Light reflection model boosts solar farm efficiency

October 22, 2015 //By Paul Buckley
Light reflection model boosts solar farm efficiency
Researchers at Michigan Technological University (Houghton, MI) and Queen's University in Canada have found a way to shine more sun onto solar panels that could boost output by 30% or more.

The researchers used thermal radiation readings on panels to help better understand ways to improve low-concentration photovoltaic systems. Their findings - that solar panels are not getting as much light as they could be - is published in the Institute of Electrical and Electronics Engineers (IEEE) Journal of Photovoltaics .

"We're looking at this from a systems perspective," says Joshua Pearce, an associate professor of materials science and engineering and electrical and computing engineering at Michigan Technological University. According to Pearce, the research focused on the system rather than individual panels mostly because the current set up for ground-mounted solar panel arrays is "wasting space."

The iconic flat-faced solar panels installed in large-scale utility solar farms are spaced apart to prevent shading. As the sun shines on a photovoltaic system, sending electricity into the grid, a fair amount of that potential energy is lost as the light hits the ground between rows of panels.

The solution is simple, claims Pearce: Fill the space with a reflector to bounce sunlight back onto the panels. At present, however, reflectors - or planar concentrators - are not widely used.

According to Pearce, panels are usually warranted for 20 to 30 years, but the warranty only guarantees under certain circumstances. "If you're putting more sunlight on the panel with a reflector, you will have greater temperature swings and non-uniform illumination, but simple optics makes wrong predictions on the effect."

Because of the uncertainty with potential hot spots, using reflectors currently voids warranties for solar farm operators. Pearce and his co-authors found a way to predict the effects using bi-directional reflectance function, or BDRF.

BDRF is often used in movies and video games to create more life-like computer generated imagery (CGI) characters and scenes. BDRF equations describe how light bounces off irregular surfaces and predicts how the light will scatter, creating indirect brightening and shadows.

For their solar panel work, Pearce's team created a BDRF

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