[001] The invention relates to the field of machine building, in particular to hydraulic displacement machines, namely to compressors, in which the simultaneous supply of liquid and gaseous media to the working chamber takes place, and can be used for hydraulic compression of hydrogen.

[002] Hydraulic gas compression technology has a number of significant advantages over reciprocating compressors. The known technical solution [1] implements the design of the compressor, in which the piston compresses the liquid in the cylinder with a certain volume and supplies it to another container filled with gas through the inlet valve. When the tank is filled with liquid, the gas is compressed and at the end of the cycle it is pushed through the open outlet valve into the accumulation tank. At the end of each cycle, the pressure in the accumulation tank increases discretely and reaches the level of gas pressure in the cylinder.

[003] A disadvantage of the known design is that the volume of the compression chamber cannot exceed the volume of the cylinder of the piston pump. This limits the possibility of compressing a large volume of gas in one cycle and consequently reduces the efficiency of the pump.

[004] To control the degree of compression in the known technical solutions [2, 3], it is proposed to place a plate inside the gas compression tank that floats on the surface of the liquid. At the maximum filling level, the plate rises and affect the sensor, which causes the liquid supply to be cut off from the container.

[005] This method of controlling the filling of the volume of the container with liquid is associated with uncertainty in the position of the plate in the movable volume of liquid, which reduces the accuracy of determining the level of liquid in the container. As a result, the device has a restriction on the degree of gas compression, and also reduces the reliability of the device operation. The degree of hydrogen compression is not regulated during operation of the device.

[006] A device [4] is known, which comprises a tank for storing low-pressure hydrogen, two cylinders of the first stage of hydrogen compression, a cylinder of the second stage of hydrogen compression and a buffer cylinder for storing high-pressure hydrogen, connected to each other by pipelines. Hydraulic compression system consists of fluid tank and high-pressure fluid pump communicated via pipelines with cylinders. The liquid level in the cylinders and hence the degree of hydrogen compression are controlled by the liquid flow meters. Hydrogen and liquid flows are switched by controlled valves. Optical sensors for monitoring the flow rate help to control the flow rate in the pipelines.

[007] In accordance with the Boyle-Mariotte law, the increase in the hydrogen pressure in the buffer cylinder relative to the pressure in the hydrogen storage tank is determined by the possibility of compressing the gas in the cylinders of the first and second stages by filling these cylinders with liquid. Moreover, the compression ratio in cylinders of the first and second compression stages is defined by device design and is constant. However, when low-pressure hydrogen produced by hydrolysis of water using renewable energy sources is compressed, it becomes necessary to use several compression stages, which complicates the design.

[008] The technical problem solved by the present invention is to increase the efficiency of the low-pressure hydrogen hydraulic compression device obtained under conditions of limited productivity of the electrolyser when using renewable energy sources, and to expand the functional capabilities of the device.

[009] In the device for hydrogen hydraulic compression comprising a low-pressure hydrogen tank, a high-pressure hydraulic pump with its inlet connected via pipeline with a container filled with a working fluid (fluid), a first cylinder and a second cylinder of a first compression stage, a cylinder of a second compression stage and a buffer cylinder for storing a high-pressure hydrogen; an outlet of said tank is connected via pipeline with inlets of a second valve and a third valve of the first group with their outlets connected with outlets of the first cylinder and the second cylinder of the first compression stage, respectively, wherein said outlets and inlets of the second valve and the third valve are connected with the inlets of the first and the second valves, respectively, the outputs of which are connected to the output hole of the cylinder of the second compression stage and the input of a first valve of a third group, an output of which is connected to the input hole of the buffer cylinder for storing the high-pressure hydrogen; the output of the hydraulic pump is connected to inputs of three valves of a fourth group and an input of a safety valve, wherein the outputs of the three valves of the fourth group are connected to an input of one of three fluid flow meters, respectively, wherein the outputs of the first flow meter and the second flow meter are connected to the inlet of the first cylinder and the second cylinder of the first hydrogen compression stage, respectively, and the output of the third flow meter is connected to the inlet of the cylinder of the second hydrogen compression stage, wherein the outputs of each of the three said valves of the fourth group and the inputs of the flow meters are also connected to an input of one of three valves of a fifth group, respectively, the output of which is connected to the container with the fluid through one of the three optical sensors, respectively, and the output of the safety valve is directly connected to the said container; the outlet of the buffer cylinder is connected by a pipeline to the valve for supplying hydrogen to the consumer, the outputs of the cylinders of the first hydrogen compression stage and the cylinder of the second hydrogen compression stage are connected to one of three pressure sensors, respectively, according to the present invention, the low-pressure hydrogen storage tank has two inlets, the first inlet of which is connected to an outlet of a valve for supplying hydrogen from an external source, the inlet of which is connected to an electrolyser connected to electric power sources, and the second outlet hole is connected to an inlet of a first valve of the first group, the outlet of which is connected by pipeline to the inlets of the second valve and the third valve of the first group, the outlets of which are connected to the outlets of the first cylinder and the second cylinder of the first compression stage, wherein the device is equipped with an additional container, the inlet of which is connected by pipelines to the inlet of an additional valve and an outlet of a second valve of the third group, the inlet of which is connected to the outlet of the cylinder of the second stage of hydrogen compression and the outlets of the valves of the second group connected to it, the inlet of the first valve of the third group and to the third pressure sensor, the output of the additional valve is connected to the output of the first valve of the first group, which is connected to the inputs of the second valve and the third valve of the first group.

[0010] The device may comprise an electrolyser that comprises a container of water connected to the electrode unit.

[0011] The device may additionally comprise an electric power source, which comprises renewable energy converters, which are photovoltaic panels and/or wind turbines connected to generators. [0012] Fluid flow meters can be reversible.

[0013] The fluid flow meters can be unidirectional and the device is additionally provided with a sixth group of valves which are connected in pairs, wherein in a first pair of valves and a second pair of valves, the output of the first valve is connected to the input of the second valve of the corresponding pair and their connection points are connected to the inlet holes in the first cylinder and to the second cylinder of the first hydrogen compression stage, respectively, and in a third pair of valves, the output of the first valve is connected to the input of the second valve and their connection point is connected to the input of the cylinder of the second stage of hydrogen compression, wherein the free inputs of the second valves of each pair of the sixth group are connected to the outputs of the corresponding flow meters of the fluid and the inputs of the first valve, the second valve and the third valve of the fifth group, respectively, the free outputs of the first valves of each pair of valves are connected to inputs of fluid flow meters and outputs of the first valve, the second valve and the third valve of the forth group, respectively.

[0014] The proposed device for hydraulic compression of hydrogen is explained by figures, wherein is shown:

[0015] Figure 1 is a block diagram of the proposed device for hydraulic compression of hydrogen according to the scheme of the first embodiment, and the arrows show the direction of movement of hydrogen and fluid.

[0016] Figure 2 is a block diagram of a portion of the proposed hydrogen hydraulic compression device according to the scheme of the second embodiment using unidirectional fluid flow meters.

[0017] In the description of the device, the controlled valves are grouped by functional purpose: valves for hydrogen switching - the first group (8 - 10); the second group (11, 12); the third group (14, 39); the fourth group (16 - 18), valves for fluid switching - the fifth group (23 - 25); the sixth group (42 -47).

The present invention is explained by examples of its specific implementation.

Embodiment 1. [0018] Hydrogen hydraulic compression device (FIG. 1) comprises a low-pressure hydrogen storage tank (1), a high-pressure hydraulic pump (2), the inlet of which is connected by a pipeline to a container (3) filled with fluid (4), a first cylinder (5), and a second cylinder (6) of the first compression stage, a cylinder (13) of the second compression stage and a buffer cylinder (15) for high-pressure hydrogen storage. The outlet hole of said tank (1) is connected by pipeline to the inlets of the second valve (9) and the third valve (10) of the first group, the outlets of which are connected to the outlets of the first cylinder (5) and the second cylinder (6) of the first compression stage, respectively. Said outlets and inlets of the second valve (9) and the third valve (10) of the first group are also connected to inlets of the first (11) and second (12) valves of the second group, respectively, the outlets of which are connected to the outlet of the cylinder (13) of the second compression stage and the inlet of the first valve (14) of the third group, the outlet of which is connected to the inlet of the buffer cylinder (15) for storing high- pressure hydrogen. The output of the hydraulic pump (2) is connected to the inputs of three valves (16-18) of the fourth group and the input of the safety valve (19), wherein the outputs of the three valves (16-18) of the fourth group are connected to the input of one of the three fluid (4) flow meters (20-22), respectively. The fluid (4) flow meters (20-22) are reversible.

[0019] The outputs of the first flow meter (20) and the second flow meter (21) are connected to the inlet of the first (5) cylinder and the second (6) cylinder of the first hydrogen compression stage, respectively, and the output of the third flow meter (22) is connected to the inlet of the cylinder (13) of the second hydrogen compression stage. The outputs of each of the three said valves (16-18) of the fourth group and the inputs of the flow meters (20-22) are also connected to an input of one of three valves (23-25) of a fifth group, respectively, the output of which is connected to the container (3) with the fluid (4) through one of three optical sensors (26-28), respectively. The outlet of the safety valve (19) is directly connected to the said container (3). The outlet of the buffer cylinder (15) is connected by a pipeline to the valve (29) for supplying hydrogen to the consumer, and the outputs of the cylinders (5, 6) of the first hydrogen compression stage and the cylinder (13) of the second hydrogen compression stage are connected to one of the three pressure sensors (30-32), respectively. The low-pressure hydrogen storage tank (1) has two inlets, the first inlet of which is connected to an outlet of a valve (33) for supplying hydrogen from an external source, the inlet of which is connected to an electrolyser (34) connected to electric power sources (35). The electrolyser (34) comprises a container with water (7) connected to the unit of electrodes (36). The electric power source (35) comprises renewable energy converters represented by photoelectric panels (40) and/or wind turbines (41) connected to generators.

[0020] The second outlet hole of the tank (1) is connected to an inlet of a first valve (8) of the first group, the outlet of which is connected by pipeline to the inlets of the second valve (9) and the third valve (10) of the first group, the outlets of which are connected to the outlets of the first cylinder (5) and the second cylinder (6) of the first compression stage. The device is equipped with an additional container (37), the inlet of which is connected by pipelines to the inlet of an additional valve (38) and an outlet of a second valve (39) of the third group, the inlet of which is connected to the outlet of the cylinder (13) of the second stage of hydrogen compression and the outlets of the valves (11, 12) of the second group connected to it, the inlet of the first valve (14) of the third group and to the third pressure sensor (32), and the outlet of the additional valve (38) is connected to the outlet of the first valve (8) of the first group, which is connected to the inlets of the second valve (9) and the third valve (10) of the first group.

Description of device operation

[0021] High-pressure hydrogen from 50 to 100 MPa is used to refuel vehicles at filling stations. However, due to leaks, the ability to retain hydrogen at this high pressure for a long time is limited. Accordingly, booster compressors and buffer tanks for high-pressure hydrogen should be used at filling stations.

[0022] The proposed device is designed for use as a booster compressor in a filling station system, where hydrogen is used, brought by a truck in cylinders with a pressure of up to 25 MPa or produced locally by electrolysis of water in limited quantities with a pressure of up to 3.0 MPa. For the production of "green" hydrogen, wind and solar energy can be used, converted into electrical power using, for example, wind turbines and/or photovoltaic panels.

[0023] The proposed device operates on the principle of hydraulic compression of hydrogen in closed cylinders filled with a fluid suitable for compression of hydrogen. The cycling of the processes of compression and filling with a new portion of low-pressure hydrogen occurs in accordance with a certain valve switching algorithm. All valves in the device circuit are controllable and connected to the control unit, which is not shown in the diagram.

[0024] The operation algorithm provides for the joint operation of all stages of hydrogen compression, and this leads to a gradual increase in pressure in the buffer cylinder (15) for the accumulation of high-pressure hydrogen. In the first embodiment of the device (FIG. 1) in the initial state, the tank (1) is filled with hydrogen obtained from the source with an initial pressure, and fluid (4) is poured into the container (3).

[0025] At the same time, after switching on the control unit, the controlled valves (8-12, 14, 33, 38, 39) in the device are opened, the valve (29) closed, and hydraulic pump (2) does not create pressure in the pipelines. In the meantime, the cylinders (5), (6), (13) and the buffer cylinder (15) and the additional container (37) are filed with the hydrogen from the tank (1) with the corresponding pressure. After that the valves (8-12, 14, 38, 39) are closing.

[0026] The next step is to switch on the hydraulic pump (2) and open the third valve (18) of the fourth group, through which the fluid (4) from the container (3) is supplied to the second cylinder (6) of the first compression stage through the pipeline and through the second flow meter (21). Filling the second cylinder (6) of the first compression stage with fluid (4) leads to a decrease in the volume of hydrogen, and its pressure increases proportionally.

[0027] The amount of fluid (4) entering the second cylinder (6) of the first compression stage is measured by the second flow meter (21). When the predetermined degree of hydrogen compression in the second cylinder (6) of the first compression stage is reached, the third valve (18) of the fourth group is closed and the second valve (12) of the second group is opened. Simultaneously with this process, the second valve (9) of the first group opens, and hydrogen from the tank (1) enters the first cylinder (5) of the first compression stage. It is filled with hydrogen with initial pressure, and the second valve (9) of the first group is closed.

[0028] Through the second valve (12) of the second group, compressed hydrogen enters the cylinder (13) of the second compression stage and simultaneously through the first valve (16) of the fourth group and the first flow meter (20), fluid (4) enters the first cylinder (5) of the first compression stage, where hydrogen is compressed. At the same time, the transfer of compressed hydrogen from the second cylinder (6) of the first compression stage to the cylinder (13) of the second compression stage is completed, and then the second valve (12) of the second group is closed.

[0029] Further, the third valve (10) of the first group and the third valve (25) of the fifth group are opened, as a result of which hydrogen from the tank (1) through the open first valve (8) of the first group extrudes fluid (4) from the second cylinder (6) of the first compression stage into the container (3) through the second flow meter (21) and the third optical sensor (28) to control the fluid flow. The direction of the fluid flow through the second flow meter (21) changes the direction, therefore, the said flow meter (21) operates in the reverse counting mode and issues a signal to close the third valve (10) of the first group, when the measured volumes of fluid pumped in one and the other direction are equalised.

[0030] In this state, the working second cylinder (6) of the first compression stage is filled with hydrogen and prepared for a new compression cycle, and hydrogen in the first cylinder (5) of the first compression stage is in a compressed state. At this moment, the first valve (11) of the second group is opened, and compressed hydrogen from the first cylinder (5) of the first compression stage enters the cylinder (13) of the second compression stage. An additional volume of compressed hydrogen from the first cylinder (5) increases the level of hydrogen pressure in the cylinder (13) of the second compression stage, after which the first valve (11) of the second group is closed. At the same time, the third valve (18) of the fourth group is opened, and the second cylinder (6) of the first compression stage is filled with fluid (4), which leads to the compression of a new portion of hydrogen.

[0031] After closing the first (11) valve of the second group, the second valve (9) of the first group and the first valve (23) of the fifth group are opened, and hydrogen from the tank (1) extrudes fluid (4) from the cylinder of the first (5) first compression stage into the container (3) through the first flow meter (20) and the first optical sensor (26). The first flow meter (20) also operates in reverse counting mode and issues a signal to close the second valve (9) of the first group and the first valve (23) of the fifth group, when the measured volumes of fluid pumped in one and the other direction are equalised.

[0032] Hydrogen pressure in the cylinder (13) of the second compression stage through several repeated cycles reaches its maximum and becomes equal to pressure in the first and second cylinders (5, 6) of the first compression stage. After that, the first and second valves (11, 12) of the second group are closed, and the second valve (17) of the fourth group is opened, through which fluid (4) is supplied to the cylinder (13) of the second compression stage.

[0033] After completion of the hydrogen compression cycle in the cylinder (13) of the second stage, the second valve (17) of the fourth group is closed, and the first and second valves (14, 39) of the third group are opened. High-pressure compressed hydrogen enters the buffer cylinder (15) and the additional container (37).

[0034] After removal of compressed hydrogen from the cylinder (13) of the second stage, the first and second valves (14, 39) of the third group are closed and the second valve (24) of the fifth group is opened, as a result of which fluid (4) flows through the third flow meter (22) and the second optical sensor (27). The third flow meter (22) also operates in reverse counting mode and issues a signal to close the second valve (24) of the fifth group, when the measured volumes of fluid pumped in one and the other direction are equalised.

[0035] Optical sensors of fluid flow control (26-28) duplicate operation of fluid flow meters (20-22) to exclude ingress of hydrogen into the container (3) in case of rupture of fluid flow (4).

[0036] In the process of cyclic switching of valves, a situation may arise when valves (16- 18) of the fourth group can simultaneously receive a command to close, since the control of these processes depends on signals from the output of flow meters (20-22) and optical sensors (26-28). As a result, simultaneous closing of valves (16-18) of the fourth group is possible, which will lead to a sharp increase in pressure at the outlet of the high-pressure hydraulic pump (2). Switching on the safety valve (19) serves to bypass the fluid flow (4) from the outlet of the hydraulic pump (2) and reduces the pressure in the pipelines in this case. Thus, the process of accumulation of high-pressure hydrogen in the buffer cylinder (15) and the additional container (37) is completed.

[0037] The limited hydrogen reserves in the tank (1) lead to a decrease in the hydrogen pressure during the operation of the device, which is supplied for compression to the cylinders (5, 6) of the first stage. This raises the problem of how to maintain a high hydrogen pressure, which fills the buffer cylinder (15) at a low pressure in the tank (1).

[0038] To compensate for this phenomenon, the device provides for the possibility of filled cylinders (5, 6) of the first compression stage with hydrogen accumulated in an additional container (37). While maintaining the compression ratio in these cylinders, the outlet pressure also increases and is supplied to the cylinder (13) of the second compression stage. Accordingly, after compression in the cylinder (13) of the second compression stage, the pressure increases without using an additional compression stage.

[0039] Algorithm of device operation provides for supply of compressed hydrogen to cylinders (5, 6) of the first compression stage from additional container (37) through additional valve (38) and open second valve (9) of the first group or the third valve (10) of the first group. This makes it possible to increase hydrogen pressure at the inlet in the first cylinder (5) and in the second cylinder (6) of the first compression stage.

[0040] After hydrogen is compressed in cylinder (13) of the second compression stage by fluid (4), hydrogen is supplied only to the buffer cylinder (15) through the first valve (14) of the third group. Thus, it is possible to maintain a high pressure in the buffer cylinder (15) during the filling of the tank (1) with hydrogen produced by the electrolyser (34) from renewable energy sources using a wind turbine (41) and/or a photovoltaic panel (40).

Embodiment 2.

[0041] The hydrogen hydraulic compression device is similar to that described in Embodiment 1, except for the portion shown in FIG. 1 is indicated by a dashed line (VI) and this part (V2) is designed as shown in FIG. 2.

[0042] In the second embodiment of the device, it is possible to use unidirectional fluid (4) flow meters (20-22), which are not used in the reverse counting mode.

[0043] The device is additionally equipped with the sixth group of valves (42-47), which are connected in pairs. In a first pair of valves (42, 43) and a second pair of valves (44, 45), the output of the first valve (42, 44) is connected to the input of the second valve (43, 45) of the corresponding pair and their connection points are connected to the inlet holes in the first cylinder (5) and to the second cylinder (6) of the first hydrogen compression stage, respectively. And in a third pair (46, 47) of valves, the output of the first valve (46) is connected to the input of the second valve (47) and their connection point is connected to the input of the cylinder (13) of the second stage of hydrogen compression. The free inputs of the second valves (42, 46, 44) of each pair of the sixth group are connected to the outputs of the corresponding flow meters (20-22) of the fluid (4) and the inputs of the first valve (23), the second valve (24) and the third valve (25) of the fifth group, respectively. Free outputs of the first valves of each pair of valves (43, 47, 45) are connected to inputs of fluid (4) flow meters (20-22) and outputs of the first valve (16), the second valve (17) and the third valve (18) of the forth group, respectively.

[0044] In such a connection scheme, the direction of fluid (4) low from the outlet of the hydraulic pump (2) and from the inlet holes in the first and second cylinders (5, 6) of the first compression stage and in the cylinder (13) of the second hydrogen compression stage through the flow meters (20-22) does not change.

[0045] The peculiarity of the design of the proposed device consists in the use of fluid (4) flow meters (20-22) to determine the degree of hydrogen compression. This avoids the use of fluid level sensors, which must be installed inside the cylinders to control the degree of hydrogen compression. The pressure in the cylinders (5, 6 and 13) of the first and second compression stages is controlled by pressure sensors (30-32).

[0046] In this case, the information used to generate commands for switching the valves can be corrected in accordance with the operation algorithm recorded in the device control unit software. As a result, the reliability of the device is improved, as the control system continuously receives information on the degree of filling of the cylinders with fluid.

[0047] In the mentioned software, actions can be provided to solve a possible situation when a conflict of signals from sensors occurs. In this case, the cyclic process can be restored without returning to the initial state of the device and draining the fluid into the container (3) from the cylinders (5, 6) of the first compression stage and the cylinder (13) of the second compression stage.

[0048] After filling the buffer cylinder (15) with hydrogen with a given pressure level, the device is ready to supply it to the consumer through the valve (29).

[0049] Improved reliability of the device contributes to increased efficiency of the low- pressure hydrogen hydraulic compression device and increases the rate of filling the buffer cylinder (15) with high-pressure hydrogen. This is especially evident in the conditions of reducing the hydrogen pressure in the tank (1) during its flow rate for filling the cylinders (5, 6) of the first compression stage. This makes it possible to expand functional capabilities of the device and to use photovoltaic panels (40) and/or wind turbines (41) connected to generators for hydrogen production in the electrolyser (34) as source of electric power (35). References

1. RU2736555, 2020-11-18, F04B35/02, F04B19/06.

2. CN105464927, 2015-12-31, F04B35/02; F04B39/00; F04B39/12.

3. JP2016188675, 2015-03-30, H01M8/0606; C01B3/04; C25B1/04; F17C7/00; H01M8/00.

4. Bezrukovs, V., et al. "Hydrogen Hydraulic Compression System for Refuelling Stations." Latvian Journal of Physics and Technical Sciences 59. s3 (2022): 96-105. D01: 10.2478/lpts-2022-0028 (closest prior art)