Mechanical liquid piston slow expansion compressor (1) defining a variable pneumatic volume (2) which forms a compressor (3) or an expander (4), a working gas (5) being able to enter said volume (2) via an input port (6) or exit from said volume (2) via an outlet port (7), characterised in that it comprises:
- A liquid cylinder (8) which can, directly or indirectly, pivot about a tilt axis (9) which is perpendicular to the axis of said cylinder (8) and which is secured to a static frame (40);
- A hydraulic piston (10) which can sealingly translate into the liquid cylinder (8) to form with the latter, a variable hydraulic volume (12) which is totally or partially filled with a working liquid (13);
- A gas and liquid reservoir (14) which is connected to the variable hydraulic volume (12) by a communication conduit (15), such that said reservoir (14) is mainly or totally filled with working liquid (13) when the variable hydraulic volume (12) is minimum, and is totally or partially filled with working gas (5) when the variable hydraulic volume (12) is maximum, the variation of absolute volume of the working gas (5) contained in the variable pneumatic volume (2) forming on the one hand, the variable pneumatic volume (2), and being on the other hand, approximately equal to the variation of absolute volume of the working liquid (13) contained in the variable hydraulic volume (12);
- Heat exchange and accumulation means (16) housed in the gas and liquid reservoir (14), said means (16) being able, on the one hand, to exchange heat with the working gas (5) or with the working liquid (13) and on the other hand, to temporarily store all or some of said heat;
- Heat export or input means (17) which take or which transfer, directly or indirectly, heat to the heat exchange and accumulation means (16) and/or to the working liquid (13) and/or to the working gas (5), said heat taken then being transferred to heating means (18) or said transferred heat having been taken beforehand to cooling means (19), said heating means (18) and said cooling means (19) being external to the gas and liquid reservoir (14);
- Filling means (20) which enable or prohibit the passage of working gas (5) from an intake plenum (21) to the gas and liquid reservoir (14) via the inlet port (6);
- Draining means (22) which enable or prohibit the passage of working gas (5) from the gas and liquid reservoir (14) to a repression plenum (62) via the outlet port (7);
- A connecting rod (11) a first rod end (29) of which is fixedly secured to the hydraulic piston (10), said rod (11) being approximately parallel to the longitudinal axis of said piston (10);
- Piston guiding means (23) which maintain the hydraulic piston (10) and the connecting rod (11) parallel to said cylinder (8), whatever the position of said piston (10) in said cylinder (8);
- A crankshaft (24) which can rotate about an axis parallel to the tilt axis (9) in at least one shaft bearing (25), and which has at least one crank (26) around which a second rod end (30) of the connecting rod (11) is articulated;
- At least one drive motor (27) which directly or indirectly rotates the crankshaft (24);
- Kinetic energy storage means (28), which are directly or indirectly connected to the crankshaft (24).