GB2375147A

GB2375147A - Electrical power generation using turbine driven by compressed gas

Info

Publication number: GB2375147A
Application number: GB0102986A
Authority: GB
Inventors: Michael Brian Kemp
Original assignee: Individual
Current assignee: Individual
Priority date: 2001-02-07
Filing date: 2001-02-07
Publication date: 2002-11-06
Also published as: GB0102986D0

Abstract

An electrical generator 16 is driven by a turbine which is driven by compressed gas (such as air) supplied from a container 12, or a distribution network connected to a central reservoir. The supply of compressed gas to the turbine may be controlled by a valve which may be responsive to failure of a main power supply and incorporate pressure regulating means. The turbine may be of the axial flow type or radial flow type and comprise multiple stages, and a voltage stabiliser 20, may be provided.

Description

ELECTRICAL POWER GENERATION This invention relates to electrical power generation and in particular concerns a method and apparatus for providing electrical power independently of the mains supply.

t It is often necessary to provide electrical power independently of the mains supply, For instance, auxiliary power systems are often found in buildings such as hospitals and other power critical installations so that electric power can be maintained in the event of disruption of the mains supply. These systems tend to comprise complex and costly generation plant in the form of diesel engine generators capable of generating several hundred ofKWs of electrical power. For low energy systems low cost stored energy devices such as batteries can be used but these devices tend to be bulky, require constant maintenance and frequent re-charging. Fuel cells provide an alternative to batteries but are costly by comparison.

There is a requirement to provide electricity in circumstances where other fuels are not available, in particular for emergency use when a mains supply and/or an emergency electricity generator has failed.

According to one aspect of the invention there is provided an apparatus for electrical power generation comprising : a gas container for compressed gas; a turbine in flow communication with the gas container for expansion of gas

discharged from the said container; generator means connected for rotation with the said turbine for electric power generation. The above mentioned apparatus readily enables electricity to be generated in almost any environment. The apparatus may be used to provide auxiliary

power in the event of disruption of the main supply or at locations remote from the , main supply. The apparatus provides a low cost alternative to stored energy devices such as batteries and/or fuel cells and may also be used as an alternative to low power diesel engine generators. The apparatus does not emit any harmful gases and so may be used in environments where diesel or petrol engine generators are inappropriate.

In this respect the apparatus may be used to power individual items of equipment within closed environments such as buildings and in particular individual items of medical equipment in hospitals. The apparatus provides a very compact alternative to stored energy devices such as batteries and fuel cells as significant power may be generated from a relatively small volume of highly compressed gas.

The apparatus may comprise valve means for selective discharge of gas from the container. In this way the apparatus may be switched on and off as required by operation of the valve means. This provides a convenient source of instantaneous power which is available on demand.

Preferably, the valve means is responsive to failure of a main power supply, whereby the apparatus provides a back up power supply. In this way the apparatus can respond automatically to a disruption in the main power supply. This provides for continued operation of safety critical equipment.

The valve means may comprises pressure regulating means for regulating the pressure of the gas discharged to the turbine. This allows the power output of the generator means to be controlled according to the amount of power required so that the energy

of the compressed gas can be conserved. The pressure regulator means also allows , the apparatus to respond to changes in power demands and also allows the pressure to be optimised for efficient operation of the turbine.

In preferred embodiments the gas is compressed air. This minimises operational costs of the apparatus and readily allows the gas container to be recharged using an air compressor. Compressed air may be supplied from a centralised supply by connection of the turbine to a compressed air distribution network, for instance by connection to a wall mounted supply valve. Compressed air distribution networks are common in buildings such as hospitals and factories where compressed air is stored in high volume pressurised containers.

In one embodiment the turbine may be an axial flow turbine. This provides a small diameter turbine.

In another embodiment the turbine may be a radial flow turbine. This provides a turbine having a short axial length but larger diameter.

Additionally the turbine is a multi-stage turbine. This provides for an efficient expansion of the pressurised gas an thereby maximises the energy recovered by the

turbine to drive the generator.

Preferably, the apparatus further comprises a voltage stabiliser for stabilising the output voltage of the said generator means. In this way the output voltage of the

generator can be matched to that of the main supply or the operating voltage of the , electrical equipment to be powered.

According to another aspect of the invention there is provided a method of generating electrical power comprising the steps of :- discharging compressed gas from a gas container; expanding the said gas in a turbine in flow communication with the gas container; and said turbine driving generator means to generate electrical power.

Various embodiments of the invention will now be more particularly described, by way of example only, with reference to the accompanying drawings, in which: Figure I is a schematic representation of an arrangement of an electrical power generation apparatus according to an aspect of the invention; Figure 2 is a schematic representation of a further arrangement according to an aspect of the present invention; Figure 3 shows an axial flow turbine; and Figure 4 shows a radial flow turbine.

Referring now to Figure 1, apparatus for generating electrical power 10 comprises a pressurised gas container 12, a turbine 14, an electrical generator 16, which is connected to the turbine by means of a drive shaft 18, and a voltage stabiliser 20. The gas container is provided by a high pressure cylinder containing air compressed to

several tens of bars. The air cylinder has typical dimensions of 0. 3 metre diameter I and 1. 5 metre length. The air cylinder is connected to a valve 22 positioned at the neck of the air cylinder. The valve is connected to an air pressure regulator 24 which controls the discharge pressure of the air cylinder when the valve 22 is moved to an open position. An air conduit 26 is provided between the regulator 24 and an entry section of an air turbine 14.

In use, air is discharged from the air cylinder to the turbine 14 where the air is expanded through turbine blades (not shown) of a turbine rotor (not shown) which causes the rotor to rotate and drive a generator rotor (not shown) via drive shaft 18.

Electrical power generated by the generator 16 is fed to the voltage stabiliser 20 where the output voltage of the generator is matched to the required voltage of a load 22 which electrical power is generated for. The load 22 may comprise any electrical load and may be additionally connected to a mains electrical power supply such that the apparatus 10 provides an auxiliary back up power supply in the event of disruption to the main supply.

Referring to Figure 2 in a second arrangement compressed air is supplied to the turbine 14 from a terminal 28 in a distribution network (not shown) connected to a central reservoir (not shown) of compressed air. In the arrangement of Figure 2 the

air cylinder 12 is replaced by the compressed air supply terminal 28 and is therefor relevant to installations having a distributed supply of compressed air such as factories, hospitals and similar installations.

Referring the Figure 3, in one arrangement the turbine 14 is an axial flow turbine f comprising a rotor 30 rotatably mounted within a circular cylindrical rotor housing 32. The rotor comprises a plurality of circumfrentially spaced aerofoil shaped rotor blades 34 with which are mounted on a rotor shaft 36 and extend radially between the outer circumference of the shaft 36 to the inner circumference of the housing 32. In use high pressure air entering the turbine in the direction indicated by arrow 38 is expanded as it passes the rotor blades 34 so that it exits the turbine at lower pressure in the direction indicated by arrow 40. The expansion of the compressed air causes the rotor 30 to rotate and drive the drive shaft 18 of the generator.

In another arrangement the air turbine is provided by a radial flow turbine as shown in Figure 4. The radial flow turbine of Figure 4 comprises a central impeller 40 having a plurality of circumfrentially spaced vanes 42 which extend radially from a hub section 44 to a rim 46. The impeller is mounted in a casing 50 radially inwardly of circumfrentially spaced exit guide vanes 48 which direct air exiting the impeller in the direction indicated by the arrows 50 to a pair of turbine exit sections 54. In the view of Figure 4 air enters the turbine impeller 40 in a direction perpendicular to the plane of the drawing and moves radially outwards between the vanes 42 before passing through the exit vanes 48.

Although the invention has been described with reference to the embodiments shown in the accompanying drawings it is to be understood that the invention is not limited to those precise embodiments and that various changes and modifications may be effected without further inventive effort. For example, the turbine shown in Figure

3 and Figure 4 could be modified to provide further stages of turbine rotors for , additional and/or more efficient expansion of the compressed air. In addition the valve 22 can be linked to a micro processor control unit for monitoring the status of the mains supply. In this way the valve 22 may be activated by the control in response to interruption of the main supply so that the apparatus 10 can provide immediate auxiliary power.

Claims

CLAIMS 1. Apparatus for electrical power generation comprising: a gas container for compressed gas;

a turbine in flow communication with the gas container for expansion of gas , discharged from the said container; generator means connected for rotation with the said turbine for electric power generation.
2. Apparatus as claimed in Claim 1 wherein valve means is provided for selective discharge of gas from the container.
3. Apparatus as claimed in Claim 2 wherein said valve means is responsive to failure of a main power supply, whereby said apparatus provides a back up power supply.
4. Apparatus as claimed in Claims 2 or 3 wherein said valve means comprises pressure regulating means for regulating the pressure of the gas discharged to the turbine.
5. Apparatus as claimed in any preceding Claim wherein said gas is compressed air.
6. Apparatus as claimed in any preceding Claim wherein said turbine comprises

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an axial flow turbine.
7. Apparatus according to any of Claims I to 5 wherein said turbine is a radial flow turbine.

,
8. Apparatus according to any preceding Claim wherein said turbine is a multi- stage turbine.
9. Apparatus according to any preceding Claim further comprising a voltage stabiliser for stabilising the output voltage of the said generator means.
10. A method of generating electrical power comprising the steps of :- discharging compressed gas from a gas container; expanding the said gas in a turbine in flow communication with the gas container; and said turbine driving generator means to generate electrical power.
11. Apparatus for electrical power generation substantially as hereinbefore described with reference to the accompanying drawings.
12. A method substantially as hereinbefore described with reference to the accompanying drawings.