Concentrated photovoltaic systems use lenses and mirrors to direct sunlight into small cells that generate power. They’re highly efficient but relatively expensive compared to standard solar panels. And they’re enormous. The arrays are normally the size of billboards, making them unsuitable for house rooftops.
What is more, concentrated photovoltaic (CPV) systems need to be pointing in the right direction throughout the day. They rely on large tracking systems to line them up with the sun. The cost of such additional equipment is another reason CPV is not in wider use today.
Not yet, anyway. Researchers from Penn State University and the University of Illinois have developed a smaller, consumer-sized CPV system that gets around some of the normal disadvantages of CPV and maximizes its advantages. Though at an early stage, it could allow homeowners to buy into higher-efficiency cells by reducing the cost of tracking.
The system has two main innovations. First the cells, which were developed at the University of Illinois, are very small: only tenths of a millimeter across compared to cells that are normally centimeters-squared. Second, the tracking system reverses the way things are normally done. The “microcells” are laid onto a piece of plastic, then sandwiched between two bubbled layers of optics. During the day, the middle layer moves slowly against the static outer layers, so it’s always got enough light.
“Instead of pointing all your optics at the sun, all your optics remain fixed and the solar cells move to follow the focal point,” explains Chris Giebink, an assistant professor of electrical engineering at Penn State.
As yet, the technology has only reached the prototype stage. But the results so far are impressive. The system captured 70% of available optical light and generated 50% more power than a conventional silicon solar panel (which has efficiency of about 20%).
Now Giebink needs to find more funding and do testing over a longer period to ensure the performance holds up. He’s optimistic but realistic. “This is technology that has real potential but unfortunately what potential means is that you’re not very good yet. So we’ll have to see where we’re able to get to,” he says.