Analysis of a pumped thermal electricity storage system with the integration of low temperature heat sources

in this dissertation an innovative electric energy storage technology potentially suited for grid scale applications is proposed and analyzed. The investigated system belongs to a broader technology family which comprises an heterogenous group of technologies based on the idea of storing electric energy as thermal energy. Such group of technologies is known in literature by several names, with Pumped Thermal Electricity Storage (PTES) being the most common. Notwithstanding, the name “Carnot Batteries” is lately growing in popularity and may be found as well in literature. In PTES systems, the charge phase is usually performed by using a Heat Pump (HP), the energy conservation is entrusted to a Thermal Energy Storage (TES), which can be either a latent or a sensible one, and the discharge phase is performed by means of a Heat Engine (HE). In this dissertation, a system based on Vapor Compression HPs (VCHPs) and Organic Rankine Cycles (ORCs) is investigated. The classical configuration which may be found in literature has been modified to allow the heat pump being powered also by low-temperature heat sources, such that the system performance is improved. The use of additional low temperature heat sources has been called Thermal Integration (TI), which led to the development of a TI-PTES system