Upright tidal turbine assembly and gravity base for supporting upright tidal turbine

Abstract

A gravity base 400 for an upright (vertical axis) tidal turbine assembly comprises a plurality of feet 505, an upright hollow support column 515 arranged to envelope at least a portion of each of the

Description

Field of the invention The present disclosure relates to an upright tidal turbine assembly for converting kinetic energy of water into electrical energy and a gravity base for supporting said upright tidal turbine assembly and easing the installation and decommissioning process of placing the tidal turbine on the seabed. In particular, the present disclosure relates to an upright tidal turbine assembly comprising at least one turbine which has an upright vertical rotational axis in use and a gravity base comprising a cement or concrete fillable support column, a plurality of feet, and a tensioning mechanism. Background The concept of offshore tidal turbines is not new, however the majority of existing concepts, none of which have reached full market implementation, have used some form of horizontal axis turbine with all working parts under water. Under water horizontal axis turbines are extremely expensive to develop, install and maintain and this has meant that no existing concepts have been able to demonstrate that they are economically viable. The inventors of the present application have taken a completely different approach using vertical axis turbines. This innovative concept is designed to sit on the seabed but allows for all of the mechanics, generators and electrical equipment to be installed out of the water, above the highest tide level, in storm proof housings. This dramatically reduces the complexity and costs of construction because it allows for the use of standard “off the shelf” equipment. It also makes installation and maintenance much cheaper. It also allows each turbine to sweep a much larger area of water from just below the lowest tide level to just above the seabed. The installation and decommissioning of tidal turbines is known to be a demanding and expensive process, further exacerbating that inventive concepts in this field of energy production are rarely economically viable. Prior to installation the location selection for a tidal turbine often is restricted and time consuming. A selected location typically requires the removal of debris to level the seabed. A level seabed ensures that an inputted turbine has an axis suitable for converting tidal motion into electrical energy. Challenging marine environments require tidal turbines to comprise sturdy foundations; as of yet these foundations are fixed to the sea bed or embedded into the underlaying sediment before the tidal turbine is attached. This process takes substantial time and expensive equipment. The upright tidal turbines assembly themselves are traditionally assembled outside of the sea, transported, and then fixed to a foundation made previously. This process requires extensive transportation means and restricts the mass of the tidal turbine that can be transported. The inventors of the present application have taken a different approach to reduce the installation time and cost. The tidal turbine gravity base of the present application is comprised of parts that may be individually transported and slotted together in the sea without the need for a premade foundation. The individual parts and construction process also negates the need for a level seabed. The gravity base has a sturdy foundation which is made after construction, reinforcing the upright tidal turbine assembly in its place. This innovative concept makes installation and maintenance much cheaper. Summary of the invention Aspects of the invention are as set out in the independent claims and optional features are set out in the dependent claims. Aspects of the invention may be provided in conjunction with each other and features of one aspect may be applied to other aspects. An aspect of the disclosure provides a gravity base for supporting an upright tidal turbine assembly, the gravity base comprising; a plurality of feet configured for placement on the sea bed; a hollow support column configured to be orientated upright relative to the sea bed and arranged to envelope at least a portion of each of the plurality of feet; a support beam configured to be located above the sea level in use; and a tensioning mechanism configured to attach to each of the plurality of feet at one end and the support beam at the other end and to couple the plurality of feet, support beam, and support column together. Advantageously, a sturdy adaptable foundation on the seabed is provided by the gravity base. Providing a plurality of support feet enveloped by a hollow support column means that each of the support feet may self-position on the seabed to adapt to undulations on the seabed. The use of the tensioning mechanism may then hold the structure in tension together and hold the support feet in place. Advantageously, the tensioning mechanism clamps the support column, plurality of feet and support beam in place without the need for fastening means or attachment prior to installation in the water. The use of divers for attaching individual parts and the need for industrial seabed drills or anchors may therefore be negated. The tensioning mechanism may comprise a plurality of cables which pass through the inside of the hollow support column, wherein each of the plurality of cables is coupled to a respective one of the plurality of feet. Each end of the cables may be fastened at a position, in use, that is above the sea level - with each cable adjustably attaching to the support beam at one end above the sea level and attaching to a corresponding fitting on each foot at the other such that one end of the cable is fastened above the sea level in use. Each of the cables may be individually adjustable so that all cables are in tension and the plurality of feet, support beam and support column can be coupled by tension from the cables. Enabling each cable to be individually adjustable may mean that the tension on each foot can be adjusted to account for variations in relative position of each foot due to undulations of the seabed. Advantageously, the upright tidal turbine assembly can be held together tightly without the need for premade foundations or fastening means below the sea level. The feet can also sit on an uneven seabed and still hold the tidal turbine assembly fixedly upright relative to the seabed due to the adaptable positioning of the feet and tensioning mechanism. The coupling of the feet, support beam, and support column by the cables under the water rather than in the nearest dock allows individual transportation of each part. In examples, the support column comprises a plurality of stacked hollow cylinders that determine the height of the support column relative to the seabed. Advantageously, the support column can be adjusted to hold mechanics, generators, and electrical equipment out of the water, above the highest tide level, in storm proof housings. The support column in the form of cylinders is easy to transport to the installation location reducing transportation equipment and complications. Furthermore, this advantageously allows a generic set of components to be manufactured that can then be selected to accommodate variations in sea depth for the specific location of installation, thereby reducing cost in manufacturing. In examples, the cylinder of the support column which is distal to the sea level / surface has grooves proximal to the seabed to allow the support column to removably slot onto each of the plurality of feet. Advantageously, securing the support column around the feet does not require complicated fastening means and may hold the upright tidal turbine assembly in a fixed position without the need for pre-made seabed foundations. The plurality of feet may each comprise a cavity at the distal end to the support column to house the end of the turbine shafts which is proximal to the seabed. The cavity may be configured to enable the distal end of the support column to slot into place, enabling easy construction and placement in situ. The cavities in the plurality of feet, which house the turbine shafts, may be larger in width than the turbine shaft end to provide some excess space. Advantageously, the excess space in the cavity not occupied by the shaft may allow the turbine shafts to sit upright, for example at a non-90 degree angle relative to the seabed, if the gravity base is installed on a unlevelled seabed. Location requirements for the upright tidal turbine assembly are reduced and electrical energy can be produced in conditions beyond that of standard tidal turbines. In examples, the cavities in the plurality of feet may each comprise a nylon enclosure which act as a bearing and house the end of turbine shafts proximal to the sea-bed inside the cavity. Advantageously, the nylon enclosures may constrain relative motion of turbine shafts in the plurality of feet. This can reduce unwanted friction between the turning shaft and foot and in turn diminish any wasted electrical energy production to heating. The plurality of feet may be joined by horizontal cables, parallel to the seabed. Advantageously, the horizontal cables may fix the feet in position on the seabed and inhibit movement of the gravity base under tidal motion. The gravity base may further comprise a tube located along the axis of the support column wherein the tube is arranged to provide a pathway, from above the sea level to the bottom of the support column, for concrete to fill and strengthen the support column and to securely hold each of the plurality of feet in place within the support column. Advantageously, the tube within the gravity base may reduce the use of large equipment for deep sea concrete or cement deposition. This also negates the need for permanent concrete or cement structures under the seabed floor that cannot be removed when the tidal turbine is decommissioned. The tube located in the support column may comprise a first opening proximal to the plurality of feet for dispensing liquid cement or concrete, and second opening proximal to the support beam for receiving liquid cement or concrete. Advantageously, the input of cement or concrete into the support column secures the tidal turbine in place without the need for fastening means or extensive equipment, such as sea drills or anchor or sea divers. In particular, the cement of concrete fixes each of the plurality of feet in place, meaning that if any of the feet are at different relative angles to each due to the undulations of the underlying seabed, the feet are fixed at those different relative angles to ensure the gravity base has an even contact with the seabed, which may inhibit movement under strong sea currents. The gravity base, in use, may allow cement or concrete to move through the tube from above sea level to the base of the support column and hardens at the base of the support column around each of the plurality of feet, displacing water and creating a heavy base around the plurality of feet. Advantageously, the deposition of cement or concrete on top of the seabed may allow the gravity base to be removed when the tidal turbine is decommissioned. In examples, each of the plurality of feet comprises at least one eyelet on a side distal to the seabed for attachment to lifting buoys. Advantageously, this buoyancy aid makes the transportation and lowering of the gravity base to the seabed less mechanically demanding. The use of divers to place the gravity base pieces on the seabed is negated. Another aspect of the disclosure provides an upright tidal turbine assembly comprising the gravity base. The upright tidal turbine assembly comprises: a first turbine, comprising a first plurality of foils, that is configured, in use, to rotate around an upright axis that is upright relative to the sea bed; and a second turbine, comprising a second plurality of foils, that is configured, in use, to rotate around an upright axis that is upright relative to the sea bed; wherein the first turbine and the second turbine are coupled by a support beam. Advantageously, renewable electrical energy conversion is provided by the upright tidal turbine assembly. Tidal movements of water are regular and the electrical power output obtainable, using the present upright tidal turbine assembly, can be determined in advance. Therefore, the negative consequences which arise from the uncertainties in power output present in other renewable energy fields (e.g., wind and solar) do not manifest for the present tidal turbine assembly. Advantageously, providing two turbines may reduce the net torque on the upright tidal turbine assembly which in turn may reduce the amount offeree required to secure the tidal turbine to the seabed. In examples, the support column of the gravity base supports the support beam between the first and second turbines such that the first and second turbines are on either side of the support column. Advantageously, a symmetric gravity base and upright tidal turbine assembly can reduce the plurality of feet and installation requirements per turbine shaft to secure the tidal turbine to the seabed. For example, a tidal turbine with only one turbine shaft typically requires three feet whereas a tidal turbine with two turbine shafts positioned on either side of the support column can be secured with only four feet. Each turbine may comprise a turbine shaft wherein each turbine rotates about a turbine axis, wherein the turbine shaft is coupled to the support beam at one end and to the gravity base at the other end. In examples, a bearing is disposed between respective turbine shafts and the support beam. In examples, a bearing is disposed between respective turbine shafts and the gravity base. In examples, each turbine may comprise a turbine shaft wherein each turbine rotates about a turbine axis, wherein the turbine shaft is only coupled to the support beam (and not the gravity base). Each turbine may comprise a turbine shaft and a foil support for supporting the respective plurality of foils via a respective plurality of foil connections, Each turbine foil support may be configured to be movable up and down relative to the seabed to lift the foil connections out of the water. Advantageously, the foils can be replaced or removed for maintenance without the need to take tidal turbine assembly back to shore. In examples, the foil support of one turbine is configured to be movable independently of the foil support of another turbine. Another aspect of the disclosure provides an upright tidal turbine assembly comprising: a first turbine, comprising a first plurality of foils coupled via foil connections to a first foil support and a second plurality of foils coupled via foil connections to a second foil support, that is configured, in use, to rotate around a first turbine shaft about an upright axis that is upright relative to the sea bed; and wherein each of the first foil support and the second foil support are configured to be independently movable up and down relative to the first turbine shaft to thereby permit the plurality of foil connections to be lifted out of the water. The upright tidal assembly may further comprise: a second turbine, comprising a third plurality of foils coupled via foil connections to a third foil support and a fourth plurality of foils coupled via foil connections to a fourth foil support, that is configured, in use, to rotate around a second turbine shaft about an axis that is upright relative to the sea bed; wherein each of the third foil support and the fourth foil support are configured to be independently movable up and down relative to the second turbine shaft to thereby permit the plurality of foil connections to be lifted out of the water. Advantageously, the tidal turbines can produce electrical energy from tidal movements of water even if one foil support is raised above the sea level for maintenance. Advantageously, the upright turbine assembly can produce electrical energy from deep tidal movements of water even if one set of the two foil supports on a turbine shaft is raised above the sea level for servicing, repair, or replacement. Furthermore, providing two (or more) sets of foil supports per turbine shaft may allow energy to be extracted from a deeper body of water while, for example, still using individual foils of a uniform size. The at least two foil supports on each turbine shaft may be orientated at a different angle relative to each other, or in other words offset relative to each other, about the upright axis of the turbine shaft to allow the foil supports to be stacked on the turbine shaft and allow the attached plurality of foils to sit at proximal heights on the turbine shaft. Advantageously, the foils can be adjusted to a suitable position on each turbine in response to the currents and tidal motion and produce an optimal amount of electrical energy. Drawings Embodiments of the disclosure will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a side plan view of an example upright tidal turbine assembly; Figure 2 shows a top plan view of the upright tidal turbine assembly of Figure 1; Figure 3A shows a plan side view of the upright tidal turbine assembly of Figure 1 with foils lowered in the operational position; Figure 3B shows a plan side view of the upright tidal turbine assembly of Figure 1 with foils raised in the maintenance position; Figure 4 illustrates a side plan view of an upright tidal turbine assembly according to the disclosure; Figure 5 shows a perspective view of the gravity base which supports the upright tidal turbine assembly; Figure 6 shows a close-up perspective view of the gravity base of Figure 5 with some cylinders omitted to show the inner details of the support column; Figure 7 shows a close-up perspective view of the gravity base of Figure 5 with the cylinder proximal to the seabed slotting onto the feet; and Figure 8 shows a close-up perspective view of the cavity on a singular foot of the gravity base. In the drawings, like reference numerals indicate like elements. Soecific description Embodiments of the claims relate to an upright tidal turbine assembly configured to convert kinetic energy of water into electrical energy and a gravity base for supporting an upright tidal turbine assembly and easing the installation and decommissioning process of placing the tidal turbine on the seabed. In particular, the kinetic energy of the water may be provided by tidal forces which provide regular and predictable water movement. Figure 1 shows a side plan view of an example of an upright tidal turbine assembly 100; Figure 2 shows a top plan view of the upright tidal turbine assembly of Figure 1. It will be understood that this upright tidal turbine assembly may be used with the gravity base of Figures 5 to 7, described in more detail below. The upright tidal turbine assembly 100 comprises: a first turbine 110; a second turbine 120; a support beam 130; a support column 140; and a gravity base 150. The first turbine 110 is connected to the support beam 130. The second turbine 120 is connected to the support beam 130. The support column 140 connects the support beam 130 to the gravity base 150. The first turbine 110 comprises: a first plurality of foils, comprising a first A foil 111, a first B foil 112, and a first C foil 113; a first turbine shaft 115; a first power generating portion 117; a first foil support 118; a first plurality of foil connections 119. The first turbine 110 rotates about a first turbine axis. The second turbine 120 comprises: a second plurality of foils, comprising a second A foil 121, a second B foil 122, and a second C foil 123; a second turbine shaft 125; a second power generating portion 127; a second foil support 128; a second plurality of foil connections 129. The second turbine 110 rotates about a second turbine axis. Each foil 111-113 121-123 has a proximal end, p, and a distal end d, wherein each of the proximal ends is disposed closer to the support beam 130 than the respective distal end. Each foil 111-113 121-123 has a foil length defined as the length between the proximal end p and the distal end d. The foils have the same length. The length of the foils is less than the lowest water level L (e.g., the depth of water during the lowest tide). In examples, the foils may have lengths which are not equal to one another. For example, for a given plurality of foils, the A foil may be the longest foil, the C foil may be the shortest foil and the B foil may have a length which differs from that of the A foil and C foil. However, it will be understood that in other examples each foil may be of a standard, uniform, size. Each foil 111-113 121-123 is positively buoyant so that free foils (e.g., foils removed for maintenance or towed by sea to replace an existing foil) float at the surface of water. Advantageously, loss or costly recover of the foil from the seabed is prevented. Each foil 111-113 121-123 is weighted at its distal end so that each foil floats vertically (i.e., the proximal end floats at the surface and the distal end is disposed below the proximal end). Advantageously, weighting the foil in this manner permits easy connection of the proximal end of a foil to the respective foil support. The first plurality of foils (first A foil 111, first B foil 112, first C foil 113) is connected to the first foil support 118 by the first plurality of foil connections 119 at the proximal ends of said coils. The proximal end 111 p of the first A foil 111 is connected to the first foil support 118 by one of the foil connections 119. Likewise, the proximal end 112p of the first B foil 112 is connected to the first foil support 118 by another foil connection 119, and the proximal end 113p of the first C foil 113 is connected to the first foil support 118 by further foil connections 119. In a similar manner, the second plurality of foils (second A foil 121, second B foil 122, second C foil 123) are connected to the second foil support 128 by a second plurality of foil connections 129 at the proximal ends of said foils. Connecting the foils at the proximal ends permits easy connection and replacement thereof (e.g., in comparison to providing a connection at a distal end, which would either require using a diver or taking the whole assembly back to shore and / or lifting the whole assembly out of the water and onto a ship which is required for typical horizontally-orientated turbine assemblies). The first plurality of foils 111-113 are equidistantly arranged about a common centre i.e., the first plurality of foils equiangularly arranged to lie on the curved face of a cylinder. The first plurality of foils 111-113 are configured so that, when the upright tidal turbine assembly is installed for use, water moving past the first plurality of foils imparts a net rotational force on the first plurality of foils about their common centre. The first foil support 118 is configured to transmit said net rotational force to the first turbine shaft 115 to thereby rotate the first turbine shaft 115. Similarly, the second plurality of foils 121-123 are equidistantly arranged about another common centre. The second plurality of foils 121-123 are configured so that, when the upright tidal turbine assembly is installed for use, water moving past the second plurality of foils imparts a net rotational force on the second plurality of foils about their common centre. The second foil support 128 is configured to transmit said net rotational force to the second turbine shaft 125 to thereby rotate the second turbine shaft 125. The foils in a given plurality of foils are symmetric to thereby permit rotation of the plurality of the foils about their rotational axis when impinged upon by water moving in any direction oblique to the upright rotational axis of said plurality of foils. In examples, the foils in a given plurality of foils may be asymmetric. Advantageously, said foils may permit rotation of the plurality of the foils about their rotational axis when impinged upon by water moving in any direction oblique to the upright rotational axis of said plurality of foils. The first foil support 118 is movable relative to the support column 140. The first foil support 118 is moveable in a lateral direction along the upright rotational axis of the first turbine shaft 115 (i.e. the first rotational axis). When installed for use, movement of the first foil support 118 relative the support column 140 provides movement of the first foil support 118 relative to the seabed. The second foil support 128 is movable relative to the support column 140. The second foil support 128 is moveable in a lateral direction along the upright rotational axis of the second turbine shaft 125 (i.e., the second rotational axis). When installed for use, movement of the second foil support 128 relative the support column 140 provides movement of the second foil support 128 relative to the seabed. Moreover, the lateral movement of the foil supports 118 128 may permit the foil connections to be raised out of the water (see Figure 3B which illustrates the assembly in a maintenance position). Advantageously, one or more of the foils 111-113 121-123 can be replaced or removed for maintenance without the need to take tidal turbine assembly 100 back to shore or lifting the whole assembly out of the water and onto a ship which is required for typical horizontally orientated turbine assemblies. The lateral movement of the first foil support 118 along the rotational axis of the first turbine shaft 115 may be independent of the lateral movement of the second foil support 128 along the rotational axis of the second turbine shaft 125 (and vice versa). After maintenance has been performed, the foil supports 118 128 are moved down the respective turbine shafts into an operational position (shown in Figure 3A). The first plurality of foils 111-113 is coupled to the first turbine shaft 115. The first turbine shaft 115 is configured to rotate about the first upright rotational axis. The second plurality of foils 121-123 is coupled to the second turbine shaft 125. The second turbine shaft 125 is configured to rotate about the second upright rotational axis. The first upright axis is parallel to a second upright axis (about which the second turbine shaft 125 rotates). The first turbine shaft 115 is configured to rotate when a net rotational force is applied to the turbine by the first plurality of foils 111-113 (connected thereto by the first foil support 118). Likewise, the second turbine shaft 125 is configured to rotate when a net rotational force is applied to the turbine by the second plurality of foils 121-123 (connected thereto by the second foil support 128). When the upright tidal turbine assembly is installed for use, the first rotational axis is vertical with reference to the seabed (i.e., approximately perpendicular to the seabed). The first turbine shaft 115 is coupled to the support beam 130. The first turbine shaft 115 is coupled to the gravity base 150. The first turbine shaft 115 is rotatable relative to the support beam 130 and the gravity base 150 about the first rotational axis which extends between the support beam 130 and the gravity base 150. The first rotational axis is upright in use i.e., when the upright tidal turbine assembly is installed for use. A first bearing is disposed between the first turbine shaft 115 and the support beam 130 and a second bearing is disposed between the first turbine shaft 115 and the gravity base 150 to reduce friction therebetween due to rotation of the first turbine shaft 115. Similarly, the second turbine shaft 125 is coupled to the support beam 130. The second turbine shaft 125 is coupled to the gravity base 150. The second turbine shaft 125 is rotatable relative to the support beam 130 and the gravity base 150 about the second rotational axis which extends between the support beam 130 and the gravity base 150. The second rotational axis is upright in use i.e. when the upright tidal turbine assembly is installed for use. A third bearing is disposed between the second turbine shaft 125 and the support beam 130 and a fourth bearing is disposed between the second turbine shaft 125 and the gravity base 150 to reduce friction therebetween due to rotation of the first turbine shaft 125. The support beam 130 holds the turbine shafts 115 125 either side of the support column 140 at distal points to the support column 140. The support beam 130 is configured to provide support to the distal end of the tidal turbine shafts 115 125, near the sea level. In examples, the tidal turbine shafts 115 125 are also configured to attach to the plurality of feet 605 at their proximal end, near the seabed. In examples, the turbine shafts 115 125 may be coupled to the support beam only (i.e., not coupled to the gravity base 150). The first turbine shaft 115 is coupled to the first power generating portion 117. The first power generating portion 117 comprises a first generator which is configured to generate power when the first turbine shaft 115 is turned. Similarly, the second turbine shaft 125 is coupled to the second power generating portion 127. The second power generating portion 127 comprises a second generator which is configured to generate power when the second turbine shaft 125 is turned. The first power generating portion 117 and the second power generating portion 127 are disposed on the support beam 130. When installed for use, the first power generating portion 117 and the second power generating portion 127 are disposed above the water level (e.g., above the water level of the highest tide H). Advantageously, maintenance of the power generating portions 117 127 is comparatively easy given the relative ease of access thereto (i.e., is not disposed underwater or in a confined space) in comparison to other tidal turbine assemblies. Advantageously, the power generating portions 117 127 can be formed of components which are not specially adapted for use under the water (e.g., so-called off-the-shelf components can be used to form the power generating portions) which can reduce the overall manufacturing and maintenance costs of the upright tidal turbine assembly. Electrical power may be stored at each of the power generating portions or in an energy storage device (e.g., a battery) disposed at the upright tidal turbine assembly 100. The power generating portions may be connected to an electrical power grid for distribution of said electrical power to electrical devices connected to the grid. In examples wherein energy generated by the power generating portions is stored at the upright tidal turbine assembly 100 in an energy storage device, the energy storage device may be connected to an electrical power grid for distribution of said power. The support column 140 is hollow and configured to be buoyant for floating prior to installation. This permits the upright tidal turbine assembly 100 to be towed to an installation location rather than carried upon a ship. Advantageously, the size of the ship required to move the upright tidal turbine assembly from the shore to an installation location may be reduced which may in turn reduce the installation cost of the upright tidal turbine assembly. The gravity base 150 is a weighted base structure. The gravity base 150 is weighted so that when the upright tidal turbine assembly 100 is kept in a given installation location relative to the seabed, thereby preventing damage to the tidal turbine system. The weight may be provided by the weight of the structure itself, but additionally weight may be added by filling the structure with cement or concrete. However, in some examples, the gravity base can be replaced by a driven monopile and or a monopile of a wind turbine. The gravity base 150 supports the support column 140 in an upright orientation relative to the seabed in use. This ensures that the support beam 130 and the first and second power generating portions 117 and 127 are disposed above sea level. Figure 4 shows a side plan view of an upright tidal turbine assembly 400 according to the disclosure. This upright tidal turbine assembly 400 is similar to that of 100, as shown in Figures 1-3B, as it has a plurality of foils 411-413, 431-433 connected to a plurality of foil connections 419, 439 which are connected to foil supports 414, 434. The upright turbine assembly 400 also has the same turbine shafts 115, 125 either side of the support column 140 which supports a support beam 130 and a gravity base 150 holding the upright tidal turbine assembly 400 in place. Upright tidal turbine assembly 400 is different to that of 100 as the two turbine shafts 115, 125 comprise an addition foil support 424, 444 with a corresponding additional plurality of foil connections 429, 449 coupled to an additional plurality of foils 421-423, 441-443. Like the foil supports, foil connections and foils in tidal turbine assembly 100 the additional plurality of foils 411-413, 421-423, 431-433, 441-443 are positively buoyant, equidistantly arranged about a common centre and are connected to the foil connections 419, 429, 439, 449 at the end of said foils proximal to the sea level / surface. As before, the first turbine shaft 115 is coupled to the first power generating portion 117 and the second turbine shaft is coupled to the second power generating portion 122. Upright tidal turbine assembly 400 has two foil supports which reside on each turbine shaft 115, 125 wherein both supports comprise a central sheath which sits about the turbine shaft and connects to the plurality of foil connections and in turn the plurality of foils. As shown in Figure 4, the first turbine shaft 115 comprises a first plurality of foils 411 -413, coupled via foil connections 419 to a first foil support 414, and a second plurality of foils 421-423, coupled via foil connections 429 to a second foil support 424. The foil supports 414, 424, byway of the plurality of foil connections 419, 429, hold the plurality of foils 411 -413, 421-423 upright relative to the seabed and parallel to the turbine shaft axis 115 at a horizontal distance from the first turbine shaft axis 115. The central sheaths of the two foil supports 414, 424 sit about the first turbine shaft 115. The outer diameter of the central sheath of the top foil support 414 is smaller in diameter than the inside diameter of the lower foil support sheath 424, such that the sheaths may “telescope” within each other. The two foil supports 414, 424 on the first turbine shaft 115 may be configured, in use, to rotate independently around the first turbine shaft 115. The first and second foil supports 414, 424 are configured to be independently movable up and down relative to the first turbine shaft 115. The two central sheaths of the foil supports 414, 424 on the first turbine shaft 115 can slide over one another on the turbine shaft 115. The first and second foil supports 414, 424 are configured to be able to sit at different heights relative to the support column 140 or stack on top of one another, as shown in Figure 4. This may be due to their disparate central sheath diameters, although it will be understood that other means for fixing the foil connections at different relative positions on the first turbine shaft 115 may be used, such as a clamp or other gripping means to detachably fasten each foil support to the first turbine shaft 115. The plurality of foil connections 419,429 are thereby permitted to be lifted above the sea level / surface independently. Likewise, as shown in Figure 4, the second turbine shaft 125 is coupled to a third plurality of foils 431-433, via foil connections 439 to a third foil support 434, and a fourth plurality of foils 441-443, via foil connections 449 to a fourth foil support 444. The foil supports 434, 444, by way of the plurality of foil connections 439, 449, hold the plurality of foils 431-434, 441-443 upright relative to the seabed and parallel to the turbine shaft axis 125 at a horizontal distance from the turbine shaft axis 125. The central sheaths of the two foil supports 434, 444 sit about the second turbine 125. The outer diameter of the central sheath of the top foil support 434 on the turbine 125 is smaller in diameter than the inside diameter of the lower foil support sheath 444 on the turbine 125. The two central sheaths of the foil supports on the second turbine shaft 125 can therefore slide past or over one another on the turbine shaft 125. The two foil supports 434, 444 on the second turbine shaft 125 are configured, in use, to rotate independently around the second turbine shaft 125. The third and fourth foil supports 434 444 are configured to be independently movable up and down relative to the second turbine shaft 125. The two central sheaths of the foil supports 434, 444 on the second turbine shaft 125 shown in Fig. 4 are configured to slide over one another on the turbine shaft axis 125. The third and fourth foil supports 434, 444 are configured to be able to sit at different heights relative to the support column 140 or stack on top of one another as shown in Figure 4, due to their disparate central sheath diameters, although again it will be understood that other means for fixing the foil connections at different relative positions on the second turbine shaft 125 may be used, such as a clamp or other gripping means to detachably fasten each foil support to the second turbine shaft 125. The plurality of foil connections 439 449 are thereby permitted to be lifted above the sea level independently. In Figure 4 the two foil supports 414, 424, 434, 444 on each turbine shaft 115, 125 are offset relative to each other about the upright axis of the turbine shaft 115, 125 so that the foil support sheaths 414, 424, 434, 444 on the same turbine shaft 115, 125 are stacked on the turbine shaft 115, 125. In examples, the horizontal breath of the two foil supports on a given turbine axis may be different. As a result, the two foil supports of a given turbine may hold the plurality of foils at different distances from the turbine axis. In such examples, the foil supports do not need to be offset relative to one another in order for the two foil supports and plurality of foils to stack on top of one another at the same height relative to the support column 140. The two pluralities of foils 411-413, 421-423, 431-433, 441-443 on a turbine shaft 115, 125 can sit at proximal or distal heights on the turbine shaft 115, 125. In some examples, each of the foil supports 514, 524, 534, 544 on each turbine shaft 115, 125 may be able to rotate independently of each other - for example one foil support on a turbine shaft may be able to rotate while the other is held static. This may be via use a of a clutch or clamp mechanism that can detachably fasten each foil support to its corresponding turbine shaft. Additionally, or alternatively, each sheath as described above may be configured to detachably couple to the power generation portions 117, 127. The independent motion of the foil supports 514, 524, 534, 544 on each turbine shaft 115, 125 of the turbine assembly 100 may allow each turbine to have different foil arrangements to one another. In use, the two foil supports, plurality of foil connections and plurality of foils per turbine rotate about the turbine shafts with oncoming tidal motion and provide reliable electrical energy production even if one or more plurality of foils is lifted above the sea level. The foil supports 514, 524, 534, 544 and thereby foils may be moved up and down in response to the depth of the sea level and the motion of the tides. Figure 5 shows a perspective view of the gravity base 150 which may support the upright tidal turbine assembly 400, such as the upright tidal turbine assembly 100 of Figures 1-3B, although it will be understood that in some examples the gravity base can be replaced by a driven monopile. Figure 6 shows a perspective view of the gravity base 100 of Figure 5 with some hollow cylinders 515 omitted to show the inner details of the support column 140. The gravity base 150 comprises: a plurality of feet 505; a support column 140; a support beam 130; a tensioning mechanism 605; and a hollow tube 610. Each foot 505 is adjacent to and runs along the seabed. Each foot 505 has a proximal end, p, and a distal end, d, wherein each of the proximal ends are disposed at the centre of the support column 140 and the distal ends protrude away from the support column 140 adjacent to the seabed. The proximal end of each foot in the plurality of feet, not visible in Figure 5, may comprise a clip, joint or link to couple each of the plurality of feet together, although as described below in more detail in some examples there may not be a clip, joint or link and instead the plurality of feet may be coupled by the bottom cylinder 520 of the support column 140. However, the skilled person will understand that other clip or linking configurations may be used, for example a lock and key, hook and dock or other joining mechanism. When the proximal end of each foot come together, they are configured to join together forming a fixed support base. In use, the support base created by the plurality of feet forms the stabilising mechanism for the tidal turbine assemblies 100, 400 and gravity base 150. Each foot 505 has a foot length defined as the length between the proximal end p and the distal end d. The plurality of feet 505 have the same length. The length of the feet is greater than the distance between the base of the support column 140, proximal to the seabed, and the base of a tidal turbine shaft 115 125, proximal to the seabed. Advantageously, the turbine shafts 115 125 can be secured to the plurality of feet 505, at the end proximal to the seabed, as well as the support beam 140, at the end distal to the seabed. In examples, the feet 605 may not have equal lengths. For example, feet 605 that do not secure a tidal turbine may be shorter than those that do if the space for the gravity base 150 is limited. In examples, all the feet 505 may have lengths smaller than the distance between the base of the support column 140, proximal to the seabed, and the base of a tidal turbine shaft 115 125, proximal to the seabed. For example, the turbine shafts 115 125 may be secured to the support beam 140 at the end distal to the seabed only. In this example the gravity base 150 may not need to be as large and the foot length is reduced. As shown in Figure 5, each foot 505 comprises eyelets 510 on the side distal to the seabed. The eyelets 505 are configured for the attachment of lifting buoys to each foot 505 of the plurality of feet 505. In use, prior to the tidal turbine assembly 100, 400 installation, the plurality of feet 505 with the attached lifting buoys can float in the water and easily be transported and lowered to the upright tidal turbine assembly 100, 400 location. Each foot 505 may comprise a cavity at the end distal to the support column 140 to house the end of a tidal turbine shaft 115, 125 which is proximal to the seabed. The cavity has volume greater than the end of the turbine shafts 115, 125. This permits the tidal turbine shafts 115 125 to be supported by the plurality of feet 505. The cavity in the distal end of each foot comprises a slot, open on the side of the foot distal to the support column. The cavity and slot are configured to removably allow the end of a turbine shaft 115, 125 to slide sideways or vertically into the cavity and sit within the distal end of the foot 505. In use, the turbine shaft 115, 125 is secured to the gravity base directly allowing electrical energy to be generated in turbulent deep tidal motions. Advantageously, the excess volume of the cavity and slot allows the turbine shaft 115, 125 end to move adjustably within the housing to stay upright in turbulent motion or on a slanted seabed. In examples, the cavity may be closed and not comprise a slot opening to the distal end of the foot 505. In such example the turbine shaft 115, 125 is removably placed into the cavity from above and supports the turbine in all lateral motion. In examples, the cavity of each foot may also contain a nylon, or similar material, enclosure 805 which surrounds the end of the housed turbine shaft 115, 125 and acts as a bearing to constrain relative motion of the turbine shaft 115, 125 and reduce friction between the turning shaft 115, 125 and foot 505. This component is demonstrated in Figure 8 and is discussed in more detail below. This component is optional and may not be present in some tidal turbine assemblies and gravity base examples. For example, some tidal turbine assemblies may have turbine shafts which attach to the support beam only. In such assemblies, the gravity base need not house the turbine shafts and therefore will not require a nylon enclosure 805. Figure 5 shows that the support column 140 of the gravity base 150 and upright tidal turbine assemblies 100, 400 comprises a plurality of stacked hollow cylinders 515. The cylinders 515 are shaped specifically to stack on top of one another to make the support column 140. The cylinders 515 are stacked with the bottom cylinder 520 on the seabed and the top cylinder at or above the sea level to make the support column 140 upright relative to the seabed. The proximal end of the column 140 to the seabed is located on top of the central point between the plurality of feet 505 where all the proximal ends of the feet 505 meet. The proximal end of the column 140 to the sea level is located adjacent to the support beam 130. The support cylinders, when stacked to form the support column, are configured to be stabilised on the plurality of feet and to support the support beam 130 above the sea level. The cylinders 515, and in particular the bottom cylinder 520, may also couple the plurality of feet 505 together. The amount of cylinders 515 stacked between the plurality of feet 505 and support beam 130 may be changed to alter the height of the hollow support column 140 relative to the seabed. The support column 140 height may therefore be changed to adapt to the sea level height. The support column cylinders 515 are hollow and may be configured to be buoyant for floating prior to installation. This permits the upright tidal turbine assembly 100 to be towed to an installation location rather than carried upon a ship. Advantageously, the size of the ship required to move the upright tidal turbine assembly 100 from the shore to an installation location may be reduced which may in turn reduce the installation cost of the upright tidal turbine assembly 100. Figure 6 shows a close-up view of the gravity base 150 wherein there is a plurality of feet 505 connected to the support column 140. The support column 140 is hollow and made up of the stacked hollow cylinders 515 as shown in Figure 5. Figure 6 has omitted some cylinders 515 from the support column 140 to show a tensioning mechanism 605 and tube 610 within the support column 140. The tensioning mechanism 605 comprises a plurality of cables (as shown in Figures 6). The plurality of cables 605 have a distal end to the seabed, which attach to the plurality of feet 505, and a proximal end to the sea level, which attach to the support beam 130. The proximal end of each of the cables passes through and removably attaches the upper side of the support beam 130 distal to the sea level. The support beam 130 sits proximal to (but above) the sea level. The support beam 130 extends horizontally, running parallel to the sea level. The support beam 130 comprises a central point at the centre of its length which is removably clamped to the support column 140. The central point of the support beam 130 is hollow and dissects the support beam 130 to allow the tensioning mechanism 705 to pass from the support column 140 through the support beam 130 to the distal side of the support beam 130 above the sea level. The tensioning mechanism 705 is attached to the distal side of the support beam 130 in a way such that it can be adjusted or held fixed. Each end of the plurality of cables 605 proximal to the seabed is coupled to a respective one of the plurality of feet 505. The middle of the cables 605, between the feet 505 and support beam 130, pass through each cylinder 515 of the plurality of the cylinders 515. The tensioning mechanism cable 605 lengths can be adjusted at the proximal end to the sea level. Each cable of the tensioning mechanism 605 can be adjusted individually. The cables 605, when attached to the feet 505 at one end, passing through the cylinders 515, and attaching to the support beam 130 at the other, are configured to securely hold the stacked plurality of cylinders 515 on top of one another and secure the feet 505, support column 140, and support beam 130 into a removably fixed position. The adjustable length of the cables 605 configure the support column 140 and support beam 130 to sit fixedly on the plurality of feet 605 on an unlevel seabed. In use, when the cables 605 are pulled to tension, the stacked cylinders 515 are clamped together forming the support column 140 which stabilises and holds the tidal turbine assembly 100, 400 upright on the plurality of feet 505 on the seabed. The cables 605, acting as a coupling mechanism, hold the gravity base 150 and upright tidal turbine assembly 100, 400 together and nullify tidal forces. As shown in Figure 6 a tube 610 is situated within the support column 140, in the middle of the tensioning mechanism 605. The tube 610 is hollow, sits parallel to the support column 140 axis and has a proximal end, near the seabed, and a distal end, near the sea level. The proximal end has an opening within the bottom cylinder 520 of the support column 140, near the plurality of feet 505, and the distal end has an opening above the sea level in the central point of the support beam 140. The tube 610 is hollow and configured to be buoyant for floating prior to installation like the support column cylinders 515. Figure 7 shows a close-up perspective view of the gravity base 150 of Figure 5 with the bottom cylinder 520, the cylinder proximal to the seabed, lifted to show the bottom cylinder 520 slotting onto the plurality of feet 505. The bottom cylinder 520 is the base of the support column 140 and is shaped to removably stack the hollow cylinders 515 above. The bottom cylinder 520 is hollow, proximal to the seabed, and when in the lowered position is adjacent to the seabed. The bottom cylinder 520 envelopes the connecting point of the proximal ends of the plurality of feet 505 and houses the end of the hollow tube 610. The proximal end of the bottom cylinder 520 has four sets of grooves 705 that are shaped to the topography of the side of the plurality of feet 505 distal to the seabed. The proximal end of the plurality of feet 505, at their connecting point, sit within the bottom cylinder 520. The distal end of the plurality of feet 505 protrude away from the bottom cylinder 520 running along the seabed. As shown in Figure 7 the bottom cylinder 520 is configured to removably slot on top of the plurality of feet 505 when the grooves 705 are aligned with the plurality of feet 505. The bottom cylinder 520 is configured to provide a contained space for liquid cement or concrete to be deposited via the hollow tube 610. The bottom cylinder 520 is configured to provide a connection between the tidal turbine assembly 100, 400 and the gravity base 150 without a fastening means or underground fixing mechanism. In use, prior to cement or concrete deposition the bottom cylinder 520 removably holds the support column 140 and support beam 130 on the plurality of feet 505 and seabed. After cement or concrete deposition, the bottom cylinder 520 holds the heavy component of the gravity base 150 onto the seabed and the tidal turbine assembly 100, 400 to the gravity base 150. Figure 8 shows a close-up perspective view of a cavity in a singular one of the plurality of feet 505 which form the gravity base 150. This cavity is one of many which sit in the end of each of the plurality of feet 505 distal to the support column 140. As discussed above, the cavity may be open ended to the distal end of the foot 505 or closed at the end. The cavity may also house the end of a turbine shaft 115, 125 which is proximal to the seabed. In Figure 8 an example embodiment of the cavity is shown where a turbine shaft 115, 125 is housed in the cavity by way of a nylon, or similar material, enclosure 805. The enclosure 805 is round on the inside to couple to the turbine shaft and is rectangular on the outside to fit into a cavity. The enclosure 805 sits between the cavity of the foot and the turbine shaft and surrounds the end of the turbine shaft. The inside of the enclosure 805 may rotate with the turbine shaft while the outside stays fixed to the shape of the cavity. The enclosure 805 is configured to act as a bearing for the turbine shaft 115, 125 to constrain the motion of the bottom of the turbine shaft 115,125 under turbulent tidal motion and when rotating in use. In use, the enclosure 805, acting as a bearing, diminishes friction between the cavity and the rotating turbine shaft 115, 125 and reduces any rotational motion being wasted to heating the cavity rather than generating electrical energy. An aspect of the disclosure provides a method of installing the upright tidal turbine assembly 100 and gravity base 150. The method of installing the upright tidal turbine assembly 100 and gravity base 150 comprises providing an upright tidal turbine assembly 100 and gravity base 150 e.g. a tidal turbine assembly 100 and gravity base 150 according to the present disclosure. Next the upright tidal turbine assembly 100 and gravity base 150 is towed to an installation location. The upright tidal turbine assembly 100 and gravity base 150 is configured to be buoyant so that the assembly 100 and base 150 can be floated and towed to the installation location. Tidal turbine assemblies 100 and gravity base 150 of the present disclosure comprise a hollow support column 140 and a plurality of feet 505 with eyelets 510 for attaching lifting buoys. The hollow support column 140 and plurality of feet 505 provide at least part of the required buoyancy to float the upright tidal turbine assembly 100, 400 and gravity base 150. Once the upright tidal turbine assembly 100, 400 and gravity base 150 are disposed above the installation location, the lifting buoys are deflated at the same time to ensure that each part of the assembly 100, 400 and base 150 are deposited on the seabed at the same time and at a slow and controlled rate. The individual parts slot into place. In the present example, the hollow interior of the support column 140 is flooded (e.g., with sea water) and the lifting buoys are released which reduces the overall buoyancy of the assembly 100, 400 and base 150. The upright tidal turbine assembly 100, 400 and gravity base 150 then sink to the seabed and slot into place. The plurality of feet 505 adapt to the topography of the seabed floor. The cables 605 of the tensioning mechanism 605 within the, now flooded, support column 140 are tightened individually to each foot 505. Tightening of the tensioning mechanism 605 secures the support beam 130, support column 140, and plurality of feet 505 into a removably fixed position. In turn the upright tidal turbine assembly 100, 400 and gravity base 150 are removably fixed in position on the seabed. This permits the upright tidal turbine assembly 100, 400 and gravity base 150 to supportably fix to the seabed while the tidal turbines 110, 120, 410, 420 can still rotate relative to their turbine shafts 115, 125. Once removably fixed in place on the seabed the tube 610 in the support column 140 receives liquid cement or concrete at the end proximal to the sea level. The liquid cement travels down the tube 610 and exits via the end proximal to the seabed at the base of the support column 140. The liquid cement or concrete then hardens at the base of the support column 140 around each of the plurality of feet 505. The cement or concrete displaces water, creating a heavy gravity base 150 around the plurality of feet 505 and permanently fixing the support column 140, plurality of feet 505 and extended upright tidal turbine assembly 100, 400 in place on the seabed. The gravity base 150 is designed (e.g., sufficiently weighted and / or shaped) so that once the assembly 100, 400 is sunk to the installation location, the gravity base 150 is immovable relative to the seabed in the response to natural force (e.g., water forces due to currents and tides). Advantageously, this may simplify installation e.g., divers may not be required to secure the base 150 to the seabed. In examples, the gravity base 150 may be secured to the seabed. In alternative examples, a monopile may be provided in the place of the gravity base 150. In such examples, the monopile is driven into the seabed to thereby secure the upright tidal turbine assembly 100, 400. An aspect of the disclosure provides a method of use of the upright tidal turbine assembly 100, 400. When the upright tidal turbine assembly 100, 400 and gravity base 150 is installed at an installation location then the assembly may be used to convert the kinetic energy of tidal waters into electrical energy. The foils are disposed below the level of the lowest tide L (see Figure 3A). From low tide to high tide there is a net movement of water in a first direction. The water moves past the first and second turbine 110, 120 which causes a corresponding rotation of the turbines 110, 120. The rotation of the turbines 110, 120 generates electrical energy at the first and second power generating portions 117, 127. The generated electrical energy can be sent to the power grid onshore. Similarly, from high tide to low tide there is a net movement of water in a second direction (e.g., generally opposite to the direction of the first direction). The water moves past the first and second turbine 110, 120 which causes a corresponding rotation of the turbines 110 120. The rotation of the turbines 110, 120 generates electrical energy at the first and second power generating portions 117, 127. The generated electrical energy can be sent to the power grid onshore. As the turbines are symmetrical, they will rotate irrespective of the new movement direction of the water. Advantageously, energy can be generated during both tidal movements. Examples described herein refer to sea water and the seabed, but it will be appreciated that the present invention may also be used in fresh water or brackish water. Examples described herein refer to extracting energy from tidal waters, but it will be appreciated that the present invention may also be used in any body of water which exhibits a net flow of water (e.g., rivers). Importantly tidal turbine assemblies 100 and 400 illustrate how a general tidal turbine assembly having any number of turbines or foil supports may be provided. It will be evident to one of ordinary skill in the art that an additional turbine or foil support can be added to any given tidal turbine assembly described herein by noting the differences between tidal turbine assembly 100 and 500 and applying these differences to a given upright tidal turbine assembly. Providing an upright tidal turbine assembly comprising more than two turbines or foil supports may advantageously increase the power yield of a given upright tidal turbine assembly. It will be appreciated from the discussion above that the embodiments shown in the Figures are merely exemplary, and include features which may be generalised, removed or replaced as described herein and as set out in the claims. In the context of the present disclosure other examples and variations of the apparatus and methods described herein will be apparent to a person of skill in the art.

Claims

1. A gravity base for supporting an upright tidal turbine assembly, the gravity base comprising;a plurality of feet configured for placement on the seabed;a hollow support column configured to be orientated upright relative to the seabed and arranged to envelope at least a portion of each of the plurality of feet;a support beam configured to be located above the sea level in use; anda tensioning mechanism configured to attach to each of the plurality of feet at one end and the support beam at the other end and to couple the plurality of feet, support beam, and support column together.

2. The gravity base of claim 1 wherein the tensioning mechanism comprises a plurality of cables passing through the support column, wherein each of the plurality of cables is coupled to a respective one of the plurality of feet.

3. The gravity base of claim 2 wherein each of the cables is individually adjustable so that all cables are in tension and the plurality of feet, support beam and support column can be coupled by tension from the cables.

4. The gravity base of claim 1 wherein the support column comprises a plurality of stacked hollow cylinders that determine the height of the support column relative to the seabed.

5. The gravity base of claim 4 wherein the cylinder of the support column which is distal to the sea level has grooves proximal to the seabed to allow the support column to removably slot onto each of the plurality of feet.

6. The gravity base of any of the previous claims further comprising a tube located along the axis of the support column wherein the tube is arranged to provide a pathway, from above the sea level to the bottom of the support column, for concrete to fill and strengthen the support column and to securely hold each of the plurality of feet in place within the support column.

7. The gravity base of claim 6 wherein the tube located in the support column comprises a first opening proximal to the plurality of feet for dispensing liquid cement or concrete, and second opening proximal to the support beam for receiving liquid cement or concrete.

8. The gravity base of claim 7 wherein, in use, cement or concrete is configured to move through the tube from above sea level to the base of the support column and hardens at the base of the support column around each of the plurality of feet, displacing water and creating a heavy base around the plurality of feet.

9. The gravity base of any of the previous claims wherein each of the plurality of feet comprises at least one eyelet on a side distal to the seabed for attachment to lifting buoys.

10. An upright tidal turbine assembly comprising the gravity base of any of the previousclaims.

11. The upright tidal turbine assembly of claim 10 comprising;a first turbine, comprising a plurality of foils, that is configured, in use, to rotate around an upright axis that is upright relative to the seabed; anda second turbine, comprising a plurality of foils, that is configured, in use, to rotate around an upright axis that is upright relative to the seabed;wherein the first turbine and the second turbine are coupled by the support beam.

12. The upright tidal turbine assembly of claim 11 wherein the support column supports the support beam between the first and second turbines such that the first and second turbines are on either side of the support column.

13. The upright tidal turbine assembly of claim 11 or 12 wherein each turbine comprises a turbine shaft wherein each turbine rotates about a turbine axis, wherein the turbine shaft is coupled to the support beam at one end and to the gravity base at the other end.

14. The upright tidal turbine assembly of claim 11 or 12 wherein each turbine comprisesa turbine shaft wherein each turbine rotates about a turbine axis, wherein the turbine shaft is only coupled to the support beam.

15. The upright tidal turbine assembly of claim 10,11,12,13 or 14 wherein each turbine comprises a turbine shaft and a foil support for supporting the respective plurality of foils via a respective plurality of foil connections.

16. The upright tidal turbine assembly of claim 15 wherein the foil support is configured to be movable up and down relative to the turbine shaft to thereby permit the plurality of foil connections, and attached plurality of foils, to be lifted out of the water.

17. The upright tidal turbine assembly of claim 16 wherein the foil support of one turbine is configured to be movable relative to the turbine shaft independently of the foil support of another turbine on another turbine shaft.

18. An upright tidal turbine assembly comprising:a first turbine, comprising a first plurality of foils coupled via foil connections to a first foil support and a second plurality of foils coupled via foil connections to a second foil support, that is configured, in use, to rotate around a first turbine shaft about an upright axis that is upright relative to the seabed; andwherein each of the first foil support and the second foil support are configured to be independently movable up and down relative to the first turbine shaft to thereby permit the plurality of foil connections to be lifted out of the water.

19. The upright tidal turbine assembly of claim 18 further comprising:a second turbine, comprising a third plurality of foils coupled via foil connections to a third foil support and a fourth plurality of foils coupled via foil connections to a fourth foil support, that is configured, in use, to rotate around a second turbine shaft about an axis that is upright relative to the seabed;wherein each of the third foil support and the fourth foil support are configured to be independently movable up and down relative to the second turbine shaft to thereby permit the plurality of foil connections to be lifted out of the water.

20. The upright tidal turbine assembly of claim 18 or 19 wherein the two foil supports on each turbine shaft are orientation at a different angle about the upright axis of the turbine shaft to allow the foil supports to be stacked on the turbine shaft and allow the attached plurality of foils to sit at proximal heights on the turbine shaft.

521. The upright tidal turbine of claim 18, 19 and 20 wherein the first turbine and the second turbine are coupled by a support beam;and wherein a support column supports the support beam between the first and second turbines such that the first and second turbines are on either side of the support 10 column;and wherein the support column supports the support beam, in use, above the sea level.

Images