GB2387641A

GB2387641A - Combined heat and power unit

Info

Publication number: GB2387641A
Application number: GB0209006A
Authority: GB
Inventors: Derek Cope
Original assignee: GASFORCE Ltd
Current assignee: GASFORCE Ltd
Priority date: 2002-04-19
Filing date: 2002-04-19
Publication date: 2003-10-22
Also published as: GB0209006D0

Abstract

The unit 10 includes a fan 20, an engine 30, an electrical generator 50, a heat recovery unit 60, and a boiler 120. The engine may be a reciprocating engine, a Wankel or Stirling engine, or a gas turbine. The boiler is controlled to produce a heated water supply on demand by receiving water from the heat recovery unit via pipe 100. The boiler includes a modulating burner 115 and may have a condensing unit. Waste heat and exhaust emissions from the burner are directed towards a plate heat exchanger of a radiator 40 to further increase hot water generated. The fan directs air toward the electrical generator and the engine, which has a cooling system. Hot water in the cooling system is fed through the heat exchanger in the radiator 40 and then into the heat recovery unit 60. An inlet 70 and outlet 80 connect the unit 10 to a conventional hot water system.

Description

10 In comb À he 'wum( eel CODE He 1 Sol I electrical current and heat.

Electrical current is produced by means of a generator driven by an engine such as a reciprocating engine, a Wankel engine a Sterling engine or a gas turbine. Heat is produced from cooling systems and exhaust gases of the engine. Conventional low pressure hot water combined heat and power systems typically comprise a gas turbine driving electric generator which provides a portion of the power required by a building. Waste heat from the combustion process in the engine is collected from the engine cooling system and exhaust system and transferred to a low 20 pressure hot water system by way of separate heat exchangers. The hot water is pumped around the building to provide hot water for radiators, domestic hot water systems and possibly to air handling unit heating coils. Such systems are typically used in, for example, leisure centres and swimming baths, hotels, hospitals and sheltered housing. Unfortunately, the take- up of gas turbine CHP units has been much lower than expected. Some of the reasons for this are that gas prices have risen whilst electricity prices have fallen, the initially high cost of the units results in an extremely long pay back period and, perhaps most importantly, the fact that a thermal output is produced 30 irrespective of demand and often results in waste during the summer.

The fact that heating output is directly related to electricity generation has meant that buildings using CHP systems that constantly needed electricity power had hot wan 1 238764 1

COMBINED HEAT AND POWER UNIT

Field of the Invention

5 The present invention relates to a combined heat and power unit suitable for use in the home and also in small-scale commercial and light industrial facilities.

Background to the Invention

available whether it was needed or not. During the summer months, some hotels and leisure centres have been able to utilize the excess heat generated by running air conditioning systems or water coolers. However, the process of generating heat to subsequently reduce the heat of a room or water is obviously wasteful and means that 5 such systems are quite costly during summer months when heating is not required. In addition, it was typically not possible to increase the heat output of CHP units as the gas turbine is normally run at full power.

The present invention seeks to provide a CHP unit in which the thermal output can be 10 controlled in dependences on demand and in which the thermal output can exceed that provided by the generator alone.

Statement of the Invention

15 According to an aspect of the present invention, there is provided a combined heat and power unit comprising an engine driving an electrical generator, a heat recovery unit arranged to capture heat produced by the engine and to heat a water supply with said captured heat and a water heater, wherein the water heater is controlled to heat the water supply upon demand.

By providing an integral water heater such as boiler within the CHP unit, the temperature of the hot water output from the CHP unit can be amplified as and when necessary. In this manner, a relatively low power generator can be incorporated in the CHP unit sufficient to generate electrical power for the home or for small commercial 25 or industrial premises and the resultant cost of the CHP unit can therefore be reduced to be suitable for the home or small industrial or commercial budget.

Brief Description of the Drawines

30 Figure 1 is a schematic diagram of an example of a CHP unit in accordance with the present invention.

- Detailed Description

Figure 1 is a schematic diagram of an example of a CHP unit in accordance with the present invention.

The CHP unit 10 includes a fan 20, an engine 30, an electrical generator 50, a heat recovery unit 60 and a boiler 120.

The engine 30 drives the electrical generator 50 to produce electrical energy. The 10 engine 30 includes an exhaust 35 and a radiator 40. Air is blown into the unit by the fan 20, cooling the electrical generator 50. Having been warmed by the electrical generator 50, the air then enters the engine 30 and its cooling system. Hot water in the cooling system of the engine 30 is fed through a plate heat exchanger within the radiator 40 and hot water generated by the heat exchanger is then fed into a heat IS recovery unit 60. How exhaust gases from the engine are also ducted to the heat recovery unit 60. The heat recovery unit 60 uses a condensing operation to increase the temperature of the hot water from the heat of the exhaust emissions. The hot water is fed into a conventional hot water system or the like, the entry and exit points of which are labelled 70 and 80, respectively. Exhaust emissions are then output from a flue 90.

20 The heat obtained from exhaust gases and by the heat exchanger can increase the hot water temperature by 4 C or more (equivalent to 15 to 35 kWe).

As and when additional hot water or water of an increased temperature is required, generated hot water from the heat recovery unit 60 can be fed into a high efficiency 25 boiler llO. The boiler 110 includes a modulating burner 115 and a condensing unit 120. Heat and exhaust emissions from the burner 115 that are not utilized by the boiler 110 itself are directed towards the heat exchanger of the radiator 40 to further increase hot water generated. The hot water is fed by a pipe system 100 from the hot recovery unit 60 into the boiler 110 and then out into output pipe 80. Flue exhausts from the 30 boiler l lO are output via exhaust port 130 that is coupled to the flue 90.

Using a 35HP rotary internal combustion engine as the engine 30, an 18kWe electrical generator can be driven. If this is combined with a boiler 110 having a 13-70KW

modulating output, 15 to 35kWe of hot water can be permanently provided (for example for kitchen use and hot water storage facilities), increasing to 18 to 103kWe when the boiler is activated.

5 In this manner, a CHP unit capable of delivering a modulating electrical base load and a variable thermal load at a very high operating efficiency can be provided.

It will be appreciated that specific elements within the CHP unit of the present invention could be replaced by equivalents without affecting the overall operation of 10 the present invention. In particular, whilst a condensing unit with a modulating burner is shown as the high efficiency condensing boiler, other boiler types can be envisaged.

In addition, a number of different engines could be used such as reciprocating engines, gas turbines or the like. However, in the case of the engine it is preferred that a rotary internal combustion engine is used (in particular, a rotary engine such as that developed 15 for light aircraft) as benefits of low vibration and noise, long intervals between major service work and relatively low capital outlay can be obtained from such engines. In contrast, reciprocating engines have a much higher maintenance cost, are high in vibration and are noisy whilst gas turbines are currently extremely expensive.

20 The heat recovery unit may be a fully condensing unit such as a condensing flue economizer.

Claims

1. A combined heat and power unit comprising an engine driving an electrical generator, a heat recovery unit arranged to capture heat produced by the engine and to 5 heat a water supply with said captured heat and a water heater, wherein the water heater is controlled to heat the water supply upon demand.

2. A combined heat and power unit according to claim 1, wherein the engine comprises a rotary internal combustion engine.

3. A combined heat and power unit according to claim 2, wherein the engine comprises a light aircraft rotary internal combustion engine.

4. A combined heat and power unit according to any of claims 1 to 3, wherein the 15 water heater comprises a boiler.

5. A combined heat and power unit according to claim 4, in which the boiler comprises a high efficiency condensing boiler.

20

6. A combined heat and power unit according to any preceding claim, in which the engine includes a cooling system coupled to a radiator, wherein the heat recovery unit captures heat from the radiator via a heat exchanger.

7. A combined heat and power unit according to any preceding claim, in which 25 exhaust emissions from the engine are directed into a condensing unit within the heat recovery unit to thereby capture heat from the emissions.

8. A combined heat and power unit according to claim 7, in which the condensing unit comprises a condensing flue economiser.