APPLICABILITY OF CARBONATION DECARBONATION REACTIONS TO HIGH-TEMPERATURE THERMAL-ENERGY STORAGE AND TEMPERATURE UPGRADING

Storing thermal energy by thermochemical means seems very attractive s ince large amounts of energy can be stored per unit mass, and such sys tems can function as a heat pumps, For storing high temperature heat e nergy such as concentrated solar energy at 773 K, various candidate ch emical reactions have been evaluated in terms of energy storage densit y, turning temperature, toxicity, corrosiveness, and other factors, Th e dissociation reaction of CaCO3 is found to be very promising, Three methods for storing the dissociation product CO2 gas; (i) storing as a compressed gas, (ii) letting the CO2 gas react with a metal oxide and storing it in the form of another carbonate, and (iii) adsorbing with an appropriate adsorbent and storing as an adsorbed gas; have been pr oposed and the respective thermal operating efficiencies at various up graded temperatures are evaluated. The CaO-CO2 metal oxide system seem s very effective for temperature upgrading around 1273 K and the CaO-C O2-compressor system seems suitable for storing and delivering heat en ergy at the same temperature, Whether the efficiency of the CaO-CO2-Ad sorbent system is comparable to one of the other two systems or not gr eatly depends upon the adsorptivity of the adsorbent.