EP4716802A1 - Improvements relating to cooling wind turbines - Google Patents

Abstract

A wind turbine cooling system comprising: a coolant circuit adapted to convey coolant between a first heat exchanger arranged to cool coolant flowing through the coolant circuit; and a second heat exchanger arranged to heat coolant flowing through the coolant circuit; a coolant pump adapted to pump coolant around the coolant circuit; a first flow control valve having first and second ports, wherein coolant flows between the first and second ports along the coolant circuit in a cooling mode of operation, the first flow control valve further having a third port to which is connected an expansion tank, and a fourth port adapted for connection to a coolant filler tank; a second flow control valve having first and second ports, wherein coolant flows through the first and second ports during the cooling mode of operation. The second flow control valve further includes a third port, wherein coolant flows between the second and third ports during a bypass mode of operation in which coolant bypasses the first heat exchanger, and a fourth port adapted for connection to a coolant filler tank. Beneficially, three modes of operation of the system are achieved with only two four-way valves and a single pump, which represents a significant reduction in complexity and cost over known systems of comparable functionality.

Description

IMPROVEMENTS RELATING TO COOLING WIND TURBINES

Technical Field

This disclosure relates to systems, apparatus and methods adapted to control the temperature of components of a wind turbine generator.

Background

The components housed in the nacelle of a wind turbine generator, such as the electrical generator and power converter, operate most effectively within respective optimal temperature bands. Accordingly, selective cooling and/or heating systems are required to regulate the temperatures of these components.

Recirculating coolant systems for wind turbines are known in which waste heat generated by wind turbine components, for example components located in a nacelle of the wind turbine, is transferred to a working fluid, or coolant, which then dissipates the heat to surroundings by a suitable heat exchanger. A pump moves the working fluid around a coolant circuit comprising a network of pipes and valves, which coolant circuit enables the coolant to travel between the components and to dissipate heat. The working fluid within the coolant circuit may be pressurised, although this need not be the case.

In one known system, a main heat exchanger is located on top of the nacelle in a prominent position which enables air to flow through the heat exchanger. Such an arrangement is known as a ‘cooler top’ design. To enable cooling to be applied selectively such that the system can operate in a warming mode, for example in cold start conditions, and a normal of ‘cooling’ mode, known systems rely generally on three- way valves to control whether the working fluid flows through or bypasses the cooling device. Further valves can be included in the system to provide suitable air bleed points, and tapping points. Such tapping points can be used to connect to a filler tank to enable the cooling system to be filled before first use, or to enable coolant to be added to the system, for example after a coolant leak. Hydraulic valves that have the required performance are complex and costly to manufacture and maintain so there is a drive to reduce system complexity and cost, whilst maintaining or improving system performance. It is against this background that the invention has been devised.

Summary of the Invention

According to a first aspect of the invention, there is provided a wind turbine cooling system comprising: a coolant circuit adapted to convey coolant between a first heat exchanger arranged to cool coolant flowing through the coolant circuit; and a second heat exchanger arranged to heat coolant flowing through the coolant circuit; a coolant pump adapted to pump coolant around the coolant circuit; a first flow control valve having first and second ports, wherein coolant flows between the first and second ports along the coolant circuit in a cooling mode of operation, the first flow control valve further having a third port to which is connected an expansion tank, and a fourth port adapted for connection to a coolant filler tank; a second flow control valve having first and second ports, wherein coolant flows through the first and second ports during the cooling mode of operation, the second flow control valve further having a third port, wherein coolant flows between the second and third ports during a bypass mode of operation in which coolant bypasses the first heat exchanger, and a fourth port adapted for connection to a coolant filler tank.

An advantage of the cooling system as defined above is that the three modes of operation of the system are achieved with only two four-way valves and a single pump. Typically, known schemes use a combination of two-way valves, three-way valves and an auxiliary filling pump to achieve the same functionality. Compared to existing schemes, therefore, the examples of the invention reduces the number of valve components used and also the number of pumps, which results in a less complex system that is lighter and less costly, which are important considerations in the design of such systems and the realisation of a reduction in system complexity is not straightforward to achieve for a skilled person.

The invention extends to a method of using the cooling system, specifically for charging the cooling system with coolant, comprising connecting the filler tank to a fourth port of the first flow control valve, and connecting the return pipe to the fourth port of the second flow control valve and arranging a discharge end of the return pipe to discharge into the filler tank. Once the filler tank is connected, a maintenance worker may then configure the first flow control valve to connect the filler tank to the coolant circuit, either by manual or computerised means, and then configure the second flow control valve to connect the return pipe to the cooling circuit. Finally, the maintenance worker may operate the pump to fill the coolant circuit with coolant from the filler tank.

The invention may further be expressed as a method of adapting a cooling system, that system comprising a coolant circuit adapted to convey coolant between a first heat exchanger arranged to heat coolant flowing through the coolant circuit and a second heat exchanger arranged to cool coolant flowing through the coolant circuit; a coolant pump adapted to pump coolant around the coolant circuit; a first flow control valve having first and second ports, wherein coolant flows between the first and second ports along the coolant circuit in a cooling mode of operation, the first flow control valve further having a third port to which is connected an expansion tank, and a second flow control valve having first and second ports, wherein coolant flows through the first and second ports during the cooling mode of operation, the second flow control valve further having a third port, wherein coolant flows between the second and third ports during a bypass mode of operation in which coolant bypasses the second heat exchanger.

In the context of such a system, the method comprises forming, for example by drilling, boring or machining, in the first flow control valve a fourth port in addition to the first, second, and third ports thereof, forming in the second flow control valve a fourth port in addition to the first, second and third ports thereof. In effect, therefore, the inventors have recognised that three-way valves can be adapted to be four-way valves and such an adaptation can be performed in-situ within the wind turbine. This is particularly the case where the three-way valves to be adapted are in the form of a T-port ball valve and an L- port ball valve.

Once the flow control valves are so adapted, the method may further comprise connecting a filler tank to the newly formed fourth port of the first flow control valve, connecting a return pipe to the newly formed fourth port of the second flow control valve and arranging a discharge end of the return pipe to discharge into the filler tank; configuring the first flow control valve to connect the filler tank to the coolant circuit; and configuring the second flow control valve to connect the return pipe to the cooling circuit.

Further optional and advantageous features are set out in the dependent claims and in the detailed description that follows. Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all examples and/or features of any example can be combined in any way and/or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner.

Brief Description of the Drawings

The above and other aspects of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a schematic view of a wind turbine including a cooling system;

Figure 2 is a schematic view of the cooling system in more detail, and configured in a first or ‘cooling’ mode of operation;

Figure 3 is a schematic view of the cooling system in Figure 2, configured in a second or ‘bypass’ mode of operation;

Figure 4 is a schematic view of the cooling system in Figure 2, configured in a third or ‘charging’ mode of operation.

Detailed Description

A specific embodiment of the invention will now be described in which numerous features will be discussed in detail in order to provide a thorough understanding of the inventive concept as defined in the claims. However, it will be apparent to the skilled person that the invention may be put into effect without the specific details and that in some instances, well known methods, techniques and structures have not been described in detail in order not to obscure the invention unnecessarily. In general terms, the examples of the invention described here provide systems and corresponding methods for selectively cooling components housed within the nacelle of a wind turbine generator, although in principle embodiments of the invention could be used to cool any components requiring thermal control.

The approach involves a coolant circuit that incorporates a cooling heat exchanger that is mounted on the top of a nacelle in a so-called ‘cooler top’ configuration. The cooling heat exchanger or ‘radiator’ is fluidly connected by a main system pump to a further heat exchanger or heating device that is housed within the nacelle. The heating device is thermally coupled to at least one heat-generating component of the wind turbine to transfer thermal energy away from the at least one heat-generating component to the coolant flowing within the heating circuit, thereby cooling the heat-generating component. A bypass line provides a bypass flow path through which coolant can flow in preference to flowing through the radiator, wherein flow through the bypass line is controlled by a flow control valve. Beneficially, the coolant circuit is provided with flow control valves which are adapted in an effective way to achieve flow control objectives reliably whilst avoiding the use of an excessive number of valves, thereby resulting in a lower cost and higher reliability system. The flow control valves are adapted to connect to a filler tank which, in a charging mode of operation, function to fill or charge the coolant circuit with coolant. No further valves are required for this purpose, which reduces system complexity. Furthermore, the system pump is used to charge the system, by virtue of the configuration of the valves, which avoids the need for an additional charging pump.

In order to place the embodiments of the invention in a suitable context, reference will firstly be made to Figure 1 , which illustrates a typical Horizontal Axis Wind Turbine 1 (HAWT) comprising a tower 2, a nacelle 4 rotatably coupled to the top of the tower 2, a rotating hub or ‘rotor’ 6 mounted to the nacelle 4 and a plurality of wind turbine rotor blades 8 coupled to the rotor 6.

The rotor 6 is connected to a power generation system 10 housed within the nacelle 4. The power generation system 10 comprises components required to convert rotation of the rotor 6 into electricity, including a drive train, a generator and one or more transformer(s), converter(s), bearing(s) and brake(s), none of which are shown here for brevity. However, the skilled person would understand that these are conventional components of a wind turbine power generation system. A down conductor 12 is connected to the power generation system 10 to transport power to a distribution network (not shown). It should be noted that the wind turbine described here may be installed in an offshore or an onshore location and the specific type of wind turbine is not central to the invention.

The wind turbine also includes a cooling system 20 which is shown here as being housed at least partly within the nacelle 4. This is because most of the heat-generating components are housed within the nacelle 4.

The cooling system 20 comprises a first heat exchanger or ‘heating device’ 22 that is coupled thermally to at least one component of the power generation system 12, and a second heat exchanger or ‘cooling device’ 24 that is positioned so it is exposed to a cooling airflow. In this example, the second heat exchanger 24 is located on top of the nacelle 4 in a ‘cooler top’ configuration which is known in some wind turbine designs.

A coolant circuit 26 pumps coolant between the first and second heat exchangers 22,24 and, in doing so, transfers thermal energy absorbed by the first heat exchanger 22 to the second heat exchanger 24. Such a configuration is generally known in the art.

Whilst Figure 1 provides a general overview, Figure 2 shows the cooling system 20 in more detail.

In overview, the cooling circuit 26 comprises a primary cooling loop 28, a secondary cooling loop 29 a pump 30, an expansion tank 32, a first flow control valve 34, a second flow control valve 36 and a temperature sensor 38. Also provided is a controller 40 which is adapted to control one or both of the first and second flow control valves. As such, the controller 40 is adapted to receive one or more operational parameter signals 42 and to implement a suitable control algorithm thereby outputting one or more control signals 44 to the first and/or second flow control valves 34,36.

The cooling circuit 26 is configured to convey a working fluid to and from the first heat exchanger 22. The working fluid may be a known coolant, for example glycol or mineral oil.

The first heat exchanger 22 is thermally coupled to at least one component 46 of the wind turbine which generates heat and therefore has a requirement for cooling. The heat generating component 46 may be at least one of: a generator; a gearbox; a power converter; an oil cooler; an electronics cabinet; a hydraulic pump; a yaw drive. Although only one heat generating component 46 is illustrated in the figures, it should be noted that the coolant circuit 26 may suitably be adapted to connect to further heat-generating components.

The first heat exchanger 22 may take various forms. For example, in the case of the heat generating component 46 being a generator of the wind turbine, the first heat exchanger 22 may be composed of one or more pipes, passageways, conduits or cavities which pass through the generator which serve to transfer thermal energy from the generator to the working fluid passing through those passages. Further, the first heat exchanger 22 may interface thermally with the heat generating component 46 by way of an air-to- coolant or a coolant-to-coolant interface as is conventional in heat exchanger technology. Functionally, the first heat exchanger 22 transfers thermal energy from the heatgenerating component 46 to the coolant flowing through the first heat exchanger 22, thereby cooling the heat-generating component 46.

The second heat exchanger 24 is an air-to-coolant heat exchanger in this example, as is known generally in the art. Functionally, the second heat exchanger 24 transfers thermal energy from the coolant flowing through it to the airflow to which it is exposed. Other configurations may achieve the same function and are considered to be encompassed by the term ‘heat exchanger’.

The pump 30 is any suitable fluid pump that is adapted to pump coolant around a coolant circuit. Preferably, the pump 30 is a high capacity pump due to the typical demands of cooling the heat generating components of a wind turbine, of which there may be many. By way of example, the pump 30 may have a flow rate that is between approximately 200L/min and 1000L/min, for example greater than 300L/min, optionally greater than 400L/min, and optionally greater than 600L/min. In a similar manner, the coolant circuit 26 preferably is sized to cope with the coolant demands and, in this respect, may have a coolant capacity between 300L and 1200L, for example greater than 400L, optionally greater than 500L and optionally greater than 800L.

The expansion tank 32 is provides by any suitable vessel that can contain coolant and provide a means for the coolant within the coolant circuit to expand in volume thereby causing the coolant to expand into the expansion tank 32. Each of the first and second flow control valves 34,36 is a four-way valve, as is indicated in Figure 2. In the specific example shown, the first flow control valve 34 is a four-way T- port ball valve, whereas the second flow control valve is a four-way L-port ball valve. Such valve types are generally known in the art.

In Figure 2, the cooling system 20 is configured to be in a cooling mode of operation, in which coolant flows around the primary loop 28 of the control circuit 26, as indicated by the arrows F1. As such, coolant flows from the pump 30 through a first pipe 50 to an inlet 22a of the first heat exchanger 22, and out of an outlet 22b of the first heat exchanger 22 through a second pipe 52 to an inlet 24a of the second heat exchanger 24. From the second heat exchanger, 24, coolant flows from its outlet 24b through a third pipe 56 to the second flow control valve 36 whereupon coolant then flows from the second control valve 36 through pipe 58 to the first flow control valve 34 and back to the pump 30.

As can be seen from Figure 2, each of the first flow control valve 34 and the second flow control valve 36 has four ports. Referring firstly to the first flow control valve 34, the ports are numbered P11 , P12, P13 and P14. Likewise, in respect of the second flow control valve 36, the ports are numbers P21, P22, P23, and P24.

Port P11 of the first control valve is connected to the expansion tank 32. Port 12 is connected to port P21 of the second control valve via pipe 58. Port P14 is connected to an inlet 30a of the pump 30. Port P13 is shown as not connected in Figure 2 but, as will be described later, is adapted to be connectable to a filler tank.

Turning to the second flow control valve 36, port P21 is connected to port P12 of the first flow control valve 34, whereas Port P22 is connected to the outlet 24b of the second heat exchanger 24 via pipe 56.

Port P23 is shown as not connected in Figure 2 but, as will be described later, is adapted to be connectable to a filler tank. Port 24 is connected to a bypass pipe 60 which connected to pipe 52 at a junction 62 which extends between the outlet 22b of the first heat exchanger and the inlet 24a of the second heat exchanger 24. It should be appreciated that the bypass pipe 60 provides a means for coolant to circulate without passing through the second heat exchanger 24. In Figure 2, it will be noted that the in the cooling mode of operation shown here, the first flow control valve 34 is configured such that ports P11 , P12 ad P14 are fluidly connected by virtue of the T-shaped flow control element that is part of the valve and which is depicted centrally in the valve symbol and which is considered standard nomenclature for these valve types. Furthermore, in this mode of operation the second flow control valve 36 is configured so that its ports P21 and P22 are fluidly connected, as is achieved by the positioning of its L-shaped valve element, shown centrally in the valve symbol.

At this point it will be noted that the fluid connections within the fluid circuit 26 are made via conduits/pipes and ports suitable for allowing the working fluid to flow with minimal pressure losses. The system shown in Figure 2 has necessarily been simplified for the sake of clarity and the run of pipes may take a different form to that shown. Likewise, although two flow control valves are shown here, the skilled person would appreciate that further valves, such as pressure relieve valves, shut off valves, tapping points and diverter valves may be provided as an option to provide additional functionality as may be required to the core functionality shown in Figure 2.

The configuration of the first flow control valve 34, the second flow control valve 36 and their respective ports will now be appreciated more fully by reference to Figures 3 and 4.

Referring to Figure 3, it should be noted that the cooling system 30 is in a bypass mode of operation in which the coolant flows around the secondary loop 29, as indicated by arrows F2. The secondary loop 29 functions when the coolant has a low temperature and so does not require active cooling by the second heat exchanger 24.

The secondary loop 29 is active by the state of the second flow control valve 26. As can be seen by comparing the position of the second flow control valve 36 in Figure 3 with that of Figure 2, the L-shaped valve element has changed position so that it now fluidly connects ports P21 and P24.

As such, coolant flows from the pump 30 through the first pipe 50 to the inlet 22a of the first heat exchanger 22, and out of the outlet 22b through a second pipe 52 through the junction 62 to the bypass pipe 60. Coolant then flows through the second flow control valve 36 whereupon coolant then flows from the second control valve 36 through pipe 58 to the first flow control valve 34 and back to the pump 30. It will be noted that the position of the first control valve 34 is the same as it is in the cooling mode of operation, as shown in Figure 2.

It is envisaged that the state of the second flow control valve 34 may be computer- controlled and adaptive to one or more parameters of the wind turbine. One way in which suitable control may be achieved is for the controller 40 to control the state of the second flow control valve 36 based on the temperature of the coolant, as detected by the temperature sensor 38. The controller 40 may implement a suitable temperature threshold or set point which sets the transition point between the cooling mode of operation and the bypass mode of operation. Such a temperature threshold may be set during installation of the wind turbine, for example. The controller 40 may be responsive to other parameters. For example, the outside air temperature and/or nacelle temperature and/or time of operation of the wind turbine or pump 30, and/or power output of the wind turbine, may provide suitable parameters for determining the appropriate mode of operation for the cooling system 20. In either of these situations, the controller 40 is configured to output appropriate control commands 44 to a suitable motorised driver/actuator in order to achieve the required internal reconfiguration of the flow elements in side the valve, for example the rotation of a ball valve element with appropriate porting.

Although sensing the coolant temperature may provide a direct way of determining the coolant temperature, it is envisaged that the coolant temperature may also be modelled by way of a suitable modelling process. For example, it would be possible to determine the coolant temperature within a reasonable certainty level by factoring in one or more of the pump operational speed, time of operation, nacelle temperature and outside air temperature.

The controller 40 may also control the state of the first flow control valve 34. However, a change of state is not required between cooling mode and bypass mode since the first flow control valve 34 remains in the same state during both modes of operation.

The discussion will now turn to Figure 4 which shows a charging/filli ng mode of operation. Comparing Figure 4 with Figures 2 and 3, it will be noted that the cooling system 20 now includes a filler tank 61. The filler tank 61 provides a large capacity coolant receptacle which can be used to fill the cooling system 20 with coolant during installation, ready for use. Or, the filler tank 61 can be used to provide a top up to the cooling system during operation, which may be required periodically in the event of minor coolant leaks.

The filler tank 61 has an inlet 61a and an outlet 61b. In this case, the filler tank 61 is unpressurised and the inlet 61a is simply an open aperture at the top of the filler tank 61. The outlet 61b is at the bottom of the filler tank 61 and is gravity fed.

It will be noted that the filler tank 61 is connected into the cooling system 20 by the first and second flow control valves 34,36. More specifically, the filler tank inlet 61a communicates via a return pipe 62 to the third port P23 of the second flow control valve 36, and the filler tank outlet 61b is connected to the third port P13 of the first flow control valve 34 by filler pipe 64.

It will also be noted that the state of the first flow control valve 34 has been changed so that ports P12, P13 and P14 are fluidly connected to one another, by virtue of the position of the T-shaped valve element therein, whilst port P11 is cut off. This means that coolant is unable to flow from the expansion tank 32 into the cooling circuit 26 via the first flow control valve 34. However, coolant is able to flow solely under the influence of gravity from the filler tank 61 through the filling pipe 64. Notably, there is no pump necessary to feed coolant into the coolant circuit 26 from the filler tank 61.

Note that the state of the first flow control valve 34 may be changed by manual means. For example, the charging mode of operation is envisaged to be responsive to a maintenance event, in which case maintenance personnel would be on hand to change the state of the first flow control valve 34 manually by way of a suitable valve lever, wheel or other actuator. However, the first flow control valve 34 may also be computerised and driven by a suitable motor under the control of control commands 44 issued by the controller 40 in response to the triggering of a system charging event.

It will also be observed that the state of the second flow control valve 36 has been changed compared to the modes shown in Figure 2 and 3 such that now the second and third ports, P22 and P23 are fluidly connected. This can be achieved by suitable operation of the controller 40 issuing output commands 44 to an appropriate motorised driver for the second flow control valve 36 as discussed above. However, as an alternative the position change can be achieved by way of a manual operation or ‘override’ of the second flow control valve 36 in a similar way as for the first flow control valve 34.

As a result of this, during the charging mode of operation, the cooling system 20 is configured so that coolant flows substantially around the primary loop 28 of the control circuit 26, as indicated by the arrows F1. As such, coolant flows from the pump 30 through a first pipe 50 to the inlet 22a of the first heat exchanger 22, and out of the outlet 22b of the first heat exchanger 22 through a second pipe 52 to the inlet 24a of the second heat exchanger 24. From the second heat exchanger, 24, coolant flows from its outlet 24b through a third pipe 56 to the second flow control valve 36 whereupon coolant then flows through ports P22 and P23 to return pipe 62 to the top of the filler tank 62, as indicated by arrows F3. From the perspective of when the cooling system 20 is empty of coolant, the pump 30 is able to operate to push coolant into the system thereby filling the capacity of the network of pipes/conduits. This ensures that the inflow of coolant pushes air out of the pipes and back to the filler tank to ensure that no air bubbles are left in the system.

Further measures can be taken during a filling operation to ensure that the pipe 58 between port P12 of first flow control valve 34 and port P21 of second flow control valve 36 is filled with coolant. For example, a short feed passage e.g. in the form of a pipe or a direct drilling in a valve body can be formed between port P22 or port P23 and pipe 58, and/or a passage can be formed between port P13 or P14 and port P21.

Beneficially, the three modes of operation discussed above can be achieved with only two four-way valves and a single pump. Typically, existing schemes use a combination of two-way valves, three-way valves and an auxiliary filling pump to achieve the same functionality. Compared to existing schemes, therefore, the examples of the invention have the effect of reducing the number of valve components used and also the number of pumps, which results in a less complex system that is lighter and less costly, which are important considerations in the design of such systems and the realisation of a reduction in system complexity is not straightforward to achieve for a skilled person.

What is more, the use of the system pump 30 to move the coolant around the cooling circuit 26 during the cooling mode and bypass mode, but also in the charging mode of operation, means that the functionality can be achieved with one pump instead of two. Moreover, the main system pump 30 is a high capacity pump which means that the filling mode of operation can be carried out more rapidly compared with using a smaller capacity pump that typically would be used for pumping coolant from a filling tank into a conventional cooling system.

It will be noted that in the context of the cooling system described above, the invention embraces the use of the cooling system to fill the cooling circuit 26 with coolant at installation or to top it up during use. Thus, that method may include a maintenance worker, during a maintenance event, connecting the filler tank 61 to a fourth port P13 of the first flow control valve 34, and connecting the return pipe 62 to the fourth port P23 of the second flow control valve 36 and arranging a discharge end of the return pipe to discharge into the filler tank 61. Once the filler tank is connected, the maintenance worker may then configure the first flow control valve 34 to connect the filler tank 61 to the coolant circuit 26, either by manual or computerised means, and then configure the second flow control valve 36 to connect the return pipe 62 to the cooling circuit 26. Finally, the maintenance worker may operate the pump 30 to fill the coolant circuit 26 with coolant from the filler tank 61.

The approach discussed above also may be used to adapt an existing cooling system equipped with flow control valves which are three-way valves, for example a three-way T- port ball valve and a three-way L-port ball valve. In such a configuration, a method of adapting such a cooling system may include, forming in the first flow control valve 34 a fourth port P13 in addition to the first, second, and third ports P11 ,P12,P14 thereof, and forming in the second flow control valve 36 a fourth port P23 in addition to the first, second and third ports P21 ,P22,P24 thereof. Thereafter, it is straightforward to connect a filler tank to the newly formed fourth ports of the respective first and second flow control valves, for the purposes of charging the cooling system whether for initial installation or a system coolant top up. In this connection, the action of ‘forming’ a port in a flow control valve may include the action of drilling or boring an additional port/hole/aperture/window through the wall of the valve body of the flow control valve. Thereafter suitable adaptation may be made for connection to a pipe, such as a screw thread, and/or a machined mating face, and/or clamping means to clamp a pipe to the port so that fluid can flow.

Various modifications may be made to the specific embodiments that have been discussed above with reference to the accompanying figures. Some variants have already been discussed but others would be apparent to the skilled person. Therefore, the scope of the invention should be determined from the appended claims rather than with reference to the specific examples discussed in this text.

Claims

1. A wind turbine cooling system (20) comprising: a coolant circuit (26) adapted to convey coolant between a first heat exchanger (22) arranged to heat coolant flowing through the coolant circuit and a second heat exchanger arranged (24) to cool coolant flowing through the coolant circuit (26); a coolant pump (30) adapted to pump coolant around the coolant circuit; a first flow control valve (34) having first and second ports (P12.P14), wherein coolant flows between the first and second ports (P12.P14) along the coolant circuit in a cooling mode of operation, the first flow control valve (34) further having a third port (P11) to which is connected an expansion tank (32), and a fourth port (P13) adapted for connection to a coolant filler tank (61); a second flow control valve (36) having first and second ports (P22.P21), wherein coolant flows through the first and second ports during the cooling mode of operation, the second flow control valve (36) further having a third port (P24), wherein coolant flows between the second and third ports (P21 ,P24) during a bypass mode of operation in which coolant bypasses the second heat exchanger (24), and a fourth port (P23) adapted for connection to the coolant filler tank (61).

2. The system of Claim 1 , wherein the second heat exchanger (24) is a radiator adapted to be arranged on an external surface of a nacelle of the wind turbine.

3. The system of Claims 1 or 2, wherein the bypass mode of operation, the second flow control valve (36) directs coolant along a branch pipe (60) of the coolant circuit so coolant does not flow through the second heat exchanger (24).

4. The system of Claim 3, wherein the branch pipe connects (60) to the coolant circuit at a point upstream from the second heat exchanger.

5. The system of any one of the preceding claims, wherein the first flow control valve (34) is a four-way T-port ball valve.

6. The system of any one of the preceding claims, wherein the second flow control valve (36) is a four-way L-port ball valve.

7. The system of any one of the preceding claims, wherein the second flow control valve is controlled by a computerised controller (40).

8. The system of Claim 7, wherein the computerised controller (40) is adapted to control the position of the second flow control valve (36) at least partly based on a determined coolant temperature.

9. The system of any one of the preceding claims, wherein the second flow control valve is a proportional valve.

10. The system of any one of the preceding claims, further comprising a filler tank (61) connected between the fourth port (P13) of the first flow control valve (34) and the fourth port (P23) of the second flow control valve (36), wherein in a charging mode of operation, the first flow control valve (34) and the second flow control valve (36) are adapted so that coolant flows from the filler tank (61) to the coolant circuit (26) through the fourth port (P13) of the first flow control valve (34), and so coolant and/or air flows from the coolant circuit (26) to the filler tank (61) through the fourth port (P23) of the second flow control valve (36).

11 . The system of Claim 10, wherein coolant from the filler tank (61 ) flows to the coolant circuit (26) under the influence of gravity.

12. The system of Claims 10 or 11 , wherein the coolant pump of the coolant circuit operates in the charging mode to charge the coolant circuit with coolant from the filler tank.

13. The system of any one of the preceding claims, wherein the coolant circuit has a capacity of greater than 300L, optionally greater than 500L and optionally greater than 800L.

14. The system of any one of the preceding claims, wherein the coolant pump has a flow rate that is greater than 200L/min, optionally greater than 400L/min, and optionally greater than 600L/min.

15. The system of any one of the preceding claims, wherein the first heat exchanger (22) is thermally coupled to a heat generating component (46) of the wind turbine, said heat generating component being selected from at least one of: a generator; a gearbox; a power converter; an oil cooler; an electronics cabinet; a hydraulic pump; a yaw drive.

16. A method of charging a cooling system (20) with coolant, the cooling system comprising: a coolant circuit (26) adapted to convey coolant between a first heat exchanger (22) arranged to heat coolant flowing through the coolant circuit and a second heat exchanger arranged (24) to cool coolant flowing through the coolant circuit (26); a coolant pump (30) adapted to pump coolant around the coolant circuit; a first flow control valve (34) having first and second ports (P12.P14), wherein coolant flows between the first and second ports (P12.P14) along the coolant circuit in a cooling mode of operation, the first flow control valve (34) further having a third port (P11) to which is connected an expansion tank (32), a second flow control valve (36) having first and second ports (P22.P21), wherein coolant flows through the first and second ports during the cooling mode of operation, the second flow control valve (36) further having a third port (P24), wherein coolant flows between the second and third ports (P21 ,P24) during a bypass mode of operation in which coolant bypasses the second heat exchanger (24), wherein the method comprises: connecting a filler tank (61) to a fourth port (P13) of the first flow control valve (34); connecting a return pipe (62) to the fourth port (P23) of the second flow control valve (36) and arranging a discharge end of the return pipe to discharge into the filler tank (61); configuring the first flow control valve (34) to connect the filler tank (61) to the coolant circuit (26); configuring the second flow control valve (36) to connect the return pipe (62) to the cooling circuit (26); operating the pump (30) to fill the coolant circuit (26) with coolant from the filler tank (61).

17. A method of adapting a cooling system (20), the cooling system comprising: a coolant circuit (26) adapted to convey coolant between a first heat exchanger (22) arranged to heat coolant flowing through the coolant circuit and a second heat exchanger arranged (24) to cool coolant flowing through the coolant circuit (26); a coolant pump (30) adapted to pump coolant around the coolant circuit; a first flow control valve (34) having first and second ports (P12.P14), wherein coolant flows between the first and second ports (P12.P14) along the coolant circuit in a cooling mode of operation, the first flow control valve (34) further having a third port (P11) to which is connected an expansion tank (32), a second flow control valve (36) having first and second ports (P22.P21), wherein coolant flows through the first and second ports during the cooling mode of operation, the second flow control valve (36) further having a third port (P24), wherein coolant flows between the second and third ports (P21 ,P24) during a bypass mode of operation in which coolant bypasses the second heat exchanger (24), wherein the method comprises: forming in the first flow control valve (34) a fourth port (P13) in addition to the first, second, and third ports (P11 ,P12,P14) thereof, forming in the second flow control valve (36) a fourth port (P23) in addition to the first, second and third ports (P21 ,P22,P24) thereof.

18. The method of Claims 16 or 17, wherein the wherein the first flow control valve (34) is a four-way T-port ball valve, and wherein the second flow control valve (36) is a fourway L-port ball valve.

19. The method of Claim 17, further comprising: connecting a filler tank (61) to the fourth port (P13) of the first flow control valve (34); connecting a return pipe (62) to the fourth port (P23) of the second flow control valve (36) and arranging a discharge end of the return pipe to discharge into the filler tank (61); configuring the first flow control valve (34) to connect the filler tank (61) to the coolant circuit (26); configuring the second flow control valve (36) to connect the return pipe (62) to the cooling circuit (26).