GB2153917A - Tide powered electrical generator - Google Patents

Abstract

A tide powered electrical generator comprising reservoir means (2), and electrical generator and valve arrangement (8, 10, 12, 14) via which a tidal water source is arranged to flow to and from the reservoir means (2), a chamber (18) surrounding a pontoon 16 in which the generator and valve arrangement are contained, through which chamber (18) tidal water flows via the generator and valve arrangement to the reservoir and via the generator and valves water is returned to the tidal water source, and position control apparatus (20,22) Fig. 3 operative to control the vertical position of the pontoon 16 within the chamber (18) whereby the generator can be positioned within the chamber (18) so as to be driven as the tide ebbs and flows consequent upon appropriate operation of the valve arrangement. Reservoirs 28,30,32,34 may be operated so as to provide appropriate water heads or sinks to maintain operation at all tide states. <IMAGE>

Description

SPECIFICATION Tide powered electrical generator This invention relates to tide powered electrical generators.

Tide powered electrical generators are known. The known tide powered electrical generators are however often inefficient since they do not make full enough use of tidal inflow and ebb.

According to the present invention a tide powered electrical generator comprises reservoir means, an electrical generator and valve arrangement via which a tidal water source is arranged to flow to and from the reservoir means, a chamber in which the generator and valve arrangement are contained, an inlet gate in the chamber via which tidal water is fed to the generator and valve arrangement and via which tidal water is returned to the tidal water source, and position control apparatus operative to control the vertical position of the generator and valve arrangement within the chamber whereby the generator can be positioned within the chamber so as to be driven as the tide ebbs and flows consequent upon appropriate operation of the valve arrangement.

By providing position control apparatus operative to control the vertical position of the generator and valve arrangement, a tide powered electrical generator is afforded which can be operated effectively during various states and conditions of the tide.

The valve arrangement may comprise two inlet valves and two outlet valves arranged so that the generator can be driven in the same rotary direction when the tide ebbs as when it flows.

The generator may comprise a pair of juxtaposed rotors between which the tidal flow is directed via the valve arrangement so that flow between rotors of the generator is in the same direction during ebb as during flow of the tide.

The reservoir means may comprise a plurality of bays arranged in mutual communication via bay valves.

The bays may be arranged on each side of a central passageway and arranged to communicate with the passageway via predetermined bay valves.

At least one of the bays may include valves which are arranged to communicate with the tidal water source.

One embodiment of the invention will now be described solely by way of example with reference to the accompanying drawings in which: Figure 1 is a plan view of a tide powered electrical generator; Figure 2 is a perspective view of the front part of the tide powered generator shown in Figure 1; and Figure 3 is a side view of a part of the tide powered generator shown in Figures 1 and 2.

Referring to the drawings, a tide powered electrical generator comprises a reservoir 2 into which water from a tidal turbine 6. The turbine 6 can form part of, or be coupled to, an electrical power generator (not shown).

Two valves 8 and 10 allow tidal water to flow into the reservoir 2. Two further valves 1 2 and 14 are provided so that water in the reservoir 2 can be returned via the valves 1 2 and 14 to the tidal source without reversing the direction of rotation of the turbine 6.

Thus, when the valves 8 and 10 are opened, the turbine 6 will be driven by the incoming tide as water flows into the reservoir 2 and when the valves 1 2 and 14 are open, reverse flow is permitted to drive the turbine 6. It will of course be appreciated when the valves 8 and 10 are open, the valves 14 and 1 2 will be closed and conversely when the valves 1 2 and 1 4 are opened the valves 8 and 10 will be closed.

The valve arrangement comprising the valves 8,1 0, 1 2 and 14 and the turbine 6 are mounted on a pontoon 1 6 which is arranged to be vertically movable against copper/bronze seals 1 7 in a chamber 1 8. The pontoon 1 6 is mounted on hydraulically operated barriers 20 and 22, side faces 24 of which are arranged to be sealed against the side of the chamber 1 8 so that flow from the inlet gate 4 to the reservoir 2 is permitted only via the inlet valves 8 and 1 4. The hydraulically operated barriers 20 and 22 are sealed in part tubular seals 26 which extend across the bottom of the chamber and which facilitate pivotal movement of the barriers 20 and 22 so that the vertical position of the pontoon 1 6 can be adjusted within the chamber 1 8. The barriers 20 and 22 are also provided with side seals. Thus the effective vertical level or position of the turbine 6 can be controlled in dependence upon tidal states and conditions thereby to produce optimum turbine operation.

In order to facilitate optimum operation, the reservoir 2 is divided into four bays 28,30,32 and 34 and a central passageway 36. The passageway 36 is arranged in communication with the bays 28,30,32 and 34 via valves 38,40,42 and 44 respectively. The bays 28 and 30 are coupled via a valve 46 and the bays 32 and 34 are coupled via a valve 48.

Additionally the bays 28 and 32 are provided with inlet valves 50 and 53 respectively, these inlet valves 50 and 53 being arranged in communication with the tidal water source.

Although four bays 28, 30, 32 and 34 only are shown in Figure 1, a plurality of further bays (not shown) may be provided and accordingly additional valves 64, 66 are provided to provide communication with the additional bays when they are in use. The number of bays provided is infinite and will be determined in accordance the capacity of the electrical generator system. Various modifications to the arrangement thus far described may be made and for example the turbine which in the present example comprises a pair of juxtaposed turbine rotors 56 and 58 may be of alternative construction.

The electrical generator operates as follows.

Initially the pontoon 1 6 is lowered so that the inlet gate 4 is below water level. Tidal water then flows through the valve 8 which is open from the tidal source. It will be appreciated that since the pontoon 1 6 and the hydraulically operated barriers 20 and 22 are sealed within the chamber 18, the only path for water flow is through the valve 8 and the turbine rotors 56, 58 to the reservoir 2 via the outlet valve 10. The valve 14 is closed and the valve 12 is also closed. Tidal water thus flows into the passageway 36. Valve 38 is opened and tidal water thus flows into the bay 28. The valve 38 should be adjusted to control the flow until the tidal level is well up.

The valve 40 of bay 30 is then opened so that water continues to flow into bay 30 at slack tide. At this stage, valve 38 is closed and valve 50 of bay 28 is opened, so that bay 28 will be filled as far as possible from the tidal source. When this has been achieved or when the flow through the valve 50 ceases, valve 50 of bay 28 is closed. Water will still be flowing into bay 30 until the water in bay 30 is of useful height and the tide has fallen off to a sufficient level to enable the outlet side of the turbine rotors 56, 58 to be raised above the tidal source level, with the water in the passageway 36 below the level of the water in bay 28. At this stage, valve 38 will be opened, valve 10 will be closed, valve 1 2 will be opened, valve 1 4 will be open, and valve 8 will be closed.This will allow water from the bay 28 to flow back through the passageway 36, through the valve 12 and the turbine 6 to the tidal source via the valve 14 and the gate 4. This flow is shown in Figure 1 by a broken line having two arrow heads.

The water will be of sufficient capacity with the combined capacity of bays 28 and 30 to keep the water flow going.

Bay 28 will flow to its lowest usable level, and then valve 38 will close and valve 40 will open. Valve 50 opens to scavenge bay 28 to the lowest level and then closes. Flow is now taken over from bay 28 by bay 30. The volume of water in bay 30 should be sufficient to supply flow until the tide has turned and risen to a height sufficient to allow adequate flow through the turbine rotors 56, 58 into bay 32. At this stage, valve 14 closes, valve 10 opens, valve 1 2 closes, valve 8 opens, valve 42 opens, valve 40 closes, and valves 50 and 52 open to scavenge bays 28 and 30 respectively when bays 28 and 30 are at their lowest level. At this stage, valves 50 and 52 are closed and valve 42 is opened to allow flow into bay 32. This flow into bay 32 continues until the tide rises to a point where the flow is likely to be insufficient.Then the valve 42 closes and the valve 44 opens.

Valve 54 opens to fill the bay 32 until the highest possible level is attained. Bay 34 takes the inflowing tide until the tide has dropped off to the point again where the water in the passageway 36 is below the level of the water in the bay 32, and the outlet can be above tide. At this point, valve 10 closes, valve 14 opens, valve 8 closes and valve 1 2 opens. The pontoon 1 6 raises above the tide level. The process continues until conditions as regards tide levels are as they previously were, when again the pontoon 1 6 lowers below tide. The valve 8 opens, valve 1 2 closes, valve 14 closes, valve 10 opens, valve 38 opens and the process repeats as previously described.

The gate valves 8, 10, 12, 14 must be of an adequate size to accomplish maximum flow, and to take in as much water as quickly as possible. Valves 50 and 52, should also be of a size to take in as much water as needed as quickly as possible.

Valves 64 and 66 are shown to illustrate that further emergency storage bays could be provided to accommodate for failures in other bays or to expand the entire electrical generator. The electrical generator is advantageously built in a harbour to protect it from rough weather. The bays 28, 30, 32, 34 may be used for fish farming and with locks etc. could probably be used for small craft etc. Thus the electrical generator may add to amenities and conservation, and may eliminate or reduce carbon dioxide pollution. There would be no nuclear dangers and no fuel costs.

Figure 2 shows that a copper/bronze seal 1 7 is employed on the bottom of the pontoon 16. Also shown schematically in Figure 2 is an automatic flooding valve 70. More than one automatic flooding valve 70 may be employed if desired.

Figure 2 shows in more detail the inlet/outlet gate 4. Thus it will be seen that the gate 4 has an oriface 72 and a control flow plate or gate 74. As the pontoon 1 6 moves up and down, it runs against fixed bearings 76 which are positioned between the gate 4 and the pontoon 1 6.

Figure 3 shows a housing 78 for the electrical generator turbine 6. A turbine compart ment 80 and a waterproof compartment 82 are also shown.

By way of example, it is mentioned that the tide may be 18ft tide, and the turbine may require a 3ft head. The tide time may be 6 hours each way, and the flow through the turbine may be 5ft X 2ft, i.e 10 sguare ft. A flow of lOft per second equals a 100 cubic ft per second = 6000 cubic feet per minute = 360000 cubic ft per hour.

By way of example, it is mentioned that the bay 28 may be 200 ft wide, 600 ft long and 18ft deep. The water may rise at 3ft per hour.

The flow into the bay 28 after approximately 5 hours would give 15ft of water in the bay 28. The valve 38 may then be closed. Valve 40 may then be opened into bay 30 which contains a low level of water. Valve 50 opens to flood the bay to the highest level and then closes at approximately the maximum level of water. Water flows into the bay 30 for example for 3 hours. The bay 30 will then contain 9ft of water and, at this stage, the tide will have fallen off for approximately 2 hours being, for example, 6ft below the maximum level in the bay 28. The pontoon 1 6 will raise above the falling tide to the required depth head below water level in the bay 28.

Valve 38 opens,valve 10 closes, valves 12 and 14 open,valve 8 closes, and valve 40 closes. This gives 6 hours running time as the bay size and capacity and design cater for flow of eguipment in use so that it will run until approximately a few hours after low tide or valve 40 will open when needed to supply a longer flow out and slower level drop off.

When the tide has risen enough to allow sufficient head, the pontoon 1 6 will lower.

Valves 40 and 38 close. Valve 42 opens and then valve 8 is opened, valve 1 2 is closed, valve 1 4 is closed, valve 10 is opened and the sequence starts again. At bays 28 and 30, the valves 50 and 52 would open to empty the bays to the lowest level to begin the process on the next low tide cycle. Usually, the valves will be arranged to be installed so that they are computer operated. The area below the pontoon 1 6 is flooded to water level on the highest side using an automatic valve system in the dam gate 4 to assist the pontoon hydraulics.

Although tidal power has been tried in various ways, it is to be appreciated that the present invention does not rely on waves but on the incoming tide and the outgoing tide.

The electrical generator will be built to an appropriate size, for example to take into account the type of turbine 6 used and to make arrangements such that a flow of water is available at the slack tide period until the tide is falling off sufficiently to allow the back flow.

Small electrical generators of the present invention may be manually controlled. Larger permanent electrical generators may be controlled by computers as indicated above, and these computers may be designed around flow sensors, the height of tides, water flow etc., It is to be appreciated that the embodiment of the invention described above with reference to the drawings has been given by way of example only and that modifications may be effected. Thus, for example, different types of seals may be employed for ensuring that the water flow is always through the turbine rotors 56,58.In order for the sealed floating pontoon 1 6 to follow the tide below the required head for a turbine 6, the pontoon 1 6 may have a bottom water flow area containing turbines sealed in a watertight manner from an upper area where generators, and fluid or air pumps may be situated. Such areas were mentioned above as areas 80,82 and they may be of a different shape and size than shown in Figure 3. The equipment may be driven by a sealed shaft from the turbine 6, making it unnecessary to develop a combined turbine generator. 8uch an arrangement may give a 24 hour fully controllable output for a multi-stage output,with a spare unit taking over as each unit is disengaged at changeover level on forward and reverse sequence of tides.Various options are available such for example as air pumps for air turbines, fluid pumps for fluid turbines, or direct alternator drive, whichever is convenient for any given situation and appropriate for the equipment that is available or economically possible.

The bays 28,30,32,34 may have turbines incorporated for added output. The volume of water then employed should allow the sequence to function to its optimum on the main generator unit, and the additional power units could be installed in areas of the main inlet gate 4, and the inlets 38, 40,50,53 etc.

With reversible alternators, the pontoon 1 6.

can be made slightly less complicated.

The generators may be fabricated in ship yards and transported and assembled on site.

Underdeveloped countries may benefit as smaller generators may be operated with minimal training, installation of the generators only requiring normal engineering skills. The bays may be erected by normal labour, the requirements being size, freedom from damage by insects and environmental hazards, and watertight. For those parts of the generators in contact with seawater, stainless steel is preferably used. Plastics materials and carbon fibre materials may also be used. Strengthening of working areas may be effected by materials such for example as reinforced concrete. It can be arranged that there is always some water in the bays so that fish farming with locks, or marinas become possible. Concrete or other suitable materials can be used for buildings containing equipment.

As the generator operates, pontoon lifting is effected by displacement of water. Once the generator is in operation, programmes may be worked out as overlap in the volumn of the bays would allow delay in changeover at certain tide conditions, the remainder of a bay being used and switched in as required depending upon tides, such for example as neap, spring and freak tides. It is to be noted that the pontoon 1 6 follows the tidal inflow and the tidal outflow. The pontoon position is advantageously continually monitored and automatically adjusted to ensure the correct water head and flow for the turbine or turbines 6 in both directions.

The invention includes the various parts of the generator taken singly or in any combination.

Claims (7)

1. A tide powered electrical generator comprising reservoir means, an electrical generator and valve arrangement via which a tidal water source is arranged to flow to and from the reservoir means a chamber in which the generator and valve arrangement are contained, an inlet gate in the chamber via which tidal water is fed to the generator and valve arrangement and via which tidal water is returned to the tidal water source, and posi- tion control apparatus operative to control the vertical position of the generator and valve arrangement within the chamber whereby the generator can be positioned within the chamber so as to be driven as the tide ebbs and flows consequent upon appropriate operation of the valve arrangement.

2. A tide powered electrical generator according to claim 1 in which the valve arrangement comprises two inlet valves and two outlet valves arranged so that the generator can be driven in the same rotary direction when the tide ebbs as when it flows.

3. A tide powered electrical generator according to claim 1 or claim 2 and including a pair of juxtaposed rotors between which the tidal flow is directed via the valve arrangement so that flow between the rotors of the generator is in the same direction during ebb as during flow of tide.

4. A tide powered electrical generator according to any one of the preceding claims in which the reservoir means comprises a plurality of bays arranged in mutual communication via bay valves.

5. A tide powered electrical generator according to claim 4 in which the bays are arranged on each side of a central passageway and arranged to communicate with the passageway via predetermined bay valves.

6. A tide powered electrical generator according to claim 4 or claim 5 in which at least one of the bays inciudes valves which are arranged to communicate with the tidal water source.

7. A tide powered electrical generator substantially as herein described with reference to the accompanying drawings.