Long-term Power-to-Heat Storage based on Ca(OH)2 - Experimental Development of Pilot Plant

Abstract

Natural limestone is an abundant and inexpensive material in Europe. Therefore, using the reversible thermochemical reaction of Ca(OH)2 (calcium hydroxide), which is obtained from limestone, to CaO (calcium oxide) and water vapor for energy storage is a promising approach. After the energy charging process, CaO can be stored in solid form at ambient temperature for an indefinite amount of time free of thermal energy losses. Hence, such a storage principle has a particular advantage compared to latent or sensible storage methods, in case a longer storage duration (several weeks to months) is required. Consequently, an application that is of particular interest is, charging Ca(OH)2 during summer using excess renewable electricity, storing the CaO for several months and discharging it during winter supplying heat for the building sector. Based on this concept, a storage system including a novel reactor has been developed at the DLR. This publication presents its experimental data during operation including its performance and the challenges for the application of the storage system