Tests carried out by Canadian researchers on the NREL take a look at discipline in Colorado have proven that floor reflectors based mostly on high-density polyethylene can enhance the efficiency of bifacial PV vegetation. They emphasize that the profitability of this expertise is strongly depending on the placement and warn to keep away from combining it with the clipping of the inverter.
Researchers on the University of Ottawa in Canada investigated the consequences of utilizing a synthetic floor reflector in massive bifacial PV vegetation and located that it may enhance the ability’s energy technology by as much as 4.5%.
“Critically, these reflectors must be positioned instantly beneath the photo voltaic panels, not between the rows, to maximise this profit,” mentioned lead analysis writer, Mandy Lewis. “These findings are significantly necessary in Canada, the place snow cowl persists for 3 to 4 months of the yr in main cities akin to Ottawa and Toronto, and 65% of the nation’s huge land space experiences snow. cowl for greater than half a yr.”
The analysis group carried out its evaluation on a 75 kW bifacial system based mostly on horizontal single-axis monitoring (HSAT) and positioned on the testing facility of the National Renewable Energy Laboratory (NREL) of the US Department of Energy in Golden, Colorado. “We studied a row of PERC + modules with a bifaciality issue of 70%,” it defined, noting that the take a look at was carried out for 4 months. “Module energy stage and time knowledge are measured at 1-min intervals and correctly averaged to acquire 15-min energy values.”
The scientists used a synthetic high-albedo, UV-resistant reflector materials made from high-density polyethylene (HDPE), provided by Germany-based Solmax Geosynthetics. Its solar-weighted reflectivity reached roughly 70%. They assessed 5 completely different reflector configurations: with 100% floor protection; 50% and 25% floor protection, each centered on the torque tube; and 50% and 25% soil protection, each centered in the course of the open floor between rows.
The efficiency of reflector-dependent PV system parts is in comparison with module arrays with out the reflector. The modeling exhibits a root imply sq. error (RMSE) of 5.4% per hour and exhibits a rise in whole annual irradiance of 8.6% and an annual power yield of as much as 4.5% when the 70 % reflective materials is added to a single- axis-tracked system. The optimum reflector placement was discovered to be the one centered instantly beneath the torque tube for all reflector sizes.
Further financial evaluation additionally discovered that reflector expertise may obtain breakeven put in prices of $2.50-4.60 per m2. “Higher materials breakeven prices are attainable in techniques with a better preliminary LCOE. For instance, we discover an put in breakeven value of $3.40–6.00/m2 for Seattle, Washington, with 60% reflective materials,” the teachers emphasised.
Furthermore, they emphasize that the profitability of reflectors is strongly depending on location, with photo voltaic radiation ranges enjoying an necessary position. They additionally advocate avoiding the deployment of reflectors in tasks with inverter clipping, which happens when the DC power of a PV system is bigger than the utmost enter measurement of the inverter. “Inverter clipping has a big influence on techniques that embody synthetic reflectors, lowering annual power positive factors and shifting the best placement for the smallest reflectors in some areas,” they warned.
Their experiments are described within the paper “Size and Position of Artificial Ground Reflectors on the Energy and Economic Impact of Single Axis Tracked Bifacial Photovoltaics,” printed in Advances in Photovoltaics. “These findings have explicit worth for Canada and different nations which can be largely cloudy, as energy positive factors of 6.0% had been noticed in cloudy Seattle in comparison with 2.6% in dry Tucson. ,” the researchers emphasised.
Another analysis group on the University of Ottawa has not too long ago developed a brand new method to measure the power yield of bifacial PV techniques. The new scaled rear irradiance (SRI) technique supposedly improves IEC measurements by accommodating the consequences of various floor covers’ spectral albedo in its calculation of the rear-side irradiance of the bifacial system.
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