The number of homes with solar panels has grown quickly in the last few years. But there could be a lot more. Up to three-quarters of houses are still thought to be unsuitable for solar because of shading, ownership, and structural issues. Shading is also a serious issue even for homes with solar. Covering up just 3% of an array leads to a loss of 25% of power, according one estimate.
That's why an invention by graduate students at MIT is potentially significant. It could both raise the performance of shaded panels and put homes that are currently excluded from solar into play.
The team's integrated circuit recently picked up two prizes: the Department of Energy's $100,000 Energy Efficiency and Renewable Energy Clean Energy Prize and the MIT Clean Energy Prize, worth $125,000.
"Our technology focuses on solving the problem of shading on solar panels, where a small percentage of shading can cause significant losses," explains Bessma Aljarbou, one of the team members.
Because solar panels are made up of cells in series, one bad cell can affect performance of the whole panel. Likewise, one bad panel can affect the performance of a whole array. The whole system is only as good as its weakest link, because ideally you want power to flow equally between all points.
To get around this problem, many systems have added power optimizers that isolate certain panels, thus improving overall performance. But that's far from ideal. It's a sledgehammer solution to a nut-sized issue, Aljarbou says.
The circuit from the MIT team instead balances power between cells that are energized and cells that are shaded. "When you're doing it at the cell-level, you're capturing more energy," Aljarbou says. The team claims its prototype recovers double the energy compared to existing power optimization methods.
For now, the circuit is only working in the lab. The team, which has formed a company called
United Unified Solar, now plans to develop a commercial prototype and start working with manufacturers on a full product.
"It has the potential to open a whole bunch of new rooftops and make entire rooftops more efficient and ultimately drives down the cost of solar," Aljarbou says.