Alejandra Acuna Balbuena, Emma DeAngeli, Emily Fitzsimmons, and Alaine Nguyen Information for the OKC Sustainability Plan Introduction We are excited to have had the opportunity to research potential ways to include solar in the OKC sustainability plan. Through our research, we’ve discovered opportunities for you all to consider. While Emma and Alaine researched specific cities and how they’ve worked to implement solar energy, Emily used the NREL tool to calculate the benefits that OKC might see from incorporating this renewable energy into the Sustainability Plan. Additionally, we have attached research from our fourth group member, Alejandra. She looked into what the research says regarding the implementation of solar and sustainable solutions. We hope that you will find this document useful! Solar Development in Austin, St. Louis, and Kansas City - Emma I researched several cities in relation to how they implemented solar programs within their cities. The cities I researched were Austin, St. Louis, Kansas City, and Topeka (as you will see, Alaine also touched on Austin but she emphasized infill projects). When applicable, I address the ways in which this might directly benefit OKC in the incorporation of solar energy. Austin One interesting project in Austin is the Colony Park Sustainable Community Initiative. Austin was granted $3,000,000 from the U.S. Department of Housing and Urban Development through their Sustainable Communities Challenge. Their project entails encouraging sustainability within development in the Colony Park neighborhood and on its public land. While they have not yet completed the implementation phase of the project, it was clear that they relied upon relevant community stakeholders as well as development experts. That being said, Austin residents likely have more interest in solar than those in OKC. There is an entire nonprofit, Solar Austin, that is geared towards encouraging its widespread use throughout the city. They have worked with the Austin city government before on several initiatives, including the Equitable Clean Energy Jobs Program. This was also created with UT Austin to ensure its effective implementation. Even though there might not be a nonprofit exactly comparable, the U.S. Department of Energy’s SolSmart initiative may have some helpful tools to encourage citizens to value solar. In addition, the city advertises solar as a money-saver for its citizens. They have an app and a website that commercial customers can observe what energy they’re using and how they are using it. This is through Green Button Data, a website that informs people of their utility usage data to see where some waste inefficiencies might exist. When implementing solar, residential customers can earn credits to apply to electric bills and increase the property value of their home and reduce demand charges and get LEED points. Since solar may not be feasible for individual households, community solar panels allow people to opt for getting their solar energy somewhere else in the city; they’ll install solar somewhere other than the residences. This seemed like a creative, communal solution.
St. Louis St. Louis’ Sustainability Plan mentions solar energy several times, mostly in relation to what their goals are. Specifically, they would like to use solar farms and install more bases for renewable energy. Strategies that they mention are using federal tax credits and providing information about sustainability for zoning or building applicants. There appears to be a parallel between this and Austin; they provide very clear information on their website about the incentives they have for citizens to use renewables. Additionally, the PACE programs in both of the cities have ample incentives for using solar energy. It seems that St. Louis is largely in the development stage of their solar infrastructure. On their website, it says that their solar permitting checklist and other guidelines are “coming soon.” Therefore, they may be a good contact since they’re in a similar stage of development. Something that they already have outlined is solar installation guidelines for historic districts, so this may be helpful to reference as well. Kansas City A unique resource that both St. Louis and Kansas City have is the Missouri Clean Energy District. It provides capital for localities in their development of renewable energy. A comparable program in Oklahoma is the Oklahoma Renewable Energy council. They might be a helpful contact in the development of solar in the sustainability plan; their strategic plan mentions wanting both to educate citizens about solar energy and to build more relationships with relevant stakeholders. Also, the renewable energy credits that they advertise are very similar to how Austin has communal solar panels from which people may get their power, so it seems to be a best practice. Kansas City has developed their strategic plan in changing the Kansas City Zoning and Development Code to include information about solar. They have also created several documents, including a consumer’s guide to solar and information about rebates and incentives, to help the public in their pursuit of solar energy. They also won a Gold SolSmart Designation meaning that they were designated as having good solar development. Something seemingly unique that Kansas City implements to meet their sustainability goals is KC Green. This is a volunteer effort from members of city government who divide into teams to ensure that the city is meeting their “green” goals. These teams are education and outreach, green infrastructure, regulation and policy, and resource management. Perhaps this could be a feasible solution to encouraging sustainable efforts, including solar, within the community. Infill and Renewable Development in Austin and Aurora - Alaine I researched for potential urban development tools relating to renewable energy and solar energy from the cities of Aurora and Austin that could help facilitate sustainable infill development in Oklahoma City. I found helpful tools such as existing zoning codes, building codes, other planning tools located in the peer cities to outline valuable practices and lessons for OKC to follow as recommendations. I wanted to focus on Austin because the state of Texas has the largest wind potential and solar energy potential in the country as well as some of the most urban infill opportunities. I chose Aurora because renewable energy is a growing industry in the state of Colorado and it leads in many areas of renewable energy such as solar, wind,
and hydropower in response to the limited supply of fossil fuels. With that said, these cities would have some of the best planning tools to recommend OKC infill projects. In Dallas, the most needed types of development are affordable housing projects, such as apartments and homeless shelters. Most of these infill projects aim to reduce the amount of underutilized land within existing communities and increase housing and business densities and private investment. Mueller is an urban infill project that focuses on sustainable community development located in Austin, Texas, where the developments tend to be set in less polluted areas that are far from the resources of surface and groundwater. One of their nonprofit buildings was the first in Texas to utilize solar power and an art gateway of theirs collected sun rays that convert them into solar energy to light the art pieces during the nighttime. They are benefitted by Austin Energy, an electric utility company, that is committed in providing affordable and consistent energy to several Austin communities. The company created a cooling-healingpower plant that is a part of the community’s infrastructure that helps with lowering energy costs. With the help of Austin Energy’s Green Building Program, Mueller’s infill projects are able to have sustainability features that are energy efficient and also solar readiness through the use of national LEED standards. In Aurora, Colorado, the SIR (Sustainable and Infill Development) Zoning District follows a mix of commercial, civic, and residential uses in areas that meet the requirements for redevelopment and infill development. The new zoning district is located in the existing and developed lots of Aurora that are located along major streets that support new businesses and increase living choices, with one of the district’s goals is to promote energy and resource efficiency. They have done infill projects with passive solar tools where they have different elements that boost energy and resources efficiency of infill development, and the energy efficiency and renewable energy components can help businesses lower their operating costs through decreased utility costs. Aurora maximizes building orientation to take advantage of solar energy, use designs that take advantage of the sun for heating and lighting, and designs that provide natural cooling for a building’s windows, walls, and floors so they can store and deliver solar energy through heat in the winter and to reject solar heat in the summer since architectural designs can produce an average of 35% reduction in energy use yearly. They add window canopies to collect seasonal cooling and heating cycles, install materials that provide thermal mass like bricks, and create concrete forms to improve building security. They use renewable energy tools to incorporate renewable energy into design with combining solar, wind, and geothermal into new and existing construction because it offsets energy use and increases sustainability, and then based on the characteristics of the site, there are approaches to use such as install solar photovoltaic arrays, install small or district-scale wind systems, absorb energy efficiency to increase project sustainability, and then install electric vehicle charging stations driven by renewable energy. They use green infrastructure to add value by conserving water, managing natural storm water runoff, and creating an aesthetically pleasing environment. Assuring redevelopment complements with Aurora’s barren climate also reduces the energy demand and increases the value of the overall project. With the tools, they construct bioswales to remove pollution from surface runoff and design irrigation systems with storm water. They use heat island reduction methods to install paving materials that reflect more solar energy, enhance water evaporation, reduce pavement area for parking, and use Energy Star roofing. They install Energy Star roofing material, propose landscape ideas to include stormwater management, and
expand the city’s tree population by preserving existing trees and planting more. These solar energy designs from Aurora could be beneficial to OKC’s sustainable development. NREL and the Benefits of Solar - Emily Like other cities around the globe, Oklahoma City has much to gain from solar energy. Oklahoma has depended on its resources of oil, natural gas, and coal for a long time, but these fuels have serious drawbacks, including public health issues, ecosystem degradation, and massive, misplaced expenditures to support a quickly vanishing energy source. Instead of investing more valuable time and resources into fossil fuels, this great state should take advantage of our fierce wind and clear blue skies to transition to renewable energy. Since 1993, Oklahoma City has implemented a series of tax-funded improvement ventures in order to make the city more livable. The Metropolitan Area Projects, or MAPS, plan has transformed the state capitol into a thriving destination with public transit, gorgeous parks, and blooming neighborhood districts. Recently, residents approved MAPS 4, and over the next decade, the program will add more parks, alternative transportation infrastructure, an animal shelter, new economic hubs, and community centers, which will provide recreation, education, and services for all members of the community. Specifically, the MAPS 4 plan has set aside $110 million for at least four new youth centers and the existing Douglass Recreation Center, $30 million for a new senior wellness center, $38 million for a new family justice center, and $25 million for renovations at the existing Freedom Center and construction of the Clara Luper Civil Rights Center addition. As these enhancements to Oklahoma City are built, it is important to recognize this critical opportunity to begin the necessary transition to renewable energy. According to the U.S. Energy Information Administration (EIA), there were approximately 352,000 public assembly buildings such as those proposed in MAPS 4 in the United States in 2012. Altogether, these buildings consumed 245,310,668,229 kWh of primary electricity and 80,597,889,800 kWh of site electricity each year. The EIA also estimated that the annual electricity expenditures for these buildings added to $7,889,000,000, or $22,411 per building. If electricity were supplied by solar energy, pollution would be greatly reduced, improving the air, soil, and water quality imperative to human health, ecosystem well-being, and the natural resources on which our state’s economy is dependent. A preliminary screening of the benefits of a solar transition on human health can actually be performed using the EPA’s peer-reviewed Health Benefits per kWh method, which translates health benefits to monetary values. According to this, Oklahoma would save 2.19-4.96 cents/kWh saved via solar. Additionally, solar energy decreases greenhouse gas emissions, helping curtail the local effects of climate change, such as more extreme temperatures and more sudden and unpredictable severe weather that disrupts both human and wildlife ecosystems. Notably, the Office of the United States Trade Representative also states that Oklahoma’s biggest exports are beef and veal, wheat, pork, cotton, and other plant products, which each siphon millions of dollars into the state. The current use of fossil fuels pollutes and harms the environment on which the state’s economy depends, but solar energy could easily coalesce with humans and nature. Through the use of a System Advisor Model by the National Renewable Energy Laboratory, or NREL, simulations in the PVWatts calculator indicate that Oklahoma City would save thousands of dollars each year from its electricity bill alone for solar-powered buildings in
addition to the previously mentioned savings and benefits, especially if the solar farms were funded as part of the MAPS budget. Furthermore, even if the city chose to take out a loan for a solar farm, the simulations show just a fifteen to twenty-five-year discounted payback time, depending on the system; likewise, even the most expensive of my simulations cost only a little over $727,000 while producing 698,369 kWh annually. Because I do not have the technical details specific to the solar system and financial model Oklahoma City would select, I was limited to the PVWatts calculator rather than the Detailed Photovoltaic calculator, which is much more comprehensive. Additionally, I had to make assumptions about the type of panel and mounting system. Because of my own limitations, I highly recommend that the planning department run their own simulations to find the best system for the budget. To aid in this, a supplemental document is attached with helpful information for running solar energy simulations in the NREL calculator. Sources Annotated - Alejandra We apologize for the more informal formatting on this section. Alejandra is not able to synthesize her portion due to COVID-19 related circumstances, but she did some great research! Amado, M. & Poggi, F. (2012). Towards Solar Urban Planning: A New Step for Better Energy Performance, Energy Procedia 30, 1261-1273, https://doi.org/10.1016/j.egypro.2012.11.139. This paper explores the concept of Solar Urban Planning with the goal of developing an operative methodology to achieve the best conditions towards Zero Energy Building (ZEB). The task to provide high solar performance buildings could be attained in a better way if the urban planning process integrates a solar energy approach to both new and existing urban environments. Solar urban design is a “new phase” of sustainable urban planning, a phase that has wide horizons of development and could provide new solutions to the world's energy problem by reducing its consumption and improving the performance of future buildings. Garde, A & Kim, C. (2017) Form-Based Codes for Zoning Reform to Promote Sustainable Development: Insights From Cities in Southern California, Journal of the American Planning Association, 83 (4), 346-364. https://doi.org/10.1080/01944363.2017.1364974 This article examines the extent to which form-based codes adopted by California cities differ from conventional zoning regulations using a multiple-case study of 26 cities in Southern California. Their findings suggest that form-based and conventional zoning regulations can each help cities integrate sustainability criteria into their development regulations. Kanters, J & Horvat, M. (2012). Solar Energy as a Design Parameter in Urban Planning, Energy Procedia 30, 1143-1152, https://doi.org/10.1016/j.egypro.2012.11.127. According to this article, by the end of 2020, all EU member states need to ensure that all newly constructed buildings consume ‘nearly zero’ energy and that their energy needs are produced locally as much as possible and with renewable sources; a concept called nearly Zero
Energy Buildings (ZEB). This study shows an exploration of geometrical forms of urban blocks and the potential of solar energy to the local production of energy for the city of Lund in southern Sweden. It was found that the impact of the geometry form on the potential of solar energy was significant (up to twice as much) and some forms were found to be less sensitive for different orientations. Kanters, J. & Wall, M. (2014) The impact of urban design decisions on net zero energy solar buildings in Sweden, Urban, Planning and Transport Research, 2(1), 312-332, https://doi.org/10.1080/21650020.2014.939297 This study examines the effects of important design decisions on the solar energy potential of net zero energy solar buildings. Results of this study show that the urban density is the most influential parameter on the solar potential of building blocks. Furthermore, flat roofs often returned the highest load match value, while the effect of orientation on the solar potential turned out not to be that straightforward. Kim, J. & Larsen, K. (2017). Can new urbanism infill development contribute to social sustainability? The case of Orlando, Florida. Urban Studies, 54(16), 3843–3862. https://doi.org/10.1177/0042098016670557 Deriving community indicators for social sustainability – including housing affordability and socioeconomic diversity – and from studies assessing new urbanism as an infill development tool, this study examines the impact of new urbanism infill development in Parramore, an economically distressed inner city neighborhood, and Baldwin Park, a brownfield inner-ring suburb, with comparative control neighborhoods in Orlando, Florida. The findings from these two distinct cases of infill development indicate that the new urbanism does not necessarily ensure social sustainability, though these principles are often integrated into publicly funded revitalization initiatives dedicated to doing so through mixed use and mixed income development. Lehmann, S. (2012). Sustainable Construction for Urban Infill Development Using Engineered Massive Wood Panel Systems. Sustainability, 4(10), 2707-2742. https://doi.org/10.3390/su4102707 This study is a little dated, however, this article offers insights into the potential of prefabricated engineered solid wood panel systems as a sustainable building material and system. It highlights the properties of timber as one of the few materials that has the capacity to store carbon in large quantities over a long period of time, pointing out that solid wood panel construction offers the opportunity of carbon engineering, to turn buildings into ‘carbon sinks’ in the long run. It could be an interesting study for OKC to look at, especially regarding brownfield development. Niemasz, J., Sargent, J., & Reinhart, C. F. (2013). Solar Zoning and Energy in Detached Dwellings. Environment and Planning B: Planning and Design, 40(5), 801–813.
https://doi.org/10.1068/b38055 The solar envelope is a three-dimensional volume on a building site which will not shade adjacent neighbors during a specified minimum of hours each day, developed as a tool to give buildings in an urban setting the mutual opportunity to employ passive and active solar-design strategies. This study investigates the implications of a solar-envelope zoning approach for the most common building type in the United States with respect to energy use and developable density. The results indicate that solar zoning for this building type has a limited, and sometimes negative effect on energy use as well as a larger negative impact on developable density. Nolon, J. R. (2015). Mitigating Climate Change by Zoning for Solar Energy Systems: Embracing Clean Energy Technology in Zoning's Centennial Year. Zoning & Planning Law Report, December 2015. Available at SSRN: https://ssrn.com/abstract=2733319 This article explores efforts at the state and local level to reform zoning and land use regulations to permit, encourage, require, and incentivize rapidly-evolving clean energy systems, particularly solar, that, in the aggregate, have the ability to significantly increase power generation and decrease carbon emissions. The article illustrates how zoning, as it approaches its 100th anniversary, is encrusted with provisions that prohibit or discourage clean and solar energy systems: barriers that are being removed by progressive communities, some more successfully than others. Conclusion We all found that solar and other sustainable initiatives could be beneficial for OKC to implement. From Emma and Alaine, we learned how cities implement solar and infill projects. From Emily, we learned what the benefits of solar could be. And from Alejandra, we learned what would be important to consider when moving forward with sustainable development. Once again, thank you for allowing us the opportunity to do research for you all!
Bibliography “About MCED.” Missouri Clean Energy District, https://www.mced.mo.gov/about-mced/ “About Us.” Solar Austin, https://solaraustin.org/ “Aurora, CO, Sustainable Infill and Redevelopment Design Handbook.” American Planning Association, www.planning.org/knowledgebase/resource/7002319/.
City of Oklahoma City. “MAPS 4 Projects.” Accessed April 28, 2020. https://www.okc.gov/government/maps-4/projects “City of St. Louis Sustainability Plan.” City of St. Louis, 6 February 2013, https://www.stlouismo.gov/government/departments/planning/sustainability/documents/city-of-st-louissustainability-plan1.cfm “Colony Park Sustainable Community Initiative Facts.” City of Austin, http://www.austintexas.gov/department/about-colony-park “KC Green.” City of Kansas City, Missouri, https://www.kcmo.gov/programs-initiatives/kc-green555 Office of the United States Trade Representative. “Oklahoma.” Accessed on April 28, 2020. https://ustr.gov/node/7255 “Quick Facts.” Oklahoma Renewables, http://www.okrenewables.org/ “Rebates and Incentives.” Austin Energy, http://powersaver.austinenergy.com/ “Solar and the City of St. Louis.” City of St. Louis, https://www.stlouismo.gov/government/departments/planning/sustainability/solar-and-the-city.cfm “Solar Energy: SolSmart’s Toolkit for Local Governments.” SolSmart, https://solsmart.org/solarenergy-a-toolkit-for-local-governments/ “Solar Panel Permits.” City of Kansas City, Missouri, https://www.kcmo.gov/cityhall/departments/city-planning-development/solar-panel-permits “Thinking Green.” Mueller Austin, www.muelleraustin.com/thinking-green/. United States Environmental Protection Agency & State and Local Energy and Environmental Program. “Public Health Benefits per kWh of Energy Efficiency and Renewable Energy in the United States: A Technical Report.” Last modified July 2019. https://www.epa.gov/sites/production/files/2019-07/documents/bpk-report-final-508.pdf U.S. Energy Information Administration. “Commercial Buildings Energy Consumption Survey (CBECS).” EIA. Last modified May 2016. https://www.eia.gov/consumption/commercial/data/2012/c&e/cfm/c13.php
An Abridged Guide to Solar Simulations in NREL’s SAM Program https://sam.nrel.gov/ NREL website provides… ● Free download of the SAM program for running energy and fiscal simulations for photovoltaic systems, concentrated solar plants, solar thermal systems, wind turbines, tidal energy, geothermal systems, biomass combustion systems, and batteries ● Instructional videos ● A list of web resources with costs of renewable energy projects on the Cost Data page ● Another, older version of PVWatts that is not as in-depth but does not require downloading the program General Instructions: 1. Click “Start a new project” button 2. Click one performance model and one financial model. Click OK.
3. SAM will use default values for the input numbers. Most of these can be left alone, but it depends on which model you are completing. Review the inputs for values you may need to change, such as… a. Project location b. Weather (derating factors, insolation, etc.) i. Type in address or location, and if the location is covered by NSRDB, it returns with a weather file and adds it to the weather file download folder c. Type of equipment (collector and receiver type, storage capacity, solar multiple, power block capacity, number of modules and inverters, tracking type, derating factors, etc.) d. Cost of installation (equipment purchase, labor, engineering, land cost, etc.) e. Cost of operation (labor, maintenance, etc.) f. Financial incentives (real discount rates, inflation rate, tax rates, internal rate of return target or power purchase price, building load, time-of-use retail rates, tax/cash incentive amounts/rates, etc.) g. Analysis period i. You can either choose a specific year(s) from the past or deselect “Default TMY file,” which downloads a typical meteorological year weather file for the chosen location 4. “Simulate” button 5. Examine results a. Results can be shown in default or personalized metric tables and graphs b. You can make post it notes on any input or result page. Click on the small white square button in the top right of the screen called “Show a note.” A window will pop up, and you can type your note. To save and hide, just click the red X box of the post it note window. The navigation menu will show a note icon for all pages with notes. To delete a note, delete all text in the note pop up box and X out. c. SAM’s report generator helps you create reports that include the results. Click on the case tab at the top, which will reveal a dropdown menu. Then click “Create Report.” d. Performance Model Results i. “Summary” includes the metrics table with important metrics and graphs that summarize the performance, such as annual electrical output, capacity, factor, etc. ii. “Losses” includes an energy loss diagram iii. “Graphs” includes graphs of hourly, monthly, annual, and single values iv. “Data” includes tables of hourly, monthly, and annual data v. “Time Series” includes graphs with time series data and statistics of hourly and sub-hourly data vi. “Profiles” includes time series data as daily profiles by month vii. “Statistics” includes the mean, maximum, minimum, sum, standard deviation, and average daily minimum and maximum values of time series data viii. “Heat map” includes one year’s worth of time series data set in one graph using colors to represent magnitude e. Financial Model Results
i. ii. iii. iv.
“Summary” includes the metrics tables with important metrics like LCOE, PPA price, IRR, and payback period as well as graphs for the projects after-tax cash flows “Cash Flow” includes details of the project cash flows “Data” includes tables of cost and cash flow data along metrics and timedependent electricity sales and price data “Time series data” includes time-dependent electricity sales and price data
Overview: SAM predicts performances and cost of energy for projects that are connected to the grid based on the installation and operation costs as well as the parameters of the system set-up that you input into the model. Models can be for projects that buy/sell electricity at retail rate or through a power purchase agreement. Performance models can calculate hour-by-hour estimates of a power system’s electrical output. Results can be viewed in hourly, monthly, or annual data. Note: Only monthly and annual data will be saved due to file size; to view the hourly data, you will have to run your simulation each time. Financial models are based on the project’s cash flows during the chosen analysis period. SAM can calculate the internal rate of return if you give a power price, or vice versa. The annual cash flow of a project includes value of electricity sales or savings, incentive payments, installation costs, operation costs, equipment replacement costs, debt and interest payments, tax benefits/credits, liabilities, project and partner’s internal rate of return requirements (for power purchase agreements). SAM calculates a project’s levelized cost of energy – the cost of installation and operation, including incentives, debt, and costs – and the net present value of cash flows after taxes and the payback period in years needed for the after tax cash flows to cover the initial investment. Financial models can simulate either…. ● residential/commercial projects that buy/sell electricity at retail rates and displace purchases of power from the grid (assumes a single entity develops, operates, and owns the project) OR ● power purchase agreements that sell electricity at wholesale rates to satisfy the internal rate of return requirements 3 types of Photovoltaic System simulations (SAM can model grid-connected PV systems that include a PV array and an inverter, either flat-plate or concentrating modules with one- or twoaxis or no tracking at all) ● Detailed Photovoltaic-Use this when you have detailed information about the equipment to be used in the system. Requires module and inverter specifications, including amounts; you can either input your own from a data sheet or select a module and inverter from the SAM libraries
Inputs you need to provide include… ● Location-Choose your location or the nearest one from the solar resource library ● Module type-Choose a module with a maximum power rating (Pmp) close to the one in your system from the Module Database library ● Inverter-Choose an inverter with a maximum AC power rating close to the one in your system from the CEC Database library ● System Design-Using the “Specify desired array size” option, enter the value for the size of your system. Under “Tracking and Configuration,” select a tracking option and a value for tilt in “Subarray 1” ● Shading and Layout-By default, SAM models with no shading losses; SAM recommends ignoring these inputs at first ● Losses-Review these values, but SAM also recommends not altering the defaults for the initial analysis ● PVWatts Model-makes assumptions for 3 types of modules about its modules and inverters; requires input information on the systems nameplate capacity, array orientation, mount type, and system losses; recommended for preliminary or less in-depth analyses ■ Inputs you need to provide include… ● Location-Choose your location or the nearest one from the solar resource library ● System Design-Enter values for the nameplate size and the tilt ● Concentrating Photovoltaic-produces distinct models for the module and the inverter; requires information about the concentrator design and cell efficiency; inverter information can either be manually input or extracted from a library ■ Inputs you need to provide include… ● Location-Choose your location or the nearest one from the solar resource library ● Module-Enter the values for “Single Cell Area,” “Number of Cells,” and “Concentration Ratio” ● Inverter- Choose an inverter with a maximum AC power rating close to the one in your system from the CEC Database library ● Array-Enter values for the number of trackers and the modules on each tracker ■
SAM can also include an electric battery storage model: detailed PV-battery, PVWatts-battery, and generic system-battery: ● Choose the battery chemistry ● Choose the bank size in kWh for the battery size and a value in kW for the maximum discharge rate. Note: The nominal hours for storage is the capacity in kWh divided by the bank power in kW. Example: a 20 kWh battery with a 10 kW bank power is nominally a 2-hour battery. ● There is no need to change the default dispatch model as it will match the chosen project model, but you can if you wish. ● Battery replacements are accounted for by default and will be included in the simulations
cash flow results On the input pages, text boxes are color-coordinated: ● Input variables that you can change are in white boxes with black text ● Values that you cannot change are in blue boxes; these include calculated values, values from other input pages, and values extracted from the library ● Values you cannot change also appear in gray boxes P50/P90 Simulations You can run a simulation that generates P90 and P50 values. A P90 value is a value that is expected to be met or exceed 90% of the time. This kind of simulation runs hourly data over a period of multiple years, so this requires at least ten weather files of consecutive single-year data. If pulling weather files from the database, use the dropdown box to click “Download files for all years (P50/P90).” If uploading your own set of weather files for this type of simulation, place them all in one folder with no other files and name each one as follows: file name_year.extension (For example: portalnd_psm_1998.csv, portland_psm_1999.csv, etc. ). Now to actually run the P50/P90 simulation, click “Configure Simulations” on the main window to view the Configure Simulations page; then select P50/P90. For the “Select weather file folder,” click the “….” And go to the folder with the weather files. Click “Run P50/P90 analysis.” Not doing a P50/P90 simulation simply means that SAM will use data from just one year with the financial model to represent multiple years, otherwise known as “typical data,” or you can use “single year data” to run a simulation on a system’s performance over the course of one year. PV Sizing and Configuration SAM works with two distinct approaches to input the array size… ● For a PVWatts simulation, you need to input the nameplate DC capacity in kW as well as the DC to AC ratio. This approach is good if you do not know the type of arrays or inverters for the system yet and just need a preliminary size or production estimate ● For a Detailed Photovoltaic Model, you must input the module type, inverter type, number of modules in a string, and the number of strings in an array. More required but better results Choosing the number of modules and inverters based on the array’s expected DC output rather than nameplate capacity… ● Either choose a specific inverter or input the chosen inverter’s specifications on the Inverter page. If you have not selected an inverter for your system yet, you can choose one with a maximum DC power near to the array size you are modeling or choose one with a maximum AC power that equals the desired DC capacity divided by your desired DC to AC ratio ● Choose a module or input its parameters on the Module page. If you do not have a specific module in mind, choose the default. ● On the System Design page, under AC Sizing, type 1 for the Number of Inverters. ● Under DC Sizing and Configuration, for Subarray 1, type a value for Modules Per String in Subarray that results in a Sting Voc – a string open circuit voltage – less than but as close as possible to the inverter’s maximum DC input voltage and greater than the inverter’s minimum MPPT voltage.
● For Strings in Parallel in Subarray, type a value that results in an array nameplate capacity that is near your desired systems DC capacity. Choose a value close to: ● Strings in Parallel = Array Nameplate Capacity (kWdc) × 1000 (W/kW) ÷ Module Maximum Power (Wdc) ÷ Modules Per String. ● Depending on the chosen inverter, you might need to modify the number of inverters to match the array’s size ● Number of Inverters = ( Modules per String × Strings in Parallel × Module Maximum Power (Wdc) ) ÷ ( DC-to-AC Ratio × Inverter Maximum AC Power (Wac) ) ● Under Tracking & Orientation, input the tracking, orientation, and ground coverage ratio ● Input any losses on the Losses page ● Run the simulation. You can check your inputs by going to the Results page and checking that the Energy Yield (kWh/kW) is a reasonable value. For reference, the energy yield for the default system of mono-crystalline modules in Arizona is 1,850 kWh/kW. If the value is too low, check that the total inverter capacity is not too low and thus limiting the system AC output; in this case, you would try using a larger inverter, fewer modules, or a module from the same family with a slightly lower capacity. ● You can also check the inverter capacity by going to the Time Series tab on the Results page. Look at the Hourly Energy variable, which is the system’s AC output in kWh/h. For instance, if you input a 400 kW inverter capacity, but the time series data indicates that the system rarely operates at that level, you could try reducing the number of inverters to simulate a system with 315 kW of inverter capacity instead, which would reduce the system’s installation cost. ● Look at the Subarray 1 open circuit voltage and operating voltage variables; this can verify that the voltage does not exceed your design’s limits. ● Adjust the number of inverters, modules per string, and strings in parallel with each simulation run until you are content with your system’s performance and cost. Five module performance model options ● Simple Efficiency Module Model: a basic representation of module performance; requires you input the module area, the conversion efficiency values, and the temperature correction parameters. Least accurate model but is appropriate for determining the relationship between module efficiency, the system performance, and the cost of energy. ● CEC Performance Model with Module Database: calculates the module’s solar energyto-electricity conversion efficiency from the library’s data ● CEC Performance Model with User Entered Specifications: you enter the module specifications from a manufacturer’s data sheet ● Sandia PV Array Performance Model with Module Database: calculates the module’s conversion efficiency based on the data collected from modules and arrays during field work; this database includes modules with various cell types, such as crystalline silicon and thin film technology ● IEC61853 Single Diode Model: calculates the module’s conversion efficiency detailed parameters about the module Inverter options ● Inverter CEC Database: Calculates the system AC output with the parameters of the inverter chosen from SAM’s database. This method is appropriate for most simulations.
● Inverter Datasheet: Calculates the coefficients for the inverter model using the parameters you input from the manufacturer’s data sheet. This method is appropriate for an inverter that is not included in the CEC database. ● Inverter Part Load Curve: Creates a table of part-load efficiency values for an inverter using either data from the manufacturer’s data sheet or another source. This method is appropriate when you have an inverter’s part-load efficiency data. ● Inverter CEC Coefficient Generator: Calculates the coefficients for the inverter model when you have the inverter test data Electrical Configuration If your system just has one subarray, there is no need to enable additional subarrays as Subarray 1 is always enabled. If the system has more than one subarray, you should click Enable for each, up to four subarrays The number of modules per string determines the subarray’s open circuit string voltage, otherwise known as Voc, and the maximum power rated string voltage, or Vmp: Subarray Voc (V) = Module Voc (V) × Modules Per String in Subarray Subarray Vmp (V) = Module Vmp (V) × Modules Per String in Subarray In general, select a number of modules per string that results in the Voc being less than the inverter’s maximum DC voltage rating and the Vmp being in between the inverter’s minimum and maximum MPPT voltage rating. The number of strings in parallel and number of subarrays determine the system nameplate DC capacity in kW: Modules per Subarray = Modules per String in Subarray × String in Parallel in Subarray Total Number of Modules = Modules per Subarray × Number of Subarrays Nameplate DC Capacity (kW) = Total Number of Modules × Module Maximum Power (W) ÷ 1000 (W/kW) The number of modules in each subarray depends on the number of modules per string and the number of strings in parallel in each subarray: Number of Modules in Subarray = Modules per String in Subarray × Strings in Parallel in Subarray Total Number of Modules = Sum of Number of Modules in Subarrays 1 - 4 The open circuit DC voltage of each string (Voc) of modules as well as the DC voltage at the module maximum power point of each string (Vmp) of modules at the module reference conditions, as shown on the Module page: String Voc (V) = Module Open Circuit Voltage (V) × Modules per String String Vmp (Vdc) = Module Max Power Voltage (Vdc) × Modules per String
Tracking Four tracking options: ● Fixed-the subarray is fixed at the given Tilt and Azimuth values; it does not track the sun’s path ● 1 Axis-the subarray is fixed at the given Tilt and Azimuth values, but it rotates around the tilted axis to follow the sun from east to west. For a completely horizontal subarray, the tilt is zero; the azimuth is the orientation of the subarray based off a line perpendicular to the equator. ● 2 Axis-SAM ignores both the Tilt and Azimuth values. The subarray rotates from east to west each day and adjusts from north to south to account for seasonal changes ● Azimuth Axis-the subarray rotates on the horizontal plane, or the vertical axis, to follow the sun each day. SAM ignores the Azimuth value, and the Tilt is fixed. Tilt in degrees only applies to arrays with one-axis tracking and to fixed arrays. An arrays tilt angle is in degrees from horizontal where zero degrees is horizontal and 90 degrees is vertical. In general, many use the location’s latitude as the array tilt angle, but this will vary, depending on project requirements. The Azimuth angle decides an array’s east-west orientation for arrays with one-axis tracking and fixed arrays. For affixed tilted array, an Azimuth value of zero faces north while 90 degrees faces east, 180 degrees faces south, and 270 degrees faces west. A typical Azimuth value for systems north of the equator is 180 degrees Losses Loss inputs account for electrical and soiling losses that inverter and modules losses fail to account for. Batteries If you wish to include a battery in the simulation, check Enable Battery. You must provide the building’s electric load. The battery capacity is the size of the battery bank in kWh; the battery power is the battery bank’s maximum power output in kW; battery chemistry is the type of battery; battery discharge is how the battery will release its stored energy through the day. Battery models can simulate lead-acid batteries, lithium-ion batteries, vanadium redox flow batteries, and all iron flow batteries, though the PVWatts simulator cannot do all of them. Terms & Abbreviations Guide ● PV = Detailed photovoltaic model ● PVW = PVWatts ● HCPV = High concentration photovoltaic model ● CSP = Concentrating solar power ● TMY = Typical Meteorological Year; typical year data involves using data from a single year to represent multiple years ● MPPT = Maximum Power Point Tracking. MPPT input means the electrical connection to a maximum power point tracker; an MPPT electric circuit in a system can either be integrated with the inverter or in a distinct device. If you input the Number of MPPT on the Inverter page, type in the number of MPPT circuits in the system
● Power Purchase Agreement: A third-party developer builds, operates, and owns a PV system while a host customer allows the system to reside on their property. This same customer purchases the system’s electric output from the developer, which gives them stable electricity at a lower price. Meanwhile, the developer/owner can sell the remaining energy and receive the additional benefits of tax credits. (https://www.epa.gov/greenpower/solar-power-purchase-agreements) ● Solar multiple: a ratio between thermal power that is created by the solar field during the design point and the thermal power that is needed by the power block at normal conditions. (https://www.sciencedirect.com/science/article/abs/pii/S0038092X09001947) ● Power block capacity: the full-load, dependable electrical generation capability of a power block in kW (https://www.lawinsider.com/dictionary/power-block-capacity) ● Nameplate capacity: AKA generator nameplate capacity AKA installed capacity. The maximum output of prime mover, generator, or similar electric producing equipment under conditions specified by the manufacturer; generally given in megawatts, or MW; it is usually stated on a generator’s physical nameplate. (https://www.eia.gov/tools/glossary/index.php?id=G#gen_nameplate) ● Albedo: Ground reflectance; SAM uses albedo to adjust the irradiance incident on the solar arrays due to irradiance reflected onto the arrays from the ground; 0 means a surface is entirely non-reflective; 1 means a surface is entirely reflective; grassy ground is about 0.2, which the default in SAM; snow-covered ground would be about 0.6 ● Insolation: cumulative exposure to the sun’s rays over a period of time; typically expressed as kWh per square meter followed by the time interval (annual, monthly, etc. insolation) (https://pvpmc.sandia.gov/modeling-steps/1-weather-design-inputs/irradianceand-insolation-2/) ● Irradiance: the power from the sun as electromagnetic radiation per unit area in one instant, or watts per square meter (https://pvpmc.sandia.gov/modeling-steps/1-weatherdesign-inputs/irradiance-and-insolation-2/) ● Module: a solar module is another phrase for a solar panel, which consists of small solar cells which absorb sunlight to produce electricity (https://www.sunrun.com/go-solarcenter/solar-terms/definition/solar-module) ● Inverter: a system’s inverter converters the DC power produced by the solar panels into AC power, which is the type of electricity our buildings use (https://www.sunrun.com/gosolar-center/solar-articles/what-is-a-solar-inverter-and-how-does-it-work) ● Array: an array is a system of multiple solar modules, or panels (https://www.sunrun.com/go-solar-center/solar-terms/definition/solar-module) ● String: the connection between solar cells and the connection between solar modules in a system (https://www.pveducation.org/pvcdrom/modules-and-arrays/mismatch-effects-inarrays) ● DC vs. AC: DC is direct current; AC is alternating current. Solar panels produce energy that is direct current, but we use AC power because it is easier to manage. A system’s inverter converts DC power to AC power, so it can be used by our current grid. (https://www.sunrun.com/go-solar-center/solar-articles/what-is-a-solar-inverter-and-howdoes-it-work) ● Azimuth: the angular distance from the horizon on the north/south axis to a point projected into the sky. ● External Shading: Shade on a PV subarray due to trees, buildings, roof protrusions, and
other objects. This does not include neighboring panels, which would constitute selfshading. External shading is represented by the percentage of a subarray that is shaded in a single time step. For example, if a shadow covers 25% of a subarray at 11 AM, the shading loss at 11 AM is 25%; a shading loss of 0 means there was no shade on the subarray. ● Behind-the-meter: power from the system is used to reduce customers’ electricity bills; used in models for residential, commercial, and third-party ownership projects ● Front-of-meter: power from the system is sold for profit; used in models for power purchase agreements and merchant plant models ● LCOE, or Levelized Cost of Energy: the costs of the project and its energy production