GB2615995A

GB2615995A - A tidal energy converter

Info

Publication number: GB2615995A
Application number: GB2201153.0A
Authority: GB
Inventors: Burn Michael
Original assignee: Tidalgen Ltd
Current assignee: Tidalgen Ltd
Priority date: 2022-01-28
Filing date: 2022-01-28
Publication date: 2023-08-30
Also published as: GB202201153D0

Abstract

A tidal energy converter comprises a rotor 100 with a plurality of chambers 120, 122, 124, 126 and a plurality of blades 130 132 134 136, wherein each blade can pivot between a closed position and an open position. In the open position the blade 130, 136 extends outwards away from the rotor body, and in the closed position the blade 132, 134 partially closes the corresponding chamber, leaving a gap between the blade and a wall 160, 162, 164, 166 of the corresponding chamber that enables water to flow into the corresponding chamber. The blades may comprise first and second 145, 175 parts pivotally connected together, and the second part may be able to pivot inwards so that the end of the second part is within the chamber.

Description

TITLE

A TIDAL ENERGY CONVERTER

FIELD OF THE INVENTION

Embodiments of the present invention relate to a tidal energy converter. In particular, they relate to a tidal energy converter in the renewable energy industry.

BACKGROUND TO THE INVENTION

Existing methods used or proposed for gathering energy from flows of water focus on gathering energy from fast moving water, typically in rivers and tide-races and are provided in various forms including Archimedean screws, turbines, etc.

BRIEF DESCRIPTION OF VARIOUS EMBODIMENTS OF THE INVENTION

According to various, but not necessarily all, embodiments of the invention there is provided a tidal energy converter, comprising: a rotor comprising: a rotor body comprising a plurality of chambers; a plurality of blades, each blade being associated with a corresponding chamber from the plurality of chambers, wherein each blade can pivot between a closed position and an open position; where in the open position the blade extends outwards away from the rotor body; where in the closed position the blade partially closes the corresponding chamber, leaving a gap between the blade and a wall of the corresponding 30 chamber that enables water to flow into the corresponding chamber.

In some, but not necessarily all, examples, each blade comprises: a first part connected to the rotor body, wherein the first part can pivot relative to the rotor body; a second part connected to the first part, wherein the second part can pivot relative to the first part.

In some, but not necessarily all, examples, in the closed position the second part has inwardly pivotally rotated relative to the first part so that the end of the second part is within the chamber.

In some, but not necessarily all, examples, the tidal energy converter comprises stopping means for preventing further inward pivotal rotation of the second part relative to the first part.

In some, but not necessarily all, examples, the length of the first part is greater than the length of the chamber.

In some, but not necessarily all, examples, the length of the second part is less than the length of the chamber.

In some, but not necessarily all, examples, in the closed position the first part lies against the rotor body.

In some, but not necessarily all, examples, when the first part lies against the rotor body the second part can inwardly pivotally rotate relative to the first part within the chamber.

In some, but not necessarily all, examples, the rotor body comprises: a circular top: a circular bottom; a plurality of walls.

In some, but not necessarily all, examples, each chamber is formed by part of the circular top, part of the circular bottom, two of the plurality of walls and the blade that corresponds with the chamber.

In some, but not necessarily all, examples, the rotor comprises: four walls, four blades, four chambers.

In some, but not necessarily all, examples, the four walls form a cross shape in cross-section.

In some, but not necessarily all, examples, the first part of the blade is curved to match the curvature of the circular top and the circular bottom.

In some, but not necessarily all, examples, the first part of the blade lies against the circular top and the circular bottom in the closed position.

In some, but not necessarily all, examples, the tidal energy converter is configured so that in the open position the first part is prevented from pivotally rotating further in the direction away from the closed position.

In some, but not necessarily all, examples, the tidal energy converter comprises a second such rotor.

In some, but not necessarily all, examples, the rotor and the second rotor are arranged side-by-side.

In some, but not necessarily all, examples, the rotor and the second rotor have outputs linked by linking means and are orientated to rotate in the same direction and provide a single, common output for an electric generator.

In some, but not necessarily all, examples, the rotor and the second rotor are arranged so that as the blades of one of the rotors rotate in the open position, the wash of water from the blades can feed into one or more of the gaps of the other rotor.

In some, but not necessarily all, examples, the rotor and the second rotor are 5 arranged so that the wash of water from the blades of one of the rotors can provide a pushing force to push the blades of the other rotor towards the closed position as the rotors rotate.

In some, but not necessarily all, examples, the tidal energy converter comprises an electric generator, coupled to an output of the rotor.

In some, but not necessarily all, examples, the tidal energy converter comprises an electric generator, coupled to the common output.

In some, but not necessarily all, examples, the tidal energy converter comprises a plurality of such rotors, arranged in an array.

In some, but not necessarily all, examples, the rotors are coupled in pairs, each pair linked to a corresponding single common output.

In some, but not necessarily all, examples, the rotor, or rotors, when mounted in a seabed, river bed or other bed that has a tidal stream, can rotate in the same direction for an incoming tidal stream and an outgoing tidal stream.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of various examples of embodiments of the present invention reference will now be made by way of example only to the accompanying drawings in which: FIG. 1 shows an example of the subject matter described herein; FIG. 2 shows another example of the subject matter described herein;

FIG FIG FIG FIG

FIG

FIG 3 shows another example of the 4 shows another example of the shows another example of the 6 shows another example of the 7 shows another example of the 8 shows another example of the subject matter described herein; subject matter described herein; subject matter described herein; subject matter described herein; subject matter described herein; subject matter described herein.

DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS OF THE INVENTION

The Figures illustrate a tidal energy converter 100, comprising: a rotor 110 comprising: a rotor body 111 comprising a plurality of chambers 120, 122, 124, 126; a plurality of blades 130, 132, 134, 136, each blade being associated with a corresponding chamber from the plurality of chambers, wherein each blade can pivot between a closed position 140 and an open position 145; where in the open position 145 the blade extends outwards away from the rotor body 111; where in the closed position 140 the blade partially closes the corresponding chamber, leaving a gap 150 between the blade and a wall 160, 162, 164, 166 of the corresponding chamber that enables water to flow into the corresponding chamber.

Fig. 1 illustrates an example tidal energy converter 100. In this example the tidal energy converter 100 comprises a rotor 110. The rotor body 111 comprises a plurality of chambers 120, 122, 124, 126. The rotor 110 also comprises a plurality of blades 130, 132, 134, 136. Each of the blades, 130, 132, 134, 136 are associated with a corresponding chamber from the plurality of chambers 120, 122, 124, 126. Each blade 130, 132, 134, 136 can pivot between a closed position 140 and an open position 145.

In Fig.1, blade 130 and blade 132 are illustrated. Blade 130 is in the open position 145. In the open position the blade extends outwards away from the rotor body 111 Blade 132 is in the closed position 140. In the closed position 140 the blade partially closes the corresponding chamber 122, leaving a gap 150 between the blade 132 and a wall 164 of the corresponding chamber 122. The gap 150 enables water to flow into the corresponding chamber 122.

In the example of Fig.1, chamber 120 corresponds with blade 130. In Fig. 1, chamber 120 is open and is visible. Chamber 122 is associated with blade 132. In the example of Fig. 1 chamber 122 has been partially closed and in Fig. 1 only part of the chamber 122 is visible.

In Fig. 1, blade 134 is partially visible, but is mainly blocked from view by the rotor body 111 from the viewpoint in Fig. 1.

In this example each blade 130, 132, 134, 136 comprises: a first part 170 connected to the rotor body 111. The first part 170 can pivot relative to the rotor body 111. Each blade 130, 132, 134, 136 also comprises a second part 175 connected to the first part 170. The second part 175 can pivot relative to the first part 170.

As illustrated in Fig. 1, both the first part 170 and the second part 175 of blade 130 are extending outwards away from the rotor body 111. The blade 132 in the closed position 140 has the second part 175 inwardly pivotally rotated relative to the first part 170 so that the end of the second part 175 is within the chamber 122.

In this example the tidal energy converter 100 also comprises stopping means for preventing further inward pivotal rotation of the second part 175 relative to the first part 170 when the blade is in the closed position 140. In this example the stopping means 180 comprises a barrier as illustrated in Fig.1. The barrier is provided within the chamber 120 and protrudes upwards from the bottom surface of the chamber 120 so that it can abut the second part 175 when the blade 130 is in the closed position 145. Stopping means 180 can be provided in each chamber 120, 122, 124, 126. The stopping means 180 can therefore maintain the size of the gap 150 when the blade 130, 132, 134 and 136 is in the closed position 140.

In other examples the stopping means 180 can be any alternative structure or mechanism for preventing further inward pivotal rotation of the second part 175 relative to the first part 170 when in the closed position 140. For example, if the second part 175 pivots via hinges, the hinges may be configured to stop at a certain position. In another example, the stopping means 180 may comprise alternative or additional barriers provided within the chambers 120, 122, 124, 126.

In the example of Fig.1, the length of the first parts 170 of the blades 130, 132, 134, 136 is greater than the length of the chamber 120, 122, 124, 126.

This means that the first part 170 of the blades 130, 132, 134, 136 are prevented from entering the corresponding chamber. In this example in the closed position 140 the first part 170 of each blade lies against the rotor body 111.

The length of the second part 175 of each blade 130, 132, 134, 136 is less than the length of the chamber 120, 122, 124, 126 so that it can inwardly pivotally rotate relative to the first part 170 within the chamber.

Therefore, in this example when the first part 170 lies against the rotor body 111, the second part 175 can pivotally inwardly rotates relative to the first part 170 within the chamber 120, 122, 124, 126.

In the example of Fig.1, the rotor body 111 comprises a circular top 190, a circular bottom 195 and a plurality of walls 160, 162, 164, 166.

In the example of Fig. 1 each chamber 120, 122, 124, 126 is formed by part of the circular top 190, part of the circular bottom 195 and two of the plurality of walls, 160, 162, 164, 166 and also the blade 130, 132, 134, 136 that corresponds with the chamber.

In the example of Fig. 1 the rotor 110 comprises four walls 160, 162, 164, 166, four blades, 130, 132, 134, 136 and four chambers 120, 122, 124, 126.

In the example of Fig. 1, the blades pivot using hinges. For example blade 130 has hinges 1301, 1302, 1303 and 1304. In this example, the first part 170 is connected to the rotor body 111 via the hinges 1301, 1303. The second part 175 is connected to the first part 170 via the hinges 1302, 1304.

Fig. 2 illustrates an example tidal energy converter 100. In Fig. 2, the tidal energy converter 100 is viewed from above and in cross section. In Fig. 2 each of the chambers 120, 122, 124, 126, the blades 130, 132, 134, 136 and walls 160, 162, 164, 166 are visible.

In this example, the four walls 160, 162, 164, 166 form a cross shape in cross 20 section.

Fig. 2 illustrates an example direction of a tidal flow 200 relative to the energy tidal energy converter 100. Due to the tidal flow 200, each of the blades 130, 132, 134, 136 is in a different position. Blade 130 is in the open position 145, with its interior surface 210 facing the tidal flow 200. Due to the force of the water impacting the blade 130, this imparts a force on the rotor 110. The rotor 110 in this example is mounted on an axle 240. The axle 240 runs in the direction of the length of the blades 130, 132, 134, 136. Due to the force on the blade 130 from the tidal flow 200, the rotor can rotate in the direction illustrated by arrows 250, 255.

In this example the blade 130 in the open position is prevented from pivotally rotating further in the direction from the closed position 140. This is because the first part 170 of the blade 130 is prevented from pivotally rotating further. For example, stoppers 230 protrude from the back surface 220 of the blades 130, 132, 134, 136 and apply a force to the corresponding wall 160, 162, 164, 166 which prevent further pivotal movement of the first part 170. In other examples, the hinges of the pivot between the first part 170 and the rotor body 111 are configured to stop at the open position 145 and prevent further pivotal movement away from the closed position 140.

In Fig. 2, blade 136 is in a position between the open position 145 and the closed position 140. The blade 136 has started to move back in the direction towards the closed position 140 due to not directly facing the tidal flow 200 and also due to the force on the back surface 220 due to rotation of the rotor 110 through water, causing pivotal rotation of the first part 170 relative to the rotor body 111 in the direction towards the closed position 140.

Blade 134 is shown in a position which has rotated further towards the closed position 140. The blade 134 has moved closer towards the closed position 140 due to the force of the tidal flow 200 on the back surface 220 of the blade 134 and also due to the rotation of the rotor 110. The first part 170 of blade 134 is close to/is lying against the rotor body 111 and the second part 175 has inwardly pivotally rotated relative to the first part 170 Blade 132 is shown in the closed position 140.

As illustrated in Fig. 2, the blade 132 in the closed position 140 provides a gap 150 which enables water to flow into the chamber 122. In this example the force of the tidal flow 200 and the rotation of the rotor 110 has put the blade 132 into the closed position 140 including causing the second part 175 to inwardly pivotally rotate relative to the first part 170 and in this example is prevented from further inward pivotal rotation by stopping means 180.

As the rotor 110 continues to rotate the gap 150 will become more exposed to the tidal flow 200 causing water to flow into the chamber 122. This causes water pressure to increase on the interior surface 210 of the blade 132 which, as the rotor 110 continues to rotate, will help the blade 132 to move from the closed position 140 towards the open position 145, which will lead to the interior surface 210 of the blade 132 facing the tidal flow 200.

As illustrated in Fig. 1 and Fig. 2, the first part 170 of the blades 130, 132, 134, 136 is curved to match the curvature of the circular top 190 and the circular bottom 195. In the closed position 140, the first pad 170 of the blades 130, 132, 134, 136 lies against the circular top 190 and the circular bottom 195.

Fig. 3 illustrates another example tidal energy converter 100. In this example, the tidal energy converter 100 comprises a second such rotor 300 that is as described above in Fig. 1 and Fig. 2. The rotor 110 and the second rotor 300 are arranged side by side. A tidal flow 310 and its direction are represented by arrows. Due to the tidal flow 310, the rotors 110, 300 rotate in the direction illustrated by arrows 320, 330, 340, 350.

In the example of Fig. 3 the tidal energy converter 100 is illustrated in cross-section from above.

Each rotor 110, 300 can rotate with the blades 130, 132, 134, 136 moving pivotally. The rotors 110, 300 are arranged so that as the blades 130, 132, 134, 136 of one of the rotors 110, 300 rotates the wash of water from the blades 130, 132, 134, 136 of that rotor 110, 300 can feed into one or more of the gaps 150 of the other rotor 110, 300. In this example, the wash of water from the blades 130, 132, 134, 136 of the second rotor 300 can feed into the gaps 150 of the blades 130, 132, 134, 136 on the first rotor 110. For example in the positions the rotors 110, 300 are in within Fig. 3, the wash from blade on the rotor 300 can feed into the gap 150 associated with blade 132 on the rotor 110, and can continue to do so as both rotors 110, 300 rotate. As the rotors 110, 300 rotate the wash of the other blades 132, 134, 136 of the rotor 300 will feed into the gaps 150 associated with the other blades 130, 134, 136.

In this example the rotor 110 and the second rotor 300 are arranged so that the wash of water of the blades 130, 132, 134, 136 of one of the rotors 110, 300 can provide a pushing force to push the blades 130, 132, 134, 136 of the other rotor 110, 300 towards the closed position 140 as the rotors rotate. For example, as illustrated in Fig. 3, as the blade 130 of the second rotor 300 continues to rotate its wash will impact against the back surface 220 of blade 136 of the first rotor 110 as it continues to rotate, which can push the blade 136 of the rotor 110 further to the closed position 140.

Fig. 4 illustrates, schematically, an example tidal energy converter 100 from a side view. In this example, the tidal energy converter 100 comprises two rotors 110, 300 as described above. In this example, the rotor 110 and the second rotor 300 have outputs 400, 410, from each of their axles 240, linked by linking means 420 and are orientated to rotate in the same direction as illustrated in Fig. 3 and provide a single, common output 430 for an electric generator. For example, the linking means 420 may be a chain and the output 400, 410 are rotary outputs of the rotor 110 and the second rotor 300. Sprockets can be provided on the rotary outputs 410, 430 which connect to the linking means 420. As both the outputs are linked by the chain 420, a common output 430 can be provided as a rotary input to an electric generator.

In this example the output 400 is part of the common output 430. In other examples, the common output 430 may be provided by a separate spindle and sprocket connected to the outputs 400, 410 by linking means 420 or additional linking means between one of the outputs 400, 410 and the common output 430.

In some examples gearing can be provided between the outputs 400, 410 which causes the common output 430 to rotate at a different speed to the outputs 400, 410. For example, gearing may be provided so that the common output 430 rotates at a higher speed compared to the outputs 400, 410.

Fig. 5 illustrates an example tidal energy converter 100. In this example, the tidal energy converter comprises an electric generator 500 coupled to an output 510 of the rotor 110. In this example, the electric generator 500 is coupled directly to the output 510 of the rotor 110. In other examples, the electric generator 500 may be coupled to the output 510 via linkage means and/or gearing.

Fig. 6 illustrates, schematically, an example tidal energy converter 100. In this example, tidal energy converter 100 comprises a rotor 110, a second rotor 300, where the outputs 400, 410 of the rotor 110 and the second rotor 300 are linked by linking means 420 and provide the single common output 430 for an electric generator as described in Fig. 4. The tidal energy converter 100 in this example additionally comprises an electric generator 500 which is coupled to the single common output 430. In other examples, the electric generator 500 may be coupled to the common output 430 via linkage means and/or gearing.

Fig. 7 illustrates an example tidal energy converter 100. In this example, the tidal energy converter 100 comprises a plurality of such rotors 110, 300, 710, 720, 730, 740 as described above, arranged in an array 700. In this example the rotors are coupled in pairs, each pair linked to a corresponding single common output as described above in Fig. 4 and Fig. 6. Alternatively, each rotor in the array can provide an output to a separate electric generator. The rotors in the array can be arranged so that as the blades 130, 132, 134, 136 of the rotors 110, 300 rotate the wash of water from the blades 130, 132, 134, 136 of that rotor 110, 300 can feed into one or more of the gaps 150 of an adjacent rotor. In the example of Fig. 7, if the tidal flow is in the direction of into the page, the adjacent rotor is on the left. Therefore rotors along the array can feed the wash from the blades to the rotor on their left. Similarly, the rotors are arranged so that the wash of water of the blades 130, 132, 134, 136 of the rotors can provide a pushing force to push the blades 130, 132, 134, 136 of an adjacent rotor towards the closed position 140 as the rotors rotate.

Fig. 8 illustrates an example tidal energy converter 100 comprising a rotor 110 and a second rotor 300 as described above. In this example the tidal energy converter 100 also comprises a mounting 800. The axles 240 of the rotors are mounted at one end to the mounting 800 and at the other end pass through the mounting to provide the outputs 410, 420. The mounting 800 may be provided to mount the rotors to a sea bed, or other bed that has a tidal stream. Other forms of mounting are possible, for example the mounting may be a base provided in or on the bed for each rotor.

In the examples illustrated the rotary output of the rotor or rotors 110, 300, 710, 720, 730, 740 can be used to provide a rotary input to an electrical generator to generate electric power.

In the examples illustrated the rotor 110 or rotors 100, 300, 710, 720, 730, 740 can be mounted to a sea bed, river bed, or other bed that has a tidal stream and can rotate in the same direction for both an incoming tidal stream and an outgoing tidal stream.

For example, the rotor 100 in Fig. 2 will rotate in the same direction illustrated by arrows 250, 255 when the tidal flow is in the opposite direction to the tidal flow 200 direction shown in Fig. 2. Similarly, in Fig. 3, the rotor 110 and the second rotor 300 will rotate in the direction illustrated by arrows 320, 330, 340, 350 when the tidal flow 300 is in the direction opposite to the direction illustrated in Fig. 3. In these examples the blades will open towards the open position 145 on the right hand side looking down from above and will move towards the closed position 140 on the left hand side, compared to being more open on the left hand side and more closed on the right hand side as illustrated in Fig. 2, Fig 3. This is achieved by the gaps 150 and the symmetrical nature of the tidal energy converter 100, so that the gaps can face the tidal flow which encourages the blades to move to the open position and the pivotal arrangement of the blades means that interior surface 210 of the blades is exposed to the tidal flow to cause a rotational force of the rotor and as the rotor rotates and the interior surface of the blades is less exposed to the tidal flow, the rotational force and the direction of the tidal flow will push against the back surface 220 of the blades causing them to close. This provides the advantage that the tidal energy converter 100 can operate reliably to produce energy whilst tide is flowing in and whilst tide is flowing out. The tidal energy converter can therefore be producing energy due to the movement of the tidal flow for all times except when there is slack water at the location of the tidal energy converter. By placing several tidal energy converters as described around the coast of a country, particular for a country that is an island, it can be possible to provide 24 hour energy generation if the high water time travels around the coastline of a country.

The example tidal energy converters 100 can be provided with a large size. For example the diameter of the circular top 190 and circular bottom 195 can be 30 feet and the height of the first part 170 of each blade can be 50 feet. This leads to generating energy by taking advantage of a high mass of moving water moving at a fairly low speed past the rotor or rotors. Tidal flows can be fairly slow moving and so the example tidal energy converters can take advantage of these slow moving currents compared to some existing water flow power generation machines which rely more on high speed water flow than high mass water flow.

Given the tidal energy converter 100 may be provided with large sizes and is to be fully submerged in water for its entire performance life, the tidal energy converter including the rotors and the blades can be made out of materials used for ship building. The working surfaces of the tidal energy converter 100 may be self-cleaning but it could also be possible to coat the tidal energy converter with coatings used for the bottom of large ships.

In other examples, it is also possible to provide the tidal energy converter at smaller scale.

The simplicity of this machine and natural robustness results in easy maintenance and therefore a long natural life.

The tidal energy converter 100 also requires no driven parts or any complex machinery which also leads to more longevity and better long term performance.

In the examples illustrated, the rotors are in the shape of cylinders. In other examples, the rotors are provided in a different shape.

In the examples illustrated, the rotors have four blades and four chambers. In other examples there may be more or less blades and more or less 20 chambers.

In the examples illustrated, the rotors are illustrated vertically, rotating about a vertical axis. The rotors can also operate as described when mounted horizontally, rotating about a horizontal axis. In some but not necessarily all embodiments, the rotors may be neutrally buoyant.

In the examples illustrated, the blades may be of a width (along the line of curvature) which is just shorter than a quarter of the circumference of the circular top 190 and circular bottom 195, to account for the width of the walls 160, 162, 164, 166. In other examples, the width of the blades may be shorter than this.

In some examples the width (along the line of curvature) of the first part 170 and the second part 175 of each blade is the same. In other examples the width of the first part 170 and second part 175 is different.

Although embodiments of the present invention have been described in the preceding paragraphs with reference to various examples, it should be appreciated that modifications to the examples given can be made without departing from the scope of the invention as claimed.

Features described in the preceding description may be used in combinations other than the combinations explicitly described.

Although functions have been described with reference to certain features, those functions may be performable by other features whether described or not.

Although features have been described with reference to certain embodiments, those features may also be present in other embodiments whether described or not.

Whilst endeavoring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.

I/we claim:

Claims

CLAIMS1. A tidal energy converter, comprising: a rotor comprising: a rotor body comprising a plurality of chambers; a plurality of blades, each blade being associated with a corresponding chamber from the plurality of chambers, wherein each blade can pivot between a closed position and an open position; where in the open position the blade extends outwards away from the rotor body; where in the closed position the blade partially closes the corresponding chamber, leaving a gap between the blade and a wall of the corresponding chamber that enables water to flow into the corresponding chamber.
2. A tidal energy converter as claimed in claim 1, wherein each blade comprises: a first part connected to the rotor body, wherein the first part can pivot relative to the rotor body; a second part connected to the first part, wherein the second part can pivot relative to the first part.
3. A tidal energy converter as claimed in claim 2, wherein in the closed position the second part has inwardly pivotally rotated relative to the first part so that the end of the second part is within the chamber.
4. A tidal energy converter as claimed in claim 3, wherein the tidal energy converter comprises stopping means for preventing further inward pivotal rotation of the second part relative to the first part.
5. A tidal energy converter as claimed in any of claims 2 to 4, wherein the length of the first part is greater than the length of the chamber.
6. A tidal energy converter as claimed in any of claims 2 to 5, wherein the length of the second part is less than the length of the chamber.
7. A tidal energy converter as claimed in claim 6, when dependent upon claim 5, wherein in the closed position the first part lies against the rotor body.
8. A tidal energy converter as claimed in any of claims 2 to 7, wherein when the first part lies against the rotor body the second part can inwardly pivotally rotate relative to the first part within the chamber.
9. A tidal energy converter as claimed in any preceding claim, wherein the rotor body comprises: a circular top: a circular bottom; a plurality of walls.
10. A tidal energy converter as claimed in claim 9, wherein each chamber is formed by part of the circular top, part of the circular bottom, two of the plurality of walls and the blade that corresponds with the chamber.
11. A tidal energy converter as claimed in any of claims 9 to 10, wherein the rotor comprises: four walls, four blades, four chambers.
12. A tidal energy converter as claimed in claim 11, wherein the four walls form a cross shape in cross-section.
13. A tidal energy converter as claimed in any of claims 9 to 12, wherein the first part of the blade is curved to match the curvature of the circular top and the circular bottom.
14. A tidal energy converter as claimed in any of claims 9 to 13, wherein the first part of the blade lies against the circular top and the circular bottom in the closed position.
15. A tidal energy converter as claimed in any preceding claim, wherein the tidal energy converter is configured so that in the open position the first part is prevented from pivotally rotating further in the direction away from the closed position.
16. A tidal energy converter as claimed in any preceding claim, comprising a second such rotor.
17. A tidal energy converter as claimed in claim 16, wherein the rotor and the second rotor are arranged side-by-side.
18. A tidal energy converter as clamed in claim 16 or 17, wherein the rotor and the second rotor have outputs linked by linking means and are orientated to rotate in the same direction and provide a single, common output for an electric generator.
19. A tidal energy converter as claimed in claim 18, wherein the rotor and the second rotor are arranged so that as the blades of one of the rotors rotate in the open position, the wash of water from the blades can feed into one or more of the gaps of the other rotor.
20. A tidal energy converter as claimed in claim 18 or 19, wherein the rotor and the second rotor are arranged so that the wash of water from the blades of one of the rotors can provide a pushing force to push the blades of the other rotor towards the closed position as the rotors rotate.
21. A tidal energy converter as claimed in any of claims 1 to 17, comprising an electric generator, coupled to an output of the rotor.
22. A tidal energy converter as claimed in any of claims 18 to 20, comprising an electric generator, coupled to the common output.
23. A tidal energy converter as claimed in any preceding claim, comprising a plurality of such rotors, arranged in an array.
24. A tidal energy converter as claimed in claim 23, wherein the rotors are coupled in pairs, each pair linked to a corresponding single common output.
25. A tidal energy converter as claimed in any preceding claim, wherein the rotor, or rotors, when mounted in a seabed, river bed or other bed that has a tidal stream, can rotate in the same direction for an incoming tidal stream and an outgoing tidal stream.