Abstract: A solar collector (2) associated with or incorporated in a heat sink (4), such as a concrete slab, powers an organic Rankine cycle heat engine. Preferably, the working fluid can be heated by a second heat source, derived from biomass or waste incineration for example, after the heat sink (4) has cooled down.

Abstract: Slush gas, i.e. a gas or a mixture of gases cooled so that it is partially solid and partially liquid is employed as a drive fluid in a cryogenic engine. A cryogenic engine has a working chamber (50) connected to an energy source comprising a body of slush gas (47) via injection apparatus having a housing (36) which acts as a heat exchanger for causing part of the slush gas entering the injector to boil, so as to enable the gas to be driven under pressure into the working chamber (15).

Abstract: In an engine driven by liquefied gas, such as liquefied nitrogen or air, inlet means (31, 33) admits drive fluid to an expansion chamber defined by the volume between two relatively movable members (1, 28) guided for movement in a repetitive cycle by guide means (38, 40). The inlet means also allows a heat exchange liquid to be admitted to the chamber in which the liquid is in intimate contact with the drive fluid and gives up heat energy to the expanding drive fluid. The cooled heat-exchange liquid is withdrawn from the chamber, heated and re-circulated to the chamber. Part of said cycle includes a time period during which there is substantially no relative movement between the members (1, 28) and during which the chamber volume is maintained at or close to its minimum volume, the heat-exchange liquid and drive fluid being admitted to the chamber during said time period.

Abstract: An engine has a chamber (3) accommodating a rotor (5) providing shaft power from the expansion in the chamber (3) of a refrigerated or compressed drive fluid admitted to the chamber (3). A heat-exchange liquid is also admitted to the chamber (3). The heat-exchange liquid gives up heat energy to the expanding drive fluid in the chamber (3), and the cooled heat-exchange fluid is withdrawn from the chamber by a return pipe (16), passed through a heat exchanger (20) to raise its temperature to ambient and then reintroduced into the chamber (3).

Abstract: An engine has a chamber (3) accommodating a rotor (5) providing shaft power from the expansion in the chamber (3) of a refrigerated or compressed drive fluid admitted to the chamber (3). A heat-exchange liquid is also admitted to the chamber (3). The heat-exchange liquid gives up heat energy to the expanding drive fluid in the chamber (3), and the cooled heat-exchange fluid is withdrawn from the chamber by a return pipe (16), passed through a heat exchanger (20) to raise its temperature to ambient <and then reintroduced into the chamber (3).

Abstract: Breathing apparatus supplies air or oxygen to a patient and comprises a hand-held housing (10), a gas inlet on the housing, a gas outlet (12) on the housing (10), and a manual/automatic switch (16) on the housing for supplying gas either to a manually operable valve (40) or to a main valve (48) which delivers gas to the outlet on a cyclic basis. A trigger (22) on the housing (10) controls the supply of gas to the outlet through the manually operable valve (40).