Solar Simulation Systems
Photo Emission Tech., Inc., manufactures and markets cell testers and solar simulation systems that are also known as sun simulator that provide full spectrum light equivalent to the sunlight. The primary applications of these solar simulators are checking Photovoltaic Cell performance, materials testing, photo-lithography, cosmetic testing and in any other application where the effect of exposure to sun light needs to be studied, such as photochemistry/photobiology testing and environmental exposure testing. Seven standard solar simulators models are available for each class that serves these markets. Solar simulator systems can be manufactured with three different air mass (AM) filters: AM0, AM1 and AM1.5. These solar simulators meet Class A requirements of ASTM E927-2010, IEC60904-9 Edition 2.0 2007-10 and JIS C 8912-1998: amendment 1-2005 & Amendment 2-2011.
The ground level spectrum of natural sunlight is different for various locations on earth. The constituents of the atmosphere affect both absorption and scattering. Elevation is another factor that affects the ground level spectrum, since the elevation determines how far the sun's radiation must pass through the atmosphere. For any given location the distance the sun's radiation must travel through the atmosphere changes as the day progresses, due to the changing angle of the sun. With the sun directly overhead the direct radiation that passes through travels the shortest distance through earth's atmosphere to reach the earth. The spectrum of this radiation is referred to as "Air Mass 1 Direct" (AM1D). For standardization purposes sea level is used as a standard reference site. The global radiation with the sun overhead is referred to as "Air Mass 1 Global" (AM1G). The spectrum of sun's radiation in space does not pass through any air mass hence it is referred to as "Air Mass 0" (AM0).
Since solar radiation reaching the earth's surface varies significantly with atmospheric condition, location, time of the day, earth/sun distance, and solar activity, standard spectra have been developed to provide a basis for standardization of theoretical evaluation of the effects of solar radiation. The most widely used standard spectra are those published by The Committee Internationale d'Eclaraige (CIE), the world authority on radiometric and photometric nomenclature and standards.
The American Society of Testing and Materials (ASTM) has published three spectra, AM0, AM1.5 Direct and AM 1.5 Global for a 37° tilted surface. The conditions for the AM 1.5 spectra were chosen by ASTM because they are representative of average conditions in the 48 contiguous states of the United States. In addition to the standards for different air masses, standards for Non-Uniformity, Temporal Instability of Irradiance, Total Irradiance within 300 Field of View, and how closely the system's radiation spectral distribution matches the sun's radiation have been established by various organizations. In the USA, American Society for Test and Measurement (ASTM) has established such standards for Solar Simulators.
PET Solar Simulators consist of a Light Source with a built-in Lamp Power Supply. The Solar Simulator has an ellipsoidal reflector that surrounds the lamp and collects most of the lamp output. The radiation from the lamp is focused onto an optical integrator that helps produce a uniform diverging beam. The beam is diverted 90° by a mirror onto a collimating lens. Special filters are placed between the mirror and the collimating lens to shape the radiation spectra to match various air masses. The output is a uniform beam that closely matches the sun's radiation spectra for a given air mass. Various models offer different areas of illumination. Each model can be manufactured to simulate the sun's radiation for different air masses.
The power supply unit provides constant electrical power to the xenon arc lamp. All of our systems come with a standard closed loop light intensity controller. This helps in assuring very stable light intensity. In addition the power supply unit houses control circuitry for several control features. Some of the control features are discussed here.
Light Intensity & Control
Photovoltaic Cell Performance
Environmental Exposure Testing
SOLAR SIMULATOR MODELS
SS30AAA-TP & SS30AAA-EM
SS50AAA-TP & SS50AAA-EM
SS80AAA-TP & SS80AAA-EM
SS100AAA-TP & SS100AAA-EM
SS150AAA-TP & SS150AAA-EM
SS200AAA-TP & SS200AAA-EM
SS300AAA-TP & SS300AAA-EM
SS400AAA-TP & SS400AAA-EM
STANDARDS FOR SOLAR SIMULATORS
Three international organizations have defined the standards for solar simulators. These organizations and the standard for solar simulators are:
- American Standards for Test and Measurement (ASTM, standard reference # E927 – Standard Specifications for Solar Simulation for Terrestrial Photovoltaic Testing) has defined American standards.
- International Engineering Consortium (IEC, standard reference # IEC 60904-9 – Solar simulator performance requirements) has defined the European standards.
- Japanese Standards Association (JSA) has defined Japanese Industrial Standards (JIS C 8912 – Solar Simulators for Crystalline Solar Cells and Modules, and JIS C 8933 - Solar Simulators for Amorphous Solar Cells and Modules) for Japan.
All of these standards are very similar. Following is an overview of the three standards.
There are three classes of systems defined:
- Class A
- Class B
- Class C
Each class defines the following properties of the light beam and how well it matches the properties of the sun light:
- Total Intensity in a specific range of wavelengths (400-1,100nm for AM1.5G)
- Temporal instability of irradiance
- Non Uniformity of Total irradiance
- Spectral match to sun light within a given range for each Air Mass
Table: Solar Simulator International Standards Summary
In order to classify a Solar Simulator as a “Class A” system, it must meet all three requirements specified under Class A, i.e. the non-uniformity of the irradiance over the area of illumination must be ≤2%, and the Short Term Temporal Instability of irradiance must be ≤0.5% and the Long Term Temporal Instability (LTI) of irradiance must be ≤2%, and the spectral match in each wavelength interval must be ±25% or better. In addition, the total intensity must be 1,000W/m2 (100mW/cm2) for AM1.5G.
All three standards allow the classification of a solar simulator with three letters, such as AAB etc, where the first letter in the class designation refers to the spectral match of the class of a system, second letter in the class designation refers to the system class for Spatial Non-uniformity of irradiance and the third letter in the class designation refers to the system class for Temporal Instability of Irradiance of the system. The standard also allows a single letter designation. For example a Class A signifies that the solar simulator meets all three requirements of class A and is the same as Class AAA.
All PET Solar Simulators are class AAA meeting all three international standards. All systems are tested to the strictest of the three (3) International Standards. For example, European Standard IEC 60904-9 requires 64 test point measurement of Spatial Non-Uniformity as compared with 36 test points required by American Standard ASTM E927 or 17 test points required by Japanese Standard JIS C8912, PET Solar Simulators and Cell Testers are tested for using 64 test points to measure and calculate the Spatial Non-Uniformity. Similarly, European Standard IEC 60904-9 requires the Short Term Instability of Irradiance (STI) to be measured and reported. PET Solar Simulators and Cell Testers are tested for STI and LTI requirements of IEC 60904-9. A signed report is delivered with each system certifying the classification of the Solar Simulator or Cell Tester. See for our website for a sample report issued with our Solar Simulators or Cell Testers.
TYPICAL FINAL TEST REPORT
A report similar to the typical final test report shown below is delivered with each Cell Tester or Solar Simulator to certify that the Cell Tester or the Solar Simulator meets or exceeds all the criteria of the Class AAA requirements of ASTM E927-2010, IEC60904-9 Edition 2.0:2007-10 and JIS C 8912-1998: amendment 1-2005 & Amendment 2-2011AAA system. Pages 1 through 5 of Typical Final test report are included in the Final Test Report for each Solar Simulator shipped. Page 6 of the Typical final test Report is included in the Final Test Report for Solar Simulators with Touch Panel Controls and page 7 of the Typical Final Test report is included in the Final Test Report for each Cell Tester.
Spectral Match = +7.8% to -7.3%
Better Than Class A Spectral Match Requirements of ASTM E927-2010, IEC60904-9 Edition 2.0 2007-10 and JIS C 8912-1998: amendment 1-2005 & Amendment 2-2011 (≤ 25%)
Spectral Match vs Wavelength Band
Irradiance Ratio vs Wavelength Band (nm)
Non-uniformity = 1.78%
Meets Class A Non-Uniformity Requirements of ASTM E927-2010, IEC60904-9 Edition 2.0 2007-10 and JIS C 8912-1998: amendment 1-2005 & Amendment 2-2011 (≤ 2%)
Long Term Instability (LTI) = 1.04%
Much Better Than Class A Long Term Instability Requirements of ASTM E927-2010, IEC60904-9 Edition 2.0 2007-10 and JIS C 8912-1998: amendment 1-2005 & Amendment 2-2011 (≤ 2%)
Short Term Instability (STI) = +0.17% - -0.15%
Much Better Than Class A Short Term Instability Requirements of IEC60904-9 Edition 2.0 2007-2010 (≤ 0.50%)