WO2013185767A1

WO2013185767A1 - A wind turbine with a tower mounted heat exchange structure

Info

Publication number: WO2013185767A1
Application number: PCT/DK2013/050174
Authority: WO
Inventors: Jacob Karottki Falk ANDERSEN; Kim BRUUN; Jan Erik Karlskov JENSEN; Kenneth Hansen
Original assignee: Vestas Wind Systems A/S
Priority date: 2012-06-10
Filing date: 2013-06-06
Publication date: 2013-12-19

Abstract

A wind turbine with a tower; a nacelle supported by said tower; at least one unit to be cooled and arranged in the tower or the nacelle; a tower mounted heat exchange structure arranged outside the nacelle and tower; and a circuit facilitating a flow of a fluid medium between the at least one unit and the heat exchange structure. To improve thermal convection with the ambient space, the heat exchange structure comprises panels extending outwards from the tower such that a flow of ambient air can pass transversely trough the panel and thereby cool the unit.

Description

A WIND TURBINE WITH A TOWER MOUNTED HEAT EXCHANGE STRUCTURE

INTRODUCTION

The invention relates to a wind turbine comprising a tower and a nacelle supported by said tower. The nacelle houses a rotor, and the tower and/or the nacelle includes at least one unit to be cooled. An exchange structure is arranged outside the nacelle and tower and a circuit provides a flow of a fluid medium between the unit and the exchange structure.

BACKGROUND OF THE INVENTION

A wind turbine typically comprises several units which generate excessive heat. Examples of such components are gear boxes, transformers, bearings, generators, and power converters etc.

Such units are typically housed in a closed space within the tower or nacelle and heat exchange with the ambient space is limited. Often, active cooling, e.g. by use of a flow of air or a cooling liquid between the units and a heat exchanger, is necessary.

One commonly applied cooling structure for electrical components includes a fan for generating air flow around the electrical component or for generating air flow through a heat exchanger coupled to the component.

Particularly, very large wind turbines may include heat exchangers attached outside the nacelle, e.g. fixed to the roof of the nacelle. Since the nacelle is typically actively turned such that the rotor plane is always up against the wind, such roof-mounted heat exchangers also become up against the wind. The heat exchangers are therefore arranged side-by-side facing in one common direction, namely forward with respect to the nacelle and rotor plane. WO-A-0i/006121 discloses a wind turbine with air cooling by use of a tower wall as heat exchanger and US7168251 discloses a liquid cooled wind turbine with heat exchangers arranged outside the tower,

Since heat exchangers alongside of the tower, in contrast to the roof-mounted heat exchangers, are partly sheltered by the tower wall, such radiators typically lacks efficiency, and electrically powered fans must typically be applied for creating a forced flow of ambient air through the heat exchangers. This increases operation costs and makes the wind turbine more vulnerable,

SUMMARY OF THE INVENTION It is an object of embodiments of the invention to facilitate a simpler, cheaper, and potentially more reliable way of establishing cooling in a wind turbine,

In a first aspect, the invention provides a wind turbine where a tower mounted heat exchange structure comprises at least one panel having a generally planar shape and defines a plane oriented outwards from the tower. The panel is made with an open structure such that a flow of ambient air can travel transversely trough the panel,

In this way, the panel can be cooled by air which naturally flows along the outer surface of the tower without the use of artificial, forced air streams, e.g. from a fan or similar powered ventilator means attached next to the panel. Particularly, the defined plane could be non-parallel to a tangent of the tower such that the panei reaches furthest possible away from the tower and thereby becomes capable of catching natural air flow at a longer distance away from the tower.

Since the panel extends outwardly from the tower and has an open structure, the shelter effect caused by the tower has less impact on the flow of air through the panel. Accordingly, power driven fans for creating a forced air stream can be avoided. Herein, "pane/" means a heat exchanger for exchanging thermal energy between a fluid medium and ambient air and having a primarily two-dimensional shape, i.e. the panel has a largest dimension which is much larger than a corresponding smallest dimension. If the panel is square or rectangular, at least one of the length and height of the panel is much larger than the thickness of the panel. Herein, we refer to the "edge" of the panel as that side of the panel having the smallest dimension, and the "surface" of the panel is stretched by the other, larger, dimensions of the panel.

It should be pointed out that preferably the plane defined by the panel is oriented substantially in parallel with a vertical, longitudinal axis of the tower. Thus, preferably the plane of the panel has a substantially vertical orientation.

As an example, the largest dimension of the panel could be at least 5 times, such as 10- 100 times larger than the smallest dimension.

By the specification that at least one of the panels "extends outwards from the tower" is herein meant that the panel is arranged with one end of the surface towards the tower and an opposite end of the surface pointing outwards, away, from the tower. In one embodiment, the aforementioned edge, at one point, faces the tower, and at another point faces away from the tower.

The panel may have a structure corresponding to that of a traditional radiator well known in the art for heating or cooling purposes. Particularly, the panel may form an open structure, e.g. formed by a plurality of conduits for the fluid medium.

Since the panel is located outside of the tower, it may come in direct contact with seawater. Anti-corrosive characteristics may therefore be desired. The panels may therefore be partly or completely made from a non-metallic material, e.g. from a composite material or from a metal material coated with a sealing or anti-corrosive coating. To provide efficient cooling regardless of the wind direction, the wind turbine according to the invention may comprise at least two, and preferably at least three, or four panels extending in different directions outwards from the tower, e.g. equally spaced about the tower. If four panels are used, they could be located with 90 degrees spacing about the tower. If six panels are used, they could correspondingly be located with 60 degrees spacing about the tower etc.

Each panel may comprise an inlet and an outlet for the fluid medium, and the panels may extend in parallel between the inlets and outlets, in this way, the use of the panels may be controlled individually. If certain conditions makes use of selected panels more advantageous than use of other panels, these more advantageous panels may be used exclusively or primarily by reducing the flow to the less advantageous panels.

Some of the panels may, as an example, be sheltered partly by the tower in specific wind conditions or some panels may be heated by solar incident, and fluid flow to such panels may therefore be reduced or prevented. Accordingly, a flow control structure enabling adjustment of flow of the fluid medium through each panel individually may be provided . Such flow control may include valves, e.g. motor controlled valves or valves which are controlled by a thermo element

The inlet and outlet may be located in the edge of the panel, e.g. in that portion of the edge facing towards the tower.

In each panel, a passage structure may guide the fluid medium to establish spreading of the thermal energy over the surface of the panel. Particularly, the fluid medium may be guided in the panel in a direction from the tower and outwards, away from the tower. The individual flow control may be administered individually by a control system dedicated to one specific panel or by a common control system . The control system may adjust the flow based on a control input, e.g. based on an ambient temperature measured outside the tower or nacelle; an ambient wind speed; a wind direction; a temperature of the fluid medium, or other measures relevant for the usage of the panels.

To further reduce the sheltering impact of the tower on the panels, at least one, and preferably ail of the panels may be oriented relative to the tower such that they extend radially outwards from the tower. This provides space between the panels and allows a good flow through the panels.

At least one of the panels may have a size such that it extends at least one tenth of a tower diameter outwards from the tower, or even one fifth, or one half of a tower diameter outwards from the tower. The panels may be fixed to common frame, e.g. in the shape of a flange extending circumferentiaily about the tower. The frame could be movable along the tower, or it may be rotatabie about the tower until a desired position of the frame, and thus a desired position of the panels relative to the tower, is obtained. The frame may include attachment means for locking the position and thereby obtaining a rigid attachment of the frame to the tower.

To obtain a short distance between a heat generating unit inside the tower and the panels, at least one of the panels could be located at a specific height inside the tower, and at least one of the panels could be located directly outside the tower at that height such that the fluid medium should essentially flow in a horizontal plane or at least primarily flow in a horizontal plane.

At least one of the panels could be fixed to the tower by a hinge joint allowing rotation of the panel relative to the tower. The panel may thereby be moved to an orientation by which good flow properties through the panel can be obtained. The panel may include power means for moving the panel relative to the tower, and the power means may be controlled automatically, e.g. based on wind direction, temperatures measured at different locations around the tower, solar incident angle etc. At least one panel could be expandable in size, e.g. in a direction away from the tower. In this way, the capacity of the panel can be adjusted depending on the need for cooling and/or depending on the natural flow of air through the panel. The panel may include adjustment means for expanding the panel, and the adjustment means may be controlled automatically, e.g. based on wind direction, temperatures measured at different locations around the tower, solar incident angle etc.

An accumulator tank may be provided inside the tower to form buffer storage for the fluid medium. The accumulator tank may be located vertically above the panels to increase the pressure of the fluid medium in the panels.

To maintain a good convection and flow of air through the panels, the wind turbine may comprise at least one nozzle which is arranged such that it can distribute a cleaning fluid over the at least one panel. The wind turbine may e.g. comprise a row of nozzles for each panel, e.g. nozzles which are arranged adjacently or directly above the panel. The nozzles may be fed with a cleaning fluid from a pressure system such that the nozzles function as water high- pressure cleaners.

The cleaning fluid may be water, e.g. sea water pumped from the base of an offshore wind turbine, or it may be rainwater collected in the vicinity of the wind turbine, or it may be fluid of any kind stored in a storage tank in or at the wind turbine.

To detect faults in the heat exchange structure, the wind turbine may include a fault detection system adapted to select a panel based on a determined efficiency of the panel. The fault detection system may e.g. detect a

temperature or pressure differential between an inlet and an outlet for the fluid medium into and out of the panel. If the differential for one panel differs from an expected differential or from an average differential for other panels of the system, the fault detection system may select that panel for inspection. Such a selection may be communicated to a surveillance unit located outside the turbine, and further optionally, the selected panel may be excluded from the system by preventing flow of the fluid medium to that panel.

In a second aspect, the invention provides a wind turbine comprising a tower; a nacelle supported by said tower; a rotor supported by said nacelle; at least one unit to be cooled and arranged in the tower or the nacelle; a tower mounted heat exchange structure arranged outside the nacelle and tower; and a circuit facilitating flow of a fluid medium between the at least one unit and the heat exchange structure, characterised in that the heat exchange structure comprises at least one nozzle for distributing a cleaning fluid over at least a part of the heat exchange structure,

The heat exchange structure could comprise as discussed above at least one panel having a generally planar shape, The wind turbine may e.g. comprise a row of nozzles for each panel, e.g. nozzles which are arranged adjacently or directly above the panel. The nozzles may be fed with a cleaning fluid from a pressure system such that the nozzles function as water high-pressure cleaners.

The cleaning fluid may be water, e.g. sea water pumped from the base of an offshore wind turbine, or it may be rainwater collected in the vicinity of the wind turbine, or it may be fluid of any kind stored in a storage tank in or at the wind turbine. In a third aspect, the invention provides a method of cooling a unit which is located in a tower or nacelle of a wind turbine, the method comprising the steps of conducting a flow of a fluid from the unit to a panel located outside the tower and nacelle and cooling the panel by a natural flow of air along an outer surface of the tower without using an artificially forced stream of air of the kind generated by a ventilator arranged directly adjacent the panel.

The wind turbine and method according to the second and third aspects of the invention may further include any of the features and aspects described relative to the first aspect of the invention. DETAILED DESCRIPTION

In the following, embodiments of the invention will be described by way of example with reference to the figures in which :

Fig. 1 illustrates, in perspective view, a section of a wind turbine according to the invention;

Fig. 2 illustrates, in a side view, a section of the wind turbine according to the invention;

Fig. 3 illustrates a diagram of a cooling system for a wind turbine according to the invention; Figs. 4-7 illustrate different embodiments of the invention, and

Fig. 8 illustrates details of a panel including nozzles for distributing a cleaning fluid.

Further scope of applicability of the present invention will become apparent from the following detailed description and specific examples. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the scope of the invention will become apparent to those skilled in the art from this detailed description.

Figs. 1 and 2 illustrate a section of a wind turbine 1. The wind turbine comprises a tower 2 which carries a nacelle which is not shown in any of the Figs. The wind turbine further comprises a rotor (not shown) driven by wind and connected to an electrical generator for producing electricity by wind power.

Inside the tower, the wind turbine comprises different units needing cooling. More particularly, the wind turbine comprises a converter and a transformer which is located inside the tower. These two electrical components are connected to a circuit providing a flow of a cooling fluid such that the thermal energy can be released to ambient space via panels 3 arranged outside the tower. in the illustrated embodiment, the tower is fitted with 4 panels located 90 degrees displaced relative to each other about the circular cross section of the tower. In this way, wind may blow directly through the open structure of at least some of the panels irrespective of the wind direction.

The panels form peripheral frames and have an open centre structure such that ambient air can flow transversely trough the panels. Since the panels are oriented outwardly from the tower, wind can blow through the open structure without use of powered fans or other means for creating a forced air stream, and since the panels extend in different directions, any wind direction will at least create a flow of air through some of the panels.

Fig. 3 illustrates in a diagram the connection of the panels and the transformer and converter including peripheral equipment such as accumulator tank, pumps etc. The system forms a circuit facilitating flow of a fluid medium between the heat generating units 4 and the panels 3 via the flow pipe-system 5, The heat generating units 4 and the illustrated accumulator tank 11 are located inside the tower. Figs. 4-7 illustrate different embodiments. In Fig. 4, the panels 3 are shielded by a common frame to which all panels are attached. The common frame forms flanges 6 projecting radially from the tower. The flanges extend circumferentially about the tower and form oblique edges 7.

Fig. 5 illustrates a lower part of a wind turbine adapted to be located off shore on a rig foundation 8 to rest on a seabed. The panels 3 are located in a lower end of the tower, i.e. closer to the surface of the sea than to the top (not shown) and thus relatively far away from the nacelle. Figs. 6 and 7 illustrate another embodiment, where each panel 3 is attached via frames 9, 10 at an upper and lower edge of the panel. The frames have oblique top and bottom faces.

The mentioned flanges or frames to which the panels are attached may particularly protect the panels from elements which are hoisted up and down along an outer surface of the tower. For this purpose, the mentioned oblique faces or edges facilitate easy passage of such hoisted elements.

Fig. 8 illustrates a panel 3 with further details. The panel forms a rigid edge 12 and an open structure 13 centrally within the edge. The open structure allows flow of air transversely through the panel. The open structure may comprise flow passages for the fluid medium. To maintain good flow properties over time, it may be necessary to clean the panel, and particularly, to clean the open structure. For this purpose, the wind turbine comprises a cleaning system with nozzles 14 arranged to distribute a cleaning fluid over the open structure. The cleaning fluid may be fresh water or a particular detergent for dissolving insects, salt and other contaminants. The nozzles may particularly be fixed to the edge 12, and they could be adapted for high pressure provided by a pump 15, e.g. housed in the tower. To save water, the panel may collect the used cleaning fluid at the bottom of the panel. The illustrated panel may be used in a wind turbine according to the first or second aspect of the invention, or in a method according to the third aspect of the invention.

Claims

CLAIM

1. A wind turbine (1) comprising a tower (2); a nacelle supported by said tower; a rotor supported by said nacelle; at least one unit to be cooled and arranged in the tower or the nacelle; a tower mounted heat exchange structure arranged outside the nacelle and tower; and a circuit facilitating flow of a fluid medium between the at least one unit and the heat exchange structure, characterised in that the heat exchange structure comprises at least one panel (3) having a generally planar shape and defining a plane oriented outwards from the tower, the panel having an open structure (13) allowing a flow of air transversely through the panel whereby the panel can be cooled by an air flow along the tower.

2. A wind turbine according to claim 1, where the exchange structure comprises at least two panels extending in different directions outwards from the tower.

3. A wind turbine according to claim 1 or 2, where the exchange structure comprises at least four panels disposed at equal space about the tower.

4. A wind turbine according to any of the preceding claims, where each panel comprises an inlet and an outlet for the fluid medium, and where the panel extends in parallel between the inlets and outlets.

5. A wind turbine according to claim 4, where the at least one panel has an edge with a proximal portion facing towards the tower and a distal portion facing away from the tower, the inlet and outlet being arranged in the edge.

6. A wind turbine according to claim 5, where the inlet and outlet are arranged in the proximal portion of the edge.

7. A wind turbine according to claim 6, where the fluid medium is guided in the panel in a direction from the tower and outwards, away from the tower.

8. A wind turbine according to any of the preceding claims, comprising a flow control structure enabling adjustment of flow of the fluid medium through each panel individually.

9. A wind turbine according to claim 8, where the individual flow is based on at least one of: a temperature difference across the panel; an ambient temperature measured outside the tower or nacelle; an ambient wind speed ; a wind direction and a temperature of the fluid medium.

10. A wind turbine according to any of the preceding claims, where at least one panel extends radially outwards from the tower.

11. A wind turbine according to any of the preceding claims, where at least one panel extends at least one tenth of a tower diameter outwards from the tower.

12. A wind turbine according to any of the preceding claims, where each panel is fixed to a common frame forming flanges (6) projecting radially and extending circumferentia!ly about the tower.

13. A wind turbine according to claim 12, where the common frame is movable along the tower.

14. A wind turbine according to any of the preceding claims, where at least one panel and the unit are located at generally the same vertical height.

15. A wind turbine according to any of the preceding claims, where at least one panel is joined to the tower by a hinge allowing rotation of the panel relative to the tower.

16. A wind turbine according to any of the preceding claims, comprising an accumulator tank (11) for the fluid medium, the accumulator tank being located in the tower.

17. A wind turbine according to any of the preceding claims, comprising at least one nozzle (14) for distributing a cleaning fluid over the at least one panel.

18. A wind turbine according to any of the preceding claims, further comprising a fault detection system adapted to select a panel based on a determined efficiency of the panel.

19. A wind turbine according to claim 18, where the fault detection system is adapted to prevent flow of the fluid medium to a selected panel.

20. A wind turbine according to claim 18 or 19, where the fault detection system is adapted to communicate with an external surveillance unit and to notify about selected panels.

21. A wind turbine (1) comprising a tower (2); a nacelle supported by said tower; a rotor supported by said nacelle; at least one unit to be cooled and arranged in the tower or the nacelle; a tower mounted heat exchange structure arranged outside the nacelle and tower; and a circuit facilitating flow of a fluid medium between the at least one unit and the heat exchange structure, characterised in that the heat exchange structure comprises at least one nozzle (14) for distributing a cleaning fluid over at least a part of the heat exchange structure.

22. A method of cooling a unit which is located in a tower or nacelle of a wind turbine, the method comprising the steps of conducting a flow of a fluid from the unit to a panel located outside the tower and nacelle and cooling the panel by a natural flow of air along an outer surface of the tower without using an

artificially forced stream of air.