predictive energy modeling with solarworld and pvsyst America s Authority on Solar

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1 predictive energy modeling with solarworld and pvsyst America s Authority on Solar

2 SolarWorld PVsyst Results 1 introduction As one of the largest and most established vertically integrated photovoltaics manufacturers on the planet, SolarWorld is intimately involved with every step of the solar PV value chain from raw silicon to installed systems to end-of-life recycling. This complete knowledgebase combined with our extensive history provides the critical insight required to lead the solar industry on technical topics. The purpose of this white paper is to discuss energy output projections for monocrystalline silicon photovoltaic SolarWorld Sunmodule Plus solar modules using predictive energy modeling. PAN files were created by Black and Veatch, a global engineering, consulting and construction company, and the test measurements were provided by PV Evolution Lab (PVEL), a leading third-party testing lab. The test measurements qualified the performance metrics of samples at multiple irradiance and temperature conditions in accordance with the IEC test standard. SolarWorld utilized this thirdparty validated information to carry out predictive modeling of the energy output for a sample PV system in several climates throughout the United States. Black & Veatch created a base case PAN file for the module using the datasheet and PVSyst defaults. After evaluating the fit of the base case PAN file efficiency curves to the measured efficiency curves, discrepancies were uncovered between the curves. PAN file input parameters were adjusted accordingly to reach the closest fit of the PVSyst modeled efficiency curves to the PVEL measured curves, which resulted in the final optimized PAN file. The predicted energy modeling that results from the optimized PAN files will provide the economic viability of a project, and drive the selection of the module, inverter and type of mounting system that will be used in a project.

3 SolarWorld PVsyst Results 2 PVSYST The predominant modeling program used in the United States is PVSyst. PVSyst has a database of profiles referred to as PAN files for every module produced in the world by all of the major manufacturers. These PAN file parameters can be accessed through the Photon Database for PV modules. There are two other means to access PAN files. Sometimes, the module manufacturer will create their own PAN files using the information included in their datasheet and their internal R&D results. The reliability of PAN files developed through this method is questionable since there is no third party involvement in the development of this data. The third method of developing PAN files is to engage third-party organizations to perform testing and use the data with predictive algorithms based on academic research and historical real-world performance data of the system. This third method will provide the most reliable data. These PAN files would also be provided by the module manufacturer but will state the methodology used and organizations involved in the third-party validation. The PV design software, PVSyst Version 5, has several module parameters that must be modified to accurately reflect the performance of a SolarWorld Sunmodule Plus module. These parameters are: NOCT Mismatch losses Power losses Temperature coefficients To determine the power output of the solar cell, it is important to determine the expected operating temperature of the PV module. The Nominal Operating Cell Temperature (NOCT) is defined as the temperature reached by open circuited cells in a module under the following conditions: 1. Irradiance on cell surface = 800 W/m 2 2. Air Temperature = 25 C 3. Wind Velocity = 1 m/s 4. Mounting = open back side Pre-Module Losses Power losses occur when the module does not deliver the power as stated in the datasheet, which is why manufacturers often provide a tolerance of up to ± 5%. SolarWorld s unique plus-sorting method ensures their modules deliver greater than or equal to nameplate-rated power thus ensuring that systems operate at top efficiency. Plus-sorting also eliminates mismatch losses that occur when cells or modules do not have identical properties. As a result, associated de-rate factors in system modeling programs such as PVSyst can be minimized. Shading is an important factor because partial shading can cause significance energy loss. Shadows may occur as result of modules being blocked by trees, chimneys, etc. Dirt may also may be the cause of some energy losses. In temperate regions where there is frequent rainfall, the losses could be as low as 1%. However, in arid regions with dust and only seasonal rainfall, the loss could be up to 25%. Snow does not typically have a very significant effect on system losses. However, depending on the location of the project, this element may need to be taken into consideration. Figure 1. PVSyst PAN File for SW 265 Wp.

4 SolarWorld PVsyst Results 3 Reflection effects of the module could increase with the angle of incidence and decrease with a large portion of diffused light. Module Losses Conversion losses are the nominal efficiency given by the manufacturer for standard conditions. Thermal losses will affect conversion losses directly. These losses depend on irradiance, mounting method, glass, thermal properties of materials and wind speeds. System Losses Wiring losses occur through cabling; all cable has some resistance and, as a result, some losses. MPP is the ability of the MPP tracker to consistently find the maximum power point which typically creates losses due to mismatch power of modules do not need to be accounted for in a SolarWorld system due to the consistency and reliability of the power output. Inverter efficiency is another factor that causes system losses. For example, if the inverter is undersized, power is clipped for high intensity light. If it is oversized, the inverter s efficiency will be too low for low intensity light. Transformer losses occur in cases that require electricity to be connected to a high-voltage grid. Operation & Maintenance Downtime for maintenance is usually very low for photovoltaic systems. Efficiency of Module By definition, operating efficiency of a solar module is the ratio between electric power delivered to the load and incident light intensity. It is affected by the four main factors of cells: temperature, sunlight intensity, sun angle and load. Energy yield and Performance ratio For investors and operators, there are two fundamental questions: 1. How much electricity does the system generate? 2. How well does the system perform? The value of a project is driven by the amount of energy that can be produced from the amount of power installed. The Energy Yield (kwh / kw) is the theoretical annual energy production on the AC side of the module, and only takes into account energy of incoming light and the module s nominal efficiency. Energy Yield is a great metric for evaluating system performance, and comparing predicted and actual energy produced by PV systems of differing size. The yield on energy has a direct impact on the financials of a project, and can be used to calculate the Economic Yield of the system kwh/ kw/$. Actual energy yield kwh produced kwp installed Installed cost = Economic yield The Performance Ratio is the ratio between actual yield based on real-world conditions or annual production of electricity delivered at AC and the target yield. The Performance Ratio essentially normalizes the Energy Yield for a given system over the irradiation measured at the location of the system. This allows an investor or EPC to compare systems that may differ in design, technology and geographic location. Also, by normalizing data with respect to actual irradiance, it quantifies the overall effect of losses on the rated output, which could be caused by inverter inefficiency, wiring, soiling, etc. Using real-world data to generate actual Performance Ratios provides increased confidence for investors in their selection of solar modules.

5 SolarWorld PVsyst Results 4 Actual energy yield kwh produced kwp installed Methodology Reference yield Measured irradiance Standard reference = Performance ratio As mentioned previously, PAN files are profiles of modules in PVSyst. Obtaining a validated PAN file is valuable for module manufacturers, owners, lenders, developers and EPC contractors. This new, validated module characterization file better quantifies various critical module performance curves over a wide range of irradiance and temperature conditions, and reduces risk and financial exposure for energy predictions. SolarWorld partnered with PV Evolutions to conduct IEC testing and Black & Veatch to modify PAN files and provide validation as a third-party engineering firm. For companies developing PV products and projects, PV Evolution Labs (PVEL) is the premier solar module performance and reliability testing lab. PVEL s calibrated equipment base is closely maintained to ensure optimal availability and reliability. Black & Veatch has been ranked by Engineering News-Record as the industry s No. 1 design firm in both Power and Telecommunications, and is consistently in the Top 10 in Water. They are also a leader in more than 20 categories among design firms, contractors and environmental companies worldwide. PV Evolution Labs (PVEL) randomly sampled five SW 255 mono modules from SolarWorld s inventory. The modules were placed in outdoor sunlight to promote light-induced degradation (LID). After calibrating the flash tester to the SolarWorld reference module, the five modules were flash-tested according to IEC , as well as their temperatures and irradiances with respect to Table 2 of the IEC specification. PV Evolution Labs (PVEL) contracted Black & Veatch to create a photovoltaic (PV) module characterization file, known as a PAN file, for use in PVSyst modeling. Black & Veatch took the following approach: 1. Measured Data: They processed raw measured data from PVEL and developed Measured efficiency curves for the 255 W module under certain irradiance and module temperatures. 2. Base Case PAN File: Then created a Base Case PAN file using parameters from the module datasheet and default values in PVSyst, and compared the resulting Base Case Modeled efficiency curves to measured efficiency curves from Step 1 to determine the extent of deviation. 3. Optimization: Finally, they adjusted PAN file parameters until modeled efficiency curves generated by PVSyst match the measured curves as closely as possible. The information from PVEL and Black & Veatch were provided to SolarWorld with technical details that are not included in this paper. If further information is needed, a more detailed report can be provided.

6 SolarWorld PVsyst Results Module Efficiency (%) Measured (scaled) data 4 2 Base case PAN file Optimized PAN file 0 Irradiance (W/m 2 ) Module Temp. (º C) Figure 2. Measured, Base Case and Optimized Efficiency Curve for the. 18 PV module: SolarWorld Module Efficiency (%) Cells temp = 10ºC Cells temp = 25ºC Cells temp = 50ºC Relative efficiency loss by respect to 1000 W/m 2 (at 25ºC) W/m 2, Eff = % 800 W/m 2, -1.3 % 4 Cells temp = 75ºC Cells temp = 90ºC 600 W/m 2, -3.1 % 400 W/m 2, -5.7 % W/m 2, % Incident global (W/m 2 ) Figure 3. PVSyst Efficiency Curves for the Base Case.

7 SolarWorld PVsyst Results 6 18 PV module: SolarWorld Module Efficiency (%) Cells temp = 1ºC Cells temp = 15ºC Cells temp = 25ºC Relative efficiency loss by respect to 1000 W/m 2 (at 25ºC) W/m 2, Eff = % 800 W/m 2, 0.4 % 4 Cells temp = 50ºC Cells temp = 75ºC 600 W/m 2, 0.5 % 400 W/m 2, -0.2 % W/m 2, -2.6 % Incident global (W/m 2 ) Figure 4. PVSyst Efficiency Curves for the Optimized PAN File. Modeling Analysis As stated previously, PVSyst is the predominant program that is being used in the United States. SolarWorld used PVSyst 5.57 to create the predicted energy model for monocrystalline modules. The purpose: to compare the module s performance in a location with high insolation. Module mismatch and module quality losses were used to define their PVSyst default values, which are based on a module s specified power tolerance in accordance with its specification datasheet. PVSyst Model: MW grid-connected project 2. High desert climate 3. The system is a single-axis tracker (N-S) with rotating phi of minimum -45 and maximum SMA 500 (Sunny Central 500-HE-US) inverter 5. NOCT values inserted in the model based on module s datasheet The following tables compare the monocrystalline with other SolarWorld competitors.

8 SolarWorld PVsyst Results 7 california, palmdale (62.42 F, ft/s) (latitude of 34.63, longitude of and altitude of 769 M above sea level). Type Number of modules 4,511 4,424 4,420 3,520 4,103 Total DC capacity (kwp) 1,026 1,026 1,018 1,042 1,017 Energy yield (kwh/kwp/yr) 2,335 2,262 2,305 2,321 2,274 Performance ratio Efficiency of the modules ,360 2,340 2,320 Energy yield (kwh/kwp/yr) Performance ratio 82.5% 82% 81.5% 81% 2, % 2,280 80% 2,260 2, % 79% 78.5% 2,220 78% Figure 5. Performance Ratio and Energy Yield for the 1 MW System in Palmdale, California.

9 SolarWorld PVsyst Results 8 The modules were also modeled in different climates; the states with similar radiation as Palmdale (California) were chosen from the map provided by NREL. Figure 6. United States Concentrating Solar Power Resource: Direct Normal. The following tables represent predicted energy modeling of monocrystalline in the selected states. New Jersey, Teteboro (53.78 F, ft/s) (latitude of 40.85, longitude of and altitude of 3 M above sea level). Type Number of modules 4,508 4,424 4,420 1,151 4,103 Total DC capacity (kwp) 1,026 1,026 1,018 1,042 1,017 Energy yield (kwh/kwp/yr) 1,379 1,324 1,358 1,354 1,330 Performance ratio Efficiency of the modules ,390 1,380 1,370 1,360 Energy yield (kwh/kwp/yr) Performance ratio 87% 86% 85% 1,350 1,340 1,330 84% 83% 1,320 1,310 1,300 82% 81% 1,290 80% Figure 7. Performance Ratio and Energy Yield for the 1 MW System in Teteboro, New Jersey.

10 SolarWorld PVsyst Results 9 oregon, portland (52.52 F, 7.22 ft/s) (latitude of 45.53, longitude of and altitude of 62 M above sea level). Type Number of modules 4,508 4,424 4,420 3,520 4,103 Total DC capacity (kwp) 1,026 1,026 1,018 1,042 1,017 Energy yield (kwh/kwp/yr) 1,417 1,364 1,396 1,394 1,362 Performance ratio Efficiency of the modules ,430 1,420 1,410 Energy yield (kwh/kwp/yr) Performance ratio 86% 85% 1,400 1,390 84% 1,380 83% 1,370 1,360 82% 1,350 13,40 81% 1,330 80% Figure 8. Performance Ratio and Energy Yield for the 1 MW System in Portland, Oregon.

11 SolarWorld PVsyst Results SW US-PVS florida, orlando (71.78 F, ft/s) (latitude of 28.55, longitude of and altitude of 33 M above sea level). Type Number of modules 4,508 4,424 4,420 3,520 4,103 Total DC capacity (kwp) 1,026 1,026 1,018 1,042 1,017 Energy yield (kwh/kwp/yr) 1,710 1,636 1,677 1,686 1,639 Performance ratio Efficiency of the modules ,720 83% 1,700 Energy yield (kwh/kwp/yr) Performance ratio 82% 1,680 81% 1,660 1,640 80% 1,620 79% 1,600 78% 1,580 77% Figure 9. Performance Ratio and Energy Yield for the 1 MW System in Orlando, Florida. As is shown through the test results against competitive modules, efficiency of a module should never be looked at to solely predict the actual performance of a solar system. SolarWorld has put over 35 years of real world experience into designing our modules to provide the best results. Even against systems designed with higher powered, larger modules, the SolarWorld module consistently outperforms in energy yield which is in fact, the most important measurement when looking at the bankability and financial viability of a solar system. And the 3rd party verification by impartial, reputable organizations further mitigates any risk of poor system performance that installers, financing partners and system owners are concerned about. As you can see from the information shared in this white paper, not all solar is created equal. The innovations in manufacturing and technological advancements put into SolarWorld modules delivers superior performance time and time again.