Boosting solar panel efficiency: Is it simply a matter of angles?

October 22, 2015 // By Paul Buckley
Joshua Pearce from Michigan Technological University and a team from Queen’s University in Canada have found a way to shine more sun on to solar panels which could boost the output by 30 percent or more.

The work is published in the Institute of Electrical and Electronics Engineers (IEEE) Journal of Photovoltaics.

“We’re looking at this from a systems perspective,” explained Pearce, who is an associate professor of materials science and engineering and electrical and computing engineering. 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, claimed
Pearce: Fill the space with a reflector to bounce sunlight back onto the panels.

At present reflectors, or planar concentrators, are not widely used.

“Panels are usually warranted for 20 to 30 years,” said Pearce, explaining 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 videogames 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 model that could predict how much sunlight would bounce off a reflector and where it would shine on the array.

“Real surfaces do not necessarily behave like perfect mirrors, even if they look like it,” explained Pearce. “So we applied [BDRF] models to these materials, which
scatter the light instead.”