The present invention relates to apparatus and methods for the generation of electrical power from renewal sources, particularly but not limited to green energy technologies harnessing power from natural hydropower sources such as the sea or ocean currents and tides into electricity or other useful forms of power

Currently, green technologies are still deemed to be incapable of sustained and reliable power supply owing to their tendency to operate in a broadly cyclical manner over time - for example, the behaviour of wave and tidal currents depend on lunar orbital activity. Furthermore, it may be difficult predict if and when the natural power source is capable of generating a usable output, if at all - e.g. the sufficiency and strength of wind, sunlight tidal currents, and the like. Practically, therefore, a backup generator system based on traditional methods (e.g. fossil fuel) is typically required to cover times when power from natural sources is unavailable or insufficient

It is known that deep sea ocean currents are an exception in that they are less susceptible to short-term change and operate in a more consistent way than e.g. tidal currents and or waves. An sub-sea ocean current like the Gulf Stream is a continuously directed movement of ocean water driven in the main by density and temperature gradients, which can provide a relatively consistent base load of energy or power. This never-ceasing movement and energy is therefore suited to regular and sustained energy production, and is more often reliable than the other seasonal and cyclical green energy sources mentioned above.

It is known to use turbine or generator apparatus for this purpose. In such methods, the flow of water is used to harness hydropower sources to generate electrical power. In use, the operational and sensitive parts of the apparatus such as turbine blades, gear mechanisms, valves, rotating gimbels and the like are exposed to the corrosive nature of salt water and the accumulation of debris and marine life on their working surfaces. In consequence, they require a lot of maintenance to keep such surfaces free from obstruction and damage which hampers the efficient working of the apparatus. This problem is exacerbated in the context of deep sea oceans, where such apparatus rest on ocean floors to a typical depth of 600 to 1 ,000 feet below the surface level. The difficulty of performing maintenance work on such apparatus is augmented by the sheer size and scale of the equipment, which may reach 400m across and 200m high. Apparatus of this size requires use of a number if inlet tubes in to which sea water is funnelled, and each tube may have more than one set of sea water chambers. A structure this size will be extremely difficult to build on land in its entirety. For example, the roof of the structure has a massive span and is enormously heavy on dry land; when deployed underwater however, its weight is supported by the water and, and in a preferred embodiment is built to have neutral, or even positive buoyancy during use. Similarly, the apparatus chambers and other structures apart from the heavy concrete and steel foundation and side walls can be built to be neutrally or positively buoyant. As may be imagined, a structure of this size, weight and mass would make it extremely difficult and expensive to raise the apparatus to the surface for cleaning. Cleaning and maintenance carried out below the surface presents yet another set of difficulties. The scale of the task involved in cleaning the surfaces of is self-evident, although the need for such routine maintenance is equally obvious in view of the harsh environment within which the apparatus works.

An approach to this problem is described in US 4335319, wherein the operative components of the generator are located within a housing on a platform so that only the turbine is submerged within the corrosive water. US 5440176 addresses this by locating its control plant on land.

These prior art approaches still suffer from operational problems because they employ turbine blade surfaces which are "hydro-dynamically critical", by which is meant that the shape of the blade must be of a certain form and curvature and smooth for it to work. The presence of marine growth (e.g. barnacles) on the surface of blades and other hydro-dynamically critical components will create turbulence during operation and cause the apparatus to operate inefficiently and eventually fail completely. Furthermore, the turbine seals are exposed to sea water and pressure which are major weak points, which if and when they fail, which could result in catastrophic failure of the apparatus.

It would be desirable to eliminate or to reduce the level of maintenance required following from the operation of deep sea ocean current power generators in their natural environments.

According to a first aspect of the present invention there is provided apparatus for generating power, comprising a first, open, unit arranged to permit a first fluid to flow through it, and a second, closed, unit which in use is substantially filled with a second fluid, arranged so that in use the flow of the first fluid through the first unit drives the flow of the second fluid within the second unit, the apparatus further including a turbine arranged in use to be driven by the flow of the second fluid within the second unit.

The apparatus comprises a head- or front-end driving element or unit which is arranged specifically for use in the harsh environment of the deep sea bed. It comprises two main sections, the first of which is an open unit or section which, in the specific embodiment discussed below, receives as a first fluid, sea water driven into the apparatus by ocean currents. The force of the current causes a flow of sea water through the first, open, section. This flow of the sea water in turn causes a flow of a second fluid contained in a second, closed unit or section of apparatus, which then turns a turbine.

Thus it is possible for the simple effect of the sea water flowing into and out of the first unit, to be harnessed to cause a flow in the second, closed unit, which in turn then drives a turbine for generating power.

In preferred embodiments, the flow effect is optimised flow by causing the sea water flow initiated by the sea current to be directed into receptacles within which are disposed flexible barriers in the preferred embodiment of elastomeric balloons. The receptacle contains both sea water and the second, clean fluid, and are separated by the wall of the balloon. By deploying two or more such receptacles, it is possible to alternate, or to stagger, the flow of sea water in and out of each receptacle. The flow is directed by a fluid direction mechanism which in a preferred embodiment comprises a multi-flow valve, which include channels connecting the receptacles to the inflow and outflow ports which lead to and from the apparatus. In an exemplary implementation, the channels are blocked and unblocked so as to control sea water flow to and from the elastomeric balloons which inflate and deflate in an alternating fashion.

Varying the amount of sea water in the receptacle on one side of the flexible barrier causes the volume of second, clean fluid in the same receptacle to also vary, as the receptacle is of an unvarying size and volume. Because the second fluid is of a fixed quantity and contained (but not entirely filling) in a closed environment, first fluid/sea water volume changes within the receptacles have the effect of forcing or driving second fluid movement i.e. a flow within and through the second, closed unit. This flow is then used to turn a turbine, which may in turn push second, clean fluid to any number of further turbines eventually linked to a power generator or electric device or apparatus.

According to a second aspect of the present invention there is provided apparatus of any preceding claim and an electrical generator.

According to a second aspect of the present invention there is provided a method for generating power, comprising - providing a first, open, unit, positioned to allow an ocean current to force a flow of a first fluid to flow through it, providing a second, closed, unit substantially filled with a second fluid, causing the second fluid to flow within the second unit by being driven by the flow of the first fluid through the first unit, and - using the second fluid flow within the second unit to drive a turbine.

Preferred embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figures 1 and 2 are respectively schematic views of first and second operational positions of apparatus for generating hydroelectric power; and Figures 3 and 4 are respectively schematic views showing details of the operation of a valve in use with cylinders of the apparatus for generating hydroelectric power, in first and second operational positions. Figure 1 shows apparatus (2) for use in the harnessing of sub-sea currents to generate hydroelectric power. In particular, it forms a "front end", or a feeder or driving portion of a hydroelectric generator system which includes a surface turbine (67) which may be any conventional type or design suitable for being driven by hydropower. As shown in the drawing, this surface turbine may be located above the sea surface (66), although the skilled person would appreciate that this may be positioned anywhere which allows its operation to generate electricity from the energy and force of water. However, as noted above, the surface turbine is a relatively delicate piece of equipment having sensitive parts such as its blades and the generator, it is best kept away from the damaging and corrosive effect of seawater. Preferably, it should be placed at an underwater depth of less than 150m. Sensitive components that require precision engineering are at high risk of gross deterioration when exposed to salt water corrosion or marine growth and could result in premature malfunction. The presence of sea life (such as sharks) within the apparatus, as well as of marine growth on component surfaces, further interfere with its operation.

The driving apparatus (2) provides the power for driving the surface turbine (67), which is sourced from the energy of the constant deep ocean currents. The driving apparatus is thus substantially or completely located under the water surface. As will be elaborated below, the power of such currents drives a sub-surface turbine arrangement (62, 63), which in turn drives the surface turbine (67) in a preferred implementation. By imposing a layer between the electricity-generating portion and the sea water, and by driving the primary turbine indirectly with the energy of the ocean currents in this way, the surface turbine is protected from the harmful results of being in direct contact with the water of the sea, its inhabitants and so on.

Structurally, the apparatus (2) comprises two main parts, which for convenience shall here be referred to a sea water part, and a hydraulic fluid part. Sea water enters the apparatus in a flow originating from the ocean current (4). Energy from the sea water section in turn drives the hydraulic fluid portion of the apparatus, which drives the surface turbine connected thereto. A housing (6) houses ail (sea water and hydraulic fluid) parts of the driving apparatus (2), and is arranged to be operatively coupled to a surface turbine (67), to which a generator (90) may in turn be connected. The housing base forms a foundation (52) for location on a sea bed (51), which may be at any depth. For example, it is possible to place the apparatus on the deep ocean floor, but preferably the apparatus is placed on a continental shelf (which represents a plateau shelf section of the seabed floor which rises from the deep sea floor in areas adjacent to land masses, of typically 200m depth). Deep ocean currents (at depths of 1 ,000m or more) are powerful but move at very slow rates, typically at rates of about 1 km per hour. When a deep ocean current flows towards and over a continental shelf, the velocity and flow rate of the up-drifting current increases as it moves over the continental shelf. Faster current flow rate is preferred for their greater energy potential which may be harnessed for the generation of hydroelectricity by the system of the invention.

The parts making up the driving apparatus will now be described.

The sea water section

This part of the apparatus is so termed as it is occupied by sea water which flow is driven by the energy and force of the current (4). It comprises an open system in that the current pushes water into and through it.

A channel (53) is provided along the width the driving apparatus, terminating at each end in an opening which is wider than the channel. Ocean currents typically flow in one main direction, so the position of the generating apparatus may be fixed on the sea bed. The generating apparatus is positioned on the sea bed so that one of its openings (53) preferably directly faces an oncoming current (4). In one embodiment, the opening could measure about 200m high and 350m wide, to funnel ocean water into the apparatus via the narrower channel (84) measuring e.g. 70m high and 70m wide. In use, the reduction in cross sectional area from the opening to the channel increases the velocity of water flow through the channel.

Part way along within the channel there is provided a scoop-shaped component (82). This can be any shape to facilitate the diversion of a part of the water flowing into the channel (arrow 54) into an inflow pipe or port (55a). The water which is not diverted continues its flow path through the flow through channel (82) to exit the apparatus at the far end. In the embodiment shown in Figure 1 , the scoop is a structure extending downwardly from the upper inner surface of the channel having two concave walls facing away from each other. The concave walls help define in part the shape of the inflow port (55a) and an outflow port (55d) on opposite sides of scoop structure.

It would be appreciated that the inflow port can function as an outflow port, and the outflow port as an inflow port in dependence on the direction of ocean current. In such an implementation, the operation of the apparatus is the same, save the direction of fluid flows (discussed below) will operate in the opposite direction.

The inflow and outflow pipes or ports lead to a chamber (40) comprising a multi-flow valve (56), which is configured to selectively direct sea water within the chamber to and from one of the two cylinders (57, 69) via the pipes (55b, 55c) connecting the valve chamber to the cylinders.

One example of a suitable multi-flow valve is depicted schematically in Figures 3 and 4, and its structure will be described more fully below in connection with those figures. Essentially, the multi-flow valve (56) (shown within dotted lines in Figures 3 and 4) comprises a number of channels (41, 42, 43, 44) leading between the cylinders (57, 69). The channels are arranged so that some of them are selectively blocked off while others are left open, causing sea water to flow between the cylinders and the flow-through channel (53), in a manner discussed further below. The blocking mechanism can comprise industry standard valves, although in a preferred implementation they comprise elastomeric membranes or diaphragms acting as balloons (45, 46, 47, 48) within the channels. In preferred implementations, the channel balloons are filled with a "clean" fluid (i.e. not being sea water or the like affecting the operation of the system as discussed elsewhere), such as a distilled water-lubricant mix. They are arranged to selectively inflate and deflate as described further below, so that the channel which they occupy is blocked or choked off, stopping sea water from flowing through the blocked channel.

The first cylinder (57) within which is disposed a flexible, preferably elastomeric, diaphragm or membrane acting as a balloon (59). The balloon is secured at its neck at the entrance of the port (55b) into the cylinder. In use, the membrane walls flex and deform constantly, so that marine growth on its surface is discouraged or at any rate reduce. Any deposit or growth that does manage to settle on the balloon surfaces is likely to calcify and fall off and eventually be ejected from the cylinder. In one preferable embodiment, the membrane is made from a non-porous material such as a heavy woven aramid impregnated in a plastic/polymer. The membrane comprises an almost-wholly closed structure (akin to an inflatable balloon) save for the communicating port (55b) which leads into the interior of the closed membrane from the interior of the valve chamber (40).

A second cylinder (69) is similarly provided internally with a flexible membranous closed balloon (70) within it. The second cylinder does not communicate with the first cylinder (57) nor the first membrane (59); instead, the interior of the second membrane balloon (70) is connected via a pipe or port (55c) only with the multi-flow valve chamber (40). An outflow port (55d) is provided to allow sea water in the valve chamber (40) to flow back into the channel (84) in the direction of arrow (54) and eventually out of the apparatus entirely, and into the sea.

This sea water part of the driving apparatus is configured so that it has no sensitive mechanical moving parts that are exposed to sea water. In particular, the elastomeric balloons are not sensitive to sea water due to the material used and its not having any parts which move relative to each other. The multi-flow valve, as noted above, comprises tubes within which are disposed flexible balloons to obtain the selectively blocking effect in a preferred embodiment. Thus the multi-flow valve is also relatively resistant to the damaging effects of the seas water.

The hydraulic fluid section

This portion of the driving apparatus is a closed system containing a hydraulic fluid, which may be of any type but which has the essential characteristics of being a lubricating fluid, preferably additionally functioning as an anti-freeze and cleaning agent. One exemplary fluid comprises a distilled water-based glycol with lubricating silicone; it may also have properties similar to those of synthetic brake fluid. Importantly, this part of the apparatus (shown as shaded in Figures 1 and 2) comprises a closed system, and is substantially or completely isolated from the sea water of the previously-described sea water section of the apparatus. As being a closed system, the amount of hydraulic fluid provided in this part of the driving apparatus is fixed and quantified at the build stage and provisioned so that it almost fills or occupies the hydraulic fluid receptacle component parts in the manner described below.

As described above, the two cylinders (57, 69) are occupied by inflatable membrane balloons (59 and 70) which interiors communicate with the valve chamber (40) via ports (55b and 55c), on the sea water side. On the other side of the barrier presented by the balloon walls, the cylinders are occupied with hydraulic fluid i.e. surrounding the exterior surface of the elastomeric balloons, within the cylinders.

The cylinders on the hydraulic fluid side communicate via four one-way valve ports (60, 76, 75, 61) with a turbine arrangement, which comprises a first, larger, turbine (62) and a second, smaller, turbine (63). The first turbine (62) is configured as a high volume turbine which turns relatively slowly. It is connected via gears to the second, higher speed pressure turbine (63) which turns at greater speed than the first turbine.

An up-pipe (64) is connected to the second turbine through which is drawn a flow of hydraulic fluid upwards to the surface where the surface turbine (67) is located above sea level (66), which in turn is connectable to an electric generator (not shown). The turbine is part of the closed hydraulic fluid system, unlike the electrical generator (90) it drives.

The operation of the apparatus to obtain this effect will now be described.

Operation of the feeder apparatus

During initial installation, the driving apparatus (2) is fully submerged and settled on the sea bed. It is provided so that one cylinder is set in the fully deflated position and the other is in the fully-inflated position. At this stage, sea water will flow into the apparatus via the channel and ports (84, 55a, 55d), so eventually all the sea water section of the apparatus (i.e. including the channel 84, ports 55a, 55b, 55c and 55d, and the multi-valve chamber 40) are filled with sea water (inasfar as is possible to displace any air within these components) and to a lesser extent, the first and second balloons (57 and 69).

Operation commences when current movement (4) begins to drive a sea water flow into the apparatus channel (84), most of which, as described above, enters the inflow port (55a). The flow speed of the sea water from the channel (84) further increases by the scoop (83) as it is diverted into the multi-flow valve chamber (40) by the concave wall of the scoop (83). The higher velocity advantageously increases the speed and energy levels of the in-flowing sea water within the driving apparatus. As being open to the sea via port (55a), the chamber (40) is always substantially full of water.

Figures 3 and 4 show the operation of the multi-flow valve (56, shown within the dotted line) in conjunction with the cylinders (57, 69), which is at the heart of the operation of the driving apparatus. The parts denoting the presence of hydraulic fluid are shaded, while those parts containing sea water section of the apparatus are left un-shaded. Those parts into which sea water may flow comprises the two cylinder balloons (59, 70), as well as the channels (41 , 42, 43, 44) within the multi-flow valve.

The channels are configured so that each cylinder balloon is connected to the inflow and the outflow ports; specifically cylinder balloon (59) is respectively connected to the inflow and outflow ports via channels (41) and (43), while the second cylinder balloon (70) is connected to the inflow and outflow ports via channels (42) and (44) respectively. Disposed within the channels are channel balloons - (45) in channel (41), (46) in channel (42), (47) in channel (43), and (48) in channel (44). In the embodiment shown in the drawings, the channel balloons are disposed in pairs which are open to each other, with a fixed quantity of fluid (preferably the "clean" fluid discussed above) which enables only one of the pair to become fully inflated and thus block the channel it occupies, while the other remains substantially un-inflated within the channel, allowing for sea water within its channel to flow in a substantially unhindered manner. The amount of fluid in each pair of channel balloons is controlled by a pump (56b, 56f) which is disposed in between them. The pumps (56b, 56f) can be powered the turbine arrangement (62 and/or 63).

The pump is also operatively connected to sensors (59a, 70a). (The connection between the pump and the sensors are not shown in the drawings, but can comprise a wire or cable leading between the components.) The function of these sensors is to sense when a cylinder balloon has inflated to its maximum capacity, are positioned within the cylinders in a location remote from the mouth of the cylinder i.e. where the cylinder balloons are fixed to the cylinders. In the embodiment shown in Figure 3 for example, the sensors are depicted to be located opposite to the cylinder mouth. The sensor can comprise a simple electronically- or mechanically-activated device, e.g. a pneumatic touch- or push-button sensor. Upon full inflation, the cylinder balloon touches or impinges upon the sensor. This indication that one of the cylinder balloons is fully inflated within its cylinder is communicated (not shown) to the relevant pump (56b or 56f) which diverts fluid to a relevant one of the channel balloons in the manner described further below, to block the relevant channel to prevent sea water from continuing to flow to the now fully-inflated cylinder balloon.

The skilled person would appreciate that there are a number of ways to implement the detection of full balloon inflation in a cylinder and subsequent communication of this to the pump(s). For example, use of a touch-sensitive sensor is just one possible method of implementation.

The arrows in Figures 3 and 4 represent the movement of sea water through the sea water section. In Figure 3, the channel balloons (47, 47) in the channels (42, 43) are inflated. With e.g. channel balloon (46) full, the other (45) in the pair is relatively deflated so that the path from the inflow port to the first cylinder balloon is relatively clear. Sea water flows in the direction shown by the arrows into the cylinder balloon, as the other channel (42) leading from the inflow port to the second cylinder balloon (70) is substantially (i.e. wholly or in the most part) blocked. At the same time, the channel balloon (47) substantially blocks off sea water flow from the first cylinder balloon to the outflow port, so that any sea water entering the cylinder balloon is retained therein. As a result, the cylinder balloon inflates.

At the same time, the second cylinder balloon (70) is starved of sea water supply through blockage of channel (42) by channel balloon (46), while the channel (44) to the outflow port is open in the absence of any blockage by channel balloon (48) so that sea water drains out of the apparatus in the direction shown by the arrows. The second cylinder balloon thus deflates. This process continues until the sensor (70a) in the other cylinder is activated in the next stage of the process.

Figure 4 depicts this next stage, wherein the other two channel balloons (45, 48) are inflated and blocking off sea water passage in channels (41 , 44). The result is that sea water flows along channels (43, 42) in the directions indicated by the arrows, so that the first cylinder balloon (59) is deflating while simultaneously the second cylinder balloon (70) is inflating. When the second cylinder balloon is fully inflated, the sensor (70a) in the cylinder is activated, causing the pumps to switch over to divert the fluid in the full channel balloon to its the substantially empty corresponding balloon in the pair, causing the sea water to again flow into and be retained within the other cylinder balloon in a continuous cycle.

The alternating inflation and deflation of the cylinder balloons described above is powered by the force of the current flow entering and/or exiting the driving apparatus. While it is possible for the cycle to be continued automatically for an indefinite period for while there is current force entering the apparatus, it is possible to include a

Thus the sea water is passed around within the sea water section of the apparatus, as the two sets of blocking balloons (45, 46) and (47, 48) making up the multi-flow valve, take turns blocking and unblocking the channels they occupy. This switching effect and water flow in the sea water part is caused in part by the closed, hydraulic fluid section of the apparatus, which contains a fixed amount of fluid and thus exerts a pulling and pushing force against the sea water section of the balloons within the two cylinders.

Because its walls are flexible and deformable, sea water occupying the second elastomeric balloon is also sucked out into the valve chamber via port (55c). This causes the balloon to collapse inwardly as its walls deform. The reduction in the sea water-side volume occupied by the balloon in its cylinder causes hydraulic fluid to flow and to turn a slow high volume turbine (62), which is connected to the cylinders on the hydraulic fluid side via four valve ports (60, 76, 75, 61). One-way valves are employed, so that a single direction flow is generated to turn the high volume turbine in one direction, regardless of whether the fluid flow is generated by the pushing or pulling force by either cylinder.

The pressure differences caused by the alternating inflation and deflation of the two balloons in the cylinders is thus used to turn the high volume turbine, which turns relatively slowly, and is geared to turn an optional smaller, high pressure turbine (63) at a greater speed. The second smaller turbine (63) pumps hydraulic fluid up to the surface turbine to drive it, which in turn drives any electric generator (90), or any electrically-driven device to which it is connected.

The movement and flow of the hydraulic fluid upwards from the combined in-ward force and out-ward force create vast amounts of power in the larger turbine (62) of the underwater turbine arrangement. In particular, the larger, high volume turbine

(62)

As noted previously, the surface turbine may be positioned underwater although it is more advantageously positioned above the water surface. In such an implementation, the up- and down-pipes that connect the underwater turbine arrangement to the surface turbine can be extended to the surface and the turbine placed on the surface e.g. on a platform, or it may be located on dry land e.g. on the sae shore.

Advantageously and in contrast with prior art systems, this invention has no pressure seals and no weak points for the seawater to infiltrate the more sensitive and delicate parts of the system viz. the turbine blades and so on. Instead, the parts comprising the working mechanism operates in the hydraulic fluid which is incompressible and lubricating. In preferred embodiments, cleansing agents may be included in the hydraulic fluid to further improve its use. By completely separating or isolating the sea water and the hydraulic fluid parts of the driving apparatus in this manner, all components that are sensitive to sea water corrosion and/or the presence of marine life within the apparatus or growing on component surfaces, are encapsulated in a clean, closed system. Maximum efficiency of the system may therefore be aimed for in operation. Even though it may be expected that the surface turbine is not driven at the full power of the ocean current being harnessed, nonetheless even the reduced hydropower levels obtained at the surface are considerable.

The skilled person would appreciate that a number of permutations, additions and substitution of components, parts and processes are possible within the scope of the invention. For example, the second, high speed high pressure turbine (63) could be connected directly to the electric generator (not shown), either via a drive shaft, or the electric generator could be co-located at a subsea location with the small high pressure turbine (63).

The components of the driving apparatus and system may take different forms and even repositioned relative to each other within the apparatus, or to other pieces of equipment making up a system including the driving apparatus. The following are some examples of alternative embodiments and implementations:

Piston method:

Instead of using a membrane balloons in the pressure chamber, a piston-like device could replace the membrane balloon's function.

The methods, devices and configurations described above and in the drawings are for ease of description only and not meant to restrict the invention to any particular embodiments. It will be apparent to the skilled person that various components, devices and permutations on the methods and devices described are possible within the scope of this invention as disclosed. Similarly the invention could be deployed in a variety of contexts to realise the advantages afforded by its use. For example, a front end driving apparatus or mechanism may be usefully deployed in connection with any turbine, generator, or other equipment which comprises sensitive and fragile parts susceptible to damage when operated in an environment hostile to it. For example, the apparatus may be used in the generation of tidal power, or wind power.

The skilled person would also appreciate that a number of variations may be made to the precise location and configuration and materials used for the components and parts making up the apparatus, that would be within the scope of the inventive concept.