This is a continuation of International Application Number PCT/GB00/00634 filed Feb. 23, 2000.
This invention relates to water turbines and more particularly to turbines arranged to be driven by the action of a flow of water.
In our British Patent Application No 9706464.6 and in our British Patent No 2256011 B we have disclosed constructions of water drivable turbines.
As has been previously mentioned flowing water is a characteristic of tidal, marine, esturial or river currents.
Bearing this in mind the present invention relates in particular to the use of turbines for to produce either electricity directly or to produce rotation of a shaft for utilisation for a required purpose.
A known turbine arrangement intended for extracting kinetic energy from water currents, whether in a river or at sea, generally includes a rotor capable of interacting with the flow of water in such a way that some of the energy motion of the passing mass of water produces forces on the blades of a rotor thereby producing rotation of the rotor. The rotation of the shaft is utilise to perform some useful function such as to generate electricity. Such a device is analogous in principle to the better known concept of a windmill or wind turbine which extracts kinetic energy from flowing air, except that due to the much greater density of water as compare with that of air, lower fluid flow velocities (by a factor of approximately 9) are needed to give the same power density (power per unit area of flow) so that water moving at Im/s has a similar power density (e. g., watts per square metre) as air moving at 7.5 metres/second.
It is also to be noted that although the basic principles involved in extracting kinetic energy from water currents are similar to those involved in the better known art of extracting kinetic energy from the wind, the actual forces involved and the practical engineering requirements for the formation of suitable installation are in most respects totally different. In practice, tidal, marine and river currents generally have their maximum velocity near to the surface so that any device intended efficiently to intercept the kinetic energy of the currents needs to have its rotor set so that its active plane or cross section is perpendicular to the direction of water flow and as near as possible to the surface. Any such device also needs to be securely positioned in such manner as to resist the considerable drag forces and reaction forces associated with any interaction with large masses of moving water. In practice, the main drag force is an axial thrust in the direction of current flow due to the momentum deficit in the flow, which thrust is proportional to the area of the active rotor and the velocity squared. There is also a significant torque reaction to be resisted when a load is applied to the turbine rotor drive shaft. Furthermore, means has to be provided to convert slow rotational rotor movement produced by the water flow into a useful energy form that can be effectively transmitted from the generation location to a location at which it can be gainfully employed.
Such transmission of energy can be in the form of electricity by way of a marine cable along the sea or river bed (or by way of overhead cables supported by pylons or poles if the installation is close to the shore or river bank) there is also the option to use the energy xe2x80x9con sitexe2x80x9d for the production of some portable product such as fresh water, ice, minerals extracted from the sea or hydrogen and oxygen produced by electrolysis or any other products that can be generated from energy and the local environment, any such products can be stored and collected by an appropriate vessel, or transmitted to shore by pipeline.
For a practical installation there are other important factors that need to be addressed. In the case of marine applications such factors include the need to resist damage from large waves during storms, the need to make the device visible to minimise it as a marine hazard to shipping and the need to be able to service and repair as well as to deploy the device at sea both safely and at a minimum cost.
It is an object of the present invention to provide a turbine system that takes into account factors or matters such as mentioned above.
Broadly, according to a first aspect of the invention there is provided a flowing water actuatable turbine system including a column/pile upstanding; from the sea or a river bed, a stored and collected by an appropriate vessel, or transmitted to shore by pipeline.
For a practical installation there are other important factors that need to be addressed. In the case of marine applications such factors include the need to resist damage from large waves during storms, the need to make the device visible to minimise it as a marine hazard to shipping and the need to be able to service and repair as well as to deploy the device at sea both safely and at a minimum cost.
It is an object of the present invention to provide a turbine system that takes into account factors or matters such as mentioned above.
According to an aspect of the invention there is provided a flowing water actuatable turbine system, wherein the turbine system is mounted for operational co-operation with water current by means of an upstanding column/pile in such manner as to be axially displaceable length ways of the column/pile Conveniently, in the flowing water actuatable turbine system the turbine system is arranged to be rotatable about the longitudinal axis of the column.
According to a further aspect of the invention there is provided a water flow current turbine, wherein in order to accommodate change of the direction of water flow with respect to the turbine assembly arrangements are provided for controlling the pitch of the blades in response to change in direction of water flow through the turbine rotor.
A further aspect of the invention provides a water flow turbine installation, including a column/pile upstanding from a river or the sea bed to project above the water level, for supporting a water current turbine, wherein the operational pitch of the blades of the rotor are selectively adjustable.
Preferably the operational setting of the pitch of the turbine blades of the associated rotor is selectively settable throughout a range of 180 degrees of rotation.
Conveniently the turbine is so mounted to the column to be bodily displaceable length ways of the column/pile.