UNDERWATER POWER PLANT AND METHOD OF USING SEA CURRENTS

The present invention relates to a power plant of the type stated in the introductory part of appended claim 1 , and a method for generating power such as stated in the introductory part of the appended claim 11.

Lately, new methods for generating energy from the natural energy reservoirs have been sought. One of those reservoirs are the large ocean masses that contain considerable amounts of kinetic energy. The most common types of power plant are so-called wave-power plants, that are essentially adapted to concentrate and collect energy in the form of surface waves generated by wind. Another known type are the so-called current or tidal power plants, which are in effect turbines (similar to wind mills) arranged underwater, which means that they are attached to the bottom so that the turbines are driven by water currents generated by tides or other effects.

The present invention concerns a power plant related in type to the last mentioned current-driven power plants, but which constitutes an alternative solution and utilizes energy with a basis in other types of natural forces.

Hence, in accordance with a first aspect of the present invention, there is provided a power plant that comprises at least one turbine and a generator attached thereto, and where the turbine is adapted to be driven by a water current in an ocean. The power plant of the present invention is characterized in that it is arranged afloat underwater and further comprises a) equipment for detecting a convection current, . b) equipment for effecting movement to a location at said convection current, and c) an energy storage facility for storing generated energy.

The turbine is preferably adapted substantially for utilizing vertical currents, or currents having a substantial vertical component, the turbine axis being arranged substantially vertically.

Preferably, the turbine is adapted for utilizing substantially vertical currents driven by at least one parameter among the parameters density differentials, temperature differentials, salinity differentials.

In a preferred embodiment, the power plant comprises buoyancy equipment in the form of buoys for regulating the floating level for the power plant.

The equipment for detecting a convection current may comprise a sonar system, and the equipment for effecting movement may comprise a propeller system.

The power plant of the present invention comprises equipment for maintaining a floating depth, in the form of an adjustable buoyancy system.

The energy storage facility may be constituted by a system for generating free hydrogen, as well as a storage tank at the sea surface for storing hydrogen gas.

Further, the turbine may have a funnel-shaped concentration means attached thereto, for focusing the current toward the turbine cross section.

In a second aspect of the present invention, there is provided method for providing utilization power from a water current in an ocean, by means of a turbine and a generator, and the method is characterized in that

- a power plant comprising the turbine and generator, is arranged afloat underwater in said ocean, - a convention current is detected by means of detection equipment on or attached to the power plant,

- the power plant is moved to a position at the convection current,

- the turbine is driven by the convection current so as to make the generator generate electrical energy, and - the energy is stored in an energy storage facility in or at the power plant.

In what follows, the invention shall be illuminated further by considering embodiments thereof, and it is then referred to the appended drawings, of which

fig. 1 shows schematically how convection currents are able to move in a mass of water,

fig. 2 shows schematically how a power plant in accordance with the invention may be constructed, and

fig. 3 shows a special embodiment of important elements constituting part of a power plant in accordance with the invention.

In water masses, whether they are small or large, there will exist gradients of various physical parameters. Such gradients may be temperature gradients, density differentials and variations in salinity, over larger or smaller distances. Such differences or gradients will cause currents or flows attempting to equalize the differences.

In fig. 1 appears a simple and schematic presentation of how a series of convection currents may arise in a mass of water, driven by a temperature difference between the upper and lower layers of water. Heating from below and cooling at the top will start a multitude of circulating flows, with an upward current typically in an area like a, and with a downward current in areas like b.

If one imagines large masses of water with a typical depth dimension from 50 to 1000 meters, the picture of currents will of course be more complicated, due inter alia to currents generated by other and more important effects (like solar influx, earth rotation, coastlines etc.), however such currents are usually horizontal. In areas not dominated by global or regional currents, more local convection currents of the general type illustrated in fig. 1 , will arise.

Density differences, based on temperature, will cause such currents, since denser water, particularly at 4 ⁰ C, will have a tendency to sink, while water of lesser density will rise, and hence currents similar to what is shown in fig. 1 , may arise.

The density does not depend on temperature only, but for instance also on salinity. Salinity may vary, and this may generate currents in a similar manner.

One further factor is the bottom conditions, which means, particularly, locations where the sea bottom exhibits a prominent climb, for instance at underwater rock formations. It will be possible to find currents of substantially vertical type in such locations also.

Quite simply, the present invention amounts to moving a power plant over to such a current area as indicated at a or b in fig. 1 , and utilizing the current to drive a turbine system. We are then talking about currents of a substantial size, at sea depths in a range mentioned previously, 50-1000 meters or more. When the current is weakened or finds another position, the power plant will move to the closest usable position and continue its operation there.

In fig. 2 appears, in a quite schematical and sketch-like form, elements necessary in a power plant according to the invention, as well as some elements that can be chosen additionally. In an ocean or mass of water 1 , a substantially downward directed water current is shown by reference numeral 2. A power plant 3 in accordance with an embodiment of the invention, is arranged in such a manner that the current 2 or a part thereof, passes through the plant, driving a turbine 4 with a vertically arranged axis. The turbine 4 drives a generator 5 which, in the embodiment shown, is arranged somewhat outside the current 2. Electrical energy from generator 5 is transferred to an energy storage facility 8 that might be for instance accumulator batteries or a flywheel storage facility, but is shown here as an electrolysis installation 8a for dissociating hydrogen gas that is to be stored thereafter in a surface-located storage tank 8b.

The power plant must be kept at a certain floating depth, more particularly in a position where the current 2 of interest is concentrated, and for this purpose, buoyant bodies 10 in the form of buoys, are used. Since one must consider the reaction force that must be provided in an upward direction to prevent the downward current 2 from "dragging along" the power plant, it is quite necessary to have an adjustment system for uplift, and reference numerals 11 indicate devices for such adjustment of buoyancy. Thus, ballasting and de-ballasting of the buoys 10 take place by making the devices 11 , which comprise pumps and pressure

tanks for air or some other safe gas, provide for a variable volume ratio between gas and seawater in the buoys 10. These operations are controlled from a control center 12, on the basis of incoming measurement data regarding present depth, depth change per time unit, possibly measured force influence from the current 2 itself. Depth and depth change can be measured by means of sonar devices (not shown in the drawing).

If the current 2 decreases to below a critical value, either because the very power plant 3 has drawn so much energy therefrom that it is weakened, or because the current is diminished from other reasons, then it would be of interest to move the power plant 3 horizontally (and possibly vertically) to a new position where another flow can be utilized, then preferably within a reasonable distance from the first position. A scanning equipment 6 in the form of a special sonar (for instance of Doppler-type) may be used to find interesting movements in a substantially vertical direction. Then, the control center 12 will command translation of the power plant 3 in a horizontal direction, by means of e.g. a propeller system 7. The translation is effected slowly and steadily, and when the turbine 4 of the power plant 3 enters the new current 2, then a rapid ballasting/de-ballasting is made by means of devices 11 in order to compensate for the influences from the new current 2, in opposite directions depending on whether the current is rising or descending.

During the translation, a possible storage tank 8b is towed along, which means that a transfer cable between the hydrolysis installation 8a and the storage unit 8b must have the necessary strength to withstand the traction force.

As previously mentioned, the construction appearing in fig. 2 is quite schematic. In reality, a compact construction will be designed. For instance, it will be possible to arrange an electrical generator axially relative to the turbine, and propeller devices, control unit and sensors/gauges can of course be arranged in a more "integrated" manner than what appears from the drawing.

In fig. 3 appears a somewhat special embodiment of a power plant in accordance with the invention, in which embodiment a funnel-like pickup device or concentration device 9 is arranged above the turbine (in the drawing named a

"Kaplan-turbine"), in order to guide a downward directed current better toward the turbine situated at the lowest level. Orifices are arranged at the bottom of the funnel 9, for discharge of the water.

In this figure, it is also indicated that it is a density difference (cp. "water at +4°C") that is the prime mover behind the current. It is also indicated that the current will take on a rotary movement, possibly with a contribution to such movement from the so-called Coriolis effect. For the rest, this power plant is shown to comprise buoyancy tanks and a generator, but other necessary elements (cp. Fig. 2) have been left out.

Having a current-guiding/pickup device 9 arranged like in fig. 3, will result in a power plant that is only suitable for operation with a downward directed current. But with a suitable mechanical arrangement, it will be possible to "reverse" the funnel 9 into a downward shape, or it may be possible to tilt the whole system containing funnel 9, turbine 4 and generator 5, a 180° angle about a horizontal axis so that it may work in an upward directed current.

Furthermore, the inventor sees a possibility for exploiting also an additional energy that is conveyed to a current from the earth rotation, i.e. via the Coriolis effect. This effect will be best discernible for a horizontally running part of the convection current. The power plant 3 must then be movable upward or downward to a horizontal part of the current, and the turbine must be tiltable to horizontal operation.