Power generation system

Abstract

This invention provides a power generation system that effectively utilizes relatively low-temperature waste heat to generate electricity. [Solution] A power generation system comprising: a generating device that generates steam at a first temperature higher than the waste heat using a fluid having a predetermined waste heat and the power generated by a first power generation device that utilizes renewable energy; a heat storage device that stores heat using the steam at the first temperature; and a second power generation device that generates electricity using steam at a second temperature obtained based on the heat storage temperature of the heat storage device.

Description

Technical Field

[0001] The present invention relates to a power generation system that generates electricity using waste heat at a relatively low temperature.

Background Art

[0002] For example, a heat storage system that stores waste heat at a relatively low temperature (for example, about 100°C to 200°C) discharged from power plants, factories, hot springs, households, etc. for use as a cold heat source or a warm heat source is known (Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, this waste heat is not effectively utilized except for being used in limited applications such as cold heat sources and warm heat sources, and at present, the waste heat that is not effectively utilized is simply discarded as it is.

[0005] The present invention has been made in view of the above problems, and one object thereof is to provide a power generation system that effectively utilizes the discharged relatively low-temperature waste heat to generate electricity.

Means for Solving the Problems

[0006] One aspect of the present invention for achieving the above object is a power generation system including: a generation device that generates steam at a first temperature higher than the waste heat using the generated electric power of a first power generation device that uses a fluid having a predetermined waste heat and renewable energy; a heat storage device that stores heat using the steam at the first temperature; and a second power generation device that generates electricity using steam at a second temperature obtained based on the heat storage temperature of the heat storage device.

[0007] According to the power generation system of the present invention, it is possible to generate electricity by effectively utilizing waste heat at relatively low temperatures.

[0008] Furthermore, another aspect of the present invention for achieving the above objectives is a power generation system in which the first power generation device generates electricity using solar energy as the renewable energy source, and the power generated by the first power generation device includes surplus power from the power generated by the first power generation device that is not consumed by the owner of the first power generation device and is not traded in the electricity trading market.

[0009] According to the power generation system of the present invention, the second power generation device can effectively utilize the surplus power generated by the first power generation device to generate electricity.

[0010] Another aspect of the present invention for achieving the above objectives is that, in a power generation system, the generation of steam at the first temperature by the generating device and the storage of heat by the heat storage device are performed during a first time period (e.g., daytime) in which the first power generation device is capable of generating power, and the second power generation device is performed during a second time period (e.g., nighttime) in which the first power generation device is not capable of generating power.

[0011] According to the power generation system of the present invention, at night when the solar power generation device is unable to generate electricity, it becomes possible to sell the electricity generated by the second power generation device at a relatively high price, for example, through the electricity trading market.

[0012] Furthermore, another aspect of the present invention for achieving the above objectives is that the heat storage device constituting the power generation system includes a heat storage material and a heat transfer tube for transferring heat to the heat storage material inside the heat storage device, wherein steam at a first temperature is taken into the heat transfer tube during the first time period, and steam at a second temperature is taken out from the heat transfer tube during the second time period.

[0013] Furthermore, another aspect of the present invention for achieving the above objectives is that the second power generation device constituting the power generation system may be a device that generates electricity using steam of an organic medium.

[0014] Furthermore, the problems disclosed in this application and their solutions will be made clear from the description in the section on embodiments for carrying out the invention and from the drawings. [Effects of the Invention]

[0015] According to the present invention, it is possible to provide a power generation system that effectively utilizes relatively low-temperature waste heat to generate electricity. [Brief explanation of the drawing]

[0016] [Figure 1] This diagram illustrates the operation in power generation system 1, which utilizes a fluid containing waste heat to store heat at a temperature higher than that waste heat. [Figure 2] This diagram illustrates the operation of power generation system 1, which uses steam at its thermal storage temperature to generate electricity. [Modes for carrying out the invention]

[0017] The following matters will become clear from this specification and the accompanying drawings. The present invention will be described below with reference to the accompanying drawings in accordance with one embodiment thereof. In this embodiment, identical or similar components may be denoted by the same reference numeral and their descriptions may be omitted.

[0018] Figure 1 is a diagram illustrating the operation of power generation system 1 in which heat is stored at a temperature higher than the waste heat using a fluid containing waste heat. Figure 2 is a diagram illustrating the operation of power generation system 1 in which electricity is generated using steam at the heat storage temperature. In power generation system 1, for example, waste heat (e.g., 100°C to 200°C) contained in a fluid (liquid or gas) discharged from a power plant or factory is used.

[0019] The power generation system 1 includes a steam generator 100, a steam separator 110, a heater 120, a heat storage tank 130, a water storage tank 140, a feed water pump 150, a compressor 160, an ORC (Organic Rankine Cycle) power generation device 170, and on-off valves 200, 210, 220, 230, 240, 250 as means for generating power using a fluid having waste heat. For convenience of explanation, the on-off valves 200, 210, 220, 230, 240, 250 shown in white indicate that the valves are open, and the on-off valves 200, 210, 220, 230, 240, 250 shown in black indicate that the valves are closed.

[0020] Each of the steam generator 100, the steam separator 110, the heater 120, the heat storage tank 130, the water storage tank 140, the feed water pump 150, the compressor 160, and the ORC power generation device 170 is connected via a metal pipe 190 (metal pipes 190A to 190K) through which steam or water passes when the heat storage operation of FIG. 1 and the power generation operation of FIG. 2 are performed. Note that the compressor 160 is used when compressing steam b7 to, for example, twice or more the atmospheric pressure. Depending on the degree of compression, instead of the compressor 160, a fan that compresses to, for example, 1.1 times the atmospheric pressure or a blower that compresses to, for example, 1.1 to 2 times the atmospheric pressure may be employed.

[0021] Specifically, the between the inlet 110A of the steam separator 110 and the outlet 101B of the steam generator 100 is connected by a metal pipe 190A. The between the inlet 110B of the steam separator 110 and the outlet 140E of the water storage tank 140 is connected by a metal pipe 190B via the feed water pump 150. The between the outlet 110C of the steam separator 110 and the inlet 101A of the steam generator 100 is connected by a metal pipe 190C. The between the outlet 110D of the steam separator 11 and the inlet 120A of the heater 120 is connected by a metal pipe 190D via the on-off valve 200.

[0022] Also, between the inlet 140A of the water storage tank 140 and the inlet / outlet 130B of the heat storage tank 130, they are connected by a metal pipe 190E via a shut-off valve 240. Between the inlet 140B of the water storage tank 140 and the outlet 170B of the ORC power generation device 170, they are connected by a metal pipe 190F. Between the outlet 140D of the water storage tank 140 and the outlet 110D of the steam separator 110, they are connected by a metal pipe 190G via a compressor 160 and a check valve 180. Incidentally, the water storage tank 140 is provided with an inlet 140C for water replenishment in case it is unable to supply the required amount of water to the inlet 110B of the steam separator 110.

[0023] Between the inlet / outlet 130A of the heat storage tank 130 and the outlet 120B of the heater 120, they are connected by a metal pipe 190H via a shut-off valve 210. Between the inlet / outlet 130A of the heat storage tank 130 and the inlet 170A of the ORC power generation device 170, they are connected by a metal pipe 190I via a shut-off valve 220. Between the inlet / outlet 130B of the heat storage tank 130 and the outlet 110D of the steam separator 110, they are connected by a metal pipe 190J via a shut-off valve 230. Between the inlet / outlets 130A and 130B of the heat storage tank 130, they are connected by a metal pipe 190K via a shut-off valve 250.

[0024] Incidentally, as the metal pipe 190, for example, at least one of low alloy steel, carbon steel pipe, copper pipe, stainless steel pipe, cast iron pipe, lead pipe, etc. can be adopted.

[0025] The steam generator 100 exchanges the temperature of the water a1 supplied to the inlet 101A of the steam generator 100 with the waste heat of the fluid, and generates steam b1 from the outlet 101B of the steam generator 100.

[0026] The steam generator 100 has a metal pipe 102 through which a fluid containing waste heat flows, and a metal pipe 101 through which water a1 flows, as means to achieve the above functions. Metal pipe 101 is connected between the inlet 101A and the outlet 101B so that water a1 supplied to the inlet 101A is output as steam b1 (wet steam) from the outlet 101B through heat exchange. Metal pipe 102 is connected between the inlet 102A and the outlet 102B so that fluid containing waste heat supplied to the inlet 102A is output from the outlet 102B after heat exchange. Furthermore, metal pipes 101 and 102 are arranged opposite each other to enable efficient heat exchange between them.

[0027] The steam-water separator 110 has a drum 111 that contains a mixture of steam and water, and the drum 111 is provided with inlets 110A, 110B and outlets 110C, 110D. Steam b1 output from outlet 101B of the steam generator 100 is supplied to inlet 110A. Water a2 stored in the water tank 140 is supplied to inlet 110B using a pump 150. The steam-water separator 110 separates the steam and water supplied to the drum 111 by improving the dryness of the steam present in the drum 111 to a predetermined dryness. The water a1 separated in the drum 111 is output from outlet 110C, and this water a1 is supplied to inlet 101A of the steam generator 100. Steam b2 separated in the drum 111 is output from outlet 110D. When the heat storage tank 130 is storing heat, this steam b2 is supplied to the inlet 120A of the heater 120 via the on-off valve 200. On the other hand, when the ORC power generator 170 is generating electricity, this steam b2 is supplied to the inlet 130B of the heat storage tank 130 via the on-off valve 230, which opens and closes complementary to the on-off valve 200. Furthermore, if steam is stored in the water storage tank 140, the steam b7 (saturated steam) output from the outlet 140D of the water storage tank 140 may be mixed with the steam b2 through the compressor 160 and check valve 180 so that it is reheated by the heater 120.

[0028] The heater 120 heats the steam b2 supplied to the inlet 120A to a temperature higher than the temperature of the steam b2, and outputs the superheated steam b3 from the outlet 120B. A metal pipe 121 is connected between the inlet 120A and the outlet 120B of the heater 120, through which the steam b2 heated by the heater 120 passes. When the metal pipe 121 is heated, steam b3 is output from the outlet 120B.

[0029] The heater 120 operates by being supplied with power from, for example, the electricity generated by the first power generation device that utilizes renewable energy. As renewable energy, at least one of the following can be used: solar power, wind power, hydropower, geothermal energy, biomass, etc. In this embodiment, the first power generation device is a solar power generation device that generates electricity using sunlight, and the electricity generated by the solar power generation device supplied to the heater 120 is surplus electricity that is not consumed by the owner of the solar power generation device and is not subject to trading in the electricity trading market. When the heat storage tank 130 is storing heat, the steam b3 output from the outlet 120B is supplied to the inlet / outlet 130A of the heat storage tank 130 via the on / off valve 210.

[0030] For example, a sheathed heater can be used as the heater 120. A sheathed heater has a structure in which a coiled nichrome wire, which serves as the heating element, is passed through a metal tube 122. In the case of a sheathed heater, the steam b2 can be heated efficiently by changing the shape of the metal tube 122 to match the shape of the metal tube 121 through which the steam b2 passes.

[0031] When the heat storage tank 130 is storing heat, the inlet / outlet 130A becomes the inlet for steam b3, and the inlet / outlet 130B becomes the outlet for water a3 and steam b4. For example, when heat storage is performed from a state where the heat storage temperature of the heat storage tank 130 is 100°C or lower, the steam b3 that heats the heat storage tank 130 may condense into water a3 midway through the heat storage tank 130 and be output from the inlet / outlet 130B. On the other hand, when the ORC power generation device 170 is generating electricity, the inlet / outlet 130B becomes the inlet for steam b2, and the inlet / outlet 130A becomes the outlet for steam b5, which is at a lower temperature than steam b3.

[0032] The heat storage tank 130 is equipped with a heat storage material 131 for storing heat and heat transfer tubes 132 for transferring heat to the heat storage material 131. The heat storage material 131 can be at least one of the following: sand, a mixture of sand and alumina, carbon bricks, fired magnesia bricks, high-alumina bricks, etc. The heat storage material 131 is arranged to fill, for example, the entire interior of the heat storage tank 130.

[0033] Within the heat storage tank 130, a heat transfer tube 132 is connected between inlet / outlet 130A and inlet / outlet 130B. For example, inlet / outlet 130A is located at a high position on the side of the heat storage tank 130, and inlet / outlet 130B is located at a low position on the side of the heat storage tank 130. The heat transfer tube 132 is bent and meanders within the heat storage tank 130, close to the side, as it travels from inlet / outlet 130A to inlet / outlet 130B.

[0034] When the heat storage tank 130 is performing heat storage, steam b3 is supplied to the inlet / outlet 130A, and as the steam b3 passes through the heat transfer tubes 132, the heat transfer tubes 132 are heated. The heat storage material 131 then exchanges heat with the heat transfer tubes 132, and heat is stored as the heat from the heat transfer tubes 132 is transferred to the heat storage material 131. On the other hand, when the ORC power generation device 170 is generating electricity, steam b2 is supplied to the inlet / outlet 130B of the heat storage tank 130, and as a result, steam b5 is output from the inlet / outlet 130A, and this steam b5 is supplied to the inlet 170A of the ORC power generation device 170.

[0035] The ORC power generator 170 is one of the power generators that can be adopted as a second power generator. The ORC power generator 170 is a device that drives a turbine with steam generated by vaporizing an organic medium from a liquid state, and generates electricity with the driving force of the turbine. As the organic medium, a medium with a low evaporation temperature such as silicone oil, chloromethane, or ethanol can be used. This organic medium is vaporized into steam by steam b5 supplied to the inlet 170A. A metal pipe 171 through which steam b5 passes is connected between the inlet 170A and the outlet 170B. After heat exchange with the organic medium inside the ORC power generator 170, the steam b5 becomes water a4 and is output from the outlet 170B. This water a4 is hot water (for example, 60°C) and is supplied to the inlet 140B of the water storage tank 140.

[0036] When the ORC power generator 170 is generating electricity, and especially when the heat storage temperature of the heat storage tank 130 is sufficiently high, the steam b5 output from the inlet / outlet 130A of the heat storage tank 130 may rise too high to the temperature required for the organic medium used in the ORC power generator 170 to be steamed. In this case, the shut-off valve 250 is opened to mix steam b5 with steam b2, which is at a lower temperature than steam b5, and adjust the temperature of steam b5 to lower it. In other words, the shut-off valve 250 is a bypass valve that controls the amount of heat released from the inlet / outlet 130A of the heat storage tank 130.

[0037] The heat storage operation of the heat storage tank 130 will be explained below using Figure 1. In this mode, valves 200, 210, and 240 are open, while valves 220, 230, and 250 are closed.

[0038] The water a1 (saturated water) output from the outlet 110C of the steam separator 110 and supplied to the inlet 101A of the steam generator 100 undergoes heat exchange with a fluid containing waste heat, and is then output as steam b1 from the outlet 101B.

[0039] Steam b1 is supplied to the inlet 110A of the steam-water separator 110, and water a2 is supplied to the inlet 110B of the steam-water separator 110.

[0040] The steam-water separator 110 contains a mixture of steam b1 and water a2. The water a1 separated from the mixture is output from outlet 110C and supplied to the inlet 101A of the steam generator 100. Meanwhile, the steam b2 (saturated steam) separated from the mixture is output from outlet 110D and supplied to the inlet 120A of the heater 120.

[0041] Steam b2 supplied to the inlet 120A of heater 120 is heated by heater 120 and then becomes steam b3 (superheated steam) which is output from outlet 120B.

[0042] Steam b3 passes through the heat transfer tube 132 inside the heat storage tank 130 from inlet 130A to inlet 130B, thereby transferring heat from the heat transfer tube 132 to the heat storage material 131, and the heat storage material 131 stores heat.

[0043] After the steam b3 exchanges heat with the heat storage material 131 in the heat storage tank 130, it becomes water a3 or steam b4 and is output from the inlet / outlet 130B of the heat storage tank 130 and supplied to the inlet 140A of the water storage tank 140.

[0044] When a mixture of water and steam is contained in the water storage tank 140, the steam is output from outlet 140D, then compressed and reheated by the compressor 160 to become steam b7, which then joins with steam b2. Meanwhile, the water is output from outlet 140E, then supplied to the inlet 110B of the steam-water separator 110 via pump 150 to become water a2.

[0045] During the time period when the solar power generation device is generating electricity (the time period when sunlight is irradiated onto the solar power generation device), the above operation is performed so that heat of, for example, 300°C or more is stored in the heat storage material 131 of the heat storage tank 130.

[0046] Next, the power generation operation of the ORC power generator 170 will be explained using Figure 2. In the mode in which the ORC power generator 170 is generating power, the on-off valves 200, 210, and 240 are closed, and the on-off valves 220 and 230 are open. The on-off valve 250 is opened until the temperature of the steam b5 output from the inlet / outlet 130A of the heat storage tank 130 drops to 300°C if the temperature of the steam b5 is too high to turn the organic medium of the ORC power generator 170 into steam.

[0047] The water a1 (saturated water) output from the outlet 110C of the steam separator 110 and supplied to the inlet 101A of the steam generator 100 undergoes heat exchange with a fluid containing waste heat, and is then output as steam b1 from the outlet 101B.

[0048] Steam b1 is supplied to the inlet 110A of the steam-water separator 110, and water a2 is supplied to the inlet 110B of the steam-water separator 110.

[0049] The steam-water separator 110 contains a mixture of steam b1 and water a2. The water a1 separated from the mixture is output from outlet 110C and supplied to the inlet 101A of the steam generator 100. Meanwhile, the steam b2 (saturated steam) separated from the mixture is output from outlet 110D and supplied to the inlet / outlet 130B of the heat storage tank 130.

[0050] When steam b2 is supplied to the inlet / outlet 130B of the heat storage tank 130, steam b5, adjusted to, for example, 300°C by opening and closing the on / off valve 250, is supplied to the inlet 170A of the ORC power generation device 170. As a result, in the ORC power generation device 170, the organic medium undergoes heat exchange with steam b5 to become steam, and this steam is used to generate electricity. The ORC power generation device 170 generates electricity, for example, during nighttime hours when the solar power generation device cannot generate electricity.

[0051] After heat exchange with the organic medium, the steam b5 becomes water a4, which is output from outlet 170B and supplied to the inlet 140B of the water storage tank 140.

[0052] The water in the storage tank 140 is output from the outlet 140E and then supplied as water a2 to the inlet 110B of the brackish water separator 110 via the pump 150.

[0053] In this way, the ORC power generation device 170 can generate electricity by utilizing the heat storage temperature of the heat storage tank 130.

[0054] As described above, the power generation system 1 includes a generating device (steam generator 100, steam-water separator 110, heater 120, water storage tank 140) that generates steam b3 at a temperature higher than the waste heat using a fluid (gas, liquid) with relatively low temperature (e.g., 100-200°C) waste heat discharged from a power plant or factory, and the electricity generated by a solar power generation device; a heat storage tank 130 that stores heat using the steam b3; and an ORC power generation device 170 that generates electricity using steam b5 obtained based on the heat storage temperature of the heat storage tank 130.

[0055] According to power generation system 1, it becomes possible to generate electricity by effectively utilizing relatively low-temperature waste heat.

[0056] Furthermore, in power generation system 1, the power generated by the solar power generation device supplied as the power source for the heater 120 is surplus power from the solar power generation device that is not consumed by the owner of the solar power generation device and is not sold to consumers or the like in the electricity trading market.

[0057] According to the power generation system, the ORC power generation device 170 can effectively utilize surplus electricity from the solar power generation device to generate electricity.

[0058] Furthermore, in the power generation system 1, the generation of steam b3 by the above-mentioned generating device and the storage of heat by the heat storage tank 130 are performed during the time of day when the solar power generation device can generate electricity (for example, during the daytime), while the ORC power generation device 170 generates electricity during the time of day when the solar power generation device cannot generate electricity (for example, at night).

[0059] According to power generation system 1, at night when the solar power generation equipment is unable to generate electricity, it becomes possible to sell the electricity generated by the ORC power generation equipment 170 at a relatively high price, for example, through the electricity trading market.

[0060] Furthermore, the heat storage tank 130 that constitutes the power generation system 1 includes a heat storage material 131 and a heat transfer tube 132 that transfers heat to the heat storage material 131 inside the heat storage tank 130. The heat transfer tube 132 is structured to take in steam b3 during the daytime when the solar power generation device is generating electricity, for example, and to take out steam b5 from the heat transfer tube 132 during the nighttime when the solar power generation device is not generating electricity.

[0061] This embodiment is intended to facilitate understanding of the present invention and is not intended to limit its interpretation. The present invention can be modified and improved without departing from its spirit, and equivalents thereof are also included. In this embodiment, a metal pipe 190 is used as the piping through which steam and water pass, but the invention is not limited thereto. For example, a predetermined non-metallic pipe capable of maintaining the pressure, temperature, and specific enthalpy of steam and water, similar to the case of the metal pipe 190, may be used. Also, in this embodiment, steam obtained by evaporating water is used as the medium for evaporating the organic medium of the ORC power generation device 170, but the invention is not limited thereto. For example, a heat transfer oil such as Barreltherm (e.g., Barreltherm 200) may be used. Furthermore, in this embodiment, the ORC power generation device 170 is used, but the invention is not limited thereto. Other power generation devices that generate electricity using a medium having a low evaporation temperature, similar to the organic medium of the ORC power generation device 170, may also be used. [Explanation of Symbols]

[0062] 1. Power generation system 100 Steam Generator 101,102,121,171,190A~190K Metal tube 101A,102A,110A,110B,120A,140A,140B,140C,170A Entrance 101B,102B,110C,110D,120B,140D,140E,170B Exit 110 Brackish water separator 120 Heater 130 Heat storage tank 131 Heat storage material 132 Heat transfer tubes 130A,130B entrance / exit 140 Water storage tanks 150 pumps 160 Compressor 170 ORC power generator 180 Check valve 200, 210, 220, 230, 240, 250 Shut-off valves

Claims

1. A generating device that generates steam at a first temperature higher than the waste heat, using a fluid having a predetermined waste heat and the power generated by a first power generation device that utilizes renewable energy, A heat storage device that stores heat using steam at the first temperature, A second power generation device that generates electricity using steam at a second temperature obtained based on the heat storage temperature of the heat storage device, A power generation system including a power generation system.

2. A power generation system according to claim 1, The first power generation device generates electricity using solar energy as the renewable energy source. The power generated by the first power generation device includes surplus power from the power generated by the first power generation device that is not used or sold. Power generation system.

3. A power generation system according to claim 2, The generation of steam at the first temperature by the generating device and the heat storage device performing heat storage are performed during a first time period in a day in which the first power generation device is capable of generating electricity. The second power generation device generates electricity during a second time period of the day when the first power generation device is unable to generate electricity. Power generation system.

4. A power generation system according to claim 3, The aforementioned heat storage device is The heat storage device includes a heat storage material and a heat transfer tube that transfers heat to the heat storage material. Steam at the first temperature is taken into the heat transfer tube during the first time period. Steam at the second temperature is extracted from the heat transfer tube during the second time period. Power generation system.

5. A power generation system according to claim 1, The second power generation device includes a device that generates electricity using steam of an organic medium. Power generation system.

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