Module |

| To view the Module page, click Module on the main window's navigation menu. Note that for the Module page to be available, the technology option in the Technology and Market window must be Photovoltaics - SAM Performance Models.
| Overview
The Module page allows you to choose a photovoltaic module performance model from four options:
• | Simple Efficiency Module
• | CEC Performance Model
• | Sandia PV Array Performance Model
• | Concentrating PV Module
Note. To model a photovoltaic system using the PVWatts model, you must choose PVWatts System Model in the Technology and Market window. To specify a photovoltaic module model:
1. | Choose the model name from the list.
2. | For the Sandia or CEC models, choose a module from the database of available models.
For the simple efficiency model and concentrating PV Module, enter module characteristics. Each of the four module performance models calculates the hourly DC electrical output of a single module based on the hourly incident solar radiation (plane-of-array irradiance) calculated by the Climate model using data in the weather file and array orientation and tracking information from the Array page. The photovoltaic array output depends on the number of modules and the pre-inverter derate factor specified on the Array page. Solar Advisor passes the array's hourly DC power output to the inverter model, whose characteristics appear on the Inverter page. Note. Solar Advisor does not track voltage and current levels in the system and assumes that the array operates at its maximum power point. Each model uses a different algorithm to predict module performance. In general, if you are modeling a system that uses a particular brand and type of flat-plate PV module, you should first look for the module in the Sandia database, and then in the CEC database. If you do not find the module in either database, you can either choose a similar module, or use the simple efficiency model. The simple efficiency and concentrating PV models are ideal for analyses involving explorations of the relationship between module efficiency and the system's performance and cost of energy. Both models allow you to define a curve of the module's efficiency versus incident radiation. The Sandia and CEC models do not allow you to modify the module parameters, although advanced users with and understanding of the model algorithms can add their own modules to the database.
• | The Sandia PV Array Performance Model calculates hourly efficiency values based on data measured from modules and arrays in realistic outdoor operating conditions. The Sandia model tends to produce more accurate predictions of module performance than the CEC model. However, because of the time and effort required to make the field measurements, the Sandia module database is less up-to-date than the CEC database.
• | The California Energy Commission (CEC) Performance Model predicts module performance based on a database of module characteristics determined from module ratings. Like the Sandia model, the CEC model calculates hourly efficiency values, and allows you to select from a list of a commercially-available modules. The CEC module database tends to be more up-to-date than the Sandia database. For some types of modules, the CEC model predictions may be less accurate than the Sandia model.
• | The Simple Efficiency Module model is a simple representation of module performance that requires you to provide the module area, a set of conversion efficiency values, and temperature correction parameters. The simple efficiency model is the least accurate of the three models for predicting the performance of specific modules. It is useful for preliminary performance predictions before you have selected a specific module, and allows you to specify a module efficiency and temperature performance parameters, which is useful for analyses involving sensitivity or parametric analysis.
• | For concentrating photovoltaic (CPV) modules, use the concentrating PV Module model unless you are modeling one of the concentrating modules available in the Sandia model, in which case, you can choose the module from the database in the Sandia model. The concentrating PV module model is similar to the simple efficiency model, except that it uses only the direct normal component of the incident solar radiation instead of the total radiation for performance predictions.
Table 9. Guidelines for choosing a photovoltaic module performance model.
Use this model... | ...if your analysis involves... | Comments
Sandia Model based on field test data. | estimates of module performance for crystalline or thin-film modules. | If your module is in both the Sandia and CEC lists, use the Sandia model.
CEC Model based on module ratings. | estimates of module performance for crystalline-silicon modules or for new modules recently available on the market. | Use the CEC model when your analysis involves a particular module that is not available in the Sandia database.
Simple Efficiency Module Simple efficiency curve with temperature correction. | sensitivity or parametric studies on module efficiency or temperature coefficients, or for preliminary analyses before you have chosen a specific module. |
Concentrating PV Module Simple efficiency curve with temperature correction. | Modeling concentrating photovoltaic modules. | See Modeling Concentrating Photovoltaic (CPV) Modules for details.
| Sandia PV Array Performance Model
The Sandia PV Array Performance Model uses an algorithm and a database of commercially available modules developed at Sandia National Laboratories. The Sandia model is described in King et al, 2004. Photovoltaic Array Performance Model. Sandia National Laboratories. SAND2004-3535. http://photovoltaics.sandia.gov/docs/PDF/King%20SAND.pdf To use the Sandia photovoltaic model:
1. | On the Module page, choose Sandia PV Array Performance Model.
2. | Choose a module from the list of available modules. Solar Advisor displays the module's characteristics and model coefficients.
When you choose a module from the list, Solar Advisor displays the module characteristics at reference conditions on the Module page. Internally, the model applies a set of coefficients from the Sandia Modules library to the simulation equations.
1. | Choose a module structure from the three available options (displayed as front material / cell / back material). See Temperature Correction for details. Module manufacturers typically include a description of the front material, and frame or back material in a mechanical characteristics section of module specification sheets.
Note. The current version of the database contains a single concentrating PV module, listed as Entech 22X Concentrator [1994]. The Sandia model consists of a set of equations that provide values for five points on a module's I-V curve and a database of coefficients for the equations whose values are stored in the Sandia Modules library. The coefficients have been empirically determined based on a set of manufacturer specifications and measurements taken from modules installed outdoors in real, operating photovoltaic systems. Note. If you are a module manufacturer and would like to add your module to the Sandia database, you should contact Sandia National Laboratories directly. Modeling Arrays The first several items in the list are arrays instead of single modules. The arrays are indicated by the word "Array" in the name. The array coefficients account for some losses not accounted for in the single module parameters, including module mismatch, diodes and connections, and DC wiring losses. When you use an array from the database, you should be sure that the Pre-Inverter derate factor on the Array page does not include these losses. Modeling Thin-film Modules For modules based on thin-film cell technology, including amorphous silicon, copper indium diselenide (CIS), cadmium telluride (CdTe), and heterojunction with intrinsic thin layer (HIT), the Sandia model may provide more accurate results than the CEC and simple efficiency models, which do not adequately represent module performance at low-light levels. For best results, if you are modeling a thin-film module, look for the module in the Sandia database. If the module is not available in the Sandia database, you may want to use a module from the database with similar characteristics to the one you are modeling. Use the table below to help identify the thin-film modules in the Sandia database. Table 10. Thin-film module manufacturers and model numbers available in the Sandia module database.
Cell Type | Manufacturer | Model Series or Number
amorphous tandem junction (2-a-Si) | Solarex | MST
amorphous silicon triple junction (3-a-Si) | Uni-Solar | PVL, SHR, US, USF
cadmium telluride (CdTe) | BP Solar | BP980, BP990
First Solar | FS
copper indium diselenide (CIS) | Shell Solar | ST
Siemens Solar | ST
amorphous silicon heterojunction (HIT-Si) | Sanyo | HIP
Module Characteristics at Reference Conditions Solar Advisor displays the module characteristics so that you can compare modules in the database to manufacturer specifications or to different modules in the database. Reference Conditions The reference conditions describe the incident solar radiation, air mass, ambient temperature, and wind speed that apply to the module characteristics. The module efficiency, power, current, voltage, and temperature coefficients values are those for the module operating at the reference conditions. Efficiency (%) The module's rated efficiency at reference conditions. Solar Advisor displays this value for reference only. During simulations, the model calculates an efficiency value for each hour, which you can see in the hourly output data. Maximum Power, P_mp (Wdc) The module rated power in DC Watts. Equal to the product of the maximum power voltage and maximum power current. Maximum Power Voltage, V_mp (Vdc) Maximum power voltage in DC Volts under reference conditions. Maximum Power Current, I_mp (Adc) Maximum power current in DC Amps under reference conditions. Defines the maximum power point on the module's I-V curve. Open Circuit Voltage, V_oc (Vdc) Open circuit voltage under reference conditions. Defines the open circuit point on the module's I-V curve. Short Circuit Current, I_sc (Adc) Short circuit current under reference conditions. Defines the short circuit point on the module's I-V curve. Temperature Coefficients Solar Advisor displays the temperature coefficients in %/°C and W/°C at the different points on the power curve. Module Structure and Mounting This option determines the coefficients that Solar Advisor uses to calculate the cell temperature in each hour of the simulation. The default option is User Database Values, which displays the coefficients from the measured data at reference conditions. See Temperature Correction for details. Physical Characteristics Material A description of the semiconductor technology used in the photovoltaic cells.
2-a-Si | dual-junction amorphous silicon
3-a-Si | triple-junction amorphous silicon
CdTe | cadmium-telluride
CIS | copper indium diselenide
HIT-Si | amorphous silicon heterojunction
c-Si | single-crystal silicon
mc-Si | multi-crystalline silicon
Vintage The year that module coefficients were added to the database. The letter "E" indicates that the coefficients were estimated from a combination of published manufacturer specifications and data from the outdoor testing of a similar module. Entries without an "E" are for modules whose coefficients were derived entirely from outdoor tests involving one more or more modules of that type. Because the tested modules (listed without an "E") may have had different average power ratings than production versions of the same module, the database typically also includes an "E" entry for each of the tested modules that represents the average power rating specified by the manufacturer. Module Area (m 2) The total area of the module, including spaces between cells and the frame. Number of Cells Total number of cells per module, equal to the product of the number of cells in series and number of cell strings in parallel. Number of Cells in Series Number of cells connected in series per cell string. Number of Cell Strings in Parallel Number of cell strings connected in parallel per module. References A link to King et al, 2004. Photovoltaic Array Performance Model. Sandia National Laboratories. SAND2004-3535 document describing the Sandia PV Array Performance Model in detail. You can find links to more documents in References.
| CEC Performance Model
The California Energy Commission (CEC) Performance Model uses the University of Wisconsin-Madison Solar Energy Laboratory's five-parameter model with a database of module parameters for modules from the database of eligible photovoltaic modules maintained by the California Energy Commission (CEC) for the California Solar Initiative. The five-parameter model is described in brief in De Soto 2003, "Improvement and Validation of a Model for Photovoltaic Array Performance," Solar 2003 Conference Proceedings, American Solar Energy Society. A more detailed description can be found in De Soto 2004, Improvement and Validation of a Model for Photovoltaic Array Performance, Master of Science Thesis, University of Wisconsin-Madison. http://sel.me.wisc.edu/theses/desoto04.zip. For information about the CEC list of eligible photovoltaic modules, see http://www.gosolarcalifornia.org/equipment/pvmodule.html. To use the CEC photovoltaic model:
1. | On the Module page, choose CEC Performance Model.
2. | Choose a module from the list of available modules. Solar Advisor displays the model's characteristics and model coefficients.
When you select a module from the CEC database on the Module page, Solar Advisor displays module's parameters. You can see the complete set of parameters in the Module library by using Solar Advisor's library editor. Note. To make sure that you have the latest CEC module library, on the Help menu, click Check for updates. Solar Advisor will connect to NREL servers on the Internet and, if a more recent version of the library is available, automatically update your current library. Updating the library only affects the standard CEC module library, and will not affect any modules you may have added to the library. The five-parameter model calculates a module's current and voltage under a range of solar resource conditions (represented by an I-V curve) using an equivalent electrical circuit whose electrical properties can be determined from a set of five parameters. These five parameters, in turn, are determined from standard reference condition data provided by either the module manufacturer or an independent testing laboratory, such as the Arizona State University Photovoltaic Testing Laboratory. Note. If you are a module manufacturer and would like to add your module to the CEC database, you should contact the CEC directly. If you would like to add a module to the CEC module library in your copy of Solar Advisor, please contact us at solar.advisor.support@nrel.gov. If you can provide us with a list of the module's specifications as shown on the Module page under Module Characteristics, we may be able to create a set of coefficients for you to use. We provide this service on a case-by-case basis, and cannot guarantee the quality of the coefficients we generate. The parameters in the CEC module library include:
• | A set of module characteristics at standard test conditions, which may be provided by either the module manufacturer or by an independent testing laboratory.
• | A set of additional parameters used in the model's equivalent circuit to calculate the module's I-V curve.
• | Reference inputs required to generate the calculated model parameters.
Module Characteristics at Reference Conditions Efficiency (%) The module's rated efficiency at reference conditions. Solar Advisor displays this value for reference only. During simulations, the model calculates an efficiency value for each hour, which you can see in the hourly output data. Maximum Power, P_mp (Wdc) The module rated power. Equal to the product of the maximum power voltage and maximum power current. Maximum Power Voltage, V_mp (V) Reference maximum power voltage at the reference conditions. Maximum Power Current, I_mp (A) Reference maximum power current at the reference conditions. Open Circuit Voltage, V_oc_ref (V) Reference open circuit voltage at the reference conditions. Short Circuit Current, I_sc_ref (A) Reference short circuit current at the reference conditions. Number of Cells Total number of cells per module. Temperature Coefficients Solar Advisor displays the temperature coefficients in %/°C and W/°C at maximum power, open circuit, and short circuit. Physical Characteristics Material A description of the semiconductor technology used in the photovoltaic cells.
1-a-Si | single-junction amorphous silicon
2-a-Si | dual-junction amorphous silicon
3-a-Si | triple-junction amorphous silicon
a-Si/nc | amorphous silicon - microcrystalline silicon tandem module
CdTe | cadmium-telluride
CIGS | copper indium gallium sulfide
CIS | copper indium diselenide
HIT-Si | amorphous silicon heterojunction
Mono-c-Si | single-crystal silicon
Multi-c-Si | multi-crystalline silicon
Module Area The total area of the module, including spaces between cells and the frame. Number of Cells Number of cells per module. Reference Conditions T_Amb_NOCT Ambient temperature at NOCT T_REF Module temperature at reference conditions FFV_Wind Correction factor for wind speed (FFV_wind = 0.51 if lowest part of the array is less than 22 feet from the ground FFV_wind = 0.61 if lowest part of the array is 22 feet or more from the ground) I_NOCT Irradiance at NOCT I_REF Irradiance at reference conditions Tau_alpha Transmittance-absorptance product KL Extinction coefficient Eta_MPPT Maximum power point correction factor E_G Band gap at reference temperature Additional Parameters T_NOCT Cell temperature at NOCT A_REF Modified ideality factor at reference conditions I_L_REF Photocurrent at reference conditions I_O_REF Reverse saturation current at reference conditons R_s Series resistance (constant) R_sh_ref Shunt resistance at reference conditions References A link to De Soto W, 2004. Improvement and Validation of a Model for Photovoltaic Array Performance. Master of Science Thesis. University of Wisconsin-Madison. http://sel.me.wisc.edu/theses/desoto04.zip. You can find links to more documents in References.
| Simple Efficiency Module
The flat-plate photovoltaic simple efficiency module model calculates the module's hourly DC output assuming that the module efficiency varies with radiation incident on the module as defined by the radiation level and efficiency table. The model makes an adjustment for cell temperature, See Temperature Correction for details. To use the simple efficiency module model:
1. | On the Module page, choose Simple Efficiency Module.
2. | Enter a temperature coefficient. This is the number typically reported on manufacturer specification sheets as the maximum power coefficient. See Temperature Correction for suggested values.
3. | Choose a module structure from the three available options (displayed as front material / cell / back material). See Temperature Correction for details.
Module manufacturers typically include a description of the front material, and frame or back material in a mechanical characteristics section of module specification sheets.
4. | Enter the module's total cell area in square meters, equivalent to the product of the cell area and number of cells.
5. | In the Radiation Level and Efficiency Table, enter an efficiency value for each of the five incident global radiation reference values in increasing order. If you are defining the efficiency curve with fewer than five efficiency values, you must include five radiation values, but you can assign the same efficiency value to more than one radiation value. For example, to represent a module with 13.5% constant efficiency, you would assign the value 13.5 to each of the five radiation values 200, 400, 600, 850, 1000.
6. | Choose the radiation level that represents the reference value, often 1000 W/m 2 for flat-plate modules.
Solar Advisor uses the reference value to calculate the module's rated power, displayed as the Power variable on the Module page. Characteristics The module characteristics define the module's capacity, efficiency, and thermal characteristics. Maximum Power, Pmp (Wdc) The module's rated maximum DC power at the reference radiation indicated in the radiation level and efficiency table. Solar Advisor uses this value to calculate the array cost on the PV System Costs page, but not in simulation calculations. The module power is the product of the reference radiation, reference efficiency, and area. Temperature Coefficient, Pmp (%/°C) The rated maximum-power temperature coefficient as specified in the module's technical specifications. See Temperature Correction for details. Area (m 2) The module collector area in square meters. To calculate the area for a given module power rating at a given reference radiation level, divide the power rating by the module efficiency and radiation level. For example, a module with a 100 W rating and 13.5% efficiency at 1000 W/m 2 would requires an area of 100 W / (0.135 × 1000 W/m 2) = 0.74074 m 2. Module Structure and Mounting The module's front and back materials (front material/cell/back material) used in the temperature correction algorithm described below. See Temperature Correction for details. Radiation Level and Efficiency Table Radiation (W/m2) The incident global (beam and diffuse) radiation level at which the given efficiency value applies. Efficiency (%) The module conversion efficiency at a given incident global radiation level. Solar Advisor calculates an efficiency value for each hour in the simulation using linear extrapolation to determine the value based on radiation data from the weather file. The efficiency values represent the efficiency of conversion from incident global radiation to DC electrical output. Reference Indicates the value to use for the reference calculations. Solar Advisor uses the reference values to calculate the module's rated power on which module costs are based. For each hour of the year, the flat-plate single-point efficiency model calculates the module DC output as the product of the total incident global radiation, module area, and temperature correction factor: Where,
E TotalIncident (W/m 2) | Total incident radiation from the Climate model.
A Module (m 2) | The module area in square meters.
η Module | Module efficiency at a given incident global radiation level, calculated by extrapolating values from the Radiation Level and Efficiency Table.
F TempCorr | Temperature correction factor. See Temperature Correction for details.
| Concentrating PV Module
The Concentrating PV Module model uses a simple algorithm that calculates the module's hourly DC output by multiplying the hourly direct normal component of the solar radiation data from the weather file by the module's area and efficiency as specified on the Module page, and makes a correction for the cell's temperature. Note. If you are modeling the Entech 22X Concentrator (c-Si), you can use the Sandia PV Array Performance model instead of the Simple Efficiency model. The Entech module is modeled using a set of coefficients determined by analyzing field test measurements. To use the Entech module, choose the Sandia model option and select the Entech 22X Concentrator [1994] module from the list of available modules. To use the Concentrating PV module model:
1. | On the Module page, choose Concentrating PV Module.
2. | Enter a temperature coefficient. This is the number typically reported on manufacturer specification sheets as the maximum power coefficient. See Temperature Correction for suggested values.
3. | Enter the module's total collector area in square meters.
4. | If you have a set of temperature correction coefficients, enter values for a, b, and dT. If you do not have a set of values, use the default values (click Default Temperature Inputs to populate the variables with their default values). See Temperature Correction for details.
5. | In the Radiation Level and Efficiency Table, enter an efficiency value for each of the five incident global radiation reference values in increasing order. If you are defining the efficiency curve with fewer than five efficiency values, you must include five radiation values, but you can assign the same efficiency value to more than one radiation value. For example, to represent a module with 20% constant efficiency, you would assign the value 20 to each of the five radiation values 200, 400, 600, 850, 1000.
Concentrating PV Module Characteristics Maximum Power, Pmp (Wdc) The module's rated maximum DC power at the reference radiation value indicated in the efficiency table below. Solar Advisor uses this value to calculate the array cost shown on the PV System Costs page, but not in simulation calculations. The rated module power is the product of the reference radiation, reference efficiency and area. Temperature Coefficient, Pmp (%/°C) The rated maximum-power temperature coefficient as specified in the module's technical specifications. The default value is -0.15. See Temperature Correction for details. Area (m 2) The module collector area in square meters. a, b, and dT Temperature correction coefficients, a=-3.2, b=-0.09, dT=17 by default. See Temperature Correction for details. Default Temperature Inputs Resets the a, b, and dT coefficients to their default values. Radiation Level and Efficiency Table Radiation (W/m2) The incident beam radiation level at which the given efficiency value applies. Efficiency (%) The module conversion efficiency at a given incident global radiation level. Solar Advisor calculates an efficiency value for each hour in the simulation using linear extrapolation to determine the value based on radiation data from the weather file. The efficiency values represent the efficiency of conversion from incident global radiation to DC electrical output. Reference Indicates which value to use for the reference calculations. The module's hourly DC output is the product of the hour's direct normal solar radiation from the weather file as defined on the Climate page, collector area, and module efficiency from the Module page: Where,
P mp,CPVModule (Wdc) | The module's average DC electric output for the hour.
E DirectNormal (W/m 2) | The direct normal solar radiation from weather processor.
A Collector (m 2) | The collector area in square meters.
η Module | The module's conversion efficiency at the incident beam radiation for the current hour, extrapolated from the efficiency curve defined by the table on the Module page.
F TempCorr | Temperature correction factor. See Temperature Correction for details.
| Temperature Correction
The Sandia, Simple Efficiency, and Concentrating PV models all use the temperature correction algorithm originally developed for the Sandia model to calculate a temperature correction factor that accounts for efficiency losses due to heating of the module during the day when the sun is shining. The algorithm calculates an hourly module temperature as a function of the solar radiation, ambient temperature, and wind speed in a given hour. The algorithm uses a set of three coefficients (a, b, and dT, described below), whose values depend on the module's construction and how air circulates around the module when it is installed in the system. For more details about the algorithm, see King et al, 2004. Photovoltaic Array Performance Model. Sandia National Laboratories. SAND2004-3535. http://photovoltaics.sandia.gov/docs/PDF/King%20SAND.pdf The CEC model uses a different temperature correction algorithm. For a description of the CEC temperature correction approach, see De Soto 2004, Improvement and Validation of a Model for Photovoltaic Array Performance, Master of Science Thesis, University of Wisconsin-Madison. http://sel.me.wisc.edu/theses/desoto04.zip. Note. The Solar Advisor temperature correction algorithms do not account for cooling strategies used in some innovative photovoltaic systems. Temperature Correction for Sandia, Simple Efficiency, and Concentrating PV Models Solar Advisor uses the method described below to calculate a module and cell temperature and temperature correction factor for the Sandia, Simple Efficiency and Concentrating PV models. The model uses the temperature correction factor to adjust each hour's module efficiency value: The higher the module's temperature in a given hour, the lower the module's efficiency in that hour. You can explore temperature effects on the array's performance in the hourly output data. The data shows the hourly cell temperature, along with the solar radiation, wind speed, and ambient temperature. The temperature correction equations use the following input values from the Module page:
• | Temperature coefficients. The Sandia model uses the four values listed in the Temperature Coefficients column. The Simple Efficiency and Concentrating PV models use the single temperature coefficient of power value.
• | Temperature correction coefficients: a, b, and dT. For the Sandia and Simple Efficiency models, the three values appear under the Module Structure - Mounting option. For the Concentrating PV model, the values appear below the temperature coefficient variable.
The equations use four hourly data sets from the weather file. You can see the hourly data by either viewing the climate data from the Climate page, or viewing the hourly results data after running simulations:
• | Incident direct normal radiation
• | Incident diffuse radiation
• | Ambient temperature
• | Wind speed
Guidelines for choosing the Module Structure - Mounting option for the Sandia and Simple Efficiency models:
• | For most analyses involving modules mounted on open racks, choose Use Database Values. These are the values determined empirically during testing of the module. Most of the modules in the database were tested on open racks.
• | Choose a different option to see how the module would perform under different mounting conditions. Be sure to choose a module structure and mounting option that is consistent with the module you are modeling. You may need to refer to the module's specification sheet for information about its structure.
• | If you understand the Sandia model well enough to generate your own temperature correction coefficients, choose User Defined, and type your own values for the three coefficients.
Table 11. Description of the module structure and mounting options.
Module Structure and Mounting | Description
Glass/Cell/Polymer Sheet Open Rack | Solar cells are between a glass front and polymer back, and the module is mounted on an open rack allowing air to circulate freely around the module.
Glass/Cell/Glass Open Rack | Solar cells are between a glass front and glass back, and the module is mounted on an open rack allowing air to circulate freely around the module.
Polymer/Thin Film/Steel Open Rack | Solar cells are between a transparent polymer front and steel back, and the module is mounted on an open rack allowing air to circulate freely around the module.
Glass/Cell/Polymer Sheet Insulated Back | Solar cells are between a glass front and polymer back, and the module is mounted directly to a building surface in a building-integrated PV (BIPV) application preventing air from flowing over the module back.
Glass/Cell/Glass Close Roof Mount | Solar cells are between a glass front and glass back, and the module is mounted on a rack with little clearance between the building surface and module back allowing little air to flow over the module back.
Table 12. Empirically-determined coefficients from the Sandia database for each of the module structure and mounting options available on the Module page.
Module Structure and Mounting | a | b | dT ºC
Glass/Cell/Polymer Sheet Open Rack | -3.56 | -0.0750 | 3
Glass/Cell/Glass Open Rack | -3.47 | -0.0594 | 3
Polymer/Thin Film/Steel Open Rack | -3.58 | -0.113 | 3
Glass/Cell/Polymer Sheet Insulated Back | -2.81 | -0.0455 | 0
Glass/Cell/Glass Close Roof Mount | -2.98 | -0.0471 | 1
Table 13. Sample temperature coefficient values for different cell types based on an informal survey of manufacturer module specifications.
Cell Type | Maximum Power Temperature Coefficient (%/°C)
Monocrystalline Silicon | -0.49
Polycrystalline Silicon | -0.49
Amorphous Silicon | -0.24
Amorphous Silicon Triple Junction | -0.21
Copper Indium Gallium DiSelenide (CIGS) | -0.45
Cadmium Telluride (CdTe) | -0.25
The temperature correction algorithm first calculates the module back temperature based on the incident solar radiation, a and b coefficients, and the ambient temperature and wind speed: Next, the cell temperature is calculated based on the module back temperature, incident radiation, and dT: The temperature correction factor F TempCorr is: Where,
E Incident (W/m 2) | The sum of the direct normal and diffuse radiation for the current hour in the weather data. Solar Advisor determines this value based on the data in the weather file.
E 0 (W/m 2) | The reference total incident radiation, equal to 1000 W/m 2.
T ref (°C) | The reference temperature in degrees Celsius, equal to 25°C.
γ (%/°C) | The maximum power temperature coefficient from Module page.
a, b | Values from the Module page. They are empirically-determined coefficients accounting for the effect of wind on the module temperature: a defines the module temperature upper limit (at low wind speed and high solar radiation levels), and b defines the rate at which module temperature decreases as wind speed increases. The values depend on the module's construction, which determines its ability to absorb and shed heat. See the table above for typical values.
dT | Value from the Module page. The temperature difference between the cell and module back surface at the reference incident radiation of 1000 W/m 2. The value depends on how the module is mounted in the system, which determines how much air comes into contact with the module back surface. See the table above for typical values.
v Wind (m/s) | Wind speed from the weather file in meters per second.
T Ambient (°C) | Ambient temperature from weather file.