GB2464306A

GB2464306A - Turbine array

Info

Publication number: GB2464306A
Application number: GB0818620A
Authority: GB
Inventors: Paul Fletcher
Original assignee: Rolls Royce PLC
Current assignee: Rolls Royce PLC
Priority date: 2008-10-13
Filing date: 2008-10-13
Publication date: 2010-04-14
Also published as: GB0818620D0

Abstract

An array of turbine units 10 comprises at least two units 12 each having a single turbine 14 mounted to a single stanchion 16, wherein alternate (adjacent) turbines 12A, 12B rotate in opposite directions. Blade tips 18 of adjacent turbines may rotate within one turbine diameter of each other, and preferably within 0.1 to 0.5 (half) a turbine diameter of each other. The array of turbine units 10 may be arranged in a substantially continuous straight or arced line. The turbines 14 may comprise blade pitch change mechanisms for reverse flow, wherein alternate turbines 12A, 12B operate in forward and reverse configurations to form a handed array. The turbines 14 may be tidal turbines.

Description

TIDAL TURBINE ARRAY

The present invention relates to an array of tidal turbines for power generation.

An array of tidal turbine units or farm' is normally arranged such that each turbine is in a substantially linear format to avoid vortices/wakes from an otherwise upstream turbine interfering with a downstream turbine.

Vortices impinging on a turbine can cause damage to the blades, housings and generation mechanisms.

A known turbine unit comprising a single turbine and its generator is mounted on a single stanchion. In this case, an array of these turbine units is arranged in-line and their turbines all rotate in the same direction. This ensures parts count' commonality, which benefits unit cost and logistics including spare parts holding. These in-line single rotor units are spaced at least and typically one turbine rotor diameter apart. This is to avoid harmful turbine rotor wake interactions generated by adjacent turbines. At the point of closest approach, blade tips from adjacent units pass one another with a relative velocity of twice their normal rotational speed.

w02004/048,774 discloses a double turbine unit comprising a single stanchion with two turbines mounted thereon. The two turbines rotate in opposite directions to one another. This is commonly called handing'. The main reason for this handing is to balance torque loads from each turbine. For movable turbine unit configurations, such as a buoyant kite' e.g. CB2441821, other factors limit the rotor spacing.

Thus the number of units in an array is limited by their spacing and hence total power output of an array in a given location is relatively limited. Since many of the costs of installing a tidal array or farm are fixed, it is desirable for the overall cost per installed kW output to be decreased.

Single turbine, single stanchion units have several advantages over double turbine units. A failure of either half of a double unit requires shut down of both halves, i.e. double the loss of capacity. Also, double structures are typically larger than single stanchion units and significantly more elaborate, hence less easy to install and maintain.

Therefore it is an object of the present invention to provide a higher density power output tidal farm using single turbine, single stanchion units.

In accordance with the present invention there is provided an array of turbine units comprising at least two units each having a single turbine mounted to a single stanchion wherein alternate turbines rotate in opposite directions.

Preferably, the turbines comprise blade tips and the blade tips of adjacent turbines rotate within one turbine diameter of each other. More specifically, blade tips rotate between 0.1 and 0.5 turbine diameters of each other.

Preferably, the turbine units are arranged substantially in a continuous line in either a straight or arcuate line in plan.

Alternatively, the turbine units comprise blade pitch change mechanisms for reverse flow and alternate turbines operate in forward and reverse configuration to form a handed array.

In another aspect of the present invention there is provided a method of operating an array of turbine units comprising at least two units each having a single turbine mounted to a single stanchion wherein alternate turbines rotate in opposite directions, the turbine units comprises blade pitch change mechanisms for forward and reverse flow conditions; the method comprises the step of operating alternate turbines in forward and reverse configuration to form a handed array.

As suitable tidal turbine array sites are particularly rare, because of other marine activity and wildlife considerations, it is of the utmost significance that the present invention maximises power generation density.

The present invention will be more fully described by way of example with reference to the accompanying drawings in which: Figure 1 is a schematic view of part of an array of tidal turbine unit in accordance with the present invention.

With reference to Figure 1, an array of turbine units comprises a number of turbine units 12A, 12B each having a single turbine 14 mounted to a single stanchion 16.

Alternate turbines 12A, 12B rotate in opposite directions.

The turbines 12 comprise blades 17 having tips 18.

The turbine units 12A, 12B are located relative to one another such that the blade tips of adjacent turbines rotate within one diameter 20 of each other. Depending on blade shape and tip speed of the blade tips of adjacent turbines are preferably positioned to rotate between 0.1 and 0.5 diameters of each other.

Depending on ocean or estuary bed topography and local tidal flow patterns, the turbine units are arranged substantially in a continuous and straight line (in plan) Alternatively, where bed topography dictates and/or tidal flow direction varies across the farm, the continuous line may be arcuate in plan, but still at least a number of the units are within at most one diameter of one another.

For these single turbine rotor units, two versions are produced in which the blades rotate in opposite directions and comprise mirror image' designs for the following, as appropriate: blade profiles; gearbox/transmission; generator/power electronics system; stanchion structure to reflect the opposite torque loads. Other consideration to reduce mirror image' designs may include gearboxes with an additional stage which could be incorporated to restore the rotational direction of the drive into a standardised a]ternator for power generation. Hydraulic transmsson could also be used, where the motors are handed' to restore the rotational direction of the drive into the alternator.

It is well known, e.g. W02005/103,484A2, for tidal turbines to accommodate flow reversal (the change in tide direction) via pitch change blade mechanisms. In this design, a pitching motor rotates the entire blade about an axis at which it joins its hub.

It is possible for the array of handed turbines of the present invention to be reversible and therefore identical, but for alternate units to have their turbines in 4reverse' and forward' modes. Thus a method of operating this array of turbine units comprises the step of operating alternate turbines in forward and reverse configuration to form a handed array.

It is also well known for tidal turbines to accommodate flow reversal by turning the part of the structure that mounts the turbine (typically the nacelle) This typically does not impact minimum blade spacing, but theoretically could do depending on where the axis of turning is located.

Generator/power electronics systems can easily be designed to work equally well with either rotational direction. The power electronics typically converts the generators electrical output to the voltage and frequency desired for transmission.

The present invention is not without compromise particularly in parts count commonality, which impacts unit cost and logistics, including spares holding. However, these disadvantages can be minimised where high numbers of units are manufactured and employed. As suitable tidal turbine array sites are particularly rare, because of other marine activity and wildlife considerations, it is of the utmost significance that the renewable power generation is maximised.

Claims

Claims: 1. An array of turbine units (10) comprising at least two units (12) each having a single turbine (14) mounted to a single stanchion (16) wherein alternate turbines (12A, 12B) rotate in opposite directions.
2. An array of turbine units (10) as claimed in claim 1 wherein the turbines (14) comprise blade tips (18) and the blade tips (18) of adjacent turbines rotate within one turbine diameter (20) of each other.
3. An array of turbine units (10) as claimed in claim 1 wherein the turbines (14) comprise blade tips (18) and the blade tips of adjacent turbines rotate between 0.1 and 0.5 turbine diameters (20) of each other.
4. An array of turbine units (10) as claimed in any one of claims 1-3 wherein the turbine units are arranged substantially in a continuous line.
5. An array of turbine units (10) as claimed in claim 4 wherein the continuous line is straight in plan.
6. An array of turbine units (10) as claimed in claim 4 wherein the continuous line is arcuate in plan.
7. An array of turbine units (10) as claimed in any one of claims 1-3 wherein the turbine units comprises blade pitch change mechanisms for reverse flow and alternate turbines operate in forward and reverse configuration to form a handed array.
8. A method of operating an array of turbine units (10) (10) comprising at least two units (12) each having a siricjle turbirae (14) mounted to a sinicjle stanchion (16) wherein alternate turbines (12A, 12B) rotate in opposite directions, the turbine units comprises blade pitch change mechanisms for forward and reverse flow conditions; the method comprises the step of operating alternate turbines in forward and reverse configuration to form a handed array.
9. An array of turbine units substantially as described in this specification and with reference to and as shown in figure 1.