Cogeneration system

Abstract

In a cogeneration system having a generation unit comprising a generator connectable to an AC power feed line between a commercial power network and an electrical load, and an internal combustion engine for driving the generator and having a coolant circulation passage through which a coolant circulates, there are provided a first heat exchanger installed at the coolant circulation passage of the engine to exchange heat with the coolant, a blower that supplies intake air to the first heat exchanger to exchange heat and heat-exchanged hot air to a hot-air passage, a selector comprising a damper that selectively connects the hot-air passage to a room or to exterior, and a controller that controls operation of the selector based on thermal demand, i.e., to lead the hot air to the exterior when there is no thermal demand.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention This invention relates to a cogeneration system, particularly to a cogeneration system responsive to a case where electric power supply is required when there is no thermal demand.

2. Description of the Related Art

In recent years, cogeneration systems have been developed that are equipped with an internal combustion engine-driven generator for installation in an AC power supply line between a commercial power network and an electrical load for supplying power to the load in interconnection with the power network and also for supplying hot water or the like heated using exhaust heat from the engine to a thermal load. Such a cogeneration system is taught, for example, by Japanese Laid-Open Patent Application No. Hei 8-4586 ('586).

In the prior art configuration according to the technology taught by '586, when surplus electricity is generated, a heater installed in a hot water storage tank is energized to heat the hot water, i.e., the surplus electricity generated is converted to thermal energy for improving energy-saving efficiency, while the stored thermal energy is made available or usable in response to increase in thermal load for enhancing the capacity to respond to load change.

The above-mentioned prior art relates to a cogeneration system that generates hot water using exhaust heat from the engine. In a cogeneration system that generates hot air instead of hot water, a situation may happen in which electric power supply is required when there is no thermal demand.

SUMMARY OF THE INVENTION

An object of this invention is therefore to overcome the foregoing disadvantage by providing a cogeneration system generating hot air by using exhaust heat from an internal combustion engine that, when electric power supply is required at the time of no thermal demand, can supply electric power as required.

In order to achieve the object, this invention provides a cogeneration system having at least a generation unit comprising a generator connectable to an AC power feed line between a commercial power network and an electrical load, and an internal combustion engine for driving the generator and having a coolant circulation passage through which a coolant circulates, comprising: a first heat exchanger installed at the coolant circulation passage of the engine to exchange heat with the coolant; a blower that supplies intake air to the first heat exchanger to exchange heat and heat-exchanged hot air to a hot-air passage; a selector that selectively connects the hot-air passage to a room or to exterior; and a controller that controls operation of the selector based on thermal demand.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects and advantages of the invention will be more apparent from the following description and drawings in which:

FIG. 1 is a block diagram giving an overall view of a cogeneration system according to an embodiment of this invention;

FIG. 2 is an explanatory view showing a hot-air passage of a hot air heater unit shown in FIG. 1; and

FIG. 3 is an explanatory view similarly showing the hot-air passage of the hot air heater unit shown in FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A cogeneration system according to an embodiment of the invention will now be explained with reference to the attached drawings.

FIG. 1 is a schematic diagram showing a cogeneration system according to an embodiment of this invention.

As illustrated, the cogeneration system (designated by reference numeral 10) is equipped with a power generation unit 26 having a generator (GEN) 20 connectable to an AC power feed line (power line) 16 between a commercial power source (commercial power network) 12 and domestic electrical loads (electrical loads) 14, an internal combustion engine (ENG; hereinafter called “engine”) 22 driving the generator 20 and a power controller 24.

The power source 12 generates or outputs single-phase, three-wire, 100/200 V, 50 Hz (or 60 Hz) AC power. The generation unit 26 is integrally formed and housed in a generation unit case 30.

Specifically, as shown in FIG. 1, the generation unit case 30 is divided into two compartments by a partition 30a. The right compartment in the drawing accommodates the generator 20 and engine 22 to be arranged above and below in a vertical direction in the axis of gravity, and the left compartment accommodates the power controller 24. The power controller 24 is isolated from the engine 22, i.e., installed in one of the compartments which does not house the engine 22 so that heat from the engine 22 can be blocked as much as possible.

The engine 22 is a single-cylinder, four-cycle, water-cooled, spark-ignition, OHV engine that runs on the city gas or LP (liquefied petroleum) gas and has a displacement of, for example, 163 cc. Although not shown in the drawing, the cylinder head and cylinder block of the engine 22 is laid in the lateral (horizontal) direction in the generation unit case 30, and a piston is reciprocatingly accommodated therein.

Sucked air supplied from an air intake duct 22a is mixed with gas supplied from a gas supply source. The air-fuel mixture thus produced flows into a combustion chamber and burns upon ignition to drive the piston, thereby rotating the crankshaft connected to the piston in a longitudinal (vertical) direction in the generation unit case 30. The generated exhaust gas passes through an exhaust pipe and an exhaust duct 32 connected to the generation unit case 30 and is discharged to the exterior of a room(s).

A coolant circulation passage 34 is formed in the vicinity of heating region such as the cylinder block and the coolant composed of antifreeze liquid circulates therethrough. The coolant exchanges heat with the heating region to rise its temperature, as cooling the engine 22, and passes through an exhaust-air heat exchanger (first heat exchanger) 36 installed along the exhaust pipe to be further heated.

A flywheel attached to the upper end of the crankshaft has magnet pieces on the inside surface that are arranged to face multipolar coils constituting the generator 20. The generator 20 produces alternating current when the flywheel rotates such that the multipolar coils cross the flux emitted from the magnet pieces. The output of the generator 20 is sent to the power controller 24.

Although not shown in the drawing, the power controller 24 comprises an electronic control unit (ECU) constituted as a microcomputer, an inverter and a DC/DC converter. The inverter inverts the DC output of the DC/DC converter to 100/200 V AC power (single phase).

The output of power generation of the generation unit 26 is 1.0 kW or thereabout. The output of the inverter is connected to the power feed line 16 via a breaker 38. When, on the other hand, the generator 20 is supplied with power from the power source 12 via the inverter, it functions as a starter motor for cranking the engine 22.

The ECU of the power controller 24 switches the function of the generator 20 between the starter and the generator, and controls the operation of the engine 22 and the like.

The cogeneration system 10 includes a hot-air heating unit 40 in addition to the generation unit 26.

The hot-air heating unit 40 comprises an exhaust heat exchanger (first heat exchanger) 42 connected to the coolant circulation passage 34 of the engine 22, a burner 44 having an intake pipe 44a1 and an exhaust pipe 44a2, a sensible heat exchanger (second heat exchanger) 44b and latent heat exchanger (second heat exchanger) 44c installed at the exhaust pipe 44a2 for exhausting combustion gas generated in the burner 44, a blower 46 that supplies intake air to the exhaust heat exchanger 42 and at least one of the sensible heat exchanger 44b and latent heat exchanger 44c, specifically the both of them, to exchange the heat and supplies the hot air thus generated to the interior of the room(s) through a hot-air passage, and a hot-air heating unit controller (controller) 50.

The hot-air heating unit 40 is housed in a hot-air heating unit case 52 and connected to each room through the hot-air passage.

FIGS. 2 and 3 are explanatory views showing the hot-air passage (now assigned by 54) and the like. The hot-air passage 54 is installed with a damper (selector) 56 that selectively connects the hot-air passage 54 to either the interior (inside of the room) or the exterior (outside). The damper 56 is comprises a door that can be opened or closed by an electric motor 56a.

The electric motor 56a is connected to the power feed line 16 to be supplied with power. The operation, i.e., the open/close operation of the damper 56 is controlled by the hot-air heating unit controller 50. FIG. 2 shows the damper 56 that connects or leads the hot-air passage 54 to the exterior (outside) and FIG. 3 shows the same that connects the hot-air passage 54 to the room (interior).

The foregoing configuration will be explained for each.

The generation unit 26 is connected to the hot-air heating unit 40 through the coolant circulation passage 34. Specifically, the coolant circulation passage 34 extends from the engine 22 toward the hot-air heating unit 40, is connected to the exhaust heat exchanger 42 positioned near the blower 46, and returns to the engine 22. In the exhaust heat exchanger 42, air flowing through the coolant circulation passage 34 is heat-exchanged with cold air of the rooms.

Cold air is warmed up by the heat exchange in the exhaust heat exchanger 42 to be hot air, supplied to the hot-air passage 54 through an air duct (not shown) by the blower 46, and, as shown in FIG. 3, passes through the hot-air passage 54 to be supplied to each room, thereby warming up the rooms.

The burner 44 sucks in air from the exterior or outside through the intake pipe 44a1 by using a combustion fan and mixes the sucked air with supply gas to burn. The combustion gas thus generated passes through the sensible heat exchanger 44b and latent heat exchanger 44c and is discharged from the exhaust pipe 44a2 to the exterior.

The sensible heat exchanger 44b and latent heat exchanger 44c warm up air passing through the air duct (not shown) of the blower 46 by the heat exchange. Specifically, the sensible heat exchanger 44b releases heat above the dew point of combustion gas and the latent heat exchanger 44c releases heat at or below the dew point. Condensate water generated in the latent heat exchanger 44c is discharged to the exterior through a drain pipe (not shown).

The blower 46 sucks in cold air from the rooms and supplies hot air which has been warmed up by the heat exchange by the exhaust heat exchanger 42 and further heated and warmed up by combustion by the burner 44, to the rooms through the air duct for warming the rooms.

The hot-air heating unit controller (hot-air controller) 50 is equipped with an ECU (electronic control unit) constituted as a microcomputer similarly to the ECU of the power controller 24. The ECU of the hot-air controller 50 is connected to the ECU of the power controller 24 to be able to communicate and also connected to a remote controller 60 to be able to communicate. The remote controller 60 is operated by the user to set a desired room temperature or the like.

Temperature sensors indicated by “T”, a valve by “V” and a pump by “P” in FIG. 1 are electrically connected to the hot-air controller 50, although signal lines are partially omitted in the drawing. Based on the outputs of the temperature sensors 62, 64, 66, the hot-air controller 50 controls the operation of the valve V and pump P to control engine exhaust heat recovery and the operation of the blower 46 and burner 44.

In other words, the hot-air controller 50 drives the exhaust-heat pump 70 to pump the coolant flowing through the coolant circulation passage 34 to the exhaust heat exchanger 42 for exchanging heat between circulating water in the coolant circulation passage 34 and the cold air of the rooms sucked in by the blower 46.

In order to avoid corrosion due to accumulation of condensate water in the exhaust-air heat exchanger 36 and taking the engine oil durability into account, the hot-air controller 50 controls such that the coolant temperature at the inlet of the engine 22 becomes, for example, 70° C.

The operation of the hot-air controller 50 will be further explained.

First, the explanation is made on a case of operating the cogeneration system 10 in interconnection with the commercial power source 12.

(a) Heating Operation

The hot-air controller 50 compares the outputs of the temperature sensors 62 (sensors installed in the respective rooms are collectively assigned by 62) with the temperature (desired temperature) set by the user through the remote controllers 60 (remote controllers installed in the respective rooms are collectively assigned by 60), and sends a command to the power controller 24 to operate the generation unit 26 when the detected temperature is lower than the set temperature, while terminating the operation when the detected temperature has reached the set temperature. Subsequently, this procedure is repeated.

(b) Burner Operation

When the detected temperature does not reach the set temperature after a lapse of a specified time period or when a difference between the detected temperature and set temperature (desired temperature) exceeds a predetermined value, the hot-air controller 50 determines that the operation only by the generation unit 26 is insufficient and operates the burner 44 to burn until reaching the set temperature for supplying the hot air heated by the burner 44 to the rooms by the blower 46. Once the detected temperature has reached the set temperature, the hot-air controller 50 terminates the operation of the burner 44.

Thus the hot-air controller 50 controls the operation of the burner 44 to burn when the room temperature is lower than the desired temperature, thereby causing the hot-air temperature to rise.

(c) No Heating Requirement Case

As mentioned in the foregoing, electric power supply may be required when heating is not needed, i.e., there is no thermal demand. For instance, there can be a case where electric power is supplied when power from the commercial power network (commercial power source) 12 is insufficient, that is, a case where heating is not required at the time when a main-heat sub-electricity operation is not conducted. More specifically, it is a case that, when the generation unit 26 is operated to supply power to the electrical load 14, thermal energy of hot air is also supplied. Another example is a case where the detected temperature is higher than the set temperature.

In this case, the hot-air controller 50 energizes the motor 56a of the damper 56 to operate the damper 56 from the position shown in FIG. 3 to that shown in FIG. 2, specifically, controls the operation of the damper 56 so that the hot-air passage 54 is connected or lead to the exterior (outside).

Owing to the foregoing configuration, it becomes possible to drive the generation unit 26 to supply power to the electrical load 14 as required. The hot-air controller 50 returns the damper 56 from the position shown in FIG. 2 to that shown in FIG. 3 upon termination of the power supply operation.

Next, the explanation is made on a case of independently operating the cogeneration system 10 separated from the commercial power source 12 when, for example, a power failure occurs in the power source 12.

In this case, the power controller 24 activates the generation unit 26 simultaneously with occurrence of a power failure. The ECU of the power controller 24 operates the generation unit 26 to generate power corresponding to the electrical load 14. Since the voltage decreases with increasing electrical load and the voltage increases with decreasing electrical load, the ECU regulates the power generation output so as to keep the voltage constant.

When the generation unit 26 is operated, including a period during idling operation with no power output, the thermal output is generated. The hot-air controller 50 conducts the heating operation, burner operation and the like on thermal demand, similarly to the above-mentioned case of working together with the commercial power source 12. Also, the hot-air controller 50 controls the operation of the damper 56 when there is no thermal demand as mentioned above.

As stated above, the embodiment is configured to have a cogeneration system (10) having at least a generation unit (26) comprising a generator (20) connectable to an AC power feed line (power line) 16 between a commercial power network (commercial power source) (12) and an electrical load (14), and an internal combustion engine (22) for driving the generator and having a coolant circulation passage (34) through which a coolant circulates, comprising: a first heat exchanger (exhaust-air heat exchanger 36, exhaust heat exchanger 44) installed at the coolant circulation passage of the engine to exchange heat with the coolant; a blower (46) that supplies intake air to the first heat exchanger to exchange heat and heat-exchanged hot air to a hot-air passage (54); a selector (damper) (56) that selectively connects the hot-air passage to a room or to exterior; and a controller (hot-air controller) (50) that controls operation of the selector based on thermal demand.

Since the operation of the damper (selector) (56) is controlled based on thermal demand, i.e., is controlled to connect or lead the hot-air passage 54 to the exterior in a case where electric power supply is required when there is no thermal demand, it becomes possible to supply power as required. The same can be applied to a case where the room temperature is higher than the desired temperature.

The system further includes: a burner (44) that burns a mixture of fuel and air to heat the hot air and having an exhaust pipe (44a2) through which combustion gas generated by the burning is discharged to the exterior; and the blower (46) supplies the hot air to the hot-air passage (54).

The system further includes: a second heat exchanger (sensible heat exchanger 44b, latent heat exchanger 44c) installed at the exhaust pipe (44a2) of the burner (44); and the blower (46) supplies the intake to the second heat exchanger to exchange heat.

In the system, the second heat exchanger comprises a sensible heat exchanger (44b) and a latent heat exchanger (44c) installed at the exhaust pipe (44a2).

In the system, the selector is composed of a damper 56 installed in the hot-air passage 54. With this, in addition to the foregoing effect, the hot-air passage 54 can be easily connected to the inside or outside (exterior) of the room.

In the system, the controller controls the operation of the burner (44) to burn when temperature of the room is lower than a desired temperature (set temperature). With this, in addition to the foregoing effects, it becomes possible to avoid insufficiency of heat supply by burning the burner 44 in response to thermal demand.

It should be noted that, in the foregoing although a gas engine using gas fuel such as the city gas or LP (liquefied petroleum) gas is taken as an example of the power source of the generator 20, an engine instead can be one utilizing gasoline fuel or the like.

It should also be noted that, although the output of the generator 20, displacement of the engine 22 and the like are shown by specific values, they are only examples and not limited thereto.

Japanese Patent Application No. 2007-212979 filed on Aug. 17, 2007, is incorporated herein in its entirety.

While the invention has thus been shown and described with reference to specific embodiments, it should be noted that the invention is in no way limited to the details of the described arrangements; changes and modifications may be made without departing from the scope of the appended claims.

Claims

1. A cogeneration system having at least a generation unit comprising a generator connectable to an AC power feed line between a commercial power network and an electrical load, and an internal combustion engine for driving the generator and having a coolant circulation passage through which a coolant circulates, comprising:

a first heat exchanger installed at the coolant circulation passage of the engine to exchange heat with the coolant;

a blower that supplies intake air to the first heat exchanger to exchange heat and heat-exchanged hot air to a hot-air passage;

a selector that selectively connects the hot-air passage to a room or to exterior; and

a controller that controls operation of the selector based on thermal demand.

2. The system according to claim 1, further including:

a burner that burns a mixture of fuel and air to heat the hot air and having an exhaust pipe through which combustion gas generated by the burning is discharged to the exterior;

and the blower supplies the hot air to the hot-air passage.

3. The system according to claim 2, further including:

a second heat exchanger installed at the exhaust pipe of the burner;

and the blower supplies the intake to the second heat exchanger to exchange heat.

4. The system according to claim 3, wherein the second heat exchanger comprises a sensible heat exchanger and a latent heat exchanger installed at the exhaust pipe.

5. The system according to claim 1, wherein the selector comprises a damper installed in the hot-air passage to lead the hot to the room or to the exterior.

6. The system according to claim 5, wherein the damper comprises a door.

7. The system according to claim 2, wherein the controller controls operation of the burner to burn when temperature of the room is lower than a desired temperature.

8. The system according to claim 3, wherein the controller controls operation of the burner to burn when temperature of the room is lower than a desired temperature.