TIMMIS, Roger, James (56 Fairgarth Drive, Kirkby Lonsdale, Carnforth Lancashire LA6 2FB, GB)
THE ENVIRONMENT AGENCY (Rio House, Waterside DriveAztec West,Almondsbury, Bristol Avon BS32 4UD, GB)
AGGIDIS, George, Athanasios (152 Windermere Road, Kendal Cumbria LA9 5EZ, GB)
TIMMIS, Roger, James (56 Fairgarth Drive, Kirkby Lonsdale, Carnforth Lancashire LA6 2FB, GB)
| CLAIMS: I An unpowered device providing an aquatic wildlife ladder giving easy passage upstream and downstream to circumvent a hydraulic obstruction, and providing a means to generate useful power from the water flowing through the device. 2 A device as in Claim 1 including a vertically mounted housing containing a substantially helical surface providing the water path and rotatable about a vertical axis. 3 A device as in any previous Claim containing a plurality of coaxial water path surfaces. 4 A device as in any previous Claim coupled directly or indirectly to an electrical generator. 5 A device as in any previous Claim where the housing is cylindrical or substantially cylindrical. 6 A device as in any previous Claim where the housing and water path surface(s) substantially take the form of sections from a cone. 7 A device as in any previous Claim where the water path surface(s) incorporate(s) texture and/or structure including without limitation channels and/or pools. 8 A device as in any previous Claim where the water path surface(s) is/are manufactured in metal and/or glass-reinforced plastic and/or a composite material. 9 A device as in any previous Claim where the water path surfaces(s) is/are made by connecting together a series of prefabricated modules. 10 A device as in any previous Claim where the power generated is used for telemetry equipment and/or data transmission, optionally by using batteries and electrical conditioning apparatus. I I A device comprising a plurality of devices as in any previous Claim used together in combination. 12 A device as in any previous Claim installed in fresh water or saline water (including without limitation estuarine and/or tidal water). 13 A device as in any previous Claim incorporating a fish counter and/or a water flow meter. |
The present invention relates to wildlife ladders for aquatic wildlife.
Civil engineering structures which block watercourses have a number of applications such as hydroelectric barrages and flood alleviation. However they also block the flow of aquatic animals and fish and measures have to be taken to rectify this in order to maintain the continuity and health of aquatic and riparian ecosystems.
In particular, if migratory fish cannot reach their headwater spawning grounds, the population may become rapidly depleted.
A number of techniques exist to address this, but generally they involve extra cost and/or additional riparian land for construction.
Many governments have set challenging targets for future production of renewable energy, including hydro-electric generation. However certain proposals for low-head hydro schemes may become unattractive when the land take, ecosystem disruption, and costs of a traditional wildlife bypass are incorporated.
The most common approach to the by-pass route is based on an inclined plane and has multiple variants, including pool-and-weir, pool-and-weir with vertical slot, and baffle- fishway. Typically this is installed parallel to the barrage, and has a separate continuous flow of water, so that aquatic wildlife is able to traverse it in both directions. Because many types of fish can only climb flows derived from shallow gradients, fish ladders are long, and involve considerable land and large quantities of concrete. Some designs require fish to jump repeatedly which some species are unable to do. Fish ladders generally require fish to climb or jump an ascent, or ascending surface. When flow is low, existing schemes at hydro-electric plants may require the total suspension of power generation in order to provide flow for the bypass. Historically the main objective was often to allow large (economically important) fish to pass at particular times of year, but today it is normal to consider the whole ecosystem with the objective that all significant biota can pass upstream and/or downstream as appropriate at all times of year.
It is the objective of embodiments of the present invention to address these problems.
Hydroelectric turbines use the force of flowing water to create rotational motion and hence produce useful power or drive electrical generators. Inside the turbines are blades which can be fatal to fish which enter the turbine. Over recent years manufacturers of turbines have created "fish-friendly" designs. These typically involve adapting existing turbine designs by removing a fraction of the blades, and/or reducing the size of the blades so that there is a central passage through the turbine (eg WO.2005.080789 Williams and US.2005.005592 Fielder). Both documents disclose a horizontal turbine not providing an ascent. In the paper "Development and evaluation of a new helical fish friendly turbine" (ASCE Journal of Hydraulic Engineering, Volume 131 , Number 10, October 2005) Hecker and Cook detail causes and rates of fish mortality in hydro-turbines.
Importantly, even so-called "fish-friendly" turbines still cause death and injury to fish (especially larger fish) and can only ever provide a downstream pathway.
Some relevant fish ladder designs are noted below:
DE19510347 (Mueller) describes a static helical fish ladder, with two principal embodiments, the first being an open V-shaped duct wound around a vertical cylindrical former, and the second having a closed pipe instead of the duct.
GB1451944 (Aeroceanics) similarly describes an open duct in prefabricated straight and semicircular stretches which can be joined together to make a range of shapes, including a helix. US3038314 (Hultman 1962) describes a helical design, but Hultman's design is static and offers no generation of power.
JP9059965 proposes a circulating hydraulic vertical elevator, using descending water to lift a continuous series of containers into which a fish might swim and then be transported to the upper water level. Though providing an ascent, fish are not required to climb.
Existing helical fish ladders are all static, and none provide a source of power. Although some hydroelectric turbines claim to be "fish-friendly" they do not provide a stress-free fishway both downstream and upstream, nor do they provide an ascent.
There is a need for technologies generating hydro-power while allowing permanent easy bidirectional passage of wildlife and avoiding harming the ecosystems and morphology of rivers.
The present invention is an active "wildlife ladder" desirably providing a low-stress bidirectional route for aquatic animals and fish, to minimise land use, and also able to generate useful power.
By-pass routes for aquatic wildlife are often designed as a secondary part of a civil engineering project. The present invention instead makes welfare of wildlife a primary objective.
In a first of its aspects, the invention may provide an unpowered device providing an aquatic wildlife ladder giving passage (preferably easy passage) upstream and downstream to circumvent a hydraulic obstruction, and providing a means to generate useful power from the water flowing through the device. The device may provide a guide for a descending flow of water. Aquatic wildlife may ascend the device by climbing against the descending flow, or may descend the device by going with the descending flow. The device may be adapted to provide a guide for a continuous flow of water over a substantially continuous inclined surface, The device may include an upright or vertically mountable or mounted housing containing a substantially helical surface providing the water path (e.g. the guide for descending water) and rotatable about an upright or a vertical axis
The device may contain a plurality of coaxial water path/guide surfaces which may be parallel channels formed in the surface of the guide.
The device may be coupled directly or indirectly to an electrical generator
The housing of the device may be cylindrical or substantially cylindrical
The housing and water path/guide surface(s) may substantially take the form of sections from a cone
The water path/guide surface(s) may incorporate(s) texture and/or structure including without limitation channels and/or pools
The water path/guide surface(s) may be manufactured in metal and/or glass-reinforced plastic and/or a composite material
The water path/guide surfaces(s) may be made by connecting together a series of prefabricated modules
The power generated by the device may be used for telemetry equipment and/or data transmission, optionally by using batteries and electrical conditioning apparatus
The invention may provide an unpowered device comprising a plurality of devices described above used together in combination
The device may be installed in fresh water or saline water (including without limitation estuarine and/or tidal water), and the invention may provide a device so installed in a further of its aspects.
The device may incorporate a fish counter and/or a water flow meter BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 shows a schematic vertical cross-section through an embodiment of the present invention.
Figure 2 shows a more detailed cross-section through one embodiment with surface water channels incorporated.
The drawings are intended to make clear the structure and operation of the present invention but are not to scale and do not show the precise geometry of embodiments (which in any case vary).
The present invention will be described by reference to the Drawings. It consists of a device providing easy permanent bidirectional flow for aquatic wildlife, by regulating water flow, and additionally using the water flow to generate useful power. The device itself needs no power supply, runs unattended, has a small footprint, and can be built into a barrage.
The present invention is particularly applicable to low-head installations where existing technologies cannot effectively balance investment, hydro-generation, land requirements and ecosystem protection. A particular advantage in such installations is that the device takes the whole flow through a single channel making it easy for ascending wildlife to sense the correct route. This also facilitates acquisition of accurate data from a fish counter and/or water flow meter.
The present invention consists of a substantially helical inclined surface (101 ) wrapped around a central vertical shaft (103) either solid or hollow. Water (105) flows over the surface (101 ) and provides the pathway for aquatic wildlife. The hydraulic parts of the device are contained within a housing (107), preferably cylindrical to provide uniformity of manufacture, but other shapes including conic sections may be used to introduce variation in water flow. Preferably the housing has protrusions (1 15) into the upper water body so that on all sides of the open top of the housing (107) there is a pool for easy entry and exit of wildlife.
The upper edge (1 17, a radius) of the surface (101 ) is preferably rounded or made of low impact material so that it causes no injury in case of collision with an animal or fish. Optionally it may have a horizontal extension and/or low gradient spillways (not shown in the Drawings) to facilitate entrance and exit.
When a mass m is on a plane inclined at angle θ to the horizontal, it experience a vertical downwards force mg (where g is the gravitational acceleration) and a reaction force perpendicular to the plane of magnitude m-g-cos(θ). The vector sum of these is an accelerating force m-g-sin(θ) parallel to the plane. The plane experiences an equal and opposite reaction force. If the plane is supported vertically but free to move horizontally, it experiences a horizontal accelerating force m-g-cos(θ) -sin(θ).
In the present invention the inclined plane is a surface (101 ) substantially in the form of a helix, and the mass is the water (105) flowing over the surface (101 ), and the force provides a rotational torque about the vertical shaft (103). This accelerates the device from rest until it reaches an equilibrium rate of rotation where the accelerating force is equal and opposite to dynamic friction. Note that the torque is in the opposite direction to the flowing water so that the surface (101 ) may be considered to rotate "backwards".
Practical gradients for most migratory fish are in the range 1 in 20 (5%) to 1 in 50 (2%).
The surface (101 ) preferably has a textured upper surface maintaining a desired flow rate close to the surface, even when large volumes of water are passing through. However the interaction of the water with the texture generates a force (and hence torque) opposing the torque above - and reducing efficiency. So the amount of texturing is a design compromise. At its lower end the surface (101 ) extends below the surface of water (121 ) at the foot of the barrage, allowing easy entry and exit. There are substantial openings (127) in the housing (107) to allow entry and exit of animals and fish. Optionally the lower end of the surface (101 ) may incorporate an "apron" with shallow or no gradient (not shown in the Drawings) to facilitate entrance and exit. The rotation of the surface (101 ) acts to set up a circulating current which also assists entrance and exit by distributing the flow shear experienced by fish more gradually over a larger volume of water.
The lower end of the central solid or hollow shaft (103) is located in a simple hydrodynamic or other bearing (1 1 1 ) lubricated by water. The upper end of the shaft (103) extends clear of the upper water surface (123) producing useful power and/or driving (preferably via a gearbox or belt drive, optionally by an additional coupling) an electrical generator. These components (125) preferably include a bearing and are preferably located well above the maximum expected water level. As is well known to those skilled in the art, the electrical output may serve (directly and/or via inverters and/or transformers and/or active electronics) to charge one or more batteries and/or power equipment, and/or be exported to an electricity grid for wider distribution.
An alternative embodiment incorporates fixed magnets around the edges of the rotating surface (101 ) and stator wiring within the housing (107). This comprises an intrinsic electrical generator. This is more complex to construct but avoids the need for a separate generator and couplings.
In particular, if the present invention is installed at a remote weir, it may conveniently provide power for telemetry equipment and wireless transmission of data.
Preferably the helical surface (101 ) is manufactured in sections (segments) which bolt together (analogously to a traditional spiral staircase). The number of such sections is chosen as appropriate to the difference in head at each installation. Preferably the sections locate onto the central solid or hollow shaft (103).
Preferably the helical surface (101 ) is made of stainless steel, and/or more preferably of glass-reinforced plastic and/or other composite material. Figure 2 shows how the surface (101 ) preferably incorporates one or more channels (201 ) formed in its surface to provide a continuous water body for passage of wildlife. The channels (201 ) are formed so that each one starts to fill only when the previous is full and starts to overflow. Figure 2 shows three channels (201 ) but this is for ease of illustration and any reasonable number of channels (201 ) may be used. Each channel may be continuous or in the form of a series of pools. The channels have different radii, and hence different gradients and water velocities, giving scope to design for specific species.
To reduce flow rate further, baffle plates may used in one or more of the channels, preferably shaped and positioned so that they have greater effect when water levels are higher and consequently flows and/or velocities are larger.
Different embodiments of the present invention for use in different locations are of different sizes and different relative dimensions, as appropriate for flow and head conditions.
Figure 1 shows a cylindrical form (for ease of illustration) but embodiments in other forms have advantages in certain deployments. A conical form with a larger radius at the base gives a lower gradient and longer path at the base, so the water speed will be reduced (relative to a shorter steeper path). It is also advantageous in some embodiments to reduce radius at the inlet and/or outlet to reduce velocity shear and so ease the passage of wildlife.
In embodiments of the present invention where the radius of the device is large, it is preferable to have a plurality of coaxial helical surfaces (101 ) arranged like a multi- thread screw. This is to avoid a large vertical drop in or jump out at the top of the device, and to allow a greater flow of water. If there are N helices, the device has radius r and the surfaces (101 ) are inclined at angle θ to the horizontal, the biggest drop is the distance between surfaces and is equal to 2-π-r-sin(θ) / N Where a large vertical interval has to be traversed, it is preferable to use a plurality of devices, preferably with pools between them to allow wildlife to make the journey in several stages.
Although wildlife ladders are traditionally used in freshwater systems, embodiments of the present invention are also well suited to operation in an estuarine and/or tidal barrage, providing bidirectional passage.
While the present invention has been described in terms of several embodiments, those skilled in the art will recognize that the present invention is not limited to the embodiments described, but can be practised with modification and alteration within the spirit and scope of the appended claims. The Description is thus to be regarded as illustrative instead of limiting.
The present invention is an example of how hydropower and wildlife passages can be integrated in a single flow system. The same approach is applicable to other combinations of power and passage. For example, small cylindrical rotors that rotate around a horizontal and cross-flow axis maybe fitted to each step in a crump-weir-type fish pass; this will allow power to be drawn from these stepped flows at the same time as fish are allowed passage in both directions.