Rogozinska, Alicja

The subject of the invention is a material based on Cu, Te and S for thermoelectric conversion having a γ-polymorphic modification of the β-tungsten type structure. The material according to the invention has a chemical formula Cu<6+δ>Te<3-x>S<1+x>, where 0 < x ≤ 1 and 0 ≤ δ ≤ 0.7. The invention refers also to a method for preparing of said material in which the elements Cu, Te, S are mixed in stoichiometric proportions, wherein the ratio of Cu : Te : S being respectively (6+δ):(3-x):(1+x), where 0 ≤ δ ≤ 0.7 and 0 < x ≤ 1, then the mixture is tightly sealed under vacuum in a quartz ampoule, followed by melting the elements mixture by heating to a temperature in the range from 1200 K to 1600 K, and annealing at this temperature for at least 5 hours to allow synthesis to take place in the liquid state, then a resulting ingot in the quartz ampoule is cooled down to room temperature and then it is grounded to a powder which is cold pressed and then the pressed powder is subjected to an annealing process by thermal treatment from 20 h to 1000 h at a temperature in the range of 700 K to 1000 K in vacuum or in protective atmosphere, after which it is cooled down to a room temperature resulting in an annealed material, that is later sintered with pressure by placing it in a graphite mold and heating it to temperatures in the range from 600 to 900 K under a pressure in the range from 20 to 200 MPa for a time ranging between 1 to 600 min, finally the resulting material is cooled down at a cooling rate ranging from 1 to 30 K/min.

Geothermal engine with one element for absorbing heat from an upper heat source and one element for discharging heat to a lower heat source, the geothermal engine being suitable to be placed within a borehole (17) and having a cooling medium circuit, a cylindrical housing (9) with a cylinder head (10), a working piston (1), a displacer (2) with a regenerator (3), a crankshaft, and connecting rods for the piston and displacer, a rock mass - cylinder head heat exchanger as well as a generator-starting device. The working piston discharges heat to lower heat source, while the rock mass - cylinder head heat exchanger (11) absorbs heat from the upper heat source. The cooling medium circuit comprises a pump, a casing pipe (13), and a central pipe (15). Inside the casing pipe (13), there is a flow space (14) for the heated cooling medium, while inside the central pipe (15), there is a flow space (16) for the cooled cooling medium, which constitutes the lower heat source and circulates over the upper surface of the working piston (1). The crankshaft (4) is enclosed within the engine's working chamber, where a working gas is present between the piston (1) and the displacer (2). The pump includes at least one suction valve (7) and at least one discharge valve (8).Method for obtaining energy from the rock mass using such a geothermal engine mounted in a borehole in which the movement of a working piston (1) is initiated and the flow and change in volume of a working gas located inside of the engine is forced providing mechanical energy needed to start the engine with the use of an external generator-starting device (19), powered from the surface and working in starting mode, then the generator-starting device (19) is switched to generating mode, then the compressed working gas is heated with heat obtained from the borehole and transfers said heat to cool cooling medium, converting the mechanical energy of the working piston movement with use of the generator-starting device (19) that is set to generating mode in the electrical energy, that is extracted with wires (20) on the surface and pumping heated cooling medium with use of at least one discharge valve (8) through the cooling medium circuit to the surface.

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