Experimental results of a 10 kW high temperature thermochemical storage reactor based on calcium hydroxide

One promising possibility to store thermal energy is by means of reversible gas solid reactions. In this context, the endothermal dehydration of calcium hydroxide (Ca(OH)2) to calcium oxide (CaO) is a well known, cycle stable reaction able to store heat at temperatures above 410 °C and pressures above 0.1 bar. Additionally, the storage material itself is a widely available low cost raw material which allows for low cost thermal energy storage capacities. Therefore, a multifunctional test bench for thermochemical storage reactors has been developed and set into operation. Simultaneously an indirect operated reactor for ∼20 kg Ca(OH)2 was designed, manufactured and integrated into the test bench. Within this work the charge and discharge characteristics of the reactor concerning possible limitations due to heat and mass transfer were studied experimentally. Thereby, the possibility to store and release the heat of reaction at an adjustable temperature level was demonstrated in a technical relevant scale. The storage material remained stable and showed no degradation effects after ten cycles. -- Highlights: • Multifunctional test bench and indirect operated reactor developed and in operation. • Proof of principal for a 10 kW, 20 kg calcium hydroxide thermochemical storage reactor. • Several charge and discharge cycles were performed at adjustable storage temperatures