Power generation system

This power generation system is provided with: a gas turbine (11) having a compressor (21), a combustor (22) and a turbine (23); a first compressed air supply line (26) that supplies compressed air, which has been compressed by the compressor (21), to the combustor (22); a solid oxide fuel cell (SOFC) (13) having an air electrode and a fuel electrode; a compressed air supply device (61) capable of generating compressed air; and a second compressed air supply line (31) that supplies compressed air, which has been compressed by the compressed air supply device (61) to the SOFC (13). The fuel cell can thus be stably operated regardless of the operating state of the gas turbine.

TECHNICAL FIELD

The present invention relates to a power generation system combining a fuel cell, a gas turbine, and a steam turbine.

BACKGROUND ART

The solid oxide fuel cell (hereinafter, referred to as SOFC) is known as a high efficiency fuel cell with a wide range of uses. The operating temperature of the SOFC is increased to increase the ionic conductivity, so air discharged from the compressor of a gas turbine can be used as air (oxidizing agent) supplied to the air electrode side. Also, high-temperature fuel that could not be used in an SOFC can be used as the fuel in the combustor of a gas turbine.

Therefore, various combinations of SOFC, gas turbine, and steam turbine have been proposed as power generation systems that can achieve high efficiency power generation, as disclosed in, for example, Patent Document 1. The combined system disclosed in Patent Document 1 includes an SOFC, a gas turbine combustor that burns exhaust fuel gas and exhaust air discharged from the SOFC, and a gas turbine having a compressor that compresses air for supply to the SOFC.

CITATION LIST

Patent Document

Patent Document 1: Japanese Unexamined Patent Application Publication No. 2009-205930A

SUMMARY OF THE INVENTION

Technical Problem

During normal operation of the conventional power generation system described above, air compressed by the compressor of the gas turbine is supplied to the combustor of the gas turbine, a portion of the air being supplied to the SOFC for use as an oxidizing agent. In this case, the pressure of the air compressed by the compressor fluctuates according to the operating state of the gas turbine, with the result that the pressure of the compressed air supplied to the SOFC also fluctuates according to the operating state of the gas turbine, leading to the risk of being incapable of maintaining a stable operating state of the SOFC. For example, the power generator is activated through the driving of the gas turbine; if the frequency of the power generator fluctuates, the gas turbine engages in output control in order to keep the frequency at a predetermined frequency. Specifically, the output of the gas turbine is adjusted by adjusting the amount of fuel supplied thereto; during this process, the pressure of the compressed air at the outlet of the compressor fluctuates, causing the pressure of the compressed air supplied to the SOFC to also fluctuate.

The present invention solves the problems described above, and has an object of providing a power generation system allowing a fuel cell to be stably operated regardless of the operating state of a gas turbine.

Solution to Problem

In order to achieve the object proposed above, a power generation system of the present invention comprises: a gas turbine having a compressor and a combustor; a first compressed air supply line for supplying first compressed air compressed by the compressor to the combustor; a fuel cell having an air electrode and a fuel electrode; a compressed air supply unit capable of generating second compressed air; and a second compressed air supply line for supplying second compressed air compressed by the compressed air supply unit to the fuel cell.

Thus, a compressed air supply unit is provided separately from the gas turbine compressor, with first compressed air compressed by the gas turbine compressor being supplied to the combustor via the first compressed air supply line, and second compressed air compressed by the compressed air supply unit being supplied to the fuel cell via the second compressed air supply line. Therefore, there is no fluctuation in the pressure of the air supplied to the fuel cell even if the pressure of the air supplied to the combustor fluctuates according to the operating state of the gas turbine. As a result, the fuel cell can be stably operated regardless of the operating state of the gas turbine.

The power generation system of the present invention comprises: a heat recovery steam generator for generating steam using exhaust gas from the gas turbine; and a steam turbine driven by steam generated by the heat recovery steam generator, the compressed air supply unit having a steam-driven fuel cell compressor and a steam supply line for supplying steam generated by the heat recovery steam generator to the fuel cell compressor.

Accordingly, when steam generated by the heat recovery steam generator is supplied to the fuel cell compressor via the steam supply line, the fuel cell compressor is driven by the steam to generate second compressed air, which is supplied to the fuel cell. The power generation system combines a fuel cell, a gas turbine, and a steam turbine, with steam generated within the system being used to drive the fuel cell compressor to generate second compressed air, and the second compressed air being supplied to the fuel cell to improve overall system efficiency.

In the power generation system of the present invention, the compressed air supply unit includes a fuel cell compressor and a drive motor for driving the fuel cell compressor.

Accordingly, the fuel cell compressor is driven by the drive motor to generate second compressed air, which is supplied to the fuel cell. Simply by providing the drive motor and the fuel cell compressor, the second compressed air can be supplied to the fuel cell independently of the gas turbine, allowing stable operation of the fuel cell to be ensured with a simple arrangement.

The power generation system of the present invention comprises: a first on/off valve capable of opening and closing the second compressed air supply line; a bypass line connecting the first compressed air supply line and the second compressed air supply line; and a second on/off valve for opening and closing the bypass line.

Accordingly, the second compressed air generated by driving the fuel cell compressor can be supplied to the combustor via the bypass line, allowing the amount of compressed air to be adjusted according to the operating state of the gas turbine or the fuel cell.

The power generation system of the present invention comprises a control unit capable of opening and closing the first on/off valve and the second on/off valve, the control unit closing the first on/off valve and opening the second on/off valve when the fuel cell is stopped.

Accordingly, when the fuel cell is stopped, the first on/off valve is closed to stop the supply of second compressed air from the compressed air supply unit to the fuel cell, and the second on/off valve is opened to start the supply of second compressed air from the compressed air supply unit to the gas turbine combustor, ensuring the amount of compressed air in the gas turbine and allowing the gas turbine to operate stably.

Effect of the Invention

In accordance with the power generation system of the present invention, first compressed air compressed by the compressor can be supplied to the combustor and second compressed air compressed by the compressed air supply unit can be supplied to the fuel cell, allowing the fuel cell to operate stably regardless of the operating state of the gas turbine.

DETAILED DESCRIPTION OF THE INVENTION

Preferred embodiments of the power generation system according to the present invention will now be described in detail with reference to the attached drawings. The present invention is not limited by these embodiments, and, when there is a plurality of embodiments, configurations that combine these embodiments are also included.

First Embodiment

The power generation system according to a first embodiment is a Triple Combined Cycle (registered trademark) that combines a solid oxide fuel cell (hereinafter, referred to as SOFC), a gas turbine, and a steam turbine. The Triple Combined Cycle can generate electricity in the three stages of the SOFC, the gas turbine, and the steam turbine by installing the SOFC on the upstream side of a gas turbine combined cycle power generation system (GTCC), so it is possible to achieve extremely high power generation efficiency.

FIG. 1is a schematic view illustrating a compressed air supply line in the power generation system according to the first embodiment of the present invention, andFIG. 2is a schematic view of the configuration of the power generation system according to the first embodiment.

As illustrated inFIG. 2, in the first embodiment, a power generation system10comprises a gas turbine11, a generator12, an SOFC13, a steam turbine14, and a generator15. The power generation system10is configured to achieve high power generation efficiency by combining the power generation by the gas turbine11, the power generation by the SOFC13, and the power generation by the steam turbine14.

The gas turbine11includes a compressor21, a combustor22, and a turbine23, and the compressor21and the turbine23are connected by a rotary shaft24so that they rotate integrally. The compressor21compresses air A that is drawn in from an air intake line25. The combustor22mixes and burns compressed air (first compressed air) A1supplied from the compressor21via a first compressed air supply line26and fuel gas L1supplied via a first fuel gas supply line27. The turbine23is rotated by exhaust gas (combustion gas) G supplied from the combustor22via an exhaust gas supply line28. Although not illustrated on the drawings, the compressed air A1compressed by the compressor21is supplied to the casing of the turbine23, and the compressed air A1cools the blades and the like as cooling air. The generator12is provided coaxially with the turbine23, and can generate power by the rotation of the turbine23. Note that here, for example, liquefied natural gas (LNG) is used as the fuel gas L1supplied to the combustor22.

The SOFC13is supplied with high-temperature fuel gas as a reductant and high-temperature air (oxygen gas) as an oxidant, which react at a predetermined operating temperature to generate power. The SOFC13is configured from an air electrode, a solid electrolyte, and a fuel electrode, housed within a pressure vessel. Power is generated by supplying compressed air to the air electrode and supplying fuel gas to the fuel electrode. The fuel gas L2supplied to the SOFC13is, for example, liquefied natural gas (LNG).

A compressed air supply device (compressed air supply unit)61is linked to the SOFC13via the second compressed air supply line31, allowing compressed air (second compressed air) A2compressed by the compressed air supply device61to be supplied to an inlet of the air electrode. A control valve (first on/off valve)32that can adjust the flow rate of the air supplied, and a blower33that can increase the pressure of the compressed air A2are provided along an air flow direction on the second compressed air supply line31. An exhaust air line34into which exhaust air A3that was used at the air electrode is discharged is connected to the SOFC13. The exhaust air line34branches into an exhaust line35that discharges to the outside exhaust air A3that was used at the air electrode, and a compressed air circulation line36that is connected to the combustor22. A control valve37that can adjust the flow rate of the air discharged is provided on the exhaust line35, and a control valve38that can adjust the flow rate of the circulating air is provided on the compressed air circulation line36.

Also, a second fuel gas supply line41is provided on the SOFC13to supply the fuel gas L2to the inlet of the fuel electrode. A control valve42that can adjust the supplied fuel gas flow rate is provided on the second fuel gas supply line41. The SOFC13is connected to an exhaust fuel line43in which exhaust fuel gas L3that was used at the fuel electrode is discharged. The exhaust fuel line43branches into an exhaust line44that discharges to the outside, and an exhaust fuel gas supply line45connected to the combustor22. A control valve46that can adjust the flow rate of the fuel gas discharged is provided on the exhaust line44, and a control valve47that can adjust the flow rate of the fuel gas supplied and a blower48that can increase the pressure of the fuel are provided on the exhaust fuel gas supply line45along the flow direction of the fuel gas L3.

Also, a fuel gas recirculation line49is provided on the SOFC13connecting the exhaust fuel line43and the second fuel gas supply line41. A recirculation blower50that recirculates the exhaust fuel gas L3of the exhaust fuel line43to the second fuel gas supply line41is provided on the fuel gas recirculation line49.

A turbine52of the steam turbine14is rotated by steam generated by an exhaust heat recovery boiler51(HRSG). The exhaust heat recovery boiler51is connected to an exhaust gas line53from the gas turbine11(turbine23), and generates steam S by heat exchange between air and high-temperature exhaust gas G. A steam supply line54and a water supply line55are provided between the steam turbine14(turbine52) and the exhaust heat recovery boiler51. A condenser56and a water supply pump57are provided on the water supply line55. The generator15is provided coaxially with the turbine52, and can generate power by the rotation of the turbine52. The exhaust gas from which the heat has been recovered in the exhaust heat recovery boiler51is discharged to the atmosphere after removal of harmful substances.

The compressed air supply system of the power generation system10according to the first embodiment described above will now be described in detail. As illustrated inFIG. 1, the power generation system10according to the first embodiment is provided with a compressed air supply device (compressed air supply unit)61capable of generating compressed air, and a second compressed air supply line31for supplying compressed air compressed by the compressed air supply device61to the SOFC13.

Specifically, the compressed air supply device61, which is capable of stand-alone operation, is provided separately from the compressor21of the gas turbine11, with the compressor21supplying compressed air only to the combustor22(turbine23) via the first compressed air supply line26and the compressed air supply device61supplying compressed air only to the SOFC13via the second compressed air supply line31. Therefore, total quantity of the compressed air compressed by the compressor21is delivered to the combustor22and the turbine23, and total quantity of compressed air compressed by the compressed air supply device61is delivered to the SOFC13. As a result, fluctuations in the operating state of the gas turbine11are not transmitted to the SOFC13, allowing the SOFC13to operate stably. Specifically, the SOFC13generates power as the result of the compressed air A2being supplied to the air electrode and the fuel gas L2being supplied to the fuel electrode. In this case, if the pressure in the air electrode and the pressure in the fuel electrode are not roughly equal, a flow of compressed air A2or fuel gas L2between the air electrode and the fuel electrode will be generated, causing the temperature of the SOFC13to fluctuate. In the present embodiment, the compressed air A1compressed by the compressor21is not supplied to the SOFC13; rather, only compressed air A2compressed by the compressed air supply device61is supplied to the SOFC13, eliminating fluctuations in the pressure in the air electrode of the SOFC13, and allowing the SOFC13to operate stably.

The compressed air supply device61is constituted by an SOFC compressor (fuel cell compressor)62and an SOFC steam turbine (fuel cell steam turbine)63linked by a coupling shaft64so as to be capable of integral rotation. One end of the second compressed air supply line31is connected to the SOFC compressor62and the other end is connected to the SOFC13, and the SOFC compressor62compresses air taken in via an air intake line65. The SOFC compressor62is driven by the rotation of the SOFC steam turbine63by steam generated by the heat recovery steam generator51, and is capable of compressing air. Specifically, one end of a steam supply line66is connected to the steam supply line54for supplying steam from the heat recovery steam generator51to the steam turbine14(turbine52), and the other end is connected to the SOFC steam turbine63. The steam supply line66is provided with a control valve67that is capable of adjusting the amount of supplied steam.

A control device68is at least capable of adjusting the degree of opening of the control valve32and the control valve67and controlling the driving and stopping of the blower33. Thus, when the SOFC13is operating normally, the control device68opens the control valves32,67and supplies steam generated by the heat recovery steam generator51to the SOFC steam turbine63via the steam supply line54to drive the SOFC compressor62.

A bypass line71is provided that connects the first compressed air supply line26and the second compressed air supply line31, and the bypass line71is provided with a control valve (second on/off valve)72that is capable of adjusting the flow rate of compressed air. The control device68is capable of adjusting the degree of opening of the control valve72. Specifically, when the SOFC13is operating normally, the control device68closes the control valve72so that compressed air A2generated by the compressed air supply device61is not supplied to the gas turbine11, but is only supplied to the SOFC13. Conversely, when the SOFC13is stopped, the control valve72is opened and the control valve32is closed so that compressed air generated by the compressed air supply device61is not supplied to the SOFC13, but is only supplied to the gas turbine11.

The following is a description of the operation of the power generation system10according to the first embodiment. As illustrated inFIGS. 1 and 2, when the power generation system10is activated, the gas turbine11, steam turbine14, and SOFC13are activated in that order. The control device68is capable of controlling not only the control valve32and the control valve67, but also the other control valves.

First, in the gas turbine11, the compressor21compresses the air A, and the combustor22mixes and burns the compressed air A1and the fuel gas L1, the turbine23is rotated by the exhaust gas G, and the generator12starts to generate power. Next, in the steam turbine14, the turbine52is rotated by the steam S generated by the exhaust heat recovery boiler51, and, as a result, the generator15starts to generate power.

Next, in the SOFC13, the control valve67is opened so that steam generated by the heat recovery steam generator51is supplied via the steam supply line66to the SOFC steam turbine63of the compressed air supply device61. The SOFC steam turbine63then begins to rotate due to the supplied steam, and the SOFC compressor62is rotatably driven in sync, compressing the air A taken in via the air intake line65. The SOFC compressor62then supplies compressed air A2to the SOFC13via the second compressed air supply line31, and the pressure begins to increase.

At this time, with the control valve37of the exhaust line35and the control valve38of the compressed air circulation line36closed and the blower33of the second compressed air supply line31stopped, the control valve32is opened. Compressed air A2compressed by the compressed air supply device61is then supplied to the SOFC13side via the second compressed air supply line31. In this way, the pressure on the SOFC13side increases due to the supply of the compressed air A2.

On the other hand, in the SOFC13, the fuel gas L2is supplied to the fuel electrode side and the pressure starts to rise. With the control valve46of the exhaust line44and the control valve47of the exhaust fuel gas supply line45closed, and the blower48stopped, the control valve42of the second fuel gas supply line41is opened, and the recirculation blower50of the fuel gas recirculation line49is driven. Then, the fuel gas L2is supplied to the SOFC13side from the second fuel gas supply line41, and the exhaust fuel gas L3is recirculated by the fuel gas recirculation line49. In this way, the pressure on the SOFC13side increases due to the supply of the fuel gas L2.

When the pressure on the air electrode side of the SOFC13reaches a predetermined pressure, the control valve32is fully opened, and the blower33is driven. At the same time, the control valve37is opened and the exhaust air A3from the SOFC13is discharged from the exhaust line35. Then, the compressed air A2is supplied to the SOFC13side by the blower33. At the same time, the control valve46is opened and the exhaust fuel gas L3from the SOFC13is discharged from the exhaust line44. Then, when the pressure of the air electrode side and the pressure of the fuel electrode side of the SOFC13reach the target pressure, pressurization of the SOFC13is completed.

In the present embodiment, a compressed air supply device61and a blower33are provided, but the blower33may be omitted by controlling the compressed air supply device61. Specifically, the degree of opening of the control valve67may be adjusted so as to adjust the amount of steam supplied to the SOFC steam turbine63, and the amount of compressed air A2generated by the SOFC compressor62may be adjusted so as to adjust the amount of compressed air A2supplied to the SOFC13and increase the pressure in the SOFC13. In this case, the omission of the blower33eliminates the need to open and close the control valve32and activate the blower33, allowing for reduced costs.

Then, when the reaction (power generation) of the SOFC13is stable and the components of the exhaust air A3and the exhaust fuel gas L3are stable, the control valve37is closed, and the control valve38is opened. Then, the exhaust air A3from the SOFC13is supplied to the combustor22from the compressed air circulation line36. Also, the control valve46is closed, the control valve47is opened, and the blower48is driven. Then, the exhaust fuel gas L3from the SOFC13is supplied to the combustor22from the exhaust fuel gas supply line45. At this time, the flow rate of the fuel gas L1supplied to the combustor22from the first fuel gas supply line27is reduced.

At this time, total quantity of the compressed air A1compressed by the compressor21is supplied to the combustor22and the turbine23of the gas turbine11, and total quantity of the compressed air A2compressed by the compressed air supply device61is supplied to the SOFC13. Thus, even if a fluctuation in the output of the gas turbine11occurs and the pressure of the air A1compressed by the compressor21fluctuates, there is no fluctuation in the pressure of the air A2supplied to the SOFC13. As a result, there is no fluctuation in the pressure in the air electrode of the SOFC13, the pressure in the air electrode and the pressure in the fuel electrode are roughly equal, and the SOFC13is stably operated regardless of the operating state of the gas turbine11.

When the SOFC13stops operating, the control device68opens the control valve72and closes the control valve32when the SOFC13is stopped, so that the compressed air A2generated by the compressed air supply device61is supplied not to the SOFC13, but to the gas turbine11. When the SOFC13is operating normally, the compressed air A2generated by the compressed air supply device61is supplied to the SOFC13and the used exhaust air A3is supplied to the combustor22of the gas turbine11via the compressed air circulation line36. Thus, when the operation of the SOFC13is stopped, the compressed air A2generated by the compressed air supply device61is not supplied to the SOFC13, but is supplied directly to the combustor22of the gas turbine11via the bypass line71. As a result, roughly equal amounts of compressed air A2are supplied to the gas turbine11both when the SOFC13is operating normally and when it is stopped, allowing for stable power generation by enabling full-load operation. Because exhaust fuel gas from the SOFC13is not supplied to the combustor22of the gas turbine11when the operation of the SOFC13is stopped, the amount of fuel gas supplied via the first fuel gas supply line27must be increased.

As described above, the power generation system according to the first embodiment comprises the gas turbine11having the compressor21, the combustor22, and the turbine23, the first compressed air supply line26for supplying compressed air compressed by the compressor21to the combustor22, the SOFC13having the air electrode and the fuel electrode, the compressed air supply device61capable of generating compressed air, and the second compressed air supply line31for supplying compressed air compressed by the compressed air supply device61to the SOFC13.

Accordingly, the compressed air supply device61is provided separately from the compressor21of the gas turbine11, air A1compressed by the compressor21is supplied to the combustor22via the first compressed air supply line26, and air A2compressed by the compressed air supply device61is supplied to the SOFC13via the second compressed air supply line31. Therefore, there is no fluctuation in the pressure of the air supplied to the SOFC13even if the pressure of the air supplied to the combustor22fluctuates according to the operating state of the gas turbine11. As a result, there is no fluctuation in the pressure in the air electrode of the SOFC13, the pressure in the air electrode and the pressure in the fuel electrode are roughly equal, and the SOFC13can be stably operated regardless of the operating state of the gas turbine11.

The power generation system according td the first embodiment is provided with the heat recovery steam generator51for generating steam using exhaust gas from the gas turbine11and the steam turbine14driven by the steam generated by the heat recovery steam generator51, and the compressed air supply device61is provided with an SOFC compressor62and a steam supply line66for supplying steam generated by the heat recovery steam generator51to the SOFC steam turbine63. Accordingly, when steam generated by the heat recovery steam generator51is supplied to the SOFC steam turbine63via the steam supply line66, the SOFC steam turbine63is driven by the steam so that the SOFC compressor62is driven to generate compressed air A2, which is supplied to the SOFC13. The power generation system10combines the SOFC13, the gas turbine11, and the steam turbine14, and steam generated within the power generation system10is used to drive the SOFC compressor62to generate compressed air A2which is supplied to the SOFC13, thereby allowing overall system efficiency to be increased.

The power generation system of the first embodiment is provided with the control valve32capable of opening and closing the second compressed air supply line31, the bypass line71connecting the first compressed air supply line and the second compressed air supply line31, and the control valve72for opening and closing the bypass line71. Accordingly, the compressed air A2generated by driving the SOFC compressor62can be supplied to the combustor22via the bypass line71, allowing the amount of compressed air to be adjusted according to the operating state of the gas turbine11or the SOFC13.

The power generation system of the first embodiment is provided with the control device68capable of opening and closing the control valve32and the control valve72, and, when the SOFC13is stopped, the control device68closes the control valve32and opens the control valve72. Accordingly, when the SOFC13is stopped, the control valve32is closed to stop the supply of compressed air A2from the compressed air supply device61to the SOFC13, and the control valve72is opened to begin supplying compressed air A2from the compressed air supply device61to the combustor22of the gas turbine11, ensuring the amount of compressed air provided to the gas turbine11and allowing the gas turbine11to operate stably.

Second Embodiment

FIG. 3is a schematic view illustrating a compressed air supply line in a power generation system according to a second embodiment of the present invention. The basis configuration of the power generation system according to the present embodiment is roughly identical to that of the first embodiment described above; thus, for parts described usingFIG. 2and having similar functions as in the first embodiment described above, the same reference numerals are used, and detailed description thereof will be omitted.

In the power generation system of the second embodiment, as illustrated inFIGS. 2 and 3, a compressed air supply device (compressed air supply unit)81is linked to the SOFC13via the second compressed air supply line31, the compressed air supply device81being capable of supplying compressed air A2to an inlet of the air electrode. Specifically, the compressed air supply device81, which is capable of stand-alone operation, is provided separately from the compressor21of the gas turbine11, with the compressor21supplying compressed air A1only to the combustor22(turbine23) via the first compressed air supply line26and the compressed air supply device81supplying compressed air A2only to the SOFC13via the second compressed air supply line31. Therefore, the total quantity of compressed air compressed by the compressor21is delivered to the combustor22and the turbine23, and the total quantity of compressed air compressed by the compressed air supply device81is delivered to the SOFC13. As a result, fluctuations in the operating state of the gas turbine11are not transmitted to the SOFC13, allowing the SOFC13to operate stably.

The compressed air supply device81is constituted by an SOFC compressor (fuel cell compressor)82and a drive motor83linked by a coupling shaft84. One end of the second compressed air supply line31is connected to the SOFC compressor82and the other end is connected to the SOFC13, and the SOFC compressor82compresses air taken in via an air intake line85. The SOFC compressor82is driven by power being supplied to the drive motor83, and is capable of compressing air.

The control device68is at least capable of adjusting the degrees of opening of the control valve32and the control valve72and controlling the driving and stopping of the drive motor83. Thus, when the SOFC13is operating normally, the control device68opens the control valves32,67, and the drive motor83is driven to drive the SOFC compressor82.

A bypass line71is provided that connects the first compressed air supply line26and the second compressed air supply line31, and the bypass line71is provided with a control valve72that is capable of adjusting the flow rate of compressed air. When the SOFC13is operating normally, the control device68closes the control valve72so that compressed air generated by the compressed air supply device81is not supplied to the gas turbine11, but is only supplied to the SOFC13. Conversely, when the SOFC13is stopped, the control valve72is opened and the control valve32is closed so that compressed air generated by the compressed air supply device81is not supplied to the SOFC13, but is only supplied to the gas turbine11.

When the power generation system described above is activated, the gas turbine11, steam turbine14, and SOFC13are activated in that order; however, the SOFC13may also be activated before the gas turbine11.

When operating the SOFC13, the drive motor83is driven so as to rotatably drive the SOFC compressor82, compressing air A taken in via the air intake line85. The SOFC compressor82then supplies compressed air A2to the SOFC13via the second compressed air supply line31. Meanwhile, the control valve42of the second fuel gas supply line41is opened, thereby supplying fuel gas L2to the SOFC13via the second fuel gas supply line41. The compressed air A2and the fuel gas L2then react in the SOFC13, generating power.

At this time, total quantity of the air A1compressed by the compressor21is supplied to the combustor22and turbine23of the gas turbine11, and total quantity of the air A2compressed by the compressed air supply device81is supplied to the SOFC13. Thus, even if a fluctuation in the output of the gas turbine11occurs and the pressure of the air A1compressed by the compressor21fluctuates, there is no fluctuation in the pressure of the air A2supplied to the SOFC13, and the SOFC13is operated stably regardless of the operating state of the gas turbine11.

As described above, the power generation system according to the second embodiment is provided with the gas turbine11having the compressor21, the combustor22, and the turbine23, the first compressed air supply line26for supplying compressed air compressed by the compressor21to the combustor22, the SOFC13having the air electrode and the fuel electrode, the compressed air supply device81capable of generating compressed air, and the second compressed air supply line31for supplying compressed air compressed by the compressed air supply device81to the SOFC13.

Accordingly, the compressed air supply device81is provided separately from the compressor21of the gas turbine11, air A1compressed by the compressor21is supplied to the combustor22via the first compressed air supply line26, and air A2compressed by the compressed air supply device81is supplied to the SOFC13via the second compressed air supply line31. Therefore, there is no fluctuation in the pressure of the air supplied to the SOFC13even if the pressure of the air supplied to the combustor22fluctuates according to the operating state of the gas turbine11. As a result, the SOFC13can be stably operated regardless of the operating state of the gas turbine11.

In the power generation system according to the second embodiment, the compressed air supply device81is provided with the SOFC compressor82and the drive motor83for driving the SOFC compressor82. Accordingly, the SOFC compressor82is driven by the drive motor83to generate compressed air A2, which is supplied to the SOFC13. Simply by providing the drive motor83and the SOFC compressor82, compressed air A2can be supplied to the SOFC13independently of the gas turbine11, allowing stable operation of the SOFC13to be ensured using a simple configuration.

In the embodiments described above, the first on-off valve and the second on-off valve of the present invention are control valves32,72capable of adjusting flow rate, but these valves may be also be cutoff valves incapable of adjusting flow rate.

REFERENCE SIGNS LIST