GB2543262A

GB2543262A - Turbine system

Info

Publication number: GB2543262A
Application number: GB1517750.4A
Authority: GB
Inventors: Penfold William
Original assignee: Individual
Current assignee: Individual
Priority date: 2015-10-07
Filing date: 2015-10-07
Publication date: 2017-04-19
Also published as: WO2017060732A1; GB201517750D0

Abstract

A water turbine system comprises a Savonius turbine 10 with a barrier 30 arranged to shield a returning blade 22 of the turbine 10 from a fluid flow (arrow). The barrier 30 has a curved surface that faces the returning blade. This system provides improved efficiency for power generation and the like. Alternatively Savonius turbines may be arranged in arrays which are offset from each other as viewed in the flow direction (figure 41). An array of turbines may be positioned close together to create a blocking effect, potentially increasing efficiency beyond the Betz limit. A turbine array may be located outwards of a headland.

Description

TURBINE SYSTEM

This invention relates to a turbine system.

BACKGROUND

Moving fluids such as rivers, estuaries and tidal flows remain an underutilised resource for generating electrical power.

Currently tidal turbines are used in high flow regions where the flow rate is in the range 2.3-3m/s or upwards. Such locations present issues with connection to the National Grid. In view of these difficulties, only are small proportion of the potential of tidal power is being realised.

Hydroelectric systems that extract energy from river or other inland water systems generally employ a dam and create a large hydrostatic head. For example hydrostatic heads in excess of 20 meters are commonly used although lower heads in the range 3-10 m have also been employed. Hydroelectricity can also be generated in “Run of River” (ROR) environments in which little water storage is provided.An overriding cost for the implementation of hydroelectric power systems is the cost of installation. In order to obtain economies of scale, turbine systems are normally implemented as part of a large infrastructure project. Such projects often require a large quantity of concrete to be laid to support the turbines and associated machinery and/or energy harvesting infrastructure. Implementing conventional turbine systems therefore represents a large investment. Additionally, such systems are not suitable for shallow water flows. Currently, there are few cost effective solutions for harvesting energy from environments where there is a low hydrostatic head (less than 2 meters) or no hydrostatic head at all, i.e. ROR environments. ROR projects need to take into consideration environmental impacts on fish and aquatic organisms and the impact of access roads and transmissions lines associated with the ROR installation. DE 102011100630 A1 relates to a Savonius wind turbine in which an obstacle is placed close to the returning blade of the turbine and a deflector is placed close to the advancing blade of the turbine. US 4,715,776 A describes a Savonius wind turbine that uses a deflector plate device to increase the power output of the turbine. US 20100247320 A1 describes a twisted blade Savonius wind turbine, US 4,830,570 A relates to a wind turbine system that uses a combination of two Savonius rotors mounted on a support structure with a deflector plate. WO 2012127196 A1 describes a Savonius wind turbine that can be used in a fence of such turbines. US2011211956 A1 describes a matrix of Savonius wind turbines. US 2008116692 describes a floating pontoon that carries an array of horizontally oriented Savonius turbines. US 2008/145991 describes a horizontal water turbine

SUMMARY

Aspects and embodiments of the invention are set out according to the appended claims.

An aspect of the invention provides a turbine system comprising: a first Savonius turbine; and a barrier arranged to shield a blade of the turbine from a fluid flow, the blade being a returning blade when the turbine is operated in the fluid flow, wherein the barrier has a surface that faces the returning blade that comprises a curved surface.

The fluid flow is typically a water flow. The water flow may be provided by a channel such as a river, an estuary or a man-made channel such as a canal or other conduit. The water flow may be a tidal water flow.

An aspect of the invention provides a turbine installation comprising an array of Savonius turbines that spans a channel so as to create a blockage effect. The blockage effect acts to increase the efficiency of each of the turbines in the array of turbines.

BRIEF DESCRIPTION OF DRAWINGS

There now follows, by way of example only, a detailed description of embodiments of the present invention with reference to the accompanying drawings in which:

Figure 1 is a perspective view of a Savonius turbine;

Figure 2 is a perspective view of another Savonius turbine;

Figure 3 is a plan view of the turbine illustrated in Figure 2;

Figure 4 is a plan view a three-bladed Savonius turbine;

Figure 5 illustrates a twisted two-bladed Savonius turbine;

Figure 6 illustrates a twisted three-bladed Savonius turbine;

Figure 7 is a plan view of a turbine system comprising a Savonius turbine and a barrier;

Figure 7a is a plan view of the turbine system of figure 7 illustrating the wake produced by the barrier;

Figure 8 illustrates low and high pressure regions with respect to the system illustrated in figure 7 ;

Figure 9 illustrates a system comprising a barrier which has planar upstream surfaces and a downstream surface that has a curved surface that follows the arc of a circle;

Figure 10 illustrates a system comprising a barrier which has concave upstream surfaces and a downstream surface that has a curved surface that follows an arc of a circle;

Figure 11 illustrates a system comprising a barrier which has an upstream surface that follows the arc of an oval and a downstream surface that has a curved surface that follows an arc of a circle;

Figure 12 illustrates a system comprising a barrier which has an oval cross-section;

Figure 13 illustrates a system comprising a barrier which has an upstream surface that has a curved surface that follows an arc of a circle and a downstream surface that has a curved surface that follows an arc of an oval;

Figure 14 illustrates a system comprising a barrier which has an upstream surface that follows the arc of a first circle that has a first radius and a downstream surface that follows the arc of a second circle having a second radius that is different to the first radius;

Figure 15 illustrates a system comprising a barrier which has flat upstream surfaces, a downstream surface that has a curved surface that follows an arc of a circle and an elongated section between the upstream and downstream surfaces;

Figure 16 illustrates a system comprising a barrier which has planar upstream surfaces and a downstream surface that has a curved surface that follows an arc of a circle, the barrier having an elongated section between the upstream and downstream surfaces;

Figure 17 illustrates a system comprising a barrier which has an upstream surface that follows the arc of an oval and a downstream surface that has a curved surface that follows the arc of a circle, the barrier having an elongated section between the upstream and downstream surfaces;

Figure 18 illustrates a system comprising a barrier which has an upstream and downstream surface that each follow the arc of a circle, the barrier having an elongated section between the upstream and downstream surfaces;

Figure 19 is a plan view of a turbine system comprising a Savonius turbine and a barrier in which the lateral offset, with respect to a flow, between the barrier and the turbine is set to different degrees;

Figure 20 is a plan view of a turbine system comprising a Savonius turbine and a barrier in which the offset in a flow direction between the barrier and the turbine has been set to different degrees;

Figure 21 is a plan view of a turbine system comprising two adjacent Savonius turbines arranged to counter rotate and to exhibit a time lag between when the returning blade of each turbine is traverse to a fluid flow; .

Figure 21a is a plan view of a turbine system comprising two adjacent Savonius turbines arranged to counter rotate and for the returning blade of each turbine to be traverse to a fluid flow at the same time as each other;

Figure 22 is a plan view of a turbine system similar to that illustrated in Figure 21a except that the turbines are spaced apart from each other in the direction of the flow;

Figure 23 is a plan view of a turbine system comprising two adjacent Savonius turbines and a barrier located between the turbines;

Figure 24 illustrates the turbine system of Figure 24 deployed in a channel;

Figure 25 is a plan view of a turbine system comprising two adjacent Savonius turbines, each turbine having a barrier located to the side of the turbine in a direction traverse to a fluid flow and on a side of the turbine opposite to the other turbine, the turbines being arranged to counter rotate and for the returning blade of each turbine to be traverse to a fluid flow at the same time as each other;

Figure 26 is a plan view of a turbine system similar to that illustrated in Figure 25 except that the turbines exhibit a time lag between when the returning blade of each turbine is traverse to a fluid flow;

Figure 27 is a plan view of a turbine system similar to that illustrated in Figure 25 except that the turbines are offset in a first direction traverse to the fluid flow;

Figure 28 is a plan view of a turbine system similar to that illustrated in Figure 25 except that the turbines are offset in a second direction traverse to the fluid flow;

Figure 29 is a side cross-sectional view of a channel and an array of vertical Savonius turbines spanning the channel;

Figure 30 is a side cross-sectional view of an infrastructure spanning a channel and an array of vertical Savonius turbines housed within the infrastructure;

Figure 31 is a plan view of a turbine system installed in a channel that has turbines adjacent to the channel sides;

Figure 32 is a plan view of an extended turbine system installed in a channel that has turbines adjacent to the channel sides;

Figure 33 is a plan view of a turbine system installed in a channel that has barriers adjacent to the channel sides;

Figure 34 is a plan view of a turbine system similar to that illustrated in Figure 33 except that there are sluice gates disposed between the barriers and the channel sides;

Figure 35 is a plan view of a first type of turbine module;

Figure 36 is a plan view of an installation of a plurality of the first type turbine modules illustrated in figure 35;

Figure 37 is a plan view of a second type of turbine module;

Figure 38 is a plan view of an installation of a plurality of the second type turbine modules illustrated in figure 37;

Figure 39 is a plan view of a third type of turbine module;

Figure 40 is a plan view of an installation of a plurality of the third type turbine modules illustrated in figure 39;

Figure 41 is a plan view of a two linear turbine arrays that traverse a channel with the turbines of one array rotating in the same direction as the turbines of the other array;

Figure 42 is a plan view of two linear turbine arrays that traverse a channel with the turbines of one array counter rotating with respect to the turbines of the other array;

Figure 43 is a plan view of an array of turbines and barriers arranged in a first flow direction;

Figure 44 is a plan view of an array of turbines and barriers arranged in a second flow direction that is opposite to first flow direction illustrated in Figure 43;

Figure 45 is a plan view of two linear turbine arrays disposed from a headland or promonitory;

Figure 46 is a side cross-sectional view of a horizontal Savonius turbine deployed in a fluid flow together with a barrier deployed below the turbine;

Figure 47 is a side cross-sectional view of two horizontal Savonius turbines deployed in a fluid flow together with a barrier deployed between the turbines;

Figure 48 is a side cross-sectional view of two horizontal Savonius turbines deployed in a fluid flow, the turbines being spaced apart in the direction of the flow and rotating in the same direction;

Figure 49 is a side cross-sectional view of two horizontal Savonius turbines deployed in a fluid flow, the turbines being spaced apart in the direction of the flow and counter rotating;

Figure 50 shows the turbines arrangement of Figure 48 operating in two different flow directions;

Figure 51 shows the turbines arrangement of Figure 49 operating in two different flow directions;

Figure 52 is a side cross-sectional view of an infrastructure spanning a channel and an array of horizontal Savonius turbines housed within the infrastructure;

Figure 53 is a side cross-sectional view of an infrastructure spanning a channel and an array of vertical Savonius turbines and a horizontal Savonius turbine housed within the infrastructure; and

Figure 54 is a plan view of an arrangement of turbines configured to operate in both a fluid flow that has a first flow direction and in a fluid flow that has a second flow direction that is opposite the first flow direction.

DETAILED DESCRIPTION

Figure 1 illustrates a standard Savonius turbine 10 that comprises two rotor blades 20 in the form of scoops. When placed in a fluid flow the drag of the flow on the blades 20 causes the blades 20 to rotate.

Figure 2 illustrates a Savonius turbine 10 in which the blades 20 of the turbine are in a configuration that is a reflection of the configuration of blades 20 illustrated in Figure 1. The turbine 10 is also illustrated as having end plates 24. The flow that impinges on the turbine 10 is represented by a solid arrow. The blade that is being pushed forward by the flow is termed the “advancing blade” 21 and the blade that moves back against the flow is termed the “returning blade” 22.

Although figures 1 and 2 illustrate turbines that have blades 20 that are rotated through 180° with respect to each, other higher degrees of rotation can be used.

Figure 3 is a plan view of the turbine 10 illustrated in Figure 2. Although two rotor blades 20 are illustrated a higher number of blades 20 can be employed, for example, three rotor blades 20 are commonly used. Figure 4 is a plan view of a turbine 10 that has three blades 20.

Figures 5 and 6 illustrate twisted-type Savonius turbines 10 which have two and three blades 20 respectively. In the examples illustrated the turbines 10 are twisted into a helical form. In Figure 5 the blades 20 are twisted by 180° relative to each other whereas in Figure 6 the turbine blades 20 are twisted by 120° relative to each other.

The use of twisted blades reduces torque fluctuations and enables the turbine 10 to self-start, that is, they do not require an additional motive force to enable the blades 20 to rotate. If the turbine 10 is orientated vertically then faster flowing surface water can be directed downwards by the twisted blade 20 so that the torque across the blade 20 is evened out.

Figure 7 illustrates a barrier 30 placed upstream of the returning blade 22 of a Savonius turbine 10. The figure is a plan view and the rotational axis of the turbine 10 is orientated vertically. The turbine 10 will generally be elongated in a similar way to that illustrated in figure 2 such that the longitudinal axis of the turbine 10 will coincide with its rotational axis. The barrier 30 acts as a shield in front of the returning blade 22 of the turbine 10. Generally, the barrier 30 will also be elongate so that it can act as a barrier along some or all of the length of the returning blade 22. In one specific embodiment the barrier 30 takes the form of a tube or column.

The barrier 30 illustrated in Figure 7 has a cross-section that is circular but, as discussed below, the barrier 30 may have a cross-section with a different geometry.

Figure 7a illustrates a zone of interference 32 that trails downstream from a barrier 30. The zone of interference represents a low pressure region. The zone of interference 32 is, in effect, the wake of the barrier 30. The upstream boundary 36 of the zone of interference 36 will generally be visible as a standing wave or “bow wave”. The extent of the zone of interference 34 its shape will be dependent on the flow velocity and the shape of the barrier 30. For a circular barrier, the zone of interference 32 has a generally conical shape. The dimensions and position of the barrier 30 are chosen so that a portion of the zone of interference 34 is upstream of the returning blade 22 but does not significantly interfere with the advancing blade 21. That is, the zone of interference does not significantly overlap with the zone upstream of the advancing blade 21.

As illustrated in figure 8, a region of low pressure is created on the downstream side of the barrier 30. The low pressure region is in front of the returning blade 22 so that there is less resistance to the returning blade 22 than would otherwise be the case. As such, the barrier 30 assists the motion of returning blade 22. In figure 8, the low pressure region is labelled “L” and a high pressure region in front of the advancing blade 21 is labelled “H”.

The barrier 30 could be placed directly in front of the returning blade 22 so that the barrier 30 shields the entire front cross-section of the returning blade 22 from the oncoming flow. However, as is illustrated in figure 7, larger increases in efficiency can be achieved if the barrier 30 is offset to one side of the turbine 10 (i.e. laterally offset with respect to the flow). Further gains in efficiency are achieved if rounded/curved barriers are used.

The use of a barrier 30 that has a downstream surface that is curved enables the low pressure area, L, to be mobile. In particular, the low pressure area can move as the turbine 10 rotates and the low pressure area can remain in front of the returning blade 22 along a greater portion of its return path. This is illustrated in Figure 8 with the low pressure region moving upstream as the returning blade moves upstream. Hence the returning blade meets less resistance for more of its travel with a consequent improvement in efficiency.

Barriers that have curved surfaces also produce low levels of turbulence, compared to non-curved surfaces. This reduction in turbulence also assists the rotation of the turbine 10.

The barrier 30 shown in figures 7 and 8 has a generally circular cross-section; however, barriers having other geometries which comprise a curved downstream surface could also be used. Such curved surfaces also provide the benefit of allowing the low pressure region, L, to become mobile and move in synchrony with the returning blade. Examples of such barriers are illustrated in figures 9-18 and have a convex surface on the downstream side of the barrier 30.

Figures 9-11 illustrate barrier embodiments in which the downstream surface of the barrier 30 is defined by a curve that takes the form of an arc of a circle whilst the upstream surface takes another form. For example, the upstream surface may comprise straight surfaces, comprise concave arcs, or comprise an arc of an oval as illustrated in figures 9, 10 and 11 respectively. Figure 12 illustrates an example in which both the front (upstream) surface and the rear (downstream) surface have an oval geometry. Figure 13 illustrates an example in which the rear surface has an oval shape and the front surface is defined by an arc of a circle. Figure 14 illustrates a barrier 30 in which the front and rear surface are defined by arcs having different radii of curvature - as such the cross-section of the barrier is represented as the intersection of two overlapping circles of different sizes. In the example illustrated in Figure 14, the rear surface comprises an arc that forms a half circle.

As illustrated in figures 15-18, the barrier 30 may comprises an elongated section between the front and rear surfaces of the barrier 30.

In general, a barrier 30 that has a circular or approximately circular cross-section has a less aggressive intervention on the flow than other shapes. Such a shape will have a reduced wake and the wake will be less turbulent compared to other shapes. Reduced turbulence in downstream flows is particularly important when boosting the efficiency of an array of turbines (in comparison to a single turbine).

Circular/tubular barriers are fairly easy to manufacture and are structurally reliable. Circular/tubular structures are widely available for other applications and are manufactured in a range of different materials. Such structures could be used as barriers in embodiments of the current invention with little or no modification. Using such “off the shelf’ components as barriers would reduce the cost of implementing the invention compared to the use of bespoke barriers. For example, steel or concrete tubes that are normally used for drainage or water transportation could be utilised in embodiments of the invention.

The barriers 30 could form a part of the structure of the whole turbine installation, for example, the barriers 30 may act as piles that support a structure such as bridge or roadway or they may support energy harvesting infrastructure.

As illustrated in figure 19, the barrier 30 may be placed to one side of the turbine 10 in the lateral direction (i.e. the cross flow direction) so that the barrier 30 can be positioned to either overlap with the returning blade 22 of the turbine 10 or not overlap with the returning blade at all. In Figure 19(a) the barrier 30 is placed so that it overlaps with the returning blade 22 when the returning blade is in a position that is fully traverse to the fluid flow. For example the barrier 30 may overlap to an extent “d” in the lateral direction. In Figure 19(b) the barrier 30 is placed so that it is in line with outside edge of the returning blade 22 when the returning blade 22 is fully traverse to the fluid flow. In Figure 19(c) the barrier 30 is placed so that it does not overlap with the returning blade 22 in the traverse direction. For example the barrier 30 may be placed a distance d’ outside of the returning blade when the returning blade 22 is fully traverse to the fluid flow. The position of the barrier 30 can be chosen to produce the most useful wake, i.e. to assist the motion of retuning blade 22 whilst not significantly interfering with the advancing blade 21. The wake is affected by such factors as flow velocity, water depth and the relative sizes of the turbine 10 and barrier 30.

Figure 20 illustrates different positions of the barrier 30 relative to the turbine 10 in the flow direction. That is, the barrier 30 may be positioned at different distances in front of the turbine 10. In figure 20(a) the barrier 30 is positioned in front of the turbine 10 so that there is a clear distance between the rear surface of the barrier and the front of the turbine. In figure 20(b) the barrier 30 is positioned so that the rear surface of the barrier is in line with the front of the turbine. In figure 20(c) the barrier 30 is positioned so that the rear surface of the barrier is behind the front of the turbine but ahead of the center of rotation of the turbine.

Figure 20(d) illustrates an embodiment in which the trailing edge of the barrier 30 is behind the centre line of the turbine. The barrier 30 would still act to improve to efficiency of turbine 10 but the position of the barrier would not be ideal. In particular, as can be appreciated from figure 7a, it would not be possible to fully utilise the wake 34 from the barrier 30 since the wake 34 would only partially cover the zone in front of the returning blade 21.

The skilled person will appreciate that the various positions that the barrier 30 can take at in front of the turbine 10, as illustrated in figure 20, can be combined with the various positions that the barrier 30 can be take in the lateral direction (so that it is offset from the turbine in the direction traverse to the flow direction), as illustrated in figure 19.

Figure 21 illustrates two turbines 10 that are in close proximity alongside one another. In this arrangement there is a positive interaction between the turbines 10 and the efficiency of both turbines 10 is improved considerably. In general, the efficiency of the turbines 10 increase the closer that the turbines 10 are to each other but there is a limit to how close the turbines 10 can be for practical reasons, for example, some space is required to allow clearance for maintenance and operation of the turbine system. Also the turbines 10 may be spaced to an extent sufficient to allow passage of fish and/or aquatic mammals. The turbines 10 may be placed, for example between 0.5 and 2.5 diameters apart, between 1 and 2 turbine diameters apart, between 1.3 and 1.8 diameters apart and about 1.5 diameters apart.

The sense of rotation of the blades 20 of adjacent turbines 10 may be the same and the blades 20 may be in phase or out of phase. Figure 21 illustrates two adjacent turbines 10 that are rotating in the opposite sense (i.e. one turbine 10 is rotating clockwise and the other is rotating anti-clockwise). The blades 20 of one turbine are out of phase by 90° to the blade of the other turbine in the sense that the returning blade of one turbine is fully traverse to the water flow a quarter of a cycle before the returning blade of the other turbine is fully traverse to the water flow.

There are a number of different interactions between Savonius turbines which can be taken advantage of, and they are not limited to those where the turbines are alongside one another. Generally, the changing low and high pressure fields created by one turbine can give a boost to another turbine and vice versa. For instance, Figure 22 shows two turbines 10 that are diagonally aligned facing the fluid flow; they have opposite directions of rotation and the blades 20 are in phase. In this arrangement there is also a positive interaction between the turbines 10 but this is a different kind of interaction to that shown in Figure 19 with only the downstream turbine 10 showing a gain in efficiency. In the arrangement illustrated in figure 22, the upstream turbine acts as a barrier to create a low pressure region in front of the returning blade of the downstream turbine, the upstream turbine and also pushes a high pressure field into the path of the advancing blade of the downstream turbine.

Figure 23 illustrates two turbines 10 that can generate power independently of one other. The same barrier 30 can be used to increase the efficiency of both of the turbines 10. The turbines 10 do not have to be in phase. Indeed the turbines work more efficiently when they are “out of phase(i.e. so there would be a time delay between retuning blades of the respective turbines being fully traverse to the flow) since this allows a low pressure region that is developed downstream of the barrier 30 to move in front of the returning blade of both of the turbines 10.

Figure 24 illustrates the arrangement of Figure 23 deployed within a channel 52.

Figure 25 illustrates a design that uses two adjacent turbines 10 arranged side by side in the direction lateral to the flow direction. Each turbine 10 has a barrier 30 that boosts performance with the barrier 30 positioned on the side the turbine 10 that is opposite to the side facing the adjacent turbine 10. The turbines 10 illustrated are “in phase” and counter rotating with the turbine 10 at the top of the diagram rotating anticlockwise and the turbine 10 at the bottom of the diagram rotating clockwise. In the example illustrated, the turbines 10 are in phase in the sense that the returning blade 22 of each turbine 10 approaches its respective barrier 30 at the same time. In this respect the turbines can be said to be in sync. The turbines 10 need not be in phase in order to achieve a boost in performance. For example figure 26 illustrates the turbines 10 being “out of phase” or “out of sync”. The turbines of the arrangement illustrated in figure 25 and the turbines of the arrangement illustrated in figure 26 all receive a performance boost in comparison to the operation as a stand-alone single turbine. The performance boost is greater for the arrangement of figure 25 than it is in figure 26 The adjacent turbines do not need to be aligned so that they are side by side in the transverse direction. For example, as illustrated in Figures 27 and 28, the turbines 10 can be offset relative to each other in the flow direction.

Figure 29 illustrates an array of Savonius turbines 10 that stretches across a waterway or channel such as, for example an estuary or river. Each turbine 10 is vertically aligned - that is the rotational axis of each turbine 10 is substantially vertical. Each turbine 10 may be, for example a two or three bladed Savonius turbine 10 that may have twisted or untwisted blades 20. In the figure a twisted two blade Savonius turbine is illustrated.

Having an array of turbines 10 that spans the channel creates a blockage effect that can improve the performance of each individual turbine 10 by several hundred percent. Creating a blockage allows the turbines to draw more power from the flow and hold back water to create a water level difference (i.e. a hydrostatic head) between the upstream and the downstream sides of the turbines 10. The water level difference equates to a potential energy difference which allows the theoretical Betz limit to be ignored. The blockage effectively narrows the fluid channels and causes an acceleration of the fluid created by the difference in height of the fluid between the upstream and downstream sides of the turbines.

The blockage ratio of a turbine 10 can be defined as the ratio of the area swept by the turbine blades (i.e., the frontal area of the turbine) to the channel cross-section. High blockage ratios can be achieved with Savonius turbines because they have a rectangular cross-section with respect to the fluid flow.

Figure 29(a) illustrates a water level 40 that substantially covers the turbines 10. Figure 29(b) illustrates a lower water level 40 that causes an upper portion of the turbines 10 to protrude from the surface. Orientating the Savonius turbines 20 vertically will mean that the blockage ratio of the turbine 10 array will be maintained even if the water level in the channel changes (e.g. due to tidal flow or flooding/drought) so that the efficiency of the turbines 10 is maintained.

Arrays of Savonius turbines can be integrated into other infrastructure such as a bridges, dams or weirs. As an example, figure 30 illustrates an array of turbines 10 integrated into a bridge 50 (which may be, say, a foot, cycle, road or rail bridge). The turbines 10 may be placed within one or more channels 52, or other fluid conduits within the bridge 50 or other infrastructure. By utilising such infrastructure, the costs of deploying the turbine array can be reduced by sharing the construction, operation and maintenance costs associated with the infrastructure. Further infrastructure such as weirs and sluice gates could also be integrated for flood avoidance as necessary. Locks could also be added to maintain navigation for water craft.

Figure 31 is a plan view of a vertical Savonius array deployed in a channel 52. The array comprises four turbines 10 that traverse the channel. The turbines 10 are illustrated as a linear array. The linear array of turbines may be substantially or approximately perpendicular to the fluid flow in the channel so that the array defines the shortest distance between the channel sides 54. Alternatively, the linear array of turbines may be disposed at an angle to the fluid flow as illustrated by the dotted line in figure 31. Disposing the array at an angle may be necessary or preferred due to obstacles or other constraints on the channel sides and/or in the channel itself.

Each of the outermost turbines, labelled 10i and 10r in figure 31, is disposed between a channel wall and a barrier 30. Each of the outermost turbines 10i, 10r shares its respective barrier 30 with a neighbouring inner turbine 10. Each outermost turbine 10i, 10r can rotate independently of its neighbouring turbine. As such these turbines 10 need not be in phase with each other.

The inner turbines, labelled 10a and 10b, are not separated from each other by a barrier and can benefit from a positive interaction with each other such has been described in relation to figures 21 and 22. Generally, the inner turbines 10a, 10b counter rotate with respect to each other.

For each of the turbines 10 illustrated, the returning blade 22 is shielded from the flow thereby increasing the efficiency of the turbine 10. The barriers 30 also contribute to the blockage effect of the array to further increase the efficiency of each of the turbines 10.

The size of the turbine array can be increased so that the array may extend across the water resource. This can be achieving by adding further pairs of the inner turbines. The inner two turbines, along with an adjacent barrier 30, are illustrated in figure 31 as a unit that can be repeated n times (where n is a non-zero integer 1, 2...) to extend the array. As an example, figure 32 illustrates an array of turbines 10 that is the same as the array illustrated in figure 31 except that a further pair of inner, adjacent, turbines 10c, 10d is present in between the outermost turbines i.e. n=2.

Whilst the two turbines in each inner pair of turbines interact, one pair of turbines, e.g. 10a, 10b, will not interact with another pair of turbines, e.g. 10c, 10d, since the pairs are separated from each other by barriers 30. This means that the different turbine pairs can rotate at different velocities. This is beneficial when the flow rate varies across the extent of the channel. For example, in a straight channel, the flow rate in the centre of the channel is normally greater than the flow rate at the sides of the channel (where the channel sides have a drag effect on the flow).

Figure 33 is a plan view of a vertical Savonius turbine array deployed in a channel 52 in which barriers 30 are deployed between the turbines and the sides of the channel. In this arrangement the barriers 30 also act to increase the blockage effect and act to assist the returning blade of each of the turbines.

Figure 34 shows a similar arrangement to that illustrated in figure 32 but with the addition of sluice gates 42 between one or both of the barriers 30 and the side of the channel. The barriers can be formed as an integral part of the sluice gates. The sluice gates can be used for flow regulation, for example, for flood control.

An array of turbines and barrier can be deployed in a channel by installing a number of turbine modules with the number of turbine modules being chosen according to the width of the channel. Generally, the modules will be installed so as to span substantially all, or the majority, of the width of the channel (so as to increase the blockage effect of the turbine array).

Figure 35 illustrates a first type of turbine module 80. The module comprises two Savonius turbines 10 and a barrier 30 in an arrangement that has already been described in relation to figure 23.

Figure 36 illustrates an installation of the first type of turbine module 80 in a water channel 52. In the particular example installation illustrated, three first type turbine modules have been installed.

Figure 37 illustrates a second type of turbine module 80. The second type turbine module 80 comprises a pair of Savonius turbines (comprising a first turbine 101 and a second turbine 102) and a barrier 30. The barrier 30 is disposed to the side of one of the turbines in the turbine pair so that it is on the side of the turbine that is opposite to other turbine. In the module illustrated the barrier 30 is to one side of the first turbine 10i. Of course the module could also be defined by placing the barrier 30 to the side of the second turbine 102.

When utilised in a channel, the second type of module 80 may be deployed with an additional barrier 30a that is disposed between the module 80 and the channel side to the side of the module 80 that is opposite to the barrier 30 that is part of the module 80.

The configuration of the turbines 10 and the barrier 30 follows that which has been described in relation to figure 30. The turbines 10 and barrier 30 could also be arranged to follow the configurations illustrated in one of figures 26 to 28.

Figure 37 illustrates an installation of the second type of turbine module 84 in a water channel 52. In the particular example installation illustrated, three second type turbine modules 84 have been installed. The installation illustrated in figure 37 is similar to the installation illustrated on figures 31 and 32 except that the installations illustrated in Figures 31 and 32 use turbines adjacent to the channel sides (rather than an additional shields 30a).

Figure 39 illustrates a third type of turbine module 80. The module comprises a pair of Savonius turbines 10 (comprising a first turbine 10i and a second turbine 102) with a barrier portion 37 are disposed to the side of each turbine 10i , 102 so that the barrier portions 37 are on opposite sides of the module 80 to each other.

Figure 40 illustrates an installation of the third type of turbine module 80 in a water channel 52. When the modules 80 are placed alongside each other, the barrier portion 37 next to the second turbine 102 of a module 86 can combine with the barrier portion 37 that is next to the first turbine 10i of an adjacent module 86 so as to form a complete barrier 30. In the particular example installation illustrated, three first type turbine modules have been installed.

The installation illustrated in Figure 40 is similar to that illustrated in figure 38 except there is a barrier portion 37 situated at each end of the installed array adjacent to the channel sides rather than full barriers 20. The array of modules 86 may be supplemented by an additional barrier portions 37 that complement the barrier portions 37 at the end of the outermost modules 86 so as to provide complete barriers 30 adjacent to the channel sides 54.

Figures 41 and 42 illustrate two rows of turbines 10 that stretch across a channel. The rows increase the blockage effect and take advantage of the interactions between the turbines 10. The two rows are off-set from another in the lateral direction - this increases the blockage effect of the turbines 10 and means that one row of turbines can act as barriers for the other row of turbines.

In the arrangement illustrated in Figure 41 all of the turbines 10 are rotating in the same direction. In the arrangement illustrated in Figure 42 all of the turbines 10 in a particular row are rotating in the same but the turbines 10 of one row are rotating in a counter direction to the turbines 10 of the other row.

The turbines 10 can rotate and extract energy from the flow irrespective of the direction of the flow. This is beneficial for harvesting energy from tidal waters so that energy can be harvested throughout the day (apart from brief periods of slack tide, i.e. the time when the tide changes).

The number of turbines in each row of turbines can be chosen to suit the width of the channel where they are deployed. Also the rows may be deployed at angle to the flow/bank sides (in a similar way to the arrangement illustrated in figure 21).

Figure 43 illustrates a first arrangement of the turbines 10 and barriers 30 that is optimised for a fluid flow in a first direction whereas Figure 44 illustrates a second arrangement of turbines 10 and barriers 30 that is optimised for a fluid flow in a second direction which is opposite to the first direction. Adjacent turbines 10 in the row of turbines are counter-rotating as described hereinabove in relation to figure 31. The positioning and sense of rotation of the turbines 10 in each of the two arrangements can be the same (as is illustrated) but the position of the barriers 30 is different in each of the two arrangements. Specifically, the barriers 30 are positioned upstream of the turbines 10 so that they may barrier the returning blades of the turbines 10.

The same installation of turbines can be used in the channel to achieve either the first arrangement or the second arrangement with the barrier arrangement being altered to according to the flow direction. An opportune time to change the barrier arrangement would be at slack tide. In one scenario the barriers 30 are moved from one side of the turbine array to the other, for example, the barriers 30 may be removed by lifting them out of the flow and then lowered into the flow on the other side of the turbines 30.

In another scenario there are two sets of barriers 30 that are positioned on opposite sides of the turbine array. In this case only the barriers 30 on one side of the array are deployed at one time. For example, the barriers 30 may be retracted or stowed (e.g., lowered into the channel bed) when they are downstream of the turbines 10 and deployed (e.g., raised into the flow) when they are upstream of the turbines 10.

As described above with reference to figure 31, the size of the turbine array and its orientation with respect to the flow/channel sides can be set according to the size and geometry of the channel within which the array is deployed.

The above-mentioned turbine arrays could also be deployed so that they are only bounded by a single bank. An array can be built out from a single fixed point to create a blockage without the need to reach to the other side of the channel. The array acts effectively as a “fence” in such an arrangement. For example, the arrays could extend out from a headland or from a river bend. An example of such a deployment is illustrated in figure 45. Two arrays could be deployed, as illustrated in the figure, for tidal flows as described with reference to figures 41 and 42 or a single array could be used for a deployment in a substantially non-tidal river. The turbines could also be deployed with barriers 30 as has been described with reference to figures 23, 25-27, and 31-40..

Tidal-streams are additional resources that have the potential to be exploited for energy extraction by Horizontally Aligned Turbines (HATs). Tidal turbines are likely to be subject to shallow water flow and the rotor is significantly constrained between the sea bed and the free surface. As a result tidal turbines are subject to strong blockage effects which can significantly increase the maximum power that can be extracted from the flow by a single open turbine.

Figure 46 illustrates a Savonius turbine 10 deployed horizontally in a flow. The horizontal turbine 10 is deployed alongside a barrier 30 to increase the blockage effect of the turbine 10 and to create a low pressure region in front of the retuning blade 22. Generally, the the flow rate of the fluid is faster at the surface of the water (where it experiences less drag). To take advantage of this situation, the turbine 10 can be arranged so that the advancing blade 21 is on the surface side of the turbine 10 and the returning blade 22 is on the side of the turbine 10 that is closest to the channel bottom (e.g., closest to the sea-bed/river-bed). In this arrangement the barrier 30 will be positioned between the turbine 10 and channel bottom.

Figure 47 illustrates two turbines 10 deployed horizontally in a flow. The two turbines 10 run parallel to each other and are separated by a barrier 30.

Figure 48 illustrates two horizontal turbines 10 that rotate in the same sense whereas figure 49 illustrates two horizontal turbines 10 that are counter rotating to each other and 90° degrees out of phase. In both cases the uppermost turbine 10 has an advancing blade that rotates towards the surface of the flow.

Figures 50 and 51 correspond to figures 48 and 49 but illustrate that the turbines 10 can be operated irrespective of the direction of the fluid flow.

The horizontal turbine illustrated in figures 46 to 51 can be deployed to create a blockage in a channel or river estuary. As with the vertically aligned turbines 10 illustrated in figure 30, horizontally aligned turbines 10 can also be incorporated into infrastructure such as bridges and weirs. Such a deployment of turbines is illustrated in Figure 52.

Figure 53 illustrates a combination of vertical and horizontal turbines 10 deployed in an infrastructure such as a weir or bridge. The use of a combination of vertically and horizontally aligned arrays can be used to provide navigational access. For example, in the configuration illustrated in figure 45, navigational access may be provided over the horizontally aligned turbine 10.

Figure 54 illustrates a further configuration of turbines 10 in which three line arrays of turbines are deployed across a channel. The turbine configuration can operate irrespective of the direction of the flow of the fluid in the channel.

Although various implementations of the invention have been illustrated with barriers that have a circular cross-section, it will be appreciated that such implementations can be implemented with non-circular barriers that have a curved downstream surface, for example, a convex downstream surface. As such, the barriers discussed in relation to figures 9 to 18 can be utilised with the implementations illustrated in the other diagrams.

Claims

1. A turbine system comprising: a first Savonius turbine; and a barrier arranged to shield a blade of the turbine from a fluid flow, the blade being a returning blade when the turbine is operated in the fluid flow, wherein the barrier has a surface that faces the returning blade that comprises a curved surface.

2. The turbine system of claim 1, wherein the curved surface is a convex surface.

3. The turbine system of claim 1 or claim 2, wherein the curved surface defines an arc of a circle or an arc of an ellipse.

4. The turbine system of any previous claim wherein the Savonius turbine is a vertically orientated Savonius turbine.

5. The turbine system of claim 4 wherein the barrier is an elongate barrier that is orientated vertically.

6. The turbine system of claim 5, wherein the horizontal cross-section of the barrier is substantially circular or substantially elliptical.

7. A turbine installation module comprising the turbine system of any previous claim and a second Savonius turbine, wherein: the first and second turbines are adjacent to each other; and the barrier is disposed between the first and second turbines.

8. A turbine installation comprising: an array of turbines traversing a channel, the channel containing, or operable to contain, a liquid flow; wherein the array of turbines comprises one or more of the turbine installation modules of claim 7.

9. A turbine installation module comprising the turbine system of any one of claims 1 to 6 and a second Savonius turbine, wherein: the first and second turbines are adjacent to each other; and the barrier is disposed to the side of the first turbine that is opposite to the second turbine.

10. The turbine installation of claim 10, comprising a further barrier disposed to the side of the second turbine that is opposite to the first turbine.

11. A turbine installation comprising: an array of turbines traversing a channel, the channel containing, or operable to contain, a liquid flow; wherein the array comprises one or more of the turbine installation modules of claim 9 or claim 10. (Fig. 31-34, 37, 38}}

12. A turbine installation module comprising: the turbine system of any one of claims 1 to 6 and a second Savonius turbine, wherein the first and second turbines are adjacent to each other; a first barrier portion disposed to the side of the first turbine that is opposite to the second turbine; and a second barrier portion disposed to the side of the second turbine that is opposite to the first turbine.

13. A turbine installation comprising: an array of turbines traversing a channel, the channel containing, or operable to contain, a liquid flow; wherein: the array comprises two or more of the turbine installation modules of claim 12; and the first barrier portion of one of the two or more turbine installation modules combines with the second barrier portion of an adjacent turbine installation module to form the barrier.

14. The turbine installation or turbine installation module of any one of claims 7 to 13 wherein the first and second turbines are configured to counter rotate with respect to each other.

15. A turbine arrangement comprising: a first linear array of Savonius turbines; and a second linear array of Savonius turbines; wherein the second array is offset relative to the first array.

16. The turbine arrangement of claim 15, wherein the turbines of the second array are arranged to counter rotate relative to the turbines of the first array.

17. The turbine arrangement of claim 15, wherein the turbines of the second array are arranged to rotate in the same direction as the turbines of the first array.

18. The turbine arrangement of claim 17, wherein the turbines of the second array are arranged to rotate in phase with the turbines of the first array.

19. A turbine installation comprising an array of turbines spanning a channel so as to create a blockage effect that increases the efficiency of the individual turbines in the array.

20. The turbine installation of claim 19 comprising the turbine arrangement of any one of claims 15 to 19.

21. The turbine system, turbine installation module, turbine installation or turbine arrangement of any previous claim wherein the, or each, turbine has two, three or more blades.

22. The turbine system, turbine installation module, turbine installation or turbine arrangement of claim 21 wherein the blades of the, or each, turbine are twisted.

23. The turbine system, turbine installation module, turbine installation or turbine arrangement of claim 22, wherein the blades the, or each, turbine have a helical form.

24. An infrastructure spanning, or partially spanning, a water channel, the infrastructure comprising the turbine system or the turbine installation module of any one of previous claims.

25. The infrastructure of claim 24, wherein the infrastructure comprises (i) a bridge; (ii) a dam; (iii) a sluice gate; (iv) a weir; (v) dyke or (vi) any combination of (i) to (v).

26. A turbine installation comprising a first turbines array disposed outwardly from a headland or other promontory.

27. The turbine installation of claim 24, wherein the turbines in the first turbine array rotate in the same direction.

28. The turbine installation of claim 26 or claim 27, comprising a second turbine array wherein the turbines in the second turbine array rotate in the same direction and optionally also in the same direction as the turbines in the first turbine array..