Wave attenuation structure constructed of decommissioned wind turbine blades

Abstract

The invention describes a wave attenuation structure constructed of decommissioned wind turbine blades. This is a structure intended for installation along soft shorelines threatened by wave erosion. A formation of piles can reduce wave energies, and is a simple structure to install securely in soft deep sediments. Due to the high degree of permeability, a formation of piles can also ensure that erosion can be reduced whilst minimizing the impact on nature. Utilizing decommissioned wind turbine blades for this purpose allows for a second life for the large number of otherwise difficult to recycle fiberglass composite blades.

Description

[0001] The invention concerns on the one side the technical area of coastal protection becoming increasingly important during the current progression of the climate crises. The idea of the invention concerns renewal energy production as one of the key element fighting the climate crisis. Wind turbines are classical means for producing renewable energy, but they have themselves a limited lifetime. After that lifetime, a huge amount of waste accumulates, as the wind turbine blades normally cannot by recycled.

[0002] The invention combines now usage of decommissioned wind turbine blades with effective and cost-efficient coastal protection, so that two problems in climate change mitigation are addressed.

[0003] The invention allows a wave attenuation structure to be constructed of decommissioned wind turbine blades. This is a structure intended for installation along soft shorelines threatened by wave erosion. A formation of piles can reduce wave energies, and is a simple structure to install securely in soft deep sediments. Due to the high degree of permeability, a formation of piles can also ensure that erosion can be reduced whilst minimizing the impact on nature. Utilizing decommissioned wind turbine blades for this purpose allows for a second life for the large number of otherwise not reusable composite blades, which may contain fiberglass and / or other material difficult to recycle.

[0004] According to the invention, a wave attenuation structure is a system of components that reduces the wave energy transmitted across the structure.

[0005] Such a structure is erected along the section of coastline to be protected according to local conditions. The structure is linear and runs along a continuous line. The continuous line does not necessarily have to be parallel to the coastline or perpendicular to incoming waves. The structure does not have to be straight or completely continuous on longer distances, but can be erected in distinct portions, and can be adapted to local hydrological, morphodynamic and geographic concerns. As the blades are not connected to each other or otherwise dependent on each other for stability, any form of continuous line may be followed.

[0006] By installing an array of decommissioned wind turbine blade segments, wave heights can be reduced on the shoreside of the structure.

[0007] The blades are installed primarily vertically, by which is meant that the longest dimension is installed primarily perpendicular to the water surface. The rotation of the blades on this axis is chosen such as to maximise the wave attenuation function. The exact axial orientation depends on the exact shape of the available blade segments. As a rough approximation this is chosen such that the blade presents the largest possible area towards the waves. "Primarily vertical" comprises the vertical direction and all directions deviating less than 75 °, in particular less than 55° from the vertical.

[0008] In more detail, the direction of a blade being part of the wave attenuation structure refers to the angle of erection of such blade and is related to an axis of the respective blade. The axis is defined as the or one of the straight lines passing along the maximum distance through the interior of the wind turbine blade. The erection angle is defined to be 0°, if the blade is exactly vertically erected. In the invention, angles inclined to the vertical are preferred, i.e. angles of erection larger than zero in magnitude, in particular larger than 20° and preferably smaller than 75 °. A particularly preferred range of the angle of erection is 30 ° to 50 °. Another preferred embodiment is a vertical installation.

[0009] A wave attenuation structure according to the invention comprises normally more than 100 or more than 1000 or even several thousands of blades. There is no upper limit except the geography and the availability of decommissioned blades.

[0010] By installing the blades in a widely spaced line, significant reductions in wave heights can be achieved without creating a barrier to fauna, water exchange and natural processes.

[0011] Gap widths of 40% of segment width enable significant reductions in wave heights whilst still enabling most marine fauna to access the inshore. This is gap measured at a pre-defined tide level according to local conditions. The pre-defined tide level is preferably chosen as the height, where most of the wave energy is present and where the wave attenuation functionality should be maximised.

[0012] If wider gaps are required, then, in a group of n neighbouring blades, gap widths between each pair of blades can be d1, which is smaller than the gap width between the n-1)th and the nth blade being d2 > d1, ensuring that averaged over the structure the gap ratio required for the desired reductions in wave energy is maintained. The choice of d1 and d2 is limited by the distance between the structure and the shoreline to be protected. Enough space is required for the wave to defuse; this minimum distance is dependent on the gap width, the required reduction in wave energies and the wavelength. Starting from a fixed average gap width d, gaps 1 to n-1 are reduced by a factor of x %: d1 = d 1 − x % , and gap n will be enlarged to d2 = d1 + n − 1 * x % .

[0013] In a practical example with n = 10, an average gap* of 1.0 m and x = 10 % are chosen. This allows for regular gaps of 0.9 m with every 10 th< gap being 2 m wide allowing for significantly large fauna to reach the beach.

[0014] If greater reductions of wave energy are required, one or more additional rows of blades can be installed to form a combined wave attenuation structure according to claim 5. The two continuous lines may have a distance dh of at least the gap width between individual blades in the lines. In practical embodiments dh is larger than 1 m, preferably than 3 m having basically no upper limit. Normally there are no values above 650 to 1,000 m. Practical values lie between 1 and 100 m. The two structures may or may not be staggered. Due to wave diffraction, if enough space is between the lines, depending on the wave lengths and the gaps between the individual blades in the lines, lines do not have to be staggered to reduce wave heights, enabling straight channels to be created for beach access, whilst still reducing wave energies.

[0015] In order to improve the attenuation effect, at least some blades may have an erection angle inclined versus the vertical by at least 15°. Preferably, most or all of the blades are inclined accordingly. The inclination may be in any direction, but preferably perpendicular to the coast and / or to the continuous line of the structure. This may be optimized based on the exact wave conditions in the construction area.

[0016] By installing the blades angled towards the incoming waves, the energy dissipation of the structure can be increased significantly. If waves overtopping the structure is not a concern (i.e. if the structure is high enough), the blades can be angled away from the incoming waves with a similar effect, and enabling the installation from shallower waters, and reducing the danger that the turbine blade piles pose to shipping. The exact mechanism for this improvement of the wave attenuation capabilities of a pile breakwater is not completely understood. If multiple lines of wave breakers are installed then by angling the seaward wave breakers towards the coast and the shoreward wave breakers towards the sea, the danger to shipping is reduced. In particular embodiments, some of the blades of a row can be angled away from the incoming waves, others being angled angled towards the incoming waves.

[0017] The invention further concerns a method of erecting a wave attenuating structure according to claim 9.

[0018] The great length of wind turbine blades can be exploited to enable sufficiently deep foundations in soft coastal sediments, as well as to ensure that the structures is tall enough to deal with great tidal ranges. However since turbine blades can be over 100 m in length it is possible to utilize blade segments cut to the lengths required by the conditions of the site where the wave breakers are required.

[0019] Foundation depths of more than 10 m can be necessary to reach sufficiently consolidated sediments to ensure the stability of the structure. Due to the hollow nature of the blades, they should to be filled with sand or gravel during installation to ensure that compressive forces due to ground pressure can be equalized.

[0020] For similar reasons, sufficient drainage holes must be installed to prevent compressive forces due to hydrostatic pressure differences caused by tidal water level differences.

[0021] Depending on the specific conditions of the installation, the blades can be installed by vibrating or ramming into soft coastal sediments, if necessary this process can be improved by running hoses through the hollow structure of the and using water jets to loosen the ground directly in front of the tip during installation, e.g. utilizing a precut hole.

[0022] By installing blades tip first, the pointed shape of wind turbine blades can be utilized to enable easier installation. This has the further advantage of ensuring that the wider section of the blades is the sections interacting with the most energetic upper sections of the waves.

[0023] The invention and further details of the invention are explained in the following by schematic drawings showing: Figure 1a section of a first embodiment of the structure according to the invention, such section comprising five blades in a single line and Figure 2a part of a second embodiment of the invention with two lines of blades in parallel.

[0024] In the simplest way of realizing the invention, just a single line of blades is erected along the coastal line as shown in Figure 1. In special cases, five blades could form already a structure according to the invention as expressly shown in Figure 1, but normally the arrangement shown in the drawing is repeated to both sides several if not many times.

[0025] All blades could have the same distance d1. In Figure 1, however, the fifth blade has a greater distance d2 > d1 from the fourth blade as previously described. A sixth blade (if present) is not shown in the drawing, but would have the standard distance d1 from the fifth blade.

[0026] The width w of the blades is equal to the maximum dimension in parallel to the continuous line. The gaps d1 and d2 are the minimum distance between two neighbouring blades.

[0027] The lower horizontal line in Figure 1 represents the "continuous line", the blades are arranged at. Although this line being labelled "sea floor" in Figure 1, it could also be the ground level, if the blades are arranged onshore. The "mean high tide level" is identical to the previously introduced pre-defined tide level.

[0028] The blades are installed into the costal sediment below the continuous line, so that they are anchored in the ground. The tips of the thinner sections of the blades are usually oriented downwards.

[0029] Figure 2 shows a combined wave attenuation structure comprising two partial wave attenuation structures arranged on different continuous lines running in a distance. A section of six neighboring blades per row is depicted in the drawing. Normally the structure is continued in the same way to both sides. Again the pre-defined tide level is shown ("water level") as well as the level on which the continuous lines run ("ground level / sea floor"). In this embodiment, the blades are angled towards the incoming waves.

Claims

1. Wave attenuation structure constructed of decommissioned wind turbine blades arranged primarily vertically in a linear manner with a distance between each pair of neighbouring blades along a continuous line.

2. Wave attenuation structure according to claim 1, wherein distance d between at least one pair of neighbouring blades leaves a gap at a pre-defined tide level of 0.1 to 1.9 of the width of the turbine blade at such pre-defined tide level.

3. Wave attenuation structure according to claim 1 or 2 the distance d between most pairs of neighbouring blades along the continuous line is 0.1 to 3.2 m.

4. Wave attenuation structure according to any of the previous claims, wherein in a group of n neighboring blades, n >= 3, n-1 distances of neighbouring blades are equal to d1 and the nth distance is equal to d2 > d1.

5. Combined wave attenuation structure comprising two or more partial wave attenuation structures according to any of the previous claims, wherein the two continuous lines run in a distance.

6. Wave attenuation structure according to any of the previous claims, wherein at least some blades are inclined versus the vertical by at least 15°.

7. Wave attenuation structure according to claim 6, wherein at least some blades are inclined towards a pre-defined incoming wave direction.

8. Wave attenuation structure according to claim 6 or 7, wherein at least some blades are inclined away from a pre-defined incoming wave direction.

9. Method for erecting a wave attenuating structure comprising arranging multiple decommissioned wind turbine blades primarily vertically or close to vertically in a linear manner along a continuous line with a distance between each pair of neighbouring blades.

10. Method according to claim 9, wherein the blades are arranged in the underground by ramming or vibrating.

11. Method according to claim 9 or 10, wherein, during arranging the blades in the underground, the tips of the blades are oriented to the bottom.

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