Method and improved device for converting thermal energy into kinetic energy

Abstract

The invention relates to a method for converting thermal energy, in particular energy from the environment, into kinetic energy and to a device for converting thermal energy into kinetic energy, said device being used to carry out the method. In the method according to the invention, two circuits with fluids are operatively connected together in that on at least three heat exchangers, one fluid influences the others. The two circuits are additionally provided with environmental heat exchangers which preset the temperature of the fluids being used. The exhaust heat used for this purpose can originate from the industrial sector for example.

Description

[0001] Method and improved device for converting thermal energy into kinetic energy

[0002] Description

[0003] The present invention relates to a method for converting thermal energy, in particular energy from the environment, into kinetic energy and to a device for converting thermal energy into kinetic energy with which the method can be carried out.

[0004] State of the art

[0005] Providing the population with energy is a key issue. In particular, the generation of "clean" energy is politically desirable to protect the environment and slow, if not halt, climate change. Well-known environmentally friendly energy generation facilities include hydroelectric power plants, solar collectors, which are also used industrially in solar parks, and wind turbines, which convert wind into energy onshore and, increasingly, in large-scale facilities located offshore. These technologies will not be sufficient to halt climate change in the long term. Furthermore, electricity consumption due to electromobility is continuously increasing.

[0006] DE 10 2019 006 184 A1 therefore presents a device for converting thermal energy into kinetic energy through the combined use of a heat pump and a thermal power plant. The device is based on two thermodynamic cycles. The two cycles are connected to each other in the machine by two heat exchangers for the purpose of heat transfer. This utilizes the property of heat pumps to absorb thermal energy with gases at heat exchangers and, through compression, to achieve high temperatures while simultaneously increasing the gas pressure and reducing the volume. The amount of energy required to operate the pump is significantly smaller than the amount of energy pumped. The heated fluid is then used to evaporate a second fluid, so that the gas pressure can be converted into kinetic energy in a heat engine.Since the fluid must be condensed, as in any conventional power plant, the unused residual steam is fed into the condenser, where it is cooled by the very cold fluid from the heat pump circuit, which has been expanded by an expansion valve. There, the fluid from the heat engine circuit condenses and is pumped back into the heat exchanger for repeated evaporation. The heat pump fluid is then heated again in the heat exchanger and, with the thermal energy it contains from the condenser and the environment, can be drawn back into the compressor and then back into the heat exchanger, where heat is transferred to the fluid from the heat engine circuit. This enables a constant conversion of thermal energy into kinetic energy. Since heat pumps can be used for both cooling and heating, the energy conversion machine utilizes both potentials to utilize fluids with boiling points below 273 degrees Kelvin.Since the condenser used can reach temperatures below 250 degrees Kelvin, temperature differences of 100 degrees Kelvin and more are possible. Fluids such as isobutane can therefore build up high pressure, which is used in combined heat and power engines to convert it into kinetic energy until the gas flows to the condenser at minimal pressure and a very low temperature. When using ammonia, for example, the condenser can reach temperatures below 250 degrees Kelvin and condense gases such as isobutane. This means that the temperature gradient and thus the pressure difference across the heat engine is sufficient to convert the majority of the energy absorbed in the heat exchanger into kinetic energy. Condensation turbines, a special type of heat engine, can also further increase efficiency by utilizing the enthalpy of vaporization.During tests conducted for this development, the developer realized that the efficiencies were not yet sufficient for effective use on an industrial scale. The invention is based on the object of providing an expanded method and an improved device for converting thermal energy into kinetic energy.

[0007] The problem is solved with the features of method claim 1 and device claim 3, wherein the respective subclaims describe further embodiments.

[0008] Definitions

[0009] An environmental heat exchanger in the sense of the invention is a device in which energy is taken from the environment in the form of heat, e.g. waste heat from industrial processes, thermal energy from power plants intended for the device, from water or steam or ultimately directly from the environment, provided that this thermal energy source is sufficient to provide the required level within the device.

[0010] If a fluid is heated, a part of the fluid can also evaporate at the same time without this needing to be described in more detail.

[0011] If a fluid releases heat, liquefaction can also occur at the same time without this needing to be described in more detail.

[0012] Description of the invention

[0013] First, some basic principles for understanding the process and device will be laid. Heat pumps are generally based on efficiencies, not coefficients of performance. The work performed, and thus the pump's efficiency, is calculated from the pump's power consumption, the pump stroke, and the amount of water pumped. The temperature of the water, and thus the pumped heat capacity, are irrelevant. With a suitable arrangement—i.e., a significant difference between the ambient temperature and the temperature of the pumped medium—enormous amounts of heat, large quantities of energy, can be transported with constant pumping effort. This heat must be harnessed. The coefficient of performance of a heat pump—unlike its efficiency—thus clearly indicates the amount of energy contained in the pumped fluid.

[0014] In a conventional refrigeration system, the coefficient of performance is three to four times the energy consumed by its compressor. With a pumping power of 1 kW, a cooling capacity of up to 4 kW could be expected. The generated cold is used, for example, in a refrigerator to extract heat from the heat energy source of food, thus extending its shelf life.

[0015] Since a heat pump follows the first law of thermodynamics, the amount of energy corresponding to the cooling capacity must be dissipated as heat. The heat dissipated therefore corresponds to the required cooling capacity used to lower the temperature inside the refrigerator to the required cooling level. In the case of a state-of-the-art refrigerator, this heat dissipated into the surrounding space dissipates without further use. With a cooling capacity of 4 kW per 1 kW of pumping power, the amount of heat to be dissipated on the outside of the refrigerator is also 4 kW from the interior, plus an additional 1 kW of waste heat from the compressor.

[0016] A heat engine in the form of an ORC steam turbine converts temperature differences into rotational energy to a high degree by expanding gases – usually in the range of 70% or more. The remainder is transferred to a condenser as heat in the partially condensed fluid. For the device to function, the heat engine requires a heating and a cooling side. If the heat sink of a heat pump is designed as a condenser and the heating side of the heat pump is designed as an evaporator, with a suitable choice of fluid and the heat absorption from the environment, the components of the heat pump can be configured as the heating or cooling side of the heat engine in such a way that a high degree of rotational energy is converted into electrical energy. The amount of heat released by the heat engine is so high that it significantly exceeds the required pumping energy or energy for the compressor.

[0017] To increase the performance figures, it is advisable to extend the circuits of the heat pump and the heat engine by a suitable number of additional heat exchangers, since, as explained above, the performance increases with the size of the temperature difference.

[0018] Against this background, the inventive method for converting thermal energy into kinetic energy is presented. In this method, the recurring process steps run in parallel in a first and a second circuit. The circuits are subject to a mutual interdependence in which a condenser in one circuit is an evaporator in the other circuit, and vice versa. As the fluid in one circuit moves through the circuit, its temperature is repeatedly influenced by the fluid in the other circuit.

[0019] In a first circuit, an initially gaseous fluid is compressed, resulting in an increase in temperature. The compression creates a pumping motion of the fluid through the circuit. This first fluid is cooled in a first heat exchanger with condensation, further cooled in a third heat exchanger, also with condensation, and decompressed in a decompression valve. It then passes through a second heat exchanger and absorbs heat before absorbing further heat in an environmental heat exchanger before being returned to the compression process described above.

[0020] A second fluid is pumped through the second circuit and heated in a third heat exchanger, while the first fluid is cooled as described above. Evaporation occurs in a second environmental heat exchanger and further heating occurs in a first heat exchanger. This further heating is accompanied by the first cooling of the first fluid. From the first heat exchanger, the second fluid enters a heat engine, where the pressure is reduced and the temperature is released. The resulting rotational energy can be taken up at the heat engine and converted into electrical energy, for example. After being expanded by the heat engine, the fluid is returned to the second heat exchanger and liquefied before the process begins again with the pumping process towards the third heat exchanger.

[0021] The result of this process, with two overlapping and mutually influencing circuits, is the achievement of an optimal aggregate state of the respective fluid, especially the second fluid, since this fluid should be introduced into the heat engine at the highest possible temperature and returned to the circuit at the lowest possible temperature. If the temperature difference between the heat engine inlet and outlet is particularly high, high kinetic energy can be generated.

[0022] By compressing the initially gaseous first fluid, a temperature level is reached at which heat is transferred to the second fluid in the first heat exchanger, so that the second fluid reaches the desired inlet temperature at the heat engine. The first fluid flows cooled down and is cooled again in a third heat exchanger, where the heat is transferred to the second fluid. In the process, it condenses and is expanded by the decompression valve.

[0023] This makes it ready to absorb heat again, first in a second heat exchanger and later in the environmental heat exchanger.

[0024] To optimally implement such a process, fluids are preferably used that function effectively under the prevailing climatic conditions and the resulting temperature differences to the heat sources. Propane, carbon dioxide, and ammonia can be cited as examples, but other fluids are not excluded. Of these, propane is very suitable because it is relatively easy to control and thus allows for greater safety in use. Furthermore, it is not converted into TFA and is therefore not persistent when released into the environment. According to a special embodiment of the inventive process for converting thermal energy into kinetic energy, no further condensation takes place in the third heat exchanger. For the process to run optimally, this condensation should already be completely completed in the first heat exchanger.Ideally, the first fluid exiting the first heat exchanger is at ambient temperature. This increases the effectiveness of the process.

[0025] According to a further embodiment of the inventive method for converting thermal energy into kinetic energy, the second fluid is completely evaporated in the second environmental heat exchanger. This process improvement also leads to increased efficiency.

[0026] Furthermore, a special embodiment of the process for converting thermal energy into kinetic energy provides for temperature and / or flow rate and / or pressure measurements to be taken at at least one point in each circuit. This allows for better monitoring of the process, while regularly collected data can provide insight into the process and warn users if necessary. These measurements serve the purpose of increasing efficiency but also serve safety reasons. Furthermore, they enable control via valves that optimize energy flow and heat transfer and enable safety options. For example, excessive or insufficient heat inputs can be corrected before the system overheats or underheats, or before the heat engine becomes overloaded or underloaded.

[0027] Finally, a further embodiment of the method according to the invention for converting thermal energy into kinetic energy includes the waste heat generated at the pump in the second circuit being fed back into the second circuit, between the second environmental exchanger and the first heat exchanger or between the first heat exchanger and the heat engine. This allows even waste heat generated during the process to be put to further use, thereby increasing efficiency. Similarly, heat generated by other heat-emitting components of the circuit can also be removed and fed back into the circuit at a suitable point.

[0028] The improved device for converting thermal energy into kinetic energy for use in the described method comprises two fluid circuits, wherein a first circuit comprises, in sequence, a first environmental heat exchanger, a compressor, a first heat exchanger, a decompression valve, and a second heat exchanger. In the first circuit, the first heat exchanger serves as a condenser, and the second heat exchanger as an evaporator. A second circuit comprises, in sequence, the first heat exchanger, a heat engine, the second heat exchanger, and a pump, wherein in the second circuit, the first heat exchanger serves as an evaporator and the second heat exchanger serves as a condenser. Both circuits are not fluidically connected to one another, but have operative relationships at the first and second heat exchangers.

[0029] According to the invention, a third heat exchanger is arranged in the first circuit downstream of the first heat exchanger, and the third heat exchanger and a second environmental heat exchanger are arranged in the second circuit downstream of the pump. The circuits in the third heat exchanger also have a functional relationship between the first and second circuits. By additionally incorporating a third heat exchanger and a second environmental heat exchanger, the effectiveness of the device is further increased compared to the device described in the prior art. The fluids in the circuit can be adjusted even more precisely to the required temperatures and aggregate states, so that an optimal result can be achieved in the heat engine.

[0030] According to a particular embodiment of the improved device for converting thermal energy into kinetic energy, the device comprises measuring sensors for temperature and / or flow rate and / or pressure, and a control unit for processing the measured data. For safety reasons, but especially to achieve optimal efficiency figures, it is essential that measured data such as pressure, temperature, flow rate, or similar parameters are recorded and evaluated, and that necessary adjustments such as increasing the pressure in the fluid, changing the supply of heat from the environment, etc. are made. Constant monitoring of these parameters is also necessary to ensure consistent efficiency of the heat engine.

[0031] According to a special embodiment of the improved device for converting thermal energy into kinetic energy, the environmental heat exchangers are integrated into circuits. This essentially transforms the environmental heat exchanger into a conventional heat exchanger, where the temperature generated elsewhere is taken and transferred to the fluid. This expands the possible applications and allows the device to be adapted to the conditions at the site of use.

[0032] According to a special design of the improved device for converting thermal energy into kinetic energy, the pump in the second circuit is designed as a compressor. This additional function of the pump increases the influence on the fluid, as it can be adapted even more precisely to the specifications required for high efficiency of the heat engine.

[0033] Finally, according to a special embodiment of the improved device for converting thermal energy into kinetic energy, the first heat exchanger and the third heat exchanger and / or the second environmental heat exchanger are connected in a heat exchange arrangement. This allows the device to be designed significantly more compactly without sacrificing effectiveness. It can thus be used in smaller quantities. Furthermore, it is of course possible for other components to be combined separately or together with the aforementioned components in more compact units, if this is possible, for example, for reasons of better energy utilization in the system.

[0034] According to a final embodiment of the improved device for converting thermal energy into kinetic energy, both circuits are equipped with bypass lines in the area of ​​the environmental heat exchangers. This allows the system to be specifically protected from absorbing further energy at the environmental heat exchangers when the fluids are redirected through the bypass lines, thus allowing it to be cooled down. These bypass lines also protect the system from overheating, thus preventing damage or accidents.

[0035] A major advantage of the device is that waste heat of any kind, e.g., from laundries, energy generation, waste incineration, landfill degassing, and other industrial processes, as well as natural waste heat such as from hot springs, can be transferred to the device via the first and second environmental heat exchangers. This does not necessarily have to be done directly, but can also be achieved via an upstream heat cycle. This allows for very flexible use in many different locations, preferably where waste heat of any kind would otherwise be lost unused.

[0036] Many different fluids can be considered. Carbon dioxide, ammonia, and especially propane are preferred due to their good usability under Earth's prevailing conditions. These substances are comparatively easy to obtain and handle. It is possible to use different fluids for the circuits, provided this does not affect the effectiveness of the device.

[0037] A power supply must be provided for all measuring and control devices, as well as the control unit. The pumps must also be electrically operated. Energy is also introduced into the system at the environmental heat exchangers, which can absorb waste heat from industrial sources, for example.

[0038] The explanations are summarized below in a different logical structure in order to present the inventive causal relationships and the resulting results up to the energy conversion in a different way.

[0039] The process for converting thermal energy into kinetic energy comprises repeatedly recurring process steps in a first circuit. These include the absorption of thermal energy from the environment or from external processes by evaporation of a first fluid in a first environmental heat exchanger and the compression of the gaseous first fluid with an associated temperature increase by a compressor, whereby the compression generates a pumping movement of the fluid through the first circuit. Furthermore, in this circuit, thermal energy from the first fluid is released in a first heat exchanger with associated condensation and a further release of thermal energy from the first fluid in a third heat exchanger with associated further condensation. The first fluid is then decompressed by a decompression valve and thermal energy is again absorbed and the first fluid evaporates in a second heat exchanger.

[0040] At the same time, recurring process steps take place in a second circuit. These include the release of heat energy with accompanying condensation of a second fluid in the second heat exchanger, pumping the second fluid through the second circuit by means of a pump, and absorption of heat energy with accompanying evaporation of the second fluid in the third heat exchanger, whereby an increase in the vapor pressure in the second circuit is generated. Subsequently, further heat energy is absorbed from the environment or from external processes with accompanying further evaporation of the second fluid in a second environmental heat exchanger, whereby a further increase in the vapor pressure in the second circuit is achieved. Further absorption of heat energy with accompanying further evaporation of the second fluid in the first heat exchanger takes place, whereby a further increase in the vapor pressure in the second circuit is achieved.The second fluid, which is then in gaseous form, is then fed into a heat engine, in which a conversion of vapor pressure and thermal energy into kinetic energy takes place, combined with a decrease in kinetic energy at the heat engine, whereby vapor pressure and thermal energy decrease.

[0041] The two circuits are subject to a mutual relationship, in which a condenser in one circuit is an evaporator in the other circuit, and vice versa. Implementation of the invention

[0042] The invention is explained using an exemplary embodiment. Figure 1 shows a schematic overview of the device according to the invention.

[0043] Two circuits 2, 3 are shown which touch each other multiple times. Wherever circuits 2, 3 touch, there is a heat exchanger 6, 8, 11. Here the fluids moving through circuits 2, 3 influence each other. To achieve flow in the first circuit, one compressor 5 is sufficient. Here the fluid in the first circuit 2 is compressed and its temperature is increased. There is a temperature release in the first heat exchanger 6, a further temperature release in the third heat exchanger 11 and decompression in the decompression valve 7. The fluid then absorbs heat first in the second heat exchanger 8 and then in the first environmental heat exchanger 4. The highest temperature of the fluid is therefore after compression, the lowest after decompression.

[0044] In the second circuit 3, a fluid is pumped by a pump toward the third heat exchanger 11, where it is heated. The fluid is further heated in the second environmental heat exchanger 12, its temperature rises again in the first heat exchanger 6, and is then transferred to the heat engine 9. This heat generates kinetic energy, cooling the fluid. The fluid is then liquefied again in the second heat exchanger 8 before being pumped back into the second circuit 3.

[0045] List of reference symbols

[0046] 1 device

[0047] 2 First circuit

[0048] 3 Second circuit

[0049] 4 First environmental heat exchanger

[0050] 5 compressors

[0051] 6 First heat exchanger

[0052] 7 Decompression valve

[0053] 8 Second heat exchanger

[0054] 9 Heat engine

[0055] 10 Pump

[0056] 11 Third heat exchanger

[0057] 12 Second environmental heat exchanger

Claims

Claims 1. A process for converting heat energy into kinetic energy comprising the recurring process steps in a first cycle (2) - Compression of a gaseous first fluid with a concomitant temperature increase, wherein the compression generates a pumping motion of the fluid through the first circuit (2), - Cooling of the first fluid in a first heat exchanger (6) with condensation, - further cooling of the first fluid in a third heat exchanger (11) with further condensation, - Decompression of the first fluid in a decompression valve (7), - Heat absorption in a second heat exchanger (8) and - further absorption of temperature in a first environmental heat exchanger (4), as well as the parallel, recurring process steps in a second circuit (3) - Pumping a second fluid through the second circuit (3), - Heating in a third heat exchanger (11), - Evaporation in a second environmental heat exchanger (12), - further heating in a first heat exchanger (6), - Transferring the second fluid into a heat engine (9) with accompanying pressure reduction and temperature release, - Reduction of energy at the heat engine (9) and - Return to the second heat exchanger (8) and condensation, wherein the circuits (2, 3) are mutually dependent, in which a condenser of one circuit is an evaporator of the other circuit.

2. Method for converting heat energy into kinetic energy according to claim 1, characterized in that no further condensation takes place in the third heat exchanger (11). A method for converting thermal energy into kinetic energy according to any of the preceding claims, characterized in that the second fluid is already evaporated in the second environmental heat exchanger (12). A method for converting thermal energy into kinetic energy according to any of the preceding claims, characterized in that temperature and / or flow velocity and / or pressure measurements are taken at least at one point in each circuit (2, 3), the recorded data are evaluated, and the respective circuit is optimized by means of controllers. A method for converting thermal energy into kinetic energy according to any of the preceding claims, characterized in that waste heat generated at the pump (10) in the second circuit (3) is supplied to the second circuit (3) between the second environmental heat exchanger (12) and the first heat exchanger (6) or between the first heat exchanger (6) and the heat engine (9).Improved device (1) for converting thermal energy into kinetic energy for use in the method according to claims 1 to 5, comprising two circuits (2, 3) for fluids, wherein a first circuit. (2) in the following order a first environmental heat exchanger (4), a compressor (5), a first heat exchanger (6), a decompression valve (7) and a second heat exchanger (8), wherein in the first circuit (2) the first heat exchanger (6) serves as a condenser and the second heat exchanger (8) serves as an evaporator, and a second circuit (3) comprising in sequence the first heat exchanger (6), a heat engine (9), the second heat exchanger (8) and a pump (10), wherein in the second circuit (3) the first heat exchanger (6) serves as an evaporator and the second heat exchanger (8) serves as a condenser, wherein the two circuits (2, 3) are not fluidically connected, except at the first heat exchanger (6) and at the second heat exchanger (8) exhibit interrelationships, characterized in that in the first circuit (2) after the first heat exchanger (6) there is a third heat exchanger (11) and in the second circuit (3) after the pump (10) there is the third heat exchanger (11) and a second environmental heat exchanger (12) are arranged, wherein the circuits (2, 3) in the third heat exchanger (11) have an interaction between the first circuit (2) and the second circuit (3). Improved device (1) for converting thermal energy into kinetic energy according to claim 6, characterized in that the device has measuring sensors for temperature and / or flow velocity and / or pressure and a control unit for processing measurement data as well as controllers for controlling the process. Improved device (1) for converting thermal energy into kinetic energy according to claims 6 or 7, characterized in that the environmental heat exchangers (4, 12) are integrated into external circuits. Improved device (1) for converting thermal energy into kinetic energy according to claims 6 to 8, characterized in that the pump (10) in the second circuit (3) is designed as a compressor.Improved device (1) for converting thermal energy into kinetic energy according to claims 6 to 9, characterized in that the first heat exchanger (6) and / or the third heat exchanger (11) and / or the second environmental heat exchanger (12) are connected in a heat exchanger arrangement. Improved device (1) for converting thermal energy into kinetic energy according to claims 6 to 10, characterized in that the circuits (2, 3) have bypass lines to bypass the environmental heat exchangers (4, 12).

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