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Canadian scientists have developed a new method to measure the energy yield of bifacial photovoltaic systems. As they explained, they took into account the spectral albedo of the ground surface, such as snow and sand, to predict energy gains of up to 2%, compared to the International Electrotechnical Commission (IEC) standard.
Researchers at the Sunlab laboratory at the University of Ottawa have devised a new way to measure the energy yield of bifacial photovoltaic systems. The innovative method is intended to complement the International Electrotechnical Commission (IEC) measurement standard introduced in 2019.
The new Scaled Back Irradiance (SRI) process purportedly improves the IEC measurements by taking into account the effects of the spectral albedo of different ground covers in its calculation of bifacial system back irradiance.
To prove the concept, the scientists modeled the performance of a bifacial heterojunction silicon (HJT) solar module using the IEC bifacial illumination technique and the SRI method. They mounted the system on a single-axis horizontal tracker 1.22 meters above the ground in Boulder, Colorado, USA. The ground surfaces considered were dirt, red brick, green grass, tiles, concrete, sand, dry grass, and snow.
The results show that for a rear irradiance of 200 W/sqm, the IEC measurement does not distinguish between the different ground surfaces, overestimating the bifacial gain by between 14% and 1.4% for all ground cover except snow. . The ISR method, on the other hand, shows a clear differentiation between the range of operating conditions.
"The application of this method to the international standards for this type of panels can allow us to predict the performance of outdoor bifacial panels with an absolute precision of 2%," says researcher Erin Tonita.
The new method was also able to predict energy yield increases at various locations in Boulder with less than 7% error, according to the academics.
According to the authors, this technique could be used to compare different bifacial technologies and improve system performance by optimizing the specific design of the plant surface. They shared their findings in “ A general illumination method to predict bifacial photovoltaic system performance ” recently published in Joule. |
