JP4669654B2 - Small fuel cell system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a standard small fuel cell system for home use and business use.
[0002]
[Prior art]
Currently, as a fuel cell used in a small-sized fuel cell system for home use or business use, a model having a small power generation capacity of about 200 W to 30 kW has been developed, and is going to be put on the market one after another (see Patent Document 1). ).
[0003]
For example, in a small fuel cell system for home use, as shown in FIG. 15, one solid polymer fuel cell 501 of about 700 W to 1.5 kW is installed. Then, the fuel cell 501 generates electricity using city gas or the like as fuel, and supplies the generated electric power to an electric device 502 such as a home TV, refrigerator, air conditioner, or lighting. The output of the fuel cell 501 is instructed by the control unit 505 based on the demand amount of the power / heat load detected by the sensors 5021 and 5041. However, when the power is insufficient, the supply of commercial power is received and surplus In this case, it can be sold as commercial power. Since heat is also generated when power is generated by the fuel cell 501, the generated heat is stored as hot water in the hot water storage tank 503, and the hot water is supplied to a heat demanding device 54 such as a bath, kitchen, floor heating or the like. In the case of a commercial fuel cell system, the electrical equipment and heat demand equipment used are changed to commercial equipment, but the usage form is basically the same as that for home use.
[0004]
[Patent Document 1]
JP 2003-51316 A
[0005]
[Problems to be solved by the invention]
By the way, the amount of demand for electric power and heat load of small consumers varies depending on the type of business and scale. For example, in the case of small hospitals, the demand for power and heat load varies greatly depending on the number of beds held by each hospital. In the case of a beauty salon, the demand for power and heat load varies greatly depending on the number of customers. In addition, the demand for power and heat load varies depending on the season and time of day, and in order to economically operate a small fuel cell of several kW to several tens of kW, it is necessary to follow the load well and operate the surplus. It is necessary to minimize the generation of electric power and heat.
[0006]
In the case of households, the demand for power and heat load varies greatly depending on the number of family members, and the number of families changes as the family ages. Furthermore, in this case as well, the power and heat load changes depending on the season and time zone. To economically operate a small fuel cell of several hundred watts to several kW, it is necessary to follow the load well and operate. It is necessary to minimize the generation of electric power and heat. FIG. 16 shows, for example, fluctuations in demand for electric power load and hot water supply (heat) load by season (spring, summer, autumn and winter) and by time zone (0-24 o'clock) in a standard family with a family of four in the Kansai region. A pattern (load pattern) is shown.
[0007]
It is necessary to introduce a small fuel cell with an optimal capacity for such demands of various electric power and heat loads. However, there is a case where an apparatus with an optimal capacity cannot be installed with one small fuel cell. In addition, when the demand amount of the electric power / heat load changes with time, the optimum fuel cell capacity may change and replacement by purchase is necessary. On the other hand, as a fuel cell manufacturer, in order to prepare an optimal fuel cell for various power and heat load demands, a fuel cell with various types of power generation capacity will be developed and lineup will be required. Considering inventory, the economic burden increases. In addition, cost increases are unavoidable in order production from customers.
[0008]
The present invention has been made in view of the above circumstances. The purpose of the present invention is to install a plurality of small fuel cells for the purpose of supplying electric power and heat to small consumers. It is to provide a small fuel cell system to be operated.
[0009]
[Means for Solving the Problems]
Small fuel cell system according to one aspect of the present invention Is a small fuel cell system for small-sized customers that operates by following an electric load and a thermal load, each of which is capable of generating power and having a plurality of small fuel cells having a heat exchanging unit, and each of the heat exchanging units. A hot water storage tank to which water is supplied through a pipe passing through, a load prediction means for predicting a load pattern for at least one of the power load and the thermal load, and each small size based on the load pattern predicted by the load prediction means Operation control means for individually controlling the operation of the fuel cell; The operation control means controls the operation of at least one small fuel cell in a load region in which the operation control with the lowest load at midnight is possible. It is characterized by that.
[0010]
According to this configuration, for small consumers, a plurality of small fuel cells are installed for the capacity that is optimal for the electric power load and heat load, and each small fuel cell is installed according to the load pattern. By individually controlling, a plurality of small fuel cells can be optimally controlled as a whole system.
[0011]
In general, since there is little midnight power load for home and business use, it is preferable to operate with a minimum power load if the small fuel cell is operated at midnight. Therefore, the above As in the invention, if the operation control means controls the operation of at least one small fuel cell in a load region in which operation control at the lowest load at midnight is possible, a small size unnecessary at midnight. By stopping the fuel cell and lowering the minimum load of the entire system, it is possible to meet the low power demand at midnight.
[0012]
Small fuel cell system according to another aspect of the present invention Is a small fuel cell system for small-sized customers that operates by following an electric load and a thermal load, each of which is capable of generating power and having a plurality of small fuel cells having a heat exchanging unit, and each of the heat exchanging units. A hot water storage tank to which water is supplied through a pipe passing through, a load prediction means for predicting a load pattern for at least one of the power load and the thermal load, and each small size based on the load pattern predicted by the load prediction means Operation control means for individually controlling the operation of the fuel cell; And the plurality of small fuel cells include small fuel cells having different start times, and the operation control means includes a small fuel cell having a first start time and a second shorter than the first start time. In combination with a small fuel cell having a start-up time, the operation of each small fuel cell is controlled so as to reduce the start-up loss of the entire system. It is characterized by that.
[0013]
the above As described in the invention, small fuel cells having different start times are installed, and the operation control means has a small fuel cell having the first start time and a second start time shorter than the first start time. If each small fuel cell is to be operated and controlled so as to reduce the startup loss of the entire system in combination with the small fuel cell, the small fuel cell to be stopped against the predicted load pattern It can be selected and operated so as to reduce the loss at the start-up of the entire system. For example, the start-up time of the fuel cell reformer by the normal steam reforming method (corresponding to the first start-up time) requires about 30 minutes to 1 hour, but the reformer by the partial oxidation combustion method is sufficient. Since the start-up time is about the same (corresponding to the second start-up time), for the base load, an ordinary reformer solid polymer fuel cell or a solid oxide fuel cell that does not start and stop are operated. For the daytime peak, a polymer electrolyte fuel cell with a fast start-up time having a reformer by the partial oxidation combustion method may be operated.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a block diagram showing a configuration of a small fuel cell system according to an embodiment of the present invention, where (a) is an overall configuration diagram and (b) is a configuration diagram of a control unit. As shown in FIG. 1A, this system includes three polymer electrolyte small fuel cells (PEFCs) 1a, 1b, and 1c, for example, a television set at home, a refrigerator, an air conditioner, Electrical equipment 2 such as lighting, high-temperature / medium-temperature / low-temperature storage tanks 3a, 3b, 3c, heat demand equipment 4 for kitchens, toilets, baths, etc., and a control unit 5 as operation control means Have . The control unit 5 is electrically connected to a memory 6, a timer 7, a power demand detection sensor 21 as a detection means, and a heat demand detection sensor 41. The memory 6 is for storing a predetermined load pattern and the like. As the sensor 21, for example, a voltmeter or ammeter installed in a power supply line, an air conditioner switch, or the like can be used. As the sensor 41, for example, a thermometer or level meter installed in a storage tank can be used. .
[0015]
The control unit 5 further includes a load pattern reading unit 51 as a load prediction unit, an operation load setting unit 52, an activation / stop unit 53 as an operation control unit, an efficiency determination unit 54, as shown in FIG. The driving load determination unit 55 Have . Each of the units 51 to 55 is embodied by various programs that are read into the CPU constituting the control unit 5 from a ROM (not shown) when the system is started.
[0016]
Among them, the load pattern reading unit 51 is for reading a load pattern stored in the memory 6. The operation load setting unit 52 sets the power load and the heat load in the read load pattern as the operation loads at a predetermined time using the timer 7, and determines the number of small fuel cells to be operated corresponding to the load. In addition, for large electric devices such as air conditioners, the operation load when the switch is turned on is set and the above operation load is set, and the number of small fuel cells operated is set. Determination and setting of load sharing can be performed. The start / stop unit 53 starts each of the three small fuel cells 1a, 1b, and 1c according to the number of operating units and the load sharing determined by the operating load setting unit 52 to increase the output (increase the operating load), or The output is lowered (reduced operating load) and stopped. The efficiency determining unit 54 calculates and determines how to distribute these loads based on the characteristic data of the small fuel cells 1a, 1b, and 1c to be operated, and determines based on this determination. A command is issued to the start / stop unit 53.
[0017]
For example, in a small fuel cell of a medium efficiency machine, this characteristic data shows that at 100% output, the power generation efficiency is 33.5%, the exhaust heat efficiency is 30.0%, the total efficiency is 64.0%, and the output is 75%. The power generation efficiency is 32.9%, the exhaust heat efficiency is 15.3%, the total efficiency is 48.2%, and the power generation efficiency is 31.8% and the exhaust heat efficiency is 3.1% at 50% output. The total efficiency is 34.9%, and when the output is 25%, the power generation efficiency is 29.7%, the exhaust heat efficiency is 0.0%, and the total efficiency is 29.7%. Thus, it is known that the exhaust heat efficiency becomes very low at 50% output or less. The power generation efficiency is the ratio of the electric output (output) of the small fuel cell to the amount of heat generated by the fuel, and the exhaust heat efficiency is the ratio of the heat output (exhaust heat amount) of the small fuel cell to the amount of heat generated by the fuel. Means the sum of power generation efficiency and exhaust heat efficiency. The operation load determination unit 55 determines whether there is a difference between the operation load set based on the load pattern or the like and the electric power demand and the heat demand detected by the sensors 21 and 41, if any. It is determined whether or not there is a surplus, and the determination result is fed back. In response to this determination, the operating load setting unit 52 resets the operating load.
[0018]
FIG. 2 shows the system configuration of the polymer electrolyte fuel cell. In the figure, each small fuel cell 1a, 1b, 1c generates, for example, a small power of about 1 kW, and the generated power (3 kW) of one small fuel cell 501 in the conventional example is three of them. Can be covered.
[0019]
Since each small fuel cell 1a, 1b, 1c has the same configuration, only one (1a) of them will be described below. A desulfurizer 11, a reformer 12, a CO converter 13, a battery body 14, an air blower 15, and a selective oxidizer 16 are respectively provided. Have . The desulfurizer 11 removes sulfur as an odorant contained in city gas (propane gas, naphtha, kerosene, etc.) as fuel, and gas is supplied so that the city gas is supplied. Connected to the supply pipe. The reformer 12 is connected to the gas outlet side of the desulfurizer 11, and the desulfurized city gas and water vapor are heated by the burner 121 to react with each other, thereby reforming mainly carbon dioxide and hydrogen. It produces gas. The CO converter 13 is connected to the gas outlet side of the reformer 12, and changes carbon monoxide contained in the reformed gas into carbon dioxide in order to prevent poisoning of the cell electrode and reduction in power generation efficiency. Is. The selective oxidizer 16 reduces the CO concentration contained in the gas sent from the CO converter 13 to 10 ppm or less in order to prevent poisoning of the cell electrode. The battery body 14 includes a negative electrode to which hydrogen supplied from the CO transformer 13 is supplied and a positive electrode to which oxygen in the air sent from the air blower 15 is supplied, and causes an electromotive reaction at each electrode. It generates electricity.
[0020]
Hereinafter, the operation of the small fuel cell 1a will be described. The city gas is desulfurized by the desulfurizer 11 and then mixed with steam to enter the reformer 12. This mixture is heated to about 800 ° C. by heating the burner 121 in the reformer 12 and then converted into a reformed gas mainly composed of hydrogen by the action of the catalyst. This reformed gas enters the battery main body 16 via the CO converter 13 and the selective oxidizer 14 and generates a power by chemically reacting with oxygen in the air sent from the air blower 15.
[0021]
The generated electric power is converted from direct current to alternating current by an unillustrated inverter and supplied to the electric device 2. The battery body 16 generates heat due to a chemical reaction between hydrogen and oxygen. In order to keep the small fuel cell 1a at a constant temperature, it is cooled with water to remove excess heat. Hot water (hot water) of about 60 to 80 ° C. can be obtained by heating the tap water using this excess heat (exhaust heat). This heat is stored in the hot water tank 3 and supplied to the heat demanding device 4 as needed. The small fuel cell 1a has a function of supplying electric power and heat. The same applies to the other small fuel cells 1b and 1c.
[0022]
Next, the operation of the system including these small fuel cells 1a, 1b, and 1c will be described with reference to FIG. FIG. 3 is an explanatory diagram showing an example of the operation of this system, where (a) is a flowchart, (b) is a load pattern, and (c) is an operable range for each number of operating units. In FIG. 3A, the load pattern reading unit 51 of the control unit 5 reads a load pattern stored in advance in the memory 6 (step S1). As shown in FIG. 16, for example, the load pattern is based on a standard household power load and heat load (demand load) collected by season, time zone, and the like. Here, it is assumed that a load of 2.5 kW at a certain time is read as shown in FIG.
[0023]
The operating load setting unit 52 determines the number of units to be operated based on the load at the time (current load) and the expected future load and issues a command to the start / stop unit 53 at this time. When a switch of a large electric device such as the above is turned on, the operation signal is also taken in and the number of operating units is determined (step S2). Here, the operation load setting unit 52 first issues a command for starting one small fuel cell, but the load suddenly increases from 1 kW to 2.5 kW during the operation of the one unit, and the load continues thereafter. Since the time zone increases, the total number of operating units is selected as three as shown in FIG.
[0024]
Upon receiving the above command, the start / stop unit 53 starts the first small fuel cell (for example, 1a) according to the preset operation sequence, and then starts the second (1b), third (1c) ). Moreover, also when stopping, according to the driving | operation order set beforehand, it stops in order of 1c->1b-> 1a (step S3). Assuming that the first unit is already in operation, the operation load setting unit 52 issues an operation continuation command for the first unit, and issues a start command for the second and third units.
[0025]
Next, in order to optimize load distribution, the efficiency determination unit 54 calculates and determines how the load sharing of each small fuel cell to be operated will maximize the efficiency of those small fuel cells, A command based on the determination is issued to the start / stop unit 53 (step S4).
[0026]
Here, since the load is 2.5 kW, load sharing can be either Case A (1 kW × 2 units, 0.5 kW × 1 unit) or Case B (1 kW × 1 unit, 0,75 kW × 2 units). However, if the load sharing of case A is selected, the small fuel cell 1a in operation increases its output to 1 kW, the small fuel cell 1b is activated, and 1 kW after the activation. The small fuel cell 1c is started up and the output is raised to 0.5 kW after the start-up, thereby increasing the operation load of the entire system (step S5).
[0027]
Next, the driving load determination unit 55 detects the difference between the driving load and the demand load, and determines whether to apply feedback based on this difference (step S6). Then, if the difference between the operation load and the demand load becomes larger than the load control width of the small fuel cell or a certain set amount, the process returns immediately before step S2. Here, it is determined whether the load difference is larger or smaller than ½ of the load control width of the small fuel cell. If it is smaller than 1/2, the current state is maintained, and if it is larger than 1/2, the operation load setting unit 52 returns to the difference between the fed back operation load and demand load. To determine the number of units to be operated.
[0028]
For example, while operating the small fuel cells 1a, 1b, and 1c at 2.5 kW as a whole system, even if the power load demand drops to 2.4 kW, the minimum load range in which load control is possible is 250 W. Even if feedback based on the difference between the load and the demand load is applied, the load of each small fuel cell 1a, 1b, 1c does not change. On the other hand, if the driving load is reduced to 2.3 kW, the driving load setting unit 52 determines whether to drive at 2.5 kW or 2.25 kW. Reduce the fuel cell output. At this time, Case A (1 kW × 2 units, 0.5 kW × 1 unit), Case B (1 kW × 1 unit, 0.75 kW × 2 units), Case C (1 kW × 1 unit, 0.75 kW × 1 unit), One of 0.5 kW × 1 unit) can be selected. In this case, since the power generation efficiency and the exhaust heat efficiency are the highest in the case B load distribution, the case B load distribution is selected. By sending a load command to each small fuel cell 1a, 1b, 1c, the small fuel cell 1a is maintained at 1 kW, 1b is dropped from 1 kW to 0.75 kW, and 1c is loaded with 0.5 kW. A command is issued to the start / stop unit 53 so as to be maintained. Then, the above steps S2 to S6 are repeated until the system is stopped.
[0029]
Here, the examination result about the validity of this system is explained. Specifically, the power generation efficiency, exhaust heat efficiency, or total efficiency of the system was compared between the case of one 3 kW small fuel cell and the case of three 1 kW small fuel cells. When a plurality of small fuel cells are installed, a small fuel cell whose output is unnecessary is stopped at a low load, and a so-called serial operation is performed in which the next small fuel cell is started and operated when the load becomes high. The so-called parallel operation in which three 1 kW small fuel cells are activated and operated simultaneously is the same as the case where one 3 kW small fuel cell is activated and operated.
[0030]
FIG. 4 shows a comparison of power generation efficiency. In the case of one 3 kW small fuel cell indicated by reference numeral A1 in FIG. 4, the power generation efficiency increases from 30% to 33.5% as the output increases from 750 W to 3000 W. On the other hand, in the case of three 1 kW small fuel cells indicated by the same symbol B1, the power generation efficiency increases rapidly from 30% to 33.5% as the output increases from 250 W to 1000 W by starting the first unit. is doing. Next, while the output increases from 1000W to 2000W due to the start-up of the second unit, the power generation efficiency is the average value of two units, so it temporarily decreases to 32%, but then recovers immediately and increases to 33.5%. is doing. And while the output increases from 2000W to 3000W due to the start of the third unit, the power generation efficiency decreases to 32.5% because it is the average value of the three units, but then recovers immediately and increases to 33.5% is doing. Thus, compared to the case of one 3 kW small fuel cell, in the case of three 1 kW small fuel cells, the power generation efficiency is improved by 1 to 3% at an output of 2 kW or less, and operation at a partial load is possible. The economy is considerably improved for many small consumers. In addition, the minimum load is 750 W in the case of one 3 kW small fuel cell, whereas it decreases to 250 W in the case of three 1 kW small fuel cells, which is a great advantage for midnight fuel cell operation. I knew that to give.
[0031]
FIG. 5 shows a comparison of the amount of exhaust heat. In the case of one 3 kW small fuel cell indicated by reference character A2 in FIG. 5, the exhaust heat amount is 0 W at an output of 1250 W or less, and the exhaust heat amount increases from 0 W to 2750 W as the output increases from 1250 W to 3000 W. ing. On the other hand, in the case of three 1 kW small fuel cells indicated by the same symbol B2, the amount of heat exhausted is 0 W at an output of 500 W or less by the start of the first unit, and the exhaust amount increases as the output increases from 500 W to 1000 W. The amount of heat has risen from 0W to 900W. Next, when the second unit is started at 1 kW during the output increase from 1000 W to 2000 W due to the start of the second unit, the amount of exhaust heat once decreases to 300 W because one unit is 250 W and the other unit is 750 W. However, it recovered immediately and rose to 1800W. And when the third unit is started at 2kW during the output increase from 2000W to 3000W due to the start of the third unit, the amount of exhaust heat once decreases to 1300W because one unit is 250W and one unit is 750W. After that, it recovered immediately and increased to 2800W. As shown in FIG. 5, in the case of three 1 kW small fuel cells, the amount of exhaust heat increases more at an output of 2.5 kW or less, and doubles at 2 kW or less, compared to the case of one 3 kW small fuel cell. It turns out that it becomes. For customers with long operation hours under partial load and high heat demand, it is expected that the increase in exhaust heat in this way, especially the ability to store heat even at night when the load is low, will greatly improve the economy. The Further, the minimum load for obtaining exhaust heat is 1250 W in the case of one 3 kW small fuel cell, whereas it is reduced to 500 W in the case of three 1 kW fuel cells. Even when a small fuel cell is operated, heat can be stored, and can be stored in night heating or hot water storage tanks. FIG. 6 shows the degree of improvement in exhaust heat efficiency. Similarly, in the case of one 3 kW small fuel cell indicated by reference symbol A2 ′ in FIG. 6, three small 1 kW fuel cells indicated by reference symbol B2 ′ are provided. Compared to the case, the improvement of the exhaust heat efficiency at the partial load becomes remarkable.
[0032]
FIG. 7 shows the degree of improvement in overall efficiency. From FIG. 7, in the case of three 1 kW small fuel cells indicated by symbol B3, the overall efficiency exceeds 50% in the range from 750 W to 3 kW, compared to the case of one 3 kW small fuel cell indicated by symbol A3. However, overall efficiency is greatly improved.
[0033]
In FIG. 8, one small fuel cell of 3 kW with a maximum power generation efficiency of 31, 33, 37% is installed, and one small fuel cell of 1 kW with a maximum power generation efficiency of 31, 33, 37% is installed. A comparison with the case of 3 kW in total is shown. In the figure, A11 is a 3 kW small fuel cell having a maximum power generation efficiency of 31%, A12 is a small fuel cell having a maximum power generation efficiency of 33%, and A13 is a small fuel having a maximum power generation efficiency of 37%. This is the case for batteries. The same sign B11 is a case where a 1 kW small fuel cell is started in the order of 31%, 33%, and 37%. The symbol B12 is a case where a 1 kW small fuel cell is started in the order of 37%, 33%, and 31%. In the operation of reference B11, there is almost no difference from the case of one 3 kW small fuel cell having a maximum power generation efficiency of 33% (reference A12), but in the reference B13, the power generation efficiency at a partial load is greatly improved.
[0034]
FIG. 9 shows a comparison of the amount of exhaust heat. In the figure, symbol A14 is a 3 kW small fuel cell having a power generation efficiency of 31%, symbol A15 is a small fuel cell having a power generation efficiency of 33%, and symbol A16 is a small fuel cell having a power generation efficiency of 37%. It is. Symbol B14 in the figure is a case where a 1 kW small fuel cell is started in the order of 31%, 33%, and 37%. The symbol B15 is a case where a 1 kW small fuel cell is started in the order of 37%, 33%, and 31%. Regarding the amount of exhaust heat, both symbols B14 and B15 improve with partial load, but the increase when operating with symbol 15 is slightly larger. FIG. 10 shows a comparison of exhaust heat efficiency, which shows the same tendency. In addition, each code | symbol in a figure respond | corresponds by attaching | subjecting a dash (') to the code | symbol in FIG.
[0035]
FIG. 11 shows the overall efficiency. In the figure, symbol A17 is a 3 kW small fuel cell having a maximum power generation efficiency of 31%, symbol A18 is a small fuel cell having a maximum power generation efficiency of 33%, and symbol A19 is This is the case of a small fuel cell with a maximum power generation efficiency of 37%. The symbol B17 is a case where a 1 kW small fuel cell is started in the order of 31%, 33%, and 37%. The symbol B18 is a case where a 1 kW small fuel cell is started in the order of 37%, 33%, and 31%. From FIG. 11, the overall efficiency is greatly improved in the entire load region except that the rated load is equivalent to that of one small fuel cell of 3 kW. Further, the minimum load is also reduced, and the load change range is widened, so that the operability is improved.
[0036]
In a system having three small fuel cells of 1 kW as described above, a small fuel cell that does not require output is stopped at low load, and the next small fuel cell is operated in series when the load increases. However, the power generation efficiency, exhaust heat efficiency, and overall efficiency are higher than when a single 3 kW small fuel cell is installed and operated. However, it is preferable to avoid frequent start / stop with a short stop time because the start-up loss increases. Further, the exhaust heat amount can be increased in a wide load range by operating in series operation so as to maximize the exhaust heat amount by controlling the load of each small fuel cell. However, when emphasizing the higher power generation efficiency as indicated by reference signs B12, B14, B14 ′, and B17, compared to the case of attaching importance to the higher heat exhaust efficiency as indicated by reference signs B11, B15, B15 ′, and B18. The amount of exhaust heat is somewhat reduced.
[0037]
These operations do not need to be fixed throughout the year. For example, it is operated in a case where power generation efficiency is high (reference numerals B12, B14, B14 ′, B17) in summer when there is a large amount of power demand and heat demand is low, and a large amount of exhaust heat can be obtained in the winter season when heat demand is high (reference numerals B11, B15, B15 ′, and B18) are better operated, and the control unit 5 has a function of performing such operation determination and switching of operating devices.
[0038]
As described above, in the small fuel cell system of the present embodiment, a plurality of (three) small fuel cells 1a, 1b, and 1c are installed, and the power generation efficiency, exhaust heat efficiency, or overall efficiency is increased. As a result, high efficiency can be achieved in the entire load region, and economic efficiency is improved. However, there is a concern that the installation of multiple small fuel cells may be expensive in terms of equipment costs, but in the case of small fuel cells, the economies of economies of scale are less than conventional equipment, and costs are reduced due to shared parts such as waste heat equipment This is expected to be canceled.
[0039]
Further, even if one of the plurality of small fuel cells breaks down, the remaining small fuel cells can be operated, and there is little possibility that all the small fuel cells stop simultaneously. For this reason, periodic inspection, renewal of the old model, and handling at the time of failure are facilitated, and the reliability of the system is improved.
[0040]
In addition, small consumers can select and combine the specifications of small fuel cells for their own power / heat load according to their purpose, which increases the degree of freedom of choice for power / heat load demand, and the optimal system. Can be built.
[0041]
On the other hand, a manufacturer only needs to prepare several types of standard small fuel cells (standard units) for a number of small consumers, and the cost reduction effect due to standardization can be obtained. The mass production of standardized units leads to cost reduction at the manufacturer, resulting in lower costs.
[0042]
Various modifications can be considered for this embodiment. This will be described below.
[0043]
(Modification 1)
In the embodiment described above, three 1 kW small fuel cells are provided for one conventional 3 kW small fuel cell. However, the present invention is not limited to this, for example, required power / heat load. The power generation capacity and the number of installed small fuel cells may be selected in accordance with the above, and the method of combining the operation order of the small fuel cells once installed may be selected. Even in that case, in the same manner as described above, for example, the highest efficiency can be obtained in the load region from the lowest load to the rated load with respect to at least one of the electric power load demand and the thermal load demand by the small consumer. Operation control is possible.
[0044]
For example, for a standard household power / heat load as shown in FIG. 16, the most economical is when a small fuel cell of 500 W to 1 kW is installed. In such a home, when one small fuel cell of 1 kW is installed, by installing two 500 W fuel cells, an effect equivalent to that for business use can be obtained. In particular, it is said that the electric power load at home is small and the minimum load of the fuel cell system is 25 to 30% of the rated load regardless of the rated load capacity. When a small fuel cell of 1 kW is installed, 250 W Is the minimum load. On the other hand, when two 500 W small fuel cells are installed, if one of them is stopped and the remaining one is operated, the minimum load is 125 W, which is lower than the midnight load of 200 W to 300 W at home. Become. In this way, only necessary power is generated even at midnight, and economical operation becomes possible.
[0045]
In addition, with regard to the use of exhaust heat, in a 1 kW small fuel cell, exhaust heat is almost lost at 50% load (500W) or less, but when two 500W small fuel cells are installed, up to 25% load (250W). The heat can be used, and heat is generated even at midnight operation, and hot water can be stored in the hot water tank. Also, when two 500 W small fuel cells are installed in terms of power generation efficiency, at 500 W or less, by stopping one of them, the load of the remaining one 500 W small fuel cell is increased and the power generation efficiency is increased. Can be maintained at a high level. Thus, high efficiency can be achieved by controlling the number of operating devices.
[0046]
(Modification 2)
In the first modification, the economical efficiency can be further improved by introducing two 500 W small fuel cells having different specifications.
[0047]
For example, it is conceivable to combine a small fuel cell with high power generation efficiency but low exhaust heat and a small fuel cell with low power generation efficiency but high exhaust heat. In general, it is economical to operate a small fuel cell with high power generation efficiency at a location corresponding to the base load, so the small fuel cell with high power generation efficiency is operated continuously, and exhaust heat is exhausted during the time when the operation time is limited. It is economical to operate a large number of small fuel cells so as not to generate surplus power and heat. Examples of small fuel cells with high power generation efficiency include high-efficiency polymer electrolyte fuel cells and solid electrolyte fuel cells.
[0048]
(Modification 3)
In addition, one unit is highly efficient, but small fuel cells equipped with facilities that require about 30 minutes to 1 hour to start and stop (corresponding to the first start time) and the other unit are slightly inefficient, It is also conceivable to combine with a small fuel cell equipped with a facility with good maneuverability with a start-up time of about 10 minutes (corresponding to the second start-up time).
[0049]
By combining such small fuel cells with different start-up times, the base load is shared by small fuel cells with long start-up times, and small fuel cells with short start-up times are used to handle places with high loads. Efficiency can be improved. A solid electrolyte fuel cell as a small fuel cell with high power generation efficiency but limited start-stop; a solid polymer fuel cell with a normal steam reformer as a small fuel cell with high power generation efficiency but long start-stop; There is a polymer electrolyte fuel cell equipped with a partial oxidation reformer as a small fuel cell having a slightly low power generation efficiency but quick start-up. In addition to a small fuel cell, a combination with a gas engine or the like is also possible.
[0050]
As a method of operating such a plurality of small fuel cell systems, predict which fuel cell should be operated at what time based on the time-dependent data of seasonal power or heat load. In consideration of the startup time, it is preferable to start operation preparation before the load increases. The said embodiment uses the load pattern by such prediction. However. You may use the load pattern by only one of a season and a time slot | zone, or only one of an electric power load and a heat load, and the load pattern by another parameter.
[0051]
(Modification 4)
By the way, in the exhaust heat utilization method when a plurality of small fuel cells are installed, in the basic system, as shown in FIG. 12, one hot water tank 3a, 3b is provided for each small fuel cell 1a, 1b, 1c. , 3c are provided, but it is conceivable to consolidate these hot water tanks 3a, 3b, 3c as shown in FIG. FIGS. 12 and 13 show an exhaust heat utilization system when a plurality of polymer electrolyte fuel cells are installed.
[0052]
FIG. 12 corresponds to the above-described embodiment, and the hot water storage tanks 3a, 3b, 3c are installed for the respective solid polymer type small fuel cells 1a, 1b, 1c, and each small fuel cell 1a, Water from the water supply pipe 11 is supplied to 1b and 1c. The water supplied from the water supply pipe 11 is heat-exchanged at the heat exchange section (not shown) of each small fuel cell 1a, 1b, 1c to become hot water, and is discharged from each small fuel cell 1a, 1b, 1c. . On the other hand, each small fuel cell 1a, 1b, 1c and hot water storage tank 3a, 3b, 3c are connected by a communication pipe 40, and the connection pipe 40 is controlled to be opened and closed by a command from a control unit (not shown). Control valves 31 to 39 are disposed at appropriate positions. And by controlling the opening and closing of the control valves 31 to 39, when the load is low, it is possible to concentrate heat in one hot water storage tank and store heat. For example, when concentrating on the high-temperature hot water tank 3a, the control valves 31, 33, 37, and 34 are opened and the remaining control valves 32, 38, 39, 35, and 36 are closed according to a command from the control unit. To do. As the control valves 31 to 39, for example, electromagnetic valves or air operated valves can be used.
[0053]
The hot water storage tanks 3a, 3b, 3c can change the hot water storage capacity and the hot water temperature depending on the heat supply destination. For example, the high temperature hot water tank 3a can be set to 90 ° C., the intermediate temperature hot water tank 3b can be set to 80 ° C., and the low temperature hot water tank 3c can be set to 60 ° C. As in the high temperature hot water tank 3a, the small fuel cells 1a, 1b, 1c can be discharged. When hot water higher than the heat temperature (80 ° C.) is required, the hot water storage tank 3a is provided with an electric heater and a gas burner (not shown), and the electric heater is heated with surplus power or heated with a gas burner. As a result, the convenience of each hot water storage tank 3a, 3b, 3c becomes high. Further, when a solid oxide fuel cell is adopted as the small fuel cell 1a, the exhaust heat temperature is as high as 90 ° C., so that hot water is mainly stored in the high temperature hot water storage tank 3a, and the intermediate temperature hot water storage tank 3b is appropriately passed through the control valves 31 and 38. It is also possible to add the hot water to a temperature of 80 ° C. In this case, a heating gas heater or an electric heater is unnecessary.
[0054]
FIG. 13 shows a system in which a large hot water storage tank 3 is installed to collect hot water from the small fuel cells 1a, 1b, 1c in the hot water storage tank 3 to collect exhaust heat. This reduces the cost of hot water tanks, simplifies control valves and piping, and offers advantages in terms of cost and installation space. However, two hot water storage tanks may be installed as an intermediate plan between FIG. 13 and FIG.
[0055]
(Modification 5)
By the way, when installing a plurality of small fuel cells of about 0.8 to 1.5 kW for home use, the capacity of one small fuel cell is usually 3 to 4 for 200 to 300 W machines, If it is 500W machine, it becomes 2-3. However, a single unit of 200-300W machine is too small to make the partial load operation of 25%, 50%, 75% and 100%, and the load control unit becomes complicated, resulting in an increase in cost. It might be.
[0564]
Therefore, in the case of such a small capacity machine, each small fuel cell is stopped or only rated load operation is performed, and the load can be changed stepwise as a system. In this case, for example, as shown in FIG. 14, the control unit operates the first small fuel cell for the base load, and the second unit, the third unit, the fourth unit, etc. according to the load pattern. In addition, the operation of each small fuel cell is controlled at a constant output by changing the start / stop timing. The hatched parts in the figure are covered with commercial power. As a system that performs only such load changes, the cost of a small fuel cell alone can be reduced, and operation control can be simplified. Therefore, the system is suitable for home use or small-scale business use.
[0057]
【The invention's effect】
According to the present invention, for small consumers, a plurality of small fuel cells are installed for the capacity that is optimal for the electric power load and the heat load, and each small fuel cell is set according to the load pattern. By individually controlling, a plurality of small fuel cells can be optimally controlled as a whole system. Further, even if one of the plurality of small fuel cells breaks down, the remaining small fuel cells can be operated, and there is little possibility that all the small fuel cells stop simultaneously. For this reason, periodic inspection, renewal of the old model, and handling at the time of failure are facilitated, and the reliability of the system is improved. In addition, small consumers can select and combine the specifications of small fuel cells for their own power / heat load according to their purpose, which increases the degree of freedom of choice for power / heat load demand, and the optimal system. Can be built. On the other hand, a manufacturer only needs to prepare several types of standard small fuel cells (standard units) for a number of small consumers, and the cost reduction effect due to standardization can be obtained. The mass production of standardized units leads to cost reduction at the manufacturer, resulting in lower costs.
[0058]
Also Especially, when the load becomes low for a certain period of time, some small fuel cells are stopped, and the small fuel cells that are operating are operated with a high load with high power generation efficiency and exhaust heat efficiency. Since it is possible to control the operation of a plurality of small fuel cells so that the fuel cell as a whole system has high power generation efficiency and exhaust heat efficiency, a plurality of fuel cells can be controlled for at least one of the power load demand and the heat load demand by small consumers. It is possible to control the operation of a system composed of a small fuel cell so that, for example, the highest efficiency can be obtained in the load region from the lowest load to the rated load.
[0059]
Also By selecting the optimal power generation capacity, specifications, number of installed small fuel cells, and by combining the operation order of the small fuel cells once installed, at least the power load demand and heat load demand by small consumers On the other hand, a system composed of a plurality of small fuel cells can be controlled to obtain the highest efficiency in the load region from the lowest load to the rated load.
[0060]
Also By stopping unnecessary small fuel cells at midnight and lowering the minimum load of the entire system, it is possible to meet the low power demand at midnight.
[0061]
Also A small fuel cell to be stopped with respect to the predicted load pattern can be selected and operated so as to reduce the loss at the start-up of the entire system.
[0062]
Also The total capacity of a plurality of small fuel cells can be changed stepwise. By adopting a configuration that performs only such a step-like change in capacity, the cost of a small fuel cell alone is reduced and the operation control is simplified, so it is particularly suitable for home use and small-scale business use.
[0063]
Also A plurality of small fuel cells can be selected and operated so as to be most economical. Then, according to the thermal power / electric load data of small customers, select the most suitable operation unit (small fuel cell to be operated) according to the season, month, and time, so that multiple small fuel cells can be most economical. Can be operated, and even if an unexpectedly large load (for example, operation of an air conditioner) is applied, it can be detected and dealt with.
[0064]
Also In addition, the capacity and holding temperature of each hot water tank are selected for each heat supply destination, and the waste heat obtained from the small fuel cell must meet the detailed heat demand by installing the connecting pipe and control valve for supplying hot water. Can do. As a hot water storage tank, it isolate | separates into the object for high temperature water, the object for low temperature water etc., and shall use it properly by a use. In the case of using a polymer electrolyte fuel cell, surplus power or a gas heater may be used to raise the temperature of the hot water storage tank, but in the case of a solid electrolyte fuel cell, the exhaust heat can be used as it is. Or , Saving The hot water tanks can be consolidated to simplify the system configuration, and the operation control can be simplified.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a small fuel cell system according to an embodiment of the present invention, where (a) is an overall configuration diagram and (b) is a configuration diagram of a control unit.
FIG. 2 is a diagram showing a system configuration of a polymer electrolyte fuel cell.
FIGS. 3A and 3B are explanatory diagrams showing an operation example of the system, wherein FIG. 3A is a flowchart, FIG. 3B is a load pattern, and FIG. 3C is an operable range for each number of operating units;
FIG. 4 is a view for examining power generation efficiency.
FIG. 5 is a view for examining the amount of exhaust heat.
FIG. 6 is a view for examining exhaust heat efficiency.
FIG. 7 is a view for examining overall efficiency.
FIG. 8 is a view for examining power generation efficiency.
FIG. 9 is a view for examining the amount of exhaust heat.
FIG. 10 is a view for examining exhaust heat efficiency.
FIG. 11 is a diagram for examining overall efficiency.
FIG. 12 is a system configuration diagram when there is a hot water tank for each small fuel cell.
FIG. 13 is a system configuration diagram when there is a shared hot water bath.
FIG. 14 is an explanatory diagram showing step-like operation control.
FIG. 15 is a block diagram showing an overall configuration of a fuel cell system according to a conventional example.
FIG. 16 is an example diagram showing a power / heat load pattern of a standard household.
[Explanation of symbols]
1a, 1b, 1c Small fuel cell
2 Electrical equipment
3, 3a, 3b, 3c Reservoir
4 Thermal load equipment
5 Control unit (corresponds to operation control means)
51 Load pattern reading section
52 Operating load setting section
53 Start / stop unit
54 Efficiency Judgment Department
55 Operating load judgment section
6 memory
7 Timer

Claims (2)

In a small fuel cell system for small-sized customers that operate by following an electric load and a thermal load,
A plurality of small fuel cells each capable of generating electricity and having a heat exchange section;
A hot water tank to which water is supplied through a pipe passing through each of the heat exchange parts;
Load prediction means for predicting a load pattern for at least one of the power load and the thermal load;
Operation control means for individually controlling the operation of each small fuel cell based on the load pattern predicted by the load prediction means ,
The operation control means controls operation of at least one small fuel cell in a load region in which operation control with a minimum load at midnight is possible . In a small fuel cell system for small-sized customers that operate by following an electric load and a thermal load,
A plurality of small fuel cells each capable of generating electricity and having a heat exchange section;
A hot water tank to which water is supplied through a pipe passing through each of the heat exchange parts;
Load prediction means for predicting a load pattern for at least one of the power load and the thermal load;
Operation control means for individually controlling the operation of each small fuel cell based on the load pattern predicted by the load prediction means ,
The plurality of small fuel cells include small fuel cells having different start times,
The operation control means combines a small fuel cell having a first startup time with a small fuel cell having a second startup time shorter than the first startup time so as to reduce the startup loss of the entire system. A small fuel cell system characterized in that the operation of each small fuel cell is controlled .

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