Joshua Pearce from Michigan Technological University (MTU) and researchers from Queen’s University in Canada have found a way to get more sunshine on solar panels, increasing its output by 30% or more.
According to Pearce, an associate professor of materials science and engineering and electrical and computing engineering, the research focused on the system rather than individual panels. The current setup for ground-mounted solar panel arrays, he intones, 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.
Pearce explains that this space can be filled with a reflector to bounce sunlight back onto the panels.
However, reflectors, or planar concentrators, are not widely used. Why? Well, panels are usually warranted for 20 to 30 years. 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.
Not anymore. Pearce and his team have found a way to predict the effects using bi-directional reflectance function (BDRF). 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.
By showing how the reflectors scatter light, the researchers started to take the risk out of using reflectors with solar panels. More importantly, the reflectors greatly increase solar system output.
The team took their model to the field and ran an experiment on Canada’s Open Solar Outdoors Testing Field in Kingston, Ontario.
With standard panels, not tilted at the optimum angle for the latitude, the increase in efficiency reached 45%. Even with a panel optimally tilted, the efficiency increased by 18% and simulations show it could be pushed to 30% with better reflectors.
Such a large increase of efficiency at the system level could greatly change how solar panels are installed, and with the economic payback, it could even mean major retrofits for existing solar farms.
Image courtesy of Michigan Technological University