Patent Application
20110298216
This invention relates to a method of securing a hydroelectric turbine at a deployment site, for example on the seabed and in an area of significant tidal flow, which method enables the turbine to be located securely without risk of overturning or sliding out of position, but without requiring the use of piling or other complex fixing operations, thus significantly simplifying the installation of such a turbine.
Currently, and at a global scale, there is great concern surrounding the damage that the emission of CO2 is causing to our environment, in particular the threat posed by global warming. One of the major sources of CO2 emission is in the production of electricity, on a large scale, through the burning of fossil fuels. Electricity is however a commodity that has become essential to the survival of the human race, and there are thus vast resources currently being expended in seeking alternative means of generating large quantities of electricity without the use of fossil fuel. While nuclear energy is one such alternative, most societies are uncomfortable with the negative aspects of nuclear power and thus other more desirable solutions are required.
Renewable energy has thus come to the fore in recent years, with many projects being developed around solar energy, wind energy, and tidal power. Of these alternative forms of energy, tidal power is arguably the most attractive, given that tidal flows are entirely predictable and constant, unlike wind or solar energy which are relatively intermittent and therefore less dependable.
However, harnessing tidal energy does provide its own challenges, in particular with respect to the installation and maintenance of tidal power generators, for example hydroelectric turbines, which by the very nature of the operation of same must be located in relatively fast flowing tidal currents, and more than likely located on the seabed. These conditions are significantly inhospitable, and are not conducive to safe working conditions. The installation of a base on which such tidal turbines are mounted has conventionally taken the form of the sinking of a pile into the seabed, on which pile a turbine or secondary frame carrying one or more turbines can then be located. However, the sinking of a pile into the seabed in an area of high tidal flow is considerably problematic and generally a dangerous operation. In addition, significant drilling and piling equipment must be transported to and operated at the site of installation, significantly increasing the complexity and cost of the operation.
The installation process is further complicated by an increasing shortage in the market of suitable vessels and equipment to perform such drilling work and the extreme danger of engaging divers in high tidal flow sites.
It is therefore an object of the present invention to provide a method of securing a hydroelectric turbine at a deployment site such as on the seabed and using readily available non-specialist marine equipment and without requiring complex and time consuming drilling or similar preparatory operations.
According to a first aspect of the present invention there is provided a method of securing a hydroelectric turbine at a deployment site, the method comprising the steps of:
Preferably, the method comprises the steps of
Preferably, the method comprises the step of:
Preferably, the method comprises the step of:
Preferably, the method comprises the step of:
Preferably, the method comprises the steps of:
Preferably, the method comprises the step of:
According to a second aspect of the present invention there is provided a hydroelectric turbine system comprising a turbine; a base on which the turbine is mountable, the base comprising a plurality of legs at least one of which is positioned to experience a down-force, when the system is deployed on the seabed at a high tidal flow deployment site, which down-force is generated from the force exerted on the turbine and/or the base by the tidal flow.
Preferably, the base comprises three legs arranged in a triangular orientation.
Preferably, each of the three legs has a seabed-contacting end which is shaped and dimensioned to assist in penetrating the seabed.
Preferably, the base comprises a frame which is triangular in shape, a leg extending from each apex of the frame.
Preferably, a seabed contacting end of the, or each, leg is pointed.
Preferably, a seabed contacting end of the, or each, leg comprises an array of fins.
Preferably, the plurality of fins are arranged in a circular array about a longitudinal axis of the respective leg.
Preferably, each fin tapers inwardly such that the fins converge at a common point.
As used herein, the term “seabed” is intended to mean the seabed in addition to the floor or bottom of any suitable body of water such as a riverbed or the like.
As used herein, the term “direction of tidal flow” is intended to mean the prevailing direction in which the tide flows, as there will be some deviation from the prevailing direction as the tide ebbs and flows.
Referring now to the accompanying drawings, there is illustrated a hydroelectric turbine system, generally indicated as 10, which is adapted to simplify the installation and maintenance of a hydroelectric turbine 12 forming part of the system 10 on to the seabed B as illustrated in
The frame 16 of the base 14, in the embodiment illustrated, is triangular in shape and is comprised of three struts 20 which together define three apexes 22, at or adjacent each of which one of the legs 18 extends downwardly. While the triangular shape of the frame 16 is preferred, it will be appreciated from the following description that the shape of the frame 16 may be considerably varied, and further the number of legs 18 provided may be varied.
Referring now in particular to
In the embodiment illustrated each contacting end 24 comprises a plurality of tapered fins 28, four fins 28 being provided to form each contacting end 24. It will of course be appreciated that the fins 28 could be significantly varied both in number and shape/orientation. The use of the fins 28 significantly reduces the cross-sectional area of the contacting end 24, thereby increasing the ability of the end 24 to grip, pierce or penetrate the seabed B. In addition, once the contacting ends 24 are sunk into the seabed B, the fins 28 will resist any turning moment on each leg 18, thereby improving the stability of the system 10.
Turning then to the operation of the invention, the system 10 is initially transported to a deployment site using any suitable vessel (not shown), for example a barge towed by a tug or the like. The system 10 is then lowered from said vessel (not shown) towards and onto the seabed B, with the turbine 12 secured to the base 14. On contacting the seabed B the pointed contacting ends 24 of the three legs 18 will, due to the weight of the turbine 12 and base 14 acting downwardly thereon, provide significant grip on the seabed B. In the absence of the significant tidal forces experienced at the deployment site, this grip would be sufficient to prevent unwanted movement or slippage of the system 10 along the seabed B. However, due to the significant tidal forces which are experienced at the deployment site the level of grip effected by the weight of the turbine 12 and base 14 may not be sufficient to prevent the above-mentioned unwanted movement of the system 10.
The system 10 is therefore designed to generate, from the tidal flow, a downwardly acting force through at least one of the legs 18 in order to generate increased grip by the base 14 on the seabed B. This is achieved primarily by selective positioning of the turbine 12 on the base 14 at a location between each of the legs 18. In this way, regardless of the direction of tidal flow, one or more of the legs 18 will be located downstream of the turbine 12. Referring to
The system 10 is also preferably positioned, with respect to the prevailing direction of tidal flow, such that the pair of downstream legs 18 are each positioned on a line which runs substantially normally to the direction of tidal flow A. In this way an equal force is applied to each of the legs 18, improving the stability of the base 14 on the seabed B When the tide reverses to flow in the opposite direction AA the two legs 18 which were downstream of the turbine 12 will now be located upstream of the turbine 12, while the remaining single leg 18 will now be located downstream of the turbine 12. Again the tidal flow acting against the turbine 12 will generate a turning moment, which results in the frame 16 behaving like a lever, and transmitting this turning moment into a downforce acting through the single downstream leg 18. Again this downforce will result in significant gripping and/or penetration of the contacting end 24 of said leg 18 into the seabed B in order to prevent unwanted movement of the system 10.
In addition to the above generated forces, the turbine 12 is operating in the tidal flow and undergoing rotation to generate electricity. As a result a torque will be generated by the turbine 12. Again the positioning of the legs 18 with respect to the turbine 12 will result in this torque being transmitted downwardly through the base 14 into the legs 18 in order to further increase the downwardly acting force experienced by the legs 18. Thus the operation of the turbine 12 further acts to secure the system 10 in position against unwanted movement along the seabed B.
As mentioned above, the shape of the frame 16, in addition to the number of legs 18, may be varied once the above-described functionality is maintained. However, the use of three legs 18 ensures that regardless of irregularities in the contour of the seabed B, all three legs 18 will contact the seabed B in order to provide stability to the system 10. In addition, the use of three legs 18 is the minimum number of legs which will allow the system 10 to be stably positioned on the seabed B. This thus maximises the pressure which is exerted by each leg 18 on the seabed B in order to effect penetration of the seabed B. While additional legs 18 could be provided, this would decrease the pressure exerted by each leg 18. It will therefore be appreciated that the use of three legs 18 in a triangular configuration provides a number of benefits to the system 10.
As detailed above, the system 10 are transported to the installation site and lowered into the sea by suitable means. The system 10 is lowered towards and onto the seabed B, as illustrated in
When lowering the system 10 it may be beneficial to let the “front” leg 18 down first. This will allow the system 10 to be rotated about this leg 18 (by manoeuvring the vessel used when lowering the system 10 to the seabed B) until the system 10 has been brought into the correct orientation so that the turbine 12 is in line with the tidal flow. At this point the back two legs 18 are lowered. This approach may mean that the front leg 18 may not have the fins 28, as the fins 28 would make it more difficult to rotate the front leg 18.
As no drilling or other preparatory operations are required as a result of the configuration and operation of the system 10, the design thereof allows the turbine 12 to be pre-installed on the base 14 prior to deployment of the system 10 onto the seabed B. If drilling or other operations such as pile driving were required in order to secure the system 10 in position, then any turbine 12 mounted thereto during such operations would be at significant risk of damage, and would thus not be a viable option. Thus it will be appreciated that the system 10 of the present invention provides a significant number of advantages over prior art methods of installation of tidal turbines on the seabed.
The system 10 is also capable, as a result of the design of the legs 18, and in particular the tapered contacting ends 24, to be lifted off the seabed B by suitable hoisting means (not shown) in the event that the turbine 12 or base 14 require maintenance. Once such maintenance has been performed, the system 10 is simply lowered back onto the seabed B, where the base 14 will again automatically penetrate the seabed B to secure itself in position. It is therefore not necessary to exactly reposition the system 10 at the location from which it was removed for maintenance. This significantly reduces the accuracy required when repositioning the system 10, thereby reducing the time taken to complete this task.
| Number | Date | Country | Kind |
|---|---|---|---|
| 08022012.2 | Dec 2008 | EP | regional |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2009/008940 | 12/14/2009 | WO | 00 | 8/18/2011 |
