Wave attenuation structure constructed of decommissioned wind turbine blades and method for erecting a wave attenuating structure

Abstract

The invention concerns a wave attenuation structure constructed of decommissioned wind turbine blade elements. 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 blade elements for this purpose allows for a second life for the large number of otherwise difficult to recycle fiberglass composite blades. The invention further concerns a method for erecting such wave attenuation structure.

Description

[0001] Wave Attenuation Structure Constructed of Decommissioned Wind Turbine Blades and Method for Erecting a Wave Attenuating Structure

[0002] 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.

[0003] 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.

[0004] The invention allows a wave attenuation structure to be constructed of decommissioned wind turbine blades, in particular of blade elements. A blade element consists of a complete wind turbine blade or a part of a wind turbine blade. In particular embodiment of the invention, the length of a blade element may be from 5 % to 100 % of the length of the complete blades, in particular from 15 to 50 %; that percentage number may strongly depend on the total length of the blade which may vary from about 10 to more than 150 m. In another embodiment of the invention, the length of a blade element may be from 8 to 30 m, in particular 8 to 12 m. In general, the length of the blade elements used in the invention depends on

[0005] - the size of the decommissioned turbine blades,

[0006] - the depth of water and foundation depths reguired for the blade attenuation structure and on

[0007] - logistical considerations like the maximum length of transportation vessels e.g.,

[0008] ISO containers, trucks or boats.

[0009] A wave attenuation structure according to the invention may likewise be constructed of a mixture of parts of decommissioned blades and complete decommissioned blades. The wave attenuation structure is 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 blade elements for this purpose allows for a second life for the large number of otherwise not re-usable composite blades, which may contain fiberglass and / or other material difficult to recycle.

[0010] According to the invention, a wave attenuation structure is a system of components that reduces the wave energy transmitted across the structure.

[0011] 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 blade elements are not connected to each other or otherwise dependent on each other for stability, any form of continuous line may be followed.

[0012] By installing an array of decommissioned wind turbine blade segments, wave heights can be reduced on the shoreside of the structure.

[0013] The blade elements are installed primarily vertically, by which is meant that the longest dimension is installed primarily perpendicular to the water surface. The rotation of the blade elements 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 element 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.

[0014] In more detail, the direction of a blade being part of the wave attenuation structure refers to the angle of erection of such blade element and is related to an axis of the respective blade element. 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 element. The erection angle is defined to be 0°, if the blade element 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.

[0015] A wave attenuation structure according to the invention comprises normally more than 100 or more than 1000 or even several thousands of blade elements. There is no upper limit except the geography and the availability of decommissioned blades.

[0016] By installing the blade elements in a widely spaced line, significant reductions in wave heights can be achieved without creating a barrier to fauna, water exchange and natural processes.

[0017] Gap widths of 40% of blade element 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.

[0018] If wider gaps are required, then, in a group of n neighbouring blade elements, gap widths between each pair of blade elements can be d1 , which is smaller than the gap width between the (n-1)th and the nth blade element 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 %.

[0019] 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 10thgap being 2 m wide allowing for significantly large fauna to reach the beach. If greater reductions of wave energy are required, one or more additional rows of blade elements 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 blade elements 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 blade elements 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.

[0020] In order to improve the attenuation effect, at least some blade elements may have an erection angle inclined versus the vertical by at least 15°. Preferably, most or all of the blade elements 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.

[0021] By installing the blade elements 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 blade elements 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 element 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 blade elements of a row can be angled away from the incoming waves, others being angled towards the incoming waves.

[0022] The invention further concerns a method of erecting a wave attenuating structure according to claim 9. The great length of wind turbine blade elements 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.

[0023] 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.

[0024] For similar reasons, sufficient drainage holes must be installed to prevent compressive forces due to hydrostatic pressure differences caused by tidal water level differences.

[0025] Depending on the specific conditions of the installation, the blade elements 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.

[0026] If the blade elements comprise the tip of the blade, by installing blade elements 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 blade elements is the sections interacting with the most energetic upper sections of the waves.

[0027] The invention and further details of the invention are explained in the following by schematic drawings showing:

[0028] Figure 1 a section of a first embodiment of the structure according to the invention, such section comprising five blade elements in a single line and

[0029] Figure 2 a part of a second embodiment of the invention with two lines of blade elements in parallel.

[0030] In the simplest way of realizing the invention, just a single line of blade elements is erected along the coastal line as shown in Figure 1. The blade elements of the two particular embodiments consist of complete wind turbine blades. The technology disclosed in the embodiments can, however, easily applied to the usage of parts of wind turbine blades. In special cases, five blade elements 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.

[0031] All blade elements could have the same distance d1. In Figure 1 , however, the fifth blade element has a greater distance d2 > d1 from the fourth blade element as previously described. A sixth blade element (if present) is not shown in the drawing, but would have the standard distance d1 from the fifth blade element.

[0032] The width w of the blade elements is equal to the maximum dimension in parallel to the continuous line. The gaps d1 and d2 are the minimum distance between two neighbouring blade elements.

[0033] The lower horizontal line in Figure 1 represents the "continuous line", the blade elements are arranged at. Although this line being labelled "sea floor" in Figure 1 , it could also be the ground level, if the blade elements are arranged onshore. The "mean high tide level" is identical to the previously introduced pre-defined tide level.

[0034] The blade elements 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 blade elements are usually oriented downwards.

[0035] 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 blade elements 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 blade elements are angled towards the incoming waves.

Claims

Patent Claims1. Wave attenuation structure constructed of decommissioned wind turbine blade elements, a blade element comprising a complete wind turbine blade or a part of a wind turbine blade, the blade elements being arranged primarily vertically in a linear manner with a distance between each pair of neighbouring blade elements along a continuous line.

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

3. Wave attenuation structure according to claim 1 or 2 the distance d between most pairs of neighbouring blade elements 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 blade elements, n >= 3, n-1 distances of neighbouring blade elements 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 blade elements are inclined versus the vertical by at least 15°.

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

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

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

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

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

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