TECHNICAL FIELD

The present disclosure relates to a wind turbine array of a floating windfarm connection architecture, to a floating windfarm connection architecture and to a subsea power hub for use in a floating windfarm connection architecture.

BACKGROUND

In the field of wind energy, wind farms consisting of a number of individual wind turbines can be situated on land or offshore. The cost of offshore wind energy production is dependent amongst other factors on both capital expenditure (CAPEX) and operating expense (OPEX). Offshore wind energy producers and their suppliers are thus always seeking ways of reducing both CAPEX and OPEX in order to reduce the cost and improve the cost effectiveness of energy production.

One significant CAPEX factor in floating offshore wind farms is the cost of the dynamic cables which connect the wind turbines to one another and to the substation(s). In some known arrangements for example, wind turbines may be connected together in a “daisy chain” arrangement (the wind turbines being connected together in series in a ring) which requires a large amount of costly dynamic cable. It is therefore desirable to reduce the CAPEX costs associated with dynamic cable in offshore wind farms.

Further, in offshore windfarms, the individual wind turbines have typically been connected to one another in series to form a string, a wind turbine at the end of the string being connected to either a floating or subsea substation. The substation may then in turn be connected with appropriate power storage or distribution facilities on shore.

The series connection of the string of individual wind turbines has the disadvantage that a fault in a single connection between two wind turbines may stop current from any of the wind turbines in the string from reaching the substation. Thus, a fault in a single cable may lead to significant energy production losses, leading to an increase in OPEX costs.

In addition, as the string of individual wind turbines are connected in series, the current carried by the cable connecting the wind turbines will increase along the string, such that a cable having a large enough conductor cross section to carry the current produced by the entire string of wind turbines will be required at the end of the string. As such cables are expensive both to buy and install, typically different cables having a number of conductor cross section sizes, for example 3 different sizes, have been used so as to increase the conductor cross section along the string as the current produced increases along the string.

The present disclosure therefore provides a wind turbine array for a floating windfarm connection architecture, a floating windfarm connection architecture and a subsea power hub which seek to reduce both the CAPEX and OPEX costs of the windfarm, thus providing a more cost effective means of producing and distributing electricity from offshore wind energy.

SUMMARY

From one aspect, the present disclosure provides a wind turbine array for a floating windfarm connection architecture, the array comprising: a subsea power hub; and a plurality of groups of floating wind turbines, wherein each group of floating wind turbines comprises a first floating wind turbine connected to a second floating wind turbine by a power cable, and wherein each group of floating wind turbines is connected to the subsea power hub by a power cable extending between the first floating wind turbine and the subsea power hub.

In any example of the disclosure, the wind turbine array may be for a floating windfarm electrical connection architecture. In any example of the disclosure, the power cable connecting the first floating wind turbine to the second floating wind turbine and /or the power cable connecting each group of floating wind turbines to the subsea power hub may be a dynamic cable.

In any example of the disclosure, the wind turbine array may comprise three or more groups of floating wind turbines.

In any example of the disclosure, the wind turbine array may comprise four or more groups of floating wind turbines.

In any example of the disclosure, the wind turbine array may comprise four or five groups of floating wind turbines.

In any example of the disclosure, at least one of the groups of floating wind turbines may comprise only two floating wind turbines.

In any example of the disclosure, each of the groups of floating wind turbines may comprise only two floating wind turbines.

Alternatively, in any example of the disclosure, at least one of the groups of floating wind turbines may further comprise a third floating wind turbine connected to the second floating wind turbine by a power cable.

In some examples of the disclosure, each of the groups of floating wind turbines may further comprise a third floating wind turbine connected to the second floating wind turbine by a power cable.

From a second aspect, the present disclosure provides a floating windfarm connection architecture comprising one or more wind turbine arrays according to any example of the disclosure.

In any example of the disclosure, the floating windfarm connection architecture may further comprise a subsea transformer, wherein the or each subsea power hub is connected to the subsea transformer by a respective power cable. In any example of the disclosure, the floating windfarm connection architecture may comprise three wind turbine arrays according to any example of the disclosure.

In any example of the disclosure, the power cable(s) connecting the or each subsea power hub to the subsea transformer may be a static power cable.

From a further aspect, the present disclosure provides a floating windfarm comprising two or more floating windfarm connection architectures according to any example of the disclosure.

From a still further aspect, the present disclosure provides a subsea power hub for use with a floating windfarm, the subsea power hub comprising: a plurality of connectors for connecting the subsea power hub to each of a plurality of power cables connected to respective wind turbines; and a further connector for connecting the subsea power hub to a power cable connected to a subsea transformer.

In any example of the disclosure, the subsea power hub may be configured to combine inputs received from the plurality of respective wind turbines via the plurality of connectors and to output the combined inputs via the further connector.

In any example of the disclosure, the subsea power hub may comprise three or more connectors for connecting the subsea power hub to each of three or more respective wind turbines, or may comprise four or more connectors for connecting the subsea power hub to each of four or more respective wind turbines, or may comprise four or five connectors for connecting the subsea power hub to each of four or five respective wind turbines.

In any example of the disclosure, at least one of the connectors may be a wet mate connector.

In any example of the disclosure, the subsea power hub may further comprise a watertight housing, wherein each of the connectors and the further connector are configured to provide an electrical connection between a respective power cable extending external of the housing and the interior of the housing.

From a still further aspect, the present disclosure provides a wind turbine array according to any example of the disclosure, or a floating windfarm connection architecture according to any example of the disclosure, or a floating windfarm according to any example of the disclosure, wherein the subsea power hub is a subsea power hub according to any example of the disclosure.

Features described in relation to one aspect of this disclosure may of course be applied to the further aspects thereof. In general, features of any example described herein may be applied wherever appropriate to any other example described herein. Where reference is made to different examples or sets of examples, it should be understood that these are not necessarily distinct but may overlap.

Although certain advantages are discussed below in relation to the features detailed above, other advantages of these features may become apparent to the skilled person following the present disclosure.

BRIEF DESCRIPTION OF DRAWINGS

Certain non-limiting examples of the disclosure will now be described by way of example only and with reference to the accompanying drawings in which:

Figure 1 is a schematic view of a floating windfarm connection architecture in accordance with an example of the present disclosure;

Figure 2 is a schematic view of a wind turbine array of a floating windfarm connection architecture in accordance with another example of the present disclosure;

Figure 3 is a perspective view of a subsea power hub according to one example of the disclosure; and Figure 4 is a schematic diagram showing the internal connections formed in a subsea power hub according to another example of the disclosure.

DETAILED DESCRIPTION

Referring to Figure 1, a floating windfarm connection architecture 2 for a floating windfarm 3 (in other words, a power distribution system topology or layout for the windfarm 3) is schematically shown. The floating windfarm 3 shown in Figure 1 consists of two floating windfarm connection architectures 2 located adjacent each other. It will be understood that in many applications, a larger number, potentially significantly larger, of floating windfarm connection architectures 2 may be provided in a windfarm 3 and that the number of repeating floating windfarm connection architectures 2 will depend on the energy output required from the windfarm 3, amongst other factors. Each floating windfarm connection architecture 2 includes a number of individual wind turbines 4. The wind turbines 4 are floating offshore wind turbines of a standard type. Different types and sizes of wind turbines may be used as desired. In one example, the wind turbines used may be a commercially available 14MWwind turbine or similar.

The floating windfarm connection architecture 2 is made up of one or more wind turbine arrays 6a-6c. In any example of the disclosure, each wind turbine array 6c includes a subsea power hub 8 and a plurality of groups 10 of floating wind turbines 4. Each group 10 of floating wind turbines 4 includes a first floating wind turbine 4a connected to a second floating wind turbine 4b by a dynamic power cable 12. Each group 10 of floating wind turbines is connected to the subsea power hub 8 by a dynamic power cable 14 extending between the first floating wind turbine 4a and the subsea power hub 8.

In the example shown in Figure 1, the floating windfarm connection architecture 2 is made up of three wind turbine arrays 6a-6c connected in parallel with a transformer 16 as will be described in further detail below. It will be understood however that any suitable number of wind turbine arrays for a required power output and location could be provided in each floating windfarm connection architecture 2 and connected either in parallel or series with the transformer. It will be understood that the size of transformer available and the size of the power transmission cables will both limit the number of wind turbine arrays provided in each floating windfarm connection architecture 2 and connected to the transformer. Further, if required, different numbers of wind turbine arrays could be provided in different floating windfarm connection architectures within the windfarm.

Although the number of wind turbines in each wind turbine array may be varied, in the example shown in Figure 1 , each wind turbine array 6a-6c includes four groups 10 of floating wind turbines 4. Each group 10 of floating wind turbines 4 includes a first floating wind turbine 4a connected to a second floating wind turbine 4b by a dynamic power cable 12. Each group 10 of floating wind turbines is connected to the subsea power hub 8 by a dynamic power cable 14 extending between the first floating wind turbine 4a and the subsea power hub 8. It will be understood that in other examples of the disclosure, other types of cable may be used but dynamic cable, i.e. cable which is capable of moving under water and is fixed only at its points of connection is used in various examples including those shown.

In other examples of the disclosure each wind turbine array may include any of two, three, four, five or more groups of floating wind turbines. The provision of four or five groups of floating wind turbines in each wind turbine array may provide better efficiency both in terms of CAPEX and OPEX costs of the floating windfarm provided.

A wind turbine array according to an alternative example of the disclosure is shown in Figure 2. It will be understood that, as for the example of Figure 1 , the number, arrangement and types of wind turbine arrays provided in a windfarm connection architecture may be varied as desired. In the example of Figure 2, the wind turbine array 206 includes five groups 210 of floating wind turbines 204. Each group 210 of floating wind turbines 204 includes a first floating wind turbine 204a connected to a second floating wind turbine 204b by a dynamic power cable 212. Each group 210 of floating wind turbines is connected to the subsea power hub 208 by a dynamic power cable 214 extending between the first floating wind turbine 204a and the subsea power hub 208.

As described above and shown in Figures 1 and 2, each group of floating wind turbines in a wind turbine array 6a-6c, 206 is connected to the subsea power hub 8, 208 by a dynamic power cable 14, 214 and each floating wind turbine 4a, 4b, 204a, 204b in each group 10, 210 is connected to another wind turbine 4a, 4b, 204a, 204b in that group by a dynamic power cable 12, 212. The material and manufacturing costs of the dynamic power cables form a significant part of the CAPEX cost of any floating windfarm power distribution system. A larger diameter cable is required to carry higher currents. Thus, in previous arrangements in which significant numbers of wind turbines are connected in series, a much larger diameter of dynamic power cable is required at one end of the series of wind turbines than the other. There is considerable expense involved in manufacturing dynamic cable of different diameters but using the largest diameter cable required to connect all wind turbines in the series is also inefficient due to the material costs of the cable.

By using the floating windfarm connection architecture according to the disclosure, the CAPEX costs of a windfarm can be reduced as dynamic cable of a constant diameter can be used more efficiently throughout the windfarm architecture. This is further optimised for architectures according to the disclosure in which four or five groups of floating wind turbines are provided in each array. This is optimised still further when each of the groups of floating wind turbines comprises only two floating wind turbines and still further when a 66kV dynamic cable is used throughout each array. By using the same diameter of static power cable as described, the CAPEX costs of a windfarm can be reduced as static cable of a constant diameter can be used more efficiently throughout the windfarm architecture.

It will further be understood that static cable is much less expensive than dynamic cable of the same diameter, partly as there is no need to attach buoyancy to the static cable which runs along the seabed as opposed to dynamic cable which must float in the sea. Thus, the use of static cable for connecting the or each subsea power hub to the or each transformer will further reduce the CAPEX costs of a windfarm.

Figure 4 is a schematic diagram showing the internal connections in a subsea power hub according to another example of the disclosure. In the example of Figure 4, a schematic representation of a subsea power hub 408 suitable for connecting to two wind turbine arrays is shown. As described above, the subsea power hub 408 forms a junction box for connecting to two power cables in a subsea environment. The subsea power hub 408 includes a watertight housing 450. In at least some examples of the disclosure, the housing 450 may be filled with oil and I or may be pressure compensated to further seal against water ingress.

In the example shown, a first WM connector 452a is provided on the subsea power hub 408 for connecting to corresponding WM connector 454a provided on a dynamic cable or input cable 414a connected to one of the groups of wind turbines (not shown in Figure 4) in an array. In the arrangement shown, the WM connector 452a on the subsea power hub 408 is a male connector configured to receive a female connector, for example connector pins of the corresponding WM connector 454a provided on the dynamic cable 414a. In addition, a second DM connector 452b is provided on the subsea power hub 408 for connecting to a corresponding DM connector 454b provided on a dynamic cable or input cable 414b connected to another one of the groups of wind turbines (not shown in Figure 4) in an array. In the arrangement shown, the DM connector 452b on the subsea power hub 408 is a male connector configured to receive a female connector, for example connector pins of the corresponding DM connector 454b provided on the dynamic cable 414b. As seen in Figure 4, the subsea power hub 408 is configured to combine each phase of the power input from each of the input cables 414a-b and to output each combined phase of the power input via the output cable 418. It will be understood that a subsea power hub having any suitable number of input cables, connected via any combination of WM and DM connectors to the subsea power hub could be provided.

In the example of Figure 4, the subsea power hub 408 further includes a connector (typically a DM connector) 456 for connecting with a corresponding connector 458 on a power cable or output cable 418 (typically a static cable) extending between the subsea power hub 408 and a transformer (not shown in Figure 4).

The power hub typically provides means to support/assist the pull-in and connection of WM connectors. The power hub may be equipped with additional signal connectors (electrical or optical) for communication signals and/or auxiliary power supply that connects to communication and/or auxiliary power wires included in the power cables 414a, 414b and 418. For example, an optical junction box 460 may be provided for connecting via WM or DM connectors to auxiliary cables 462a-c provided in the power cables as shown. In the example shown, an optical WM connector 464a, 464b is provided for connecting each of the auxiliary cables 462a-b of the input cables 414a, 414b to the auxiliary cable 462c of the output cable 418.

The power hub may be equipped with internal sensors to monitor its performance. It may also be equipped with the ability to remotely control the WM connectors between electrically connected and disconnected states.

Further, the power hub may be designed with the ability to replace the subsea power hub (including the housing and the connectors provided on the housing) after the WM connectors have been disconnected, but with the cables including their connector halves still mechanically attached to the power hub structure.

Using the floating windfarm connection architecture according to the disclosure, it is possible to disconnect or reconnect any one or more groups of wind turbines from/to the floating windfarm at any time as required. Thus, if a wind turbine fails or requires maintenance, the group of wind turbines to which it belongs can be disconnected from the subsea power hub within a wind turbine array and either kept in position or removed from the windfarm. The remaining wind turbines in the windfarm and the wind turbine array will continue to operate and to provide energy via the subsea power hub at optimum efficiency. Further, if desired a new group of wind turbines can replace the group containing the failed wind turbine in a straightforward manner at any time.

While the disclosure has been described in detail in connection with only a limited number of examples, it should be readily understood that the disclosure is not limited to such disclosed examples. Rather, the disclosure can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the scope of disclosure. Additionally, while various examples of the disclosure have been described, it is to be understood that aspects of the disclosure may include only some of the described examples. Accordingly the disclosure is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.