a composition for thermal energy storage or thermal energy generation comprising a silica based gel or dry powder in the form of silica particles containing a water / urea phase change material for thermal energy storage or an endothermic or exothermic compound for thermal energy generation . the water / urea phase change material stores and releases at least 50 cal / gm of thermal energy in freezing and melting , and has a melting and a freezing point in the range of - 11 ° c . to - 15 ° c . the endothermic compound is preferably ammonium nitrate , urea , or combinations thereof . the exothermic compound is preferably calcium oxide or calcium chloride . the thermal energy storage composition may find use in a variety of applications including medical wraps , food servingware , and &# 34 ; blue ice &# 34 ; for cold packs or food storage . the thermal energy generation composition may find use as medical wraps , food servingware , and refrigerators when endothermic and medical wraps , food servingware , heaters , stadium seats , boots , vests , caps ear muffs , and scarves when exothermic .