The development of thermal energy storage technologies to match sustainable energy production is of interest. A prototype of a multi-cell thermochemical battery consisting of connected cells containing MgCl2 salt, and additional air-cooled or air-heated cells containing liquid ammonia of varying quality, was constructed and tested. Each of the 17 cells contained thermocouple probes at three different axial locations within the cylindrical cells. Heat transfer rates, pressures, and ammonia condensation and vaporization rates were measured.
Three tests were run. In the first test, the hot bed containing 10 cells was heated using cartridge heaters, driving vaporous ammonia from the salt phase once sufficient salt temperatures were reached. The evolved gaseous ammonia was condensed in an additional 7 empty air-cooled cells. Once the recharging cycle was complete, a valve in the ammonia vapor line connecting the cold and hot beds was closed, allowing indefinite storage of cooling or heating capacity. The second operational test involved the opening of the valve while simultaneous air-cooling the hot bed cells and air-heating the cold bed cells. Heating rates and cooling rates to/from air forced through the hot bed and cold bed, respectively, were monitored to gauge HVAC performance. The second recharge was performed by using a air/air heat exchanger that captured waste heat from an automobile engine exhaust manifold and transferred it to air that was re-circulated through the hot bed array. Temperatures, pressures, heating rates, cooling rates, and cell array heat transfer specifications are reported.
