JPH0721362B2 - Waste heat recovery power generator - Google Patents

Description

TECHNICAL FIELD The present invention drives an electric generator using an internal combustion engine as a prime mover to generate electric power, supplies the electric power to an electric load, and recovers heat generated by the operation of the prime mover. The present invention relates to a waste heat recovery type generator device that stores heat in a heat storage tank and supplies the heat to a heat load.

<< Conventional Technology and Problems >> FIG. 1 shows a typical conventional configuration of this type of waste heat recovery type power generator. The prime mover 1 is an internal combustion engine such as a diesel engine or a gas engine, by which the generator 2 is rotationally driven, and its generated output is supplied to the electric load 3.
A water-water heat exchanger 5 for recovering waste heat is provided in the cooling water circulation passage of the cooler 4 of the prime mover 1, and the secondary side hot water thereof is guided to the heat storage tank 6. Further, an exhaust gas boiler 8 is provided in the middle of the exhaust pipe 7 of the prime mover 1, whereby hot water is produced by the heat of the exhaust gas and introduced into the heat storage tank 6. In addition,
When the cooling water temperature at the inlet of the cooler 4 is lower than the set value, the solenoid valve 9 is open and the solenoid valve 10 is closed. When the cooling inlet temperature exceeds the set value, the solenoid valve 9 is closed and the solenoid valve 10 is opened, and the cooling water also passes through another water-water heat exchanger 11. A cooling tower 12 is provided on the secondary side of the heat exchanger 11 to promote cooling of cooling water.

In this way, the waste heat is recovered from the system of the cooler 4 and the system of the exhaust pipe 7 of the prime mover 1 and stored in the heat storage tank 6 in the form of hot water. The recovered waste heat is supplied from the heat storage tank 6 to the heat load 13.

If the amount of heat consumed by the heat load 13 and the amount of waste heat recovered in the heat storage tank 6 are in balance, the temperature of the heat storage tank 6 is kept substantially constant, and a stable steady operation state is achieved. The amount of heat recovered in the heat storage tank 6 naturally depends on the amount of heat generated by the prime mover 1. The heat generation amount of the prime mover 1 changes according to the fluctuation of the electric load 3. That is, when the electric load 3 increases, the mechanical load of the prime mover 1 also increases, the output increases, and the amount of heat generation increases.

Therefore, in the conventional device, when the electric load 3 changes,
The temperature in the heat storage tank 6 changes. This becomes a serious problem when the heat load 13 is operated only by the heat from the heat storage tank 6. For example, if an absorption refrigerator is used as the heat load 13 and it is operated only by the heat from the heat storage tank 6, it is necessary to maintain the temperature of the heat storage tank 6 at about 85 to 90 ° C. When the heat generation amount of the prime mover 1 decreases below the rated value, the temperature of the heat storage tank 6 decreases, and the operation efficiency of the absorption refrigerating machine and the like greatly decreases. Due to this problem, in the conventional device, in order to maintain the temperature of the heat storage tank 6 at a predetermined value, the consumed heat amount (heat supply amount) of the heat load 13 must be changed according to the fluctuation of the electric load 3, It was very inconvenient.

<Object of the Invention> An object of the present invention is to enable a temperature of a heat storage tank to be effectively stabilized even if an electric load and a heat load fluctuate over a considerably wide range. To provide.

<< Outline of the Invention >> In the device of the present invention, a heat pump driven by a motor operated by a generator output is provided in a system path for collecting the heat generated by a prime mover and storing it in a heat storage tank, which can heat a heat medium. It was configured. In addition, the change in the electric load is detected by the electric power sensor provided on the output side of the generator, the temperature of the heat storage tank is detected by the temperature sensor, and the amount of heating by the heat pump is detected by the motor based on the detected output. By controlling the temperature of the heat storage tank effectively by controlling the temperature of the heat storage tank, the temperature of the heat storage tank is stabilized more reliably without being affected by the fluctuation of the heat load.

<< Embodiment >> FIG. 2 shows the construction of an embodiment of the present invention.
The same or corresponding parts as those of the conventional apparatus shown in FIG. 1 are designated by the same reference numerals.

In the apparatus shown in FIG. 2, a generator 2 is driven by a prime mover 1 such as a diesel engine or a gas engine, a power generation output is supplied to an electric load 3, and a cooler 4 of the prime mover 1 is supplied.
The waste heat is recovered from the system of 1 and the system of the exhaust pipe 7 and stored in the heat storage tank 6, and the heat is supplied to the heat load 13 from the heat storage tank 6 is the same as the conventional one. Detailed description of the same parts as the conventional one will be omitted.

In the device of this embodiment, the secondary side of the water-water heat exchanger 5 that recovers the cooling water heat of the cooler 4 of the prime mover 1, that is, in the system path of the heat medium that guides the recovered heat to the heat storage tank 6. To heat pump
14 is provided, and the heat pump 14 heats the heat medium (water) in the heat storage tank 6.

That is, the heat pump 14 includes a water-air heat exchanger 14a having an input side connected to an output side of the water-water heat exchanger 5, a compressor 14b and a compressor connected to an output side of the water-air heat exchanger 14a. The air-water heat exchanger 14c has an input side connected to the compression output side of 14b.
The output side of 4c communicates with the heat storage tank 6.

Here, the water that has undergone heat exchange by the water-water heat exchanger 5 circulates on the input side of the water-air heat exchanger 14a of the heat pump 14. As a result, the air flowing to the output side of the water-air heat exchanger 14a is heat-exchanged and then compressed by the compressor 14b. The compressed air has a high temperature and is discharged to the input side of the air-water heat exchanger 14c, and the water flowing through the output side is heated.

The heat pump 14 is driven by the variable speed motor 15, and the variable speed motor 15 is controlled by the control circuit 16. The heating capacity of the heat pump can be adjusted by controlling the speed of the motor 15. The motor 15 is driven by the output of the generator 2, and the speed is controlled by the motor control circuit 16.

A power sensor 17 is added to the output system of the generator 2,
As a result, the generated power (power consumption) is detected. That is, the electric power sensor 17 detects a change in the electric load 3.

Further, the heat storage tank 6 is provided with a temperature sensor 18 for detecting the internal temperature, and the temperature change in the heat storage tank 6 due to the fluctuation of the heat load 13 or the like is detected.

The detection outputs of the power sensor 17 and the temperature sensor 18 are control circuits.
16 input signals, and based on these detection outputs, the motor
The speed control of 15, that is, the heating amount control by the heat pump 14 is performed.

As shown in the operation flow of FIG. 3, the motor control circuit 16 fetches the power signal of the power sensor 17 and the temperature signal of the temperature sensor 17 in step S1, and proceeds to step S2 to set the power consumption of the electric load 3 to the set value. To determine whether or not it is decreasing. If the power consumption is lower than the set value, the process proceeds to step S3, and the rotation speed of the motor 15 is increased. Motor 15
If the rotation speed of the air is increased, the compression pressure of the compressor 14b is increased, the temperature of the air on the input side of the air-water heat exchanger 14c rises, and the temperature of the water on the output side of the air-water heat exchanger 14c also rises. The temperature of the water in the tank 6 also rises. After the speed of the motor 15 is increased in step S3, the process proceeds to step S4, and it is determined whether the temperature in the heat storage tank 6 is lower than the set value. If the power consumption of the electric load 3 is not less than the set value in step S2, step S5
Then, it is determined whether the temperature of the heat storage tank 6 is lower than the set value, and if it is lower, the process returns to step S3, and if not lower, the process returns to step S2. Furthermore, if the temperature of the heat storage tank 6 is lower than the set value in step S4, the process returns to step S3.

When the temperature in the heat storage tank 6 detected by the temperature sensor 18 becomes lower than the set temperature, the control circuit 16 increases the rotation speed of the motor 15 according to the difference from the set temperature, and the heat pump 14
The amount of heating due to is increased to raise the temperature of the hot water introduced into the heat storage tank 6. As a result, the temperature of the heat storage tank 6 approaches the set temperature. When the temperature of the heat storage tank 6 reaches the set value, the control circuit 16
Stops the motor 15 or runs it at the lowest speed.

When the power consumption detected by the power sensor 17 is equal to or higher than the rated power, the control circuit 16 stops the motor 15 or operates it at the lowest speed. When the electric load 3 decreases,
The power consumption decreases, the mechanical load of the prime mover 1 also decreases, the heat generation amount of the prime mover 1 decreases, and the heat amount recovered in the heat storage tank 6 also tends to decrease. Therefore, in the device of the present invention, the decrease of the electric load 3 is detected by the power sensor 17,
It is transmitted to the control circuit 16. In response to this, the control circuit 16 increases the rotation speed of the motor 15 according to the amount of decrease in power consumption with respect to rated power. As a result, the heating amount of the heat pump 14 is increased, the reduction of the recovered heat amount due to the reduction of the heat generation amount of the prime mover 1 is compensated, and the temperature drop of the hot water introduced into the heat storage tank 6 is prevented. That is, the control is performed based on the fluctuation of the electric load 3, and the temperature change of the heat storage tank 6 is prevented in advance.

The rotation speed N of the motor 15 under this control is the rated power Po,
The power consumption detected by the sensor 17 is P, and appropriate constants are a and b
Then, it is represented by N = ap / po + b. It should be noted that this control formula is an example, and other control algorithms may be adopted according to the characteristics of the entire control system.

By the way, since the motor 15 is driven by the output of the generator 2, when increasing the heating amount of the heat pump 14, the power consumption of the motor 15 increases, which increases the heat generation amount of the prime mover 1 itself. Reasonable and efficient.

<< Effects of the Invention >> As described in detail above, according to the waste heat recovery power generator of the present invention, the temperature of the heat storage tank is stable even if the electric load and the heat load fluctuate over a considerably wide range. , Even for heat loads that require constant temperature, such as absorption refrigerators,
It is possible to operate efficiently only by supplying heat from the heat storage tank. In particular, the heat pump effectively acts even when the electric load fluctuates to enable effective control, and the temperature change of the heat storage tank is effectively prevented.

[Brief description of drawings]

FIG. 1 is a block diagram of a conventional device, FIG. 2 is a block diagram of a device of one embodiment of the present invention, and FIG. 3 is an operation flow of a motor control circuit. 1 ... motor, 2 ... generator, 3 ... electric load, 4 ... cooler,
5 ... Heat exchanger, 6 ... Heat storage tank, 7 ... Exhaust pipe, 8 ... Exhaust gas boiler, 13 ... Heat load, 14 ... Heat pump, 14a ... Water-water heat exchanger, 14b ... Compressor, 14c ... Air- Water heat exchanger, 15
… Motor, 16… Motor control circuit, 17… Power sensor, 18…
Temperature sensor.

Claims (1)

[Claims] Claim: What is claimed is: 1. An internal combustion engine is used as a prime mover to drive a generator to generate electric power, which is supplied to an electric load. At the same time, heat generated by the operation of the prime mover is recovered and stored in a heat storage tank. A device for supplying heat load, the heat pump being interposed in a waste heat recovery path for guiding the heat generated by the prime mover to the heat storage tank, and operated by a heat pump for heating a heat medium in this system and the output of the generator. A motor for driving the heat pump, an electric power sensor for detecting an increase / decrease in output of the generator, a temperature sensor for detecting a temperature in the heat storage tank, an electric power detection signal of the electric power sensor, and a temperature of the temperature sensor. A waste heat recovery power generator comprising control means for controlling the motor based on a detection signal to control the amount of heating by the heat pump to stabilize the temperature in the heat storage tank.