The possibilty of using silica gel and water as a reversible pair, in a thermochemical heat-pump/energy-store has been studied theoretically and experimentally during both heating and cooling modes. With silica gel absorbing water by 25 +/-2% of the dry silica gel's weight, the heat of adsorption and the heat of wetting of 2712.43 +/- 30 kJ/kg SiO2 and 94.43 +/- 15 kJ/kg SiO2 have been achieved respectively. The concentration rate for the two reaction pair was investigated and a general relationship that governed the adsorption rate with time has been deduced.