Metal hydride heat pump system

A metal hydride heat pump system comprising:

• a plurality of operating units, each operating unit comprising a combination of a first metal hydride having a lower equilibrium dissociation pressure at an operating temperature and a second metal hydride having a higher equilibrium dissociation pressure at said operating temperature and means for causing hydrogen to flow freely only between the two metal hydrides in the respective operating units, the equilibrium dissociation pressure characteristics of at least one of the first and second metal hydrides in a given operating unit differ from those of at least one of the first and second metal hydrides in at least one other operating unit;
• each of said operating units having high temperature heat transfer medium source means, medium temperature heat transfer medium source means and a low temperature heat transfer medium source means, said first metal hydride being switchably connected in heat transfer relation to said high-temperature heat transfer medium source means and said medium temperature heat transfer medium source means, and the second metal hydride being switchably connected in heat transfer relation to said medium temperature heat transfer medium source means and said low temperature heat transfer medium source means, at least one of said heat transfer medium source means being common to at least two operating units, whereby when each of the operating units is operated such that in one cycle hydrogen is released from the first metal hydride after the first metal hydride has been heated to the temperature of the high temperature heat transfer medium, the released hydrogen is exothermally occluded by the second metal hydride after the second metal hydride has been heated to the temperature of the medium temperature heat transfer medium, and then hydrogen is endothermally released from the second metal hydride after the second metal hydride has been heated to the temperature of the low temperature heat transfer medium, and the released hydrogen is exothermally occluded by the first metal hydride after the first metal hydride has been heated to the temperature of the medium temperature heat transfer medium, heat absorption by the second metal hydride during release of hydrogen at said low temperature can be used for cooling and heat generated by the first metal hydride during occlusion at said medium temperature and/or heat generated by said second metal hydride during occlusion at said medium temperature can be used for heating.