Experimental proof of concept of a pilot-scale thermochemical storage unit

The present study presents installation and operation of the first pilot scale thermal storage unit based on thermochemical redox-cycles. The reactive core is composed of a honeycomb ceramic substrate, coated with cobalt oxide. This concept, already analyzed and presented at lab-scale, is now implemented at a larger scale: a total of 280 kg of storage material including 90 kg of cobalt oxide. The storage block was implemented inside an existing solar facility and connected to the complete experimental set-up. This experimental set-up is presented, with focus on the measurement system and the possible improvement for a next campaign. Start-up and operation of the system is described during the first complete charge-discharge cycle. The effect of the chemical reaction on the stored capacity is clearly detected by analysis of the temperature distribution data obtained during the experiments. Furthermore two consecutive cycles show no evident loss of reactivity inside the material. The system is cycled between 650°C and 1000°C. In this temperature range, the total energy stored was about 50 kWh, corresponding to an energy density of 630 kJ/kg. In conclusion, the concept feasibility was successfully shown, together with a first calculation on the system performance.