A thermal energy storage apparatus, including: a block of a heat-absorbing material, and a plurality of heat storage elements, the heat storage elements including a phase change material stored in a containment vessel; wherein each heat storage element is in thermal contact with the block of heat-absorbing material.

A thermal energy storage apparatus, including: a block of a heat-absorbing material, and a plurality of heat storage elements, the heat storage elements including a phase change material stored in a containment vessel; wherein each heat storage element is in thermal contact with the block of heat-absorbing material.

A Stirling engine has a housing containing a displacer and a power piston arranged to reciprocate relatively to one another. A head is adjacent to the displacer to absorb heat, and is surrounded by a block of copper or aluminum. A substantial proportion of the block is clad with a layer of stainless steel or Inconel having a thickness of between 3 mm and 0.15 mm.