Compressor for compressing a fluid

Abstract

The invention presented relates to a compressor (100) for compressing a fluid, wherein the compressor (100) comprises: - a compressor room (101), - a collection container (103) for a liquid, - a pump (105), wherein the pump (105) is configured to pump liquid from the collection tank (103) into the compressor chamber (101) in order to compress fluid located in the compressor chamber (101), wherein a porous insert (109) is arranged in the compressor chamber (101), the density of which changes as it passes through the compressor chamber (101).

Description

[0001] The presented invention relates to a compressor for compressing a fluid, an energy supply system for supplying a consumer with energy, a fluid supply system for supplying a storage device with a fluid, and a method for compressing a fluid, according to the attached claims. State of the art

[0002] The compression of fluids, especially gases, will increase significantly as part of the energy transition. Hydrogen gas cannot be liquefied at temperatures above -239.9°C and pressures below 13.15 bar (critical point). This means that in the vast majority of real-world applications, hydrogen will exist as a gas.

[0003] Energy-efficient compressors are therefore needed for the transport and storage of hydrogen.

[0004] Since hydrogen has a very low volumetric density, very high pressures are required, for example 700 bar in passenger cars. Furthermore, energy-efficient compressors are needed, especially for compressing hydrogen produced by electrolysis systems and for storing carbon dioxide in final repositories.

[0005] Gas compressors are well known and established on the market in various forms, e.g. as Roots blowers, reciprocating compressors, turbo compressors or similar.

[0006] All known compressors have in common that the compression process is almost adiabatic / isentropic. This means that the gas or fluid heats up considerably during compression, but cannot be cooled, or only very insufficiently, in the compression chamber.

[0007] This is because the known compressors usually require high-speed processes in which the heat cannot be dissipated from a compressor chamber to a significant extent, as the surface area to volume ratio is too poor.

[0008] It is also well known that heated gas requires more energy to be compressed than cold gas.

[0009] Ideally, a gas should be compressed isothermally, as this requires the lowest possible energy expenditure.

[0010] Below is an example calculation to highlight the significance: 1 Nm 3 H2 contains 2.9 kWh of chemical energy. An ideal (isothermal) compression to 600 bar requires approximately 200 Wh / Nm³. 3 H2. This corresponds to approximately 7% of the contained chemical energy. In reality, at least 500 Wh / Nm³ is used today. 3 H2 is necessary, i.e., approximately 17% of the energy content.

[0011] If one further considers that a compressor requires electrical energy, and this energy must first be generated from hydrogen using a fuel cell, the efficiency is halved again. This means that approximately one-third of the chemically stored energy in the hydrogen is currently needed to compress the hydrogen to 600 bar.

[0012] This example applies to single-stage compression. To minimize losses, multi-stage compressors with gas intercooling are used. However, this makes the compressors more complex and expensive. Disclosure of the invention

[0013] Within the scope of the presented invention, a compressor for compressing a fluid, an energy supply system for supplying a consumer with energy, a fluid supply system for supplying a storage device with a fluid, and a method for compressing a fluid are presented.

[0014] Further features and details of the invention will become apparent from the respective dependent claims, the description, and the drawings. Features and details described in connection with the compressor according to the invention naturally also apply in connection with the fluid supply system or the energy supply system and the method according to the invention, and vice versa, so that the disclosure regarding the individual aspects of the invention always makes or can make reciprocal reference.

[0015] The invention presented here serves in particular to provide a possibility for an energy-efficient compressor for compressing a fluid, especially hydrogen.

[0016] Thus, according to a first aspect of the presented invention, a compressor for compressing a fluid is presented.

[0017] The presented compressor comprises a compressor chamber, a collection tank for a liquid and a pump, wherein the pump is configured to pump liquid from the collection tank into the compressor chamber in order to compress fluid located in the compressor chamber, wherein a porous insert is arranged in the compressor chamber, the density of which changes as it passes through the compressor chamber.

[0018] In the context of the presented invention, density refers in particular to gravimetric density.

[0019] In the context of the presented invention, a porous insert is understood to be a material or a mixture of materials that forms a multitude of pores or cavities. A porous insert can be, for example, a metal foam or a quantity of bulk material, such as metal spheres, in particular steel spheres, and / or ceramic elements.

[0020] The present invention is based on the principle that the fluid to be compressed is not compressed by reducing the volume of the compressor chamber using a mechanical solid, e.g., a piston, but rather by filling the compressor chamber with a liquid to compress the fluid already present there. As the liquid volume increases, it reduces the space available for the fluid within the compressor chamber, sealing it completely. Consequently, sealants and lubricants are unnecessary, preventing contamination of the fluid by residues of such substances.

[0021] Due to the use of liquid for compression, the presented compressor requires particularly little maintenance.

[0022] According to the invention, a porous insert is arranged in the compressor chamber, the density of which changes as it flows through the compressor chamber. The liquid flowing into the compressor chamber thus fills each pore of the porous insert and displaces the fluid contained therein.

[0023] When the liquid is drained from the compressor chamber, the liquid flows out of the porous insert and the pores refill with newly flowing fluid.

[0024] The porous insert has a high heat capacity and a very large surface area.

[0025] The heat energy generated during compression is absorbed via the very large surface area of ​​the porous insert due to its heat capacity, especially if it contains metallic and / or ceramic components, so that the fluid does not heat up or only heats up by a few Kelvin.

[0026] The porous insert is cooled down by the inflowing, possibly cooled, liquid, and the unwanted heat energy is carried away when the liquid is drained from the compressor chamber.

[0027] During compression, the fluid first transfers the resulting heat energy to the porous insert, and the porous insert then passes the heat energy on to the liquid as soon as its pores fill with liquid.

[0028] The porous insert is designed with respect to its mass such that its absolute heat capacity, given material constants, is so large that the fluid heats up by a predetermined amount at most.

[0029] In the presented compressor, the fluid is not cooled after compression, as in multi-stage compressors, but during compression within the compressor chamber. This results in compression very close to ideal, isothermal compression.

[0030] Compression using fluid solves the problem of lubrication as well as backflow at high pressures, since the fluid seals absolutely tightly.

[0031] The density of the porous insert is designed to change as it flows through the compressor chamber. For example, the density can be higher in the upper section, where the fluid enters the compressor chamber, than in the lower section, where the fluid exits. This distribution of density in the porous insert ensures particularly good heat transfer from the fluid to the insert, while simultaneously optimizing the material properties of the insert.

[0032] It may also be provided that the density of the porous insert changes uniformly or randomly during the course of the porous insert through the compressor chamber.

[0033] In particular, the density can change if the porous insert consists of bulk material, due to the use of bulk material elements of different sizes and / or weights, such as metal spheres. Specifically, the density of the porous insert can change gradually or uniformly as it moves through the compaction chamber.

[0034] Alternatively or in addition to bulk material elements of different sizes and / or weights, differently shaped bulk material elements can be used, resulting in a randomly distributed pore structure.

[0035] Accordingly, the pore size of the porous insert, i.e., the size of the pores formed between the bulk material elements, can change as it moves through the compaction chamber.

[0036] The presented compressor enables, in particular, single-stage compression, the performance of which depends only on the performance of the pump.

[0037] It can be provided that the pump is a reciprocating piston pump configured to compress a quantity of fluid located in the collection container with a single stroke such that it is present at a pressure greater than 20 bar, in particular greater than 90 bar, preferably greater than 600 bar.

[0038] A reciprocating pump configured to compress a quantity of fluid in the collection container with a single stroke to a pressure greater than 20 bar, in particular greater than 90 bar, preferably greater than 600 bar, may, for example, include a particularly heavy counterweight, which, for example, weighs more than one ton.

[0039] A reciprocating pump of this type can compress a large quantity of fluid to a very high, predetermined pressure extremely quickly. This is relevant, for example, for hydrogen filling stations where hydrogen gas must be supplied at a pressure of approximately 100 bar. Since the hydrogen is stored at low pressure, it must be compressed for each refueling process, which is time-consuming. The compressor presented here, with its corresponding reciprocating pump, can compress the entire volume of hydrogen needed to fill a vehicle to the required pressure in a single stroke, thus enabling the rapid refueling of numerous vehicles.

[0040] In particular, the pump of the presented compressor can be configured in such a way that with just one stroke a fluid located in the compressor chamber of the compressor is compressed to such an extent that it is present at a predetermined pressure and can be further processed accordingly, e.g. stored in a storage tank.

[0041] It may also be provided that the porous insert has a porosity between 60% and 95% and is permeable to the fluid to be compressed as well as the liquid.

[0042] The porosity of the metal foam can vary along the porous insert. For example, the porosity of the insert can be higher in the upper section, where the fluid enters the compressor chamber, than in the lower section, where the fluid exits the compressor chamber. This distribution of porosity ensures particularly good heat transfer from the fluid to the metal foam while simultaneously optimizing the material properties of the porous insert.

[0043] It may also be provided that the compressor includes a cooling device configured to cool the liquid to a temperature below the temperature of the fluid.

[0044] By cooling the liquid to a temperature below that of the fluid, a thermal buffer is provided to absorb thermal energy released during compression of the fluid, thus minimizing heating of the compressor.

[0045] It may also be stipulated that the liquid is an ionic liquid or water.

[0046] Suitable liquids for use in the presented compressor are ionic liquids, which are characterized by their lack of vapor pressure, thus preventing contamination of the fluid. If small amounts of water vapor in the fluid are tolerated, liquid water can be used in the compressor, for example, in the compression of carbon dioxide into gas storage tanks.

[0047] It may also be provided that the compressor is configured to compress a fluid from the following list of fluids: hydrogen, carbon dioxide, refrigerant.

[0048] Due to its energy efficiency, fast operation and low maintenance requirements, the presented compressor is suitable for many applications, such as compressing hydrogen provided by an electrolysis system, compressing refrigerant in an energy supply system, such as a heat pump or air conditioner, especially a cooling unit, or operating a carbon dioxide storage system.

[0049] It may be provided that the compressor further includes a first valve for controlling an inflow of liquid from the collection tank into the compressor chamber, a second valve for controlling an outflow of liquid from the compressor chamber into the collection tank, a third valve for controlling an inflow of fluid into the compressor chamber and a fourth valve for controlling an outflow of fluid from the compressor chamber.

[0050] Four valves, which are opened and closed independently of each other or at different times, enable a timed compression of fluid in a continuous process.

[0051] According to a second aspect, the presented invention relates to an energy supply system for supplying a consumer with energy.

[0052] The presented energy supply system comprises a fluid system, such as a refrigerant circuit or a piping system for removing products, in which a fluid flows, and a possible design of the presented compressor.

[0053] The energy supply system may be an electrolysis system or a heat pump.

[0054] According to a third aspect, the presented invention relates to a fluid supply system for supplying a storage device with a fluid.

[0055] The presented fluid supply system comprises a fluid tank, a possible embodiment of the presented compressor configured to compress fluid from the fluid tank, and an interface for fluid-conducting coupling of the compressor to the storage tank.

[0056] Due to the compressor presented, the fluid supply system presented is particularly energy-efficient, low-maintenance and fast.

[0057] The proposed fluid supply system may be intended to be a hydrogen filling station or a carbon dioxide storage facility.

[0058] A fluid system designed as a hydrogen refueling station with the presented compressor enables, especially in combination with a reciprocating pump configured to compress a quantity of fluid in the collection tank with a single stroke such that it is present at a pressure greater than 20 bar, particularly greater than 90 bar, preferably greater than 600 bar, particularly short refueling times, so that several vehicles can be refueled successively without long waiting times.

[0059] For example, the reciprocating pump can have a particularly heavy weight, e.g., heavier than a ton, in order to compress a quantity of fluid needed to fill a vehicle's tank in one stroke.

[0060] Such a weight can, for example, be designed as a concrete element that must be pulled to a height of one meter in order to then provide energy through free fall that forces the liquid into the compressor chamber and compresses the fluid.

[0061] According to a third aspect, the presented invention relates to a method for compressing a fluid, in which the fluid is compressed by means of a possible embodiment of the presented compressor.

[0062] Advantages described in detail with respect to the compressor for compressing a fluid according to the first aspect of the invention apply equally to the energy supply system for supplying a consumer with energy according to the second aspect of the invention and to the method for compressing a fluid according to the third aspect of the invention, and vice versa.

[0063] Further advantages, features, and details of the invention will become apparent from the following description, in which exemplary embodiments of the invention are described in detail with reference to the drawings. The features mentioned in the claims and in the description can each be essential to the invention individually or in any combination.

[0064] They each show schematically: Fig. 1. A representation of a possible design of the presented compressor, Fig. 2 a possible design of the presented procedure, Fig. 3. A possible design of the presented energy supply system, and Fig. 4 a possible design of the presented fluid supply system.

[0065] In Fig. Figure 1 shows a compressor 100 for compressing a fluid.

[0066] The compressor 100 comprises a compressor chamber 101, a collection tank 103 for a liquid, a pump 105 and an optional cooling device 107.

[0067] In the compressor chamber 101, a porous insert 109, e.g. in the form of a metal foam, is arranged, the density of which changes as it passes through the compressor chamber 101.

[0068] Pump 105 is configured to pump liquid from the collection tank 103 into the compressor chamber 101 in order to compress the fluid located in the compressor chamber 101. A first valve 111 is provided for this purpose.

[0069] A second valve 113 is provided to transfer the liquid from the compressor chamber 101 to the collection tank 103.

[0070] A third valve 115 is provided to direct fresh fluid into the compressor chamber 101.

[0071] A fourth valve 117 is provided to discharge the compressed fluid from the compressor chamber 101.

[0072] A process or procedure 200 for compression using the compressor 100 takes place in several stages. In a first step 201, the third valve 115 is opened and fresh fluid flows into the compressor chamber 101, while the fourth valve 117 is closed.

[0073] In a second step 203, the second valve 113, the third valve 115 and the fourth valve 117 are closed and the first valve 111 is opened, so that fluid from the collection tank 103 is directed via the pump 105 through the cooling device 107 into the compressor room 101.

[0074] In a third step 205, the compressor chamber 101 is filled with liquid. To compress the fluid, the pump 105 is stopped and the first valve 111 is closed again.

[0075] In a fourth step 207, the fourth valve 117 is opened and the compressed fluid is discharged from the compressor chamber 101.

[0076] In a fifth step 209, the fourth valve 117 is closed again and the third valve 115 and the second valve 113 are opened, so that the liquid from the compressor chamber 101 flows into the collection tank 103 and uncompressed fluid is drawn into the compressor chamber 101.

[0077] Another compaction cycle starts with the second step 203.

[0078] In Fig. Figure 3 shows an energy supply system 300. The energy supply system 300 includes the compressor 100 according to Fig. 1 and a fluid system 301 in which fluid flows. In this example, the energy supply system 300 is designed as a heat pump for heating a building.

[0079] The particularly energy-efficient compression by the compressor 100 avoids a temperature increase, as occurs with classic heat pump final compressors, and maximizes the efficiency of the energy supply system 300.

[0080] Furthermore, common heat pump compressors are oil-lubricated and generally cannot operate below 25% of their rated speed, as otherwise the oil lubrication fails. As a result, the systems then have to cycle on and off frequently. To avoid excessively short cycles, heat pump manufacturers specify a buffer storage tank, especially in houses without underfloor heating, i.e., those with radiators.

[0081] By using the Energy Supply System 300, a heating system can be operated without a buffer storage tank, and cycling of the Energy Supply System 300 is minimized, resulting in a particularly wide operating range. This means that a specific configuration of the Energy Supply System 300 can be used for different houses with varying heating loads.

[0082] In Fig. Figure 4 shows a fluid supply system 400. The fluid supply system 400 includes the compressor 100 according to Fig.1, a fluid tank 401 and an interface 403 for fluid-conducting coupling of the compressor with the storage tank.

[0083] Interface 403 is shown here as an example of a fuel dispenser, so that the fluid supply system 400 here forms an example of a hydrogen filling station.

[0084] Thanks to the compressor 100, the fluid supply system 400 is particularly energy-efficient, fast and requires little maintenance.

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