Heat engine, in particular for low-temperature operation for the utilisation of solar heat or waste heat from biological or industrial processes, with: at least two cylinder-piston units (2 - 5), which are configured to each contain an expansion fluid, which stands under a prestressing pressure and which changes its volume in the case of a change of temperature and thus moves the piston, a unit (16 - 20) for the individually controllable supply of heat to the expansion fluid of each cylinder-piston unit (2 - 5), and a control unit controlling the heat supply unit to alternately heat and cool each expansion fluid and thus move the pistons, wherein a common prestressing fluid can act on the pistons of all cylinder-piston units (2 - 5), which exerts a common prestressing pressure on the respective expansion fluid therein, characterized in that the prestressing fluid can be led from the cylinder-piston units (2 - 5) via first non-return valves in a manner known per-se to an entrance and via opposingly directed second non-return valves (12") to an exit (11") of a hydraulic load, in which it is subject to a pressure drop (Δp) between entrance and exit (11"), the control means comprises a first pressure gauge (22") for the pressure (p 2) of the prestressing fluid at the exit (11") of the load, the control means comprises a second pressure gauge for the pressure (p 1 of the prestressing fluid at the entrance of the load, the control means is configured to control the heating and cooling phases of the heat supply unit (16 - 20) at least according to the measured exit pressure (p 2), to hold it within a predefined first range (p 2,min, p 2,max), and the control means is configured to control the heating and cooling phases of the heat supply unit (16 - 20) further according to the measured entrance pressure (p 1), to hold it within a predefined second range (p 2,min, p 2,max), wherein the expansion fluid contains liquid carbon dioxide and the lower range limit (p 2,min) of said predefined first range is higher than or equal to the condensing pressure of carbon dioxide at the operating temperature. at least two cylinder-piston units (2 - 5), which are configured to each contain an expansion fluid, which stands under a prestressing pressure and which changes its volume in the case of a change of temperature and thus moves the piston, a unit (16 - 20) for the individually controllable supply of heat to the expansion fluid of each cylinder-piston unit (2 - 5), and a control unit controlling the heat supply unit to alternately heat and cool each expansion fluid and thus move the pistons, wherein a common prestressing fluid can act on the pistons of all cylinder-piston units (2 - 5), which exerts a common prestressing pressure on the respective expansion fluid therein, characterized in that the prestressing fluid can be led from the cylinder-piston units (2 - 5) via first non-return valves in a manner known per-se to an entrance and via opposingly directed second non-return valves (12") to an exit (11") of a hydraulic load, in which it is subject to a pressure drop (Δp) between entrance and exit (11"), the control means comprises a first pressure gauge (22") for the pressure (p 2) of the prestressing fluid at the exit (11") of the load, the control means comprises a second pressure gauge for the pressure (p 1 of the prestressing fluid at the entrance of the load, the control means is configured to control the heating and cooling phases of the heat supply unit (16 - 20) at least according to the measured exit pressure (p 2), to hold it within a predefined first range (p 2,min, p 2,max), and the control means is configured to control the heating and cooling phases of the heat supply unit (16 - 20) further according to the measured entrance pressure (p 1), to hold it within a predefined second range (p 2,min, p 2,max), wherein the expansion fluid contains liquid carbon dioxide and the lower range limit (p 2,min) of said predefined first range is higher than or equal to the condensing pressure of carbon dioxide at the operating temperature.