Hybrid system

[Object] To provide a hybrid system of which overall efficiency is improved.[Solution] A hybrid system of the invention includes: a fuel cell device; and a thermoacoustic cooler. The thermoacoustic cooler 14 includes: a thermoacoustic energy generating section 20 in which thermoacoustic energy is generated by a temperature gradient between a high-temperature side and a low-temperature side; and a cooling section 21 in which a function of cooling is performed in the low-temperature side using the temperature gradient between the high-temperature side and the low-temperature side which is produced when the thermoacoustic energy transmitted from the thermoacoustic energy generating section 20 is converted into energy. The system is configured to cause exhaust gas emitted from the fuel cell device to flow through the high-temperature side of the thermoacoustic energy generating section 20. Therefore, it is possible to achieve the hybrid system of which overall efficiency is improved.

RELATED APPLICATIONS

The present application is a national stage entry according to 35 U.S.C. §371 of PCT application No.: PCT/JP2013/071438 filed on Aug. 7, 2013, which claims priorities from Japanese application Nos.: 2012-175055 filed on Aug. 7, 2012, 2012-208370 filed on Sep. 21, 2012, 2012-209778 filed on Sep. 24, 2012 and 2012-251325 filed on Nov. 15, 2012, and are incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present invention relates to a hybrid system into which a thermoacoustic cooling machine and a fuel cell device are incorporated.

BACKGROUND ART

In recent years, there have been proposals for various types of fuel cell modules in which a fuel cell that can obtain power using fuel gas (hydrogen-containing gas) and oxygen-containing gas (air), as a next-generation energy source, is accommodated in a container, and various types of fuel cell devices in which the fuel cell module is accommodated in an outer case (for example, see PTL 1).

Currently, regarding a hybrid system which includes such a fuel cell device, there have been proposals for a hybrid system in which water is heated using heat produced through power generation of the fuel cell device, or into which other power generation devices such as a Stirling engine are incorporated, such that overall efficiency is improved (for example, see PTL 2).

Further, in recent years, there have been proposals for a high-temperature producing instrument that focuses on thermoacoustic energy (for example, see PTL 3).

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

As described above, currently, hybrid systems have been proposed, into which a fuel cell device and other systems are incorporated. Although these hybrid systems are assumed to be used appropriately in accordance with an application environment, there is still room for improvement in terms of the overall efficiency.

The present invention aims to provide a hybrid system that is useful particularly for a commercial facility such as a convenience store or a supermarket as the application environment.

Solution to Problem

The present invention provides a hybrid system including: a fuel cell device; and a thermoacoustic cooler. The thermoacoustic cooler includes a thermoacoustic energy generating section in which thermoacoustic energy is generated by a temperature gradient between a high-temperature side and a low-temperature side and a cooling section in which a function of cooling is performed in the low-temperature side using the temperature gradient between the high-temperature side and the low-temperature side which is produced when the thermoacoustic energy transmitted from the thermoacoustic energy generating section is converted into energy. Exhaust gas emitted from the fuel cell device flows through the high-temperature side of the thermoacoustic energy generating section.

Advantageous Effects of Invention

According to the present invention, since the hybrid system has a configuration in which the exhaust gas emitted from the fuel cell device flows through the high-temperature side of the thermoacoustic energy generating section, a sound wave can be generated efficiently in the thermoacoustic energy generating section. Accordingly, the thermoacoustic cooler, in which the function of cooling can be reinforced in the cooling section, and the fuel cell device are incorporated into the hybrid system such that the hybrid system is useful particularly for a commercial facility such as a convenience store or a supermarket which requires power supply, cold storage, and freezing.

DESCRIPTION OF EMBODIMENTS

FIG. 1is a diagram illustrating an example of a configuration of a hybrid system according to the present embodiment.

The hybrid system illustrated inFIG. 1includes a power generating unit which corresponds to an example of a fuel cell device, and a thermoacoustic cooler that generates thermoacoustic energy using exhaust gas emitted from the power generating unit and performs cooling (freezing) using the generated thermoacoustic energy. The same reference numbers are attached to the same members in the following drawings.

The power generating unit illustrated inFIG. 1includes a cell stack2that has a plurality of fuel cells, fuel source feeding means4that feeds a fuel source such as town gas, oxygen-containing gas feeding means5for feeding an oxygen-containing gas to the fuel cells that configure the cell stack2, and a reformer3that performs steam reforming of the fuel source using the fuel source and water vapor. Although described later, a fuel cell module1(hereinafter, abbreviated to module1in some cases) is configured to accommodate the cell stack2and the reformer3in a container and is illustrated by being surrounded by a two-dot chain line inFIG. 1. Although not illustrated inFIG. 1, an ignition device for burning a fuel gas that is not used in power generation is provided in the module1.

In addition, the power generating unit illustrated inFIG. 1includes a heat exchanger6that performs heat exchange for exhaust gas (exhaust heat) produced through power generation from the fuel cells that configure the cell stack2and thus lowers the temperature of the exhaust gas. The heat exchanger6includes a condensed water processing device7for processing condensed water obtained by condensing moisture contained in the exhaust gas into pure water and a water tank8for storing the processed water (pure water) in the condensed water processing device7. The water tank8and the heat exchanger6are connected by a condensed water feeding pipe9. According to water quality of the condensed water produced through heat exchange by the heat exchanger6, it is possible to employ a configuration in which the condensed water processing device7is not provided. Further, in a case where the condensed water processing device7has a function of storing water, it is possible to employ a configuration in which the water tank8is not provided.

Water stored in the water tank8is fed to the reformer3by a water pump11provided on a water feeding pipe10to which the water tank8and the reformer3are connected.

Further, the power generating unit illustrated inFIG. 1includes a power supply adjusting unit (power conditioner)12that converts DC power generated in the module1into AC power and adjusts a supply rate of the converted electricity to an external load and a controller13that controls operations of various elements. The elements that configure the power generating unit are accommodated in an outer case and thereby it is possible to achieve the fuel cell device of which installation, transporting, or the like is easily performed.

Subsequently, a thermoacoustic cooler14is described. The thermoacoustic cooler14is configured to have a motor15, a cooler16, and a connection pipe17that connects the motor15and the cooler16. The motor15, the cooler16, and the connection pipe17are filled with a gas such as helium gas. In addition, heat accumulators18and19are disposed in the motor15and the cooler16, respectively. One side of the heat accumulator18of the motor15is high in temperature (upper side inFIG. 1) and the other side thereof is low in temperature (lower side inFIG. 1), which results in a temperature gradient that causes thermoacoustic energy (sound waves) to be generated. Accordingly, there are provided a high-temperature side flow path20A through which a high-temperature fluid for heating one side of the heat accumulator18flows and a low-temperature side flow path20B through which a low-temperature fluid for cooling the other side thereof flows. The thermoacoustic energy generating section20is configured to include the heat accumulator18, the high-temperature side flow path, and the low-temperature side flow path. In addition, inFIG. 1, the high-temperature side flow path20A, the low-temperature side flow path20B, and the heat accumulator18as the thermoacoustic energy generating section20are collectively surrounded by a dotted line.

The thermoacoustic energy generated in the thermoacoustic energy generating section20resonates when flowing through the motor15and the connection pipe17and the thermoacoustic energy is transmitted to the cooler16. The energy of the thermoacoustic energy is converted into heat energy in the cooler16. A flow path21A through which the fluid flows is provided on the high-temperature side (upper side inFIG. 1) which corresponds to one side of the heat accumulator19. Thus, on the other side (lower side inFIG. 1) of the heat accumulator19an endothermic reaction occurs and causes the temperature to be lowered and, thereby, a cooling function is performed. That is, a cooling section21is configured to include the heat accumulator19, the flow path21A which corresponds to the high-temperature side, and a portion21B which corresponds to the low-temperature side. In the cooling section21, the flow path21A means a flow path through which a high-temperature fluid flows when compared to the low-temperature side on the other side, but it is not necessary for the high-temperature fluid to flow. Particularly, the temperature of the fluid flowing through the flow path21A in the cooling section21is lowered, thereby, the temperature of the portion21B which corresponds to the low-temperature side is further lowered and, thus a freezing function is performed. In other words, the cooling section21has a function as a freezing unit. Accordingly, tap water at room temperature or the like flows through, for example, the flow path21A and, thereby it is possible to lower the temperature of the portion21B which corresponds to the low-temperature side to, for example, about −70° C. InFIG. 1, the flow path21A, the portion21B which corresponds to the low-temperature side, and the heat accumulator19as the cooling section21are collectively surrounded by a dotted line.

Here, a method of operating the hybrid system illustrated inFIG. 1is described. At the time of starting up the fuel cell device, the controller13causes the fuel source feeding means4, the oxygen-containing gas feeding means5, the water pump11, and the ignition device to be operated. At this time, since the temperature of the module1is low, the power generation by the fuel cell or a reforming reaction by the reformer3is not performed. Nearly an entire quantity of a fuel gas supplied by the fuel source feeding means4is combusted as fuel gas not used for power generation, which produces combustion heat that causes the temperature of the module1or the reformer3to rise. When the temperature of the reformer3becomes a temperature at which steam reforming can be performed, the reformer3performs the steam reforming and generates the fuel gas which corresponds to hydrogen-containing gas needed for power generation of the fuel cell. After the reformer3gains the temperature at which the steam reforming can be performed, the controller13may control the water pump11such that the pump operates. When the fuel cell is at the temperature at which the power generation can be started up, the fuel cell starts the power generation with the exhaust gas produced in the reformer3and the oxygen-containing gas supplied by the oxygen-containing gas feeding means5. Electricity generated by the cell stack2is converted into AC power in a power supply adjusting unit12and, then is supplied to an external load.

After power generation is started in the fuel cell, the controller13, for efficient operation of the fuel cell device, controls operations of the fuel source feeding means4, the oxygen-containing gas feeding means5, the water pump11, and the like on the basis of preset fuel utilization (Uf), air utilization (Ua), and a value of S/C which represents a molar ratio between carbon in the fuel and water in the steam reforming by the reformer3. The fuel utilization is a value obtained by dividing an amount of the fuel gas used for power generation by an amount of the fuel gas (fuel source) supplied by the fuel source feeding means4, and the air utilization is a value obtained by dividing an amount of air used for power generation by an amount of air supplied by the oxygen-containing gas feeding means5.

The exhaust gas produced through the operation of the cell stack2flows through the high-temperature side flow path20A that configures the thermoacoustic energy generating section20in the motor15of the thermoacoustic cooler14. Specifically, piping (flow path) through which the exhaust gas emitted from the fuel cell device flows is provided to surround one side (high-temperature side) of the piping in which a heat accumulator18is disposed. Such a configuration enables the exhaust gas to flow through the high-temperature side flow path20A of the thermoacoustic energy generating section20. In the following description as well, each unit of piping is disposed to surround the piping of the thermoacoustic cooler14and is configured to cause each fluid to flow through each portion of the thermoacoustic cooler14.

Thus, a temperature gradient is produced between one side and the other side of the heat accumulator18and it is possible to generate thermoacoustic energy. The greater a difference between the temperatures of the low-temperature side and the high-temperature side of the heat accumulator18which correspond to the thermoacoustic energy generating section20, the more efficiently the thermoacoustic energy can be generated. Therefore, for example, tap water at room temperature or the like may be fed to the low-temperature side flow path20B.

In addition, in the hybrid system illustrated inFIG. 1, a solid oxide fuel cell (cell stack2) is used as the fuel cell, thereby, heat of the exhaust gas emitted from the module1becomes extremely high in temperature and, thus, a temperature gradient is more likely to be produced. In this way, it is possible to efficiently generate thermoacoustic energy and it is possible to achieve the thermoacoustic cooler14which has a good cooling function by using the generated thermoacoustic energy.

One end of the high-temperature side flow path20A is connected to the heat exchanger6. That is, a configuration is employed, in which the exhaust gas emitted from the fuel cell device flows through the high-temperature side flow path20A which corresponds to the high-temperature side of the thermoacoustic energy generating section and, then, flows to the heat exchanger6. It is preferable that, in the heat exchanger6, the temperature of the exhaust gas fed to the heat exchanger6be lowered substantially to room temperature, and the exhaust gas emitted from the fuel cell device be subjected to heat exchange with, for example, water, fuel gas or oxygen-containing gas which is fed to the fuel cell device, or the like.

In addition, water contained in the exhaust gas emitted from the cell stack2through heat exchange in the heat exchanger6is condensed and the condensed water is fed to the condensed water processing device7through the condensed water feeding pipe9. The condensed water is processed to become pure water in the condensed water processing device7and the processed pure water is fed to the water tank8. Water stored in the water tank8is fed to the reformer3through a water feeding pipe10by the water pump11. In this way, condensed water is effectively utilized and, thus it is possible to perform operation using water self-sustainingly.

As described above, since the hybrid system according to the present embodiment has a function as the cooler16in the thermoacoustic cooler14, as well as a function of power generation by the fuel cell device, it is possible to achieve the hybrid system which is useful particularly for a commercial facility such as a convenience store or a supermarket and of which overall efficiency is improved.

Subsequently, the fuel cell device according to the present embodiment will be described.

FIG. 2is an external perspective view illustrating an example of the module in the fuel cell device that configures the hybrid system according to the present embodiment.FIG. 3is a cross-sectional view ofFIG. 2.

The module1illustrated inFIG. 2is configured to accommodate a cell stack device30inside a container22. The cell stack device30includes two cell stacks2in which columnar fuel cells23which have a fuel gas flow path (not illustrated) in which fuel gas circulates are arranged in a row in a state of standing upright, adjacent fuel cells23are connected electrically in series via a power collecting member (not illustrated inFIG. 2), and the lower end of the fuel cells23are fixed to a manifold24by an insulative joining material (not illustrated) such as a glass seal material. In addition, the cell stack device30includes, over the cell stack2, the reformer3for generating fuel gas that is fed to the fuel cell23. Conductive members (not illustrated) which have an electricity lead-out unit for collecting electricity generated through power generation of the cell stack2(fuel cell23) are disposed at both end portions of the cell stack2. The cell stack device30is configured to include each member described above.FIG. 2illustrates a case where the cell stack device30includes two cell stacks2, but it is possible to change the number of the cell stacks. For example, the cell stack device30may include only one cell stack2.

In addition,FIG. 2illustrates, as the fuel cell23, a solid-oxide fuel cell23having a hollow flat plate shape which includes a fuel gas flow path in which fuel gas circulates in the longitudinal direction, and is formed of a fuel electrode layer, a solid electrolyte layer, and an oxygen electrode layer which are laminated in this order on a surface of a support which includes a fuel gas flow path. Oxygen-containing gas circulates between the fuel cells23.

In addition, in the fuel cell device according to the present embodiment, the fuel cell23may be a solid-oxide fuel cell and, for example, can be flat plate-like or cylindrical, and the shape of the container22can be appropriately modified.

In addition, the reformer3illustrated inFIG. 2performs reforming of the fuel source such as natural gas or kerosene which is supplied through a fuel source feeding pipe28such that fuel gas is generated. It is preferable that the reformer3have a structure in which the steam reforming can be performed as an efficient reforming reaction. The reformer3includes a vaporizing section25for vaporizing water and a reforming section26in which a reforming catalyst (not illustrated) for reforming the fuel source into the fuel gas is disposed. The fuel gas generated by the reformer3is fed to the manifold24through a fuel gas circulating pipe27and then is fed to the fuel gas flow path inside the fuel cells23by the manifold24.

In addition,FIG. 2illustrates a state in which a part (front and rear surfaces) of the container22is removed and the cell stack device30accommodated inside is taken out rearward. Here, in the module1illustrated inFIG. 2, it is possible for the cell stack device30to slide into the container22and to be accommodated therein.

An oxygen-containing gas guiding member29is disposed between the cell stacks2disposed in parallel on the manifold24inside the container22such that the oxygen-containing gas flows through the fuel cell23from the lower end portion toward the upper end portion.

As illustrated inFIG. 3, the container22configures the module1has a double structure including an interior wall31and an exterior wall32by which an exterior frame of the container22is formed and a generator space33in which the cell stack device30is accommodated is formed by the interior wall31. Further, in the container22, an oxygen-containing gas flow path39, in which oxygen-containing gas that is guided to the fuel cell23circulates, is formed between the interior wall31and the exterior wall32.

The oxygen-containing gas guiding member29includes an oxygen-containing gas inlet (not illustrated), a flange43and an oxygen-containing gas outlet34. The oxygen-containing gas guiding member29is inserted through the interior wall31at the upper section of the container22so as to be fixed in the container22. Oxygen-containing gas flow in through the oxygen-containing gas inlet. The oxygen-containing gas inlet and a flange43are provided at the upper side of the oxygen-containing gas guiding member29. The oxygen-containing gas outlet34guides oxygen-containing gas to the lower end portion of the fuel cell23. The oxygen-containing gas outlet34is provided at the lower portion of the oxygen-containing gas guiding member29.

InFIG. 3, the oxygen-containing gas guiding member29is disposed to be positioned between the two cell stacks2disposed in parallel in the container22, but can be appropriately disposed depending on the number of the cell stacks2. For example, in a case where a single cell stack2is accommodated in the container22, two oxygen-containing gas guiding members29are provided and can be disposed such that the cell stack2is interposed therebetween from both side surfaces.

In addition, in the generator space33, the insulating member35for maintaining the temperature in the module1to be high is appropriately provided such that heat in the module1is not extremely diffused, the temperature of the fuel cell23(cell stack2) is not lowered, and an amount of power generation is not reduced.

It is preferable that the insulating member35be disposed in the vicinity of the cell stack2, be disposed on the side surfaces of the cell stack2along the arrangement direction of the fuel cells23, and have a width equal to or more than the width of a side surface of the cell stack2along the arrangement direction of the fuel cell23. It is preferable that the insulating member35be disposed on both side surfaces of the cell stack2. In this way, it is possible to effectively suppress reduction of the temperature of the cell stack2. Further, it is possible to suppress emission, from side surfaces of the cell stack2, of the oxygen-containing gas that is guided by the oxygen-containing gas guiding member29and it is possible to quicken flowing of oxygen-containing gas between the fuel cells23that configure the cell stack2. An opening36is provided in the insulating member35on both side surfaces of the cell stack2so as to adjust the flow of the oxygen-containing gas fed to the fuel cell23and to reduce the temperature distribution in the longitudinal direction of the cell stack2and in a stacking direction of the fuel cells23.

In addition, an interior wall37for the exhaust gas is provided to the inside of the interior wall31along the arrangement direction of the fuel cells23and an exhaust gas flow path40through which the exhaust gas in the generator space33flows from the upper side to the lower side is formed between the interior wall31and the interior wall37for the exhaust gas. The exhaust gas flow path40communicates with an exhaust hole38provided on the bottom of the container22. In addition, the insulating member35is provided on the cell stack2side of the interior wall37for the exhaust gas.

Thus, the exhaust gas produced through operation (during a start-up process, during power generation, during a stop process) of the module1flows through the exhaust gas flow path40and then is emitted through the exhaust hole38. The exhaust hole38may be formed by cutting out a part of the bottom of the container22or by providing a pipe-like member.

A thermocouple42for measuring the temperature in the vicinity of the cell stack2is disposed in the oxygen-containing gas guiding member29such that a temperature sensing portion41of the thermocouple42is disposed at the central portion of the fuel cell23in the longitudinal direction and at the central portion of the fuel cells23in the arrangement direction.

In addition, in the module1having the configuration described above, the fuel gas and oxygen-containing gas, which are emitted from at least a part of the fuel gas flow path in the fuel cells23and are not used for power generation, are combusted between the upper end side of the fuel cells23and the reformer3and, thereby it is possible to raise and maintain the temperature of the fuel cells23. Further, it is possible to warm the reformer3above the fuel cells23(cell stack2) and it is possible to perform an efficient reforming reaction in the reformer3. During normal power generation, the temperature in the module1is about 500° C. to 800° C. due to the combustion described above or the power generation of the fuel cells23. Accordingly, the temperature of the exhaust gas emitted from the module1is very high.

FIG. 4is a diagram illustrating another example of a configuration of a hybrid system according to the present embodiment. When compared to the hybrid system according to the present embodiment illustrated inFIG. 1, The present embodiment has differences in that the fuel cell device includes a hot-water storage unit and heat exchange between the exhaust gas emitted from the fuel cell device and circulating water that circulates through the hot-water tank44and heat exchanger6is performed by the heat exchanger6.

That is, when compared to the hybrid system illustrated inFIG. 1, the hybrid system illustrated inFIG. 4includes circulation piping45that causes water to be circulated to the heat exchanger6, an outlet water temperature sensor46for measuring the temperature of water (circulating water flow) which flows through an outlet of the heat exchanger6provided at the outlet of the heat exchanger6, a circulation pump47for circulating water in the circulation piping45, and a hot water tank44in which water (hot water) after flowing through the circulation piping45and being undergone heat exchange is stored.

In such a hybrid system, the exhaust gas flowing through the high-temperature side flow path20A in the motor15(thermoacoustic energy generating section20) of the thermoacoustic cooler14is sequentially fed to the heat exchanger6, undergoes heat-exchange with the circulation water that flows through the circulation piping45in the heat exchanger6, and hot water is produced.

That is, the hybrid system illustrated inFIG. 4, has three functions of, in addition to power generation in the fuel cell device and a cooling function in the thermoacoustic cooler, producing of hot water in the hot water unit. Accordingly, it is possible to achieve a hybrid system in which overall efficiency is improved.

FIGS. 5 and 6are diagrams illustrating still another example of a configuration of a hybrid system according to the present embodiment.

In these hybrid systems, when compared to the hybrid system illustrated inFIG. 4, one end of the flow path21A of the cooler16is connected to the heat exchanger6or the hot water tank44. That is, water at room temperature flows through the flow path21A, and the water from the flow path21A flows directly to the heat exchanger6, or through the hot water tank44and the circulation piping45to the heat exchanger6. In the hybrid system illustrated inFIG. 5, instead of the circulation piping45, a hot-water collecting pipe48connects the heat exchanger6and the hot water tank44.

As described above, the temperature on the high-temperature side corresponding to one side of the heat accumulator19of the cooler16is maintained to be low and, thereby it is possible to lower the temperature on the low-temperature side corresponding to the other side of the heat accumulator19. Then, the cooler16performs the function of cooling efficiently. In addition, the temperature on the high-temperature side of the heat accumulator19of the cooler16is maintained to be yet lower and, thereby the cooler16has a function as a freezing machine.

In a power generation system illustrated inFIGS. 5 and 6, water at room temperature flows through the flow path21A of the cooler16, whereby it is possible to maintain a low temperature on the high-temperature side of the heat accumulator19, and it is possible for the cooler16to function as an efficient cooler. Further, the water from the flow path21A flows directly to the heat exchanger6or flows through the hot water tank44and the circulation piping45to the heat exchanger6and, thereby it is possible to effectively utilize water. Thus, it is possible to achieve the hybrid system of which overall efficiency is further improved.

FIG. 7is a diagram illustrating still another example of a configuration of a power generation system according to the present embodiment. When compared to the hybrid system illustrated inFIG. 6, the flow path21A and the low-temperature side flow path20B are integrally formed and one end of the low-temperature side flow path20B is connected to the heat exchanger6. That is, a fluid after flowing through the flow path21A of the cooling section21flows through the low-temperature side flow path20B of the thermoacoustic energy generating section20and then flows to the heat exchanger6.

As described above, the greater the temperature gradient between one side and the other side of the heat accumulator18in the thermoacoustic energy generating section20, the greater the thermoacoustic energy likely to be generated. Here, the water at room temperature after flowing through the flow path21A of the cooling section21is caused to flow continuously through the low-temperature side flow path20B of the thermoacoustic energy generating section20and, thereby, the temperature gradient is more likely to be produced between one side and the other side of the heat accumulator18in the thermoacoustic energy generating section20.

Further, the water at room temperature flowing through the flow path21A of the cooling section21flows through the low-temperature side flow path20B of the thermoacoustic energy generating section20and, then is fed to the lower section (low-temperature side) of the hot water tank44, and thereby it is possible to utilize water more effectively. Thus, it is possible to achieve a hybrid system of which overall efficiency is further improved.

FIG. 8is a diagram illustrating still another example of a configuration of a hybrid system according to the present embodiment.

In the hybrid system illustrated inFIG. 8, the fuel cell device does not include the hot-water storage unit, but the heat exchanger6includes the circulation flow path49in which a fluid having undergone heat-exchange with the exhaust gas from the fuel cell device flows through the flow path21A of cooling section21, the low-temperature side flow path20B of the thermoacoustic energy generating section20, and the heat exchanger6in this order. That is, the flow paths are integrally formed.

In addition, a pump50is provided on the circulation flow path49. Thus, there is no need to provide separate flow paths for respective heat exchanging portions and it is possible to more simply configure the thermoacoustic cooler14. Control of operation of the pump50makes it possible to control a cooling function of the thermoacoustic cooler14.

In addition, the circulation flow path49is configured to cause the fluid flowing through the circulation flow path49to flow through the flow path21A of the cooling section21and then to flow through the low-temperature side flow path20B of the thermoacoustic energy generating section20. In this way, it is possible for the fluid low in temperature to flow through the flow path21A of the cooling section21and, thus, it is possible for the cooling section21to have a greater cooling function. There is no particular limitation to a fluid flowing through the circulation flow path49and, for example, it is possible to use tap water, air, or the like at room temperature.

In addition, in the hybrid system illustrated inFIG. 8, a cooler51for cooling the fluid flowing through the circulation flow path49is provided in the circulation flow path49.

The fluid flowing through the circulation flow path49becomes high in temperature at some times in a course of flowing through the low-temperature side of the thermoacoustic energy generating section20, or in a course of heat exchange with the exhaust gas emitted from the fuel cell device in the heat exchanger6. Particularly, the fluid becomes significantly high in temperature some times, through heat exchange with the exhaust gas emitted by the fuel cell device in heat exchanger6. When such a fluid high in temperature flows through the high-temperature side of the cooling section21, the temperature on the low-temperature side rises. Then, there is a concern that the cooling function may deteriorate.

Thus, in the hybrid system illustrated inFIG. 8, since the cooler51for cooling the fluid flowing through the circulation flow path49is provided on the circulation flow path49, it is possible to maintain the temperature of the fluid flowing through the circulation flow path49to be low and it is possible to suppress deterioration of the cooling function in the cooling section21.

The cooler51may perform cooling of the fluid flowing through the circulation flow path49, but the configuration is not limited thereto. For example, it is possible for the circulation flow path49to pass through a container where tap water is stored, other than a radiator, or for the circulation flow path49be provided around a cylindrical body in which tap water flows.

Further, inFIG. 8, in the thermoacoustic energy generating section20, an exhaust gas pipe through which the exhaust gas emitted from the fuel cell device flows and of which a part becomes the flow path20A is represented by an exhaust gas pipe52. In addition, in the thermoacoustic energy generating section20, piping in which the heat accumulator18is disposed is represented by piping53. The piping will be described later.

FIGS. 9 and 10are diagrams illustrating still another example of a configuration of a hybrid system according to the present embodiment. When compared to the hybrid system inFIG. 8, the hybrid system inFIG. 9has a configuration in which heat exchange between the fluid flowing through the circulation flow path49and the fuel source which is fed to the reformer3is performed in the cooler51and the hybrid system inFIG. 10has a configuration in which heat exchange between the fluid flowing through the circulation flow path49and the oxygen-containing gas which is fed to the cell stack2is performed in the cooler51. That is, the cooler51functions as a heat exchanging section.

Particularly, in the fuel cell device that uses the solid-oxide fuel cell23as the fuel cell23, power generation of the fuel cell23is performed at a very high temperature. Therefore, it is preferable that the temperature of the fuel source or the oxygen-containing gas which is fed to the module1be high. Here, in the cooler51, the fluid flowing through the circulation flow path49undergoes heat-exchange with the fuel source or the oxygen-containing gas and, thereby, it is possible to raise the temperature of the fuel source or the oxygen-containing gas which is fed to the module1. Thus, it is possible to improve power generation efficiency of the fuel cell device and it is possible to achieve a hybrid system of which overall efficiency is improved.

FIGS. 11A to 11Dare external perspective views or cross-sectional views illustrating a dispositional relationship between an exhaust gas pipe and piping in the hybrid system according to the present embodiment.

FIGS. 11A to 11Dshows external perspective views or cross-sectional views selectively illustrating connections or examples of the connection shapes between the piping53and the exhaust gas pipe52surrounded by a dotted line inFIG. 8.FIG. 11Ais an external perspective view illustrating a structure at a position (hereinafter, in the exhaust gas pipe52and the piping53, a structure at a portion where the exhaust gas pipe52covers the piping53is referred to as a double pipe54) at which the exhaust gas pipe52covers the piping53.FIG. 11Bis a cross-sectional view taken along line A-A inFIG. 11A,FIG. 11Cis a cross-sectional view illustrating another example, andFIG. 11Dis a cross-sectional view illustrating still another example. Here, these configurations are described in this order.

FIGS. 11A and 11Billustrate selectively the high-temperature side of the heat accumulator18in the piping53and show a structure of the double pipe54in which the exhaust gas pipe52is disposed to cover the outer circumference of the piping53. Thus, the heat of the exhaust gas emitted from the fuel cell device which flows in the exhaust gas pipe52(in other words, in the high-temperature side flow path20A, and hereinafter, used with the same meaning) is efficiently transferred to the piping53and, thereby, it is possible to cause the temperature gradient in the thermoacoustic energy generating section20to be great.

FIGS. 11A and 11Billustrate an example of a configuration in which the exhaust gas flowing through the exhaust gas pipe52flows from the upper side to the lower side. As long as the structure of the double pipe54is provided, the exhaust gas flowing through the exhaust gas pipe52can flow in a horizontal direction, in addition to the vertical direction.

In addition, when conductivity of the exhaust gas flowing through the exhaust gas pipe52to the piping53is improved, the heat conductivity of the exhaust gas pipe52can be further improved than the heat conductivity of the piping53. Thus, it is possible to efficiently transfer heat of the exhaust gas flowing through the exhaust gas pipe52to the piping53and it is possible to improve the performance of the thermoacoustic cooler14.

FIG. 11Cillustrates a configuration in which a protrusion55that protrudes toward the piping53is provided on the inner wall of the exhaust gas pipe52at a portion on an outer circumference of the piping53which corresponds to a portion that becomes the double pipe54.

In such a configuration, the exhaust gas flowing through the exhaust gas pipe52produces turbulence and it is possible to efficiently transfer heat of the exhaust gas flowing through the exhaust gas pipe52to the piping53.FIG. 11Cillustrates a configuration in which the protrusion55is provided on the inner wall of the exhaust gas pipe52; otherwise, in a case where a protrusion that protrudes toward the exhaust gas pipe52is provided on an outer wall in a portion of the piping53which becomes the double pipe54, it is possible to increase the surface area of the piping53in addition to producing turbulence by the exhaust gas flowing through the exhaust gas pipe52. Then, it is possible to further efficiently transfer heat of the exhaust gas flowing through the exhaust gas pipe52to the piping53. It is possible to provide the protrusion55on both the exhaust gas pipe52and the piping53; however, in this case, it is preferable that the protrusions55be provided to an extent that there is no effect on the flow of the exhaust gas flowing through the exhaust gas pipe52.

FIG. 11Dillustrates a configuration in which an insulating member56is provided on an outer circumference of a portion (portion of double pipe54) of the exhaust gas pipe52corresponding to the high-temperature side of the thermoacoustic energy generating section. In this way, the insulating member56is provided over the outer circumference of a portion of the exhaust gas pipe52corresponding to the high-temperature side of the thermoacoustic energy generating section, whereby, it is possible to suppress diffusion of heat of the exhaust gas flowing through the exhaust gas pipe52, and it is possible to transfer more heat to the piping53.FIG. 11Dillustrates an example in which the insulating member56is provided over the outer circumference of a portion of the exhaust gas pipe52corresponding to the high-temperature side of the thermoacoustic energy generating section; however, the insulating member56may cover the entire exhaust gas pipe52such that the temperature of the heat of the exhaust gas flowing through the exhaust gas pipe52is maintained to be high.

Further, in the above description, the exhaust gas pipe52and the piping53are configured as the double pipe; however, the shape of the double pipe is not limited, as long as the heat of the exhaust gas flowing through the exhaust gas pipe52is transferred efficiently to the piping53. For example, an exhaust gas pipe52may be provided which wraps around the outer circumference of the piping53in a spiral shape.

FIG. 12illustrates an example in which, in the configuration of the exhaust gas pipe52and the piping53illustrated inFIG. 11B, a combustion catalyst57is disposed inside the portion (portion of the double pipe54) of the exhaust gas pipe52to which the piping53is connected.

As described above, the heat of the exhaust gas flowing through the exhaust gas pipe52is transferred to the piping53and, thereby it is possible to cause the temperature gradient in the thermoacoustic energy generating section20to become greater. Here, unburned fuel gas is contained in the exhaust gas flowing through the exhaust gas pipe52in some cases. Accordingly, the combustion catalyst57is provided inside at least the portion of the exhaust gas pipe52to which the piping53is connected and, thereby the unburned gas components contained in the exhaust gas are subjected to a combustion reaction. Therefore, when compared to a case where the combustion catalyst is not provided, it is possible to achieve a high temperature state. Thus, it is possible to increase a practical heat capacity of the exhaust gas flowing through the exhaust gas pipe52. Thus, since it is possible to increase an amount of heat transferred to the piping53, it is possible to increase the temperature gradient in the thermoacoustic energy generating section20and the cooling section16can efficiently perform a cooling function. The combustion catalyst57may be disposed at least inside the portion of the exhaust gas pipe52to which the piping53is connected and it is possible to provide the combustion catalyst57in other portions of the exhaust gas pipe52.

Here, as the combustion catalyst57, it is possible to use a combustion catalyst which is commonly used and for example, it is possible to use a combustion catalyst in which a catalyst such as a noble metal such as platinum or palladium is carried on a porous carrier such as y-alumina, a-alumina, or cordierite.

In addition, inFIG. 12, a partition member58is disposed at a position where the combustion catalyst57is disposed such that the combustion catalyst57does not fall out, which is disposed inside the exhaust gas pipe52at a portion to which the piping53is connected.FIG. 12illustrates an example in which, in the exhaust gas pipe at a portion to which the piping53is connected, the partition member58is provided at two places of an entrance side and an outlet side (up and down) with respect to a flowing direction of the exhaust gas. As long as the partition member58has heat resistance, does not interrupt the flow of the exhaust gas, and further can suppress falling out of the combustion catalyst57, there is no limitation to the member. For example, as the partition member58, it is possible to use a mesh-like member made of a metal or the like.

FIG. 12shows a configuration based on the configuration illustrated inFIG. 11B, and, for example, the same combustion catalyst57can be provided to the configuration illustrated inFIGS. 11C and 11D.

The present invention is described in detail as above, but the present invention is not limited to the above embodiments, and can be modified and improved in various ways within a range without departing from the spirit of the invention.

For example, in the hybrid system described above, an example of the fuel cell device is described using the fuel cell device that includes the solid-oxide fuel cell, but a polymer electrolyte fuel cell may be included. In a case where the polymer electrolyte fuel cell is used, for example, heat produced during the reforming reaction is effectively used or the configuration may appropriately be modified.

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