As manufacturers work to drive down the cost of solar power, refining solar cells and panels to make them more efficient is only half the story. Another option is to incorporate newer electronics into the panels that could boost the power output of photovoltaic systems and make them easier to design and install.
Suntech Power, the world’s largest maker of crystalline-silicon solar modules, based in Wuxi, China, has announced partnerships with Santa Clara, California-based National Semiconductor and other solar electronics makers to develop “smart” panels that would give the most power possible even if other panels are underperforming due to damage or to sunlight being blocked by shade or debris. This kind of system is useful because in conventional photovoltaic systems, one panel’s performance affects the output of the whole system. “We think smart module technology is a clear path for the future,” says Andrew Beebe, Suntech’s chief commercial officer.
Solar manufacturers are finding it difficult to eke out additional increases in how efficiently crystalline-silicon solar panels convert sunlight into electricity–so solar innovation has shifted to back-of-the-panel electronics. “Every incremental power advantage brings down cost per watt, and electronics are where the improvements are going to be,” says Matthew Feinstein, a research associate at Lux Research.
National Semiconductor’s power-optimizing device is already on the market. Tests on customer installations have shown that it can squeeze 25 percent more energy from a photovoltaic system, says Kevin Kayser, a marketing manager at the company. Independent tests by the National Renewable Energy Laboratory and Photon International have demonstrated power gains from arrays as high as 39 percent.
Solar modules operate at various current and voltage levels. Panels are traditionally strung together in a series, and their combined DC power is sent to a large inverter. The inverter does two things: it converts the power into grid-ready AC electricity, and its control circuit constantly searches for and sets the operating voltage and current levels for all the panels based on the total power output of the array. But if one panel’s current drops because of shade or debris, the inverter lowers the current of all the other panels, bringing down the array’s power output. “Ten percent shade on the array means a 50 percent power loss,” Kayser says.
National Semiconductor’s power optimizer does away with the central control circuit in the inverter, instead placing a separate control circuit behind each panel. This allows the optimizer to wring the most power from each panel. In addition, Kayser says, while some power-optimization products either increase both current and voltage or decrease current and voltage, theirs can increase and decrease both current and voltage, squeezing out even more power.