GB2235252A

GB2235252A - Electrical power generation using tidal power

Info

Publication number: GB2235252A
Application number: GB9002209A
Authority: GB
Inventors: Geoffrey Edward Lewis
Original assignee: Individual
Current assignee: Individual
Priority date: 1990-02-01
Filing date: 1990-02-01
Publication date: 1991-02-27
Anticipated expiration: 2010-02-01
Also published as: GB9002209D0; WO1991011614A1; AU7232091A; GB2235252B

Abstract

Figs. (1 and 2) show a power generating installation constructed either within a river, an estuary or off-shore between an artificial island (3) and the coast line (2). Both the main structure of the barrier and the turbine ducts have venturi shaped profiles to maximise the water velocity. The turbines are positioned within profiled ducts in the barrage (1), linking these two structures. The profiles being designed to act as primary and secondary venturis, to increase the flow rate of the water through the turbines. The cases for both bi-directional and uni-directional water flow being covered. To avoid the periodic complete loss of power generation, that would occur with estuarine and coastal installations at times around tidal flow changes, several such generating stations can be built to make use of the tidal phasing. If three such stations are suitably positioned and their outputs linked by a central distribution station, power generation will be continuous.

Description

ELECTRICAL POWER GENERATION USING TIDAL POWER.

Specification.

This invention relates not to the use of water turbine driven electrical generators for creating electrical power7 but to the 5i ting, positioning and design of the necessary infrastructure required to overcome the problems associated with other installations. It is generally accepted that the most effective way of generating electrical power from the sea is by the use an estuary barrage that houses the necessary turbine/generator equipment. However, current technology does not allow energy to be generated during periods close to the times of high and low water levels. In addition, the concept has some serious environmental problems. The system proposed in this invention utilises the efficient generation equipment of such schemes and resolves the problems by moving the complete installation off-shore and into deeper water.The barrage (1) being formed between the coast-line (2) and an artificial off-shore island (3).

constructed from concrete and in the manner shown in Fig.t.

This proposal avoids the environmental problems and allows power generation to be continuous and at the same time, reduces coastal errosion.

Observation of the tidal flow along a coast line will show that most of the wave energy approaches land obliquely. The forces shown in Fig.2 due to this flow (T) can be resolved into two components. One directly on-shore which is responsible for coastal errosion (E) and the other parallel to the shore-line (P) and responsible for the tidal phasing along the coast-line. If the angle of obliqueness A lies in the range 30 to 4sot, then since the available power is proportional to the sine of angle A, 50% to 70J; of the energy in the tidal flow (T) is available to drive the generation system.

Fig.1. shows the juxtaposition of the turbine/generator barrage (1), the coastline (2) and the artificial island (3), in relationship to the tide levels and flow. Since the system is scaleable to meet the local power and other demands, the dimensions have all been rationalised.

Fig.2. shows the relationship between the direction of tidal flow (T), the coastal errosion force (E) and the resolved power component P = TsinA.

Description.

Fig.l shows that the island and coastal outline have been given an elliptical shape. This is to produce a venturi effect that will increase the flow rate of sea water through the turbines/generators that are built into the barrage. In particular, this helps maximise the water flow rate at periods close to high and low water levels and under conditions of Neap tides. Isseally, a venturi should have an exponential profile, but in this case, it has to be effective with tides that periodically alternate. The elliptical shape is a good compromise under these conditions.The profile is calculated from the formula Ix2Sa2 + y2Xb2) = 1, where the constants a and b are the semi-major and semi-minor axes of the ellipse respectively. The choice of the ratio a:t determines the curvature of the profile and hence the throat restriction of the venturi. Typically a 20% reduction provides a good compromise and this is given by using a ratio of 1.9:1. Since the proposed concept is scaleable, design starts with the required number of generator sets that are needed to provide the desire power output. This then fixes the length of the barrage and from this the mouth dimension and island length can be calculated.

To avoid, the periodic complete loss of power generation during tide reversals, several such generating stations can be situated along a coast-line to make use of the tidal phasing. If three such station are suitably positioned and their outputs linked by a central distribution station, power generation will be continuous.

Claims

Claims.

1. R power generating station is established off-shore to produce electricity from tidal power using a barrage between shore and an artificial island.

2. As claimed in Claim 1, a chain of such stations can continuously produce electricity.

3. Whereas estuary type barrage schemes cannot be built in series to provide continuous generation, the claim in Claim 2, effectively places generating stations in parallel. This ally'as the chain of stations to provide continuous generation due to the overlapping nature of the tidal phases.

4. As claimed in Claim 1, the magnitude of pWJJer generation is scaleable. The simplest case consisting of a single turbinefgenerating set.

5. If judiciously placed, the islands claimed in Claim 2, will have a significant impact on the reduction of coastal errors ion 6. Moving the barrage as claimed in Claim 1, avoids the silting and environmental problems associated with an estuary type barrage generating scheme.

7. 45 claimed in Claim 1, electrical energy can be generated continuously from the non-polluting power source of the tides.

8. As claimed in Claim 1, some of the islands need not be completely passive. In suitable places, the outer walls can be adapted to perform the duties of harbour or marina type installations.

9. The ins ill material required for the core of the artificial islands as claimed in Claim 1, will generally be available from construction sites such as the Channel Tunnel.

Amendments to the claims have been filed as follows 1. A power generating station is established either within an estuary or off-shore, to produce electricity from the power of the tidal flow rate using a barrage between the shore and an artificial island. The tidal velocity being magnified by the application of the ventur effect.

3. Whereas estuary type barrage schemes cannot easily be built in series to provide continuous generation, the claim in Claim 2, effectively places generating stations in parallel. This allows the chain of stations to provide continuous generation due to the overlapping nature of the tidal phases.

4. As claimed in Claim 1 1, the magnitude of power generat on is scaleable. The simplest case consisting of a single turbine/generator set.

5. If judiciously placed, the islands claimed in Claim 2, will have a significant impact on the reduction of coastal erros ion.

6. As claimed in Claim 1, dividing the estuarine barrage into two sections, avoids the silting and environmental problems associated with i full barrage.

7. As claimed in Claim 6, this method of construction allows full access to any up-river port without the need to provide access locks.

8. As claimed in Claim 2. electrical power can be generated continuously from the non-polluting power source of the t ides.

9. As claimed in Claim 17 some of the islands need not be completely passive. In suitable places the outer walls can be adapted to perform the duties of harbour or marina type installations.

10. Much of the inf ill material required for the core of the artificial islands as claimed in Claim 1, will generally be available from the shore end of the construction site.