JP2628218B2 - Optimal control method for cogeneration system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to energy consumption in buildings and facilities having a private power generator and a heat recovery device when two types of secondary energy, electricity and heat, are used simultaneously. The present invention relates to an optimal control method for a cogeneration system aiming at minimizing the cost of the system.

[Background of the Invention]

In addition to commercial power, private power generation to meet the power demand and heat demand in buildings or facilities has become popular.
When electricity and heat are used simultaneously in such buildings or facilities (hereinafter referred to as buildings, etc.), the utilization efficiency of primary energy (the sum of the energy required for in-house power generation and the commercial power supplied from outside the system) is the highest. It is desirable that the power demand and the heat demand are balanced so as to be higher. However,
In practice, it is rather rare to be balanced in time and in quantity. The cogeneration system (CGS) aims to increase the utilization efficiency of primary energy when such secondary energy of electricity and heat is used at the same time. Even if a good equipment configuration is adopted, the true value of CGS cannot be demonstrated unless the operation mode is appropriate.

However, when energy saving control is performed so that the primary energy is minimized, the energy cost is not always minimized. Fig. 1 shows the operation method of CGS installed in a general office building where the heat-to-electric ratio (heat demand / power demand ratio at the same time) averages about 0.3. Here, the cost saving rate is a rate at which the energy cost is reduced, and is represented by the equation (1). Power-based operation is a method of generating electricity following power demand and radiating excess heat, and heat-driven operation is a method of generating power in accordance with heat demand. Means that power is generated mainly by heat up to a point where power demand is not exceeded. As can be seen in Fig. 1, the energy saving control that minimizes the primary energy uses a gas / power rate ratio of about 0.35.
This is the same as the cost saving rate in the case of, and in that case, the optimal operation is heat-based operation. But the gas / electricity ratio is about 0.29
In the following, the optimal operation is power-based operation, in which case the operation with the minimum primary energy is disadvantageous in terms of cost. The current gas / electricity charge ratio is between about 0.1 and 0.4, so in consideration of economy, there is a limit to the control method for energy saving control that minimizes primary energy (gas / electricity The present invention is intended to simultaneously control power and heat at the minimum energy consumption cost by properly controlling the operating conditions of the equipment constituting the CGS. Things.

[Configuration of the invention]

The present invention predicts power demand and heat demand of a building or facility equipped with a private generator having a capacity control function and a heat recovery device having a heat recovery amount control function from measured values of outside air conditions. Judging the start / stop timing of the generator and the heat recovery device according to the predicted value, measuring the instantaneous power demand and heat demand of the building or facility in real time, and determining the instantaneous heat-to-electricity ratio (heat demand / power demand). Ratio), and from the thermoelectric ratio and the information on the charge ratio between the fuel rate of the private generator and the commercial power rate, the main power operation for generating power following the power demand or the amount of generated power does not exceed the power demand Up to this point, it is determined which of the heat main operation that generates electric power according to the heat demand is the most cost-effective, and the operation main body is determined according to this judgment.
While securing the amount of power purchased to prevent the generated electricity from flowing back to the commercial side, the cost-saving rate (SC) shown in equation (1) is maximized, and the power generation dependency ratio (power generation / power Load), control the capacity of the generator and the capacity of the heat recovery unit. SC = (C ₁ -C ₂ ) / C ₁ × 100 (1) where C ₁ is CGS ( Cogeneration system)
Cost of energy consumption during supplying heat and electricity demand irrespective of the cogeneration · C ₂ is characterized by, representing the cost of the energy consumed during supplying the same heat and electricity demand by CGS This is the optimal control method for the system.

〔Example〕

FIG. 2 shows an example of a device arrangement of a CGS system to which the present invention is applied. The building (certain university) General power load W heat load for _L and Air Q _L1 and the hot water supply heat load Q _L2 is present. Building power load W _L are covered by the power produced by the commercial electric power W _S and private power generator 1. On the other hand, the heat loads _QL1 and _QL2 are provided by using a heat recovery device 3 and a heat-radiating heat exchanger 4 that recover exhaust heat of an engine 2 that is a driving source of the generator 1. That is, the exhaust gas of the engine 2 is introduced into the exhaust gas heat exchanger 5, where high-temperature water is produced, and the high-temperature water is led to the cold / hot water generator, which is the heat recovery device 3, through the primary heat source circuit P. in the cooling season in the cold and hot water generator to make the cold water of the cooling load Q _L1, directly make the hot water in the heating season. These cold or hot water are supplied to the air conditioning equipment group 6.
Is circulated and supplied to the secondary side by way of a forward path 7 and a return path 8 and is used as a heat source for air conditioning. The high-temperature water is also guided to a heat-radiating heat exchanger, which is a second heat recovery device 4, and the liquid medium received here is circulated and supplied to the hot-water storage tank 9 via the secondary-side forward path 10 and return path 11, and Used as a heat source.

A cooling heat exchanger 13 is interposed in the cooling water circulation path 12 of the engine 2, and the heat radiated by the cooling heat exchanger 13 is also supplied to the circulating water before entering the exhaust gas heat exchanger 5. It is. Further, a heat-radiating heat exchanger 14 for appropriately radiating the heat that could not be radiated by the first heat recovery device 3 and the second heat recovery device 4 is provided in the primary heat source circuit P. In the illustrated example, a gas engine is used as the engine, but an engine using a liquid fuel is also applicable.

In the CGS system configured as described above, a device configuration that can freely control the capacity of the private generator and the amount of heat recovery of the heat recovery device is adopted. This can be done, for example, by controlling the capacity of the generator by controlling the number of engines and / or the number of revolutions, and controlling the amount of heat recovery of the heat recovery unit by controlling the number of heat recovery units and / or the primary side. Alternatively, it can be performed by controlling the flow rate of the secondary heat source circuit. This control operation is performed by a control signal X from the computer 15.
And Y by control panels 16 and 17 made by Y.

On the other hand, the measured values of the outside air condition and the measured values of the power demand and the heat demand are input to the computer 15 in real time, and both the power demand and the heat demand are predicted and learned from the outside air condition according to a program created in advance. Here, the reason for estimating the power demand and the heat demand is to determine whether the generator is to be operated or stopped in advance from the tendency of the demand. On the other hand, control signals X and Y are output in accordance with the power demand and the heat demand measured in real time so that SC in the above equation (1) becomes maximum. As the measured value of the outside air condition,
Outside air temperature T (detection signal a), humidity H (same as above), pressure P
(Same as above), solar radiation R (same as above) is adopted, and the measured value of power demand is the detected value of the commercial power meter 18 (e) and the detected value of the power supplied by the private power generator 19 (f). Is done. As the measured value of the heat demand, the sum of the cooling and heating load and the hot water supply load is measured in real time, and the cooling and heating load is interposed in the secondary outward path 7 and the return path 8 to the air conditioning equipment group 6. Calculated from the difference between the calorific value detection values (g) and (h),
Regarding hot water supply load, outbound route 10 and return route to secondary storage tank 9
It is determined from the difference between the detected calorific values (R) and (N) interposed in 11.

In this way, the detected values (a) to (nu) are input to the computer 15 every moment, and the operating conditions of the engine 2 and the heat recovery device 3 are controlled so that (SC) in the above equation (1) is maximized. Thereof the said (1) of the formula, the cost C ₁ of the energy consumption during supplying heat and electricity demand regardless the CGS, the power load is used the power consumption at the time of supplying only the commercial power The heat load is calculated by using an analysis program in which the cost of fuel when supplying heat using a refrigerator and a boiler using the same fuel as CGS is calculated in advance, and Cost of energy consumption when supplying the heat and power demand of the country C ₂
It is sufficient to use a CGS analysis program that analyzes in advance the number and operating capacity of generators and heat recovery units that are suitable for the heat load and power load for each hour, and integrates the power consumption and fuel consumption of CGS. The generator operation method that can be calculated may be any of constant rate, quantitative basis, and quantitative peak operation.

As an example, Fig. 3 to Fig. 3 show the state when the CGS installed in a general office building whose average heat-to-electric ratio (ratio of heat demand / power demand at the same time) is about 0.3 is controlled by the optimal control system of the present invention. This will be described with reference to FIG.

FIG. 3 shows the heat load at each time, the heat release amount (heat amount that could not be used) obtained by subtracting the heat load from the heat amount recovered by the CGS, and the thermoelectric ratio. When the optimal control system is not introduced, it can be seen that the amount of heat radiation increases and the energy use efficiency decreases.

FIG. 4 shows the power generation when the CGS is controlled by the optimal control system according to the present invention when the thermoelectric ratio is about 0.3 on average.
It shows the relationship between the amount of power purchased and the power load. CGS
The system is operated at a power generation dependency ratio that minimizes the cost of energy consumption while securing the amount of power purchased (to prevent reverse power flow) so that the electricity generated in step (1) does not flow back to the commercial side. If the optimal control system is not introduced, only the amount of power purchased to prevent reverse power flow is purchased as a commercial product, and the remaining
S will generate electricity.

Fig. 5 compares the energy saving cost reduction rate of operating the CGS with the optimal control system and the energy saving cost rate of operating the CGS without the optimal control system. . At start-up, there is no significant difference in the cost saving ratio between the two, but after 7:00 am, the difference between the two becomes a maximum of about 9%, and at night when the thermoelectric ratio decreases, CG
You can see that the power load is covered by the power purchase by preventing waste when generating electricity with S.

As described above, according to the present invention, the system is operated with the lowest energy consumption cost in the CGS system, and true cost saving is achieved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a change in a cost saving rate accompanying a change in a gas / electricity charge ratio, FIG. 2 is a device arrangement system diagram showing an example of a CGS system to which the present invention is applied, and FIG. Fig. 4 shows the changes in heat load, heat release, and thermoelectric ratio at each time of the building. Fig. 4 shows the relationship between power generation, purchased power, and power load when the CGS was controlled by the optimal control system for the building. Figure 5
The figure compares the cost saving rate of energy consumption cost by operating the CGS with the optimal control system and the energy saving cost rate of operating the CGS without the optimal control system. 1 ... private power generator, 2 ... engine, 3 ... heat recovery device (cold / hot water generator), 4 ... heat release heat exchanger, 5 ... exhaust gas heat exchanger, 6 ... air conditioner group, 9… Hot water storage tank, 13… Cooling heat exchanger, 14… Heat dissipation heat exchanger, 15… Computer.

Claims (1)

(57) [Claims] In a building or facility equipped with a private power generator having a capacity control function and a heat recovery device having a heat recovery amount control function, power demand and heat demand of the building or facility are predicted from measured values of outside air conditions. Determining the start / stop timing of the generator and the heat recovery device according to the predicted value; measuring the instantaneous power demand and heat demand of the building or facility in real time; Ratio)
From the thermoelectric ratio and the information on the charge ratio between the fuel rate of the private generator and the commercial power rate, determine whether power-driven operation follows power demand or power generation does not exceed power demand. Judgment is made as to which of the heat main operation, which generates electric power in response to heat demand, is the most cost-effective, and the operation main body is determined according to this judgment. In the electric power main operation, the generated electricity does not flow back to the commercial side. Under the power generation dependency ratio (power generation / power load), the cost saving rate (SC) shown in equation (1) is maximized and the cost of energy consumption is minimized while securing the amount of power purchased.
To control the capacity of the generator and the capacity of the heat recovery unit, SC = (C ₁ -C ₂ ) / C ₁ × 100 (1) where C ₁ is based on CGS (cogeneration system). cost of energy consumption during supplying heat and electricity demand without, C ₂ is the cogeneration system according to claim, representing the cost of the energy consumed during supplying the same heat and electricity demand by CGS Optimal control method.