GB2439832A

GB2439832A - Turbine in power station cooling tower outlet

Info

Publication number: GB2439832A
Application number: GB0712774A
Authority: GB
Inventors: Donald Green
Original assignee: Individual
Current assignee: Individual
Priority date: 2006-07-01
Filing date: 2007-07-02
Publication date: 2008-01-09
Also published as: GB0613088D0; GB0712774D0

Abstract

A power station comprises at least one fluid, preferably, water, driven turbine 22. In a first aspect of the invention the power station further comprises a cooling tower 4 having a fluid inlet and a fluid outlet 6, 8, the turbine(s) 22 being located within the fluid outlet 6, 8 and connected to a generator. The turbine(s) 22 may be selectively removable from the fluid outlet 6, 8, and/or a by-pass channel may be provided to allow the fluid to by-pass the turbine(s) 22. In a second aspect of the invention the power station is a steam power station, and the turbine(s) 22 are hydroelectric and provided in addition to steam turbines of the power station.

Description

I

Power Generation The present invention relates to the generation of power within a power station environment and more particularly, although not exclusively, to a modification to the power plant in order to increase overall efficiency and power output and to allow the generation of power which is supplementary to the conventional power generation means.

Conventional power stations which make use of steam turbine generators employ a cooling system to condense the turbine exhaust steam. Typically such a cooling system will utilise water which is pumped around a circuit comprising at least one condenser and one or more cooling towers. A simplified arrangement of a cooling system of this type is exemplified by figure 1.

Relatively cold water is drawn from a river or other source into a reservoir 24, from which it is pumped to the condenser 28.

The exhaust steam from the steam turbines is condensed back to water within the condenser 28 causing a heated water output from the condensers, which is pumped to the cooling towers.

The water falls under gravity within the cooling towers 4 in order to remove waste heat from the cooling water. The cooled water collects at the base of the cooling tower and flows under gravity via one or more return channels 8 to the reservoir 24 for recirculation or else to a separate station for return to the original source.

In reality, the cooling circuit is more complicated than that shown in Figure 1 in that multiple cooling towers are fed by multiple condensers and recluires the flow of water to be controlled and diverted in accordance with the station operation condition at that time.

In light of the ongoing movement away from the reliance on fossil fuels for power generation, targets have been set for the reduction of fossil fuel consumption in favour of renewable energy sources. In implementing those targets, different castings have been attributed to different sources of power based upon whether or not the sources can be classified as using cgreefl energy.

Whilst it has always been an aim to refine the operation of existing power stations, the more recent changes to the price of energy based upon its classification have made it economical to consider implementation of new refinements to existing power stations.

Therefore the present invention aims to provide for the generation of power within a power station by making use of available renewable sources of energy.

According to a first aspect of the present invention there is provided apparatus for providing a power source at a power station, said power station including one or more cooling towers arranged to receive fluid and to discharge the fluid at a reduced temperature via at least one channel, wherein at least one turbine is located in said at least one channel, said turbine arranged to rotate under the force of the fluid discharged from :. the cooling tower so as to drive at least one generator connected to said turbine. *.S. * * *

In one embodiment a plurality of channels are provided and one or more turbines can be provided in each of the channels.

The present invention is particularly advantageous as a supplemental power source since it makes use of pumped water which is already required for normal operation of the power station in order to generate a supplementary power source.

Since this constitutes a secondary use of the water, the energy generated can be designated as a green' energy source. Thus the economic implications of the installation of the required water turbines is quickly offset by the increased value of the energy created, in such a way that both efficiency savings and cost savings can be achieved.

Typically the fluid which enters the cooling tower has been elevated or heated as a result of being used in steam turbine power generation.

Typically the turbine is an axial flow turbine and preferably the turbine takes the form of a propeller turbine. The turbine may be a variable pitch propeller turbine, often referred to as a Kaplan turbine. The fluid flowing from the cooling towers is typically water.

The location of a turbine within the discharge channel of a cooling tower is particularly advantageous since the fluid exiting the cooling tower has been found to have a predictable and :. ie1atively constant flow rate. Accordingly the orientation of the turbine blades may be fixed along with any associated distributor ***..S means. I. * a

* Preferably the fluid discharged from the cooling towers flows towards the one or more turbines substantially under gravity.

: However such an arrangement will require the turbines to be located below the level of the cooling towers and so such features arc to some extent dependent upon the layout of the power station in question.

According to one preferred embodiment, the turbine is selectively removable from the flow in the channel. In one embodiment the turbine is movable by way of, for example hydraulic rams, such that it can be lowered and raised respectively into and out of the flow path. Alternatively, flow diverting means may be provided to selectively short circuit the turbine as necessary.

In one embodiment there is provided control means located in the force path between the turbine and the generator. Typically the control means controls the rotational speed of the generator relative to the rotational speed of the turbine blades. The control means may take the form of a gearbox or speed increaser.

According to a further aspect the present invention there is provided a turbine for use within a power station, the power station including one or more cooling towers arranged to receive fluid and to discharge the fluid at a reduced temperature via at least one channel, wherein the turbine is arranged to be located within said channel during use and connected to a generator so that the turbine is rotated under the force of fluid discharged from the cooling tower along the channel so as to drive the generator. S...

:. According to a vet further aspect of the present invention there * *:. is provided the use of a hydroelectric turbine within a steam turbine power station, wherein said hydroelectric turbine is used **..

.. : to generate additional power to that generated using the steam turbine generator.

T'picall)', the power station includes one or more cooling towers arranged to receive fluid at an elevated temperature and to discharge the fluid at a reduced temperature via one or more channels, wherein the turbine is arranged to be located within said channels during use and connected to a generator so as to supplement the power produced by the power station.

A method for generating power at a power station, said method comprising the steps of introducing fluid in a heated state into one or more cooling towers of the power station, allowing the fluid to leave the said one or more cooling towers in a cooled condition via at least one channel and wherein the method includes the step of positioning at least one turbine with respect to the channel so as to be driven by the flow of the fluid to drive at least one generator connected thereto.

Preferred embodiments of the present invention are described in further detail below in accordance with the following drawings, n which: Figure 1 shows a general cooling tower flow circuit according

the prior art;

Figure 2 shows a modified cooling tower flow circuit according to the present invention; and Figure 3 shows a general cooling tower flow circuit according to the present invention. * *.S

A study of an existing fossil fuel burning power station within the United Kingdom has revealed that a condenser for a turbo-**..

: generator may require upwards of 18.9 m3/s of cooling water in order to achieve the required cooling effect. In addition auxiliary equipment may require in the region of 0.8 m3/s of cooling water. Therefore, for a power station with three turbo-generators, upwards of 59 m3/s of water (780 000 gal/mm) is required to be supplied.

Turning firstly to figure 1, which shows a general cooling tower flow circuit 2, said flow circuit having the features of a cooling tower 4 with an outlet channel 6, return channel 8, reservoir 24, pump system 26 and condenser 28. This system works by pumping fluid, usually water 30, from a reservoir 24 or water course via a system of pumps 26 to a condenser which cools the exhaust steam from the power station turbines (not shown).

The cooling of the exhaust steam raises the temperature of the water. To coo1 the water it is pumped to an elevated position above the ground 32. As the water 30 enters the cooling tower 4 it is allowed to fall under gravity and is thereby cooled. The water is collected at the base of the cooling tower 4 in one or more outlet channels 6 and returned to the reservoir via one or more return channels 8.

Referring to figure 2, cooling water is received from multiple condensers via conduits 10-12. The water carries heat energy away from the condensers and is therefore at an elevated temperature as it arrives at pumping station 14. A series of pumps are provided at pumping station 14 in order to drive the water to the cooling towers 15 via dock 16. * * * *

*...:* The water is pumped to a height above the ground as it enters **e** . the cooling towers and is then allowed to fall under gravity in :. order to cool the water. Once cooled, the water leaves the * *** *:. cooling towers via outlet channels 18. The outlet channels 18 from each of the cooling towers 15 lead into a single return **** channel or purge line 20. The return channel may lead to a river or an alternative waterway or else may lead to a reservoir such that the water can be reused within the cooling cycle prior to being discharged.

The return channel may take the form of one or more sealed or open channels. Whilst the present invention is ideally suited to open culverts due to the ease of access, it is not to be limited to the same and sealed culverts may also be suitable, provided that adcc1uate access can be made available.

According to the present invention and as illustrated in figures 2 and 3, a hydroelectric turbine 22 is positioned within the return channel such that the head of water leaving the cooling towers acts on the turbine blades, causing rotation thereof. The turbine rotor is connected to a generator via a mechanical linkage so as to drive the generator rotor.

As shown in figure 3 one or more turbines 22 can be positioned in the return channel 8. It is also possible that the turbines may be selectively removable from the flow of the water 30 within the return channel 8, or indeed the flow of water can be selectively diverted from the one or more return channels 8 to power said turbines.

The return channel is found to be particularly suitable since the water is flowing passively at this point in the cycle and the :. available energy is not required for other purposes. In contrast, prior to the cooling towers, work is done on the water to raise it up to a height sufficient for operation of the cooling towers.

Thus any energy reclaimed at this point would simply result in :. increased work being done on the water by the pumps.

Furthermore, when the water collects from the cooling towers, .. : the gravity induced nature of the flow advantageously results in lcss turbulent and more predictable flow characteristics.

The specific type and details of the turbine generator set to be employed will necessarily be determined by the particular site conditions but, due to the likelihood of a high flow rate but a relatively low head of water after falling within the cooling towers, it is envisaged that the most suitable turbine arrangement will be the Kaplan design of axial turbine or propeller turbine. Since the flow conditions have been found to be relatively constant, the turbine may be of an un-regulated design, having fixed blades and distributors.

Given the power output provided by a turbine arrangement according to the present invention, when compared to the power output of the power station as a whole, it is of paramount importance that operation of the power station is not interrupted by installation, operation and/or maintenance of the additional water turbine arrangement. Therefore it is proposed that the turbine arrangement should be installed in such a way that it is selectively removable from the flow of water in the return channel.

This can be achieved by providing the turbine set as a modular unit which can be moved into position in a constrained fashion.

Typically such a unit would be movable on runners or rails. The unit may be actuated by hydraulic rams or one or more lifting arms. Alternatively the turbine may be fixed permanently in :. postuon relative to the channel and flow diverting means may be provided to bypass the turbine as necessary. The turbine arrangement may be provided in a separate channel, the flow in the return channel bing diverted to the separate channel for * operation of the turbine. Alternatively the turbine may be installed within the main channel but maybe bypassed by one or S...

more valve or gate arrangements.

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A preliminary feasibility study has revealed the following results: The energy available in a water flow, or hydraulic power, may be estimated by the formula; li = @ Q g H Where; P1) = hydraulic power available (W) = water density (kg/rn3) Q = volumetric flow rate (m3/s) g = acceleration due to gravity (m/s2) H = net head available (rn) For a large coal-fired power station (i.e. circa 4000 MWh output), typical values would be as follows; Q 120 m3/s 1-I 2 -3 m (at, or very near to, pump reservoir inlet) Substituting these values into the hydraulic power formula yields the following values: = 1000 120, 9.81 x 2 = 2.35 MW and, = 1000 x 120 x 9.81 x 3 = 3.5 MW ***.

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Thus there is estimated to be a potential in the order of 2 to 3.5 :. MW in the cooling water return flow. The hydraulic power * calculated above may be harnessed to generate electricity, by means of installing a turbine generator set, or sets, in the *S..

cooling watcr return flow channel(s). S *

Again, based on a typical large coal-fired power station, there arc likely to be a number of individual cooling water return flow channels, or culverts. Assuming that the total flow in a single culvert is of the order of 20m3/s, then a preliminary sizing of the turbine runner diameter may be determined by the formula; D = / (Q/ {2.2'IH}) = i (20/ {2.2'13}) = 2.2m The rotational speed for this type of turbine will be in the order of 75 -150 rpm, so it is envisaged that a speed increaser will be necessary between the turbine and generator. S. * * * *..* S * *.S. *. * S * S.. S..

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Claims

Claims 1. Apparatus for providing a power source at a power station,

said power station including one or more cooling towers arranged to receive fluid and to discharge the fluid at a reduced ternpcraturc via at least one channel, wherein at least one turbine is located in said at least one channel, said turbine arranged to rotate under the force of the fluid discharged from the cooling tower so as to drive at least one generator connected to said turbine.

2. Apparatus according to claim I wherein there is a plurality of channels provided at the power station.

3. Apparatus according to claim I wherein the fluid entering the OflC or more cooling towers is elevated and/or heated.

4. Apparatus according to claim 1 wherein the turbine used is an axial flow turbine.

5. Apparatus according to claim 4 wherein the turbines are in the form of propeller turbines. *. * * * S..

6. Apparatus according to claim 5 wherein the turbine is a variable pitch propeller turbine of the "Kaplan"-type.

7. Apparatus according to claim 6 wherein the turbines is *:::: located substantially below the level of the cooling tower.

8. Apparatus according to claim 6 wherein the turbines is selectively removable from the flow of fluid in the channel.

9. Apparatus according to claim 8 wherein the turbine is manoeuvred with respect to the flow of fluid in the channels by way of hydraulic ram means.

10. Apparatus according to claim I wherein at least one control means is provided in the force path between the turbine and the generator.

11. Apparatus according to claim 10 wherein the control means controls the rotational speed of the generator relative to the rotational speed of the turbine blades.

1
2. Apparatus according to claim 11 wherein the control means is a gearbox and/or a speed increaser.

13. Apparatus according to claim I wherein the channel has a flow directing means capable of selectively redirecting the flow of fluid thereby bypassing one or more turbines.

14. Apparatus according to claim I wherein the fluid received is water.

:. 15. Apparatus according to claim 14 wherein the fluid discharged from the cooling tower is water.

16. A turbine for use with a power station, the power station . including one or more cooling towers arranged to receive fluid and to discharge said fluid at a reduced temperature through at least one channel, wherein the turbine is arranged to be located within said channel during use and connected to a generator so that the turbine is rotated under the force of the fluid discharged from the cooling tower along said channel so as to drive the generator.

17. A hydroelectric turbine for use within a steam turbine power station wherein said hydroelectric turbine is used to generate additional power to that generated using the steam turbines.

1 8. A method for generating power at a power station, said method comprising the steps of introducing fluid in a heated state into one or more cooling towers of the power station, allowing the fluid to leave the said one or more cooling towers in a cooled condition via at least one channel and wherein the method includes the step of positioning at least one turbine with respect to the channel so as to be driven by the flow of the fluid to drive at least one generator connected thereto. * S * S.. **.. *S*. S. S **.

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