A new solar power module developed by students and researchers at the University of Arizona uses a curved mirror to focus sunlight onto a 5-inch glass ball that then spreads the light evenly across a solar panel, a design inspired by telescope technology. The solar panel uses high-efficiency solar cell usually reserved for space applications. Those high-efficiency cells coupled with the mirrored design lead to twice the power output of traditional solar panels.
The tracker, as it's called, also has one more feature that lets it grab the greatest amount of sunlight. It doesn't sit passively in the sun, it, well, tracks it. The whole module is mounted on a steel 10 feet by 10 feet rotating frame that moves with the sun.
"The tracker is fully automated," Blake Coughenour, a graduate student in the UA's College of Optical Sciences, explained. "The system wakes itself up in the morning and turns to the East. It knows where the sun will rise even while it's still below the horizon. It tracks the sun's path during the day all the way to sunset, then parks itself for the night."
What makes the tracker particularly special is the mirror. The researchers used their experience with telescope mirrors to come up with a dish-shaped mirror design that works for concentrating sunlight for photovoltaics as opposed to a solar thermal system. This effort has already gotten them a $1.5 million Department of Energy grant to continue their work.
Roger Angel, Regents' Professor of Astronomy and Optical Sciences and director of the Steward Observatory Mirror Lab at the University of Arizona said, "Most mirrors used in solar power plants are used for thermal generation by focusing light onto a long pipe used to heat water into steam. This requires the mirrors to be shaped like a cylinder. What we have learned here at the Mirror Lab is how to bend the glass to high accuracy so as to focus to a point or a line."
The panels are made up of 36 solar cells usually reserved for use in spacecraft. These cells are able to capture a wider range of the solar spectrum than regular cells. The ball lens is coated to maximize transparency for the suns rays. Combined with the mirrors, all of this works beautifully to concentrate light on the the solar cells, but it also concentrates a bunch of heat. The team came up with a cooling system consisting of fans and a radiator that keeps the array within 36 degrees of the outside temperature.
But all that heat could go to good use. The team is also working on a way to use the mirrors to create an eco-friendly furnace that works like a toaster oven to burn a mold into a flat sheet of glass.
For now though, the team is focusing on solar power. From their tests, a tracker featuring two mirrors generates enough energy to power two homes, but they hope to place eight mirrors on each module.
Angel says that an array of sun trackers on an area measuring about seven by seven miles (11 x 11 km) would generate 10 GW of power during sunshine hours – as much as a big nuclear power plant. This technology has a lot going for it that makes it super promising.
The University of Arizona reports, "Unlike conventional power plants that use steam to power turbines, Angel's photovoltaic prototype uses no water, making it especially suitable for desert regions. The materials are cheap to produce and by concentrating sunlight with mirrors the plant's footprint is smaller than that of PV panel-based plants."
Below is a video that explains some of the development process for the tracker.