Rotary kinetic fluid motors or pumps – With means for controlling casing or flow guiding means in... – Natural fluid current force responsive
Reexamination Certificate
2002-04-26
2003-02-18
Look, Edward K. (Department: 3745)
Rotary kinetic fluid motors or pumps
With means for controlling casing or flow guiding means in...
Natural fluid current force responsive
C415S004500, C415S175000, C415S177000, C415S908000
Reexamination Certificate
active
06520737
ABSTRACT:
The present invention relates to an offshore wind turbine wherein the power transmission placed in the nacelle is cooled by means of a liquid, such as seawater, oil, or glycerol/water, that is conducted to the nacelle from the tower on which the nacelle is pivotally arranged around a vertical yawing axis. The liquid transfers the excessive heat from the power transmission system to the seawater near the turbine which is used as a heat sink of low temperature and enormous heat capacity as compared to traditional air cooling. The liquid is conducted in an open or in a closed circuit and the cooling system may comprise more than one cooling circuit.
The flow of cooling-liquid is in a particular embodiment of the invention conducted between the tower and the nacelle through a heat transfer unit having a first part that is stationary with respect to the tower and a second part that is stationary with respect to the nacelle. The parts have at least one passageway for a liquid flow defined between substantially abutting surfaces of the parts, preferably an annular passageway.
BACKGROUND OF THE INVENTION
It is known to provide cooling for the power transmission system in the nacelle of a wind turbine by means of an air intake arranged on the upwind side of the nacelle and directing the flow of air from the intake around the parts of the power transmission system. Alternatively, one or more parts of the power transmission system may have a liquid cooling system comprising a heat exchanger that is cooled by the flow of air from the air intake.
Such a cooling system has certain disadvantages. The air intake may be blocked by birds or by ice formed from rainwater, and the air intake may for that reason be provided with means for preventing such blockage, such as a fan for providing a cleaning counter flow of air or heating means for melting ice. It is furthermore becoming increasingly difficult to provide sufficient cooling capacity as the power output of the new generations of wind turbines increases. Insufficient cooling may cause mechanical breakdown of parts of the power transmission system and lowers the efficiency coefficient of the parts.
A more efficient cooling system may on the other hand provide for some of the parts of the power transmission system to be constructed more compact, in particular the electronic parts. The loss in the power transmission system is typically of the order of 6-10% of the power output of the wind turbine, the loss in the gearbox and in the generator being of approximately the same magnitude. in particular the generator may advantageously be cooled more efficiently in order to prevent break-down of the generator and both the rotor and the stator of the generator may be cooled. Furthermore, the power control system and the electrical transformer, e.g. comprising a frequency converter, may also constitute a part of the power transmission system and may also be cooled to obtain better efficiency.
U.S. Pat. No. 5,436,508 discloses a wind turbine used in an energy production and storing system in which the wind rotor drives an electric generator and a heat pump which is used to produce heat that may be stored and used for later production of electricity in periods of slacks winds. Excessive electricity production may also be converted into heat and be stored. Liquid is circulated between the tower and the nacelle, which may turn relatively to the tower, to transfer heat from the heat pump to the storage in the ground. This liquid is not used directly to cool the power transmission but a blower forces a cooling air stream past the electrical generator and to the heat pump. According to the present invention, a cooling liquid is transferred to the nacelle from the tower for the purpose of cooling the power transmission system, i.e. the gear box and/or the electrical generator and/or the power control system and electrical transformer so as to obtain a decreased power loss in the transmission system and other advantages as mentioned above.
DESCRIPTION OF THE INVENTION
It is an object of the present invention to provide an offshore wind turbine having an efficient cooling system for the power transmission system located in the nacelle of the wind turbine by means of using seawater as a heat sink for the cooling system. In particular, it is an object of the present invention to provide a cooling system that during periods of warm weather may provide a higher temperature difference between the cooling agent for cooling the power transmission system and the system itself than the temperature difference provided by the air.
An efficient cooling system for the power transmission system can be provided by cooling at least a part of the power transmission system with a cooling liquid that is conducted from the tower and to the nacelle. It is however a problem to have means for conducting the cooling liquid from the tower and to the nacelle for the reason that the nacelle must be able to pivot relatively to the tower, so-called yawing, in order to situate the main shaft parallel to the direction of the wind from which shaft the blades of the wind turbine extend perpendicularly to the main shaft.
Thus, it is a further object of the present invention to provide a device for forming one or more passage ways for liquid between the nacelle and the tower during at least most yawing positions of the nacelle.
Thus, the present invention relates to an off-shore wind turbine comprising
a stationary part including a tower extending substantially vertically,
a nacelle comprising a wind rotor having at least one blade arranged on a main shaft having a substantially horizontal rotation axis, and a power transmission system,
a yawing system comprising a stationary part being fixed to an upper end of the tower and a movable part being fixed to the nacelle, the stationary part and the movable part being designed so that the nacelle is being supported vertically and horizontally by the tower and may pivot relatively to the tower about a substantially vertical yawing axis, and
a cooling system for transferring excessive heat from the power transmission system to seawater surrounding the wind turbine, the cooling system comprising first conduction means for conducting a flow of cooling liquid from the stationary part of the wind turbine and to the nacelle during normal operational conditions and at most positions of the nacelle relative to the tower, pumping means for pumping the flow of cooling liquid through the first conducting means and first heat exchanging means for transferring heat from the power transmission system to the cooling liquid. The stationary part of the wind turbine includes further a support for supporting the tower, normally being a foundation on the seabed. However, the stationary part may be positioned on a floating support that is connected to anchoring blocks on the ground or seabed with wires, so that the stationary part may move primarily up and down relatively to the ground.
The wind rotor has at least one blade but it is preferred that it has two or three blades. Naturally, a wind turbine with a rotor having even more blade can also be made according to the present invention. The blades are mounted on a main shaft extending along a rotation axis that is substantially horizontal by which is understood that the axis may be tilted as much as about 10 degrees to horizontal so that the end of the main shaft carrying the rotor is elevated with respect to the other end.
The power transmission system is the system transmitting the power induced by the wind on the blades to a power output from the wind turbine. The power transmission system may comprise various parts depending on the requirement to the individual wind turbine, the parts being an electrical generator and/or a gear box and/or bearings for the main shaft and may further include a frequency converter for controlling the frequency of the power delivered to a power supply system so that the rotational speed of the generator optionally may be variable, it may include a transformer and/or an AC/DC converter
Fischer Torsten
Vilsbøll Niels
NEG Micon A/S
Nguyen Ninh
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