JPH0814104A - Cogeneration system - Google Patents

Abstract

PURPOSE:To improve thermal efficiency of a cogeneration system having a hot water heater for electrically heating hot water staying in a hot water storage cell by using excessive electric power and a hot water vessel. CONSTITUTION:A cogeneration system is provided with an efficiency storing means for storing the power generation efficiency of a prime mover 1/generator 3 system as a function for using a working rate, etc., of the prime mover as a parameter, storing the thermal efficiency of a prime mover 1/water heat exchanger 5 system as a function for using the working rate, etc., of the prime mover as a parameter and storing the thermal efficiency of a hot water vessel 7 as a function for using an air temperature, a water supply temperature, etc., as parameters. This is also provided with a prime mover control means for controlling the working rate of the prime mover according to an electric load or a heat load not a hot water vessel control means for controlling driving of the hot water vessel 7. This is further provided with a heat output shortage dealing determination instructing means for calculating, when heat output shortage is expected in the near future, a total thermal efficiency for dealing with a heat output shortage by increasing the working rate of the prime mover and that for dealing with this by actuating the hot water vessel and selecting either one of a higher total thermal efficiency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cogeneration system (power generation and hot water supply device) which uses a gas engine or the like using city gas as a fuel and which performs power generation and hot water supply (including other heat medium supply).

[0002]

2. Description of the Related Art Many cogeneration systems for generating electricity and supplying hot water by using a gas engine that uses city gas as a prime mover are put into practical use at present. In factories, hotels, hospitals, and offices that consume a large amount of heat energy (hot water, steam, etc.) together with electricity, a cogeneration system is installed to obtain electricity and hot water. At this time, about 30% of the fuel energy
Can be converted into electricity, and about 40% can be converted into heat energy of hot water or steam. Therefore, the total thermal efficiency is about 70%
And very expensive. The overall power generation efficiency of a general power generation / transmission system is about 35%.

As a basic idea in the operation control of this cogeneration system, there are an electric main heat slave operation and a thermal main power slave operation. In the former, the operation pattern of the cogeneration system is set according to the total electric load (demand) of the power consuming equipment in the building where the cogeneration system is installed, and the heat output generated by the operation should be used as effectively as possible. The idea is. The latter is the opposite way of thinking. In the case of general building cogeneration systems, there are many electric mains and subordinate operations. When the heat load (demand) of the building is larger than the heat output of the cogeneration system, a boiler separate from the cogeneration system is fired to satisfy the insufficient heat load.

[0004]

However, when the electric load of the cogeneration system has a margin because the electric load is low (the operating rate of the cogeneration system is low), the heat load is higher than the heat output at that time. May be large. In this case, a separate boiler is operated to compensate for the insufficient heat output. However, such a boiler has unexpectedly low thermal efficiency (65% to 70%).
In some cases, the overall thermal efficiency of the cogeneration system may be higher. However, in the case of the conventional cogeneration system, no consideration was given to equipment for converting surplus power into heat and storing it. Therefore, despite the low operation rate of the cogeneration system, a separate boiler had to be operated.

The present inventors aim to provide a cogeneration system capable of storing surplus electric power as heat energy, contributing to comprehensive energy saving, and having an improved ability to cope with load fluctuations. A cogeneration system is proposed, which includes a hot water heater that electrically heats hot water in a tank, and a surplus power supply unit that supplies surplus power from a generator to the hot water heater.

An object of the present invention is to further improve the above-mentioned proposed cogeneration system and to provide a cogeneration system having higher thermal efficiency.

[0007]

In order to solve the above problems, a cogeneration system uses a prime mover, a generator driven by the prime mover, and waste heat (including cooling removal heat) of the prime mover to generate hot water. A hot water heat exchanger to be manufactured, a hot water storage tank for storing hot water, a hot water heater for electrically heating the hot water in the hot water storage tank, an excess power supply means for supplying excess power from the generator to the hot water heater, and a hot water heat A water heater for supplying hot water to the hot water storage tank of a system different from the exchanger, a power replenishing means for supplying a shortage of electric power from a commercial power source, a power generation efficiency of the prime mover / generator system, and an operating rate of the prime mover as parameters. Stored as a function, the thermal efficiency of the prime mover / hot water heat exchanger system is stored as a function with the operating rate of the prime mover as a parameter, and the thermal efficiency of the hot water generator as a parameter such as the air temperature and the feed water temperature. Stored as a function, efficiency storage means, prime mover control means for controlling the operating rate of the prime mover according to the electric load or heat load, water heater control means for controlling the operation of the water heater, and the electric load is less than the rated output. Therefore, when the operation rate of the prime mover is less than 100% and the heat output is currently insufficient or is predicted to be insufficient in the near future, the operation rate of the prime mover is increased and the heat output of the hot water heat exchanger is increased. The overall thermal efficiency in the case of responding to the heat output shortage by raising the heat power and supplying surplus power to the hot water heater to supplement the heat output, and by operating the water heater to supplement the hot water to the hot water storage tank. A thermal output shortage response determination finger that calculates the overall thermal efficiency when responding to an output shortage, selects whichever has the higher overall thermal efficiency and issues an operation command to the prime mover control means and the water heater control means. Characterized by comprising a means.

[0008]

The cogeneration system of the present invention produces hot water by recovering the sensible heat of the exhaust gas generated by the prime mover and the cooling water of the prime mover by the hot water heat exchanger. The produced hot water is stored in the hot water storage tank. A hot water heater is provided in the hot water storage tank, and the hot water in the hot water storage tank can be electrically heated. The remaining surplus power obtained by subtracting the electric load from the electric output of the cogeneration system is sent from the generator to the hot water heater through the surplus power supply means, is used for heating the hot water, and is stored in the form of thermal energy of the hot water. Or used. Since the electricity-to-heat conversion efficiency of the hot water heater is almost 100%, it is possible to produce hot water with high thermal efficiency, which is comparable to the boiler when combined with the use of waste heat. In addition, by increasing the operating rate of the cogeneration system, it is possible to obtain the effect of improving the power generation efficiency of the generator. On the other hand, when the heat output is insufficient, a hot water heater may be used to cope with this, and hot water may be produced by burning city gas. With such a water heater, hot water can be supplied as a separate system to the hot water storage tank even when the electric power and heat output of the cogeneration system are at their maximum and the heat is still insufficient.

As described above, when the two means for dealing with the insufficient heat output are provided, which of them is to be selected becomes a next problem. For example, if the operating rate of the prime mover is considerably low and the power generation efficiency is low, the power generation efficiency is still low even if the operating rate of the prime mover is slightly increased, so it is simpler than raising the operating rate of the prime mover to cope with the heat output shortage. It is better to operate the water heater and refill hot water. On the other hand, when the operating rate of the prime mover is considerably high, it is economical to increase the operating rate of the prime mover to cope with the shortage of heat output because the overall thermal efficiency is high. The heat output insufficiency determination command means of the present invention determines which heat replenishing means is to be used according to the situation.

[0010]

Embodiments of the present invention will be described below. Figure 1
It is a systematic diagram of the cogeneration system which concerns on one Example of this invention. The cogeneration system of FIG. 1 is composed of a gas engine 1, a generator 3, a hot water heat exchanger 5, a water heater 17, a hot water tank 7, and other main equipment.

The gas engine 1 (motor) is a reciprocating type internal combustion engine, which operates by receiving city gas supply from the city gas line 2. The output shaft of the gas engine 1 is connected to the input shaft of the generator 3, the generator 3 is driven,
Power is generated. The generated power is sent to the power consuming device 63 through the electric path 62. When the load of the power consuming device 63 exceeds the capacity of the generator 3, commercial power is supplied from the commercial power line 65. Also, the generator 3
When the output of the above exceeds the load of the power consumption device 63, the surplus power can be sent to the hot water heater 11 of the hot water storage tank 7 through the electric line 13 (surplus power supply means).

A cooling water channel 21 is provided in the housing of the gas engine 1, and the gas engine 1 is water-cooled. The cooling water exiting the cooling water channel 21 is heated by the waste gas of the gas engine 1 in the waste gas heat exchanger 25. The waste gas of the gas engine 1 is sent from the waste gas discharge path 23 to the waste gas heat exchanger 25, and then discharged. The cooling water discharged from the waste gas heat exchanger 25 is sent to the hot water heat exchanger 5 through the high temperature cooling water passage 27.

In the hot water heat exchanger 5, the heat of the high temperature cooling water is used to heat the water coming from the water supply pipe 31 and the heating medium sent to each heat consuming device 47. That is, the water supplied from the water supply passes from the water supply pipe 31 through the flow control valve 15,
It is heated to about 80 ° C. by the hot water heat exchanger 5 and sent to the hot water storage tank 7 through the hot water pipe 35.

The heat medium is sent from the heat consuming device 47 (heating, absorption cooling, etc.) to the hot water heat exchanger 5 by the heat medium pump 43 and heated, and passes through the heat medium pipe 49 to reach each heat consuming device 47.
Sent to In some cases, the heat medium returned from the heat consuming device 47 is sent from the three-way switching valve 45 through the heat medium pipe 55 to the hot water storage tank 7 and is primarily heated in the hot water storage tank 7, and then the heat medium pipe 5
Secondary heating is carried out in the hot water heat exchanger 5 through 3.

The hot water storage tank 7 is provided with an electrically heated hot water heater 11.
Is provided. The hot water heater 11 is supplied with surplus electric power from the generator 3 and electrically heats the hot water in the hot water tank. That is, the surplus power is converted into thermal energy and stored in the hot water storage tank 7.

As equipment for supplying hot water to the hot water storage tank 7, a water heater 17 is provided in a system different from the hot water pipe 35 that enters the hot water storage tank 7 from the hot water heat exchanger 5. The water heater 17 heats the water supplied from the water supply pipe 31 into hot water by using city gas or the like as fuel, and sends it to the hot water storage tank 7. This water heater 17
Is the maximum output of the gas engine 1 but not enough hot water, or when the power load is too low to operate the gas engine 1 and the efficiency is poor To manufacture. The hot water in the hot water storage tank 7 is sent to the hot water consuming device 61 (bath or the like) by the pump 60 and consumed.

Next, a basic operation control method of the cogeneration system of the embodiment shown in FIG. 1 will be described.
FIG. 2 is a graph showing an example of the operation control state related to the main heat-subordinate operation of the cogeneration system. Graph (A) is a graph showing the relationship between time (horizontal axis) and electric load (vertical axis), and graph (B) shows the relationship between time (horizontal axis) and heat load (vertical axis). It is a graph.

First, in FIG. 2A, a thick curve having a mountain-like shape indicates an electric load. The dashed line drawn horizontally indicates the maximum electric output of the gas engine / generator system. The electric load rises from A to B and C with time, and reaches a peak at C. After that, it descends to D and E. A to B,
In the parts from D to E, the electric load is below the maximum output, and the gas engine is in partial load operation (operation rate is 100%).
Driving less than%). In the part of B-C-D, the electric load exceeds the maximum output. Therefore, the gas engine is performing the rated operation (operation with an operating rate of 100%), and at the same time, the commercial power supply is replenished.

Next, in FIG. 2 (B), a thick curve having a mountain-like shape indicates a heat load. The trapezoidal broken line is shown in FIG.
The heat output produced with the operation of the cogeneration system for producing the electrical output shown in (A) is shown. The heat load increases from a to b and c with time,
peak at c. After that, it descends to d and e. In the portions a to b and d to e, the heat load is below the heat output, and at that time, there is excess heat. b-c-d
The heat load exceeds the heat output in the area, and at that time, the heat is insufficient. Since heat can be stored unlike electricity, the heat surplus (2) between ab and de is stored in the hot water storage tank in the form of heat energy of hot water. And b
The heat shortage (3) such as between -d is compensated by the stored heat energy.

However, the heat shortage (3) may not be completely compensated by the heat surplus (2) between a and b. As a method of coping with such a situation, as described above, the operating rate of the gas engine is increased to increase the heat surplus between a and b, that is, the heat storage (the hatched portion in FIG. 2B) to deal with it. There are two methods: a method of doing so and a method of operating the water heater to replenish the heat when the heat shortage (3) occurs. In the present invention, the selection is made by judging which of the two is advantageous.

Next, the thermal main-power slave operation will be described. FIG. 2 is a graph showing an example of the operation control state related to the thermal main power subordinate operation of the cogeneration system. Graph (A) is a graph showing the relationship between time (horizontal axis) and heat load (vertical axis), and graph (B) shows the relationship between time (horizontal axis) and electric load (vertical axis). It is a graph.

In FIG. 3A, a thick curve having a mountain-like shape indicates a heat load. The dashed line drawn horizontally indicates the maximum heat output of the gas engine / hot water heat exchanger system. The heat load increases from A to B and C with time, and reaches a peak at C. After that, it descends to D and E. A to B and D
The heat load is less than the maximum output in the portions from E to E, and the gas engine is performing a partial load operation (operation with an operating rate of less than 100%). In the part of B-C-D, the heat load exceeds the maximum output. Therefore, the gas engine is performing a rated operation (operation with an operating rate of 100%), and at the same time, heat is supplemented from the hot water storage tank. In addition, the water heater is operated as needed.

Next, in FIG. 3B, a thick curve having a mountain-like shape indicates an electric load. The trapezoidal broken line is shown in FIG.
The electric output produced with the operation of the cogeneration system for producing the heat output shown in (A) is shown. The electric load rises from a to b and c with time, and reaches a peak at c. After that, it descends to d and e. a
In the portions from b to d and from d to e, the electric load is below the electric output, and at that time, there is surplus electricity.
In the part b-c-d, the electric load exceeds the electric output, and at that time, there is a shortage of electricity at that time, and the electric power is replenished from the commercial power source. Electricity, unlike heat, cannot be stored (it can be done with batteries, but is not common).
The electric surplus (2) between −b and d−e is sent to the hot water heater of the hot water storage tank 7 to be converted into the heat energy of the hot water, and is stored in the hot water storage tank in the form of heat energy. Then, the heat shortage between B and D shown in FIG. 3A is compensated by the stored heat energy.

However, in some cases, the heat shortage cannot be completely compensated by the stored heat obtained by converting the electric surplus (2) between a and b. As a method to deal with such a situation, as described above,
Increase the operating rate of the gas engine, and the electric surplus between a and b,
That is, there are two methods, namely, a method of increasing the stored heat (hatched portion in FIG. 3A) to cope with it, and a method of operating the water heater to supplement electricity when the heat shortage occurs. In the present invention, the selection is made by judging which of the two is advantageous.

Next, the control system of the cogeneration system of this embodiment will be described. FIG. 4 is a block diagram showing the configuration of the control system of the cogeneration system of this embodiment. The prime mover / generator system power generation efficiency storage unit 102 in the efficiency storage means 101 stores the power generation efficiency of the prime mover / generator system as a function with the operating rate of the prime mover as a parameter. Further, the prime mover / hot water heat exchanger system thermal efficiency storage unit 103 in the efficiency storage means 101 stores the heat efficiency of the prime mover / hot water heat exchanger system as a function with the operating rate of the prime mover as a parameter. Efficiency storage means 10
The water heater thermal efficiency storage unit 104 in 1 stores the thermal efficiency of the water heater as a function with the temperature and the water supply temperature as parameters.

The heat output shortage prediction unit 106 in the heat output shortage determination means 105 checks whether the heat output is currently insufficient when the operating rate of the prime mover is less than 100% because the electric load is less than the rated output. And predict if there will be a shortage in the near future. Further, in the above case, the total thermal efficiency calculation unit 107 in the heat output shortage determination means 105 increases the operating rate of the prime mover, raises the heat output of the hot water heat exchanger, and inputs surplus power to the hot water heater. The overall thermal efficiency in the case of responding to the insufficient heat output by replenishing the heat output, and the overall thermal efficiency in the case of responding to the insufficient heat output by operating the water heater to replenish hot water to the hot water tank Is calculated. Then, the selection unit 108 in the heat output deficiency determination unit 105 selects whichever of the two cases has the higher total thermal efficiency. The operation command unit 109 in the heat output deficiency determination unit 105, based on the above selection, is the motor control unit 110 and the water heater control unit 111.
Issue a driving command to.

When the operating rate of the prime mover is considerably low and the power generation efficiency is low, the power generation efficiency is still low even if the operating rate of the prime mover is slightly increased. Therefore, rather than increasing the operating rate of the prime mover to cope with the heat output shortage, , It is better to simply operate the water heater to supplement hot water. On the other hand, when the operating rate of the prime mover is considerably high, it is economical to increase the operating rate of the prime mover to cope with the shortage of heat output because the overall thermal efficiency is high. The heat output insufficiency determination command means of the present invention determines which heat replenishing means is to be used according to the situation.

[0028]

As is apparent from the above description, the cogeneration system of the present invention increases the operating rate of the prime mover to cope with insufficient heat output, or operates the water heater to cope with insufficient heat output. In determining the above, the one with higher overall thermal efficiency is selected, so that the thermal efficiency of the cogeneration system including the hot water heater and the water heater that electrically heats the hot water in the hot water storage tank by using the surplus power can be further increased.

[Brief description of drawings]

FIG. 1 is a system diagram of a cogeneration system according to an embodiment of the present invention.

FIG. 2 is a graph showing an example of an operation control state related to main power / electrical slave operation of a cogeneration system. Graph (A) is a graph showing the relationship between time (horizontal axis) and electric load (vertical axis), and graph (B) shows the relationship between time (horizontal axis) and electric load (vertical axis). It is a graph.

FIG. 3 is a graph showing an example of an operation control state related to an electric main power subordinate operation of the cogeneration system. Graph (A) is a graph showing the relationship between time (horizontal axis) and electric load (vertical axis), and graph (B) shows the relationship between time (horizontal axis) and electric load (vertical axis). It is a graph.

FIG. 4 is a block diagram showing a configuration of a control system of the cogeneration system of this embodiment.

[Explanation of symbols]

1 gas engine 2 city gas line 3 generator 7 hot water tank 11 hot water heater 13 electric circuit 15 flow control valve 17 water heater 21 cooling water flow path 25 waste gas heat exchanger 45 three-way valve 47 heat consuming device 61 hot water consuming device

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display area F02G 5/00 A

Claims (1)

[Claims] 1. A prime mover, a generator driven by this prime mover, a hot water heat exchanger that produces hot water by using exhaust heat (including cooling removal heat) of the prime mover, and a hot water storage tank that stores hot water. A hot water heater for electrically heating the hot water in the hot water storage tank, a surplus power supply means for supplying excess power from the generator to the hot water heater, and hot water for supplying hot water to the hot water storage tank in a system different from the hot water heat exchanger. And a power replenishing means for supplying insufficient power from a commercial power source, and the power generation efficiency of the prime mover / generator system is stored as a function with the operating rate of the prime mover as a parameter, and the thermal efficiency of the prime mover / hot water heat exchanger system is stored. Is stored as a function with the operating rate of the prime mover as a parameter, and the thermal efficiency of the water heater is stored as a function with parameters such as air temperature and water supply temperature. And motor control means for controlling the operation rate of the motives, and water heater control means for controlling the operation of the water heater, for the electrical load is less than the rated output engine operating ratio 100
%, And the heat output is currently insufficient or predicted to be insufficient in the near future, increase the operating rate of the prime mover, increase the heat output of the hot water heat exchanger, and supply surplus power to the hot water heater. Total thermal efficiency in the case of responding to the insufficient heat output by charging and replenishing the heat output,
And operating the water heater to replenish the hot water tank with hot water to calculate the total thermal efficiency in the case of dealing with the insufficient heat output, and select the one with the higher total thermal efficiency to select the motor control means and the hot water. A cogeneration system, comprising: a heat output shortage determination determination command means for issuing an operation command to the reactor control means;