Solar Simulation Systems

Features • Applications • Solar Simulator Models • Standards for Solar Simulators • Typical Final Test Report

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.

APPLICATIONS

Photovoltaic Cell Performance

Determining electrical performance of photovoltaic cells
Comparison of cell characteristics among group of cells or different cell designs
Repeated measurement of the same cell to study life cycle performance changes

Photochemistry/Photobiology

Testing sunscreen efficacy
Studying biological effects of solar radiation

Environmental Exposure Testing

Evaluating the effect of solar radiation on various materials and finishes
Accelerated testing for cross-linking of polymers and embrittlement of plastics
Testing for color fading of paints and fabrics
Qualifying and life-time testing of materials for space

FEATURES:

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.

Exposure Control
Each Solar Simulator has a shutter that can be operated manually from a switch on the front panel or remotely with a foot pedal. The shutter can also be programmed to open from 0.1 second to 999 seconds with a built in timer control.

Light Intensity & Control
The light intensity for all our Solar Simulators is one sun (1,000W/m²) ±20%. The intensity can be adjusted with the provided control on the front panel. The intensity adjustment is done by adjusting the control voltage to the Lamp Power Supply. Reducing the intensity below 80% is not recommended by this control method. The Lamp requires a certain minimum current to operate properly and provide stale spectrum. If testing needs to be done under intensities less than 0.8 suns (800W/m²) then we recommend using Neutral Density Filters (NDF) to control the intensity from 0-1,000W/m², without compromising the spectrum of the light. Each system has a Constant Light Intensity Controller as a standard feature. This control system maintains a constant level of light intensity for long-term exposures.

Output Power
It is possible to factory set the system light output higher than one sun when the lamp is new. If the system output is higher than one sun, then the intensity control is used to adjust the system output at one sun. As the lamp ages, the intensity control can be adjusted to maintain one sun output.

Safety Interlocks
The Light Source unit has safety interlocks. The door for lamp replacement has an electrical interlock to shut down the system if the door is opened without turning the system power off. This prevents access to the lamp when it is on thus preventing operator exposure to the radiation and protects against inadvertent contact with the hot lamp. There is a thermal interlock that turns the lamp off in the event the temperature within the housing exceeds safe operating levels. In addition there is a safety interlock that turns the system power off in the event the cooling fan fails.

Lamp Aging
The xenon arc lamp should be replaced at the after the rated life has been reached to ensure spectral fidelity and proper level of intensity. The rated life of each lamp typically ranges between 1,000 – 1,500 hours. In our computer controlled Solar Simulator Systems, the lamp life is monitored and displayed and the software also displays a message to remind that the end of the rated lamp life has been reached. In Electro-Mechanical controlled Solar Simulators, the lamp life is monitored and displayed on an LCD Hour Meter. It serves as a convenient reminder of when the lamp should be replaced. PET Solar Simulators have a lamp alignment feature that allows the lamp to be aligned without the lamp being turned on. This feature makes it very easy to align the lamp for the best uniformity.

Some Solar Simulator Systems

Complete model of SS50AAA-EM, a class A Solar Simulator, with Illumination area of 50mm x 50mm, and Air Mass Filter of AM1.5 Global. The Touch Panel Display controller of this model is built-in. More details…

Complete model of SS100AAA-EM, a class A Solar Simulator, with Illumination area of 100mm x 100mm, and Air Mass Filter of AM1.5 Global. The Touch Panel Display controller of this model is built-in. More details…

Turn-Key Solar Cell Testing Station, which includes Model SS150AAA-TP, a class A Solar Simulator, with Illumination area of 150mm x 150mm and Air Mass Filter of AM1.5 Global; plus, Model CC-5, a five (5) Amps capability I-V Measurement system. More details…

Model SS300AAA-TP, a class A Solar Simulator, with illumination area of 300mm x 300mm, and Air Mass Filter of AM1.5 Global. More details…

Model SS80AAA-EM

Click for larger image

SOLAR SIMULATOR MODELS

Solar Cell Tester Model CT30AAA-TP & CT30AAA-EM

SS30AAA-TP & SS30AAA-EM
100 Watt Solar Simulation System with an illuminated area of 30mm x 30mm.

SS50AAA-TP & SS50AAA-EM
150 Watt Solar Simulation System with an illuminated area of 50mm x 50mm.

SS80AAA-TP & SS80AAA-EM
300 Watt Solar Simulation System with an illuminated area of 80mm x 80mm.

SS100AAA-TP & SS100AAA-EM
500 Watt Solar Simulation System with an illuminated area of 100mm x 100mm.

SS150AAA-TP & SS150AAA-EM
1,000 Watt Solar Simulation System with an illuminated area of 156mm x 156mm.

SS200AAA-TP & SS200AAA-EM
1,435 Watt Solar Simulation System with an illuminated area of 210mm x 210mm.

SS300AAA-TP & SS300AAA-EM
3,000 Watt Solar Simulation System with an illuminated area of 300mm x 300mm.

SS400AAA-TP & SS400AAA-EM
7,000 Watt Solar Simulation System with an illuminated area of 400mm x 400mm.

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

Please click on table for a larger view.

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.