By Roy L Hales
For the past eight years, the PHOTON Laboratory has been monitoring solar modules on a shade free area of land near the historic city of Aachen, Germany. They measure the yield expressed in kilowatt-hours related to the power of the modules and consider solar radiation at the site. The average yield has increased 4.9% within the past three years and in 2013 set a new record: 91.5%.
According to PHOTON’s press release,
“The Performance Ratio indicates the percentage of the incoming solar energy a module is able to transform into electricity considering its efficiency. The theoretical maximum of 100 percent is given if the module achieves the same efficiency under all kinds of irradiation that is does under Standard Test Conditions (STC). In practice, efficiency variations occur, especially when weak-light conditions combine with high temperatures. That’s why the Performance Ratio also depends on how good a module copes with the weather conditions onsite.”
“Using modern solar modules leads to far better yields than 1 or 2 years before,” said Anne Kreutzmann, CEO of PHOTON Publishing GmbH. This fact should be taken into account when making revenue calculations, “Far too often, revenue calculations start with yields that are too low because they refer to average yields from 3 or 4 years ago.”
“On the other hand, those who want to calculate projected revenue using the higher yields should take into consideration that the modules on the PHOTON test field with higher values could lead to the presumption of a higher Performance Ratio. The worst module in 2013, for example, achieved a Performance Ratio of 87.9 percent, delivering a yield that was typical 2 years ago.
“Good conditions for a high Performance Ratio are a low temperature coefficient and a good weak-light behavior. Those two module qualities are verified by the PHOTON Laboratory even before the modules are installed on the test field. Using this data, the lab was able to predict an average result for three of the top ten modules added to the field last year. But there were also some surprising findings, as the yield also depends on other factors such as the module’s reflection behavior and the dependence of the efficiency on the module’s spectral sensitivity. A truly resilient result is therefore given only by the long-term measurements done on the field. These measurement are published in a monthly update on the PHOTON website, www.photon.info, in the »Laboratory« section.”
This year’s high – the SR 190 monocrystalline module from Chinese producer Sopray Energy – was 94%.
The record high, 95.2%, was achieved by a US manufacturer last year. SunPower had dominated the field in 2012, producing the top three modules:
- SPR-327NE-WHT-D (95.2%),
- SPR-320NE-WHT-D (94.9%)
- SPR-245NE-WHT-D (94.8%).
It is not known if SunPower could have repeated this sweep in 2013. Its products were among the twenty-six modules were not measured correctly every month, because of problems with PHOTON’s newly-developed testing equipment for IV curves. The top three modules for 2013 were all produced by Chinese companies who were new comers who had not been previously been tested for a full calendar year :
- Sopray Energy – SR-190 (94%)
- Risen Energy – SYP190S-M – (93.8%)
- ET Solar Industry – ET-M66250WW – (93.4%)
Excluding SunPower’s results for 2012, for a better comparison, the average yield that year was 89.9%. That is 1.6% lower than the average for 2013.
As has been their normal operating procedure, PHOTON did not clean the modules in the test field. Nor were they cleared of snow, “which hardly mattered this year, as there were practically no snowfalls in Aachen during 2013.”
(Image at top of page: Modul -Meßgerät, entwickelt von der PHOTON Laboratory, Aachen – Frank Schuberth / www.photon-pictures.com)