|
|
Why Class A? |
As photovoltaic (PV) cell manufacturers are driven to higher volume and cell uniformity requirements, Class A systems are becoming a necessity. By ensuring measurement uniformity that allows results comparability and traceability, Class A systems reduce the process and binning variability of photovoltaic cell testing as compared to Class B or non-classified sources. |
Defining Class A Performance Standards |
PV standards mandate that Class A solar simulators adhere to demanding requirements in three key performance areas: spectral match to the solar spectrum, spatial uniformity of irradiance, and temporal stability. There are three standards that define solar simulator performance. |
IEC 904-9 (1995) Photovoltaic Devices – Part 9: Solar Simulator Performance Requirements- JIS C 8912-1998, Solar Simulators for Crystalline Solar Cells and Modules
- ASTM E 927-05 (2005) Specification for Solar Simulation for Terrestrial PV Testing
|
Table 1 Class A Standards and Specifications |
| Performance Parameter |
Organization |
| IEC |
JIS |
ASTM |
| Spectral Match (fraction of ideal percentage) |
0.75 – 1.25 |
0.7 – 1.25 |
0.7 – 1.25 |
| Non-uniformity of irradiance |
≤±2% |
≤±2% |
≤±2% |
| Temporal Instability |
≤±2% |
≤±1% |
≤±2% |
|
Spectral Match |
The standards define the spectral match of a solar simulator as a percentage of the integrated intensity in 6 spectral ranges (listed in Table 2). Any deviation from the specified percentages must then lie within a range that determines the class of the simulator. For Class A, this range is 0.75 to 1.25 times the ideal percentage.
To ensure that the Oriel Class A Solar Simulator falls easily and reliably within this range, we designed a proprietary, highly stable spectral correction filter. The proprietary filter can withstand the very high intensity from the lamp without changing spectral properties. The result is the spectral output shown in Figure 1b.
The filter was also designed to maintain Class A performance over the full life of the lamp; see Fig. 4. |
Table 2 Ideal Spectral Match Defined by IEC Standards |
| Spectral Match |
| Spectral Range (nm) |
400 – 500 |
500 – 600 |
600 – 700 |
700 – 800 |
800 – 900 |
900 – 1100 |
| Ideal % |
18.5 |
20.1 |
18.3 |
14.8 |
12.2 |
16.1 |
|
Fig. 1a Solar simulator spectral output without Class A filters
|
Fig. 1b With proper Oriel Class A spectral correction filter, the same simulator shown in Fig. 1a meets Class A requirements
|
Spatial Uniformity of Irradiance |
The irradiance uniformity over the work area is the most difficult Class A requirement to achieve and maintain. Hot spots can lead to significant errors in measured cell efficiency and can cause inaccurate binning of cells. The Class A spatial uniformity performance standard is designed to minimize the impact of hot spots and has a very stringent requirement of ≤±2%. |
Fig. 2 Measured Uniformity of a 2x2” Oriel Class A Solar Simulator.
|
Temporal Stability |
Temporal stability is the third performance parameter of Class A standards. It requires that the output light be stable over time in order to ensure that the lamp fluctuations do not distort the measurements of solar cell efficiency. Our optional Light Intensity Control system substantially reduces lamp output fluctuation to values that are significantly below the maximum of ≤±1%. Even without the Light Intensity Control system, the Oriel Class A Solar Simulators meet the three standards. |
Fig. 3 Typical Output Variation of a 1.3 kW Oriel Class A Solar Simulator Over Time.
|
Fig. 4 Spectral output of Oriel Solar Simulator, over life of a 1000 W lamp.
|
Oriel Class A Solar Simulator Key Components |
Illuminator Housing |
The illuminator housing provides a safe enclosure for the lamp. It is equipped with safety interlock systems to ensure operator and system safety. An integral fan and filter blower provides forced air-cooling to maintain optimal lamp, optics and housing temperature.
Integrated Shutter
The Oriel Class A Solar Simulator includes an upgraded shutter for production-environment operation. The newly designed shutter for the Class A systems is a rugged, single-blade shutter designed for 1 million cycles. Real-world performance has exceeded 10 million cycles. The shutter has a minimum exposure time of 200 ms and can be controlled via a contact closure or logic level input, or a convenient push-button switch on the illuminator housing. |
Xenon Arc Lamp |
The Oriel Class A Solar Simulator source is a CW system. This enables testing of all cell materials unlike flashlamp-based systems that are limited by the response time of the material. The lamp is an ozone-free xenon short arc lamp. We certify each source with the supplied lamp. For continuous production environments, we recommend purchasing replacement lamps when the source is purchased, and certifying each lamp. This will ensure Class A certification as lamps are replaced. |
1.5G Air Mass Filter |
The combination of lamp and air mass filter produces the characteristic Class A spectra. Our 1.5G Air Mass Filter retains its optical properties through the life of the lamp. Replacement filters are sold separately. |
Power Supply |
The highly regulated power supply provides constant electrical power to the xenon lamp. Lamp usage can be monitored in accumulated hours from the power supply. It is important to replace the lamp at the end of its rated life to maintain the minimum 1 sun output. The lamp’s output will significantly decrease and change spectrally with continued use. |
|
|
Maintaining An Oriel Class A Solar Simulator |
Oriel Class A Solar Simulators maintain Class A standards during the lifetime of the lamp. When the lamp is replaced, and as the simulator ages, the instrument may fall outside of Class A performance. Spatial uniformity is the most difficult Class A requirement to meet and maintain. In order to facilitate the measurements and adjustments necessary to maintain spatial uniformity, we developed tools to allow rapid measurement and determination of performance. The use of these tools can significantly reduce the time and effort required to maintain the Oriel Class A Solar Simulator within Class A specifications. * Please contact a Sales Engineer for details. |
| *Note: the use of these tools does not constitute re-certification of the system to Class A standards. For re-certification, we recommend that the entire Class A Solar Simulator be returned to the factory. |
|
|
|
|
|
|
We recommend purchasing replacement lamps and certification at the time of purchase of the source. Contact a Sales Engineer for details. |
Contact a Sales Engineer for pricing of optional accessories. |