Abstract: A power control system for a hot gas engine of the type in which the power output is controlled by varying the mean pressure of the working gas charge in the engine has according to the present invention been provided with two working gas reservoirs at substantially different pressure levels. At working gas pressures below the lower of said levels the high pressure gas reservoir is cut out from the control system, and at higher pressures the low pressure gas reservoir is cut out from the system, thereby enabling a single one-stage compressor to handle gas within a wide pressure range at a low compression ratio.

Abstract: A heater head for a multi-cylinder double acting hot gas engine in which each cylinder is surrounded by an annular regenerator unit, and in which the tops of each cylinder and its surrounding regenerator are interconnected by a multiplicity of heater tubes. A manifold for the heater tubes has a centrally disposed duct connected to the top of the cylinder and surrounded by a wider duct connecting the other ends of the heater tubes with the regenerator unit.

Abstract: A heater head for a multi-cylinder solar radiation powered hot gas engine comprises tubes connecting cylinder and regenerator tops. Each tube comprises three parts. A first part of each tube extends along an involute curve on a cone. A second part extends radially outwardly on the same cone while a third part extends radially inwardly and downwardly on another cone.

Abstract: A plate-type heat exchanger for hot gas engines of the Stirling type includes stacked pairs of elongated rectangular plates joined at the longitudinal edges with spaces between the paired plates constituting the cold gas flow passages and spaces between plate pairs constituting the hot gas flow passages. Paired plates have mirror image protrusions protruding from the respective abutted longitudinal margins, which protrusion form the internal cold gas flow passages and also provide the spacing between adjacent abutting pairs that constitutes the hot gas flow passages. Abutting plates of adjacent stacked pairs are joined at the abutting transverse margins.