Submerged Tidal Generator.

A PATENT HAS BEEN APPLIED FOR

For Further Details Please Click Here  

1.0 INTRODUCTION

1.1 The Requirement.

The approaching energy deficiency in theUK has been forecast for some time and should have been the subject of much debate, however there has been a general hesitation to bring into open discussion certain delicate subjects, namely, nuclear power and the pollution from existing generators. New nuclear power generation, and the cleaning up of emissions from existing the coal and gas generators, is going to be expensive to introduce and expensive to maintain. Simply put, energy costs are going to rise very substantially. Costs to the users are going to increase, in fact the end of this long period of low cost energy, that we all have enjoyed, is rapidly approaching.

1.2 Generation Power Source Merits.

The table below gives a comparison of the attributes between the various alternative forms of energy available. From the outcome of this comparison it can be seen that the least intrusive and most suitable form appears to be tidal energy and for complete approval a Submerged Tidal Generator, appears the most desirable (STG).

Attribute Ê Source Ð	Renewable Source	Low Capital Cost	Low Running Cost	Minimum Environment Impact	Predictable	Minimum Visual Impact	Modular
Fossil	No	Yes	No	No	Yes	No	No
Nuclear	No	Yes	No	No	Yes	No	No
Wind	Yes	No	Yes	Yes	No	No	Yes
Solar	Yes	No	Yes	Yes	No	No	Yes
Hydro	Yes	Yes	Yes	No	Yes	No	No
Wave	Yes	No	Yes	Yes	No	No	Yes
Tidal	Yes	Yes	Yes	Yes	Yes	Yes	Yes

2.0 Unique Turbine Design

2.1 Design Concept

Although the submerged turbine generator would have more in common with the wind turbines than with the impulse and reaction water turbines, the water would have much more mass and would be moving more slowly. A cubic unit of water weighs about 854 times than that of a cubic unit of air at sea level. Also, unlike air, water cannot be compressed. Because no information could be found on this type of submerged turbine generator, the same method was used for calculating their power output as is used for wind turbines. The amount of kinetic energy that passes through a turbine can be calculated using the formula:

(KE = ¹/₂ x M x V² M = mass V = velocity )

Because the mass passing through the blades in one second is a factor of the current’s velocity, the power produced by the current does not increase by the square of its velocity, but by its cube. Therefore, the equation for the kinetic energy passing through a submerged turbine generator can also be written:

(KE = ¹/₂A x D x V³ A = area swept – cu.m. D = density- kg/cu.m. V = velocity- m/s)

If we assume our vertical axis three bladed turbine (60 meters diameter by 15 meters high), has paddles 30m long by 15m high and a total swept volume of,

3.142 × 30² × 15 = 42417 cu m

and it is to be used in a four knot tidal area. If we further assume that the summation of the out put torque from all three paddles is the of the submerged turbine generator is the equivalent of one paddle under full power for one third of a revolution, (bearing in mind that there is always two and some times all three paddles producing torque.);

4 knots = 1.852 x 4 = 7.408 kl / hour = 7.4 x 1000 ÷ 3600 = 2.06 m / sec

When this is used in the KE formulae, it appears that -

½ (14139 × 1025 × 2.06³) = 63,345,274 Joules or watts, -

63 mw per turbine could be theoretically possible.

Albert Betz, in 1919 determined that, theoretically, no more than 59.3 percent of the kinetic energy in the wind can be converted to useful mechanical energy. The Betz’ law applies to wind turbines – not to a submerged turbine generator. The formulas that calculate the maximum kinetic energy obtainable from a wind turbine may understate the power obtainable from a submerged turbines generator that is equipped with full paddle blades. Although most of the energy being transferred to the water turbine could be in accordance to the Betz’ law, because water is not compressible, the total amount captured by a full-bladed submerged turbine generator could be more than that coming from the kinetic energy of just that water mass in the turbine’s sweep area. When the generator is loaded, the water turbine blades tend to slow down, what forces are at work? Is additional energy coming from the inertia of that uncompressible water that would be pushing from behind the water that is passing through the turbine. In other words, the energy being applied to the turbine could be partly in the kinetic form and partly in the pressure form. If there would be any additional energy coming in the pressure form, it would have the same affect as increasing the mass acting on the submerged turbine generator. If there were any additional energy input from the inertia of that water pushing from behind the water that is passing through the sweep area, the apparent efficiencies could be inflated above the limits of the Betz’ law. This would not mean that a full-bladed submerged turbine generator would be operating at those higher efficiencies, but rather that there is additional energy input in the pressure form that is not being considered. If there is any additional energy from the inertia of the non-compressible water, it should affect our design of submerged turbine generator, which uses flat full area paddles as opposed to narrow aerofoil sections.

Rotor Frame and Paddle Interaction Description.

Paddle C is coming round into the flow with minimum area obstructing the water flow.  Paddle B is still closed due to the water pressure against it and is still generating a counter clockwise torque.  Paddle A is now at an angle of around 45° to the water flow and is now generating a much stronger counter clockwise turning torque.  Paddle C is trying to steer to its left (so supplying torque) due to either the use of an aerofoil section, or a small fixed rudder, fitted to the trailing inboard edge, (see Sketch A1 below).

2.2 Three Paddles Supplying Torque Simultaneously.

With the Submerged Turbine Generator rotor at the angle shown in Sketch B,

All three paddles are producing torque.

A, is producing counter clockwise torque.

B, is ending the power stroke.

C, has started its power stroke.

2.3 The Relationship Between Paddles and Frames.

So far I have only discussed a Submerged Tidal Generator with three frames and one paddle per frame.  Three frames, I think, will be the final build; I can’t see any major advantages in going to four, although it will be looked at.  There is little doubt in my mind that there will be multiple paddles.  On a large rotating frame a single paddle would be slow to react and contain a large amount of energy when it flops over.  Multiple paddles would execute the same function in a smoother and less violent manner.  The optimum number of paddles will be decided when computer modelling has revealed the dynamics of the variations.  Sketch C and the M series of sketches, all examine the STG with three paddles per frame.  The response that is required from the paddles will ultimately define the number of paddles that are to be used; be it, one of 30 meters length, two of 15 meters length, or even ten of 3 meters length, it makes little difference to the performance.  At this size the paddles would be similar in size to big ship stabilizer fins, many of which have given over 30 years of submerged trouble free service.   

2.4 Three Paddle – Angular Interaction.

2.5 Design Reconciliations.

2.5.1 Paddle Mountings

The paddle swivel point is shown in all the sketches as being approximately one third of the length of the paddle back from the paddle outboard edge.  This is an arbitrary selection that was used for a simple model.  In actual practice the swivel point could be any where from the leading edge to close to the middle line of the paddle.  The outboard edge position would increase the torque being applied to the frame, since it would be effectively increasing the diameter of the frame, but possible would give problems with all the torque being applied to the outboard end of the frame.  During final design the optimum point for this along with the optimum number of paddles should be decided, however it may turn out to be a design variable that has to be adjusted according to the tidal speed and turbine size.

3.0 THE MERITS OF STG’S.

1. The tide as a resource has around 850 times the energy intensity of a wind site, for similar wind and tide speeds, so Submerged Tidal Generator need only a fraction of the swept area of a wind turbine, however speeds are much lower.  So trading, density of water compared to density of air, against, speed of wind and speed of tide, looks like (850 to 1) minus (30 to 3), a very attractive increase in potential energy.
2. Once an area of intense tidal activity is located, tidal devices can be closely spaced in a string across it.  There is no need for wide spacing of the machines as in traditional wind farms.
3. Correctly sited Submerged Tidal Generator's will deliver their specified power on time every tide, indefinitely.
4. They are a direct replacement for Primary Generators.  The regular pattern of the tides enables energy to be produced to a time table.  This time table can be developed after only a few months site monitoring, unlike the years it takes to validate a wind generation site.  Having confidence in the energy production of a renewable installation overcomes one of the biggest hurdles in achieving project finance.
5. Wind and wave generators have to be designed to withstand the “Worst Storm in a Century” scenario.  Submerged tidal generators are not subjected to such a large variation in operating conditions.
6. Tidal turbines also have a very small environmental and social impact:  
7. They are totally submerged, and will therefore cause no visual intrusion or bird disturbance;
8. They have slow moving rotors (much slower than ship's propellers) and so will cause far less disturbance to sea mammals;
9. They are passive energy absorbers, so will produce less underwater noise than ships of a similar power rating, which put energy into the water. Marine life disturbance is therefore minimised.
10. A large proportion of the costs of smaller wind farms, is the cost and disruption caused by the requirement of constructing access to the site (often on mountainous land and often several miles long).  This nearly always involves digging out boggy ground, filling with many hundreds (even thousands) of tons of hard core, bridging streams and digging out substantial foundations.   
11. Getting wind turbines to the installation site is also very disruptive, time consuming and expensive.  Once at the site, they have to be assembled, which can be weather dependent.  Crews are often held up with high winds, exacerbating crew and crane costs.    
12. STG machines maintain an operating blade tip clearance to Low Water of ten meters or more; they therefore cause no disruption to shipping.
13. The cost of Sizewell B (£2.4b) to supply 1600mw, gives a capital cost of £1.5m/mw to construct and bring on line an STG.  Just now in theory, we are looking at an STG generating in excess of 200mw, would this cost £300m or less?

4.0   INSTALLATION OF STG’S

4.1   STG’s in Use.

The overall concept for the use of these Submerged Tidal Generator (s), visualises them as being constructed in a dockyard, then floated out to sea and into the area of intended use, and slowly sunk in a controlled manner, into their allocated site.  The platform could take on any shape that was found to be advantageous.  Platform size would be restricted only by the manufacturers handling capacity and or the commercial restraints of inter dependence between the Submerged Tidal Generator (s); (to take one turbine out of service, would mean taking all the platform turbines out of service).  For this reason I have looked at an equilateral triangular shaped platform holding three Submerged Tidal Generator (s), although it might be preferable to use even numbers of turbines, to allow contra rotation to cancel out any torque reaction with the seabed.  The STG’s as designed are omni-directional generators, so they will develop power no matter which direction the tide is flowing.  This triangular shape, placed correctly will present a wall of turbines to a tidal flow, or in swirling tides it may be capable of extracting a greater energy level out of the swirling tidal flow.  The basic design must give the platform self floating and sinking abilities.  Along with generators for generating electrical power, air compressors and compressed air storage facilities would be fitted, which when brought into use under a computer controlled management system, would have the capability of floating the platform off the sea bed, under the control of, and assisted by, a surface vessel.  This ability would be one of the design criteria, for the Submerged Tidal Generator (s) to be able to auto hook and unhook itself (from the cable network) and in a controlled manner rise to the surface.  Similarly, it would be capable of sinking, again in a controlled manner, and re-connecting itself to the cable network.

4.2       STG’s The Future

It is possible to design these with an operational life (between services) in mind, say 5 years.  On the expiration of the service life, they would be re-floated and towed into (maybe dry-docked or slipped) a suitable area to be serviced and brought up to date with the latest developments.  With sufficient of these installed, spare STG’s could be available to enable one to be taken out of service and a replacement one sunk in and hooked-up, with minimal supply disruption.  A full time maintenance yard would them service the out-of-service Submerged Tidal Generator (s) and ready it for further use. 

5.0  FURTHER DEVELOPMENTS.

1. Simpler version of this Submerged Tidal Generator (s) could be fitted around the base of navigation buoys, allowing them to be changed from being gas powered to electrical powered.  This would open up a whole new field, cutting maintenance drastically, and allowing electrical driven navigational transponders and audio warning devices, to be installed.
2. The existing design Submerged Tidal Generator (s) can stand vertically and extract power from moving wind.  In this mode it would be an omni-directional wind mill for electrical generation or water pumping duties.
3. A simply version of 2 could be used to build simple plastic constructed yachts as a direct replacement for the Mediterranean resort’s Pedelo’s.
4. A sophisticated version of 3 could be built as a serious challenger to sail driven recreation yachts.  Speed control being obtained by fitting variable and controllable, paddle pitch stops.  The design could allow the three frames to be unlocked from their 120º configuration, and swung round so that they are all parallel and positioned in the fore aft direction, for close-quarter manoeuvring and mooring.  The idea of a wind driven yacht always being able to steer in a straight line, regardless of wind direction, is exciting and demands to be tried.  
5. Simpler versions of 4 could be built and used as the first yachts to sail the canal waterways.
6. Wheeled versions of 4 could be built as beach buggies, for transport over sandy beaches or even desert tracks.  It could be further modified to operate over ice or snow.

A PATENT HAS BEEN APPLIED FOR

For Further Details Please Click Here  

Submerged Tidal Generator.