JP5586178B2 - Fuel cell cogeneration system - Google Patents

Description

  The present invention relates to a fuel cell cogeneration system that improves the recovery efficiency of exhaust heat accompanying power generation.

  A household fuel cell cogeneration system is a system that collects exhaust heat generated during power generation and uses it for hot water supply while generating power in a fuel cell using city gas or LP gas as fuel. In a home where such a fuel cell cogeneration system is installed, it is possible to suppress the amount of power used from the commercial power system and the amount of hot water supplied from the hot water boiler. That is, it is possible to reduce the amount of primary energy consumed at home and obtain an energy saving effect.

  Here, the outline of the fuel cell cogeneration system will be described with reference to FIG. FIG. 4 is a configuration diagram of a general household fuel cell cogeneration system. The fuel cell cogeneration system 1 includes two units: a fuel cell unit 10 mainly composed of a fuel cell main body 103 and a hot water storage unit 11 that stores the heat discharged from the fuel cell main body 103 as hot water and uses hot water. .

  The fuel cell unit 10 includes a device group that contributes to power generation and a device group that recovers exhaust heat associated with power generation. As devices that contribute to power generation, a fuel supply unit 101, a reforming unit 102, a fuel cell main body 103, an air supply unit 104, an inverter 105, and a cooling water supply unit 107 are provided.

  The fuel supply unit 101 is a part that supplies fuel such as city gas or LP gas to the reforming unit 102. The reforming means 102 is a part that processes the fuel into a hydrogen-rich reformed gas, and supplies the reformed gas to the fuel cell main body 103. The air supply means 104 supplies air in the atmosphere to the fuel cell body 103 as an oxidant gas.

  The fuel cell main body 103 takes in the reformed gas and the air, and generates direct current electricity through an electrochemical reaction. The inverter 105 is a part that converts the direct current electricity generated by the fuel cell main body 103 into alternating current electricity, and supplies the alternating current electricity together with the commercial power system to the power load 106 in the home where the system is installed. Further, since the fuel cell main body 103 generates heat as power is generated, the cooling water supply means 107 cools the fuel cell main body 103 by supplying the fuel cell cooling water to the fuel cell main body 103.

  In the fuel cell unit 10, two heat exchangers, ie, exhaust gas heat recovery means 110 and cooling water heat recovery means 112, are the main parts of the apparatus that recovers the exhaust heat accompanying the power generation of the fuel cell main body 103 from the fuel cell main body 103. In addition, there are exhaust heat recovery water supply means 109, hot water temperature measurement means 113, and plant control device 115. Among these, the exhaust heat recovery water supply means 109 is a part that receives the exhaust heat recovery water supplied from the hot water storage unit 11 side and sequentially supplies it to the heat recovery means 110 and 112.

  The exhaust gas heat recovery means 110 is supplied with exhaust heat recovery water from the exhaust heat recovery water supply means 109 and fuel cell exhaust gas from the fuel cell main body 103. The exhaust gas heat recovery means 110 is a condensing heat exchanger, and recovers the thermal energy of the fuel cell exhaust gas into the exhaust heat recovery water by cooling the fuel cell exhaust gas using the exhaust heat recovery water as a cooling medium. Further, the exhaust gas heat recovery means 110 exhausts the exhaust gas after cooling to the outside of the fuel cell unit 10.

  On the other hand, the cooling water heat recovery means 112 is the same as the exhaust gas heat recovery means 110 in that the exhaust heat recovery water is used as a cooling medium, but the object to be cooled is the fuel cell cooling water. That is, the cooling water heat recovery means 112 recovers the thermal energy of the fuel cell cooling water to the exhaust heat recovery water by cooling the fuel cell cooling water with the exhaust heat recovery water. The fuel cell cooling water cooled by heat exchange with the exhaust heat recovery water exits the cooling water heat recovery means 112 and then returns to the cooling water supply means 107 again.

  As described above, the exhaust heat recovery water that has passed through the heat recovery means 110 and 112 is used for hot water supply that is stored in the hot water storage unit 11 side due to the recovery of the exhaust heat from the fuel cell main body 103 to increase the water temperature. It becomes warm water.

  The hot water temperature measurement means 113 is a part that measures the temperature of the hot water that has come out of the heat exchange means 112, and transmits the measured value to the plant control device 115. The plant controller 115 outputs a control signal to the exhaust heat recovery water supply means 109 so that the measured value of the hot water temperature measurement means 113 becomes a predetermined value, and adjusts the flow rate of the exhaust heat recovery water. Yes.

  More specifically, when the measured value of the hot water temperature measuring means 113 is higher than the target value (the hot water temperature is high), the output of the exhaust heat recovery water supply means 109 is increased to increase the flow rate of the exhaust heat recovery water. As a result, the cooling performance of the heat recovery means 110 and 112 is increased, and the temperature of the hot water is decreased.

  Conversely, when the measured value of the hot water temperature measuring means 113 is lower than the target value (the hot water temperature is low), the output of the exhaust heat recovery water supply means 109 is lowered to reduce the flow rate of the exhaust heat recovery water. As a result, the cooling performance of the heat recovery means 110 and 112 is lowered and the temperature of the hot water is raised. By performing such flow rate adjustment, the hot water is maintained at a predetermined temperature.

  The hot water storage unit 11 has a hot water storage tank 108 for storing the exhaust heat recovery water supplied from the cooling water heat recovery means 112. The hot water storage tank 108 increases the temperature by sending the internal waste heat recovery water to the exhaust heat recovery water supply means 109 on the fuel cell unit 10 side and recovering heat by the heat recovery means 110 and 112. . The hot water storage tank 108 supplies the stored hot water to the hot water supply load 114 of the household where the system is installed.

  In the fuel cell cogeneration system having the above-described configuration, improvement in operation efficiency is required in order to enhance the energy saving effect. The improvement of the operation efficiency is realized by extracting more electricity and recovering more heat from a certain amount of fuel supplied to the fuel cell unit 10.

  With regard to efficient electricity extraction, efforts have been made to improve the performance of the fuel cell main body 103, improve the efficiency of the inverter 105, reduce the power of auxiliary equipment, and the like. In addition, regarding efficient heat recovery, it is effective to reduce the enthalpy of exhaust gas exhausted from the fuel cell unit 10, which not only reduces heat dissipation from individual devices and pipes, but also recovers exhaust gas heat. It is desired to reduce the temperature of the exhaust gas discharged from the means 110 as much as possible.

  By the way, as a household cogeneration system in which an energy-saving effect is expected, a solar power generation apparatus using a solar cell is attracting attention in addition to a system using a fuel cell. A solar power generation device is a device that converts a part of solar energy that has not been conventionally used into electric energy by a solar panel and supplies the electric power to an installed home.

  However, it is known that the power generation efficiency of the solar power generation apparatus decreases in proportion to the temperature increase of the solar panel. Therefore, in summer, although the amount of sunlight was large, the power generation efficiency was reduced due to the temperature rise. Therefore, in the solar power generation device, it is necessary to cool the solar panel and suppress the temperature rise.

  At this time, it is possible to construct a solar power generation apparatus as a cogeneration system using a combined heat and power system by collecting and using the thermal energy released by the solar panel. For example, the technology described in Patent Document 1 aims to improve power generation efficiency by cooling a solar panel with water, and at the same time, absorbs heat energy emitted from the solar panel and changes the water into hot water, which is used as a hot water storage tank. It is stored and supplied to household hot water supply loads. In addition, as a technique related to the solar power generation apparatus, a battery panel with improved cooling performance has been proposed (for example, Patent Document 2).

JP 2000-179948 A JP 2000-54174 A

  As described above, the fuel cell cogeneration system is required to improve the efficiency of heat recovery in order to improve the operation efficiency. Therefore, in the fuel cell unit 10, it is desired to reduce the exhaust gas temperature from the exhaust gas heat recovery means 110 as much as possible to reduce the energy loss. The easiest way to reduce the exhaust gas temperature from the exhaust gas heat recovery means 110 is to enlarge the exhaust gas heat recovery means 110 that is a condensation heat exchanger.

  However, the increase in the size of the exhaust gas heat recovery means 110 has caused problems such as an increase in the size and cost of the entire system. These problems may become an obstacle to the spread of household fuel cell cogeneration systems. Therefore, there is a need for a technique for reducing the temperature of exhaust gas from the fuel cell unit 10 and reducing energy loss with a simple and inexpensive configuration without increasing the size of the condensation heat exchanger constituting the exhaust gas heat recovery means 110. It was done.

  However, in the cogeneration system using the solar power generation device represented by the above-mentioned Patent Document 1, the thermal energy that can be extracted from the system is low. Therefore, even if the thermal energy generated by the photovoltaic power generator is recovered, the hot water supply temperature is low. When considering the heat demand for home use, the hot water supply in the medium temperature range is not very useful. Therefore, the temperature is insufficient as hot water used at home.

  The present invention has been proposed in order to solve the above problems, and it is possible to reduce the exhaust gas temperature by a simple and inexpensive configuration, while avoiding the enlargement of the condensation heat exchanger for cooling the fuel cell exhaust gas. An object of the present invention is to provide a fuel cell cogeneration system that can reduce exhaust gas temperature, thereby improving heat recovery efficiency and contributing to high-efficiency operation.

In order to achieve the above object, a fuel cell cogeneration system according to the present invention includes a fuel cell unit and a heat storage unit that stores exhaust heat from the fuel cell unit, and the fuel cell unit is supplied with fuel. A fuel cell main body that generates power and discharges fuel cell exhaust gas, exhaust gas heat recovery means that recovers heat of the fuel cell exhaust gas into exhaust heat recovery water, and supplies the exhaust heat recovery water to the exhaust gas heat recovery means Waste heat recovery water supply means is provided, and further, fluid is supplied from the outside of the fuel cell unit to the downstream side of the exhaust gas heat recovery means as viewed from the exhaust heat recovery water supply means , and the fluid is configured heat exchange means to provide heat is installed in the exhaust heat recovery water, the downstream of the heat exchange means as viewed from the exhaust heat recovery water supply means, temperature of the exhaust heat recovery water Temperature measuring means for measuring the installation, as the measured value of the temperature measuring means reaches a predetermined value, is characterized in that for controlling the exhaust heat recovery water supply means.

  According to the fuel cell cogeneration system of the present invention, the exhaust heat recovery water is provided by a simple configuration including heat exchange means for recovering the heat energy of the fluid supplied from the outside of the fuel cell unit to the exhaust heat recovery water. The amount of exhaust heat recovery water can be increased by increasing the heat energy, which can improve the cooling performance of the exhaust gas heat recovery means that cools the fuel cell exhaust gas and improve the heat recovery efficiency. It is possible to contribute to high-efficiency operation.

1 is a configuration diagram of a first embodiment according to the present invention. The block diagram of 2nd Embodiment which concerns on this invention. The block diagram of other embodiment of this invention. The block diagram of the conventional fuel cell cogeneration system.

(1) First embodiment (configuration)
Hereinafter, an example of an embodiment according to the fuel cell cogeneration system of the present invention will be specifically described with reference to FIG. The fuel cell cogeneration system 1 shown in FIG. 1 is an improvement to the device group contributing to exhaust heat recovery, and the device group contributing to power generation is the same as the conventional example shown in FIG. Therefore, in FIG. 1, illustration of the device group contributing to power generation in the fuel cell unit 10 is omitted. In addition, regarding the device group contributing to the exhaust heat recovery, the same members are denoted by the same reference numerals and description thereof is omitted.

  A structural feature of the first embodiment is that an external fluid heat recovery means 111 is installed downstream of the exhaust gas heat recovery means 110 when viewed from the exhaust heat recovery water supply means 109. An external device independent of the fuel cell unit 10 is connected to the external fluid heat recovery means 111.

  The external fluid heat recovery means 111 is supplied with exhaust heat recovery water from the exhaust heat recovery water supply means 109, and is supplied with a fluid that gives heat to the exhaust heat recovery water from an external device. That is, the external fluid heat recovery means 111 is a heat exchange means for performing heat exchange between the external fluid and the exhaust heat recovery water.

  Here, as an external device connected to the external fluid heat recovery means 111, a solar power generation device 201 that generates power using solar energy is employed. The state in which the solar power generation device 201 that is an external device is independent from the fuel cell unit 10 means that the thermal energy from the solar power generation device 201 and the thermal energy derived from the fuel supplied to the fuel cell unit 10 are Indicates a state that does not affect each other.

  The solar power generation apparatus 201 is provided with a solar panel 206, and a PV cooling means 202 for cooling the solar panel 206 is attached to the solar panel 206. Further, the PV cooling means 202 is provided with a PV coolant supply means 203 that circulates and supplies a PV coolant (for example, water) to the PV cooling means 202. The PV coolant supply unit 203 is connected to the external fluid heat recovery unit 111. That is, the PV coolant on the photovoltaic power generation apparatus 201 side is an external fluid that gives heat to the exhaust heat recovery water of the fuel cell cogeneration system 1.

(Function)
In the first embodiment having the above configuration, the external fluid heat recovery means 111 performs heat exchange between the PV coolant and the exhaust heat recovery water. At this time, the external fluid heat recovery means 111 heats the exhaust heat recovery water simultaneously with cooling the PV coolant. Compared with the conventional example shown in FIG. 4 that has passed through two heat exchangers, the amount of exhaust heat recovery increased by the amount of exhaust heat recovery water that has passed through the external fluid heat recovery means 111. For this reason, the temperature of the waste heat recovery water rises and the measured value of the hot water temperature measuring means 113 becomes high.

  When the measured value of the hot water temperature measuring means 113 becomes high, the output of the exhaust heat recovery water supply means 109 is increased in response to the control signal of the plant control device 115, and the flow rate of the exhaust heat recovery water as a cooling medium increases. As described above, the exhaust heat recovery water flow rate by the exhaust heat recovery water supply means 109 is increased, and the following control of the virtuous circulation works.

  If the flow rate of the exhaust heat recovery water increases, the heat recovery amount in the exhaust heat gas recovery means 110 increases. Due to the increase in the heat recovery amount, the temperature of the exhaust heat recovery water rises and the measured value of the hot water temperature measuring means 113 becomes higher. As a result, the plant controller 115 is controlled in the direction of increasing the flow rate of the exhaust heat recovery water so as to make the measurement value of the hot water temperature measuring means 113 constant. Thereby, it becomes virtue circulation control that the amount of heat recovery in the exhaust heat gas recovery means 110 further increases.

(effect)
According to the first embodiment, the following three effects can be obtained. First, in the exhaust gas heat recovery means 110 in which the flow rate of the exhaust heat recovery water is increased, the cooling performance is improved, so that the exhaust gas temperature from the fuel cell unit 10 can be reduced. Therefore, the fuel cell cogeneration system 1 can be operated with high efficiency and less energy loss.

  Moreover, since the heat energy recovered by the external fluid heat recovery means 111 is external heat energy not derived from the fuel supplied to the fuel cell main body 103, exhaust gas heat recovery without increasing the size of the exhaust gas heat recovery means 110 itself. The heat exchange performance of the means 110 can be enhanced. Therefore, the fuel cell cogeneration system 1 can be made compact and the heat recovery efficiency can be improved.

  Second, the heat exchange amount itself of the PV coolant and the exhaust heat recovery water is small, and even if the thermal energy that can be extracted from the solar power generation apparatus 201 is low, the thermal energy recovered by the external fluid heat recovery means 111 is used as the fuel cell. The exhaust heat recovery water flowing in the cogeneration system 1 can be collected intensively.

  As a result, in the cogeneration system using only the thermal energy of the solar power generation apparatus 201, only medium-temperature water having a low utility value was obtained, but in this embodiment, hot water having a high utility value is finally stored. It becomes possible to supply the unit 11 stably.

  Third, the external fluid heat recovery means 111 cools the PV coolant by heat exchange with the exhaust heat recovery water. For this reason, the PV cooling means 202 can cool the solar power generation device 201 efficiently with a low-temperature PV coolant. Therefore, the solar power generation device 201 can obtain good power generation efficiency.

(2) Second embodiment (configuration)
In the fuel cell cogeneration system according to the present invention, the configuration of the second embodiment will be described with reference to FIG. In addition, the common part of FIG. 1 and FIG. 2 is not illustrated. In 2nd Embodiment, the 1st temperature measurement means 204 for measuring the temperature of the PV coolant which cooled the solar power generation device 201 is provided, and the flow-path switching means 205 is installed in the downstream.

  The flow path switching means 205 receives the control signal from the plant control device 115, bypasses the flow path of the PV coolant toward the external fluid heat recovery means 111, or bypasses the external fluid heat recovery means 111, and the PV coolant supply means. The direction is switched to the 203 direction. Further, a second temperature measuring means 120 for measuring the temperature of the exhaust heat recovery water entering the external fluid heat recovery means 111 is installed upstream of the exhaust heat recovery water of the external fluid heat recovery means 111.

(Function)
The first and second temperature measuring means 204 and 120 transmit the PV coolant temperature T1 and the exhaust heat recovery water temperature T2 as measured values to the plant control device 115, respectively. If the PV coolant temperature T <b> 1 measured by the first temperature measuring unit 204 is equal to or lower than the exhaust heat recovery water temperature T <b> 2 measured by the second temperature measuring unit 120, the plant control device 115 sends the flow path switching unit 205. In contrast, a control signal for sending the flow path of the PV coolant to the PV coolant supply means 203 is sent. Accordingly, the external fluid heat recovery means 111 is bypassed by the flow path switching means 205, and the PV coolant is returned to the PV coolant supply means 203 side (arrow A in FIG. 2).

  Further, if the PV coolant temperature T1 measured by the first temperature measuring means 204 is higher than the exhaust heat recovery water temperature T2 measured by the second temperature measuring means 120, the plant control device 115 determines that the flow path switching means. A control signal is sent to 205 so that the flow path of the PV coolant is directed to the external fluid heat recovery means 111. Therefore, the flow path switching unit 205 causes the PV coolant to flow toward the external fluid heat recovery unit 111 (arrow B in FIG. 2). As a result, it is possible to contribute to heat exchange in the external fluid heat recovery means 111.

(effect)
According to the second embodiment having the above-described configuration, in the external fluid heat recovery means 111, T1 and T2 which are the temperatures of the PV coolant and the exhaust heat recovery water are the same, or the PV coolant temperature T1 is the same. Is lower than the exhaust heat recovery water temperature T2, the PV coolant does not become a heating medium for the exhaust heat recovery water. For this reason, the PV coolant does not flow to the external fluid heat recovery means 111. Therefore, there is no fear that the temperature of the PV coolant rises due to heat exchange with the exhaust heat recovery water, and there is no possibility that the power generation efficiency of the solar power generation apparatus 201 will decrease.

(3) Other Embodiments The above embodiments are specific examples for carrying out the present invention, and do not limit the scope of the invention in any way. For example, in order to obtain the operational effects of the first embodiment, it is important that external energy not derived from the fuel supplied to the fuel cell unit is included in the heat source of the external fluid heat recovery means 111. In addition, the heating fluid for the exhaust heat recovery water may be, for example, remaining hot water in a bath at the installation home (see FIG. 3).

  In the embodiment shown in FIG. 3, instead of the solar power generation apparatus 201, a remaining hot water supply unit 303 that supplies the remaining hot water of the bath 301 to the external fluid heat recovery unit 111 is provided. That is, the remaining hot water in the bath 301 becomes an external fluid that gives heat to the exhaust heat recovery water side. The remaining hot water supply means 303 is connected to third temperature measuring means 304 for measuring the temperature T3 of the remaining hot water.

  In this embodiment, only when the temperature T3 of the remaining hot water measured by the third temperature measuring unit 304 is higher than the exhaust heat recovery water temperature T2 measured by the second temperature measuring unit 120, the plant controller 115 Under the control, the remaining hot water supply means 303 is operated to flow the remaining hot water toward the external fluid heat recovery means 111 (arrow C in FIG. 3).

  Therefore, in the external fluid heat recovery means 111, heat exchange between the remaining hot water of the bath 301 and the exhaust heat recovery water is performed. Note that if the remaining hot water temperature T3 is equal to or lower than the exhaust heat recovery water temperature T2, the remaining hot water supply means 303 does not operate. According to such an embodiment, the same operational effects as those of the second embodiment can be obtained.

  Moreover, it is not essential to include the electromotive force by the solar power generation device 201 in the fuel cell cogeneration system 1. That is, the solar power generation device 201 may not generate power. Furthermore, in the second embodiment, the flow path of the PV coolant is switched by one flow path switching valve 205, but the flow path of the PV coolant may be switched using a plurality of shutoff valves. In addition, although the water is utilized as a PV coolant, if it is a cooling medium, the kind can be selected freely.

  The purpose of bypassing the external fluid heat recovery means 111 to the PV coolant is to prevent the PV coolant having a temperature lower than that of the exhaust heat recovery water from flowing to the external fluid heat recovery means 111 side. Therefore, when the temperature of the solar power generation apparatus 201 is directly measured and the temperature does not reach a predetermined temperature such as in winter, the PV coolant supply unit 203 is not necessary to measure the temperature of the exhaust heat recovery water. It is good also as a structure to stop.

  In addition, in the above embodiments, it is assumed that a reforming means for extracting hydrogen-rich gas from city gas or LP gas is provided. However, the present invention is not limited to this, and it is originally an industrial by-product. It may be applied to a fuel cell power generation system that uses a gas containing hydrogen or pure hydrogen gas as a fuel and has no reforming means.

DESCRIPTION OF SYMBOLS 1 ... Fuel cell cogeneration system 10 ... Fuel cell unit 11 ... Hot water storage unit 101 ... Fuel supply means 102 ... Reforming means 103 ... Fuel cell main body 104 ... Air supply means 105 ... Inverter 106 ... Electric power load 107 ... Cooling water supply means 108 ... hot water storage tank 109 ... exhaust heat recovery water supply means 110 ... exhaust gas heat recovery means 111 ... external fluid heat recovery means 112 ... cooling water heat recovery means 113 ... hot water temperature measurement means 114 ... hot water supply load 115 ... plant control device 120 ... second Temperature measuring means 201 ... photovoltaic power generator 202 ... PV cooling means 203 ... PV coolant supply means 204 ... first temperature measuring means 205 ... flow path switching means 206 ... solar panel 301 ... bath 303 ... remaining hot water supply means 304 ... Third temperature measuring means T1 ... PV coolant temperature T2 ... Waste heat recovery water temperature T3 ... Temperature of remaining hot water

Claims (5)

It is composed of a fuel cell unit and a heat storage unit that stores exhaust heat from the fuel cell unit,
The fuel cell unit includes a fuel cell main body that generates power by supplying fuel and discharges fuel cell exhaust gas, exhaust gas heat recovery means that recovers heat of the fuel cell exhaust gas into exhaust heat recovery water, and the exhaust heat Exhaust heat recovery water supply means for supplying recovered water to the exhaust gas heat recovery means is provided,
Furthermore, the downstream side of the exhaust gas heat recovery unit when viewed from the exhaust heat recovery water supply means, the fuel cell unit fluid from the external are supplied, configured such that the fluid provides heat to the exhaust heat recovery water thermal exchange means been installed,
A temperature measuring means for measuring the temperature of the exhaust heat recovery water is installed on the downstream side of the heat exchange means as viewed from the exhaust heat recovery water supply means,
The fuel cell cogeneration system , wherein the exhaust heat recovery water supply means is controlled so that the measured value of the temperature measurement means becomes a predetermined value .   The fuel cell cogeneration system according to claim 1, further comprising a fluid supply pipe for supplying the external fluid to the heat exchange means. A solar power generation device independent of the fuel cell cogeneration system is provided outside the fuel cell unit,
The fuel cell cogeneration system according to claim 2, wherein a PV coolant for cooling the solar power generation device is used as the external fluid.   The fuel cell cogeneration system according to claim 1 or 2, wherein a remaining hot water of a bath is used as the external fluid. First temperature measuring means for measuring the exhaust heat recovery water when supplied to the external fluid heat recovery means, and second temperature measuring means for measuring the temperature of the external fluid are provided,
Based on the measured values of the first and second temperature measuring means, the external fluid is supplied to the external fluid heat recovery means only when the external fluid temperature exceeds the exhaust heat recovery water temperature. The fuel cell cogeneration system according to any one of claims 1 to 4.

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