A system comprising: a cryogenic engine system (410, 610) comprising a working fluid and an expander (420, 620) for expanding the working fluid; a refrigeration system (460, 660), comprising a heat exchange system wherein: the cryogenic engine system (410, 610) and the refrigeration system are thermally coupled with each other via the heat exchange system such that the working fluid in the cryogenic engine system (410, 610) acts as a heat sink for removing heat from the refrigeration system and heat generated by the refrigeration system is used to expand the working fluid in the expander (420, 620) of the cryogenic engine system; the system comprising a refrigeration compartment thermally connected to the heat exchange system; wherein the cryogenic engine system (410, 610) is a direct and an indirect heat sink for removing heat from the refrigeration compartment; and wherein the heat exchange system comprises: a first heat exchanger (418, 618) in direct thermal contact with working fluid from the cryogenic engine system (410, 610) and in direct thermal contact with the refrigeration compartment; a second heat transfer member (422, 426, 622, 626, 670, 678) in direct thermal contact with the working fluid expanded in the expander (420, 620) of the cryogenic engine system (410, 610); a third heat transfer member (470, 682) in direct thermal contact with the interior of the compartment; and an intermediate heat transfer fluid circulation system (466, 474, 690) comprising a heat transfer fluid in thermal contact with both the second heat transfer member (422, 426 622, 626, 670, 678) and the third heat transfer member (470, 682). a cryogenic engine system (410, 610) comprising a working fluid and an expander (420, 620) for expanding the working fluid; a refrigeration system (460, 660), comprising a heat exchange system wherein: the cryogenic engine system (410, 610) and the refrigeration system are thermally coupled with each other via the heat exchange system such that the working fluid in the cryogenic engine system (410, 610) acts as a heat sink for removing heat from the refrigeration system and heat generated by the refrigeration system is used to expand the working fluid in the expander (420, 620) of the cryogenic engine system; the system comprising a refrigeration compartment thermally connected to the heat exchange system; wherein the cryogenic engine system (410, 610) is a direct and an indirect heat sink for removing heat from the refrigeration compartment; and wherein the heat exchange system comprises: a first heat exchanger (418, 618) in direct thermal contact with working fluid from the cryogenic engine system (410, 610) and in direct thermal contact with the refrigeration compartment; a second heat transfer member (422, 426, 622, 626, 670, 678) in direct thermal contact with the working fluid expanded in the expander (420, 620) of the cryogenic engine system (410, 610); a third heat transfer member (470, 682) in direct thermal contact with the interior of the compartment; and an intermediate heat transfer fluid circulation system (466, 474, 690) comprising a heat transfer fluid in thermal contact with both the second heat transfer member (422, 426 622, 626, 670, 678) and the third heat transfer member (470, 682). the cryogenic engine system (410, 610) and the refrigeration system are thermally coupled with each other via the heat exchange system such that the working fluid in the cryogenic engine system (410, 610) acts as a heat sink for removing heat from the refrigeration system and heat generated by the refrigeration system is used to expand the working fluid in the expander (420, 620) of the cryogenic engine system; the system comprising a refrigeration compartment thermally connected to the heat exchange system; wherein the cryogenic engine system (410, 610) is a direct and an indirect heat sink for removing heat from the refrigeration compartment; and wherein the heat exchange system comprises: a first heat exchanger (418, 618) in direct thermal contact with working fluid from the cryogenic engine system (410, 610) and in direct thermal contact with the refrigeration compartment; a second heat transfer member (422, 426, 622, 626, 670, 678) in direct thermal contact with the working fluid expanded in the expander (420, 620) of the cryogenic engine system (410, 610); a third heat transfer member (470, 682) in direct thermal contact with the interior of the compartment; and an intermediate heat transfer fluid circulation system (466, 474, 690) comprising a heat transfer fluid in thermal contact with both the second heat transfer member (422, 426 622, 626, 670, 678) and the third heat transfer member (470, 682). a first heat exchanger (418, 618) in direct thermal contact with working fluid from the cryogenic engine system (410, 610) and in direct thermal contact with the refrigeration compartment; a second heat transfer member (422, 426, 622, 626, 670, 678) in direct thermal contact with the working fluid expanded in the expander (420, 620) of the cryogenic engine system (410, 610); a third heat transfer member (470, 682) in direct thermal contact with the interior of the compartment; and an intermediate heat transfer fluid circulation system (466, 474, 690) comprising a heat transfer fluid in thermal contact with both the second heat transfer member (422, 426 622, 626, 670, 678) and the third heat transfer member (470, 682).