from hydroelectric.

This paper examines the recent past and potential future of photovoltaic (PV) solar in terms of how it has compared with traditional generation and how, even without government subsidies, solar utility-scale projects will reach a price per KWh that will be at — or less than — traditional generation, possibly as soon as 2014.

Now is the time for traditional conservative thinking to reexamine the facts about solar energy and explore its potential for 11 • 2012

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EN GINE E RING TE CHNOL O G Y DE V E L O P ME NT S

not only delivering more efficient and less costly power, but also for creating jobs and opportunities that jump-start economic growth.

This jump-start would be possible because electricity drives almost every part of the economy, and cheap abundant electricity keeps industry competitive.

Clean, Abundant And Renewable Photovoltaic solar essentially is made from one of the Earth’s most abundant resources: silicon. Of the 92 elements found on the periodic table, silicon (Si) is the Earth’s most prevalent semiconductor — and second most common element of any kind, after oxygen. Appearing in silicon oxides such as sand (silica), quartz, rock crystal, amethyst, agate, flint, jasper and opal, silicon makes up about a quarter, by weight, of the Earth’s crust.2 Furthermore, the fuel source is free (presuming the sun rises).

As for cost, in response to growing demand for renewable energy sources, the manufacturing of solar cells and photovoltaic arrays has advanced considerably in recent years. With continued advances in technology and increases in manufacturing scale and sophistication, the cost of PV will continue

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11 • 2012

to decline steadily, resulting in competitive electricity in a growing number of regions.

The annual exponential drops in the cost of solar will not only result in competitive electricity, but also in cheaper electricity coupled with higher profit (the hallmark of any successful capitalist system, of course).

Solar PV vs. Concentrated Solar Concentrated photovoltaic (CPV) technology

uses optical devices such as lenses to concentrate large amounts of sunlight onto small areas of solar photovoltaic materials to generate electricity. This was viable when PV was expensive and plastic lenses were cheap.

As this paper demonstrates, PV is now lowcost, so CPV is less important.

CSP simply uses concentrated sunlight to heat steam, which drives a turbine. At one point in time, CSP was less expensive than PV. This has not been the case for several years. Not only does CSP have all of the moving parts of traditional generation, thousands of mirrors must also track the sun accurately on a daily basis. The expense of these components alone, coupled with the failure rates, defeats the value of potential saving from heat storage and CSP’s ability to generate for periods after the sun has set.

For many years, solar power was not a viable alternative source of energy, but the cost of PV went down year after year just as electricity costs rose.

From 2005 to 2008, the cost of PV rose and maintained this level in response to significant transitions in the industry.

Substantial volumes of solar parks were being constructed in response to the 2004 revisions to the feed-in tariffs in Germany, which created demand for materials on a large scale

www.solarpowerworldonline.com

10/24/12 8:26 AM

to meet demands of solar farms.

During this time the silicon industry, which had previously produced materials for the microchip manufacturers, adapted and began refinements that would ultimately drive a new trend line in decreasing PV costs.

To understand this, one need only to realize that microchips are small, while solar farms are huge.

For the past eight years, silicon manufacturers have been developing new methods of mass production on a scale that is (potentially) orders of magnitude greater than historical demand, while simultaneously developing efficiencies to dramatically lower costs.

This number is based on the total cost of a system and financing large-scale projects using the same methods for financing a new combined cycle gas-powered generating

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EN GINE E RING TE CHNOL O G Y DE V E L O P ME NT S

Michael Gorton, Chief Executive Officer and Chairman of Principal Solar, is an entrepreneur, mentor and company builder, applying proven strategies in the fields of renewable energy, telecommunications, music and healthcare.

Drawing on his extensive business expertise, scientific education and training, Gorton serves as a strong voice and proponent of solar power.

Dan Bedell is Executive Vice President of Corporate Development for Principal Solar.

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facility. Referring to the previous chart, we can see that in 2010 PV was approaching $2/ watt.

2012-2014: Solar PV’s Big Leap Forward In early 2012, solar PV began to approach grid parity, and it’s almost there. In looking at the spot market price for PV from 2009-2012, note the same downward trend in cost for PV in Germany, China and Japan.

Because China has cheaper labor, it’s understandable that this labor-intensive industry produces lower-cost products in China than in Japan and Germany.

The chart above shows the May 2012 spot price of (Chinese) PV to be $0.91 per watt.

From this trend line, it can be extrapolated that in the next two years, assuming a continuing trend, solar PV may reach $0.70/ kWh by 2013 and could be as low as $0.50/ kWh by 2014.

These numbers are supported by many of the largest solar cell and PV manufacturers.

The projected 2014 price will make solar PV not only competitive with — but less expensive than — nuclear, coal and natural gas.

11 • 2012

Cost Analysis: Apples To Apples Here’s a look at a 2009 MIT study3 that evaluated the resulting cost per kWh of new plants that would be constructed in 2009. For this analysis, the cost per kWh (green) of solar built in the same period has been added to the chart. For 2009, clearly the cost of electricity from a new construction nuclear, coal and natural gas plant produces lower electricity rates than solar PV. In 2014, solar and natural gas are level, and coal costs less, although a coal plant will probably cost more to build than it did five years earlier in 2009.

From these projections, it can be concluded that 2014 is the year that solar may reach parity with the Big Three. Solar could cost half as much as its competitors by 2020.

Perfect Energy Partners: Solar & Natural Gas Rooftop solar is unlikely to become a truly viable form of energy for individual homeowners. It’s similar to making bread. A wheat farmer in Kansas grows, harvests and sells the wheat to a co-op. The co-op sells it to a transportation company that takes it to a flour grinder. A baker buys the flour from a middleman, bakes bread and sells the bread to a grocery store. Consumers buy it and get more consistent and less expensive bread than if they grew wheat in their back yard.

Even though consumers can grow gardens, it doesn’t compare to producing energy by rooftop solar panels.

The sun sets. Some days are cloudy. Mother Nature and

www.solarpowerworldonline.com

10/24/12 8:27 AM

the elements conspire to destroy panels and their inversion or mounting equipment.

Everyone needs a reliable source of back-up energy from a power company.

Most people will agree that producing electricity is more complicated than bringing bread to the market. Too much rooftop solar will change the economics of grid power.

Put simply: If everyone had solar, the power companies would sell a lot less. When they sell a lot less, the price will go up. Today, the world relies upon the power companies to provide reliable power at a reasonable price.

One more important point is that solar only generates when the sun is shining.

Backup is critical for any solar installation.

Nuclear and coal produce baseload power. They need to run 24 hours a day.

When a nuclear or coal plant is shut down, it takes hours and even days to restart. Natural gas, on the other hand, can start in minutes.

For this reason, solar and natural gas work well together compared with nuclear power and coal. Many calculations and approximations have been made on how many years supply of natural gas we currently have. Clearly, using solar as a supplement to natural gas will extend that supply.

On the other hand, the Achilles heel of earth-based solar will always be access to sunlight. Because of this, many experts have

suggested battery and storage methods. The best backup system is already on the grid in the form of natural gas and combined-cycle generation.

LOOKING AHEAD In the final analysis, solar must be able to compete on an even playing field without subsidies. Based on the projections shown in this paper, that should happen in the coming years. A solid capitalist foundation will be the primary factor driving the coming “gold rush” in solar development. It is simply icing on the cake that solar energy is a carbonfree domestic energy source that is widely available.

Unused land throughout the desert southwest represents an abundant natural resource of energy. More precisely, one county in west Texas sees enough sunshine to provide the entire electricity needs of the United States for the next 50 years.

Still, it’s not likely that solar will provide much more than 15% of the total grid power.

There are many reasons for this, almost all of which relate to the reliability of the grid.

Solar PV has experienced exponential cost drops year-after-year for more than 30 years, with projections putting PV module costs at $0.50/watt, total system costs under $2/watt and output electricity at just under 6 cents per kWh — grid parity — in 2014. In the next three years, this nation will see a www.solarpowerworldonline.com

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dramatic rise in utility-scale solar production that will support the existing infrastructure.

Many will compare the next few years to a gold rush, as billions of dollars are made from converting sunlight to electricity.

If America continues or expands a carbonregulated market, solar will fill the bill with no fuel costs, low maintenance and carbon credits rather than carbon costs when compared to coal, nuclear and gas-fired power plants.

Again, it is important to note that solar will not replace the Big Three, but it will add to the diversity of the nation’s power grid, easing congestion in energy-stressed grids and providing affordable power. Most importantly, it should produce electricity at a price that is equal to or lower than its competitors. SPW ENDNOTES 1 World Nuclear Organization; Nuclear Power in the USA; http://www.world-nuclear.org/info/inf41. html; accessed May 25, 2012.

2 Solar World; Energy for you and me; How we make solar panels to capture the power of the sun; http://www.solarworld-usa. com/aboutsolarworld/~/media/Global/PDFs/solar-101.ashx; accessed May 31, 2012.

3 Deutch, John M. et al; Update of the MIT 2003 Future of Nuclear Power; Massachusetts Institute of Technology; 2009; http:// web.mit.edu/ nuclearpower/pdf/nuclearpower-update2009.pdf; accessed May 25, 2012.

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SEIA and Vote Solar Rank The Top Commercial Solar Customers in the United States

Solar Means Business W

hat do Walmart, Costco, IKEA, McGraw Hill, Johnson & Johnson and FedEx have in common?

They know a smart investment when they see one, and all are adopting solar energy wholeheartedly.

From large corporations to small businesses, U.S. companies are installing solar energy to control energy costs and improve bottom lines. As of mid-2012, businesses as well as non-profit organizations and governments across the United States have deployed more than 2,300 MW of photovoltaic systems on more than 24,000 individual facilities — and this number is growing rapidly. During the first half of 2012, over 3,600 non-residential PV systems came online, an average of one every 72 minutes.2 The rapidly falling cost of solar energy has made solar an increasingly appealing investment for American businesses. Between the second quarter of 2011 and the second quarter of 2012, the average price of a completed commercial PV system fell by nearly 14%.3 The economics of PV have become so attractive that many of the best managed corporations, which are synonymous with low cost and efficiency, are adopting solar energy on a massive scale across the United States.

This report, prepared by the Solar Energy Industries Association (SEIA) and the Vote Solar Initiative (Vote Solar), highlights those companies that have deployed the most solar energy capacity at their facilities for onsite consumption. In total, the 42 companies analyzed for this report have deployed at least 321 MW of PV capacity at more than 750 locations in at least 26 states and Puerto Rico. The 20 companies with the highest installed capacity have deployed at

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least 279 MW, enough to supply the electricity needs of 46,500 American households. These solar leaders include some of America’s most iconic brands and biggest businesses.

In addition to installed capacity, this report also ranks companies by the number of operating installations as well as the geographic diversity of their solar deployment.

Solar Value Proposition Energy can make up a significant portion of a business’s operating costs. Companies are installing solar at record rates because it reduces operational expenses, improves their bottom lines and allows them to focus resources on their core business strategies.

The price of solar-energy systems has dropped rapidly over the past 5 years. In

some places, it is more cost-effective to deploy solar than buy electricity from the local utility. No matter where the company is located, solar provides predictably priced electricity for 20 to 30 years. This hedge against utility price volatility is highly valuable to businesses that are focused on managing long-term budgets. Combined with innovative financing options that further reduce upfront costs, solar has a new value proposition that makes business sense for major companies nationwide.

Companies across the country have made enormous investments in solar to manage their operating costs. The list at left ranks the Top 20 of these companies by the installed capacity of all of their onsite solar installations.

Some companies have high energy demand at a single facility and build one or two large systems to meet that need.

Others have dozens or hundreds of stores and facilities that could benefit from solar.

The rankings (opposite, below) list the Top 20 companies by the number of solar installations at company locations. Those at the top of this list have made repeated decisions to go solar, building off of earlier successes.

Solar Leaders by Percent of Stores The data demonstrates the percentage of

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SIKO is specialized in position feedback and offers a wide range of encoders for sun tracking systems.

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Macy’s 5%

COSTCO 14%

IKEA 79% REI 20% Kohl’s 11%

Solar Leaders by Percent of Stores The data at left demonstrates the percentage of U.S. company stores with solar for a few notable companies. It is not a full ranking, but rather a comparison between some of the top solar users that were already part of this report’s analysis. It should be noted that smaller companies could well have solar at all of their company locations or could even be net exporters to the grid, meaning companies generate more solar energy onsite than is consumed by their facility.

U.S. company stores with solar for a few notable companies. It is not a full ranking, but a comparison between some of the top solar users that were already part of this report’s analysis. It should be noted that smaller companies could well have solar at all of their company locations or could even be net exporters to the grid, meaning companies generate more solar energy onsite than is consumed by their facility.

Top Companies by Geographic Diversity While companies with facilities in California and the Southwest have certainly taken advantage of the ample solar resources and effective solar policies, corporations have gone beyond those well-known solar markets with installations all across the country. Many corporations have solar energy systems in diverse states including Michigan, Wisconsin and Massachusetts, which is a strong indication that solar energy can make business sense in all U.S. climates.

This list (above) ranks the top companies by the number of states in which they have deployed PV at their facilities.

Big Plans The companies ranked here and many more continue to expand their investments in solar energy at a rapid pace. Companies such as Apple, which has a 20-MW system under construction at a datacenter in North Carolina, have announced plans for major solar deployment. Others such as General Motors have decided to enter the solar business themselves.

Businesses as well as other large energy consumers like nonprofits, schools and public agencies are expected to add 7,000 MW of additional PV systems over the next five years. That’s enough to replace seven retiring coal power plants. SPW

The electroceramic material coats parts in about six steps. Conventional coatings require as many as 16.

Study Methodology

The Solar Energy Industries Association (SEIA) and the Vote Solar Initiative (Vote Solar) set out to rank the top corporate users of solar energy in the United States. To do this, SEIA and Vote Solar combed public databases and contacted company representatives to collect data on their use of PV systems.

While researchers made every effort to collect detailed, complete and accurate data, not every company responded to surveys, and public databases do not capture all installations.

Furthermore, new systems are installed every day.

In the first half of 2012 alone, more than 3,600 individual non-residential systems came online in the United States. Ultimately, SEIA and Vote Solar believe this is an accurate portrayal of the leading corporate users of solar energy in the United States but reserve the right to make adjustments as new data becomes available.

SEIA and Vote Solar only counted on-site PV systems that supplied power directly to company facilities. This does not include utility PV power plants that sell wholesale electricity. While some companies buy solar renewable energy credits (SRECs) from solar power generated off-site, this report does not consider such transactions because of the limitations in data collection and verification.

Likewise, SRECs produced by many onsite PV systems are sold to utilities or other buyers, while companies that sell their SRECs do not retain the environmental attributes of the system, such systems are still counted for the purposes of this report as the decision to deploy an onsite solar system is an essential step in solar energy development.

Many important companies have made massive investments in helping others go solar. Bank of America, Merrill Lynch, Google and others have provided billions of dollars in financing for solar energy systems in the United States. While these investments are big business and central to the development of the solar energy industry, they are not the focus of this report. These rankings only include PV systems that were operational as of mid-August 2012.

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W Josh Ch ien /Sr. Director of N ew Product In tro du c ti o n at S an mi n a-S C I

>

W

ith volatile demand for solar

energy products across the world, successfully bringing a solar

product from concept to reliable volume production is one of the

solar industry’s biggest challenges. The drumbeat to make the product cost less by using fewer parts and materials, design it so it assembles in half the time, fabricate and

assemble it anywhere and everywhere places pressure in an industry that is faced with potential commoditization.

Going into volume production on a global basis means

leveraging the assets and expertise of a manufacturing partner when your company doesn’t have the in-house capability and capacity and resources. Market forces require a new approach and mindset to meet time to market and competitive pressures.

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Design is Job 1 A study by Ford Motor Co. showed that although product design non-recurring engineering (NRE) and development comprise only about 5% of the product cost, design can influence the final cost up to 70%, whereas the combination of materials, labor and overhead together only influence the remaining 30%. The most effective way to manage quality and cost is to start with the product’s design.

When you look at the different elements of a solar product’s life cycle, there are many challenges:

• Product design issues such as:

1) Energy collector obstacles with optics alignment and silicon quality; 2) Designing efficiency into Balance of Systems (BOS) — mechanical support

structures, inverters, control systems, etc.

• Manufacturability issues such as element proofing and coating (i.e. plating) large support structures; • Parts fabrication process selection — e.g. cold forging vs. machining of complex high-precision components, sand casting vs. pressure casting, stamping vs. forging, etc.; • Sourcing and supplier fit — assuming the supplier can handle prototypes well, will they also be able to handle scale and sizing? (i.e. equipment, process); • Deployment and launch challenges, i.e. documentation in multiple languages, organizing multiple sites, orchestrating material delivery and fulfillment worldwide, completing regulatory requirements (to just name a few); and • Volume scaling and global production.

Of all the elements, design represents the greatest opportunity for cost reduction and quality improvement in each one of these areas.

The Value Chain Solving these dilemmas is the raison d’être of the value chain — the entire team of people who are responsible for ensuring the product gets to market. This includes design engineers, manufacturing engineers, quality engineers, logistics specialists, procurement specialists, test engineering, assemblers, machinists, inspectors, application engineers, sales reps, financial analysts, supply-chain managers, marketing managers — and that’s not even a complete list. Each of them has a role to play in the success of the product, and each can contribute (to a greater or less degree) at various stages to reducing costs,

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increasing quality and speeding the delivery of the product. The key to success is getting them all involved, right at the start, when the product is in the concept stage.

The product’s design process significantly affects each of the value chain members’ functions. As an example, instead of designing a BOS’s 20-foot structural member which requires hot-dipped galvanization — where only a handful of

suppliers have large enough plating tanks that can handle such a size (based on the findings from the manufacturing engineers, quality engineers, procurement specialists and supply-chain managers) — why not design modular structures where many suppliers and plating contractors anywhere can easily perform the task? With the value chain’s involvement in this particular example, significant savings would have been

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realized in the form of lower costs, quicker turnaround and at higher quality before significant investments in manufacturing lines and materials had been made.

Involving the value chain early and often in the product’s design and development yields extraordinary savings over the product’s life cycle. The cost to correct design errors increases by a factor of 10 at each step of the process. A $1 design error found during concept development could easily reach $1,000 during rapid prototyping, or tens of thousands of dollars during NPI, even reaching hundreds of thousands of dollars during volume production. In addition, each engineering change order, once actual tools and materials are involved, will significantly delay market entry.

ain Involving the value ch early and often in the product’s design and

Here are the most important factors I recommend for consideration when planning on ramping a product to volume globally:

development yields over extraordinary savings . the product’s life cycle

• Integrate Design for Manufacturability (DFM) and Value Analysis / Value Engineering (VAVE) into the productdevelopment process.

Waiting until after a product’s design is “finalized” before incorporating design for manufacturability (DFM) will often result in discovering it can’t be manufactured at the realistic targeted cost, volume, location or schedule that was planned. To reduce time to market and avoid unnecessary costs and constraints, run DFM/VAVE in parallel with product design. When run in parallel, these processes simplify the design and provide alternative material and manufacturing process choices, thus getting the product to market faster while improving the bottom line.

Each design has its own challenges and opportunities. For example: • Most mechanical systems, such as BOS for CPVs, can be simplified with minor modifications such as incorporating multiple brackets into main structures, resulting in better material use by incorporating modular designs and benefiting from common tooling and fixturing.

• Large enclosure assemblies can be redesigned so they are fabricated from fewer pieces of metal—resulting in lower material costs and less weight, while also making them less costly to transport. Or designing a CPV module grid that can fold on itself and take up less space during transport and installation.

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• Consider modularity and DFMA (design for manufacturing and assembly) principles for simplification such as using standard tooling to reduce cost.

• Perform cost modeling before the prototype phase Cost modeling goes beyond just parts acquisition and manufacturing and takes into consideration assembly techniques, different supply chain strategies, logistics and transportation paths/strategies.

Cost elements dynamically change as a function of location, materials, transport, and assembly techniques. Access to cost standards is a primary key to accurately modeling the final production unit cost and, therefore, the price.

The value chain is intrinsically involved with all the elements related to costing and has mastered the capability of preserving margins using efficient and cost-effective supply-chain strategies. They have the tools, resources, knowledge and expertise to simulate and validate the cost of the product from concept to volume production.

And given the physical size of many solar products, such as CPV, thin film, or CSP (concentrating solar power – thermal), it is also best to review material availability and logistics early on to avoid inherent costs.

In addition to cost reduction across all elements, product simplifications typically yield even greater savings. Fewer mechanical parts, and consolidated sub-assemblies, will mean lower product cost, more efficient transportation, less weight and less fuel consumption as a function of volume.

• Integrate Design for Reliability (DFR) at the earliest design stages Since most solar products are exposed to extremely harsh environmental conditions and still expected to operate at peak efficiency at all times, their reliability is paramount.

Building prototypes and physically testing them under the same environmental conditions and usage where they will be installed, is a crucial phase of DFR. The right tools, equipment and experts are needed

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to conduct those tests and to interpret the results accurately. In most cases, the value chain has either the testing capability in house, or a proven track record of dealing with experts for the specific subject matter.

Including automation in various fabrication processes, such as assembly and optics calibration, also plays a crucial role in delivering consistent product performance in the field. An example would be welding leads instead of soldering to power leads to eliminate soldered-joins failures in the field because of large temperature cycles.

Automation starts at the prototype stage. To take advantage of automation as cost-efficiently as possible means designing the manufacturing process at the earliest stage in product design.

Doing so results in a more secure manufacturing process where the equipment is already identified and sourced, the skill-set is readily available and the learning cycle is completed.

geopolitical obstacles, plugging fulfillment gaps — all of which can be minimized when the value chain has been involved from the beginning of the product’s design.

Taking advantage of the value chain’s engineering ecosystem lets the manufacturing roadmap be created early on, so it can be continuously updated and improved before flipping the switch to volume. Consequently, design, engineering, manufacturing, supply chain and logistics problems or issues are ironed out early enough to yield significant product life cycle savings in costs and — scaling to volume becomes relatively seamless. SPW

Chien is responsible for leading the New Product Introduction (NPI) Advanced Manufacturing solutions on behalf of Sanmina-SCI.

Scaling Up to Volume Production

To become viable products in the market, most solar products are destined for large volume manufacturing. Their scalability is inextricably intertwined with their design and strategic supply chain.

Specific product requirements, coupled with supply and material constraints for solar products, means that the top global solar industry leaders are running DFM, DFR and cost-modeling processes in parallel with their product design.

Fully using the global capabilities and local support systems of your value chain is the safest way to securely scale up volume production, especially because the solar industry supply chain is complex (solar cells, tracking technology, inverters, control systems, power storage and transmission, BOS).

Accordingly, New Product Introduction (NPI) processes must be well-defined to avoid launch and scaling issues such as preventing shortages, mitigating equipment limitations, overcoming

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

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frequency of the carrier waveform is called the modulation frequency. To generate more precise sinusoidal AC voltage waveforms and keeping the size of the LC filter small, highmodulation frequencies are generally used.

There are many industrial standards that control the noise and harmonic contents in an inverter system, such as AC motor drives, Uninterrupted Power Supplies (UPS) or other AC power applications. In the case of grid-tied PV inverters, the Institute of Electrical and Electronics Engineers (IEEE) 1547, Underwriters Laboratories (UL) 1741 and FCC Part 15B standards specify the

guidelines to control the harmonic contents of the output current and the Electro Magnetic Interference (EMI) generation in the inverter. The guidelines guarantee that: * The inverters do not generate excessive noise and harmonics, which can contaminate the AC grid voltage. * The inverters are immune to electrical and magnetic noise from other sources and provide reliable operation in an environment of high electromagnetic noise. * The inverters do not generate unwanted radiated or conducted noise, which can disturb the stable operation of

other equipment coupled either electrically or magnetically.

Most of the PV inverters manufactured in the United States are designed to meet UL 1741 and IEEE 1547 standards. As the capacity of PV generation in power distribution systems grows, utility companies become increasingly concerned that the noise and harmonics from the PV inverter systems will adversely affect the power quality or affect the operation of other equipment and cause it to malfunction or otherwise disrupt the stable operation of the power distribution system.

This article lists the possible sources of the harmonics and switching noise generated by the PV inverter and describes how they can be controlled to meet customer requirements and relevant industrial standards. The information in this article can be used to understand the harmonics and EMI issues in a variety of inverter systems.

PV Inverter System Configuration Figure 2 shows the block diagram of a Solectria PVI 82-KW inverter, including the filters used for attenuating the high frequency noise on the inverter output voltages and currents. There are two main sources of high-frequency noise generated by the PWM inverters. The first one is the

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PWM modulation frequency (2 to around 20 kHz). This component is mainly attenuated by the LC filter and the transformer. The second source originates in the switching transients of the power electronics switching devices (IGBTs). The frequency of the switching transients is dependent on the device switching characteristics, gatedrive circuit and the snubber circuit in the inverter. It ranges from several 100 kHz to 100 MHz. The series filter and the shunt filter are designed to attenuate the frequency components caused by these switching transients and also the harmonics from other subsystem components such as the switched mode power supply (SMPS) and other inverter control circuitry.

Figure 2 also shows the voltage and current waveforms in each stage of the inverter. Most of the harmonic components in the voltage and current waveforms are filtered out by the LC, series and shunt filters. The inverter output current is in phase with the voltage (unity power factor), and the total harmonic distortion (THD) is less than 5% at rated operation, which is far better than the current THD of most industrial loads and is comparable to the output current waveforms of an Uninterruptable Power Supply (UPS).

PWM frequency and LC filter An LC filter is used to attenuate the PWM modulation frequency and its harmonics in the inverter system. The leakage inductance of the integrated isolation transformer further attenuates the high frequency component so that the output current will be sinusoidal and meet the desired THD limit.

A symmetrical PWM scheme is generally preferred to reduce the ripple in the inverter output current. A symmetrical PWM scheme compared to an asymmetrical PWM reduces the effective peak-to-peak ripple current by half when using the same switching frequency.

As shown in Figure 2, the inverter’s power stage output voltage waveform is composed of a series of square waveforms and includes high-frequency components.

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and sinusoidal as the inverter output current flows into the inductor in which it cannot change instantaneously.

Figure 3 compares the power stage output to the inverter output current. In the time domain, the waveforms do not look different.

However, the Fast Fourier Transformation (FFT) results show that the inverter current after the LC filter has much less highfrequency components than the unfiltered power-stage output current.

This filtering effect can be illustrated in a Bode Plot. Figure 4 (a) shows the LC filter frequency characteristics using the theoretical frequency analysis and the measured harmonic components with a frequency analyzer when the inverter operates at full power. In the example, the LC filter resonant frequency is tuned to 750 Hz. Assuming a PWM modulation frequency of 10 kHz it would be attenuated to 45dB below the fundamental current component.

The actual inverter output current FFT result shows that the 10 kHz ripple component is further attenuated to 60dB below the fundamental component by the shunt filter, which is about 0.1% of the fundamental 60Hz current. Figure 4 (b) shows that all the 4 8 SOLAR POWER WORLD

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harmonic component frequencies are well controlled and the overall THD is 2.31%.

High-frequency noise generated by switching transients When the switching devices are turned on and off, high dv/dt and di/dt cause oscillations during the transients, which contain high frequency noise in the range of 100 kHz or higher. Figure 5 shows the switching transients of the IGBT voltage and current with two different gate drive circuit designs.

By using a slow switching transient (a), the oscillation can be minimized but switching losses are increasing because of longer operation of IGBTs in the active region. With a faster switching speed, the switching losses can be kept lower but oscillations in voltage and current are being generated because of the parasitic inductance and capacitance in the inverter stack.

This high-frequency oscillation falls into the frequency band regulated by FCC. To increase the overall efficiency of the inverter and at the same time to minimize EMI, the IGBT switching speed and noise-filter design must be carefully coordinated.

There are other sources of switching noise in the inverter system caused by the Switch Mode Power Supplies (SMPS) and the digital control logic circuits. The noise from these components can reduce the system performance by contaminating internal analog feedback signals, resulting in logic level or communication errors and could also cause EMI interference with the outside world.

The high frequency noise can be further classified into radiated noise and conducted noise. The radiated noise can be controlled at the board level and at the system level in many ways such as shielding, component layout, wiring routing and signal grouping.

The conducted noise can be controlled by grounding or the use of proper filters, carefully designed to eliminate specific frequency components. In Solectria’s PVI 82-KW inverter, excellent noise levels were achieved by implementing a robust printed circuit board (PCB) layout in combination with hardware and software filters. Noise in signal circuits is solely controlled by ferrite beads and proper grounding. The PVI 82KW inverter also features series and shunt filters in the final output stage of the system.

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These filters are frequency-band limiting and designed to filter out switching frequency transients.

Series Filter The IGBT switching transients normally last 0.1 to around 10 usec, so the filter should be tuned to between 100 kHz and several MHz. Also, the controller uses a SMPS switched at 150 kHz. The series filter in the PVI 82 KW attenuates both common-mode and differential-mode noise. It provides 80dB common-mode attenuation for the frequencies between 100 kHz and 1 MHz, and 70dB differential mode attenuation for the frequencies between 200 kHz and 3 MHz. The filter is selected to eliminate the system specific dominant frequency components and is not active in the lower PWM modulation frequency range.

Shunt Filter The selected shunt filter for the PVI 82KW inverter has a resonance point around 150 kHz and provides a reduction of noise interference particularly in the frequency range between 50 kHz and 5 MHz. This filter is added to further reduce the switching noise from the power stage as well as from the switch-mode power supply in the inverter control system. The shunt filter also provides a protection circuit against surges of atmospheric origin to the grid, typically caused by lightning and characterized by high current levels of short duration. The filter reacts in a few microseconds to current spikes of a few kA and protects the system against impulse surges of up to 1000 volts.

Harmonics Generated by Firmware Control Conventional PV inverters’ firmware runs at least two nested control loops. One is the AC current control loop to control the inverteroutput current, purely sinusoidal and in phase with the grid voltage, generating active power. The other is the DC voltage control loop in conjunction with a Maximum Power Point Tracking (MPPT) algorithm to most efficiently harvest the DC power generated

by the solar panels.

When grid conditions The filtering of harmonics and change because of powergrid transients, powerEMI needs to be carefully line faults or load-based voltage fluctuations in designed to maintain the control the distribution line, the inverter-output current bandwidth of the inverter and is controlled to balance the power transfer from to provide clean and reliable the PV array to the grid. If the current control loop control signals. gains are tuned properly, the dynamic response because of the transients can be controlled at the bandwidth usually less than 1 kHz. The DC introduced in this article. The filtering of voltage control loop is around the current harmonics and EMI needs to be carefully control loop and is usually controlled at designed to maintain the control bandwidth a lower sampling rate. If the DC voltage of the inverter and to provide clean and fluctuates because of sudden changes in reliable control signals in both analog and weather conditions, the DC voltage-control digital electronic circuits. SPW loop has a certain bandwidth to react and Michael Zuercher-Martinson, one of the four stabilize the system output. During sunlight founding partners of Solectria Renewables, transients, the system might generate even a leading photovoltaic (PV) inverter slower oscillations in the DC bus voltage manufacturer, located in Lawrence, Mass. and output AC currents control. Since the Mr. Zuercher is a distinguished electrical drive DC voltage-control loop bandwidth is low, it and power conversion innovator. Soonwook does not cause any harmonics or EMI issues.

Hong is the power systems engineering manager However, if the voltage-control loop were for Solectria. not tuned properly, the generation efficiency would decrease because of a failure to track the maximum power point of the PV panels.

Conclusion This article described how the current harmonics and EMI are controlled in PV inverters. IEEE 1547, UL 1741 and FCC Part 15B standards impose strong guidelines for grid-tied PV inverters to reduce current harmonics and eliminate electromagnetic noise. Extra attention is given by the PV inverter manufacturer to design inverters that are immune to EMI problems and guarantee reliable operation of the inverter in all worst-case operating conditions.

Different types of practical harmonics and noise reduction strategies for a commercial three-phase PV inverter were www.solarpowerworldonline.com

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Test

and

Verify Will your array stand up to heavy winds?

Here’s how you can find out.

This article is adapted from Rooftop Solar Arrays and Wind Loading: A Primer on Using Wind Tunnel Testing as a Basis for Code Compliant Design per ASCE 7 by Gregory Kopp, PhD, PEng, Joe Maffei, SE, PhD and Christopher Tilley, PE. 50 50

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A

s rooftop solar array deployment increases, assuring that building structures can withstand the additional loads is becoming a serious concern for structural engineers and building

officials responsible for reviewing and approving such systems.

To determine the loads on rooftop-mounted solar arrays, SunLink Corp. funded an extensive, multi-year test program at the Boundary Layer Wind Tunnel Laboratory at the University of Western Ontario and partnered with structural engineering firm Rutherford & Chekene to develop methodologies to appropriately apply the recorded wind loads to array structures in conformance with the International Building Code.

Code Requirements ASCE 7 does not provide specific guidance for the structural design of rooftop-mounted solar arrays, so engineers and building officials typically look to the ASCE 7 requirements for components and cladding. ASCE 7 provides three different methods for determining the design wind loads on buildings, and components and cladding. These methods and their applicability to design of rooftop-mounted solar arrays are discussed later on.

Method 1 and Method 2 ASCE 7 Method 1 (Simplified Procedure) and Method 2 (Analytical Procedure) provide prescriptive approaches for determining design wind pressures. These methods do not require experimental testing of the specific system being designed, but instead provide charts with design pressures derived from historical experimental testing of various types of roof components and cladding, none of which are similar in size, shape or configuration to solar arrays.

Typical practice has been to use Method 2 with arrays treated as a roof surface (e.g. using components and cladding coefficients for monoslope roof coefficients). There is no engineering basis for this approach, given that the aerodynamics of roof surfaces are typically different than those of typical solar arrays. However, research reveals that using Method 2 provides a safe and generally conservative estimation of the loads on arrays, particularly the loads over larger areas. However, when smaller tributary areas are considered, the code values appear to be less conservative and may, in certain cases, be liberal.

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EN GINE E RING DE V E LOP ME NT S

Computational Fluid Dynamics (CFD) CFD is an emerging discipline in wind engineering, and there has been substantial progress in the past number of years.

However, CFD is not currently in a state where it can be used reliably to estimate peak pressures on low-rise building roofs, let alone solar arrays on such buildings, and should not be used as a basis for design at this time. ASCE 7 does not currently allow it to be used as a design basis, and it would appear that CFD-based studies are a long way from being used to modify code formulations for component and cladding loads.

Method 3 Wind-tunnel testing per Method 3 provides an alternative for determining design loads for solar arrays. However, appropriately applying Method 3 is complex because there are few facilities in North America that can meet Method 3’s requirements, and because the cost, time and effort required to perform this type of testing for each specific PV project is often prohibitive.

Method 3 permits the use of wind-tunnel testing as the basis for design if the testing meets the following conditions: • The atmospheric boundary layer has been modeled to account for the variation of wind speed with regard to height.

• The relevant integral and micro-length scales for the longitudinal component of atmospheric turbulence are modeled to approximately the same scale as that used to model the building or structure.

• The modeled building and surrounding structures and topography are geometrically similar to their full-scale counterparts, except that, for low-rise buildings meeting the requirements of Section 6.5.1, tests shall be permitted for the modeled building in a single exposure site as defined in Section 6.5.6.3.

• The projected area of the modeled building or other structure and surroundings is less than 8% of the test section cross-sectional area.

• The longitudinal-pressure gradient in the wind-tunnel test section is accounted for.

• Reynolds number effects on pressures and forces are minimized.

• Response characteristics of the wind-tunnel instrumentation are consistent with the required measurements.

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Method Three in Practice Boundary Layer Wind Tunnels The Method 3 requirements listed above are only met at a few specially designed facilities in North America called Boundary Layer Wind Tunnels (BLWTs). Expensive to design, build, calibrate and maintain, BLWTs are used for the design of highrise buildings, long-span bridges and other complex structures where wind loading is a critical concern. While other types of wind tunnels provide useful information on things that move through the air, they are not appropriate for determining design wind loads on buildings and other structures.

The expertise needed to properly design and run experiments in these facilities is similarly specialized and limited. Proper BLWT modeling and testing must carefully follow the requirements as listed above, as well as those in ASCE Manuals and Reports on Engineering Practice No. 67, “Wind Tunnel Studies of Buildings and Structures.”

Scale One of the key challenges in designing wind-tunnel testing for rooftop solar arrays is scale. Because of the complexity of the flow field on a building rooftop, estimating or approximating this flow field is inappropriate for the purpose of determining design loads. To create the appropriate flow field, the building must be part of the model, included in the testing, and relatively small so as to not block more than 8 percent of the wind tunnel test section cross-sectional area. Because the modules are in turn small compared to the building, the actual array model on which measurements are taken is typically only 1:30.

Generalization Another key issue is site specificity. Many engineers are familiar with the use of wind-tunnel testing to capture particular characteristics of a building or site. If a building with specific architectural features and surroundings is accurately modeled and tested in a BLWT, the measurements can be used in a direct manner to determine design loads.

This is typical of testing performed under Method 3 for

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design of tall buildings, in which a new high-rise building is modeled with the surrounding buildings and tested in the wind tunnel. The measurements (e.g., force-balance readings at the base, pressure readings on the surfaces) are then used in a fairly straightforward manner to design the foundation, structure and cladding for that building.

However, designing a test program which yields design-load values that can be applied to a variety of buildings, rooftops and surroundings that are different than those tested is more complex.

An accepted methodology for achieving this goal can be found in the testing approach used to develop the design values prescribed in ASCE 7 Method 2 for rooftops.

The GCp curves (relationships of GCp to tributary area) provided in Method 2 for different types of roof structures were derived from a wind-tunnel-test program that included a large, but inevitably limited number of building shapes, sizes, heights, etc. (much of which was done at the Boundary Layer Wind Tunnel Laboratory at the University of Western Ontario). The curves that were developed from this program, however, are prescribed by the code to be applied to buildings with different shapes, sizes and heights than were modeled in the test program. The key to this methodology is to generalize the results sufficiently so that the worst-case scenarios are captured and enveloped.

The testing and methodology used to generate bounding GCp curves in ASCE 7 for various types of roofs (e.g., roof slope, roof shape, building height, etc.) therefore provides a good starting point and framework for generating design values for rooftop solar arrays that can be applied across a wide spectrum of building types and shapes.

Unlike rooftops, solar arrays do not necessarily span the length and width of the building. As a result, the geometry and layout of the array as well as its location on the roof must be considered as critical characteristics that influence the array/rooftop aerodynamics and therefore the loading on the array and roof. Generalizing how these factors affect the loading for specific arrays on specific roofs is difficult and requires a great deal of testing and/or analysis to bound the worst aerodynamics cases.

Wind Tunnel Models and Approaches With the goal of general applicability in mind, there are three possible test approaches that might be used to generate design values for solar arrays on rooftops: aeroelastic fly-away models, force-balance models and pressure-tapped models. In all cases, if the results are to be used for design, these models must be tested in an appropriately scaled atmospheric BLWT. Fly-Away Testing Fly-away testing of aeroelastic models is not only a well-established methodology, but also one that is intuitively easy to explain. In this type of test, the solar array model is placed on the model building in the tunnel and the wind speed is increased until the array moves. (The term “fly-away” is misleading in many cases as the point at which the www.solarpowerworldonline.com

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EN GINE E RING DE V E LOP ME NT S model first moves is typically below the point at which the model “flies.”) When the array mass, component stiffness and coefficient of friction between the array-to-roof contact points are known and accurately modeled, it is possible to measure the wind speed required to move the array.

While this method of testing is straightforward, it also presents challenges inherent in the process. First, given the complexity of mechanisms involved and the stochastic nature of wind, tens of test runs may be needed for each experiment to establish confidence around the wind speed at which movement occurs. Given that experiments need to be run for all practical wind angles and for the various types of roof/ array orientations and array configurations, the number of tests to obtain results for generalized use in design can quickly make this type of testing prohibitive.

The second and perhaps most daunting fly-away testing challenge is constructing appropriate aeroelastic models. To achieve accurate results, model weight and stiffness must be modeled accurately and at the proper scale. This is extremely difficult to do with a 1:30 scale solar array model. If the stiffness of structural members and joints are not accurately modeled, the results may not be representative. The stiffness of these components and joints can be quite complex to obtain by analysis or measurement at full scale, but doing so is required prior to attempting to build a representative model Because model stiffness is both critical to the results and difficult to model at 1:30 scale, it needs to be examined carefully.

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The sensitivity of the test results to stiffness diminishes as the stiffness of the array structure increases. Assuming a fully rigid structure therefore simplifies the analysis and is something that one might be able to justify for individual modules or small sections of an array, but for larger array structures, the assumption of rigidity leads to underestimating design loads.

A third challenge is the difficulty of generalizing results to arrays of different sizes and shapes from that which is tested.

For example, if an accurate aeroelastic model is created for a six-by-six module array, the results will provide guidance for a six-by-six module array with the same weight distribution and stiffness, but not for smaller array structures, arrays with different shapes, or even a six-by-six array with different weight distributions or component stiffness. Many combinations of array sizes, shapes and ballast configurations would therefore need to be properly modeled and tested on different locations on the roof, and with different wind approach angles to produce design values appropriate for array layouts of various shapes and sizes.

Given the complexity and cost of producing representative aeroelastic models and the need to run multiple tests for each data point, the cost of modeling and testing quickly becomes prohibitive.

Finally, a fourth fly-away testing challenge relates to understanding the various load paths between components.

Without some idea of the load sharing required between modules, the designer cannot analyze if the array structure is strong

enough to withstand highly concentrated local loads. This is an important issue for wind design as local loads (e.g., 10 square feet) can be many times higher than what would be expected by simply extrapolating from measurements taken on larger areas (e.g., 200 square feet).

There is also one final critical shortcoming to fly-away testing: The key design value of downward load imparted on the roof by the array cannot be determined.

Research shows that this load can be an important consideration in design of some components and in analyzing roof-deck loads.

Force-Balance Models Another approach to determining the wind forces on arrays is to create a test program similar to the fly-away approach, but using force-balance models, or array models that are attached to the roof with strain gauges or load cells attached to the connection points.

If each module is instrumented appropriately, it is possible to obtain a good picture of the forces they experience. The primary difficulty with this methodology is the instrumentation.

Positioning strain gauges across a 1:30 array model and connection points that can be accurately calibrated and read at the required frequency is an emerging science. It would require a massive, expensive undertaking to create and set up appropriate models for the large number of experiments (i.e., multiple array sizes and shapes and locations on the rooftop) needed.

Pressure-Tapped Models While fly-away and force-balance models monitor behavior at the interface between the array and the roof, pressure-tapped models measure wind pressures directly on the surface of each module. Pressure-tapped models have small holes or “taps” across the surfaces of the models, which are in fact the open end of air-tight tubes connected to equipment measuring pressure in the tubes.

The pressures on the model surfaces are measured such that net forces on each surface can be obtained, and the forces can then be summed to provide the load on individual sections or the entire array.

Though there are many advantages

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Doing so is computationally demanding as it requires calculations on the components of the array for every array design and for multiple area-specific load cases applied to different areas within the array.

to this type of testing, the key challenge is creating appropriately scaled models and setting up instrumentation than can accurately measure the pressures in each tube at the frequency needed.

This type of testing has the benefit of being extremely well developed, as it is the standard methodology used for wind tunnel testing of buildings. In fact, pressure-tapped models were used as the basis for developing the rooftop load curves (GCp curves) used in ASCE 7 for low-rise buildings in the late 1970s.

To measure the forces on a solar array using this methodology, the array model must include pressure taps across its various surfaces including (for example, taps on both the upper and lower module surfaces). The array models then need to be placed on a building rooftop model and measurements made for all wind approach angles and with the array in different locations on the roof.

The data from these experiments can be used to determine net forces on any expanse of array at any instant in time. The peak pressures at any instant in time (considering

all of the time history) for any array area can then be calculated. If one calculates the peak net forces over all relevant area combinations (e.g. one-module areas, two-module areas, three-module areas, etc.) for experiments covering all wind angles and appropriate setbacks, a curve for the areas of the solar array can be created similar to the GCp curve provided in the code for rooftops.

As in the case of the code for rooftops, a curve constructed in this manner will provide a bounding case on the magnitude of loads for various areas of array, provided that the array geometry (e.g. tilt angle, spacing between rows, clearance off the roof) is consistent with what was tested. Unlike the fly-away model approach, this method provides information on both upward and downward loads on the array.

While the peak values determined by this methodology are appropriate for design, it requires the appropriate application of various area-specific peak values to the array to check for strength of the array and the connections between the array and the roof. www.solarpowerworldonline.com

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Summary Wind-tunnel testing can provide an appropriate basis for design of rooftop solar arrays per the code if the testing is done properly and the results of these tests are appropriately applied.

Of the three testing approaches typically used in boundary layer wind tunnels, fly-away testing of aeroelastic models, force-balance models and pressur- tapped models, only the force-balance and pressure-tapped models can provide all the critical information needed for such a program.

However, fly-away testing of aeroelastic models cannot provide downward forces on the array that are transmitted to the roof structure. It also does not provide a clear idea of load distributions across the array and therefore makes it very difficult to determine the demands on various array components.

On the other hand, pressure-tapped models and force-balance models directly measure the loads on the array over time.

This time history, along with the spatial distribution of loads, can be used to determine the appropriate set of design loads for the array and array components.

Given the current state of technology and constraints imposed by Method 3, the force-balance approach may not be practical at the scale required.

Pressure-tapped models are therefore the best single approach for this type of program. However, because each of the testing approaches offers a slightly different perspective on array performance, there is value to looking at each. SPW

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[CONTRACTORS C O R N E R ]

Meridian Solar, Austin, Texas

Andrew McCalla

Meridian Solar

Andrew McCalla says the solar bug bit him when he was living in South America in 1992. He visited the Earth Summit in Rio de Janeiro that year and familiarized himself with photovoltaic (PV) solar technology and its global implications.

When he returned to the United States in 1995, he attended Solar Energy International, a trade school in Carbondale, Colo., to learn more about the industry. He graduated and joined a solar project design firm.

“We were designing the best of systems, but we were still getting callbacks with some frequency,” McCalla says. “I decided it was because it was a nascent technology, and the installations weren’t happening as well as they could because the expertise wasn’t out there.”

In 1999, McCalla left his firm to launch Meridian Solar, at that time a one-man operation.

“The philosophy was to make sure we had the best components, the best designs and to do quality installations,” McCalla says. “I was in it for the long haul — still am — and reputation matters a lot, not just for the company, but for the technology.”

Meridian has approximately 600 PV installations (450 residential with the balance being commercial), although they have since closed

Meridian Solar Vital Statistics:

their residential division to focus strictly on government, public, commercial and small-scale utility installations).

The number of employees has varied, growing from 18 to 42 (at the height of their residential business) and now stands at 28. “We used to do everything in house, but as we grew — especially in a state as large as Texas — we couldn’t build the army and take it cost-effectively on the road to complete projects solely on our own,” McCalla says.

“Now we do all our design, engineering and procurement in-house,” he continues. “We have project managers and field supervisors that are able to oversee local specialty contractors or temporary/permanent hires.”

The Texas solar market is complicated because it’s its own grid and is a patchwork of co-operatives, municipal grids and utilities. It also presents a challenging mix of regulated and unregulated entities, each with its own interconnection protocols.

“As an old well-driller in West Texas once told me, each one is a different kind of cussing,” McCalla says.

“You have to figure out what guidelines govern each installation individually, and that can be a challenge.” SPW For the full interview with Andrew McCalla of Meridian Solar, go to www.solarpowerworldonline.com/ contractorscorner to hear the podcast.

3-year growth:................400% Employees:.....................28 Founded: .......................1999 Website: www.meridiansolar.com

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