Combining amorphous photovoltaics with new storage media to achieve low cost electricity through stand-alone systems

The scale-up of multi-junction, spectrum splitting, amorphous silicon alloy, thin-film photovoltaic devices has recently resulted in the demonstration of large area (1 foot square) modules with a stable energy conversion efficiency of 10.2%. It has also been demonstrated that these advanced modules can be produced in a low-cost, flexible roll-to-roll continuous web manufacturing process, and a roll-to-roll pilot production plant with a 2 MW annual production capacity for these modules has been constructed and installed. When mass produced light-weight, roof-mounted solar shingle modules employing the spectrum splitting cell design are combined with a new, long-life, energy storage system based on high performance and environmentally-safe nickel metal hydride batteries, stand-alone photovoltaic systems can be constructed with the capability of providing residential electricity at very low cost. As the production volume of both the battery and solar cell manufacturing process is increased, economies of scale can, for the first time, allow the cost of stand-alone solar electricity to approach the cost of grid-connected power in many locations.