Method for determining the number of power supply systems and power generating units to be installed

Abstract

To provide a power supply system that can improve the ability of power supply to follow demand changes.SOLUTION: A power supply system 1000 comprises a plurality of power generation units 100, each having the same rated output power, and operating in parallel with a commercial power supply system 500. When the rated output power of each of the power generation units 100 is Qr [W], the reference purchased power preset to be constantly purchased from the commercial power supply system 500 is Qs [W], and the power demand for a predetermined period at a demand facility 600 receiving the power supply is D [W], and n is a natural number obtained by rounding down the decimal point of the number obtained by a calculation (D-Qs) / Qr, the number N of power generation units 100 to be installed satisfies the following formula (1): 2≤N≤n ... (1)SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a power supply system using a fuel cell or the like, and a method for determining the number of power generation units installed in the power supply system.

Background Art

[0002] It is expected that by switching part of the commercial power purchased by a consumer from a power company to self-generated power, it will lead to a reduction in carbon dioxide emissions. For example, the primary energy efficiency of thermal power generation using coal or LNG as fuel is about 40%, while the primary energy efficiency of a solid oxide fuel cell (SOFC) that generates power by reforming fuel with city gas mainly composed of methane can be expected to be 50% - 65%. Therefore, increasing the proportion of self-generated power can contribute to reducing the environmental load.

[0003] In addition, it is expected that by realizing a system that can maintain power supply independently when a power outage occurs due to a natural disaster, the adverse effects on social life and economic activities can be reduced. For example, a solid oxide fuel cell (SOFC) can generate power independently and supply power to the outside as long as the supply of city gas is not interrupted. In the case of an earthquake, the gas infrastructure may be damaged depending on the scale, but in the case of a typhoon, it can be said that there is almost no impact on the gas infrastructure, so power supply can be continued.

[0004] Patent Documents 1 and 2 disclose a power supply system (fuel cell system) that operates in parallel with a commercial power supply system and supplies power to power demand facilities. When the demand during operation is high, such as in power demand facilities in factories, etc., the power supply system is composed of a plurality of power generation units (for example, fuel cell units).

[0005] In addition, in the power supply system, it is not permitted to reverse the power flow to the commercial power supply system side regardless of the number of installed power generation units. Therefore, a countermeasure of constantly purchasing power from the commercial power supply system is required.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] The demand of power demand facilities varies depending on the operating conditions of factories and the like. The demand increases during the operating hours and decreases during the shutdown hours. If the number of operating power generation units is reduced during the low demand period, the followability of power supply to the demand change may be impaired.

[0008] For example, since the SOFC unit operates the power generation module at 600 to 800 ° C, if it becomes cold due to the operation stop, it takes a very long time to restart. In addition, if the power generation module is kept warm and waiting for operation, not only the power generation efficiency is reduced due to fuel loss, but also a certain amount of time is required from the release of standby to obtaining the minimum output power. Therefore, it is not recommended to stop or standby a part of the power generation units during the low demand period.

[0009] The present invention has been made in view of the above problems, and an object thereof is to provide a power supply system capable of enhancing the followability of power supply to demand changes, and a method for determining the number of installed power generation units in the power supply system.

Means for Solving the Problems

[0010] The power supply system according to the present invention is operated in parallel with a commercial power supply system and includes a plurality of power generation units having the same rated output power. The rated output power of each of the plurality of power generation units is Qr [W], the reference purchase power preset to be always purchased from the commercial power supply system is Qs [W], and the demand power during a predetermined period in a power demand facility receiving power supply is D [W]. When a natural number obtained by truncating the decimal part of the numerical value obtained by the calculation (D - Qs) / Qr is n, the number of installed power generation units N of the plurality of power generation units satisfies the following formula (1). 2 ≦ N ≦ n …(1)

[0011] A method for determining the number of installed power generation units in a power supply system according to the present invention is a method for determining the number of installed power generation units in a power supply system including a plurality of power generation units having the same rated output power and operated in parallel with a commercial power supply system. The rated output power of each of the plurality of power generation units is Qr [W], the reference purchase power preset to be always purchased from the commercial power supply system is Qs [W], and the demand power during a predetermined period in a power demand facility receiving power supply is D [W]. When a natural number obtained by truncating the decimal part of the numerical value obtained by the calculation (D - Qs) / Qr is n, the number of installed power generation units N of the plurality of power generation units satisfies the following formula (1). 2 ≦ N ≦ n …(1)

Advantages of the Invention

[0012] According to the present invention, there are provided a power supply system capable of enhancing the followability of power supply with respect to demand changes in a power supply system, and a method for determining the number of installed power generation units in a power supply system.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying out the Invention

[0014] Hereinafter, each embodiment of the present invention will be described with reference to the drawings.

[0015] 〔First Embodiment〕 1.1 Outline of the Configuration of the Power Generation Unit First, the outline of the configuration of the power generation unit used in the power supply system according to the first embodiment will be described. FIG. 1 is a schematic diagram showing the configuration of the power generation unit according to the first embodiment. As shown in FIG. 1, the power generation unit 100 is of a type using a fuel cell, and includes a plurality of cell stacks 1, a reformer 2, a burner 3, an evaporator 4, an air preheater 5, an anode off-gas cooler 6, an anode off-gas condenser 7, a CO oxidizer (carbon monoxide oxidizer) 8, a condensate recovery tank 9, a first raw fuel blower 10, a first air blower 11, a water pump 12, a second raw fuel blower 13, a second air blower 14, a third air blower 15, a power conditioner 16, and a local controller 17.

[0016] In the example of this embodiment, a total of 8 cell stacks 1 are provided, including those not shown in FIG. 1.

[0017] The power generation unit 100 also includes lines (pipelines) such as a raw fuel line La, a mixed gas line Lb, an anode fuel line Lc, an anode off-gas line Ld, a cathode air line Le, a cathode off-gas line Lf, a combustion gas line Lg, a burner cooling air line Lh, a reformed water line Li, a startup air line Lj, a cooling air line Lk, and a condensate recovery line Lw.

[0018] The anode fuel line Lc includes a first distribution manifold Ma that serves as a main pipe for introducing anode fuel, and the cathode air line Le includes a second distribution manifold Mb that serves as a main pipe for introducing cathode air. These distribution manifolds Ma and Mb have an inlet and a plurality of outlets corresponding to each cell stack 1, and cause the fluid flowing into the inlet to flow out from each outlet.

[0019] The anode off-gas line Ld includes a first collection manifold Mc that serves as a main pipe for discharging anode off-gas, and the cathode off-gas line Lf includes a second collection manifold Md that serves as a main pipe for discharging cathode off-gas. These collection manifolds Mc and Md have a plurality of inlets and outlets corresponding to each cell stack 1, and cause the fluid flowing into each inlet to flow out from the outlet.

[0020] The combustion gas line Lg includes a heat radiation cylinder Za and a combustion gas pipe Zb. The cooling air line Lk includes a cooling pipe Zc and a collection pipe Lk1.

[0021] The raw fuel line La is a pipeline connecting the fuel intake port E1 and the burner 3, and a second raw fuel blower 13 is arranged in this pipeline. The second raw fuel blower 13 is a device that boosts the pressure of the raw fuel gas Gf (for example, methane-containing gas such as city gas 13A) taken in from the fuel intake port E1 and sends it to the downstream side of the raw fuel line La. Typically, it is driven during the startup operation of the power generation unit 100.

[0022] The mixed gas line Lb is a pipeline connecting the fuel inlet E2 and the reformer 2. In this pipeline, in order from the upstream side, a first raw fuel blower 10, an evaporator 4, and a first bellows type expansion joint B1 are arranged. The first raw fuel blower 10 is a device that boosts the raw fuel gas Ga taken in from the fuel inlet E2 and sends it to the downstream side of the mixed gas line Lb, and is typically driven during the power generation operation of the power generation unit 100.

[0023] The anode fuel line Lc is a pipeline connecting the reformer 2 and the anode of each cell stack 1. More specifically, the anode fuel line Lc includes, in order from the upstream side, a pipeline connecting the reformer 2 and the inlet of the first distribution manifold Ma, the first distribution manifold Ma, and eight pipelines (the branch pipes of the first distribution manifold Ma) connecting each outlet of the first distribution manifold Ma and the anode of each cell stack 1.

[0024] The anode off-gas line Ld is a pipeline connecting the anode of each cell stack 1 and the burner 3. More specifically, the anode off-gas line Ld includes, in order from the upstream side, eight pipelines (the branch pipes of the first collection manifold Mc) connecting the anode of each cell stack 1 and the inlets of the first collection manifold Mc, the first collection manifold Mc, and a pipeline (hereinafter referred to as "pipeline Ld1") connecting the outlet of the first collection manifold Mc and the burner 3. In the middle of the pipeline Ld1, in order from the upstream side, a second bellows type expansion joint B2, an anode off-gas cooler 6, an anode off-gas condenser 7, and a gas-liquid separation section Sa are arranged.

[0025] The cathode air line Le is a pipeline connecting the air inlet E3 and the cathode of each cell stack 1. More specifically, the cathode air line Le includes, in order from the upstream side, a pipeline (hereinafter referred to as "pipeline Le1") connecting the air inlet E3 and the inlet of the second distribution manifold Mb, the second distribution manifold Mb, and eight pipelines (the branch pipes of the second distribution manifold Mb) connecting each outlet of the second distribution manifold Mb and the cathode of each cell stack 1.

[0026] In the middle of pipeline Le1, in order from the upstream side, a first air blower 11, an anode off-gas cooler 6, an air preheater 5, and a third bellows type expansion joint B3 are arranged. The first air blower 11 is a device that pressurizes the air Aa taken in from the air intake E3 and sends it to the downstream side of the cathode air line Le, and is typically driven during the power generation operation of the power generation unit 100. Further, in the pipeline Le1, a bypass path Le2 that bypasses the anode off-gas cooler 6 and the air preheater 5 is provided so as to connect the midpoint between the air intake E3 and the anode off-gas cooler 6 and the midpoint between the air preheater 5 and the third bellows type expansion joint B3.

[0027] The cathode off-gas line Lf is a pipeline that connects the cathode of each cell stack 1 and the burner 3. More specifically, the cathode off-gas line Lf includes, in order from the upstream side, eight pipelines (the branch pipes of the second collection manifold Md) that connect the cathode of each cell stack 1 and the inlets of the second collection manifold Md, the second collection manifold Md, and a pipeline (hereinafter referred to as "pipeline Lf1") that connects the outlet of the second collection manifold Md and the burner 3.

[0028] The combustion gas line Lg is a pipeline that connects the burner 3 and the gas discharge port E6. More specifically, the combustion gas line Lg includes, in order from the upstream side, a heat radiation cylinder Za, a pipeline that connects the heat radiation cylinder Za and the combustion gas pipe Zb, the combustion gas pipe Zb, and a pipeline (hereinafter referred to as "pipeline Lg1") that connects the combustion gas pipe Zb and the gas discharge port E6. In the middle of the pipeline Lg1, in order from the upstream side, a fourth bellows type expansion joint B4, an air preheater 5, a CO oxidizer 8, and an evaporator 4 are arranged.

[0029] The burner cooling air line Lh is a pipe connecting the pipe line Le1 and the starting air line Lj, and a flow rate adjusting means (such as an orifice) (not shown) is provided in this pipe line. More specifically described, the burner cooling air line Lh branches at an intermediate point of the pipe line Le1 connecting the first air blower 11 and the anode off-gas cooler 6, and joins the starting air line Lj on the downstream side of the second air blower 14. It is configured such that a minute flow rate of air Ab flows toward the burner 3 when the first air blower 11 is driven.

[0030] The cooling air line Lk is a pipe connecting the air intake E5 and a predetermined location of the pipe line Lg1 (a location between the evaporator 4 and the gas discharge port E6), and in this pipe line, a third air blower 15 and a cooling pipe Zc are arranged in order from the upstream side. The third air blower 15 is a device that boosts the cooling air Ad taken in from the air intake E5 and sends it to the downstream side of the cooling air line Lk.

[0031] The reformed water line Li is a pipe connecting the condensed water recovery tank 9 and the evaporator 4, and a water pump 12 is arranged in this pipe line. The water pump 12 is a device that sends the condensed water Wb stored in the condensed water recovery tank 9 as reformed water Wa to the downstream side of the reformed water line Li.

[0032] The starting air line Lj is a pipe connecting the air intake E4 and the pipe line Lf1, and a second air blower 14 is arranged in this pipe line. The second air blower 14 is a device that boosts the air Ac taken in from the air intake E4 and sends it to the downstream side of the starting air line Lj, and is typically driven during the startup operation of the power generation unit 100.

[0033] The condensate recovery line Lw is a pipeline that connects the gas-liquid separation section Sa disposed in the middle of the pipeline Ld1 and the condensate recovery tank 9. The gas-liquid separation section Sa is a member that separates the condensate Wb generated in the anode off-gas condenser 7 from the anode off-gas Gd, and the separated condensate Wb flows down into the condensate recovery line Lw. The tip of the condensate recovery line Lw is opened to the gas phase part without being immersed in the aqueous phase part of the condensate recovery tank 9 so that the condensate amount does not increase or decrease under the influence of the water temperature of the stored condensate Wb. Note that the tip of the condensate recovery line Lw is not immersed in the aqueous phase part in order not to change the flow rate of the anode off-gas Gd sent to the burner 3. In particular, this configuration is effective when the anode off-gas Gd after separating the condensate Wb is recycled to the primary side of the cell stack or used for power generation in the subsequent cell stack. For the gas-liquid separation section Sa, for example, a T-shaped pipe with a straight pipe section arranged horizontally and a branch pipe section arranged downward is used. Also, a small-capacity cylindrical container erected in the vertical direction can be used as the gas-liquid separation section Sa.

[0034] The cell stack 1 is a power generation body composed of a solid oxide fuel cell (SOFC). The solid oxide fuel cell is a high-temperature operating fuel cell in which the solid electrolyte, anode, and cathode constituting the power generation cell are all ceramics, and a power generation unit in which a predetermined number of power generation cells are integrated via a metal interconnect material (also referred to as a separator material) is called a cell stack. The battery output of the cell stack 1 is supplied with power after being adjusted by the power conditioner 16.

[0035] The reformer 2 reforms the raw fuel gas Ga using steam to generate a reformed gas Gc and sends it to the subsequent stage. The reformer 2 has a catalyst for steam reforming, reacts methane contained in the raw fuel gas Ga with steam, and generates a reformed gas Gc containing carbon monoxide and hydrogen. Although steam reforming is an endothermic reaction, the reformer 2 can stably generate the reformed gas Gc by heat supply from the burner 3.

[0036] The burner 3 burns the inflowing gas to generate heat and discharges the combustion gas Gg generated by the combustion into the combustion gas line Lg. The evaporator 4 is a device that indirectly heat-exchanges the reformed water Wa and the combustion gas Gg (heat source fluid). By heat-exchanging with the combustion gas Gg, it evaporates the reformed water Wa and at the same time plays a role in heating the raw fuel gas Ga.

[0037] The air preheater 5 and the anode off-gas cooler 6 are both heat exchangers that indirectly heat-exchange a low-temperature fluid and a high-temperature fluid. The air preheater 5 plays a role in preheating the air Aa in the cathode air line Le by heat-exchanging with the combustion gas Gg, and the anode off-gas cooler 6 plays a role in cooling the anode off-gas Gd by heat-exchanging with the air Aa in the cathode air line Le.

[0038] The anode off-gas condenser 7 uses the fan 7a to cool the anode off-gas Gd and condenses the water vapor contained in the anode off-gas Gd. Note that the anode off-gas condenser 7 of this embodiment is an air-cooled heat exchanger, but instead, a water-cooled heat exchanger may be adopted, and thus it may be a cogeneration type power generation unit in which heat recovery is performed.

[0039] The CO oxidizer 8 is a device that brings the harmful carbon monoxide contained in the combustion gas Gg into contact with a catalyst and converts it into harmless carbon dioxide. The CO oxidizer 8 does not operate when the oxidation reaction in the burner 3 is complete, and operates only when the oxidation reaction in the burner 3 is incomplete.

[0040] The condensate recovery tank 9 recovers the condensate Wb discharged from the gas-liquid separation section Sa and serves to make it reusable as reformed water Wa. In the condensate recovery tank 9, a water level detector Sb and a drain valve Sc are provided to adjust the water level of the stored reformed water Wa within a predetermined range. When the water level detector Sb detects the upper limit water level, the drain valve Sc is opened, while when the water level detector Sb detects the lower limit water level, the drain valve Sc is closed. In this way, the condensate recovery tank 9 is ensured to have the required amount of reformed water Wa. In addition, in order to prevent the anode off-gas Gd from leaking to the outside during the drainage operation of the reformed water Wa, the drainage position by the drain valve Sc is set near the bottom of the condensate recovery tank 9.

[0041] Also, as shown by the dashed line frame in Fig. 1, each cell stack 1, reformer 2, burner 3, each manifold Ma to Md, heat radiation cylinder Za, combustion gas pipe Zb, and cooling pipe Zc are arranged in the first region R1. The first region R1 is maintained at a temperature exceeding 600 °C during the power generation operation of the power generation unit 100 and independently maintains the heat balance of heat absorption and heat generation. On the other hand, the evaporator 4, air preheater 5, anode off-gas cooler 6, and CO oxidizer 8 are arranged in the second region R2. The second region R2 is maintained at a temperature lower than that of the first region R1 and higher than room temperature during the power generation operation of the power generation unit 100. The first region R1 and the second region R2 are each surrounded by a heat insulation box, and the power generation module 20 is formed by integrating the two heat insulation boxes. The anode off-gas condenser 7, condenser fan 7a, condensate recovery tank 9, each blower 10, 11, 13, 14, 15, water pump 12, power conditioner 16, and local controller 17 are arranged outside the power generation module 20 (room temperature region). In addition, the above-mentioned bellows-shaped expansion pipe joints B1 to B4 are used to absorb the expansion and contraction of the pipes caused by the temperature change between the cold state and the operation state.

[0042] FIG. 2 is a schematic diagram showing the configuration of the power conditioner 16 according to the present embodiment, and shows the internal configuration of the power conditioner 16 and the connection state to peripheral devices. The power generation module 20 is configured to include elements such as the cell stack 1 as described above. Further, the auxiliary machine 30 for operating the power generation module 20 includes components such as the raw fuel blowers 10 and 13, the air blowers 11, 14, and 15, the water pump 12, and the fan 7a of the anode off-gas condenser 7.

[0043] The power conditioner 16 converts the generated power of the power generation module 20 into output power corresponding to the AC power of the commercial power supply system 500. The power conditioner 16 includes DC / DC converters 16a and 16b, a smoothing capacitor 16c, a grid-connected inverter 16d, switches 16e and 16f, and control circuits 16g and 16h.

[0044] The DC / DC converter 16a boosts and converts the DC power from the power generation module 20 (boosting circuit). The smoothing capacitor 16c smoothes the output power of the DC / DC converter 16a. The grid-connected inverter 16d converts the output power of the DC / DC converter 16a into AC power equivalent to the commercial power supply system.

[0045] The output side of the grid-connected inverter 16d is electrically connected to, for example, a distribution board 610 for receiving commercial power installed in a building. The grid-connected inverter 16d and the distribution board 610 can be switched between a parallel state and a disconnection state via the switch 16e. The commercial power supply system 500 and the power demand facility 600 are electrically connected to the distribution board 610. The power demand facility 600 includes a plurality of sub-distribution boards, and load devices such as lighting fixtures, power units, or outlets used in the building are electrically connected to each sub-distribution board.

[0046] In addition, the grid-connected inverter 16d is electrically connected to the independent outlet 300. The grid-connected inverter 16d and the independent outlet 300 can be switched between a connected state and a disconnected state via the switch 16f. The independent outlet 300 is composed of a plurality of outlets into which the power plugs of various power-consuming devices can be inserted.

[0047] The DC / DC converter 16b and the control circuit 16g function as a driving power supply unit that supplies driving power to the auxiliary machine 30. The DC / DC converter 16b adjusts the DC voltage boosted by the DC / DC converter 16a to a DC voltage suitable for driving the auxiliary machine 30. The control circuit 16g supplies the DC voltage adjusted by the DC / DC converter 16b to the auxiliary machines 30 to appropriately drive the auxiliary machine 30. Note that the above-mentioned auxiliary machine 30 is driven using commercial power during the startup operation and shutdown operation of the power generation unit 100, and is driven using the generated power during the power generation operation of the power generation unit 100.

[0048] The DC / DC converter 16a and the control circuit 16h function as an operating power supply unit that supplies operating power to the load module 40. The load module 40 includes an electric heater 41 and a radiator fan 42. In the independent operation mode of the power generation unit 100, the load module 40 causes the electric heater 41 to generate heat to consume the excess generated power of the cell stack 1, and the radiator fan 42 sends an air flow to the electric heater 41 to promote heat dissipation. Note that the load module 40 is disposed, for example, inside or outside the housing of the power generation unit 100.

[0049] The local controller 17 controls the operation of the power generation unit 100 according to a control program created and stored in advance. The local controller 17 is provided with a communication unit 17a that communicates with the outside of the power generation unit 100. In addition, a current sensor 200, which will be described later, is connected to the local controller 17. The details of the local controller 17 will be described later as needed.

[0050] 1.2 Outline of the operation of the power generation unit Next, the general operation of the power generation unit 100 will be described with reference to FIG. 1. The raw fuel gas Ga supplied into the mixed gas line Lb from the fuel inlet E2 is sent to the subsequent stage by the action of the first raw fuel blower 10. In parallel with the supply of the raw fuel gas Ga, the reformed water Wa supplied into the reformed water line Li from the condensate recovery tank 9 has its water volume adjusted by the water pump 12 and flows into the mixed gas line Lb.

[0051] The reformed water Wa flows into the evaporator 4 together with the raw fuel gas Ga in the mixed gas line Lb, and is heated by heat exchange in the evaporator 4 to become water vapor (superheated steam). The water vapor is mixed with the heated raw fuel gas Ga and flows into the reformer 2 as the mixed gas Gb.

[0052] The reformer 2 reforms the raw fuel gas Ga using the water vapor in the mixed gas Gb, generates the reformed gas Gc, and sends it to the subsequent stage. The reformed gas Gc sent out from the reformer 2 is distributed to the anodes of the respective cell stacks 1 through the anode fuel line Lc.

[0053] On the other hand, in parallel with the supply of the above-mentioned raw fuel gas Ga, air Aa is supplied into the cathode air line Le from the air inlet E3. The air Aa in the cathode air line Le is sent to the subsequent stage by the action of the first air blower 11. This air Aa is heated by heat exchange in the anode off-gas cooler 6 and further heated by heat exchange in the air preheater 5, and then distributed to the cathodes of the respective cell stacks 1. In addition, in order to adjust the temperature of the air Aa, etc., it is also possible to make a part of the air Aa, i.e., the air Aa1, flow into the cathodes of the respective cell stacks 1 through the bypass path Le2.

[0054] Furthermore, in synchronization with the supply of the air Aa to the cathode, air Ab is supplied into the burner cooling air line Lh. The air Ab in the burner cooling air line Lh is sent to the burner 3 by the action of the first air blower 11. This air Ab acts as a coolant for reducing the combustion temperature of the burner 3.

[0055] Each cell stack 1 generates electricity using the reformed gas Gc flowing into the anode and the air Aa flowing into the cathode. When current sweeping by the power conditioner 16 is executed with the reformed gas Gc and the air Aa supplied to the cell stack 1, power generation (electrochemical reaction of the reformed gas and oxygen) of the cell stack 1 is started. During the power generation operation of the cell stack 1, the anode off-gas Gd is discharged from the anode to the anode off-gas line Ld, and the cathode off-gas Ge is discharged from the cathode to the cathode off-gas line Lf. The anode off-gas Gd contains the reformed gas that was unreacted at the anode, and the cathode off-gas Ge contains the oxygen that was unreacted at the cathode.

[0056] The anode off-gas Gd discharged from each cell stack 1 to the anode off-gas line Ld is collected in the first collection manifold Mc, then cooled by heat exchange in the anode off-gas cooler 6, and flows into the anode off-gas condenser 7. In the anode off-gas condenser 7, the anode off-gas Gd is cooled to below the dew point temperature, and the water vapor contained in the anode off-gas Gd condenses.

[0057] The anode off-gas Gd that has passed through the anode off-gas condenser 7 is sent to the gas-liquid separation section Sa for gas-liquid separation, and the condensed water Wb is recovered in the condensed water recovery tank 9. The condensed water Wb recovered in the condensed water recovery tank 9 is reused as the reformed water Wa as described above. Note that the non-condensed portion (the anode off-gas Gd after gas-liquid separation) in the anode off-gas Gd is sent to the burner 3.

[0058] The cathode off-gas Ge discharged from each cell stack 1 to the cathode off-gas line Lf is collected in the second collection manifold Md, then mixed with the air Ab flowing in through the burner cooling air line Lh in the pipeline Lf1, and sent to the burner 3. Also, to the burner 3, according to the operating state of the power generation unit 100, the raw fuel gas Gf supplied from the fuel inlet E1 is sent through the raw fuel line La, and the air Ac supplied from the air inlet E4 is sent through the starting air line Lj.

[0059] The burner 3 has the gas Gx for the first burner, which is the raw fuel gas Gf and / or the anode off-gas Gd, and the gas Gy for the second burner, which is the air Ac and / or the cathode off-gas Ge, flowing therein, and burns these to generate heat. That is, the gas Gx for the first burner is a mixture of the raw fuel gas Gf and the anode off-gas Gd, or is in a state of either the raw fuel gas Gf or the anode off-gas Gd, and which state it is in can vary depending on the operating state of the power generation unit 100 or the like. Also, the gas Gy for the second burner is a mixture of the air Ac and the cathode off-gas Ge, or is in a state of either the air Ac or the cathode off-gas Ge, and which state it is in can vary depending on the operating state of the power generation unit or the like. That is, according to the startup operation, power generation operation (full load operation or partial load operation), shutdown operation, etc. of the power generation unit 100, the supply gas to the burner 3 appropriately changes its state.

[0060] Note that the raw fuel gas Gf is a type of hydrocarbon-containing gas. On the other hand, the air Ac is a type of oxidant-containing gas. During the combustion operation of the burner 3, air Ab is continuously supplied from the burner cooling air line Lh, and the combustion temperature is adjusted.

[0061] The combustion gas Gg generated by the combustion in the burner 3 is sent to the combustion gas line Lg, passes through the heat radiation cylinder Za, the combustion gas pipe Zb, the air preheater 5, the CO oxidizer 8, and the evaporator 4 in sequence, and is discharged from the gas discharge port E6 to the outside of the power generation module 20. The heat radiation cylinder Za and the combustion gas pipe Zb are arranged so as to be able to effectively heat the reformer 2 using the combustion gas Gg. Also, the combustion gas Gg in the combustion gas line Lg is used for heat exchange when passing through the air preheater 5 and the evaporator 4, and when carbon monoxide is contained, the carbon monoxide is converted to carbon dioxide when passing through the CO oxidizer 8.

[0062] In addition, the cooling air Ad supplied from the air intake E5 to the cooling air line Lk serves to cool the interior of the power generation module 20 when passing through the cooling pipe Zc. As will be described later, the cooling pipe Zc is installed in the vicinity of the cell stack 1, and the cell stack 1 can be effectively cooled by the cooling air Ad. Then, the cooling air Ad finally passes through the collecting pipe Lk1 and is discharged to the outside of the power generation module 20 from the gas outlet E6 together with the combustion gas Gg.

[0063] Also, in the power generation unit 100, the amount of heat (temperature) inside the power generation module 20 is controlled by adjusting the flow rate of the cooling air Ad introduced into the cooling pipe Zc. As an example, when the discharge temperature of the cathode off-gas Ge flowing out from the cell stack 1 exceeds the upper limit temperature, the local controller 17 drives the third air blower 15, and controls the rotation speed of the third air blower 15 so that the discharge temperature of the cathode off-gas Ge becomes the target temperature (a temperature lower than the upper limit temperature by a predetermined temperature). The greater the rotation speed of the third air blower 15 increases, the greater the flow rate of the cooling air Ad introduced into the cooling pipe Zc increases. Further, when the rotation speed below the lower limit value continues for a predetermined time, the local controller 17 stops the third air blower 15.

[0064] Note that the cooling pipe Zc installed near the cell stack 1 can also be used to heat up the cell stack 1 during the startup operation of the power generation unit 100. Specifically, in the startup operation of the power generation unit 100, first, the second raw fuel blower 13 and the second air blower 14 are driven to burn the burner 3. The combustion gas Gg generated by this combustion flows through the heat radiation cylinder Za and the combustion gas pipe Zb, while heating the cold reformer 2 from the outside by radiative heat transfer to raise its temperature. Further, the combustion gas Gg becomes the heat source of the evaporator 4, generating steam from the reforming water Wa. This steam flows through the cold reformer 2 and the cell stack 1 in sequence, heating these devices from the inside by heat conduction to raise their temperatures. If there is waste heat in the combustion gas Gg discharged from the evaporator 4, the combustion gas Gg is allowed to flow from the pipeline Lg1 into the collecting pipe Lk1. As a result, the combustion gas Gg flows through the cooling pipe Zc, so that the cold cell stack 1 can be heated from the outside by radiative heat transfer to raise its temperature.

[0065] In the power generation operation of the power generation unit 100, balancing the heat balance among the heat generation due to the electrochemical reaction between the reformed gas Gc and oxygen in the cell stack 1, the heat generation due to the combustion reaction between the anode off-gas Gd and the cathode off-gas Ge in the burner 3, and the heat absorption due to the steam reforming reaction between the raw fuel gas Ga and steam (reforming water Wa) in the reformer 2 is called "thermal self-sufficiency". Also, recovering the water (reforming water Wa) generated by the electrochemical reaction between the reformed gas Gc and oxygen and repeatedly using it in the steam reforming reaction is called "water self-sufficiency".

[0066] In the power generation operation of the power generation unit 100, the output power of the grid-connected inverter 16d is equal to the value obtained by subtracting the total power losses due to the operation of the auxiliary machine 30, the power losses due to the operation of the power conditioner 16, and the power losses due to the operation of the load module 40. The load module 40 operates in the self-powered operation mode described later.

[0067] When the power generation unit 100 is operating at full load with the rated output power, the local controller 17 sets the sweep current value for the cell stack 1 to the rated current value and supplies an amount of raw fuel gas Ga corresponding thereto. When the power generation unit 100 is operating at a partial load below the rated output power and above the minimum output power, the local controller 17 sets the sweep current value for the cell stack 1 to a range less than the rated current value and not less than the lower limit current value, and supplies an amount of raw fuel gas Ga corresponding thereto. When the power generation unit 100 is waiting with zero output power, the local controller 17 sets the sweep current value for the cell stack 1 to the value corresponding to the operating power of the auxiliary machine 30, and keeps the power generation module 20 warm while supplying the minimum amount of raw fuel gas Ga. Note that the state in which the power generation unit 100 is waiting with zero output power is referred to as "hot standby".

[0068] The power generation operation of the power generation unit 100 includes an interconnected operation mode and an independent operation mode. In the interconnected operation mode, as shown in FIG. 2, the switch 16e is controlled to be in the on state and the switch 16f is controlled to be in the off state. Thereby, the power generation unit 100 is operated in parallel with the commercial power supply system 500. In the independent operation mode, contrary to FIG. 2, the switch 16e is controlled to be in the off state and the switch 16f is controlled to be in the on state. Thereby, the power generation unit 100 is operated in a disconnected state from the commercial power supply system 500.

[0069] The local controller 17 constantly monitors the presence or absence of a power outage in the commercial power supply system 500, and when a power outage is detected, shifts the power generation unit 100 from the interconnected operation mode to the independent operation mode. In the independent operation mode, when an electrical device is connected to the independent outlet 300, it is possible to supply the output power of the system interconnection inverter 16d to the electrical device as the independent operation power. When the commercial power supply system 500 resumes power after a power outage, the local controller 17 shifts the power generation unit 100 from the independent operation mode to the interconnected operation mode.

[0070] When the supply amount of the self-driving power exceeds the consumption amount in the self-driving mode, the power generation unit 100 causes the load module 40 to consume the surplus of the self-driving power. The adjustment of the power consumption amount of the load module 40 can be realized by adjusting the calorific value of the electric heater 41 (for example, the number of heaters to be energized, or the adjustment of the on / off duty ratio of the energization).

[0071] 2.1 Configuration Overview of Power Supply System Next, the configuration overview of the power supply system according to the present embodiment will be described. FIG. 3 is a schematic diagram showing the configuration of the power supply system according to the present embodiment. As shown in FIG. 3, the power supply system (fuel cell system) 1000 includes a plurality of power generation units 100 that are operated in parallel (system connection mode) with respect to the commercial power supply system 500, and a system controller 18 that comprehensively controls the control states of each machine. The power supply system 1000 supplies the total output power obtained by adding up the output powers of each power generation unit 100 to the power demand facility 600.

[0072] <Number of Installed Power Generation Units> The number of installed power generation units N of the power generation unit 100 is determined so as not to generate reverse power flow in a state where all the power generation units 100 are operating at the rated output power (that is, a state where the power supply system 1000 is operating at the maximum supplyable power). Specifically, the number of installed units N is such that the rated output power of each power generation unit 100 is Qr [W], the reference purchase power preset to be always purchased from the commercial power supply system 500 is Qs [W], and the demand power for a predetermined period in the power demand facility 600 is D [W]. When the natural number obtained by truncating the decimal part of the value obtained by the calculation (D - Qr) / Qs is n, it is determined so as to satisfy the following formula (1). 2 ≤ N ≤ n …(1)

[0073] Here, the predetermined period for grasping the demand power D targets at least one week and at most one year, and it is desirable not to include low-demand periods (such as nights and holidays) when the operation of factories and the like is suspended. By grasping the demand power D during high-demand periods when the operation of factories and the like is being carried out, during high-demand periods, N power generation units 100 can be operated at the rated output power.

[0074] Also, in the first embodiment, it is desirable to set the demand power D as the minimum demand power D1 [W] during a predetermined period in the power demand facility 600. That is, when the natural number obtained by truncating the decimal part of the value obtained by the calculation (D1 - Qs) / Qr is n1, the installation number N is determined to satisfy the following formula (2). 2 ≤ N ≤ n1 …(2)

[0075] For example, when the rated output power Qr = 6 kW, the reference purchase power Qs = 2 kW, and the minimum demand power D1 = 27 kW, n1 is calculated as 4. Therefore, according to formula (2), the installation number N is estimated to be 2 to 4 units. Here, in order to take advantage of the merit of self-generation of minimizing the purchase power cost, it is desirable to select 4 units, which is the maximum number, within the estimated range of the installation number N.

[0076] The calculation tool for determining the above-mentioned installation number N is not particularly limited. For example, it may be realized by using the required software or executing a program on a personal computer.

[0077] FIG. 5 is a reference diagram showing the relationship between the time-series change of the demand power D for a predetermined period (e.g., 12 days) and the minimum demand power D1. When the number of installed units N is determined so as to satisfy Equation (2), the sum (H + Qs) of the maximum supplyable power H obtained by multiplying the rated output power Qr of each power generation unit 100 by the number of installed units N and the reference purchase power Qs becomes the base load power to the power demand facility 600. When the demand of the power demand facility 600 exceeds the base load power, the power additionally purchased from the commercial power supply system 500 becomes the peak load power. When D1 < H + Qs due to a decrease in the demand of the power demand facility 600, each power generation unit 100 operates at partial load.

[0078] In the present embodiment, as shown in FIG. 3, the power supply system 1000 includes a first power generation unit 101, a second power generation unit 102, a third power generation unit 103, and a fourth power generation unit 104. Each of the power generation units 101 to 104 has the same rated output power. For example, if the rated output power of each is 6 kW, the power supply system 1000 can supply a total output power of up to 24 kW.

[0079] <Operation as an output adjuster> As described above, the power generation unit 100 can be operated at full load with the rated output power, at partial load with a power less than the rated output power and equal to or greater than the minimum output power, or in hot standby with the output power zero. That is, each of the power generation units 101 to 104 can be operated as an output adjuster that operates within a range equal to or less than the rated output power and equal to or greater than the minimum output power. Since the power generation module 20 in the present embodiment includes an SOFC cell stack, the minimum output power in partial load operation is set based on the minimum fuel supply amount that can maintain the heat self-sufficiency of the power generation module 20 and the minimum fuel utilization rate that can maintain the water self-sufficiency of the power generation module 20.

[0080] The maximum output power of the power generation unit 100 in the grid-connected operation mode is equivalent to the rated output power (6 kW). Also, the minimum output power of the power generation unit 100 in the grid-connected operation mode is set to the lower limit value at which, in addition to achieving both heat self-sufficiency and water self-sufficiency, there is no decrease in the power generation efficiency during partial load operation compared to that during full load operation. In this case, the minimum output power is, for example, equivalent to 50% (3 kW) of the rated output power (6 kW). When output adjustment below the minimum output power is required, the system will shift to hot standby.

[0081] The output adjuster adjusts the output power from the power conditioner 16 by performing operations to increase and decrease the output current from the grid-connected inverter 16d. The local controller 17 increases the sweep current value for the cell stack 1 in parallel with the increase in the output current and increases the supply amount of the raw fuel gas Ga. Also, the local controller 17 decreases the sweep current value for the cell stack 1 in parallel with the decrease in the output current and decreases the supply amount of the raw fuel gas Ga. Thereby, the power generation power of the power generation module 20 increases or decreases as the output current increases or decreases.

[0082] <Local Controller> Each of the local controllers 17 installed in the power generation units 101 to 104 is constituted by a programmable logic controller (PLC). The PLC has an arithmetic unit, a storage unit, an input unit, an output unit, and a power supply unit, and executes required arithmetic operations and sequence control using a processing program created and stored in advance. Note that the current sensor 200 described later is connected to the input unit of the PLC.

[0083] Each of the local controllers 17 is configured to be capable of executing output adjustment control for adjusting the output power of the power conditioner 16 within a range equal to or lower than the rated output power and equal to or higher than the minimum output power, based on information regarding the purchased power from the commercial power supply system 500. The output adjustment control includes heteronomous output adjustment control for heteronomously adjusting the output power and autonomous output adjustment control for autonomously adjusting the output power. The details of the heteronomous output adjustment control and the autonomous output adjustment control will be described later.

[0084] <System controller> Each of the local controllers 17 mounted on the power generation units 101 to 104 has a system control unit that can function as a system controller 18. This system control unit is a functional block incorporated in the PLC.

[0085] In the present embodiment, the power generation units 101 to 104 are classified into one master unit and the remaining slave units. Specifically, the first power generation unit 101 is the master unit, and the second power generation unit 102, the third power generation unit 103, and the fourth power generation unit 104 are the slave units.

[0086] The system control unit in the first power generation unit 101 designated as the master unit is activated as the system controller 18. On the other hand, each of the system control units in the second power generation unit 102, the third power generation unit 103, and the fourth power generation unit 104 designated as the slave units is deactivated as the system controller 18. As a result, the system controller 18 of the master unit is configured to comprehensively control the control states of the master unit and the slave units.

[0087] <Information communication function> The system controller 18 of the master unit and the local controller 17 of the master unit can exchange information with each other inside the PLC. Also, the system controller 18 of the master unit and the local controller 17 of the slave unit can communicate with each other via the communication unit 17a attached to the PLC.

[0088] Each of the local controllers 17 continuously transmits information regarding the control state and output state of its own device (e.g., the sweep current value for the cell stack 1, the output power of the grid-connected inverter 16d, etc.) to the system controller 18. The system controller 18 uses this information received from each of the local controllers 17 to coordinate the heteronomous output adjustment control and autonomous output adjustment control of the output adjuster.

[0089] <Current sensor> The power supply system 1000 includes a current sensor 200 that detects the forward power flow current flowing from the commercial power supply system 500 to the power demand facility 600. The current sensor 200 consists of a first current sensor 201 associated with the first power generation unit 101 which is the master unit, a second current sensor 202 associated with the second power generation unit 101 which is a slave unit, a third current sensor 203 associated with the third power generation unit 103 which is a slave unit, and a fourth current sensor 204 associated with the fourth power generation unit 104 which is a slave unit. The detection units of each of the current sensors 201 - 204 are disposed on the power transmission cable from the commercial power supply system 500 to the power demand facility 600, at a position upstream of the connection points P1 - P4 of the output cables of each of the power generation units 101 - 104.

[0090] The detection information (current value information) of each of the current sensors 201 - 204 is input into the local controllers 17 of the corresponding power generation units 101 - 104. In the master unit, the detection information is shared between the local controller 17 and the system controller 18.

[0091] 2.2 Outline of Control of Power Supply System The power supply system 1000 causes the output adjustment control to be executed for each of the power generation units 101 to 104 using the setting information regarding the reference purchased power. Each of the system controller 18 and the local controller 17 calculates in real time the monitored value of the actual purchased power Qm from the commercial power supply system 500 based on the detection information (current value information) input from the corresponding current sensor 201 and the AC voltage value (for example, 100V) of the commercial power supply system 500. Hereinafter, the heteronomous output adjustment control and the autonomous output adjustment control executed by each of the local controllers 17 will be briefly described.

[0092] 〔1a〕 When the system controller 18 determines that the actual purchased power Qm is lower than the first reference purchased power Q1 (for example, 2 kW) and thus a relatively slow demand decrease that is lower than the minimum required power D, the system controller 18 causes each of the local controllers 17 to execute the first output decrease control so as to increase the actual purchased power Qm up to the second reference purchased power Q2 (for example, 8 kW). The first output decrease control belongs to the heteronomous output adjustment control that follows the request from the system controller 18, and the local controller 17 decreases the output current from the system connection inverter 16d by the specified output current decrease width.

[0093] 〔1b〕 When the system controller 18 determines that the actual purchased power Qm is higher than the second reference purchased power Q2 (for example, 8 kW) and thus a demand increase, the system controller 18 causes each of the local controllers 17 to execute the output increase control so as to decrease the actual purchased power Qm within the range from the first reference purchased power Q1 to the second reference purchased power Q2 (for example, 7.5 kW). The output increase control belongs to the heteronomous output adjustment control that follows the request from the system controller 18, and the local controller 17 increases the output current from the system connection inverter 16d by the specified output current increase width.

[0094] 〔2a〕When each of the local controllers 17 determines that the actual purchased power Qm falls below the minimum demand power D1 due to the actual purchased power Qm falling below the third reference purchased power Q3 (for example, 0.5 kW), it executes the second output reduction control to recover the actual purchased power Qm to the third reference purchased power Q3. The second output reduction control belongs to the autonomous output adjustment control that does not depend on the request from the system controller 18, and the local controller 17 gradually reduces the output current from the grid-connected inverter 16d by a predetermined adjustment width.

[0095] 〔2b〕After the end of the second output reduction control, the system controller 18 causes each of the local controllers 17 to execute the third output reduction control to increase the actual purchased power Qm to the second reference purchased power Q2 (for example, 8 kW). The third output reduction control belongs to the heteronomous output adjustment control that follows the request from the system controller 18, and the local controller 17 reduces the output current from the grid-connected inverter 16d by the specified reduced output current width.

[0096] 〔Second Embodiment〕 In the second embodiment, it is different from the first embodiment in that the demand power D is the average demand power D2 [W] during a predetermined period in the power demand facility 600. That is, when the natural number obtained by truncating the decimal part of the value obtained by the calculation (D2 - Qs) / Qr is n2, the installation number N is determined to satisfy the following formula (3). 2 ≦ N ≦ n2 …(3)

[0097] For example, when the rated output power Qr = 6 kW, the reference purchased power Qs = 2 kW, and the average demand power D2 = 34 kW, n2 is calculated as 5. Therefore, according to formula (2), the installation number N is estimated to be 2 to 5 units. Here, in order to take advantage of the merit of self-generation of minimizing the purchased power cost, it is desirable to select the maximum number n2, which is 5 units, from the estimated range of the installation number N.

[0098] FIG. 6 is a reference diagram showing the relationship between the time-series change of the demand power D for a predetermined period (for example, 12 days) and the average demand power D2. When the number of installed units N is determined so as to satisfy Equation (3), the sum (H + Qs) of the maximum supply power H obtained by multiplying the rated output power Qr of each power generation unit 100 by the number of installed units N and the reference purchase power Qs becomes the base load power to the power demand facility 600. When the demand of the power demand facility 600 exceeds the base load power, the power additionally purchased from the commercial power supply system 500 becomes the peak load power. Note that when D2 < H + Qs due to a decrease in the demand of the power demand facility 600, each power generation unit 100 operates at a partial load.

[0099] 〔Third Embodiment〕 In the third embodiment, it is different from the first and second embodiments in that the demand power D is set as the maximum demand power D3 [W] for a predetermined period in the power demand facility 600. That is, when the natural number obtained by truncating the decimal part of the numerical value obtained by the calculation (D3 - Qs) / Qr is n3, the number of installed units N is determined so as to satisfy the following equation (4). 2 ≦ N ≦ n3 …(4)

[0100] For example, when the rated output power Qr = 6 kW, the reference purchase power Qs = 2 kW, and the maximum demand power D3 = 40 kW, n3 is calculated to be 6. Therefore, according to Equation (2), the number of installed units N is estimated to be 2 to 6 units. Here, in order to take advantage of the merit of self-generation of minimizing the purchase power cost, it is desirable to select 6 units, which is the maximum number n3, from the estimated range of the number of installed units N.

[0101] FIG. 7 is a reference diagram showing the relationship between the time-series change of the demand power D for a predetermined period (e.g., 12 days) and the maximum demand power D3. When the number of installed units N is determined so as to satisfy the formula (4), the total (H + Qs) of the maximum supply power H obtained by multiplying the rated output power Qr of each power generation unit 100 by the number of installed units N and the reference purchase power Qs becomes the base load power to the power demand facility 600. When the demand of the power demand facility 600 exceeds the base load power, the power additionally purchased from the commercial power supply system 500 becomes the peak load power. When D3 <H + Qs due to a decrease in the demand of the power demand facility 600, each power generation unit 100 is operated at a partial load.

[0102] 〔Other Modification Examples〕 The cell stack 1 constituting the power generation module 20 may be a molten carbonate fuel cell (MCFC) instead of a solid oxide fuel cell (SOFC). The MCFC is a high-temperature operating fuel cell like the SOFC and has high power generation efficiency.

[0103] The power generation module 20 using a fuel cell is not limited to the type that generates power with a single-stage cell stack 1, and may be a type that generates power with two or more stages of cell stacks 1. Specifically, water vapor is removed from the anode off-gas discharged from the front-stage cell stack to generate a regenerated gas, and this regenerated gas is supplied to the anode of the next-stage cell stack. In generating the regenerated gas, carbon dioxide contained in the anode off-gas may be removed using a separation membrane, an absorbent, or the like. By configuring to generate power with two or more stages of cell stacks, the fuel utilization rate can be significantly increased.

[0104] The power generation module 20 using a fuel cell is not limited to a configuration that supplies reformed gas to the cell stack, and may be configured to supply pure hydrogen gas. Specifically, hydrogen gas supplied from an external hydrogen production site through a transportation infrastructure is introduced into the anode of the cell stack. When hydrogen gas is used as the primary fuel, components necessary for steam reforming and water self-sufficiency (such as reformer 2, evaporator 4, anode off-gas condenser 7, gas-liquid separation unit Sa, condensed water recovery tank 9, water pump 12, etc.) can be omitted.

[0105] The power generation unit 100 is not limited to a type using a fuel cell, and can also be changed to other types. The power generation unit may be of a type using a solar cell, or may be of a type that rotates a generator using an organic Rankine cycle, a steam turbine, a gas turbine, or a gas engine.

[0106] The system controller 18 may be a functional block incorporated in the local controller 17 (PLC), but can also be an independent controller separated from the local controller 17. In this case, each of the local controllers 17 is connected to the system controller 18 via a communication unit 17a.

[0107] A part of the control functions executed by the local controller 17 (PLC) can also be configured to be executed by a built-in controller equipped in the power conditioner 16. In this case, the built-in controller is substantially a component of the local controller 17. For example, monitoring of power outages and power restorations, and instructions for transitioning between the grid-connected operation mode and the self-sufficient operation mode may be control functions executed by the built-in controller.

[0108] According to the power supply system 1000 of the present embodiment described above, the following effects are achieved.

[0109] (1) The power supply system 1000 operates in parallel with the commercial power supply system 500 and includes a plurality of power generation units 100 having the same rated output power. Let the rated output power of each of the plurality of power generation units 100 be Qr [W], the reference purchase power preset to always purchase from the commercial power supply system 500 be Qs [W], and the demand power during a predetermined period in the power demand facility 600 receiving power supply be D [W]. When the natural number obtained by truncating the decimal part of the value obtained by the calculation (D - Qs) / Qr is n, the number of installed units N of the plurality of power generation units 100 satisfies the following formula (1). 2 ≦ N ≦ n …(1)

[0110] (2) A method for determining the number of installed units of the power generation unit 100 in the power supply system 1000 composed of a plurality of power generation units 100 operating in parallel with the commercial power supply system 500 and having the same rated output power. Let the rated output power of each of the plurality of power generation units 100 be Qr [W], the reference purchase power preset to always purchase from the commercial power supply system be Qs [W], and the demand power during a predetermined period in the power demand facility receiving power supply be D [W]. When the natural number obtained by truncating the decimal part of the value obtained by the calculation (D - Qs) / Qr is n, the number of installed units N of the plurality of power generation units satisfies the following formula (1). 2 ≦ N ≦ n …(1)

[0111] If the total of the maximum supplyable power H obtained by multiplying the rated output power Qr of each power generation unit 100 by the number of installed units N and the reference purchase power Qs is used as the base load power, the number of installed units N is determined such that the base load power is less than the demand power D. Therefore, it is expected that all the power generation units 100 can be operated at full load or at a high partial load operation (for example, 75 - 95% output) during high demand periods and low demand periods. As a result, while enhancing the followability of power supply to demand changes, the merits of self - power generation can be enjoyed.

[0112] (3) In the power supply system 1000 of (1), when the demand power D is set to D1 [W], which is the minimum demand power during a predetermined period, and a natural number obtained by truncating the decimal part of the value obtained by the calculation (D1 - Qs) / Qr is defined as n1, the number of installed power generation units 100, N, satisfies the following formula (2). 2 ≤ N ≤ n1 …(2)

[0113] (4) In the method for determining the number of installed power generation units 100 of (2), when the demand power D is set to D1 [W], which is the minimum demand power during a predetermined period, and a natural number obtained by truncating the decimal part of the value obtained by the calculation (D1 - Qs) / Qr is defined as n1, the number of installed power generation units 100, N, satisfies the following formula (2). 2 ≤ N ≤ n1 …(2)

[0114] When the total of the maximum supplyable power H obtained by multiplying the rated output power Qr of each power generation unit 100 by the number of installed units N and the reference purchase power Q1, (H + Qs), is used as the base load power, the number of installed units N is determined such that the base load power is less than the minimum demand power D1. Therefore, all the power generation units 100 operate at full load regardless of the high demand period and the low demand period, and the insufficient peak load power is supplemented by the purchase power. Each power generation unit 100 can be operated without the need to adjust the output power, so it has excellent followability to changes in the demand of the power demand facility 600.

[0115] (5) In the power supply system 1000 of (1), when the demand power D is set to D2 [W], which is the average demand power during a predetermined period, and a natural number obtained by truncating the decimal part of the value obtained by the calculation (D2 - Qs) / Qr is defined as n2, the number of installed power generation units 100, N, satisfies the following formula (3). 2 ≤ N ≤ n2 …(3)

[0116] (6) In the method for determining the number of power generation units 100 to be installed in (2), when the demand power D is set to D2 [W] which is the average demand power over a predetermined period, and the natural number obtained by truncating the decimal part of the value obtained by the calculation (D2 - Qs) / Qr is defined as M2, the number of power generation units 100 to be installed, N, satisfies the following formula (3). 2 ≤ N ≤ n2 …(3)

[0117] When the total of the maximum supplyable power H obtained by multiplying the rated output power Qr of each power generation unit 100 by the number of units N to be installed and the reference purchase power Qs is defined as the base load power, the number of units N to be installed is determined such that the base load power is less than the average demand power D2. Therefore, during the high demand period, all the power generation units 100 operate at full load, and the peak load power shortage is supplemented by the purchased power. On the other hand, during the low demand period, some or all of the power generation units 100 operate at partial load while maintaining the reference purchase power Qs. At least during the high demand period, each power generation unit 100 can be operated without the need for output power adjustment, so the power demand facility 600 has good followability to changes in power demand. Also, since the peak load power occurs only during the high demand period, the economy is also good.

[0118] (7) In the power supply system 1000 of (1), when the demand power D is set to D3 [W] which is the maximum demand power over a predetermined period, and the natural number obtained by truncating the decimal part of the value obtained by the calculation (D3 - Qs) / Qr is defined as n3, the number of power generation units 100 to be installed, N, satisfies the following formula (4). 2 ≤ N ≤ n3 …(4)

[0119] (8) In the method for determining the number of power generation units 100 to be installed in (2), when the demand power D is set to D3 [W] which is the maximum demand power over a predetermined period, and the natural number obtained by truncating the decimal part of the value obtained by the calculation (D3 - Qs) / Qr is defined as n3, the number of power generation units 100 to be installed, N, satisfies the following formula (4). 2 ≤ N ≤ n3 …(4)

[0120] When the base load power is set as the sum (H + Qs) of the maximum supplyable power H obtained by multiplying the rated output power Q0 of each power generation unit 100 by the number of installed units N and the reference purchase power B, the number of installed units N is determined such that the base load power is less than the maximum demand power D3. Therefore, all the power generation units 100 are operated at partial load regardless of the high demand period and the low demand period, and only the reference purchase power Q1 is supplied from the commercial power supply system 500. Since it is an operation that covers most of the demand of the power demand facility 600 with self-generated power, it is extremely excellent in terms of economy.

[0121] (9)(1,3,5,7) In the power supply system 1000, each of the plurality of power generation units 100 includes a power generation module 20, a power conditioner 16 that converts the generated power of the power generation module 20 into an output power corresponding to the AC power of the commercial power supply system 500, and a local controller 17 that controls the output power by controlling the generated power of the power generation module 20. In the plurality of power generation units 100, each of the power generation modules 20 includes a cell stack 1 in which solid oxide fuel cells are integrated.

[0122] The power supply system 1000 performs self-generation using the power generation unit 100 of the type using SOFC and supplies the self-generated power to the consumers. Since SOFC has a higher primary energy efficiency than thermal power generation, it is possible to reduce the carbon dioxide emissions by switching a part of the commercial power purchased by the consumers from the power company to the self-generated power.

[0123] Also, the plurality of power generation units 100 can shift from the interconnected operation mode to the independent operation mode when a power outage occurs in the commercial power supply system 500. By realizing a system that maintains power supply independently when a power outage occurs due to natural disasters or the like, the adverse effects on social life and economic activities can be reduced.

[0124] The embodiments of the present invention have been described above. However, the configuration of the present invention is not limited to the above embodiments, and various modifications can be made without departing from the gist of the invention. That is, the above embodiments should be considered as illustrative in all respects and not restrictive. The technical scope of the present invention is shown not by the description of the above embodiments but by the scope of the claims, and it should be understood that all modifications belonging to the meaning and scope equivalent to the scope of the claims are included.

[0125] 〔Contribution to the United Nations-led Sustainable Development Goals (SDGs)〕 The power generation unit and the power supply system according to the present disclosure reduce the carbon dioxide emissions by improving the primary energy efficiency, and can contribute to the achievement of Goal 13 "Take urgent action to combat climate change and its impacts" of the SDGs (Sustainable Development Goals). In addition, the power generation unit and the power supply system according to the present disclosure can maintain the power supply independently when a power outage occurs due to a natural disaster, and can contribute to the achievement of Goal 11 "Make cities and human settlements inclusive, safe, resilient and sustainable" of the SDGs.

Explanation of Reference Numerals

[0126] 1 Cell stack 2 Reformer 3 Burner 4 Evaporator 5 Air preheater 6 Anode off-gas cooler 7 Anode off-gas condenser 7a Fan 8 CO oxidizer (carbon monoxide oxidizer) 9 Condensate recovery tank 10 First raw fuel blower 11 First air blower 12 Water pump 13 Second raw fuel blower 14 Second air blower 15 Third air blower 16 Power conditioner 16a, 16b DC / DC converter 16c Smoothing capacitor 16d System connection inverter 16e, 16f Switches 16g, 16h Control circuits 17 Local controller 17a Communication unit 18 System controller 20 Power generation module 30 Auxiliary machine 40 Load module 41 Electric heater 42 Heat dissipation fan 100 Power generation unit 101 First power generation unit 102 Second power generation unit 103 Third power generation unit 104 Fourth power generation unit 200 Current sensor 201 First current sensor 202 Second current sensor 203 Third current sensor 204 Fourth current sensor 300 Self - contained socket 500 Commercial power system 600 Power demand equipment 610 Switchboard 1000 Power supply system Aa, Ab, Ac Air Ad Cooling air B1 First bellows type expansion joint B2 Second bellows type expansion joint B3 Third bellows type expansion joint B4 Fourth bellows type expansion joint E1, E2 Fuel inlets E3, E4, E5 Air inlets E6 Gas outlet Ga, Gf Raw fuel gas Gb Mixed gas Gc Reformed gas Gd Anode off - gas Ge Cathode off - gas Gg Combustion gas La Raw fuel line Lb Mixed Gas Line Lc Anode Fuel Line Ld Anode Off-Gas Line Le Cathode Air Line Lf Cathode Off-Gas Line Lg Combustion Gas Line Lh Burner Cooling Air Line Li Reformed Water Line Lj Startup Air Line Lk Cooling Air Line Lk1 Collection Pipe Lw Condensate Recovery Line Ma First Distribution Manifold Mb Second Distribution Manifold Mc First Collection Manifold Md Second Collection Manifold R1 First Region R2 Second Region Sa Gas-Liquid Separation Section Sb Water Level Detector Sc Drain Valve Wa Reformed Water Wb Condensate Za Heat Radiation Tube Zb Combustion Gas Pipe Zc Cooling Pipe

Claims

1. A power supply system that is operated in parallel with a commercial power supply system and includes a plurality of power generation units having the same rated output power. Let the rated output power of each of the plurality of power generation units be Qr [W], the reference purchase power preset to be always purchased from the commercial power supply system be Qs [W], and the demand power during a predetermined period in the power demand facility receiving power supply be D [W]. When the natural number obtained by truncating the decimal part of the value obtained by the calculation (D - Qs) / Qr is n, the number of installed power generation units N of the plurality of power generation units satisfies the following formula (1). Power supply system. 2 ≤ N ≤ n …(1)

2. When the demand power is set to D1 [W], which is the minimum demand power during a predetermined period, and the natural number obtained by truncating the decimal part of the value obtained by the calculation (D1 - Qs) / Qr is n1, the number of installed power generation units N of the plurality of power generation units satisfies the following formula (2). The power supply system according to claim 1. 2 ≤ N ≤ n1 …(2)

3. When the demand power is set to D2 [W], which is the average demand power during a predetermined period, and the natural number obtained by truncating the decimal part of the value obtained by the calculation (D2 - Qs) / Qr is n2, the number of installed power generation units N of the plurality of power generation units satisfies the following formula (3). The power supply system according to claim 1. 2 ≤ N ≤ n2 …(3)

4. When the demand power is set to D3 [W], which is the maximum demand power during a predetermined period, and the natural number obtained by truncating the decimal part of the value obtained by the calculation (D3 - Qs) / Qr is n3, the number of installed power generation units N of the plurality of power generation units satisfies the following formula (4). The power supply system according to claim 1. 2 ≤ N ≤ n3 …(4)

5. Each of the plurality of power generation units includes: A power generation module; A power conditioner that converts the generated power of the power generation module into output power corresponding to the AC power of the commercial power supply system; A local controller that controls the output power by controlling the generated power of the power generation module. In the plurality of power generation units, each of the power generation modules is configured to include a cell stack integrating solid oxide fuel cells. The power supply system according to any one of claims 1 to 4.

6. A method for determining the number of power generation units installed in a power supply system composed of a plurality of power generation units that are operated in parallel with a commercial power supply system and have the same rated output power, wherein the rated output power of each of the plurality of power generation units is Qr [W], the reference purchase power preset to be always purchased from the commercial power supply system is Qs [W], and the demand power during a predetermined period in the power demand facility receiving power supply is D [W]. When the natural number obtained by truncating the decimal part of the value obtained by the calculation (D - Qs) / Qr is n, the number of installed power generation units n of the plurality of power generation units satisfies the following formula (1): A method for determining the number of installed power generation units. 2 ≤ N ≤ n... (1)

7. When the demand power is set to D1 [W], which is the minimum demand power during a predetermined period, and the natural number obtained by truncating the decimal part of the value obtained by the calculation (Ds - Qr) / Q0 is n1, the number of installed power generation units N of the plurality of power generation units satisfies the following formula (2): The method for determining the number of installed power generation units according to claim 6. 2 ≤ N ≤ n1... (2)

8. When the demand power is set to D2 [W], which is the average demand power during a predetermined period, and the natural number obtained by truncating the decimal part of the value obtained by the calculation (D2 - Qs) / Qr is n2, the number of installed power generation units N of the plurality of power generation units satisfies the following formula (3): The method for determining the number of installed power generation units according to claim 6. 2 ≤ N ≤ n2... (3)

9. When the demand power is set to D3 [W], which is the maximum demand power during a predetermined period, and the natural number obtained by truncating the decimal part of the value obtained by the calculation (D3 - Qs) / Qr is n3, the number of installed power generation units N of the plurality of power generation units satisfies the following formula (4): The method for determining the number of installed power generation units according to claim 6. 2 ≤ N ≤ n3... (4)

Images