WO2011120521A1

WO2011120521A1 - Foating foundation equipped with two primary wind turbines

Info

Publication number: WO2011120521A1
Application number: PCT/DK2011/000019
Authority: WO
Inventors: Per Uggen
Original assignee: Individual
Current assignee: Individual
Priority date: 2010-03-31
Filing date: 2011-03-22
Publication date: 2011-10-06
Anticipated expiration: 2012-09-30
Also published as: DK201000268A

Abstract

The construction is characterized by a floating foundation (1), which is equipped with two primary wind turbines (2). Or a floating foundation which is equipped with two primary wind turbines, together with one or more secondary wind turbines, which is placed at an anchorage (3), with one or more anchor or mooring lines. The purpose of the construction is to reclaim kinetic energy from the wind at sea, and send the electric energy to consumers ashore. The two main turbines that may be similar or different in size are called the two primary wind turbines. The two primary wind turbines are characterized by supplying more that 80% of the total energy that is produced by the invention. In addition to the two primary wind turbines, there may be smaller wind turbines (s) installed on the same floating foundation, These wind turbines (s), produces less that 20% of the total energy produced by the invention.

Description

FLOATING FOUNDATION EQUIPPED WITH TWO PRIMARY WIND TURBINES Technical field of the invention.

The present invention relates to a floating foundation fitted with two primary windmills or wind turbines. The floating foundation is constructed in a manner where the foundation has an identifiable freeboard, as a vessel, in a ships technic- al sense, so that the floating foundation can be defined as a vessel, due to the definition stipulated in rule number 3 under the "Convention on the International Regulation for Preventing Collisions at Sea, 1972 (COLREGs)".

The objective of the design is that the floating foundation is maintained at an an- chorage, with a relatively modest construction draft, at an almost geostationary anchor position, with one or more anchors or mooring lines or by alternative solutions, in salt water or in fresh water. By using different anchoring techniques the two primary wind turbines can be kept out of one another's shelter or wind shadow since the floating foundation can be turned horizontally relative to the best given direction of the wind.

The purpose of the construction is to reclaim kinetic energy from the wind at sea and send this energy to consumers ashore, in much the same way, as all other offshore wind farms and offshore windmills or offshore wind turbines do. The in- vention includes a floating foundation mounted with two primary wind turbines, or with two primary wind turbines and one or a number of secondary wind turbines. The wind turbine rotors that can be fitted on horizontal or vertical drive shafts do not serve any other purpose than to reclaim kinetic energy from the wind. The expression "primary wind turbine" defines two - and only two - windmills or wind turbines, which overall produce more than 80% of the total energy that is supplied by the invention. The two primary turbines may be similar or different in size. Secondary turbine(s) in relation to the invention is defined as one or more windmills or wind turbines fitted on the same floating foundation, together with the two primary wind turbines. The secondary turbine(s) can only produce a maximum of 20% of the energy that the invention is designed to produce.

The purpose of installing one or more secondary wind turbines that produce less than 20% of the total energy, which the floating foundation produces, is to exploit the wind from the areas not covered by the two primary wind turbines. The secondary turbine(s) will also provide vital backup power supply under stoppages, where the primary wind turbines are out of service. Background of the invention. As a fact, the world market price for energy and fossil fuel is historically high.

And the possibility of placing several more wind turbines on land faces great public oppositions. For example claims for financial compensation from the nearest neighbors. Inconveniences from wind turbines often cause fragile ecosystems con- siderable strain, in addition to the visual and the noise related inconvenience that these wind turbines also causes to the landscape. This makes alternative solutions and locations for wind turbine economically and technically more interesting.

In relation to this invention, the investment in a floating foundation is a modest additional cost in relation to the total investment in wind turbine technology. Especially if you look at the investment in offshore wind turbines, the investment will be almost the same in a floating foundation, with a total capacity of 6 MW or more, as the comparable cost for solid foundation for two conventional offshore wind turbines. In some cases, the investment in a floating foundation will even provide a better economic return, than the comparable cost when you establish two traditional solid foundations. Based on known technique for wind turbine designs, it is estimated that a floating foundation, as described in this invention, with two primary offshore windmills, under favorable wind conditions, could produce electricity corresponding to more than 6 MW, for the largest floating foundations.

It is also an assessment that several floating foundations, as in the invention, anchored with an individual distance of 0.5 km, at an area corresponding to 100 square kilometers (km²) = (10 x 10 km) = (441 floating foundations) could produce energy in a quantity larger, than what is currently produced by Hover Dam, which means more than 2080 MW. This must be compared to Lake Mead, which as water reservoir to Hover Dam fills an area of 639 (km²). Compared to Hover Dam, Lake Mead uses an area more than 6.5 times greater than needed by this invention, in order to gain a comparable amount of electricity. In relation to the total electricity consumption in Denmark, which amounts to about 32.5 x 10⁶ MW each year, calculated on an average capita consumption of about 6,500 kWh each year, 700 floating 6 MW plants or even less, could produce electricity in a quantity corresponding to the total electricity consumption for 5 million people, if one assume the most favorable wind conditions.

This is to say, that the wind that blows over an area of less than 20 square kilometers (km²) could cover the electricity consumption for 5 million people. In relation to the invention, this should be considered in a global energy perspective. The next problem, which is also solved by the invention, is the logistics in connection with installation, maintenance, and a time frame of 25 - 30 years or more and the ecological impact from offshore windmills on sensitive geographic locations.

The invention makes it easy to reposition wrongly positioned wind farms, since the invention is easily moved to better geographic locations, or less sensitive environmental locations. This is achieved according to the invention, since the floating foundation and the offshore wind turbines being built and fitted at a shipyard or alongside a quay in a harbour. After construction of the floating foundation, this will be towed to the anchorage, where the invention will extract electric energy.

In relation to maintenance of the floating foundation, the foundation could provide a platform for maintenance work, and it could also serve as a platform for supporting a crane or a mobile crane so that this can help service the wind turbines. It will also be easier to dismantle the turbine rotor for replacement or repair. Alternatively the individual floating foundations can be disconnected from the electrical grid and then towed to port. Or it can go to a shipyard for repair or related major or planned maintenance.

Description of related art.

The standpoint of the known techniques, used to exploit kinetic energy to electric energy at sea is, that the majority of all offshore windmills or wind turbines today stand on a foundation, that rest on the seabed. The foundation then is in contact with, or immersed into, or framed into the seabed. In regards to offshore wind turbines, on floating foundations, where the foundation does not rest on the seabed, the standpoint for the techniques used in the two known and realized projects is, that they are constructed in such a manner, that the wind turbines must be anchored at great sea depth. The construction is such, in the known projects, that a large part of the foundation is a counterweight, which essentially lowers the centre of gravity. This gives the floating foundation a substantial draft. The foundation, in the two realized projects, is only fitted with one wind turbine.

For the construction of traditional offshore wind turbines, which stands on the seabed, the known techniques are significantly limited by water depths, where the wind turbines are considered established. Another problem is that an established traditional offshore windmill or offshore wind turbine is not easy to move once it is established. This means that all installation or mounting and subsequent that all services must be conducted on the position where the wind turbine is physically positioned, which is very expensive. A third problem is, that when an offshore wind turbine must be located at the same position, standing on the seabed for 25-30 years or more, it is associated with significant problems to obtain approval from authorities and different groups of interest. A problem which is made larger by the fact that most of the appropriate geographic locations where wind turbines can be located at sea, also is identified to be some of the ecologically most sensitive areas. Geographic locations that are important breeding areas for fish and important food sources for other fish and animals associated with the ecosystem.

If compared to other known solutions with floating foundations, fitted with several windmills or wind turbines, these are all characterized by one or more wind turbines, that creates a wind shadow or wind shelter against other windmills or wind turbines on the same floating foundation.

Thus there are described several solutions or inventions with several offshore wind turbines, on the same floating foundation. Other known solutions with floating foundations are, that the foundation has other technical purposes for the abstraction of energy. So that the primary purpose might be abstraction of wave energy and the wind turbines therefore only serves a secondary role in relation to abstraction of energy. Summary of the invention.

According to the following aspects of the present invention, the construction is characterized by a floating foundation, which is equipped with two primary wind turbines. Or a floating foundation which is equipped with two primary wind tur- bines, together with one or more secondary wind turbines, which is placed at an anchorage, and anchored almost geostationary, with one or more anchors or mooring lines. The purpose of the construction is to reclaim kinetic energy from the wind at sea, and then send the electric energy to consumers ashore. The two main turbines that may be similar or different in size are called the two primary wind turbines. The two main or primary wind turbines are characterized by supplying more than 80% of the total energy that is produced by the invention.

In addition to the two main or primary wind turbines, there may be one or a num- ber of smaller wind turbines of various types installed on the same floating foundation. The wind turbine(s), which is called secondary wind turbine(s), produces less than 20% of the total energy, which is produced by the invention. The primary and the secondary wind turbines are a type of windmill or wind turbine, whose main purpose is to reclaim kinetic energy from the wind, and trans- form this energy into electricity. The rotors which can be fitted on horizontal or vertical drive shafts do not serve any other purpose than to exploit kinetic energy.

When the two primary wind turbines and the secondary wind turbine(s) are fitted, it is ensured that the wind turbine rotors can freely rotate without coming into physical contact with other wind turbine rotors. A distance between wind turbines that can also be achieved by the use of different tower or mast heights, or by the use of two different turbine sizes for the two primary wind turbines.

By using different techniques for anchoring the floating foundation, the two prima- ry wind turbines can be kept out of one another's shelter or wind shadow, since the floating foundation can rotate horizontally to the best direction of the wind. This gives a unique opportunity to place the two primary wind turbines into the best position, relative to actual direction of the wind, so that the two primary wind turbines provides maximum electric effect or capacity.

The invention is further identified by an identifiable freeboard. The construction will be designed to create economic healthy solutions for cheaper floating foundations for even bigger offshore wind turbines. Affordable solutions that will support an ever expanding desire to exploit renewable energy from offshore wind turbines.

Brief description of drawings.

The invention will be better understood, from the text in this description, if the text is read in connexion with the drawings, in which:

Fig. 1

A floating foundation (1) fitted with two windmills (wind turbines) (2), comprising rotors (a), nacelles (b) and towers or masts (c), mounted on a floating foundation (here shown as a traditional barge) (1). The floating foundation is held in a geo- stationary position at sea by mooring lines connected to anchors or by anchor chains (3). The floating foundation can swing or turn horizontally to the best given direction of the wind due to the arrangement of mooring lines (3) or anchor chains. The floating foundation with primary wind turbines is designed for offshore use, where it will convert wind energy into electrical power. Then the electrical power is being transferred to shore by an electrical submerged offshore cable lying on the seabed or buried into the seabed. Fig. 2

Shows the primary wind turbine (2) vertical centre of gravity, the tower (c), which is hanging outside the floating foundation, where an arm (d), holds the primary wind turbine fitted on to the floating foundation (1). The construction lifts the vertical center of gravity for the wind turbine (2) outside the floating foundation.

Fig. 3

Show the same construction as in Fig. 2. The floating foundation (1) is seen from above, with the primary wind turbine, nacelle (b), hanging or standing on the arm (d). Fig. 3 is also showing the anchoring arrangement (3).

Fig. 4

Shows a floating foundation (1) seen from above, where the primary wind turbines (2) are placed on a diagonal line on the foundation.

Fig. 5

The figure shows a floating foundation (1) with a different geometrical, symme- trical or non symmetrical shape. The primary wind turbines (2) are placed on a centre line. The floating foundation (1) is seen from above.

Fig. 6

The figure shows that a floating foundation (1) can be given symmetrical and non symmetrical shapes. The primary wind turbines (2) are placed on a diagonal line. The floating foundation (1) is seen from above.

Fig. 7

The floating foundation is shown with two primary wind turbines (2), and one, (or more than one), secondary wind turbine(s) (4) on the same floating foundation

(1) . The two primary wind turbines (2) are characterized by producing more than 80% of the total energy, which is produced by the floating foundation (1).

The secondary wind turbine(s) (4) is characterized by producing less than 20% of the energy, which the invention produces from the wind. The secondary wind tur- bine(s) (4) also serves as backup to the floating foundation, with electric power during operation, service, stoppages or breakdowns on the primary wind turbines

(2) . Different arrangements of anchors, mooring lines or other means of anchoring techniques which can be used, enables the floating foundation to turn horizontally to the best given direction of the wind. In such a manner that the primary wind turbine rotors are not in shelter of each other, which secure maximum electric production capacity. Fig. 8

The figure shows 2 images of a model, with a planned design for the invention. Two pontoons or two hulls are connected by a set of girders. This design will form the floating foundation for the two primary 3 MW wind turbines, making the total production capacity for this specific floating foundation 6 MW.

The approximate dimension of the floating foundation will be a draft of 3 - 4 me- ters with a total length of 120 meters, a width of 70 meters, which is the length of the two pontoons or hulls, and an air draft of approximately 120 meters. Air draft defined as the distance from the tip of the wing to the surface, when the tip of the wing is furthest from the sea. Descriptions of embodiments.

The embodiment of the invention will hereinafter be the floating foundation, fitted with the two primary wind turbines and / or the secondary wind turbine(s), which will be explained with reference to the drawings and images shown from Fig. 1 until Fig. 8. The invention consists of a floating foundation (1) equipped with two primary wind turbines (2) and / or the secondary wind turbine(s) (4).

The floating foundation (1) is constructed, as a floating frame, that consist of one or more hulls or pontoons, as single hull construction or pontoon construction, or a catamaran construction, or a trimaran construction, or other multi hull or multi pontoon constructions, which are then put together into one unit, as one floating foundation (1), that supports the two primary wind turbines (2) and / or the secondary wind turbine(s) (4). The two main wind turbines (2), which may be similar or different in size, are called the two primary wind turbines. The two primary wind turbines are characterized by supplying more than 80% of the total energy that is produced by the invention. In addition, there may be one or a number of smaller wind turbines (4) installed on the same floating foundation, which produces less than 20% of the electric energy produced by the floating foundation. These wind turbines are called secondary wind turbines.

The two primary wind turbines (2) and the secondary (4) wind turbine(s), being a type of windmill or wind turbine, whose main purpose is to reclaim kinetic energy from the wind, and transform this energy into electricity. The rotor that is fitted, either on a horizontal or a vertical drive shaft, do not serve any other purpose than to exploit kinetic energy. When mounting the primary wind turbines (2), one must ensure, that the distance between the wind turbines is such, that the wind turbine rotors (a) can freely ro- tate, without the wind turbine rotors thereby coming into physical contact with other wind turbine rotors. This distance can also be achieved by using different tower or mast heights or by using two different wind turbine sizes for the two primary wind turbines (2). By only mounting two primary wind turbines (2) and by using different techniques for anchoring the floating foundation (1), at the anchorage, this will help ensure that the primary wind turbines (2) does not stand in shelter or wind shadow of each other, since the floating foundation (1) can be rotated or swiveled horizontally, clockwise or counterclockwise, to the best given direction of wind. This will bring the two primary wind turbines (2) in a position, relative to actual direction of the wind, where both the two primary wind turbines provide maximum electric capacity, which is unique for the invention.

According to the invention, the normal problem when positioning offshore wind turbines most appropriate, is solved by constructing a floating frame that consist of one or more hulls or pontoons which are then put together into one unit, which then can be located by means of anchoring, at an anchorage, where those inconveniences, mentioned prior in this document, to the environment and neighbors are minimized. Geographical places, which from an ecological point of view does not show equal sensitivity to wildlife or to ecological sensitive coastal areas. In relation thereto, the invention can be constructed to have a design draft of less than 2 meters, if the proposed anchorage locations have very limited sea depth.

Compared to the standpoint of other floating foundations, the invention is charac- terized by the configuration of two primary wind turbines on one floating foundation, which is the technical solution in relative terms, which give the most foundation compared to the cost.

By placing three primary wind turbines (2) onboard the same floating foundation, using known technical solutions, you would be forced to put one or more wind turbines (2) in such a way, that they come into the shelter or wind shadow of each other, reducing the wind turbines full electric capacity.

If the floating foundation (1) were designed, to be double in length, in order to give room for three primary wind turbines (2) in a straight line. Wind turbines which stand side by side, this would roughly lead to the double cost when producing one floating foundation (1). Double production cost in order to give, a floating foundation (1), access to 50% more electric production capacity. The floating foundation (1) will also be able to serve as platform for various technical installations. These installations can either go inside the hull or pontoon, in- side the floating foundation (1) or these installations can be placed on deck. Either as individual units on deck or mounted in containers, which are standing directly on the deck or standing in container brackets on the deck of the floating foundation. This refers to manning facilities, diesel generator needed for yaw gears and brakes, transformer, cable connections, tools, ballast tanks, workshop, rafts, etc.

As for the construction of the floating foundation (1) and the wind turbines (2), it is not a requirement in this description, but these items should be designed, with a strength and stability, so the invention can withstand even the most extreme wind and wave conditions, corresponding to the design requirements for stress and maximum wind speed, as applicable for offshore wind turbines. It is therefore important, that the longitudinal respectively the transverse metacentric height is of such a physical nature and size, that the limitation of weather is only determined by the offshore wind turbine design. Similar design and classification requirements should obviously also apply to anchors and chains or mooring arrangements. This even though this will not be a detailed requirement stipulated in this description.

In addition thereto, it is a well known principle at shipyards, that ships produced in series, consisting of several identical units, can be made cheaper. By transferring this production method, to the production of the floating foundations, this method will significantly reduce the overall cost when producing hulls, pontoons, towers or masts, which would make the individual floating foundation cheaper and therefore more cost effective.

In addition, the invention is a low technology design, apart from the wind turbines (2) and rotors (a). It is basically a simple task to create a traditional floating foundation with two primary wind turbines (2), which in turn means that these can be produced at virtually all shipyards worldwide, and hence be mass produced to a very modest cost. Especially when one considers that the individual components need not to be dimensioned for road transportation, but can be put together in very large units.

In this way, the invention obtains to remove, some of the current physical limita- tions when sizing wind turbines in such a manner, that larger wind turbine units can be produced in the future.

Claims

Patent claims. Claim 1 is characterized by a floating foundation (1) fitted with two, and only two, primary wind turbines (2). The two primary wind turbines (2) produce more than 80% of the energy that is being produced by the floating foundation (1). The primary wind turbine (2), being a type of windmill or wind turbine whose main purpose is to exploit kinetic energy from the wind, and transform this energy into electricity. The rotors serve no other purpose than to exploit kinetic energy. The floating foundation (1) and the two primary wind turbines (2) are then placed at an anchorage, at an almost geostationary anchor position, where it exploits kinetic energy from the wind. By using different techniques for anchoring (3), the floating foundation (1) can be rotated horizontally, clockwise or counterclockwise, to the best direction of the wind, so that the two primary wind turbines (2) does not stand in shelter or wind shadow of each other. This will bring the two primary turbines (2) in a position, relative to the actual direction of the wind, where both wind turbines can provide maximum electrical capacity, when the floating foundation (1) is in service. Furthermore the floating foundation (1) have two or more mooring points (3) on the floating foundation, with separate points of attack (3), two or more points of mooring positions (3) with individual distance from one another, when the floating foundation is moored (3) or anchored (3) to the seabed, at the anchor position. The floating foundation (1) also have two or more fix points on the seafloor for its anchors, anchor buoys or its dolphins, or combina- tion hereof, that are separated with a distance from one another, when the floating foundation (1) is at its anchor position, connected to the land based power supply system. The floating foundations (1) serve no transportation purposes, as a normal ship, when they are being located at the anchorage, at the anchor position. Energy is subsequently sent ashore by power cable or by a submerged elec- trical offshore cable, connecting the anchorage, with the floating foundation (1), with a land based power supply system, connecting the floating foundation (1) with electrical consumers ashore. Further the floating foundation (1) with its two primary wind turbines (2), have its centre of gravity above its centre of buoyancy. This being with no regards to whether or not the floating foundation (1) is con- nected or disconnected to the land based power supply system, or if it is under transportation from harbour, shipyard or from its anchorage position. Further the distance between and the position of the centre of buoyancy and the position of the centre of gravity can remain the same, regardless of whether the floating foundation (1) is being connected or disconnected to the land based power supply system. Patent claims. Claim 2 that relate to claim 1 is characterized by, that there in addition to the two primary wind turbines (2), is fitted one or more secondary wind turbine(s) (4) on the same floating foundation (1). The secondary wind turbine (4) or the secondary wind turbines are defined to produce less than 20% of the total energy, which the floating foundation (1) is designed to produce. The secondary wind turbine(s) (4) can serve as auxiliary back up for the two primary wind turbines (2) under stoppages.

Claim 3 that relates to claim 1 and 2 is characterized by, that the windmills mentioned can be any type of windmills, whose main purpose is to exploit kinetic energy from the wind, and transform this energy into electricity.