Turning a solar power system into its own backup

247Solar is developing a concentrated-solar system designed to share its power-generation equipment with a fuel-burning backup, avoiding the need for a separate generator. Mirrors focus sunlight on a receiver that heats ordinary air to about 970°C. The air can be stored as heat in ceramic pellets, which the company says can support electricity generation for roughly nine to 20 hours after sunset, or be used directly for industrial heat. To generate electricity, hot air passes through a heat exchanger that replaces the combustor in a standard turbine assembly. When solar heat is insufficient, the same exchanger can be heated by burning a range of fuels; adding that capability is expected to cost less than 10 percent of the system’s total. The hot exhaust may also supply industrial processes or cooling.

The approach aims to address concentrated solar’s difficulty competing with cheap photovoltaic panels, while using thermal storage and shared hardware to provide power during cloudy periods and overnight. An initial Indian installation, combining photovoltaics with two 200-kilowatt generators, will test the engineering; a modular 3-megawatt design is in development. Whether the system can compete economically on power grids remains uncertain, since the value of backup generation may not flow to the plant’s owner. 247Solar sees a stronger opportunity at remote mines, where delivered diesel is costly and the system could also provide useful process heat. Its appeal will depend on proven performance, cost, and market incentives.