GB2564886A

GB2564886A - Tidal energy capturing system

Info

Publication number: GB2564886A
Application number: GB1712042.9A
Authority: GB
Inventors: Ekern Rod
Original assignee: Individual
Current assignee: Individual
Priority date: 2017-07-26
Filing date: 2017-07-26
Publication date: 2019-01-30
Also published as: WO2019021000A1; GB201712042D0

Abstract

A tidal energy capturing system 10 comprises a lower storage reservoir 12 located at a first height above sea level, an upper storage reservoir 14 located at a greater height above sea level, and a first turbine (30, figure 2) located at or around sea level in a moving body of water to be driven by the water movement. The first turbine 30 is coupled to a first pump 32 and pumps water from the lower storage reservoir 12 to the upper storage reservoir 14. A second turbine 40 is located between the lower and upper storage reservoirs, to be driven by a flow of water from the higher storage reservoir to the lower storage reservoir. The first turbine 30 may be arranged in a barrier dividing the body of water into first and second volumes, and the barrier may comprise conduits and valves that provide a uni-directional flow through the turbine regardless of the direction of flow through the barrier (figure 2). The invention provides a pumped storage system powered by e.g. tidal energy.

Description

The present invention relates to renewable energy systems. In particular, but not exclusively, the present invention relates to systems for harnessing tidal energy.

Known renewable energy systems include devices for capturing solar, wind, wave, and tidal power. Growth in the use of renewable energy is constrained only by the ability to produce and deliver it at an economic price. The majority of renewable energy devices relate solely to wind and solar power generation, and do not address renewable energy produced from water.

Ocean and tidal currents are capable of providing a virtually inexhaustible supply of emission-free renewable energy. Since ocean and tidal currents exist everywhere in the world, converting the energy in these currents to electricity could provide a predictable and reliable supply of electricity to the electric power systems in many parts of the world. Since some seventy percent of the world’s population lives within about 200 miles of an ocean, ocean current energy and ocean tidal energy could become a vital part of the world’s energy future. There are also countless numbers of island communities where ocean currents accelerate around and between land masses. These coastal communities could easily benefit from the use of ocean power. With its vast and geographically dispersed resources, ocean current energy and its associated tidal energy have the potential of becoming the next “wind” of renewable energy.

Numerous schemes for harnessing tidal power have been developed over the years. Tidal power devices offer advantages over wave power devices. Tides are regular and predictable, whereas wave power depends essentially upon weather conditions. Another advantage of tidal power devices is the fact that less complex structures can be employed at coastal sites, because locations for tidal devices are generally exposed to less extreme weather so that the devices do not have to be constructed to the same level of survivability as ocean wave power devices.

In the past, schemes for harnessing water energy have typically involved water storage systems such as dams, levies, basins, wells and reservoirs. However, these storage systems are not sufficient to meet the ever-increasing needs of the world’s population and meeting future needs is problematic. Other previously attempted solutions for water based renewable energy systems have included systems for distributing water between reservoirs. One example is the Blenheim-Gilboa pumped storage power project located in the Catskill Mountain region of the United States. This system uses a reservoir system capable of generating electricity in peak demand periods by recycling water between two large reservoirs, one of which is at a foot of a mountain and the other is at the top of the mountain.

Many known tidal energy systems require many of the components of the system to be located in sea water. The corrosive salt water causes degradation of the equipment used. The components must be specially adapted to be corrosion resistant and so cannot be standard components.

It is desirable to provide improved tidal energy systems.

The most common water turbine in use today is the Francis turbine. This is an inwardflow reaction turbine in which the working fluid horizontally enters the turbine under great pressure and energy is extracted by the turbine blades from the working fluid. Part of the energy given up by the fluid is because of pressure changes occurring in the blades while the remaining part of the energy is extracted by the spiral casing of the turbine. At the exit, water acts on the spinning cup-shaped runner features, leaving at low velocity and low swirl with very little kinetic or potential energy left. The turbine's exit tube is shaped to help decelerate the water flow and recover the pressure.

Another known turbine is the Kaplan turbine which is a propeller-type water turbine with adjustable blades. This turbine allows efficient power production in low-head applications not possible with Francis turbines. The Kaplan turbine is an outward flow reaction turbine. Power is recovered from both the hydrostatic head and from the kinetic energy of the flowing water. Water is directed tangentially and spirals on to a propeller shaped runner, causing it to spin. The outlet is a specially shaped draft tube that helps decelerate the water and recover kinetic energy. The variable geometry of the blades allows efficient operation for a range of flow conditions.

According to the present invention there is provided a tidal energy capturing system comprising:

a lower level storage reservoir located at a first height above sea level;

an upper level storage reservoir located at a second greater height above sea level;

a first turbine device having first turbine blades and a first output shaft and located at or around sea level in a moving body of water, wherein the first turbine device is adapted to be acted upon by movement of the body of water to cause rotation of the first turbine blades and first output shaft;

a first pump device coupled to the output shaft and adapted to pump water from the lower level storage reservoir to the upper level storage reservoir;

a second turbine device having second turbine blades and a second output shaft and located between the lower and upper level storage reservoirs, wherein the second turbine device is adapted to be acted upon by the flow of water from the higher level storage reservoir to the lower level storage reservoir to cause rotation of the second turbine blades and second output shaft.

Optionally, the moving body of water is a tidal body of water. Alternatively or in addition, movement of the body of water is due to current flow and/or waves.

Optionally, the system includes a barrier member located at or around sea level in the body of water, the barrier member dividing the body of water into a first and a second volume of water. Optionally, the first turbine device is provided at the barrier member.

Optionally, the barrier member includes a first conduit arrangement which fluidly connects the first and second volumes of water. Optionally, the first turbine device is provided within the first conduit arrangement.

Optionally, the first conduit arrangement is adapted to provide a first flow path from the first to the second volume of water. Optionally, the first conduit arrangement is adapted to provide a second flow path from the second to the first volume of water. Optionally, the barrier member includes at least one check valve for providing the first and second flow paths.

Optionally, the barrier member includes a plurality of first conduit arrangements and a first turbine device is provided in each first conduit arrangement.

Optionally, the or each first turbine device is a Kaplan turbine.

Optionally, the first pump device is coupled to the first output shaft via a second pump device. Optionally, the second pump device is adapted to pump a hydraulic fluid via a second conduit to a hydraulic motor. Optionally, the hydraulic motor is adapted to operate the first pump device. Optionally, the second pump device is a hydraulic pump.

Optionally, the system includes a plurality of second pumps. Optionally, a second pump is connected to each first turbine device. Optionally, the or each second pump is contained within a sealed chamber provided at each first conduit arrangement.

Optionally, only the input shaft of the or each second pump extends from the chamber. Optionally, the second conduit includes a manifold portion for fluidly connecting to a plurality of second pumps. Optionally, the manifold portion fluidly connects the plurality of second pumps to a single hydraulic motor.

Optionally, the lower and the upper level storage reservoirs each comprise fresh water. Optionally, the first pump device is adapted to pump fresh water from the lower to the upper level storage reservoir.

Optionally, at least one of the hydraulic motor and the second pump device are adapted to change the rotation speed of the first pump device relative to the first turbine device. Optionally, at least one of the hydraulic motor and the second pump device are adapted to increase the rotation speed of the first pump device relative to the first turbine device.

Optionally, the second turbine device comprises a Francis turbine. Optionally, the output shaft of the second turbine device is coupled to electricity generating apparatus.

The invention will be described below, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is schematic view of a system in accordance with the invention;

Figure 2 is a plan view of a turbine, barrier, and conduit arrangement of the system of Figure 1; and

Figure 3 is a schematic side view of the system of Figure 1.

Figures 1 and 3 show a tidal energy capturing system 10 comprising a lower level storage reservoir or lake 12 and an upper level storage reservoir or lake 14. These lakes could be artificial or they could be natural lakes selected for their proximity and suitable vertical elevations. Both of the lakes are located at a body of land which is near to a tidal body of water such as an ocean or sea 16. Both lakes comprise fresh water.

As an example, the lower lake 12 could be 20 vertical meters above sea level 100 and the upper lake 14 could be 300 vertical meters above the lower lake 12. The land and sea 16 may define an estuary 18.

The first pump 32 pumps water from the lower lake 12 up to the upper lake 14 via a pump discharge pipe 34.

The system includes a barrier in the form of a dyke 20 located in the sea 16. The dyke 20 divides the sea 16 into a first volume of water (within the estuary 18) and a second volume of water (the main body of the sea 16).

At regular intervals along the dyke 20, the dyke 20 includes a tunnel arrangement 22 fluidly connecting the two volumes of water. As shown in Figure 2, the tunnel arrangement 22 comprises a first conduit arrangement 24, a gate 29 and four check valves 25 which define two flow paths.

The first conduit arrangement 24 provides a first flow path 26 from the sea 16 to the estuary 18. When the tide is coming in, the sea water can only take this flow path 26 due to the checkvalves 25 and gate 29. The first conduit arrangement 24 also provides a second flow path 28 from the estuary 18 to the sea 16 and, when the tide is going out, the sea water takes this flow path 28.

The inlets of the tunnel arrangement 22 on the ocean side are each protected by a barricade island 27 which is positioned to dampen wave action in the tunnel which could impact the turbine assembly.

A first turbine device in the form of a Kaplan turbine 30 is provided at each tunnel arrangement 22. Water flowing along either the first or second flow paths acts upon blades of the Kaplan turbine 30 causing rotation of the blades and of an output shaft coupled to the blades. The first conduit arrangement 24 and checkvalves 25 ensure that the blades and output shaft rotate in the same direction regardless of whether the tide is coming in or going out. Each Kaplan turbine 30 and its component parts can be constructed largely of light weight, corrosion resistant materials, such as aluminium and fiberglass.

The output shaft of each Kaplan turbine 30 is connected to a second pump 42 such that the Kaplan turbine 30 drives the second pump 42. Each second pump 42 is a hydraulic pump provided in a sealed chamber 31 within the dyke 20. Only a portion of the shaft of each second pump 42 is exposed to sea water. It should be noted that, for the system as a whole, only the Kaplan turbine 30 is exposed to sea water. Therefore, only this component needs to be specially adapted such that it is corrosion resistant.

A manifold (not shown) fluidly connects the output from each second pump 42 to a single hydraulic motor 46 via a second conduit 44.

The first pump 32 is (indirectly) coupled to the Kaplan turbines 30 by a second pump in the form of a hydraulic pump 42 which pumps a hydraulic fluid to the hydraulic motor 46. The high pressure hydraulic fluid operates the hydraulic motor 46 which is used to operate the first pump 32.

Water in the upper lake 14 can naturally flow down due to gravity to the lower lake 12 via a drainage conduit or penstock 36. A movable gate (not shown) either allows or blocks this flow so that the flow is selectable and controllable.

A second turbine device in the form of a Francis turbine 40 is provided at the penstock 36. When the gate is open, the Francis turbine 40 is acted upon by the flow of water from the upper lake 14 to the lower lake 12 and this causes rotation of the second blades and, consequently, output shaft of the Francis turbine 40.

Therefore, tidal movement causes rotation of the output shafts of the Kaplan turbines 30 which in turn causes operation of each second pump 42. This operates the hydraulic motor 46 which causes the first pump 32 to transfer fresh water from the lower lake 12 to the upper lake 14. Water returning to the lower lake 12 from the upper lake 14 causes rotation of the output shaft of the Francis turbine 40. The output of the Francis turbine 40 can be coupled to an electrical generator device (not shown). An energy generating cycle can be maintained continuously.

The hydraulic motor 46 and the hydraulic pump 42 are configured so that they increase the rotation speed of the first pump 32 relative to the Kaplan turbines 30. Typically, the hydraulic pump 42 and hydraulic motor 46 may convert the output turbine shaft rotation speed of 450 RPM to 1800 RPM of the first pump 32 by varying the fluid displacement of the hydraulic pump and motor. The hydraulic fluid compressed to high pressure creates heat, approx. 300 °F to 400°F. This heat can be extracted for additional uses.

As an example of the system, a candidate site was selected at Big Water of Fleet Bay on the West Coast of Scotland. The following is a hypothetical example of the design criteria used in adapting the renewable energy system of the invention to such a candidate location. This site has an average predicted tide of 7 meters.

Assume that for a pilot project that:

Two (2) tides per 24 hours-every day, day or night, rain or shine

Four (4) flows per 24 hours

Two (2) flows into estuary

Two (2) flows out of estuary

Six (6) hours per flow to fill on empty estuary

From these assumptions, one can calculate:

Area of estuary 8,623,480 square meters

Height of tide 7m.

8,623,480m2 x 7m = 60,364,360m3

60,364,360m3 4- (6hrs x 60min/sec x 60sec/min) = 2,795m3/sec Avg. flow in and out of the estuary every 6 hours

2,795m3/sec 4- 46 Kaplan turbine units = 60.76m3/sec

2,795m3/sec - 35m3/sec (bypass) = 2,760m3/sec

Area of 3.12 meter dia. pipe = 7.65m2

V=Q/A= 60m3/sec 4- 7.65m2 = 7.84 m/sec

60m3/sec x 46 Kaplan turbine units = 2,760m3/sec .76m3/sec x 46 Kaplan turbine units = 35m3/sec (bypass flow rate)

35m3/sec 4- 7.65m3 =4.58 m/sec = 3.12m dia bypass pipe

Kaplan Turbine Power

P(watts) = nx qxp xgxh

P(watts) = .92 x l,028kg/m3 x 2,760m3/sec x 9.81m/sec2 x 7m = 179,249,136w 179,249,136w 4- 745.7 watts/hp x 46units = 5,226hp total turbine power 5,226hp total hydraulic pump power

Rotation of turbine = 450rpm = rotation of hydraulic pump

Hydraulic fluid pump = 5,226hp at 450rpm at 1500psi

P = 5,226hp n = .92 eff.

g = gpm p = l,500psi

p.d. = pump displacement

5,226hp = gpm x l,500psi x .0007

5,226hp 4-(1,500psi x .0007)= gpm = 4,977gpm

Gpm= (rpm x p.d.)4-231

4,977gpm = (450rpm x p.d.) 4-231 (4,977gpm x 231) 4- (450rpm x 46units) = p.d. = 55.54gal.

Motor input 4579gpm at 1,500 psi at l,800rpm (4,977gpm x 231) 4- (l,800rpm x 46units) = 13.89gal.

Pumping Capacity of First Pump

P(watts) = nxqxpxgxh

P(watts) = .82 x 4,977hp x 745.7kw/hp = 3,711,349w

P(watts) = 3,043,306w q = m3/sec p = l,000kg/m3 g = 9.81m/sec2 h = 300m n = .82 eff.

3,043,306w = q x 1000kg/m3 x 9.81m/sec2 x 300m q = 1.034m3/sec x 46units = 47.57m3/sec total pumping

Generating Capacity

P(watts) = nx qxp xgxh q = 47.57m3/sec p = l,000kg/m3 g = 9.81m/sec2 h = 300m n = .92 eff.

P(watts) = .92 x 47.57m3/sec x l,000kg/m3 x 9.81m/sec2 x 300m

P(watts) = 128.799mw

The plant capacity is also enhanced by natural rainfall which occurs. For the same site:

TABLE 1

Rain Fall Chart

Jan = 16 cm

Feb = 13 cm

Mar = 15 cm

Apr = 10 cm

May = 10 cm

Jun = 10 cm

Jul = 10 cm

Aug =11 cm

Sep = 13 cm

Oct= 16 cm

Nov = 15 cm

Dec = 16 cm

Total = 1.55m

Upper Lake Catchment

Lake = 134,823m2

1.55m rain fall per year in lake = 208,976m3 (208,976m3) 4- (365 days/yrj (12 hrs/dayj (60 min/hrj (60 min/sec) = 0.013m3/sec Add 0.013m3/sec to outflow of tide 2 times per day or 12 hours

Flow of Waters of Fleet

Flow of Waters of Fleet = 3.553m3/sec add to outflow of tide 2 times per day or 12 hours.

0.013m3/sec + 3.553m3/sec = 3.566m3/sec

P(watts) = .92 x 1028kg/m3 x 3.566m3/sec x 9.81m/sec2 x 7m

P(watts) = 231,595w

Pumping Capacity

P(watts) = 231,595w x .82

P(watts) = 189,909w

189,909w = q x l,000kg/m3 x 9.81m/sec2 x 300m q = .065m3/sec

Generation Capacity

P(watts) = .92 x 0.065m3/sec x l,000kg/m3 x 9.81m/sec2 x 300m

P (watts) = .178mw

Total Generation Capacity

128.799mw + .178mw = 128.98mw

The present invention provides many advantages. The renewable energy system of the invention can be used to supply a predictable and reliable source of electricity to the national grid. The system is relatively simple in design and dependable in operation. The system is also relatively non-polluting as compared to other alternative energy sources. The tidal energy source is more reliable than wave powered systems since it does not depend as heavily upon current weather conditions. Because the system is located in an estuary or other relatively sheltered location, the component parts can be made of lighter weight and non-corrosive materials than many of the prior art systems.

While the invention has been shown in one of its forms, it is not thus limited and susceptible to various changes and modifications without departing from the spirit thereof.

While the system has been illustrated in its simplest form, it will be appreciated the principal components can be doubled or tripled, etc. depending upon the amount of tidal flow, and other factors.

Various modifications and improvements can be made to the above without departing from the scope of the invention.

Claims

1. A tidal energy capturing system comprising:

a lower level storage reservoir located at a first height above sea level;

a second turbine device having second turbine blades and a second output shaft and located between the lower and upper level second storage reservoirs, wherein the second turbine device is adapted to be acted upon by the flow of water from the higher level storage reservoir to the lower level storage reservoir to cause rotation of the second turbine blades and second output shaft.

2. A system according to claim 1, wherein the moving body of water is a tidal body of water.

3. A system according to claim 1 or 2, wherein the system includes a barrier member located at or around sea level in the body of water, the barrier member dividing the body of water into a first and a second volume of water.

4. A system according to any preceding claim, wherein the first turbine device is provided at the barrier member.

5. A system according to claim 3, wherein the barrier member includes a first conduit arrangement which fluidly connects the first and second volumes of water, and wherein the first turbine device is provided within the first conduit arrangement.

6. A system according to claim 5, wherein the first conduit arrangement is adapted to provide a first flow path from the first to the second volume of water.

7. A system according to claim 6, wherein, the first conduit arrangement is adapted to provide a second flow path from the second to the first volume of water.

8. A system according to claim 7, wherein the barrier member includes at least one checkvalve for providing the first and second flow paths.

9. A system according to any of claims 5 to 8, wherein the barrier member includes a plurality of first conduit arrangements and a first turbine device is provided in each first conduit arrangement.

10. A system according to any preceding claim, wherein the or each first turbine device is a Kaplan turbine.

11. A system according to any preceding claim, wherein the first pump device is coupled to the first output shaft via a second pump device.

12. A system according to claim 11, wherein the second pump device is adapted to pump a hydraulic fluid via a second conduit to a hydraulic motor, and wherein the hydraulic motor is adapted to operate the first pump device.

13. A system according to claim 11 or 12, wherein the second pump device is a hydraulic pump.

14. A system according to any of claims 11 to 13, including a plurality of second pumps, and wherein a second pump is connected to each first turbine device.

15. A system according to claim 14, wherein the or each second pump is contained within a sealed chamber provided at each first conduit arrangement.

16. A system according to claim 15, wherein only the input shaft of the or each second pump extends from the chamber.

17. A system according to any preceding claim, wherein the lower and the upper level storage reservoirs each comprise fresh water, and wherein the first pump device is adapted to pump fresh water from the lower to the upper level storage reservoir.

18. A system according to claim 12, wherein at least one of the hydraulic motor and the second pump device are adapted to increase the rotation speed of the first pump device relative to the first turbine device.

19. A system according to any preceding claim, wherein the second turbine device comprises a Francis turbine.

20. A system according to any preceding claim, wherein the output shaft of the second turbine device is coupled to electricity generating apparatus.