39% Higher Energy Yield with Bifacial PERPoly Modules


Vaassen, 22nd of October 2018 – Bas van de Loo
On the 25th of April, 2018, a new photovoltaic (PV) test facility has been completed at the Tempress Systems headquarters, in Vaassen, the Netherlands. The test site is used to monitor the outdoor performance of bifacial PV module technologies and compare this with their monofacial counterparts. Bifacial modules can, in contrast to monofacial modules, also capture ambient light entering from the rear side of the module.

To enhance the light absorption through the rear side of the bifacial modules, the test site features a highly-reflective white paint on the pavement. Various bifacial crystalline silicon solar cell technologies are examined, including commercial nPERT and PERC+, as well as n-type solar cells with state-of-the-art poly-Si passivating contacts at the rear side. These so-called PERPoly cells have been fabricated at ECN>TNO using Tempress Systems’ equipment, including the new Ox-Poly LPCVD furnaces for the rear side contacts. The bifacial modules are directly compared to a variety of commercial high-end monofacial reference modules, including nPERT, PERC, PERC with metal-wrap-through (MWT), half-cell PERC modules, Heterojunction with Intrinsic Thin layer (HIT) and interdigitated back-contact (IBC) modules.

Preliminary results over the four-month summer period (June – September) revealed that bifacial 60-cell modules featuring PERPoly cells (305 Wp) thus far resulted in the highest average daily energy production of all modules, i.e., 1.93 kWh. In comparison, a monofacial PERC module (292 Wp) yielded only 1.33 kWh on average per day, a 370 Wp IBC module 1.78 kWh and a 327 Wp HIT module 1.62 kWh. In conclusion, the bifacial PERPoly modules have a 39% higher specific energy yield (kWh/Wp) than PERC modules, meaning that they deliver 39% more electricity per watt-peak than PERC modules.

More results will be presented at the next international conference on crystalline silicon photovoltaics in Leuven, Belgium, on April 8-10.










Photovoltaic module test site at Tempress Systems, Vaassen. 24 modules are oriented south at an angle of 38 degrees. The modules are placed ~1 meter above the ground. The test site has been constructed by Schulz Systemtechnik B.V., and has been financially supported by the Dutch Ministry of Economic Affairs, via Top Consortia for Knowledge and Innovation (TKI) program ‘Champ’.













Comparison of electricity production of two photovoltaic modules over a 4-month period.











Output power of two 60-cell PV modules as measured on the 1st of July. The nominal power (expressed in watt-peak, Wp) as measured under standard test conditions is indicated. The bifacial module had a 40% higher specific energy yield on this day. This is partly attributed to the average 37% extra irradiance from the rear side. The peak output power of the bifacial module on this day was 354 W, versus 259 W for the monofacial module.