JP2014138522A - Power generation system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power generation system using solar heat which stably and highly efficiently generates power.SOLUTION: A power generation system includes: a thermoelectric generation unit which exchanges heat between a heat medium flowing in a high temperature side loop and a fluid having temperature lower than that of the heat medium and flowing in a low temperature side loop to perform thermoelectric generation on the basis of the temperature difference between the heat medium and the fluid; a heat collecting device which is provided in the high temperature side loop and collects solar heat to heat the heat medium; a biomass boiler which is provided in the high temperature side loop and burns a biomass fuel to heat the heat medium; a heat storage tank which is provided in the high temperature side loop and stores heat of the heat medium heated by at least one of the heat collecting device and the biomass boiler into the ground; and a binary power generation unit which is provided in the low temperature side loop and uses the heat of the fluid whose heat is exchanged with the heat medium by the thermoelectric generation unit to perform binary power generation.

Description

  The present invention relates to a power generation system that uses solar heat, and more particularly, to a combined power generation system that combines power generation that converts solar heat into electrical energy using a thermoelectric conversion element and binary power generation.

  In recent years, power generation systems using solar energy have attracted attention from the viewpoint of energy saving and earth protection. Solar energy is inexhaustible as a resource, and has the great advantage that it does not emit harmful air pollutants and carbon dioxide that causes global warming when converting its energy. There are two types of power generation systems using solar energy: solar power generation and solar thermal power generation. Among them, solar power generation is a method of irradiating sunlight on an element having an internal electric field such as a semiconductor pn junction and obtaining electric energy by using the obtained photovoltaic power, and is generally called a solar cell. It is.

  On the other hand, solar thermal power generation stores solar energy as heat and uses this to generate power, and several methods are known. One of them is to collect solar heat with a reflecting mirror, circulate the heat medium and rotate the turbine to generate electricity.

  Another method of solar thermal power generation is to generate power by thermoelectric conversion using a thermoelectric conversion element having Seebeck effect using solar heat as a heat source. Solar heat is collected by the reflector through the thermoelectric conversion element, and heat exchange is performed between the heat medium heated by the solar heat and the refrigerant. At this time, the heat of the heat medium is converted into electric energy by the Seebeck effect, and electric power is generated. (See Patent Documents 1 to 4). The power generation using this thermoelectric conversion element is characterized in that the amount of power generation increases as the temperature difference increases.

JP 2011-87416 A JP 2010-11718 A JP 2007-81097 A Japanese Patent Laid-Open No. 2001-7412

  Like solar power generation, solar thermal power generation is difficult to perform stable power generation because the amount of solar radiation varies depending on the weather and power generation cannot be performed at night. Solar thermal power generation using turbine rotation requires large-scale facilities and is suitable for large-scale power generation, but is difficult to implement in relatively small-scale applications.

  On the other hand, solar thermal power generation using a thermoelectric conversion element does not have a mechanical drive unit such as a turbine and can perform power generation at low cost and high reliability. However, the thermoelectric conversion efficiency of the thermoelectric conversion element is relatively low. It is low (about 3%), and sufficient power generation cannot be obtained.

  Therefore, an object of the present invention is to provide a power generation system that stably and efficiently generates power in a power generation system using solar heat.

  In order to achieve the above object, the configuration of the power generation system of the present invention is configured to cause heat exchange between a heat medium flowing through a high temperature side loop and a fluid flowing through a low temperature side loop having a temperature lower than that of the heat medium, so that a temperature difference between the heat medium and the fluid is achieved. A first power generation unit (thermoelectric power generation unit) for thermoelectric power generation, a first heating device (solar heat collection device) that collects solar heat and heats the heat medium, and a high temperature side loop. A second heating device (biomass boiler) that is provided and burns biomass fuel to heat the heat medium and a high temperature side loop that is heated by at least one of the first heating device and the second heating device. A heat storage tank that stores the heat of the heat medium in the ground, and a second power generation unit that is provided in the low temperature side loop and performs binary power generation using the heat of the fluid that exchanges heat with the heat medium in the first power generation unit ( A binary power generation unit) And features.

  According to the power generation system of the present invention, in a power generation system using solar heat, a power generation system that stably and highly efficiently generates power by combining combustion heat from a biomass boiler and further power generation by binary power generation is provided. can do.

It is a figure which shows the structure of the combined power generation system in embodiment of this invention. 2 is a diagram illustrating a schematic configuration example of a heat exchange / power generation unit 100. FIG.

  Embodiments of the present invention will be described below with reference to the drawings. However, such an embodiment does not limit the technical scope of the present invention.

  FIG. 1 is a diagram showing a configuration of a power generation system according to an embodiment of the present invention. In the power generation system of the present embodiment, in heat generation by thermoelectric conversion, in addition to solar thermal energy, combustion heat from a biomass boiler is used as a heat source for heating a high-temperature side heat medium that exchanges heat with a low-temperature side fluid via a thermoelectric conversion element. This is a combination of energy generation and binary power generation that uses the heat of the low-temperature fluid that exchanges heat with the high-temperature side via a thermoelectric conversion element.

  The power generation system of this embodiment includes a thermoelectric power generation unit 100 that performs thermoelectric power generation based on a temperature difference between a high temperature side heat medium and a low temperature side fluid, and a heat medium (for example, mineral oil) on the high temperature side of the thermoelectric power generation unit 100. ) And a low-temperature side unit that circulates fluid (hot water) on the low-temperature side of the thermoelectric power generation unit 100 and performs binary power generation.

  The high temperature side unit includes a heat collecting device 210 that collects solar heat, a biomass boiler 240 that burns biomass fuel, a heat storage tank 220 that stores the collected heat, and a discharge pump 230, and a heat medium circulates. Loop (high temperature side loop) is formed. The heat collector 210 and the biomass boiler 240 are arranged in parallel in the high temperature side loop, and the heat medium heated by the heat collector 210 or the biomass boiler 240 is sent to the heat storage tank 220 to heat and store the heat storage tank 220. The Further, the heat medium passing through the heat storage tank 220 is sent to the thermoelectric power generation unit 100, flows through the high temperature side of the thermoelectric power generation unit 100, exchanges heat with the low temperature side, and then returns to the heat collector 210 or the biomass boiler 240. . A circulation discharge pump 230 circulates the heat medium in the high temperature side loop and supplies the heat medium to the thermoelectric generator 100. An expansion tank for absorbing pressure fluctuations in the heat medium may be provided.

  The low temperature side unit includes a binary power generation unit 310 and a discharge pump 370, and constitutes a loop (low temperature side loop) by a pipe line through which fluid (hot water) circulates. The fluid flowing through the low temperature side loop is exchanged with the high temperature side heat medium on the low temperature side of the thermoelectric power generation unit 100, and then sent to the binary power generation unit 310. The fluid discharged from the binary power generation unit 310 is the thermoelectric power generation. Part 100. A circulation discharge pump 370 circulates the fluid in the low temperature side loop.

  A heat supply device 500 that uses the heat of the fluid discharged from the binary power generation unit 310 as a heat source may be connected to the low temperature side loop of the low temperature side unit. The heat supply apparatus 500 is, for example, a hot water supply apparatus or an air conditioning apparatus, and the power generation system and the heat supply apparatus 500 in the present embodiment constitute a cogeneration system.

  FIG. 2 is a diagram illustrating a schematic configuration example of the thermoelectric power generation unit 100. The thermoelectric power generation unit 100 includes a thermoelectric power generation module 101, a high temperature side heat transfer plate 102, and a low temperature side heat transfer plate 103. The thermoelectric power generation module 101 is an element that generates power by using a temperature difference between a high temperature side and a low temperature side using the Seebeck effect, and an existing product can be adopted. The high temperature side heat transfer plate 102 is provided with a flow path through which the heat medium heated by the high temperature side unit flows, and the low temperature side heat transfer plate 103 is provided with a flow path through which the fluid of the low temperature side unit flows.

  Below is an example of a trial calculation of generated power.

  (1) Operate at least one of the heat collector 210 and the biomass boiler 270 to generate 50 kW of thermal energy and heat the mineral oil flowing through the high temperature side loop.

  If the solar heat can be collected for 8 hours of daytime and daytime out of 24 hours, it is necessary to store heat in the heat storage tank 220 for 16 hours at night (including time zones where sufficient solar heat cannot be obtained, such as morning and evening). The capacity heat storage tank 220 capable of storing the necessary amount of heat is designed.

  When the mineral oil cannot be heated to the design temperature with only the heat collector 210, the biomass boiler 270 is operated.

  (2) When the temperature of the mineral oil in the high temperature side loop is 160 ° C. to 260 ° C. (average value 210 ° C.) and the temperature of the hot water in the low temperature side loop is 20 ° C. to 80 ° C. (average value 50 ° C.), Although the temperature difference on the low temperature side is 160 ° C. (= 210 ° C.-50 ° C.), the temperature difference is set to 100 ° C. in consideration of the loss of thermal resistance.

  (3) The conversion efficiency of the thermoelectric generator module at a temperature difference of 100 ° C. is 3 to 4%, and 1.5 to 2 kW of electric power is obtained for 50 kW of thermal energy generated by the heat collector 210 or the biomass boiler 270. It is done.

  (4) If the hot water temperature of the low-temperature side loop subjected to heat exchange with the thermoelectric conversion module is 70 to 100 ° C. and the power generation by the binary power generation unit 310 can obtain about 3.5 kW, the conversion efficiency in this case is 7 %. Therefore, by the power generation by the thermoelectric power generation unit 100 and the binary power generation unit 310, a total power of 5 kW or more can be obtained for the thermal energy of 50 kW, and a conversion efficiency of 10% or more is achieved.

  The power consumption of the circulation discharge pump is about 10 W, and with this power generation amount, it is possible to cover the entire power for driving the pump.

  The electric power generated by the thermoelectric power generation unit 100 is stored in the power storage device (battery) 400. As the power storage device 400, an appropriate secondary battery corresponding to the application is selected. The power control unit 410 uses the power stored in the power storage device 400 to supply necessary power to each pump. The power control unit 410 can be realized by general computer control. The generated power may be used for operation of power driving elements other than the pump, such as the power control unit 410.

  The heat storage tank 220 is preferably installed in the ground and has a volume corresponding to a necessary heat storage amount. The underground tank is filled with a heat storage material having a high heat storage density such as rock, concrete or brick, and preferably covered with a heat insulating material. The heat medium flowing in the pipe line piped in the heat storage tank 220 performs heat absorption / radiation with the heat storage material. In the underground, there is little temperature change compared to the ground, the heat storage temperature can be kept constant and a large volume can be secured, so a heat storage tank 220 is provided as a large underground facility Thus, a large amount of heat can be stably accumulated. As a result, if sufficient solar radiation can be secured during the day and noon, it will be possible to stably generate all the electric power necessary for the operation of the device throughout the 24 hours including the night time when solar heat cannot be collected. A system that operates autonomously by solar thermal power generation is constructed without receiving external power supply. When a sufficient amount of heat cannot be ensured only by solar heat collection, the biomass boiler 270 is operated, and the amount of heat necessary for the designed power generation amount is secured.

  The heat collector 210 is a so-called heliostat type (a method of concentrating sunlight on a heat collector in a tower installed in the center using a plane mirror and collecting the heat) or a trough type (a curved mirror). And various heat collecting methods including a method of concentrating sunlight on a pipe installed in front of the curved mirror and heating a heat medium flowing in the pipe).

  Biomass boiler 270 is a combustion device that heats a heat medium by burning biomass fuel such as thinned wood, building waste, chip of chips at the time of wood processing, and waste plastic solid fuel (RPF) to obtain thermal energy. When the heat collecting device 210 can obtain a stable amount of heat necessary for heating the heat medium, the biomass boiler 270 need not be operated. For example, when the amount of heat necessary for nighttime power generation continues or when the amount of heat necessary for power generation at night is insufficient with the amount of heat stored in the heat storage layer 220, the necessary amount of heat is compensated. The high temperature side loop can adjust the loop through which the heat medium flows by switching a valve installed in the pipe line, and the loop, the heat collection device 210 or the biomass boiler 270 that flows through both the heat collection device 210 and the biomass boiler 270. It is possible to appropriately switch to a loop that flows through only one of the two.

  The binary power generation unit 310 is a power generation device that heats and vaporizes a working medium having a relatively low boiling point (for example, pentane, chlorofluorocarbon, ammonia, propane gas, etc.) and rotates the turbine with the steam to generate power. Since the working medium having a boiling point lower than that of water is evaporated, the relatively low temperature hot water can be used for power generation. In the present embodiment, the heat of the fluid flowing through the low temperature side loop of the thermoelectric power generation unit 100 is used. It generates electricity.

  In recent years, a small binary power generation device with a maximum output of about 3 kW to 10 kW has been developed, and binary power generation using a relatively low temperature heat (about 70 to 100 ° C.) of a fluid flowing through a low temperature side loop of the thermoelectric power generation unit 100 is possible. It has become.

  The installation position of each pump is not limited to that shown in FIG. 1, but is installed at a position where an appropriate flow of the heat medium flowing through the high temperature side unit and the fluid flowing through the low temperature side unit can be secured. It is determined appropriately according to the ability.

  The present invention is not limited to the above-described embodiment, and there are design changes within a range that does not depart from the gist including various modifications and corrections that can be conceived by those having ordinary knowledge in the field of the present invention. Of course, it is included in the present invention.

  The main technical features of the embodiment described above are as follows.

(Appendix 1)
A first power generation unit for exchanging heat between a heat medium flowing through the high temperature side loop and a fluid flowing through the low temperature side loop having a temperature lower than that of the heat medium, and performing thermoelectric generation by a temperature difference between the heat medium and the fluid;
A first heating device that is provided in the high-temperature side loop and collects solar heat to heat the heat medium;
A second heating device provided in the high temperature side loop for heating the heat medium by burning biomass fuel;
A heat storage tank that is provided in a high temperature side loop and stores heat of the heat medium heated by at least one of the first heating device and the second heating device in the ground;
A power generation system comprising: a second power generation unit that is provided in a low temperature side loop and that performs binary power generation using heat of a fluid that has exchanged heat with a heat medium in the first power generation unit.

(Appendix 2)
In Appendix 1,
A first pump for circulating the heat medium in the high temperature side loop;
A second pump for circulating the fluid in the low temperature side loop,
The power generation system, wherein the first pump and the second pump are driven by electric power generated by the first power generation unit or the second power generation unit.

(Appendix 3)
In Appendix 1 or 2,
The power generation system, wherein the first heating device and the second heating device are provided in parallel to a high temperature side loop.

(Appendix 4)
In Appendix 2,
A power storage device that stores the power generated by the first power generation unit and the second power generation unit;
A power generation system comprising: a power control unit that supplies power stored in the power storage device to the first pump and the second pump.

(Appendix 5)
The power generation system according to appendices 1 to 4,
A cogeneration system comprising: a heat supply device that uses heat of a fluid discharged from the second power generation unit as a heat source.

(Appendix 6)
In Appendix 5,
The cogeneration system, wherein the heat supply device is a cooling / heating device or a hot water supply device.

  100: thermoelectric power generation unit, 210: heat collecting device, 220: heat storage tank, 230: discharge pump, 270: biomass boiler, 310: binary power generation unit, 370: discharge pump, 400: power storage device, 410: power control unit

Claims (1)

A first power generation unit for exchanging heat between a heat medium flowing through the high temperature side loop and a fluid flowing through the low temperature side loop having a temperature lower than that of the heat medium, and performing thermoelectric generation by a temperature difference between the heat medium and the fluid;
A first heating device that is provided in the high-temperature side loop and collects solar heat to heat the heat medium;
A second heating device provided in the high temperature side loop for heating the heat medium by burning biomass fuel;
A heat storage tank that is provided in a high temperature side loop and stores heat of the heat medium heated by at least one of the first heating device and the second heating device in the ground;
A power generation system comprising: a second power generation unit that is provided in a low temperature side loop and that performs binary power generation using heat of a fluid that has exchanged heat with a heat medium in the first power generation unit.

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