A FLOATING SOLAR PHOTOVOLTAIC SYSTEM

Abstract

A floating photovoltaic system (1) comprising a flotation unit (100) and a mooring system (30), wherein the flotation unit (100) comprises at least one sail (2) having at least one vertical or near vertical photovoltaic panel (20) mounted on a mast (3) and supported on a base (5), wherein the base (5) further comprises at least one buoyancy element (10); and wherein the mooring system (30) comprises a single point mooring buoy (32) connected to at least one buoyancy element (10) or the base (5) via mooring lines (33), and at least one mooring line (34) from the single point mooring buoy (32) tethered to at least one anchor point (36).

Claims

1. A floating solar panel system (1) comprising a flotation unit (100) and a mooring system (30), wherein the flotation unit (100) comprises at least one sail (2) having at least one vertical or near vertical photovoltaic panel (20) mounted on a mast (3) and supported on a base (5), wherein the base (5) further comprises at least one buoyancy element (10); and wherein the mooring system (30) comprises a single point mooring buoy (32) connected to the at least one buoyancy element (10) or to the base (5), and at least one mooring line (34) from the single point mooring buoy (32) tethered to at least one anchor point (36).

2. The floating solar panel system (1) according to claim 1, wherein the mooring system (30) comprises at least two or at least three mooring lines (34) tethered to the at least one anchor point (36).

3. The floating solar panel system (1) according to claim 1 or claim 2, wherein there is one anchor point (36) for each mooring line (34).

4. The floating solar panel system (1) according to any one of the preceding claims, wherein the mooring system allows the flotation unit (100) to rotate about the single point mooring buoy (32).

5. The floating solar panel system (1) according to anyone of the preceding claims, wherein the at least one vertical or near vertical photovoltaic panel (20) is aligned to be in-line with a downwind direction of the single point mooring buoy (32).

6. The floating solar panel system (1) according to any one of the preceding claims, wherein two or more flotation units can be connected together via a horizontal element (8).

7. The floating solar panel system (1) according to claim 6, wherein the horizontal element (8) connects to the two or more flotation units (100) via a flexible joint (9) at either end of the horizontal element (8).

8. The floating solar panel system (1) according to claim 6 or claim 7, wherein the horizontal element (8) or the base (5) is composed from a material selected from galvanised steel, stainless steel, polypropylene, polyethylene, polyethylene terephthalate copolymer, amorphous polyethylene terephthalate, polyvinyl chloride, steel, steel coated with a corrosion resistant coating, galvanized steel, aluminium, titanium, fibre reinforced polymer, concrete, reinforced concrete with or without prestressed elements, syntactic foam, or composite materials.

9. The floating solar panel system (1) according to any one of claims 6 to 8, wherein the horizontal element (8) has an open frame structure to allow light to pass between the sail (2) and a water surface.

10. The floating solar panel system (1) according to any one of the preceding claims, wherein the at least one buoyancy element (10) is connected to the base (5).

11. The floating solar panel system (1) according to claim 10, wherein the at least one buoyancy element (10) is positioned to align with a down wave direction of the single point mooring buoy (32).

12. The floating solar panel system (1) according to claim 10 or claim 11, wherein the at least one buoyancy element (10) is a type selected from a horizontal shaped element, a circular shaped element, a SPAR-shaped element, a box shaped element, or a flat raft-type element, a single or multiple pipe element, a semi-submersible element, and other elongated buoyancy shaped elements.

13. The floating solar panel system (1) according to anyone of the preceding claims, wherein the photovoltaic panels (20) are monofacial or bifacial, or a combination thereof.

14. An array (200) comprising a plurality of the flotation units (100) of claim 1 joined together by a horizontal element(s) (8) via a flexible joint (9) at either end of the horizontal element (8).

15. The array (200) of claim 14, further comprising a reflective or a non-reflective material stretched over the horizontal element (8).

16. A method of generating solar energy, the method comprising placing the floating solar panel system (1) of claim 1 on a body of water, securing the system (1) to the single point mooring buoy (32), and securing the single point mooring buoy (32) with the at least one mooring line (34) that is also tethered to the at least one anchor point (36).

17. The method of claim 16, wherein the solar panel system (1) is further connected a battery, a cable connected to the national grid, a cable connected to a standalone micro-grid, a cable connected to a subsea oil and/or gas asset, a cable connected to a subsea datacentre, a cable connected to an offshore charging station, a cable connected to an offshore platform, a cable connected to a desalination plant, a cable connected to a hydrogen electrolyser, a cable connected to shoreside buildings in conjunction with battery banks, grid mains electricity, or both; or a cable connected to an offshore wind turbine or a cable connected to an offshore transformer station, or both.

18. The method of claim 16 or claim 17, wherein the material of construction of the system (1) is selected from a durable yet rigid material, for example stainless steel, polypropylene, polyethylene, polyethylene terephthalate copolymer, amorphous polyethylene terephthalate, polyvinyl chloride, steel, steel coated with a corrosion resistant coating, aluminium, titanium, fibre reinforced polymer, concrete, reinforced concrete with or without prestressed elements, syntactic foam, and the like.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The invention will be more clearly understood from the following description of an embodiment thereof, given by way of example only, with reference to the accompanying drawings, in which:

[0037] FIG. 1 illustrates an end view of one aspect of the floating photovoltaic system of the claimed invention.

[0038] FIG. 2 illustrates a side view of the floating photovoltaic system as shown in FIG. 1.

[0039] FIG. 3 illustrates a perspective view of the floating photovoltaic system as shown in FIGS. 1 and 2.

[0040] FIG. 4 is a plan view of the floating photovoltaic system as shown in FIGS. 1 to 3 with the passive mooring system illustrated. The system weathervanes about a mooring buoy. The circles show the approximate watch circle of the system and mooring anchor footprint.

DETAILED DESCRIPTION OF THE DRAWINGS

Materials and Methods

[0041] Solar panels can be PV or thermal solar panels. The floating structure is made of materials suitable for the marine (fresh and/or salt water) environment which includes metallic materials (either corrosion resistant alloys or non-corrosion resistant metals with an appropriate coating system and/or cathodic protection system), polymer materials, HDPE, fibre reinforced polymer materials, and the like.

[0042] A test using 1:10 scale model of a small array of 4 sails described herein in a wave-generating and wind-generating water tank with horizontal lines affixed thereto that simulate the mooring lines going to a mooring buoy. Tests were performed under different wind and wave conditions.

Results

[0043] The tests using the scale model (circa 1:10 scale) under different wind and wave conditions demonstrated the weathervane motion of the system when subjected to wind and waves. The tests also demonstrated that the use of flexible joints attaching the flotation units together in an array adapt to the wave profile, further reducing structural loads from the wave action by adapting to the wave profile rather than remaining rigid and resisting the vertical wave forces structurally. The individual flotation units within the array are free to rotate (pitch and roll) and heave (up-down) but are fixed relative to each other in surge, sway, and yaw. This means that the sails of the flotation units cannot clash with each other as they are restrained in surge, sway, and yaw, but also that the structural force in the array is minimized if the individual flotation units are free to move in pitch, roll, and heave (this means they adapt to or follow the wave profile).

[0044] Referring now to the figures, where FIG. 1 illustrates a general embodiment of a floating photovoltaic (PV) system of the present invention. Specifically, FIG. 1 illustrates an end view of a system of the present invention and is generally referred to by reference numeral 1. The system 1 of the illustrated embodiment comprises at least one flotation unit 100 having at least one sail 2 comprising at least one vertical or near-vertical mast 3, each mast 3 configured to accommodate at least one photovoltaic panel 20, and a base 5. The base 5 is configured to accommodate at least one photovoltaic panel 20. The base 5 further comprises at least one buoyancy element 10 positioned beneath the base 5. The buoyancy element 10 shown in the Figures is a pair of twin horizontal pipe elements. Other buoyancy configurations that could be used include buoyancy element(s) of various shapes or SPAR-type buoyancy elements, a flat raft type structure, a single or multiple pipe structure, a semi-submersible type structure, of which all could also be used. The photovoltaic panels 20 can be monofacial and mounted back-to-back, or the photovoltaic panels 20 can be bifacial.

[0045] As can be seen from FIGS. 2 and 3, the floating photovoltaic system 1 comprises a plurality of flotation units 100 spaced apart from each other, forming an array of flotation units 100. The flotation units 100 are linked together by horizontal elements 8 which connect the individual bases 5 together. These linking horizontal elements 8 fall within approximately the same horizontal plane as each other and are parallel to the still water level. The linking horizontal elements 8 are connected to the bases 5 by flexible joints 9 at either end of each horizontal element 8. The horizontal elements 8 and the space between the sails 2 can be made from reflective or non-reflective material.

[0046] The array of flotation units 100 are tethered to a mooring system 30 (see FIG. 4). The mooring system 30 comprises a single point mooring buoy 32 connected to the array of flotation units 100 at a point 33, and coupled to one or more mooring lines 34 that are tethered to at least one anchor point 36. The at least one anchor point 36 can be on land or on the seabed.

[0047] The single point mooring buoy 32 is positioned at a single point relative to the array of flotation units 100. This configuration means that the array of flotation units 100 can rotate around the single point mooring buoy 32, that is, it enables the weathervane motion of the array of flotation units 100. Mooring configurations with multiple surface buoys at different points around the array of flotation units 100 would restrain the rotational motion of the array of the flotation units 100, preventing the weathervane motion. The motion of the array of flotation units 100 is caused by the environmental loads (e.g., wind and wave loads), and the geometric configuration of the mooring system 30. This allows free rotation of the array of flotation units 100 about a single point (the single point mooring buoy 32), which is offset from the centre of the array of flotation units 100, and results in the array of flotation units 100 automatically or passively rotating downwind or down wave of the single point mooring buoy 32. The alignment of the vertical or near-vertical sails 2 on the array structure is set to be in-line with the downwind direction of the single point mooring buoy 32, ensuring that the sails 2 are edge on to the wind, which reduces wind loads. Buoyancy elements 10 at the base 5 of the system 1 can also be positioned so that they align with the down wave direction of the single point mooring buoy 32. This reduces wave loads by minimizing the area of the buoyancy elements 10 exposed to the oncoming waves by ensuring the smaller end area of the buoyancy elements 10 point towards the oncoming waves, for example, by ensuring the buoyancy element 10 is bow on to the waves for shaped buoyancy elements or end on for horizontal pipe-shaped buoyancy elements.

Discussion

[0048] The advantages of the floating vertical or near-vertical solar panel system 1 are that having high wind loads from one direction (perpendicular to panels), with very low wind loads from the opposite direction (end on to panels), combining this with a weathervane (passive) mooring system 30 enables the system 1 to provide reduced environmental loads on the panels 20. When using long and thin buoyancy elements 10 with the weathervane mooring system 30, they also provide a strongly directional dependent load (wave and current) characteristic (low loads end-on, higher loads perpendicular), which reduces wave and current loads. The panels 20 can easily be raised upwards away from the water surface (increasing the freeboard) to reduce the possibility of wave loads on the panels 20.

[0049] The use of vertical or near vertical panels 20 with the system 1 drastically reduces panel cleaning requirements as there is reduced dust, dirt, bird droppings, and biofouling on the vertical or near-vertical panels 20, which is often a major issue for conventional floating solar arrays that have horizontal or near horizontal panels.

[0050] The use of an efficient mooring system enables a simpler, more reliable mooring. The mooring footprint can also be reduced compared to a conventional spread moored system as the floating solar photovoltaic system 1 of the claimed invention can float over the mooring lines 34 of the mooring system 30.

[0051] The vertical or near-vertical photovoltaic panels 20 can be mounted back-to-back or they can be bifacial panels, which capture the maximum amount of diffuse light available and also benefits from light reflected from the water surface.

[0052] In the specification the terms comprise, comprises, comprised and comprising or any variation thereof and the terms include, includes, included and including or any variation thereof are considered to be totally interchangeable and they should all be afforded the widest possible interpretation and vice versa.

[0053] The invention is not limited to the embodiments hereinbefore described but may be varied in both construction and detail.