JPH03285520A - Optimum control method for cogeneration system - Google Patents

Abstract

PURPOSE:To improve efficiency by predicting power demand and heat demand, in a facility provided with a non-utility generator and a heat recovery unit, and measuring both demands in real time thereby controlling the operating conditions of both units. CONSTITUTION:Power to load L is fed from commercial power WS and power from a generator 1. Exhaust gas from the engine 2 of the generator 1 is subjected to heat exchange 5 with water thus feeding high temperature water to a pipe P, then the heat is recovered 3 and cooling/warming load QL1 is operated through a group of air-conditioners 6, and then heat is radiated 4 to operate a hot water supply load QL2, and the heat is further radiated 14 to cool 13 the engine cooling water 12. A computer 15 predicts power demand and heat demand based on environment conditions such as temperature and atmospheric pressure, determines voltage, current, temperature, flow rate and the like at each section and controls the engine input X and heat recovery Y so that the SC shown by a formula is maximized. SC is an energy save rate, C1 is the cost when no congeneration system CGS is employed, and C2 is the cost when heat and power is fed through CGS.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention aims to reduce energy consumption when two types of secondary energy, electricity and heat, are used simultaneously in buildings and facilities equipped with private generators and heat recovery devices. This paper relates to an optimal control method for cogeneration systems aimed at minimizing costs.

[Background of the invention]

In addition to commercial electricity, it has become common to meet the electricity and heat needs within a building or facility by generating private power.

When electricity and heat are used simultaneously in a building (such as a building), power demand and heat demand are It is desirable for the two to be balanced, but in reality, it is rather rare that they are balanced both in terms of time and quantity. Cozy Energy Residency System (CGS) aims to improve the efficiency of primary energy use when secondary energy such as electricity and heat is used simultaneously, but for this purpose it requires the most investment. Even if an efficient equipment configuration is adopted, the true value of CGS cannot be demonstrated unless its operation mode is appropriate.

However, when energy-saving control is performed to minimize primary energy, the energy cost is not necessarily minimized. .About CGS introduced in about 3 general office buildings.

This is a study on how to operate it. Here, the cost saving rate is the rate at which the energy cost decreases, and it corresponds to (1).
It is shown by the formula. Furthermore, power-based operation refers to an operation method in which power is generated in accordance with electricity demand, and excess heat is radiated. Heat-based operation is a method in which power is generated in accordance with heat demand. This means that electricity is generated mainly from heat until the amount of electricity does not exceed the electricity demand. As seen in Figure 1, the energy saving control that minimizes primary energy is the same as the cost saving rate when the gas/electricity rate ratio is approximately 0.35, and at that time, the optimal operation is based on heat. It becomes driving. However, when the gas/IIT power rate ratio is about 0.29 or less, the optimum operation is electricity-based operation, and in that case, the operation that minimizes the primary energy is disadvantageous in terms of cost.

What is the current gas/electricity rate ratio?

Since it is between about 0.1 and 0.4, when considering economic efficiency, there is a limit to the energy saving control method that minimizes the primary energy (gas/electricity rate ratio is about 0).
．． Limited to cases of 29 or more. ) The object of the present invention is to appropriately control the operating conditions of the equipment constituting the CGS and to simultaneously supply electricity and heat with the minimum energy consumption cost.

[Structure of the invention]

The present invention predicts and learns the electricity demand and heat demand of a building, etc. that has a private power generator and heat recovery device, and at the same time measures the momentary electricity demand and heat demand in real time, which is expressed by equation (1). In order to maximize the cost saving rate (SC),
It is characterized by controlling the operating conditions of the heat generating via and the heat recovery device.

5C=(CI-C1)/CIX100・
...(1) However, CI is the cost of energy consumed when the heat and power demand is supplied without using CGS (cogeneration system) + CI is the cost of energy consumption when the same heat and power demand is supplied by CGS represents the cost of energy consumption.

〔Example〕

FIG. 2 shows an example of the equipment arrangement of a CGS system to which the present invention is applied. A building (a certain university) has a general power load WL, a heat load for air conditioning and heating QL+, and a heat load for hot water supply QL.

exists. The building's power load WL is commercial power W.

This will be covered by the electricity produced by the private generator 1. On the other hand, the heat loads Q L I and Qtx are covered by using the heat recovery device 3 that recovers the exhaust heat of the engine 2 that is the driving source of the 9 power generation 811 and the heat exchanger 4 for heat radiation. That is, the exhaust gas from the engine 2 is transferred to the exhaust gas heat exchanger 5.
The high-temperature water is produced here, and this high-temperature water is guided to the cold/hot water generator, which is the heat recovery device 3, via the primary heat source circuit P, and this cold/hot water generator handles the cooling load Q L during the cooling season. + produces cold water, and directly produces hot water during the heating season. This cold water or hot water is circulated and supplied to the air conditioning equipment group 6 through an outgoing path 7 and a return path 8 on the secondary side, and is used as a heat source for air conditioning. The high-temperature water is also guided to the heat exchanger for heat radiation, which is the second heat recovery device 4, and the liquid medium that has received heat is transferred to the hot water storage tank 9 through the outgoing path 10 and the return path 11 on the secondary side.
It is used as a heat source for hot water supply.

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, the primary heat source circuit P is provided with a radiation heat exchanger 14 for appropriately radiating heat that cannot be completely radiated by the first heat recovery device 3 and the second heat recovery device 4.

In the CGS system configured as described above, the device configuration is such that the capacity of the private generator and the amount of heat recovered by the heat recovery device can be freely controlled. this is.

For example, the capacity of a generator can be controlled by controlling the number of engines and/or the number of revolutions, and the amount of heat recovered by a heat recovery device can be controlled by controlling the number of heat recovery devices and/or by controlling the number of engines on the primary or secondary side. This can be done by controlling the flow rate of the side heat source circuit.

This control operation is performed by control panels 16 and 17 operated by control signals X and Y from computer 15.

On the other hand, the computer 15 receives measured values of outside air conditions and measured values of power demand and heat demand in real time, and predicts and learns both power demand and heat demand from outside air conditions according to a program created in advance. Here, the reason for predicting the power demand and the heat demand is to judge in advance whether to operate or stop the generator based on the trend of demand.

On the other hand, the control signal
, Y is output. Measured values of outside air conditions include outside air temperature T (detection signal A) and humidity H (same port).

Atmospheric pressure P (same as C), 1 solar radiation R (same as 2) are adopted, and the measured values of electricity demand are the detected value of the commercial wattmeter 18 (e) and the detected value of the wattmeter 19 of the power supplied by the private generator (f). will be adopted. As for the measured value of heat demand, the total of the cooling/heating load and the hot water supply load is measured in real time. It is determined from the difference between the detected heat value ()) (f), and the hot water supply load is determined from the detected heat value (1) C
It is determined from the difference between M>.

In this way, the detected values (a) - (nu) are inputted into the combinator 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. . At that time, among the above formula (1),
Regarding the cost CI of energy consumption when heat and power demand is supplied without using CCS, the power consumption when supplying only commercial electricity is used for the power load, and the heat load uses the same fuel as CGS. Using an analysis program that calculates in advance the cost of fuel when supplying heat using the refrigerator and boiler used, CGS
The cost of energy consumed when supplying the same heat and power demand by C! It is sufficient to use a CGS analysis program that analyzes in advance the number and operating capacity of generators and heat recovery equipment that match the hourly heat load and power load, and calculates the power consumption and fuel consumption of CGS. , the method of operating a generator that can be calculated is constant rate.

Either stationary base or quantitative peak operation may be used.

- As an example, the state when a CGS installed in a general office building where the thermoelectric ratio (ratio of heat demand/1!power demand at the same time) is about 0.3 on average is controlled by the optimal control system of the present invention. will be explained according to FIGS. 3 to 5.

Figure 3 shows the heat load at each time, the amount of heat released by subtracting the heat load from the amount of heat recovered by CCS (the amount of heat that could not be used), and the thermoelectric ratio. It can be seen that if an optimal control system is not introduced, the amount of heat dissipated increases and the efficiency of primary energy use decreases.

FIG. 4 shows the relationship between the amount of generated electricity, the amount of purchased electricity, and the IIt power load 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. While securing the amount of power purchased to prevent electricity generated by CCS from flowing back to the commercial side (to prevent reverse 1111),
It is operated at a power generation dependency ratio that minimizes the cost of consumed energy. If an optimal control system is not introduced, only the amount of electricity required to prevent reverse power flow will be purchased commercially, and the rest will be generated entirely by CGS.

Figure 5 shows the cost saving rate of energy consumption costs due to the operation of CGS with the optimal control system installed.

This is a comparison of the cost savings rate in energy consumption costs when CGs are operated without introducing an optimal control system. There is not much difference in cost saving rate between the two at startup, but at 7 am
The difference between the two models is about 9% at most, which shows that at night when the thermoelectric ratio is low, CGS prevents wasted power generation and covers the power load with purchased electricity.

As described above, according to the present invention, the system is operated in a state where the cost of energy consumption is the lowest in the CCS system, and true cost saving is achieved.

[Brief explanation of drawings]

Figure 1 is a diagram showing changes in the cost saving rate due to changes in the gas/electricity rate ratio, Figure 2 is an equipment layout diagram showing an example of a CGS system to which the present invention is applied, and Figure 3 is a building consisting of Figure 4 shows changes in heat load, heat radiation amount, and thermoelectric ratio at each time of
The figure shows the amount of power generated when CGS is controlled using the optimal control system for the same building. Figure 5 shows the relationship between the amount of electricity purchased and the t-load. Figure 5 shows the cost saving rate of energy consumption when operating a CGS with an optimal control system installed, and the energy consumption when operating a CGS without an optimal control system installed. It is a diagram comparing cost saving rates of energy costs. 1.-Private generator, 2..Engine. 3. Heat recovery device (cold/hot water generation) 4. Heat exchanger for heat radiation, 5. Exhaust gas heat exchanger. 6. Empty MS group, 9. Hot water storage tank. 13. Heat exchanger for cooling. 14... Heat exchanger for heat radiation. 15... Computer computer lab 3 Figure 4 Time Figure 5

Claims (1)

[Claims] In a building or facility that has a private power generator and a heat recovery device, the power demand and heat demand of the building or facility are predicted, and the momentary power demand and heat demand are measured in real time, and the formula ( In order to maximize the cost saving rate (SC) shown in 1),
An optimal control method for a cogeneration system characterized by controlling the operating conditions of the generator and the heat recovery device, SC=(C_1-C_2)/C_1×100...(1
) However, C_1 is the cost of energy consumed when heat and power demand is supplied without using CGS (cogeneration system), and C_2 is the cost of energy consumption when the same heat and power demand is supplied by CGS. Represents cost.