High-performance low-temperature Stirling engine with design adaptation to increased load requirements

Abstract

Heat engine (M), comprising a high-performance low-temperature Stirling engine with a pressure chamber formed by at least one housing part (1A, 2A, 1A-2A), which is pressure-tight from the environment and filled with a working fluid (FL), and which delivers mechanical power on a hot side (HS) by external heat input at a higher temperature and on a cold side (KS) by external heat dissipation at a lower temperature compared to the higher temperature, wherein the at least one pressure chamber is divided into two fluid-tight and pressure-tight working chambers by periodically movable pistons (3, 4), wherein the working chambers are separated from each other on the fluid side by the pistons (3, 4) and are operatively connected on the pressure side via the pistons (3, 4), wherein one of the pistons (3, 4) on the hot side (HS) is heated by the external heat input relative to the other piston (3, 4) located on the cold side (KS).4) is brought to a higher temperature or kept at a higher temperature, and the other piston (3, 4) arranged on the cold side (KS) is kept at a lower temperature or brought to a lower temperature relative to the piston (3, 4) arranged on the hot side (HS), wherein the pressure fluctuations generated in the working chambers periodically act on the movable pistons (3, 4) which are operatively connected to eccentric shafts (5, 6) having eccentrics (5A, 6A), wherein the eccentric shafts (5, 6) are arranged parallel to each other with respect to their longitudinal axes (5B, 6B), characterized in that an eccentric center (5C, 6C) of the eccentric (5A, 6A) of one eccentric shaft (5, 6) forms a predetermined angular offset (V) relative to the other eccentric shaft (5, 6), wherein the angular offset (V) between the eccentric centers (5C, 6C) the eccentric (5A, 6A) and the centers of the longitudinal axes (5B,6B) the one eccentric wave (5, 6) is formed relative to the other.

Description

[0001] The invention relates to a heat engine, in particular a high-performance low-temperature Stirling engine.

[0002] The increasing use of renewable energies in Germany is progressing at different rates depending on the type of energy. Expansion for electricity generation has been more intensive, partly due to the better integration options into the nationwide electricity grid. In contrast, the use of solar thermal energy is largely tied to the prevailing heat demand at the point of generation.

[0003] The energy supply in commercial and residential buildings generally requires heat for heating and hot water, as well as electricity for lighting, information, communication, and power. Demand fluctuates depending on the time of day and year. The amount of energy required for heating is generally about four times that of electricity.

[0004] When assessing the share of renewable energies in relation to total energy demand, the development potential of integrating ambient heat into the energy supply becomes apparent. On the path to a fully renewable energy supply, in addition to efficiency improvements, the storage of large quantities of energy and the ability to transform between different energy types are fundamental prerequisites. Currently, only electrical energy possesses the property of being a universal energy source, capable of being converted into all other energy types. However, despite enormous international development efforts, the direct storage of large quantities of energy is not yet economically feasible on a large scale.

[0005] In contrast, while heat can already be stored in large quantities cost-effectively, its conversion requires, firstly, complex drive units such as steam turbines, steam engines, or high-performance low-temperature Stirling engines, and secondly, the temperature must be so high that direct use of ambient heat is impossible. Thus, the conventional combustion of gas, oil, or solid fuels is ultimately used. Even the solar-powered Stirling engines, which are occasionally in use, require temperature differences between the hot and cold sides that can only be achieved through optical concentration using complex concave mirrors and their constant tracking.

[0006] The economical use of solar thermal energy for energy conversion requires the use of standard components that operate effectively at temperature levels of approximately 50 to 70°C. Solutions that can utilize the waste heat from a thermal energy conversion process as usable heat are considered particularly effective.

[0007] Stirling engines are well-known for deriving their power solely from pressure and volume changes caused by temperature variations. Conventional Stirling engines require complex mechanics to function. This results in Stirling engines operating at high pressures being very heavy and large.

[0008] Low-temperature Stirling engines used for power generation currently require temperatures well above 100°C. Helium, air, nitrogen, and similar gases are used as working fluids. These media closely approximate theoretically ideal gases.

[0009] The publication DE 10 2009 057 210 B4 describes a Stirling evaporator heat engine consisting of at least one heat engine which is mechanically constructed like a Stirling engine, wherein a working fluid is used whose boiling point is chosen such that it is gaseous in the hot areas of the heat engine and exists as a liquid, transcritical or supercritical phase in the cold areas.

[0010] The publication EP 2 333 285 A1 discloses a Stirling evaporator heat engine with external heating, operating on a Stirling-like principle. The heat engine consists of at least one heat engine mechanically constructed like a Stirling engine. A working fluid is used whose boiling point is selected such that it is gaseous in the hot sections of the heat engine and liquid, transcritical, or supercritical in the cold sections. The heat engine simultaneously achieves the advantages of Stirling engines and those of Rankine-type engines, in particular a sustained reduction of the minimum heater temperature to approximately 150°C. The system is particularly suitable for use in combined heat and power plants, uninterruptible power supplies, emergency power generators, and vehicle power supplies.

[0011] Publication CN 102 418 621A describes a Stirling engine with an eccentric shaft rotating ring. A cylindrical air cylinder comprises four chambers: two inner chambers and two outer chambers. The working fluid is high-pressure carbon dioxide. Because the thermal expansion and contraction of the working fluid occur simultaneously, and the working fluid always flows in the same direction, the Stirling engine exhibits good motion stability without pulsation.

[0012] Furthermore, publications EP 1 592 8 75 B1 and US 6 701 721 B1 describe analogously a Stirling engine-driven heat pump with a fluid connection. A heating and cooling device is described, and in particular one based on a Stirling engine as the drive motor, which drives the compressor of a vapor compression heat pump system to pump heat from a cooler mass to a hotter mass. A single working fluid, preferably carbon dioxide, can be used both as the working fluid for the Stirling engine and as the refrigerant.

[0013] Document DE10 2006 061 509 A1 further describes a thermal displacement engine with external heat energy input. The thermal displacement engine is designed in the manner of a Stirling engine. A novel working fluid heater is proposed, which makes it possible to heat a working fluid to a significantly higher pressure and temperature level compared to a conventional working fluid heater.

[0014] German patent DE 806 611 B discloses a Stirling engine in which two double pistons are arranged via an eccentric body on a single eccentric fixed to a main shaft. Heat is supplied and removed via heaters and coolers. Due to the specific arrangement, only a fixed offset of 90° is possible.

[0015] From the publication DE 38 34 070 A1, another Stirling engine is known, in which two double pistons, each connected via rods, are connected via connecting rods to a wobble plate, which is eccentrically connected to a single crankshaft.

[0016] Finally, another Stirling engine can be found in publication FR 2 835 570 A1, in which a periodically movable piston divides a pressure chamber into two fluid-tight working chambers, but is additionally periodically moved from a hot side to a cold side and back by another piston. The piston is connected to a shaft via an eccentric. Furthermore, an arrangement is disclosed in which several pistons are arranged on eccentrics at several coaxial sections of the shaft. An offset between adjacent eccentric shafts can be achieved via a synchronizing pinion with several gears. The object of the present invention is to provide a Stirling engine, in particular a high-performance low-temperature Stirling engine, which, despite the very high pressure within the Stirling engine at the higher theoretical work capacity, has a compact design.

[0017] The invention is based on a heat engine with a pressure chamber formed by at least one housing part, which is pressure-tight from the environment and filled with a working fluid, and which delivers mechanical power on a hot side by external heat input at a higher temperature and on a cold side by external heat removal at a lower temperature compared to the higher temperature, wherein the at least one pressure chamber is divided into two fluid-tight and pressure-tight working chambers by periodically movable pistons.

[0018] The working chambers are separated from each other on the fluid side by the pistons and are in operative communication on the pressure side via the pistons, wherein one of the pistons on the hot side is brought to or kept at a higher temperature than the other piston on the cold side by the external heat input, wherein the other piston on the cold side is kept at or brought to a lower temperature than the piston on the hot side, wherein the pressure fluctuations generated in the working chambers act periodically on the movable pistons, wherein the pistons are in operative communication with eccentric shafts having eccentrics, wherein the eccentric shafts are arranged parallel to each other with respect to their longitudinal axes.

[0019] According to the invention, the eccentric center of one eccentric shaft forms a predetermined angular offset relative to the other eccentric shaft, wherein the angular offset is formed between the eccentric centers of the eccentrics and the centers of the longitudinal axes of the two eccentric shafts. Preferably, the predetermined angular offset is between 90° and 170°.

[0020] According to the invention, it is also provided that each of the pistons has parallel opposing piston end faces, wherein two piston end faces of the pistons lying on the same side form an energy storage space between the hot side and the cold side.

[0021] According to the invention, the energy storage spaces are designed as thermal regenerators.

[0022] It is provided that the thermal regenerators, designed as energy storage spaces, are integrated into the housing in one embodiment or arranged outside the housing in another embodiment.

[0023] The movable pistons are arranged in cylinders which are connected on the pressure side via connecting openings to the energy storage spaces designed as thermal regenerators.

[0024] In a preferred embodiment of the invention, cylinders formed in one or more parts each form a piston interior, in which each eccentric shaft is assigned an eccentric which is arranged together with the eccentric shaft in the piston interior, wherein the piston interiors are designed to be pressure-tight and fluid-tight with respect to the working chambers, wherein the forces acting on the piston end faces of the respective piston lead to the periodic movement of the piston and the respective piston acts on the eccentric shafts depending on the position of the eccentric.

[0025] According to the invention, the eccentric shafts are further provided that they are mounted in the housing parallel to each other with respect to their longitudinal axes via bearings adjacent to the piston interior, with the eccentric shafts extending out of the piston interior at least at one end. In another embodiment, to prevent potential leaks at the shaft output, an encapsulated magnetic coupling is arranged, through which power is delivered to the generator or the generator shaft. In a further embodiment, the generator can also be integrated into the pressure zone of the housing.

[0026] The heat engine is characterized in particular by the fact that the predetermined offset is fixed by gears arranged on the eccentric shafts outside the housing, which are meshed together according to the predetermined offset.

[0027] Preferably, a sliding bearing bushing is arranged in the respective piston interior between the eccentric of the eccentric shafts and the inner surfaces of the pistons.

[0028] The forces acting on the respective pistons of the heat engine are aligned with respect to the longitudinal axes of the eccentric shafts, whereby the forces act orthogonally as transverse forces on the eccentric shafts.

[0029] It is intended that the working fluid in the pressure chamber is liquid supercritical carbon dioxide, xenon, or ethene.

[0030] In particular, the working fluid is carbon dioxide CO2, which is used in the working spaces and energy storage spaces of the pressure chamber at an operating point that has a temperature of 30°C at a pressure of 7.2 MPa (72 bar), as is explained in more detail in the description.

[0031] In one embodiment, several heat engines are arranged separately from each other in a cascade in the longitudinal direction of the eccentric shafts, as is also explained in more detail in the description.

[0032] According to the invention, the heat engine is a Stirling engine, in particular a high-performance low-temperature Stirling engine, which is structurally modified according to the boundary conditions to be observed, whose operating temperature is < 50°C and which already reaches its optimal operating window at 27° to 37°C, whereby temperature differences between a hot and cold side of the Stirling engine of less than 10K are required, as explained below.

[0033] For an ideal gas, a temperature increase from 30°C to 31°C results in a pressure change (p1 / p2=T1 / T2) or a volume change (V1 / V2=T1 / T2) of only about 0.3%.

[0034] However, the high-performance low-temperature Stirling engine according to the invention uses a working fluid FL, in particular carbon dioxide CO2, which already changes its pressure by approximately 2.3% and its volume by approximately 16.5% in a small temperature range, for example 30°C to 31°C, thereby achieving a theoretical work capacity approximately 400 times higher.

[0035] The high-performance low-temperature Stirling engine according to the invention is characterized by its high compactness and enables high power output even at temperatures below 50°C. Xenon or ethene can also be used as the working fluid (FL).

[0036] The invention is described below with reference to the associated Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5, Fig. 6, Fig. 7 to Fig. 8 explained.

[0037] They show: Fig. 1 a perspective view of a high-performance low-temperature Stirling engine in one possible embodiment in an external view; Fig. 2 a cut AA according to Fig. 1. through the high-performance low-temperature Stirling engine; Fig. 3 a cut BB according to Fig. 2 by the high-performance low-temperature Stirling engine; Fig. 4 a cut CC according to Fig. 2 by the high-performance low-temperature Stirling engine; Fig. 5 a cut FF according to Fig. 2 by the high-performance low-temperature Stirling engine; Fig. 6 a section GG according to Fig. 2 by the high-performance low-temperature Stirling engine; Fig. 7 a cut HH according to Fig. 2 by the high-performance low-temperature Stirling engine; Fig. 8 a cut KK according to Fig. 6 through the high-performance low-temperature Stirling engine.

[0038] The invention relates to a high-performance low-temperature Stirling engine M (cf. Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5, Fig. 6, Fig. 7, Fig. 8, Fig. 9, Fig. 10, Fig. 11, Fig. 12, Fig. 13, Fig. 14, Fig. 15, Fig. 16, Fig. 17, Fig. 18, Fig. 19, Fig. 20, Fig. 21, Fig. 22, Fig. 23, Fig. 24, Fig. 25, Fig. 26, Fig. 27, Fig. 28, Fig. 29, Fig. 30, Fig. 31, Fig. 32, Fig. 33, Fig. 34, Fig. 35, Fig. 36, Fig. 37, Fig. 38, Fig. 39, Fig. 40, Fig. 41, Fig. 42, Fig. 43, Fig. 44, Fig. 45, Fig. 46, Fig. 47, Fig. 48, Fig. 49, Fig. 50, Fig. 51, Fig. 52, Fig. 53, Fig. 54, Fig. 55, Fig. 56, Fig. 57, Fig. 58, Fig. 59, Fig. 60, Fig. 61, Fig. 62, Fig. 63, Fig. 64, Fig. 65, Fig. 66, Fig. 67, Fig. 68, Fig. 69, Fig. 70, Fig. 71, Fig. 72, Fig. 73, Fig. 74, Fig. 75, Fig. 76, Fig. 77, Fig. 78, Fig. 79, Fig. 80, Fig. 81, Fig. 82, Fig. 83, Fig. 84, Fig. 85, Fig. 86, Fig. 87, Fig. 88 to Fig. 89, which is able to convert quantities of heat into electrical energy even at low temperature levels, and thereby achieve a power level to significantly support the electrical energy demand, in particular an exemplary building supply.

[0039] A comprehensive solution is planned for a commercial building, combining the supply of heat and electricity. This preferably involves first capturing ambient heat using a solar thermal system (not shown) and storing it in an external hot water buffer for the high-performance low-temperature Stirling engine M.

[0040] Additional heat requirements of the building are met by a gas condensing boiler or alternatively by a heat pump and are also stored in the external hot water buffer tank.

[0041] According to the invention, the special behavior of a working fluid FL, which, unlike ideal gases, has a supercritical state, is used for energy conversion.

[0042] When a liquid working fluid is heated above its boiling point, it generally transitions into a gaseous state. If the existing pressure prevents evaporation, the substance enters a special state, which applies to both liquids and gases. During this transition to the "supercritical" state, the working fluid (FL) expands with an extreme increase in volume, similar to what occurs during evaporation, and simultaneously exerts a force comparable to that experienced during the expansion of liquids. From an energy perspective, the so-called supercritical state thus combines technically usable advantages of both liquids and gases.

[0043] For example, carbon dioxide CO2 already forms this supercritical state as a property at an operating point at a temperature of 30°C and a pressure of 7.2 MPa (72 bar) and proves to be particularly suitable for the invention described below.

[0044] A novel high-performance low-temperature Stirling engine solution M, which is explained below, utilizes the special expansion properties of liquid carbon dioxide CO2 in the supercritical state and simultaneously copes with the associated high load on the technical engine components through a novel design.

[0045] The high-performance low-temperature Stirling engine M is operated on the hot side HS (see below). Fig. 1) operated at a minimum of 32°C. For this purpose, the hot side HS is preferably heated by the external hot water buffer (not shown).

[0046] Via a schematically indicated piping system L (see Fig. 1 and 6 to 8) heat is supplied to the hot side HS of the high-performance low-temperature Stirling engine M, as will be explained in detail later.

[0047] A cold side KS of the high-performance low-temperature Stirling engine M (see Fig. 1) is cooled by the cold water buffer to a maximum temperature of 30°C. For this purpose, the cold side KS is cooled by the external cold water buffer, for example, inactively and / or actively.

[0048] Via a piping system L designed analogously to the hot side HS (see above). Fig. 1 and 6 to 8) heat is removed from the cold side KS of the high-performance low-temperature Stirling engine M, as will also be explained later.

[0049] This special operating mode enables, according to the invention, the normal function of the high-performance low-temperature Stirling engine M even with a minimum temperature difference ΔT between the hot side HS and the cold side KS of 2°K.

[0050] The required heat energy demand on the hot side HS and the cold side KS of the high-performance low-temperature Stirling engine is realized by correspondingly high volume flows from at least the external hot water storage tank or both external buffer storage tanks, the external hot water storage tank and the external cold water storage tank.

[0051] Since the high-performance low-temperature Stirling engine M continuously cools its hot side HS and heats its cold side KS during operation, heat is ultimately transferred from the external hot water buffer to the external cold water buffer. According to the invention, for example, a heating circuit of the building is supplied from the cold water buffer, so that the building acts as a cooler.

[0052] In other words, the heat transported to the cold side KS of the high-performance low-temperature Stirling engine M is dissipated, for example, via the building's heating circuit, which is connected to the cold water buffer tank. Thus, the waste heat from the cold side KS of the high-performance low-temperature Stirling engine M is advantageously used as usable heat for building heating.

[0053] The building heating system is designed to be sufficiently large to ensure adequate heat transfer at a maximum flow temperature of 30°C for the cold side KS of the high-performance low-temperature Stirling engine M.

[0054] In a preferred embodiment, the high-performance low-temperature Stirling engine M also drives a generator which feeds the generated electrical energy into the grid, in particular into a house network.

[0055] The desired temperature of the hot side HS, in particular at least 32°C or higher, can be achieved either by mixing the medium L flowing in from the external hot water buffer. ZU (cf.) Fig. 1 and Fig. 7) and the medium L flowing back from the hot side HS AB , or by the flow rate of the medium flowing in from the external hot water buffer L ZU - without any additives - can be set.

[0056] These temperature settings allow the instantaneous power output of the high-performance low-temperature Stirling engine M or the feed-in power of the generator to be adjusted to the desired demand.

[0057] The solution according to the invention fulfills the following functions: Economical energy storage is ensured via the hot water buffer tank. Furthermore, efficient conversion of ambient heat into electrical energy is achieved. In addition, the temporal decoupling of heat generation and heat demand, as well as the demand for electrical energy, is implemented.

[0058] The high-performance low-temperature Stirling engine M in detail: Conventional high-performance, low-temperature Stirling engines feature a piston-crankshaft assembly that absorbs the pressure of the working fluid via the piston crown. A piston pin is inserted into the piston. This pin transmits the force via a bearing, typically a plain bearing or a needle bearing, to the upper end of the connecting rod. The connecting rod itself is supported against the crankshaft and transmits the force from the lower end of the connecting rod, via bearings, to the crankshaft. The resulting torque is applied to the crankshaft journal as rotational work.

[0059] When using carbon dioxide (CO2) in the planned way, considerable pressures arise, especially in the supercritical state of the working fluid, which are higher than with conventional working fluids (such as nitrogen, helium or air) that do not reach a supercritical state, resulting in immense forces acting on the piston base of the piston.

[0060] In conventional high-performance low-temperature Stirling engines, the components of the operating chain – piston pin, piston pin bearing, and the upper connecting rod area – are designed to be relatively small, which is why the surface pressures, bending stresses, and shear stresses acting on them, under the now higher pressures, lead to their overload.

[0061] To avoid this overload, the power can be reduced, but this negatively reduces the attractiveness of the high-performance low-temperature Stirling engine.

[0062] In order to safely absorb the high forces, it is also possible, as has mostly been done in practice so far, to oversize the components, which adversely increases size, weight and costs, thus reducing the economic efficiency of the high-performance low-temperature Stirling engine.

[0063] A novel design of a high-performance low-temperature Stirling engine M dispenses with piston pins, piston pin bearings and connecting rods.

[0064] The new high-performance low-temperature Stirling engine M is shown in a perspective exterior view in Fig. 1 and in a sectional view in Fig. 2 is shown, whereby it is recommended that the following description be viewed in a summary of the Fig. 1, Fig. 2, Fig. 3, Fig. 4 to Fig. 5 to understand.

[0065] With regard to the figures, it is stated that the high-performance low-temperature Stirling engine M is designed as a compact component with a height x width x depth (H / W / D) of 25 cm each, with a temperature difference ΔT of the working fluid AF of 10K between the hot side HS and the cold side KS.

[0066] With such a compact component measuring 25 cm x 25 cm x 25 cm, the high-performance low-temperature Stirling engine M (without cascading) can achieve a power output of approximately 2 kW when supercritical carbon dioxide CO2 is used as the working fluid AF, as explained.

[0067] In the high-performance low-temperature Stirling engine M (see Fig. 1) The compressed working fluid FL, in particular supercritical carbon dioxide CO2, is alternately transferred from a cold control cylinder 2, by means of a control piston 4 and a working piston 3 of a warm working cylinder 1, via the regenerators 9, 10 into the warm working cylinder 1 and from the warm working cylinder 1 into the cold control cylinder 2. A first regenerator R1 has a hot side R1-HS analogous to the warm working cylinder 1 and a cold side R1-KS analogous to the cold control cylinder 2.

[0068] A second regenerator R2 also has a hot side R2-HS analogous to the warm working cylinder 1 and a cold side R2-KS analogous to the cold control cylinder 2.

[0069] The two regenerators R1, R2 (see below) Fig. 1) form the heat storage mass of the high-performance low-temperature Stirling engine M of the heat engine.

[0070] In principle, it is possible to operate the Stirling engine without regenerators, but then the heat storage mass is lacking to operate the Stirling engine efficiently.

[0071] The high-performance low-temperature Stirling engine M is a device known per se which can generate mechanical energy from a temperature difference of a working fluid pumped back and forth between two pistons 3, 4.

[0072] This process requires a cold source and a heat source. In the high-performance low-temperature Stirling engine M according to the invention, the cold source is realized by the cold side KS. The heat source is realized by the hot side HS.

[0073] The high-performance low-temperature Stirling engine has the aforementioned two cylinders 1 and 2, namely the cold control cylinder 2 (cold side KS) and the warm working cylinder 1 (hot side HS), see section FF according to... Fig. 5 and the section BB according to Fig. 3. The cold and heat are supplied to the two cylinders 1, 2 by the cold sides KS and hot sides HS of the regenerators R1, R2, which are connected to the respective cylinders 1, 2 via connecting openings 12, 13 (see Figure 1). Fig. 1 and Fig. 4, Fig. 5) are connected.

[0074] According to the Fig. 6 to Fig. 7 (sections GG and HH) the heat supply and heat removal are ensured via at least one conduit system L each, which is formed in the housing 1A of the working cylinder 1 or in the housing 2A of the control cylinder 2, around the respective inlets of the regenerators R1 and R2 on the hot side HS and preferably also on the cold side KS in the housing 1A and 2A of the high-performance low-temperature Stirling engine M. According to Fig. 8 corresponding line branches L1 are formed in the housings 1A, 2A to increase the effect of heat input and heat dissipation.

[0075] At least on the hot side (HS) there is at least one inlet opening (L). Zu and a drain opening L AB intended to (cf. Fig. 1) to be able to supply a heat-conducting medium, in particular water, to the high-performance low-temperature Stirling engine M, which, after releasing its heat, flows through the drain opening L AB is dissipated. Preferably, as already mentioned, this heat is taken from a circuit of a solar thermal system, which is stored in a hot water buffer of the solar thermal system.

[0076] Additionally, on the cold side there is KS (see below). Fig. 1) also at least one inlet opening L Zu and a drain opening L AB intended to (cf. Fig. 1) to be able to supply the high-performance low-temperature Stirling engine M with a heat-dissipating medium which, after absorbing its heat, flows through the drain opening L ABThis waste heat is dissipated. Preferably, as mentioned, this waste heat is advantageously used as usable heat for building heating by the cold side KS of the high-performance low-temperature Stirling engine M.

[0077] In a preferred embodiment of the invention (see Fig. 2) in each of the two cylinders 1, 2 the pistons 3, 4 are arranged, which by their translational movement each drive an eccentric shaft 5, 6 rotationally, which in a preferred embodiment of the invention are each arranged in a piston interior 3A, 4A.

[0078] On each of the eccentric shafts 5, 6 a gear 9, 10 is arranged, which mesh together, thus being toothed together.

[0079] According to the invention, it is further provided that each of the eccentric shafts 5, 6 has an eccentric 5A, 6A, wherein the eccentric 5A of the first eccentric shaft 5 is arranged offset from the eccentric 6A of the second eccentric shaft 6 - predefinable - between 90° and 170°, in a so-called offset V.

[0080] The predetermined offset V of the eccentrics 5A, 5B of the eccentric shafts 5, 6, selected according to various boundary conditions, is fixed by the two correspondingly intermeshing gears 9, 10.

[0081] In the Fig. 1, Fig. 2, Fig. 3, Fig. 4 to Fig. In the embodiment shown in Figure 5, the eccentric 5A of the first eccentric shaft 5 is arranged offset by 90° relative to the eccentric 6A of the second eccentric shaft 6.

[0082] Due to the offset V (in the exemplary embodiment according to Fig. With a 90° offset V), a continuous translational movement of the working pistons 2, 4 is converted into a rotational movement of the eccentric shafts 5, 6, since the working piston 2 is connected via gears 9, 10 to the second eccentric shaft 6 and eccentric 6A located inside the control piston 4, and thus to the control piston 4. The offset V thus accounts for the time delay of the control piston 4 relative to the working piston 2.

[0083] According to the well-known Stirling principle, a usable torque can be taken from the eccentric shafts 5, 6 or from the gears 11, 12 during the operation of the high-performance low-temperature Stirling engine M.

[0084] In a preferred embodiment of the invention, the piston interior contains 3A, 4A (see Fig. 2) Plain bearing bushings 7, 8, preferably provided with a Teflon inner coating 7A, 8A, are arranged between the eccentrics 5A, 6A of the eccentric shafts 5, 6 and the pistons 3, 4. The plain bearing bushings 7, 8 advantageously reduce the friction between the eccentric shafts 5, 6 and the inner surfaces of the pistons 3, 4.

[0085] Since the design according to the invention does not require a connecting rod, this principle can be used with higher working fluid pressures than before, as will be explained below.

[0086] The high-performance low-temperature Stirling engine M thus has a pressure chamber formed by at least one housing part 1A, 2A, 1A-2A, which is pressure-tight from the environment and filled with the working fluid FL, and which delivers mechanical power on the hot side HS by external heat input at a higher temperature and on the cold side KS by external heat removal - at a lower temperature compared to the higher temperature, wherein the at least one pressure chamber is divided into two fluid-tight and pressure-tight working chambers by periodically movable pistons 3, 4.

[0087] The working chambers are separated from each other on the fluid side by the pistons 3, 4 and are operatively connected on the pressure side via the pistons 3, 4, wherein one of the pistons 3, 4 on the hot side HS is brought to a higher temperature by the external heat input compared to the other piston 3, 4 arranged on the cold side KS and the other piston 3, 4 arranged on the cold side KS is kept at a lower temperature compared to the piston 3, 4 arranged on the hot side HS, wherein the pressure fluctuations generated in the working chambers act periodically on the translationally movable pistons 3, 4, which are operatively connected to each other by parallel rotating eccentric shafts 5, 6, wherein the parallel eccentric shafts 5, 6 are arranged eccentrically to each other in a predefinable offset V in the longitudinal direction of the eccentric shafts 5, 6.

[0088] It is provided that each of the pistons 3, 4 has parallel opposing piston end faces A3, A4, wherein two piston end faces A3, A4 on the same side of the pistons 3, 4 each form an energy storage space located between the hot side HS and the cold side KS.

[0089] According to the invention, the energy storage spaces are designed as heat exchangers, in particular as thermal regenerators R1, R2 (cf. Fig. 1 and 2).

[0090] The energy storage spaces of the thermal regenerators R1, R2 are preferred (as in the Fig. 1 and Fig. 2 shown) are integrated into the housing 1A, 2A, 1A-2A, or they are arranged outside the housing 1A, 2A, 1A-2A (not shown).

[0091] During operation of the high-performance low-temperature Stirling engine M, the regenerators R1 and R2, using the working fluid carbon dioxide CO2, operate at a pressure of approximately 7.2 MPa (72 bar) at the specified operating point and a temperature of 30°C.

[0092] Depending on the temperature on the hot side R1-HS, R2-HS and the cold side R1-KS, R2-KS (see below). Fig. 1) and the operating state of the high-performance low-temperature Stirling engine M, the pressures in the regenerators R1 and R2 are temperature-dependent and lie between approximately 7.0 MPa (70 bar) and 7.5 MPa (75 bar), whereby, according to the Stirling principle, between the opposing end faces A3 of the working piston 3 (see Fig. 2) and the opposite end faces A4 of the control piston A4 (see Fig. 2) a pressure difference Δp exists that ensures the maintenance of the Stirling cycle.

[0093] It is intended that carbon dioxide as working fluid FL in the working spaces of the pressure chamber and the energy storage chambers fluctuates temperature-dependently, preferably with a temperature difference ΔT between 2K and 10K between the hot side HS and the cold side KS of the pistons 3, 4, between 7.0 MPa (70 bar) and 7.5 MPa (75 bar), wherein the pressure fluctuations are caused by the temperature difference ΔT between the hot and cold sides HS, KS at a temperature on the hot side HS of a maximum of 37°C and a temperature on the cold side KS of a minimum of 27°C.

[0094] The pressure differences Δp (p31-p32 and p41-p42) (see Fig. 1) However, due to the constructive design, the pressures p31, p32 applied to the opposing end faces A3 of the working piston 3 and the pressures p41, p42 applied to the opposing end faces A4 of the working piston 4 are relatively low.

[0095] The force F resulting from the remaining pressure difference Δp also acts, due to the design of the high-performance low-temperature Stirling engine M, on the respective pistons 3, 4 and not on the respective eccentric shafts 5, 6. The force F is dependent on the position of the eccentric 5A, 6A (see Fig. 2, Fig. 3, Fig. 4, Fig. 5) transferred to the eccentric shaft 5, 6.

[0096] The longitudinal axes 5B, 6B of the eccentric shafts 6, 7 lie transversely to the force F acting on the eccentrics 5A, 6A and the eccentric shafts 6, 7 via the respective pistons 3, 4. Therefore, the force difference acting on the eccentric shafts 6, 7 is relatively small. Thus, it is advantageously achieved that the transverse forces acting on the pistons 3, 4 are minimized.

[0097] According to the invention, the lower mechanical force transmission of the respective piston 3, 4 to the eccentrics 5A, 6A and the eccentric shafts 6, 7 and thus to the eccentric shaft bearings 5D, 6D (cf. Fig. 4 and Fig. 5) a reduction in the number of components is possible, making it possible to form a compact assembly that can withstand the high operating pressures between 7.0 MPa (70 bar) and 7.5 MPa (75 bar).

[0098] This makes it possible to operate the high-performance low-temperature Stirling engine M with a working fluid FL which is in a supercritical state (e.g. CO2), allowing the high-performance low-temperature Stirling engine M to be operated at high pressures, low temperatures and small temperature differences.

[0099] The heat exchangers, especially the regenerators R1 and R2, in detail: In order to ensure the performance of the high-performance low-temperature Stirling engine M with a small temperature difference between hot and cold sides HS, KS and small component size, the necessary amount of heat must be supplied to the hot side HS by means of a relatively large volume flow, whereby the flow resistance in the regenerators R1, R2 should be as small as possible.

[0100] A reduced temperature difference on the two sides of the regenerator R1, R2 proportionally reduces its transmission power.

[0101] Reducing the size of the regenerators R1 and R2 also results in a reduction of the transmission power, as less surface area is available for heat transfer.

[0102] A smaller design of the regenerator R1, R2 can increase the transfer area, but it also creates increasing capillary effects and thus increases the mechanical resistance when the working fluid FL flows through the regenerators R1, R2.

[0103] The following constructive embodiment according to the invention advantageously combines these conflicting boundary conditions as follows.

[0104] The in the Fig. 1 and Fig. The two regenerators R1 and R2 shown allow for flow with a relatively high volume flow rate at low mechanical resistance and a large surface area for heat transfer, while maintaining an overall compact design of the regenerators R1 and R2.

[0105] Recuperative regenerators R1 and R2 are proposed. As the working gas flows through them, they extract heat energy from the working gas, which has been heated by the supply of heat energy, cool it down, and recuperatively store at least part of the extracted heat energy in the storage mass arranged in the respective energy storage spaces of the regenerators R1 and R2.

[0106] The heat energy stored in this recuperative manner is supplied again from the heat energy stored in the storage mass when the working fluid FL, which has been cooled by the removal of heat energy, flows through it.

[0107] A heat exchanger is proposed, which in particular functions as a thermal regenerator R1, R2 of a high-performance low-temperature Stirling engine M and which has at least one housing part 1A, 2A, 1A-2A in which an energy storage space is formed in which a storage mass for heat storage is arranged, wherein the heat exchanger is a solid-state heat storage device with the described recuperative properties, the storage mass of which is made of a highly conductive, preferably metallic or non-metallic material.

[0108] In one embodiment, the storage mass is formed from a porous aluminum body arranged in the at least one housing part 1A, 2A, 1A-2A, wherein the aluminum has pore sizes from 0.14 mm to 3.00 mm and an internal surface area between 20,000 and 2,500 m² / m³. A barrier is constructed between the porous aluminum body and an inner wall surface of the heat exchanger R1, R2 to prevent the working fluid AF from flowing past the porous aluminum body.

[0109] In another embodiment, the storage mass is provided for as a bed of compact or hollow metallic or non-metallic spheres of the same or different diameter made of steel, aluminum or glass, which is between 0.5 mm and 20 mm.

[0110] In the second design variant, the surface of the spheres is provided to be completely smooth, smooth and partially structured, or completely structured.

[0111] Advantageously, in the second embodiment variant, the spheres are embedded in an inner surface of the inner wall of the heat exchanger, so that marginal flow channels in the heat exchanger are closed by embedding the spheres in the edge area of ​​the heat exchanger.

[0112] According to a first embodiment, a thread is arranged on the inner surface of the inner wall of the heat exchanger, the pitch of which between two thread crests is equal to the largest diameter of the metallic or non-metallic spheres, so that the spherical surface of the metallic or non-metallic spheres lies at least partially in the thread of the internal thread, thereby closing the marginal flow channels in the heat exchanger.

[0113] According to the following embodiment variants, a layer of a shape-variable material with a predefinable layer thickness is arranged on the inner surface of the inner wall of the heat exchanger, onto which the spheres imprint their surface shape, thereby closing the edge flow channels in the heat exchanger.

[0114] In these design variants, the layer is made of a permanently elastic, plastic, thermally variable, or chemically variable material.

[0115] In a second embodiment, it is provided that the layer is made of a permanently elastic material, in particular rubber or soft plastic.

[0116] In a third embodiment, the layer is made of a plastic material, in particular tin.

[0117] In a fourth embodiment, the layer is made of a thermally variable material, in particular a plastic or wax.

[0118] Finally, a fifth embodiment provides that the layer is made of a chemically modifiable material, in particular an epoxy resin.

[0119] In all design variants, the layer thickness is preferably 0.1 to 0.5 times the maximum sphere diameter used.

[0120] In the aforementioned high-performance low-temperature Stirling engine M, with dimensions (H / W / D) of 25 cm x 25 cm x 25 cm, spheres of preferably 0.5 mm to 0.6 mm are used, wherein a heat exchanger R1, R2 has an inner diameter of approximately 30 mm and a length of approximately 100 mm to 150 mm. The heat exchanger R1, R2 is intended to be filled with the spheres.

[0121] It is preferably provided that, with reference to a maximum sphere packing with equally sized spheres (regardless of the sphere diameter), approximately 73% of the heat exchanger volume is occupied by the sphere volume and approximately 27% of the heat exchanger volume by the fluid volume of the working fluid AF.

[0122] With these parameters, each heat exchanger R1, R2 has a total sphere surface area of ​​approximately 1 m². 2 and thus, with a heat transfer from CO2 to the metallic spheres of 1000 J / m² 2 Each of the heat exchangers R1 and R2 has a thermal transfer capacity of approximately 1000 W / K. It has been found that this size achieves a good balance between the desired low flow resistance and the desired high thermal transfer capacity.

[0123] It is specifically provided that the heat exchanger has two connecting openings 11, 12 through which the working fluid FL flows into and out of adjacent working spaces, wherein at least one grid element 13, 14, in particular made of a stainless steel wire mesh, is arranged on the working space side or heat exchanger side, the mesh size of which is smaller than the diameter of the metallic or non-metallic spheres depending on the diameter of the metallic or non-metallic spheres.

[0124] In principle, therefore, as explained, both metallic and non-metallic materials are suitable for the spheres, as will be explained in more detail below.

[0125] Particularly inexpensive materials, such as glass, are also suitable despite their lower thermal conductivity.

[0126] Glass as a material can be used particularly when larger, high-performance, low-temperature Stirling engines with slower heat exchange sequences and thus lower rotational speeds are designed. A high-performance, low-temperature Stirling engine M with a heat exchanger R1, R2 in combination, filled with glass beads, can be manufactured more cost-effectively and, in particular, can be operated with higher efficiency and a lower temperature difference ΔT of the working fluid AF between the hot and cold sides.

[0127] Preferably, as explained, the surface of the metallic or non-metallic spheres is completely smooth, smooth and partially structured, or completely structured. The formation of a surface structure on the spheres increases heat transfer and thus the possible frequency of heat exchange sequences. The packing density of the spheres decreases slightly depending on the surface roughness of the surface structure; however, this effect is compensated for by the fact that the high-performance low-temperature Stirling engine M can be operated at a higher speed due to the increased heat transfer and the resulting higher frequency of heat exchange sequences.

[0128] As explained, it is further preferably provided that the spheres are embedded in an inner surface of the inner wall of the heat exchanger R1, R2, so that marginal flow channels in the heat exchanger R1, R2 are closed by the sphere embedding in the edge region of the heat exchanger R1, R2. This ensures that the working fluid FL cannot flow past the sphere bed between the inner wall of the heat exchanger and the sphere bed.

[0129] In a preferred embodiment of the invention, as explained, a thread is arranged on the inner surface of the heat exchanger in a first embodiment variant. The pitch of this thread—as the distance between two thread crests—corresponds to the diameter of the spheres, or, if the spheres have different diameters, to the largest diameter. This ensures that the spherical surface of the metallic or non-metallic spheres is at least partially embedded in the thread of the internal thread. With an ideal packing of the spheres, a tetrahedral, crystal-like structure is formed, which can largely follow the rising path of the thread. If, in this first embodiment variant, island-like defects occur which, similar to the thread in a spiral, connect both sides of the respective heat exchanger R1, R2, further embodiment variants are proposed.

[0130] In a preferred embodiment of the invention, as explained above, a layer of a shape-variable material with a predefinable layer thickness is arranged on the inner surface of the inner wall of the heat exchanger R1, R2. The spheres imprint their surface shape onto this layer, thereby closing the marginal flow channels in the heat exchanger R1, R2. Generally, the layer is made of a permanently elastic, plastic, thermally modifiable, or chemically modifiable material.

[0131] A spherical embedding in the edge region of the heat exchanger R1, R2 is proposed.

[0132] The inner wall of the respective heat exchanger R1, R2 is preferably coated with a thin layer with a layer thickness of approximately 0.1 to 0.5 times the ball diameter with a shape-variable layer.

[0133] The spheres at the edge of the heat exchanger R1, R2 imprint their own surface shape on this layer and close off edge flow channels.

[0134] The imprinting of the surface shape can be achieved in various ways: According to the invention, the layer is formed in various embodiments from a permanently elastic, a plastic, a thermally variable, or a chemically variable material.

[0135] In a second embodiment, the layer is made of a permanently elastic material, in particular rubber or soft plastic. During filling from above and / or below, the spheres are gently pressed against the inner wall, so that the spheres exert a coating-deforming force on the layer in the edge region of the heat exchanger. Upon disassembly, the original coating state is restored, and the filling process can be repeated as often as desired, with the adaptation potentially being induced again in a modified manner.

[0136] In a third embodiment, the layer is made of a plastic material, particularly tin. The spheres are filled into the layer using a coating-deforming force, as described in the second embodiment. The imprints of the sphere surfaces in the layer are now retained. During refilling, the layer is reshaped. The filling process can be repeated several times.

[0137] In a fourth embodiment, the layer is made of a thermally variable material, in particular a plastic or wax. In this embodiment, the spheres are filled without force. The respective heat exchanger R1, R2 is heated to such an extent that the coating softens and yields at specific points to the pressure of the spheres. A mechanically induced vibration of the heat exchanger R1, R2 supports the formation of the maximum packing density of the spheres within the respective heat exchanger R1, R2.

[0138] In a fifth embodiment, the layer is made of a chemically modifiable material, in particular an epoxy resin. The coating is adapted by a chemical reaction. The coating is applied using a viscous material that cures within a specific time, possibly with an increase in temperature. The filling process takes place during the curing time. The outer spheres are advantageously bonded to the inner wall of the respective heat exchanger R1, R2. In this embodiment, refilling the respective heat exchanger R1, R2 with the spheres is only possible after the outer spheres and the old coating have been removed.

[0139] The heat exchanger has at least one sealable filling element R1-1, R2-1 (see Fig.2) through which the working fluid FL and the spheres formed from metallic or non-metallic material can be poured into the interior of the heat exchanger.

[0140] To summarize once again some advantages of the high-performance low-temperature Stirling engine M and the heat exchanger R1, R2 according to the invention.

[0141] One advantage lies in the very high expansion coefficient of liquid carbon dioxide (CO2), even with small temperature changes. For example, liquid carbon dioxide exhibits an expansion coefficient of 258% per Kelvin in the range of 30.0°C to 30.06°C. This high expansion coefficient means that even small temperature changes can induce a volume change, resulting in high performance in the operation of the high-performance low-temperature Stirling engine M. Furthermore, the dynamic viscosity of liquid carbon dioxide (CO2) is extremely low in the described temperature ranges, enabling high flow velocities, particularly in heat exchangers R1 and R2.As a result, the high-performance low-temperature Stirling engine M can generate high power outputs even at temperatures below 50°C, outputs otherwise only achievable with significantly larger Stirling engines or those operating at much higher temperatures. The power range of the described high-performance low-temperature Stirling engine extends from a few watts to several megawatts, allowing for easy adjustment of the power output, for example, through the described cascading. The cascading system is thus a modular solution that enables adaptive adjustment of the described standard solution to specific local conditions thanks to its modular design.As explained, the high-performance low-temperature Stirling engine M utilizes even the smallest temperature differences between the hot side HS and the cold side KS at an overall low temperature level, thus increasing the range of usable heat sources. This makes it possible to use heat sources whose temperature level is generally insufficient to operate a heat engine. For example, both ambient heat and waste heat can be used without the need for prior heat concentration.

[0142] In particular, the small size of a high-performance low-temperature Stirling engine M with a power output of 2 kW ensures, in contrast to large and more difficult known Stirling engines, its use in any application where only a small installation space is available.

[0143] In the aforementioned embodiment (size of 25 cm x 25 cm x 25 cm), the cylinder pistons 3, 4 have a diameter of only approximately 80 mm. The diameter of the eccentric shafts 5, 6 is only approximately 30 mm, with the diameter of the eccentrics 5A, 6A, measured against the respective outer ring of the eccentric, being only approximately 61 mm.

[0144] Furthermore, the high-performance low-temperature Stirling engine M is very quiet and a closed system, preventing the fluids introduced during operation from escaping. Sealing the housing is advantageously achieved using elastomer seals, as system temperatures remain below 50°C. A high-performance low-temperature Stirling engine requires no starter or starter system, valves, spark plugs, or exhaust system. Moreover, only a few small components are needed, making a mass-produced high-performance low-temperature Stirling engine M inexpensive to manufacture.The high-performance low-temperature Stirling engine M according to the invention can be easily integrated into renewable energy supply systems, so that no conventional fuels are required in the entire system to achieve the desired rated power, which is usually only guaranteed with the use of conventional fuels.

[0145] The heat exchanger according to the invention also has, as explained, a small component size. The heat exchanger R1, R2 operates optimally at a small temperature difference ΔT between the hot side HS and the cold side KS, due to a relatively low flow velocity and relatively low flow resistance, since the surface area of ​​the storage mass is very large.

Claims

[1] Heat engine (M), comprising a high-performance low-temperature Stirling engine with a pressure chamber formed by at least one housing part (1A, 2A, 1A-2A), which is pressure-tight from the environment and filled with a working fluid (FL), and which delivers mechanical power on a hot side (HS) by external heat input at a higher temperature and on a cold side (KS) by external heat dissipation at a lower temperature than the higher temperature, wherein the at least one pressure chamber is divided into two fluid-tight and pressure-tight working chambers by periodically movable pistons (3, 4), wherein the working chambers are separated from each other on the fluid side by the pistons (3, 4) and are operatively connected on the pressure side via the pistons (3, 4), wherein one of the pistons (3, 4) on the hot side (HS) is heated by the external heat input relative to the other piston (3, 4) on the cold side (KS).4) is brought to a higher temperature or kept at a higher temperature, and the other piston (3, 4) arranged on the cold side (KS) is kept at a lower temperature or brought to a lower temperature relative to the piston (3, 4) arranged on the hot side (HS), wherein the pressure fluctuations generated in the working chambers periodically act on the movable pistons (3, 4) which are operatively connected to eccentric shafts (5, 6) having eccentrics (5A, 6A), wherein the eccentric shafts (5, 6) are arranged parallel to each other with respect to their longitudinal axes (5B, 6B), , characterized by, that an eccentric center (5C, 6C) of the eccentric (5A, 6A) of one eccentric shaft (5, 6) forms a predetermined angular offset (V) relative to the other eccentric shaft (5, 6), wherein the angular offset (V) is formed between the eccentric centers (5C, 6C) of the eccentrics (5A, 6A) and the centers of the longitudinal axes (5B, 6B) of one eccentric shaft (5, 6) relative to the other. [2] Heat engine (M) according to claim 1, characterized by , that each of the pistons (3, 4) has parallel opposing piston end faces (A3, A4), wherein two piston end faces (A3, A4) on the same side of the pistons (3, 4) form an energy storage space between the piston end faces between the hot side (HS) and the cold side (KS). [3] Heat engine (M) according to claim 1, characterized by that the energy storage spaces are designed as thermal regenerators (R1, R2). [4] Heat engine (M) according to claim 1 and 3, characterized by that the thermal regenerators (R1, R2) designed as energy storage spaces are integrated into the housing (1A, 2A, 1A-2A) or are arranged outside the housing (1A, 2A, 1A-2A). [5] Heat engine (M) according to claim 2, characterized by , that the movable pistons (3, 4) are arranged in cylinders (1, 2) which are connected on the pressure side via connecting openings (11, 12) to the energy storage spaces designed as thermal regenerators (R1, R2). [6] Heat engine (M) according to claim 1 or 2, characterized by, that the one-piece or multi-piece cylinders (1, 2) each form a piston interior (3A, 4A) in which an eccentric (5A, 6A) of the eccentric shafts (5, 6) is arranged, wherein the piston interiors (3A, 4A) are designed to be pressure-tight and fluid-tight relative to the working chambers, wherein the forces (F) acting on the piston end faces (A3, A4) of the respective piston (3, 4) lead to the periodic movement of the piston (3, 4) and the respective piston (3, 4) acts on the eccentric shafts (5, 6) depending on the position of the eccentric (5A, 6A). [7] Heat engine (M) according to claim 1 and 4, characterized by , that the eccentric shafts (5, 6) are mounted in the housing (1A, 2A, 1A-2A) via bearings (5D, 6D) adjacent to the piston interior (3A, 4A) in the longitudinal direction with respect to their longitudinal axes (5B, 6B) parallel to each other, wherein the eccentric shafts (5, 6) are led out of the piston interior (3A, 4A) at least on one end. [8] Heat engine (M) according to claim 1, characterized by , that the specified angular offset (V) is between 90° and 170°. [9] Heat engine (M) according to claim 1 and 8, characterized by , that the specified angular offset (V) is fixed by gears (9, 10) arranged on the eccentric shafts (5, 6) outside the housing (1A, 2A, 1A-2A), which are meshed together according to the specified angular offset (V). [10] Heat engine (M) according to claim 6, characterized by , that in the respective piston interior (3A, 4A) between the eccentric (5A, 6A) of the eccentric shafts (5, 6) and the inner surfaces of the pistons (3, 4) a sliding bearing bushing (7, 8) is arranged. [11] Heat engine (M) according to claim 6, characterized by , that the forces (F) acting on the respective pistons (3, 4) are aligned with respect to the longitudinal axes (5B, 6B) of the eccentric shafts (5, 6) and act orthogonally as transverse forces on the eccentric shafts (5, 6). [12] Heat engine (M) according to claim 1, characterized by that the working fluid (FL) in the pressure chamber is liquid supercritical carbon dioxide or xenon or ethene. [13] Heat engine according to claim 1, characterized by , that the working fluid (FL) is carbon dioxide, which is used in the working spaces and energy storage spaces of the pressure chamber at an operating point that has a temperature of 30°C at a pressure of 7.2 MPa (72 bar). [14] Heat engine (M) according to claims 1 and 12, characterized by, that carbon dioxide as working fluid (FL) in the working spaces of the pressure chamber and the energy storage chambers fluctuates between 7.0 MPa (70 bar) and 7.5 MPa (75 bar) depending on the temperature at a temperature difference (ΔT) between 2K and 10K between the hot side (HS) and the cold side (KS) of the pistons (3, 4), wherein the pressure fluctuations are caused by the temperature difference (ΔT) between the hot and cold sides (HS, KS) at a temperature on the hot side (HS) of a maximum of 37°C and a temperature on the cold side (KS) of a minimum of 27°C. [15] Heat engine (M) according to at least one of claims 1 to 13, characterized by, that several heat engines (Mn) are arranged separately from one another as a cascade in the longitudinal direction of the eccentric shafts (5, 6), wherein the pressure fluctuations generated in several working chambers act periodically on the several movable pistons (3, 4) which are in operative connection with the eccentric shafts (5, 6), wherein the parallel eccentric shafts (5, 6) are arranged eccentrically to one another in the longitudinal direction of the eccentric shafts (5, 6) at a predetermined angular offset (V), wherein the predetermined angular offset (V) in several cascading heat engines (Mn) is shifted symmetrically from heat engine (Mn) to heat engine (Mn) by 360° / n depending on the number (n) of the heat engines (Mn) forming the cascade.

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