Supercritical CO2 Heat Pumps and Power Cycles for Concentrating Solar Power

Pumped Thermal Energy Storage (PIES) is a promising technology for electricity storage applications. An electrically driven heat pump moves energy from a cold space to a hot space, thereby creating hot and cold thermal storage. The temperature difference between the hot and cold storage is later used to drive a heat engine and return electricity to the grid. In this article, supercritical carbon dioxide (sCO(2)) is chosen as the working fluid for PIES, and results are compared to 'conventional' systems that use nitrogen. Molten salts are used for the hot storage which means that a CSP plant with thermal storage and an sCO(2) power cycle could potentially be hybridized with PIES by the addition of a heat pump. This article describes some of the benefits of this combined system which can provide renewable power generation and energy management services. Two methods by which an sCO(2) heat pump can be combined with an sCO(2) power cycle for CSP are described and techno-economic results are presented. Results indicate that these systems can achieve reasonable technical performance, but that costs are currently high.