the apparatus is a hydride heat pump which uses double communicating section containers holding high and low temperature metal hydrides , with the containers moving back and forth within channels between three heat exchangers . the preferred device has a cylindrical body with the several cylindrical channels in a circular pattern around the axis of the cylindrical body . high , medium , and low temperature heat exchangers are located in the body in sequence along the channels . transition regions formed by thermal bridges alternating with thermal insulation are located along the channel walls between the heat exchangers to transfer heat among all the hydride containers located in each transition region . the lengths of the heat exchangers and the transition regions , the geometry of the containers , the timing of the reciprocation , and the number of channels are selected so that at least two containers moving in opposite directions are in contact with the transition zones at any time .