A New Type of Large Scale Thermal Energy Storage

Abstract A new type of thermal energy storage (TES) with wide potential for renewable energy sources as well as conventional energy sources will be presented. The main energy storage medium is a special type of concrete that has significantly higher thermal conductivity than normal concrete. Although the recipe of this material is quite complex the main component is quartzite, a natural geo-material readily available in many parts of the world. Further, heat is transported in and out of the storage by way of a heat transfer fluid (HTF) which flows through steel pipe heat exchangers that are cast into concrete storage elements. These elements are specially designed to deal with thermal deformations and stressing. The flow through the modular system is typically arranged in parallel and serial fashion. A NEST TES is fully scalable and may consist of thousands of storage elements compactly arranged within an insulated building. The scalability implies that there is virtually no limit to size; for instance, an installation may have storage capacity for several GWh th . Thermal oil, pressurized water/steam, or compressed gases may be used as HTF. The storage is suited for high temperature applications up to 550 °C for electric power generation as well as moderate temperature applications such as process heat down to 100 °C. The storage is well suited for concentrated solar power (CSP) and other applications with direct generation of heat. The storage can equally well be used for storing “surplus” electricity, converted to heat, in areas with high penetration of variable renewable energy sources such as wind energy and/or photovoltaic. The first pilot plant will be built at the solar energy research facility at Masdar Institute in Abu Dhabi this year.