Engineers at Oregon State University have developed a new approach for the storage of concentrated solar thermal energy which could reduce its cost and make it more practical for wider use.
Their approach is to use thermochemical storage, in which a chemical transformation is used in repeated cycles to hold heat, use it to drive turbines and then be re-heated to continue the cycle.
Thermochemical storage resembles a battery, in which chemical bonds are used to store and release energy – but in this case, the energy is in the form of heat rather than electricity.
Most commonly heat might be stored and released over a 24-hour period as dictated by supply and demand but, theoretically, the energy produced could be stored indefinitely.
The engineers have tested a thermochemical storage system based on the reversible decomposition of strontium carbonate into strontium oxide and carbon dioxide, which consumes thermal energy. During discharge, the recombination of strontium oxide and carbon dioxide releases the stored heat.
Such a storage system would be much smaller and cheaper to build, with a 10-fold increase in energy density, than current thermal storage technologies. It uses materials which are nonflammable, readily available and environmentally safe.
The system works at such high temperatures (about 1200ºC) that it could be used to directly heat air to drive a turbine to produce electricity and have sufficient residual heat that it could be used to make steam to drive a second turbine.