A Stirling-cycle apparatus comprising: a hermetically sealable housing; a first rotary displacement unit and a second rotary fluid displacement unit, each operably mounted in a separate, fluidly sealed portion within said housing and adapted to provide a cyclic change of at least one thermodynamic state parameter of a working fluid during use, each said first and second rotary displacement unit comprising: a compressor mechanism, having a first compressor working chamber that is adapted to receive a first portion of said working fluid, and at least a second compressor working chamber that is adapted to receive a second portion of said working fluid; an expander mechanism, having a first expander working chamber that is adapted to receive said first portion of said working fluid, and at least a second expander working chamber that is adapted to receive said second portion of said working fluid; a drive coupling assembly, adapted to operably and operatively couple said first expander mechanism to said first compressor mechanism: characterised in that: said first rotary displacement unit is in fluid communication with said second rotary fluid displacement unit; said first compressor working chamber comprises a first outlet port and said second compressor working chamber comprises a second outlet port; said first expander working chamber comprises a first inlet port and said second expander working chamber comprises a second inlet port; said drive coupling assembly comprises: a rotating valve mechanism, adapted to provide a predetermined sequence of a cyclic fluid exchange between said first compressor working chamber and said first expander working chamber, and between said second compressor working chamber and said second expander working chamber, at predetermined intervals of the angle of rotation of said first and second rotatory displacement unit; and an actuator, operably coupled to said first and second rotary displacement unit, and adapted to synchronously link the rotational movement of said first rotary displacement unit with said second rotary displacement unit, such that said first predetermined cyclic change of at least one thermodynamic state parameter of said working fluid is offset in relation to said second predetermined cyclic change of at least one thermodynamic state parameter of said working fluid by a predetermined phase angle, during use. a hermetically sealable housing; a first rotary displacement unit and a second rotary fluid displacement unit, each operably mounted in a separate, fluidly sealed portion within said housing and adapted to provide a cyclic change of at least one thermodynamic state parameter of a working fluid during use, each said first and second rotary displacement unit comprising: a compressor mechanism, having a first compressor working chamber that is adapted to receive a first portion of said working fluid, and at least a second compressor working chamber that is adapted to receive a second portion of said working fluid; an expander mechanism, having a first expander working chamber that is adapted to receive said first portion of said working fluid, and at least a second expander working chamber that is adapted to receive said second portion of said working fluid; a drive coupling assembly, adapted to operably and operatively couple said first expander mechanism to said first compressor mechanism: a compressor mechanism, having a first compressor working chamber that is adapted to receive a first portion of said working fluid, and at least a second compressor working chamber that is adapted to receive a second portion of said working fluid; an expander mechanism, having a first expander working chamber that is adapted to receive said first portion of said working fluid, and at least a second expander working chamber that is adapted to receive said second portion of said working fluid; a drive coupling assembly, adapted to operably and operatively couple said first expander mechanism to said first compressor mechanism: said first rotary displacement unit is in fluid communication with said second rotary fluid displacement unit; said first compressor working chamber comprises a first outlet port and said second compressor working chamber comprises a second outlet port; said first expander working chamber comprises a first inlet port and said second expander working chamber comprises a second inlet port; said drive coupling assembly comprises: a rotating valve mechanism, adapted to provide a predetermined sequence of a cyclic fluid exchange between said first compressor working chamber and said first expander working chamber, and between said second compressor working chamber and said second expander working chamber, at predetermined intervals of the angle of rotation of said first and second rotatory displacement unit; and an actuator, operably coupled to said first and second rotary displacement unit, and adapted to synchronously link the rotational movement of said first rotary displacement unit with said second rotary displacement unit, such that said first predetermined cyclic change of at least one thermodynamic state parameter of said working fluid is offset in relation to said second predetermined cyclic change of at least one thermodynamic state parameter of said working fluid by a predetermined phase angle, during use.