Solar panels are usually mounted in series, to sum up their voltages, and the resulting power is sent to a large inverter, which transforms the DC voltage into AC. One big issue with this scheme is that if shade falls on one panel, or it gets dirty, the inverter lowers the current of all the other panels, and causing power losses through inefficiency.
“Ten percent shade on the array means a 50 percent power loss,” says Kevin Kayser, a marketing manager at National Semiconductor.
A partnership between Wuxi, China-based Suntech Power and National Semiconductor from California now yields a smart approach toward this problem. The two companies have jointly developed a system that limits the damage caused by one underperforming solar panel and keeps the production of all the others at their optimum parameters.
“We think smart module technology is a clear path for the future,” says Andrew Beebe, Suntech’s chief commercial officer.
Power gains by up to 39 percent have been demonstrated using the technology (by the NREL), and the add-ons have already been tested on real installations at various customers. “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.
The power optimizer deals with the central control circuit in the inverter, and does not insert separate control electronics on each panel, thus reducing price. The device costs the user another 12 cents per watt and pays within two years, on average.
An other product of Suntech, the microinverters, could offer an extra modularity to the wiring of a solar array and could improve the overall efficiency. The microinverters make the conversion from DC to AC at each panel from 30 volts to around 120 volts, to be grid-compatible. This should solve lots of headaches related to the topology of the system and to its modularity.