GB2443636A

GB2443636A - Electrical power generation

Info

Publication number: GB2443636A
Application number: GB0622242A
Authority: GB
Inventors: Charles Edward Atkinson; Michael Edward Atkinson
Original assignee: Individual
Current assignee: Individual
Priority date: 2006-11-08
Filing date: 2006-11-08
Publication date: 2008-05-14
Anticipated expiration: 2026-11-08
Also published as: GB2443636B; GB0622242D0

Abstract

Apparatus for power generation comprises a watertight housing 12, an electrical generator 13 located in the housing 12 and at least one rotor 14 located outside the housing 12 with means, preferably a shaft 16, linking the, or each, rotor 14 to the generator 13 so that it can rotate about a first axis A to drive the generator 13. A shroud 18 extends between a first section 19 attached to the housing 12, and a second section 20 remote from the housing 12, the shroud 18 serving to at least partially enclose a plenum P and incorporating first means whereby the apparatus can be mounted on a base 21 and be rotatable relative thereto about a second axis B, and second means whereby the plenum P can be isolated from water in which the installation is immersed. The invention further provides an installation including one or more of the apparatus.

Description

I

APPARATUS, INSTALLATION AND METHOD FOR ELECTRICAL POWER

GENERATION

TECHNICAL FIELD

This invention relates to apparatus, installation and method for electrical power generation.

A power generation process should not itself be the cause of unwelcome waste products or effects. Typically the generation of power by means of steam generated in coal, gas or oil burning power stations results in the dumping into the atmosphere of heat, carbon dioxide along with noxious gaseous and particulate products making a significant contribution to global warming and atmospheric pollution.

A source of energy exists in regular tidal movements in the sea around the 11,000 miles of coastline of the British Isles, not to mention the rest of the world. Very: u.

strong currents are produced along the coast and estuaries by the regular passage of S...

vast quantities of water to produce water levels differing by up to 12 metres within a 6. S...

hour period. In many coastal areas it would be possible to generate electricity for 5.. * : hours on each tide, flood or ebb, this means for up to 20 hours in every 24. As there is a phase difference along the coast there would always be a flood or ebb tide at one location while there is slack water at another.

The aim is to harness the inexhaustible source of natural energy represented by tidal movement for the generation of electricity by a means which is both non-polluting and environmentally unobtrusive.

BACKGROUND ART

Power generation by means of renewable sources of energy are in use or being developed but while not contributing to global warming or atmospheric pollution do suffer from incidental disadvantages.

Hydro electric power generation requires water stored at a relatively high level (and so high potential energy) at a period of high demand for electrical energy can be caused to flow down by way of a turbo generator to a relatively low level from which the water can be pumped back to the high level at a period of low demand. Suitable locations and conditions for this form of generation are relatively scarce and locations tend to be distant from areas of electrical consumption.

*S.e..

Wind power involves the provision of a number of wind mill generators * ..

grouped in a wind farm. A wind powered generator suffer from a minimum threshold wind speed requirement and in the event the wind speed is below that threshold level * then the generator cannot generate useful power. It is now acknowledged that in many areas the threshold levels are only achieved to a limited extent (say for six hours in * twenty four). While there are locations in the British Isles where average wind speed is * : often above such a threshold and for extended periods such locations tend to be remote from consumers and so transmission lines are needed to access a large scale grid system.

Wave generating systems are under review but to produce a reasonable power output would require a substantial area of coast line or river estuary to be closed to water born traffic. It is also not yet clear whether the maintenance of components of a wave generator installation would make them practicable and to also what extent damage would affect their generating capacity.

DiscLosui OF INVENTION According to a first aspect of the present invention there is provided an apparatus for power generation comprising: a watertight housing; an electrical generator located in the housing; at least one rotor located outside the housing; means linking the, or each, rotor to the generator so that the, or each, rotor can rotate about a first axis to drive the generator; and a shroud extending between a first section attached to the housing, and a second section remote from the housing, the shroud serving to at least partially enclose a plenum; the shroud incorporating first means whereby the apparatus can be mounted on a base and be rotatable relative to the base about a second axis, and second means base whereby the plenum chamber can be isolated from water in which the installation is immersed. * S **.* S...

According to a first preferred version of the first aspect of the present invention. : wherein in the apparatus the means linking the, or each, rotor to the generator comprises a shaft extending through a water tight seal into the housing.

According to a second preferred version of the first aspect of the present invention or of the first preferred version thereof wherein in the apparatus the first axis is horizontal.

According to a third preferred version of the first aspect of the present invention or of any preceding preferred version thereof in the apparatus the second axis is vertical.

According to a fourth preferred version of the first aspect of the present invention or of any preceding preferred version thereof in the apparatus the, or at least one, rotor is offset from the second axis.

According to a fifth preferred version of the first aspect of the present invention or of any preceding preferred version thereof in the apparatus vane means are provided for the housing on the opposite side of the second axis to the rotor or rotors so that with the apparatus immersed in water subject to flow the vane means when acted on by the flow serves to turn the housing to cause the first axis to be aligned with the direction of the water flow in a stable configuration.

According to a sixth preferred version of the first aspect of the present invention:1..:.

apparatus according to the fifth preferred version is characterised by the vane means * : serving to align the apparatus relative to the direction of water flow with the, or at **...

least one, rotor up-stream of the housing. : According to a seventh preferred version of the first aspect of the present invention * apparatus according to the fifth preferred version is characterised by the vane means serving to align the apparatus relative to the direction of water flow with the or at least one rotor down-stream of the housing.

According to an eighth preferred version of the first aspect of the present invention or any preceding preferred version thereof the apparatus indudes a fin aftached to the housing, to the shroud or to both housing and shroud providing a stabilisirtg effect to limit angular oscillation of the apparatus about the first axis when located in water flow.

According to a ninth preferred version of the first aspect of the present invention or any preceding preferred version thereof the, or at least one, rotor is of variable pitch.

According to a second aspect of the present invention there is provide an installation for power generation including an apparatus according to the first aspect and any preferred version thereof and a base unit on which the apparatus is mounted so as to provided for the apparatus to be rotatable about the second axis of the apparatus relative to the base unit.

According to a first preferred version of the second aspect of the present invention the installation defines a station for the apparatus adapted to receive the second section of the shroud of the apparatus so as to define a plenum chamber through which the second axis of the apparatus extends.

0S.,.. S...

According to a second preferred version of the second aspect of the present invention Or of the first preferred version thereof the installation provides for the second section *5S*S.

of the plenum chamber to include coupling means for providing a link between the apparatus and the base whereby the plenum chamber can be isolated from water in which the installation is immersed; the coupling means further providing for the.. : apparatus to rotate relative to the base about the second axis of the apparatus.

According to a third preferred version of the second aspect of the present invention or of any preceding preferred version thereof the installation includes in the plenum chamber conducting means whereby electrical power from the generator is fed from the generator to an output station from the apparatus.

According to a fourth preferred version of the second aspect of the present invention or of any preceding preferred version thereof the base incorporates means for linking the output station to a transmission system whereby electrical power can be conducted from the installation to a location remote from the installation.

According to a fifth preferred version of the second aspect of the present invention or of any preceding preferred version thereof the installation comprising at least two apparatus each according to the first aspect of the present invention or of any preferred version thereof.

According to a sixth preferred version of the second aspect of the present invention and of the fifth preferred version thereof the base is common to all said apparatus.

Typically the common base defines a station for each apparatus and each station is adapted to receive the second section of the shroud of the apparatus so as to define a plenum chamber for each apparatus through which the second axis of the apparatus...:.

extends. , :. * *

S.....

According to a seventh preferred version of the second aspect of the present invention:...:.

or of any preceding preferred version thereof the installation is characterised in that each plenum chamber houses conducting means whereby electrical power from the generator is fed from the generator to an output station from the apparatus. Typically the base incorporates means for linking at least two of the output stations to a transmission system whereby electrical power generated by the apparatus can be conducted from the installation to a location remote from the installation.

According to an eighth preferred version of the present invention the installation Is characterised by two or more bases each base being common to one or more apparatus according to the first aspect or any preferred version thereof; each base being located by structural means in a bed of flowing water such as a river bed or a sea bed. Typically the two or more bases are located as aforesaid by a structural means common to all the bases.

According to a third aspect of the present mvention there is provided a method of power generation comprising the steps of: providing a water tight housing for an electrical generator; and at least one rotor located outside the housing, the rotor being enabled to rotate relative to the housing about a first axis; linking the, or each, rotor to the generator so that on rotation of the rotor the generator is caused to generate electrical power; mounting the housing and rotor on a base by means of a shroud so as to enable the housing to pivot about a second axis; immersing the housing, shroud and rotor in water subject to flow relative to the i...:.

housing, shroud and rotor, the water flow being in a direction, and at a speed, either or * both of which can vary with respect to time; : *..:.

providing for the housing and the rotor, to pivot as a combination about the:...:.

second axis so that interaction between the water flow and the rotor is optimised for *e..

power generation by the generator; and * : : : . withdrawing electrical power from the generator.

According to a first preferred version of the third aspect of the present invention the method provides for the first axis to be horizontal.

According to a third preferred version of the third aspect of the present invention or of the first preferred version thereof the second axis is vertical.

According to a fourth preferred version of the third aspect of the present invention or of any preceding preferred version thereof the method provides that the, or at least one, rotor is offset from the second axis.

According to a filth preferred version of the third aspect of the present invention or of any preceding preferred version thereof wherein the indudes the further step of providing vane means for the housing on the opposite of the second axis to the rotor or rotors such that following the step of locating the housing and rotor in water subject to flow the vane means when acted on by the flow serves to turn the housing to cause the first axis to be aligned, and in a stable configuration, with the direction of the water flow. Typically the method provides that with the first axis aligned with the direction of water flow the rotor is positioned up-stream of the housing.

According to a sixth preferred version of the third aspect of the present invention and:...:.

of the fourth preferred version thereof the method provides that with the first axis aligned with the direction of water flow results in the rotor being positioned down-stream of the housing. : e.... * S..

Tidal flow occurs due to the constantly changing relationship of the earth relative to **I.

the Moon and, to a lesser extent, to the Sun. Tidal diamonds shown on Admiralty * Charts denote hourly changes of direction and flow at a given location. In any position at sea the tide does not just flow one way on the flood and the other on the ebb. The tidal flow thanges both speed and direction each hour during the cyde between low and high tide. This directional variation significantly reduces the effectiveness of urn-or bi-directional hydro-turbine. Examples of these are disclosed in GB Patent 2,382,627, US Patent 6,406, 251 and International Patent WO 03/025385 A2. This variation highlights the benefits to be obtained from the present invention which provides a multi-directional, self aligning generator installation which can take advantage of water flowing past the installation regardless of the direction of flow.

Broadly the present invention provides a submerged multi-directional, tidal powered, sea or riverbed, platform based, self aligning generator. The proposed installation can be operated below surface at inland locations and generally sited 10-50 metres below Admiralty Chart Datum at sea, (that is to say well below the draft of most types of local shipping). The generator is pivoted on a fixed mount, and the power is passed into external cables (or conductors) by means of a concentric linear transformer (or slip rings or similar arrangement). Internally the unit has a positively pressurised inert gas atmosphere, providing a constant seal against water entry whilst eliminating oxidization. Employing friction free gas bearing technology (or ceramic, plain, roller, ball, needle bearings) there are no components suffering from wear so promoting longevity. The proposed installation is environmentally clean. There is no contamination through oil or gas leakage. Marine life would remain undisturbed as..:.

the variable pitch turbine blades or rotor blades would spin at low speed so removing * the need for any marine screen. The proposed installations can be based on modular:. * units covering a range of sizes and outputs so enabling a range of demands to be met:...:.

from a single dwelling or an urban area. S... * * *.. *... * S

Previous hydro-turbine applications generally involve surface floats, platforms (US 6,406,215) or piles which are a serious navigational hazard to shipping. Historically, below surface applications have been prone to ingress of water which hampers efficient functioning. The present invention overcomes this, with a positive inert gas atmosphere pressurised to a higher level than that of the surrounding water, providing a constant seal to eradicate oxidization and remove water held in vapour form, thus significantly increasing the longevity of the generator.

BRIEF DESCRIPTION OF DRAWINGS

Figure 1 shows tidal information for Avonmouth; Figure 2 is a diagrammatic view of a first embodiment of apparatus according to the present invention; Figure 3 is a diagrammatic view of a second embodiment; Figure 4 is a diagra.minatic view of a third embodiment; Figure 5 is a diagrammatic view of a fourth embodiment; Figure 6 is a diagrammatic view of a fifth embodiment Figures 7A, 7B are diagrammatic views of a first embodiment of an installation according to the present invention; and Figure 8 is a diagrammatic view of a second embodiment of an installation according to the present invention.

MODES FOR CARRYING OUT THE INVENTION

Figure 1 serves to exemplify tidal range over a given period in this case at Avonmouth in the Bristol Channel. The curve 11 indicates tide height over a 24 hour period induding two low and two high water levels. It will be seen that the mean tidal range of spring tides is shown as 12. 2 metres which indicates the occurrence of strong tidal *..:.

flows. S.. * * S... * * . .

Figure 2 A submerged power generation apparatus 11 includes a watertight housing 12 containing an electrical generator 13. A turbine rotor 14 is located on a boss outside the housing 12. The turbine rotor 14 drives the generator 13 by means of a shaft 16 rotatable about first axis A. A rotary water tight seal 17 is located between the boss and the housing 12 to maintain water tight integrity for the interior of housing 12.

A shroud 18 extends between a first section 19 attached to the housing 12 and a second section 20 remote from the housing 12 to define art internal plenum P. The second section 20 is mounted on base 21 by means of a rotary bearing (which can be of a range of types such as plain, roller, ceramic or gas bearing) providing for rotation of the apparatus 11 relative to the base 21 about second axis B. It is anticipated that in many installations the first axis A will be horizontal arid the second axis B vertical.

Electrical output from the generator 13 is conducted by cable 22 to a concentric linear transformer E (slip rings could be used) to feed a bus bar 23 which provides for generated power to be fed to a consuming location remote from the apparatus 11.

The interior of the housing 12 and of the plenum chamber P are intended to be filled with a suitably inert gas so that effects of moisture and of chemical reactions such as oxidation on items contained in those interiors is prevented.

The apparatus 11 is shown incorporated in an installation 25 in which the apparatus 11 is mounted on base 26 mounted on upper section 27 of pile 28 whose lower section 29 is embedded in river bed 30. As shown in Figure 2 water flow W is from left to right. The installation 25 will generally be located so as to lie at a depth between 10 and 50 meters below water surface S so enabling most vessels to pass over * :.

the installation without damage to either vessel or installation. :...:.

The housing 12 has a leading end 31 which has a profiled leading edge 32. The water flow W acts to rotate the apparatus about second axis B so that the leading end,. *.. **..

31 is directed upstream so that the turbine rotor 14 lies down stream of the housing 12. * : : : A flow stabffising fin 61 is provided on the downstream side of the shroud 16 and serves to smooth flow (such as from vortex) downstream of the shroud 18.

In the case of the apparatus shown in Figure 2 the configuration of the installation 25 with leading end 31 directed upstream and the off-set of the turbine rotor 14 results in a trailing turbine rotor operation.

Figure 3 This shows a second embodiment. In this case a submerged apparatus 41 comprises: a watertight housing 42 for an electrical generator 43. A turbine rotor 44 is located on a boss 45 outside the housing 42. The turbine rotor 44 drives the generator 43 by means of a shaft 46 rotatable about first axis A. The boss 45 has a water tight seal 47 to maintain the water tight integrity of the interior of the housing 42.

A shroud 48 extends between a first section 49 attached to the housing 42 and a second section 50 remote from the housing 42 to define an internal plenum P. Lip seal S provides for the apparatus 41 to be mounted on base 51 and to rotate relative to the base 51 about a second axis B. Electrical output from the generator 43 is conducted by cable C to a concentric linear transformer T (or slip rings or similar arrangement) which leads to a bus bar 53 which provides for generated power to be fed to a consumer location.

The apparatus 41 is shown incorporated in an installation 55 in which the apparatus 41 is mounted on platform 56 mounted on upper section 57 of platform leg 58 whose lower section 59 is embedded in a concrete base 60. As shown in Figure 3 water flow W is from right to left. The installation 55 will generally be located to lie at a depth between 10 and 50 meters below water surface S. The platform 56 incorporates bus bar 53 for transmitting power from generator. :.

43toauserlocation. :...:.

Fins 61 serve to direct the housing 42 to lie downstream of axis B. A flow stabilising fin 61' is provided on the downstream side of the shroud 46 to smooth flow a Ses vortexing downstream from shroud 48. .:::: In the case of the apparatus shown in Figure 3 the configuration of the installation 55, fins 61 and the off-set of the turbine rotor 44 results in a leading rotor configuration in the water flow W while the installation 55 is generating power.

Figure 4 The installation shown here is similar in some respects to that of Figure 2.

However in this case use is made of a turbine rotor whose blade pitch can be varied to optimise operation regardless of fluctuation in water flow speeds.

A submerged power generation apparatus 101 includes a watertight housing 102 containing an electrical generator 103. A turbine rotor 104 is located on a boss 105 outside the housing 102. The turbine rotor 104 rotates a moving part of generator 103 about first axis A. A rotary water tight gas bearing seal 107 is located between the boss and the housing 102 to maintain water tight integrity for the interior of the housing 102. :13

A shroud 108 extends between a first section 109 attached to the housing 102 and a second section 110 remote from the housing 102 to define a plenum chamber P. The second section 110, and so the apparatus 101, is mounted for rotation on a vertical column V extending upwardly from base ill. For this purpose the second section provides a sleeve S incorporating bearings for support on the upper and lower part of the column V to provide for support and relatively free rotation of the apparatus about second axis B'. The second section 110 has around its lower perimeter L a lip seal LL to inhibit the entry of water into the plenum chamber P. When first lowered into position the plenum chamber contains water. Once mounted on the projection V pressurised inert gas is released into the plenum chamber P so as to expel water out of the chamber...:.

through the lip seal LL so as to maintain the plenum chamber P free of water despite * being open at the bottom alter the manner of a diving bell. Typically the pressurised inert gas is contained in a pressure tank housed either in the housing 102 or the Se....

plenum chamber P. The pressure tank is equipped with valve means adapted for remote regulation. * S *

It is anticipated that in most installations the first axis A will be horizontal and the second axis B vertical. However the invention is not limited to this particular axial alignment.

The turbine rotor 104 drives the generator 103 by way of an epicycic torque converter 201.

The angle of attack of each of the blades in the rotor 104 can be varied typically to provide that, within limits, constant generator rotary speed can be established regardless of the water flow speed.

In a given installation it is envisaged that the blade roots and variable pitch installation will be filled with an inert gas from a reservoir in the housing at a pressure higher than that due to water depth so as to prevent leakage into internal moving parts of the system and so maintain the parts free from corrosion and so improve component working life and reliability. A range of seals are available in this context.

The generator 103 comprises a linear alternator mounted on a shaft 202 supported by gas bearing 203. In alternative embodiments ceramic or needle bearings can be used.

Electrical output from the generator 103 is conducted by cable 113 to a concentric linear transformer E (slip rings could be used) to feed a bus bar 114 which provides for generated power to be fed to a consuming location remote from the apparatus 101.

The housing 102 also contains a control unit C for regulating the apparatus and including telemetry equipment so that the state of the unit and its regulation can be undertaken from a remote location.

The apparatus 101 is shown incorporated in an installation 125 in which the * apparatus 101 is mounted on base 126 mounted on upper section 127 of pile 128 whose:.

lower section not shown is embedded in a river bed. As shown in Figure 4 water flow:...:.

Wisfromlefttoright. S S**

The housing 102 has a leading end 131 which has a profiled leading edge 132.

The water flow W acts to rotate the apparatus about second axis B so that the leading end 131 is directed upstream and the turbine rotor 104 lies down stream of the housing 102. A flow stabilising fin 133 on the downstream side of the shroud 108 and serves to smooth flow vortexing downstream of the shroud 108.

In the case of the apparatus shown in Figure 4 the working configuration of the installation 125 is with leading end 131 directed upstream resulting in a trailing turbine rotor configuration.

Figure 5 This shows an installation 501 similar in many respects to that shown, and as described with reference to, Figure 2. The working configuration of the installation 501 has leading end 31' directed upstream and the turbine rotor in a trailing turbine rotor configuration. Where the form and function of components are similar in both the same reference numerals are used in Figure 5 as were used in Figure 2 with the addition of a single inverted comma.

The difference between the embodiments lies in the turbine rotor configuration. Jn Figure 2 a single turbine rotor 14 arrangement is shown. In the embodiment shown in Figure 5 twin rotors 503, 504 are used. These are contra-rotating to eliminate torque reaction associated with the use of a single rotor. The twin rotors 503, 504 are each of variable pitch to provide for operation as briefly mentioned in connection with Figure 4 in relation to a single rotor.

Figure 6 This shows an installation 601 similar in many respects to the installation. . . shown, and described with reference to, Figure 3. That is to say the configuration of the installation 601 results in a leading rotor configuration in the water flow W while * the installation 601 is generating power.

Where the form and function of components are similar in both the same reference numerals are used in Figure 6 as were used in Figure 3 with the addition of a single inverted comma (n').

The difference between the described embodiments lies in the turbine rotor configuration. In Figure 3 a single turbine rotor 14 arrangement is shown. In the embodiment shown in Figure 5 twin rotors 603, 604 are used. These are contra-rotating to eliminate torque reaction associated with the use of a single rotor. Twin rotors each of variable pitch operation can be used as described in connection with Figure 4 in relation to a single rotor. A contra-rotating turbine (Figures 5 and 6), reduces drag and swirl, balancing the torque reaction on the unit of a single rotor and reducing vibration.

In the embodiments described above the generator in each case is pivoted on a fixed mount, and the power is passed into external cables (or conductors). Internally the unit has a pressurised inert gas atmosphere within the enclosure and the shroud, providing a constant seal whilst eliminating oxidization. Employing friction free gas bearing technology (also ceramic, plain, roller, ball, needle bearings) would provide for no significant wearing of parts, thereby promoting longevity. Environmentally clean and with no contamination through oil or gas leakage. Tn many installations marine life would remain undisturbed with variable pitch turbine rotors spinning at low speed so removing the need for any marine screen. A range of turbine rotor configurations can be used having, for

example, twin, triple, quadruple or multi-blades and with curved or aerofoil sections. The generator shows configurations with the turbine rotor either upstream or downstream of their . ,.*. S...

associated enclosure, If the turbine rotor faces upstream a vertical fin can be provided * downstream of the rotor to improve flow stability. * S

S.....

The design lends itself to production in modules of varying size so being suitable for 4S* 5 providing installations whether for a single consumer or for meeting demand from an..

urban area.

Figures 7 and 8 show installations employing a plurality apparatus according to the present invention.

Figures 7A, 7B These variously show an installation in the form of a structure 700 in which six apparatus 701 -706 are mounted on a Common platform 707. The platform 707 is mounted on piles 708 -710 embedded in river bed 711. The individual apparatus work as described in relation to the earlier embodiments. However they export their generated power by means of a common transmission cable 711. In plan view, Figure 7A, the platform 707 is in the form of an equilateral triangle constructed from steel or concrete or any other material ferrous or non ferrous with fixed pivot pins incorporating sheathed soft iron transformer cores or slip ring systems. In this example the platform 707 accommodates six generator units. TI ferrous and unpainted it cart be protected by a sacriuiciai aluminium anode system in conjunction, if necessary, with a marine anti-fouling system.

Figure 8 This shows an installation in the form of a structure 800 in which three sets 801 -803 each of six apparatus (similar to those referred to in Figure 7) are stacked on three common legs 804 -806 embedded in sea bed 607. The generated power is exported to shore by way of a Common cable 807.

The installations shown in Figures 7 and 8 represent a convenient way of assembling a plurality of the generating apparatus for immersion making use of the invention along.

with well established marine construction methods. *

*****S When an installation is first located underwater it is envisaged that the vertical column *SS.

to receive the or each apparatus is protected by a inert gas filled temporary cap which will keep them clean and dry until an apparatus is to be placed on the column. At that point the cap will be lifted off to allow the column to become wet. The apparatus will then immediately be lowered to seat on the column and secured in place for rotation.

Some pressurised gas from the reservoir will then be released into the plenum to expel water from the plenum.

Depending on ocean topography, platforms would be of two or more types primarily piled or gravity. Gravity would be cheaper and more universal whereas a piled structure, subject to depth, would be provide for multiples of platforms to be stacked one above the other (Figure 8) creating a greater concentration of generators from the same fixed area footprint.

Typically the platforms can have three or more legs with base plates which could take compressed air fittings for power jetting in suitable ground conditions. The jetting system pipe work could be taken to a central point on the platform where compressed air lines from the support ship would be attached and air could be directed to all or individual legs to set the platform level. In soft rock or chalk locations it may be necessary to excavate with compressed air hand tools where legs are to be sited.

Gravity type platforms would generally be single platforms accommodating up to six or more generating units and once settled and level on the sea bed, could have leg spikes screwed into the jetting holes, nylon or similar mesh bags of any material could be fixed around each leg to provide a receptacle for concrete or ballast delivered S...

by means of a tremie pipe lowered from a support ship.

In suitable water depths piled platforms would be stacked, six or more:..:.

generators at each level and several platforms high. Being an equilateral triangle. . shaped base all units would be located on the platform perimeter. Any generator at *..S any level can be removed or exchanged using the same hoisting equipment lowered:: :.

from the support ship at slack water between tides. In a multilevel platform such as described above the three inboard platform pile apertures or guides would enable piles to be set at the required dimensions. With the three piles in place passing through the lower platform subsequent platforms could be lowered and secured at a predetermined point above the previous platform (Fig. 8), with adequate clearance allowing removal or replacement of lower level units. This arrangement allows for the generated power to meet at a central point on an individual platform. An aperture allows the power to pass through the platform where the output cables would be taken down to an inert gas filled connection box where they would be connected to a shore cable or conductor. All cable and conductor sizes and sections are dependent on current and the voltage chosen for the shore cable transmission. Once ashore the generated AC power, although the units could produce DC power, could be linked into the national grid for distribution.

The embodiments describe apparatus having the ability to turn into the water flow regardless of the direction and rate of change of direction of the water flow. It is also envisaged that with apparatus which are subject to remote control, means can be provided to limit the ability of the apparatus to change direction so that while still being capable of generation the apparatus will not rotate. Typically this may be desirable to enable inspection, maintenance or repair action to be carried out on the apparatus. A control system would also provide for the rotor shaft/s to be damped to prevent rotation of the rotor for example to allow a diver to gain access to the apparatus or its surroundings. *

The embodiments are intended when in use to have the interior of the housing and of S.....

the plenum to be filled with an inert gas so that the effects of moisture or chemical SI.

reaction can be limited if not prevented. For this purpose a reservoir of pressurised gas can be located in the housing with controlled outlets to the housing, shroud and, where applicable, units associated with the rotor or rotors. The condition of the interior of the housing and the shroud can be readily monitored by means of adaptations of known telemetry systems.

Information as to preferable types of finishes, methods of application and of maintenance has been built up over the years in relation to marine oil rigs which have been used in most climatic and sea conditions around the World.

The embodiments exemplify apparatus which are of unitary COnstructiOn and can be readily positioned and removed from their bases whether on individual sites or platforms. Appropriate anchorages are readily mounted on the housing. Typically this can be at a position relative to its centre of gravity providing for the apparatus to be readily raised or lowered vertically.

INDUSTRIAL APPUCABJLrrY The invention provides a method of electrical generation taking advantage of tidal flow which is a virtually unlimited power resource. The method of generation involved presents no hazards such as atmospheric warming or pollution nor does it provide obstructions to normal marine operations. The constructional methods involved are well established. * .

****** ****

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Claims

Apparatus for power generation comprising: a watertight housing; an electrical generator located in the housing; at least one rotor located outside the housing; means linking the, or each, rotor to the generator so that the, or each, rotor can rotate about a first axis to drive the generator; and a shroud extending between a first section attached to the housing, and a second section remote from the housing, the shroud serving to at least partially enclose a plenum; the shroud incorporating first means whereby the apparatus

S

can be mounted on a base and be rotatable relative to the base about a second * axis, and second means base whereby the plenum chamber can be isolated from...:.

water in which the installation is immersed. *5**

S

S

2 Apparatus for power generation as claimed in Claim I wherein the means linking the, or each, rotor to the generator comprises a shaft extending through a water tight seal into the housing.

3 Apparatus as daimed in any preceding claim wherein the first axis is horizontal.

4 Apparatus as claimed in any preceding claim wherein the second axis is vertical.

Apparatus as daimed in any preceding claim wherein the, or at least one, rotor is offset from the second axis.

6 Apparatus as claimed in any preceding claim including vane means for the housing on the opposite side of the second axis to the rotor or rotors such that with the apparatus immersed in water subject to flow the vane means when acted on by the flow serves to turn the housing to cause the first axis to be aligned with the direction of the water flow in a stable configuration.

7 Apparatus as claimed in Claim A wherein with the first axis aligned by the vane means with the direction of water flow the rotor is positioned in the flow up-stream of the housing. * S

*S.... *

8 Apparatus as claimed in Claim 6 wherein with the first axis aligned by the vane * means with the direction of water flow the rotor is positioned in the flow down-* **.S..

stream of the housing.

S.....

S *55.

9 Apparatus as claimed in any preceding claim including a fin attached to the **.* housing, to the shroud or to both housing and shroud providing a stabilising effect to limit angular oscillation of the apparatus about the first axis when located in a water flow.

Apparatus as claimed in any preceding claim wherein the, or at least one, rotor is of variable pitth 11 Apparatus as hereinbefore described with reference to Figure 1 to 6 of the accompanying drawings.

12 Art installation for power generation including an apparatus as claimed in any preceding daim and a base unit on which the apparatus is mounted so as to be rotatable about the second axis of the apparatus.

13 An installation as claimed in Claim 12 wherein the base defines a station for the apparatus adapted to receive the second section of the shroud of the apparatus so as to define a plenum chamber through which the second axis of the apparatus extends.

14 An installation as claimed in Claim 12 in which the second section of the:....

plenum chamber includes coupling means for providing a link between the apparatus and the base whereby the plenum chamber can be isolated from S....

water in which the installation is immersed; the coupling means further providing for the apparatus to rotate relative to the base about the second axis S...

of the apparatus.

An installation as claimed in any of preceding claims 12 to 14 wherein the plenum chamber houses conducting means whereby electrical power from the generator is fed from the generator to an output station from the apparatus.

16 An installation as claimed in any of preceding daims 12 to 15 wherein the base incorporates means for linking the output station to a transmission system whereby electrical power can be conducted from the installation to a location remote from the installation.

17 An installation comprising at least two apparatus each according to arty of preceding claims 12 to 16.

18 An installation as claimed in Claim 17 having a base Common to all said apparatus.

19 An installation as claimed in Claim 17 wherein the common base defines a station for each apparatus and each station is adapted to receive the second section of the shroud of the apparatus so as to define a plenum chamber for each apparatus through which the second axis of the apparatus extends.

An installation as claimed in Claim 19 wherein the plenum chamber of each apparatus houses a coupling adapted to provide for a water tight coupling between the apparatus and the base providing for the plenum chamber to be * :* isolated from water in which the installation is immersed which providing for *.**.* the apparatus to rotate about the second axis of the apparatus. : ****.. * S..

21 An installation as claimed in any of preceding claims 17 to 20 wherein the * **.

plenum chamber houses conducting means whereby electrical power from the ** * generator is fed from the generator to an output station from the apparatus.

22 An installation as claimed in Claim 21 wherein the base incorporates means for linking at least two of the output stations to a transmission system whereby electrical power generated by the apparatus can be conducted from the installation to a location remote from the installation.

23 An installation comprising a two or more bases each base being common to one or more apparatus as claimed in Claims 17 to 22 each base being located by structural means in a bed of flowing water such as a river bed or a sea bed.

24 An installation as claimed in Claim 23 wherein the two or more bases are located as aforesaid by a structural means common to all the bases.

An installation as hereinbef ore described with reference to Figures 7 and 8 of the accompanying drawings.

26 A method of power generation comprising the steps of: providing a water tight housing for an electrical generator; and at least one rotor located outside the housing, the rotor being enabled to rotate relative tothehousingabouta5j; :...:.

linking the, or each, rotor to the generator so that on rotation of the * rotor the generator is caused to generate electrical power; S.....

mounting the housing and rotor on a base by means of a shroud so as to:...:.

enable the housing to pivot about a second axis; S...

immersing the housing, shroud and rotor in water subject to flow relative:::: to the housing, shroud and rotor, the water flow being in a direction, and at a speed, either or both of which can vary with respect to time; providing for the housing and the rotor, to pivot as a combination about the second axis so that interaction between the water flow and the rotor is optiniised for power generation by the generator; and withdrawing electrical power from the generator.

27 A method as claimed in Claim 26 wherein the first axis is horizontal.

28 A method as claimed in Claim 26 or 27 wherein the second axis is vertical.

29 A method as claimed in any of preceding claims 26-28 wherein the, or at least one, rotor is offset from the second axis.

A method as claimed in any of preceding daims 26 to 29 including the further step of providing vane means for the housing on the opposite of the second axis to the rotor or rotors such that following the step of locating the housing and rotor in water subject to flow the vane means when acted on by the flow serves to turn the housing to cause the first axis to be aligned, and in a stable configuration, with the direction of the water flow.

31 A method as claimed in Claim 30 wherein with the first axis when aligned with the direction of water flow results in the rotor being positioned up-stream of the housing. S... * SS

32 A method as daimed in Claim 30 wherein with the first axis when aligned with.

*5*SSS the direction of water flow results in the rotor being positioned down-streairi of:...:.

the housing. S... * I... * SS

33 A method of power generation as hereinbefore described with reference to and as illustrated in any of Figures 1 to 8.

Amendments to the claims have been filed as follows

CLAS

1 Apparatus for power generation comprising: a watertight housing; an electrical generator located in the housing; at least one rotor located outside the housing; means linking the, or each, rotor to the generator so that the, or each, rotor can rotate about a first axis to drive the generator; a shroud extending between a first section attached to the housing, and a second section remote from the housing, the shroud serving to at least partially endose a plenum; the shroud incorporating first means whereby the apparatus can be mounted on a base and be rotatable relative to the base about a second axis, and second means base whereby the plenum chamber can be isolated from * water in which the installation is immersed; and I.....

* a reservoir for pressurised inert gas located in the housing with controlled outlets to the housing and the plenum whereby pressurised inert gas can be * released in a controlled manner into the interior of the housing and the plenum to maintain them at a pressure above the ambient pressure in the vidnity of the housing.

2 Apparatus for power generation as claimed in Claim 1 wherein the means linking the, or each, rotor to the generator comprises a shaft extending through a water tight seal into the housing.

3 Apparatus as claimed in any preceding claim wherein the first axis is horizontal.

4 Apparatus as claimed in any preceding claim wherein the second axis is vertical.

Apparatus as daimed in any preceding daim wherein the, or at least one, rotor is offset from the second axis.

6 Apparatus as claimed in any preceding claim including vane means for the housing on the opposite side of the second axis to the rotor or rotors such that with the apparatus immersed in water subject to flow the vane means when acted on by the flow serves to turn the housing to cause the first axis to be aligned with the direction of the water flow in a stable configuration. p. p.

7 Apparatus as claimed in Claim A wherein with the first axis aligned by the vane * *.* means with the direction of water flow the rotor is positioned in the flow up- * stream of the housing. I.... * *

8 Apparatus as claimed in Claim 6 wherein with the first axis aligned by the vane * ** means with the direction of water flow the rotor is positioned in the flow down-stream of the housing.

9 Apparatus as claimed in any preceding claim including a fin attached to the housing, to the shroud or to both housing and shroud providing a stabilising effect to limit angular oscillation of the apparatus about the first axis when located in a water flow.

Apparatus as claimed in any preceding daim wherein the, or at least one, rotor is of variable pitch 11 Apparatus as hereinbefore described with reference to Figure 1 to 6 of the accompanying drawings.

12 An installation for power generation induding an apparatus as claimed in any preceding claim and a base unit on which the apparatus is mounted so as to be rotatable about the second axis of the apparatus.

13 An installation as daimed in Claim 12 wherein the base defines a station for the apparatus adapted to receive the second section of the shroud of the apparatus so as to define a plenum chamber through which the second axis of the apparatus extends.

14 An installation as claimed in Claim 12 in which the second section of the plenum chamber includes coupling means for providing a link between the apparatus and the base whereby the plenum chamber can be isolated from p.....

* water in which the installation is immersed; the coupling means further p.....

* providing for the apparatus to rotate relative to the base about the second axis of the apparatus.

An installation as claimed in any of preceding claims 12 to 14 wherein the plenum chamber houses conducting means whereby electrical power from the generator is fed from the generator to an output station from the apparatus.

16 An installation as daimed in any of preceding daims 12 to 15 wherein the base incorporates means for linking the output station to a transmission system whereby electrical power can be conducted from the installation to a location remote from the installation.

17 An installation comprising at least two apparatus each according to any of preceding daiins 12 to 16.

18 An installation as claimed in Claim 17 having a base common to all said apparatus.

19 An installation as claimed in Claim 17 wherein the common base defines a station for each apparatus and each station is adapted to receive the second section of the shroud of the apparatus so as to define a plenum chamber for each apparatus through which the second axis of the apparatus extends.

An installation as claimed in Claim 19 wherein the plenum chamber of each apparatus houses a coupling adapted to provide for a water tight coupling :: . between the apparatus and the base providing for the plenum chamber to be isolated from water in which the installation is immersed which providing for the apparatus to rotate about the second axis of the apparatus. . ..

21 An installation as claimed in any of preceding claims 17 to 20 wherein the * plenum chamber houses conducting means whereby electrical power from the generator is fed from the generator to an output station from the apparatus.

22 An installation as claimed in Claim 21 wherein the base incorporates means for linking at least two of the output stations to a transmission system whereby electrical power generated by the apparatus can be conducted from the installation to a location remote from the installation.

23 An installation comprising a two or more bases each base being common to one or more apparatus as claimed in Claims 17 to 22 each base being located by structural means in a bed of flowing water such as a river bed or a sea bed. 3)

24 An installation as claimed in Claim 23 wherein the two or more bases are located as aforesaid by a structural means common to all the bases.

An installation as hereinbefore described with reference to Figures 7 and 8 of the accompanying drawings.

26 A method of power generation comprising the steps of: providing a water tight housing for an electrical generator; and at least one rotor located outside the housing, the rotor being enabled to rotate relative s to the housing about a first axis; linking the, or each, rotor to the generator so that on rotation of the rotor the generator is caused to generate electrical power; ** .* * : mounting the housing and rotor on a base by means of a shroud so as to S....

S enable the housing to pivot about a second axis; * pressuring the interior of the housing by means of an inert gas to * S maintain the interior of the housing at a pressure greater than that of fluid pressure surrounding the housing; immersing the housing, shroud and rotor in water subject to flow relative to the housing, shroud and rotor, the water flow being in a direction, and at a speed, either or both of which can vary with respect to time; providing for the housing and the rotor, to pivot as a combination about the second axis so that interaction between the water flow and the rotor is optimised for power generation by the generator; and withdrawing electrical power from the generator.

27 A method as daimed in Claim 26 wherein the first axis is horizontal.

28 A method as daimed in Claim 26 or 27 wherein the second axis is vertical.

29 A method as claimed in any of preceding claims 26-28 wherein the, or at least one, rotor is offset from the second axis.

A method as claimed in any of preceding claims 26 to 29 induding the further step of providing vane means for the housing on the opposite of the second axis to the rotor or rotors such that following the step of locating the housing and rotor in water subject to flow the vane means when acted on by the flow serves to turn the housing to cause the first axis to be aligned, and in a stable configuration, with the direction of the water flow. ***.

S

31 A method as claimed in Claim 30 wherein with the first axis when aligned with *5**e the direction of water flow results in the rotor being positioned up-stream of the ::::; housing.

* 32 A method as claimed in Claim 30 wherein with the first axis when aligned with the direction of water flow results in the rotor being positioned down-stream of the housing.

33 A method of power generation as hereinbefore described with reference to and as illustrated in any of Figures Ito 8.