Patent Application
20090200114
This application is related to application Ser. No. 12/021,482, titled “Lubrication Heating System And Wind Turbine Incorporating Same”, to Bagepalli et al. and filed on Jan. 28, 2008.
This invention relates generally to rotary machines and more particularly, to a thermal management system for operating wind turbines in cold weather environments.
Generally, a wind turbine includes a rotor having multiple blades. The blades are attached to a rotatable hub, and the blades and hub are often called the rotor. The rotor transforms mechanical wind energy into a mechanical rotational torque that drives one or more generators. The generators are generally, but not always, rotationally coupled to the rotor through a gearbox. The gearbox steps up the inherently low rotational speed of the turbine rotor for the generator to efficiently convert the rotational mechanical energy to electrical energy, which is fed into a utility grid. Gearless direct drive wind turbine generators also exist. The rotor, generator, gearbox and other components are typically mounted within a housing, or nacelle, that is positioned on top of a base that may be a truss or tubular tower.
The gearboxes need to be lubricated to function effectively. Typically, oils are used for lubrication, and the oil assists in the extraction of heat generated in a gearbox. The oil heats up during operation of the gearbox, and a heat exchanger can be used to cool the oil. A suction pipe typically exits the gearbox and feeds into a circulating pump. The circulating pump is used to force the oil through the heat exchanger, and the cooled oil is then directed back to the gearbox. Typically, gearboxes contain a sump in which the oil resides. Dry sump gearboxes utilize an external oil tank instead of an internal one (e.g., wet sump). Dry sump machines can offer better efficiencies (due to reduced churning losses in the oil) and their light weight.
In extremely cold environments (e.g., less than about −10 degrees C.), the lubrication oil used in the gearbox can become very viscous or thick. This cold and viscous oil resists flow and the circulating pump can be damaged if run when the oil is very cold. In some known solutions an external heater and pump are connected to the oil sump of the gearbox. This oil sump heater takes a long time to heat up all the oil in the gearbox sump and requires a large amount of energy. The result is a long delay during cold weather operation, waiting for the oil to come up to a minimum temperature, until the wind turbine can begin producing power, as well as lower overall efficiency due to the large power drain imposed by the oil sump pump/heater.
Accordingly, a need exists in the art for a system that will quickly heat or cool the oil entering a circulating pump used with a gearbox, and that does not require a large amount of power or time to operate.
In one aspect of the present invention a wind turbine is provided comprising a gearbox containing a lubrication medium and a pump for circulating the lubrication medium. A gearbox lubrication suction pipe is used for transporting the lubrication medium from the gearbox to the pump. At least one pump outlet pipe can be used for transporting the lubrication medium from the pump to other components of the wind turbine. A thermal wrap is in thermal connection to, at least a portion of, at least one of, the gearbox, pump, gearbox lubrication suction pipe and pump outlet pipe. The thermal wrap is used to heat or cool, at least a portion of, the lubrication medium.
In another aspect, a wind turbine is provided comprising a gearbox containing a lubrication medium, and having an internal or external oil sump. A pump is used for circulating the lubrication medium, and a gearbox lubrication suction pipe is used for transporting the lubrication medium from the gearbox to the pump. At least one pump outlet pipe can be used for transporting the lubrication medium from the pump to other components of the wind turbine. A thermal wrap can be used for heating or cooling the lubrication medium, and is in thermal connection to, at least one of, the gearbox, pump, gearbox lubrication suction pipe and at least one pump outlet pipe.
In a further aspect, a thermal management system for a lubrication medium used in a gearbox is provided. The system comprises a pump for circulating the lubrication medium, and a suction pipe connected between the gearbox and the pump, for transporting the lubrication medium from the gearbox to the pump. At least one pump outlet pipe can be used for transporting the lubrication medium from the pump. A thermal transfer means can be used for heating or cooling a portion of the lubrication medium. The thermal transfer means is in thermal connection to, at least a portion of, at least one of, the gearbox, pump, suction pipe and pump outlet pipe.
Blades 112 are positioned about rotor hub 110 to facilitate rotating rotor 108 to transfer kinetic energy from the wind into usable mechanical energy, and subsequently, into electrical energy. Blades 112 are mated to hub 110 by coupling a blade root portion 120 to hub 110 at a plurality of load transfer regions 122. Load transfer regions 122 have a hub load transfer region and a blade load transfer region (both not shown in
In the exemplary embodiment, blades 112 have a length between about 50 meters (m) (164 feet (ft)) and about 100 m (328 ft). Alternatively, blades 112 may have any length. As the wind strikes blades 112, rotor 108 is rotated about rotation axis 114. As blades 112 are rotated and subjected to centrifugal forces, blades 112 are subjected to various bending moments and other operational stresses. As such, blades 112 may deflect and/or rotate from a neutral, or non-deflected, position to a deflected position and associated stresses, or loads, may be induced in blades 112. Moreover, a pitch angle of blades 112, i.e., the angle that determines blades 112 perspective with respect to the direction of the wind, may be changed by a pitch adjustment mechanism (not shown in
In some configurations, one or more microcontrollers in a control system (not shown in
Rotor 108 is rotatably coupled to an electric generator 132 positioned within nacelle 106 via rotor shaft 134, sometimes referred to as low speed shaft 134, a gearbox 136, a high speed shaft 138, and a coupling 140. Forward and aft support bearings 152 and 154, respectively, are positioned within and are supported by nacelle 106. Bearings 152 and 154 facilitate radial support and alignment of shaft 134. Rotation of shaft 134 rotatably drives gearbox 136 that subsequently rotatably drives shaft 138. Typically, a lubricating oil is used within gearbox 136. Shaft 138 rotatably drives generator 132 via coupling 140 and shaft 138 rotation facilitates generator 132 production of electrical power. Gearbox 136 and generator 132 are supported by supports 142 and 144, respectively. In the exemplary embodiment, gearbox 136 utilizes a dual path geometry to drive high speed shaft 138. Alternatively, main rotor shaft 134 is coupled directly to generator 132 via coupling 140.
Also positioned in nacelle 106 is a yaw adjustment mechanism 146 that may be used to rotate nacelle 106 and rotor 108 on axis 116 (shown in
A portion of the turbine control system resides within control panel 150. The turbine control system (TCS) controls and monitors various systems and components of wind turbine 100. A plurality of sensors are distributed throughout wind turbine 100 and the status of various conditions (e.g., vibration level, temperature, etc.) are monitored. The sensed conditions are utilized by the TCS to control various subsystems of wind turbine 100. In one example, the ambient temperature or temperature of the oil in the gearbox sump can be sensed and compared to a lower threshold value. If the temperature of either or both of these values is below the threshold, a heater could be activated to warm the gearbox oil to above the threshold value. When a higher predetermined value (e.g., minimum recommended operating temperature of gearbox lubricating oil) is reached the heater may be de-activated.
Gearboxes typically need lubrication to function effectively. This lubrication is often in the form of an oil. When oil is warm, it flows readily and is non-viscous, but when oil is cold it becomes viscous and resists flow. Referring to
In cold weather operation (e.g., less than about −10 degrees C.), the lubricating oil used in the gearbox becomes very viscous. The circulating pumps 310 used in conjunction with gearboxes can be damaged by the viscous oil. For example, the vanes of the pump could break when forced to pump viscous fluids (e.g., lubricating oils). The term “cold” is somewhat relative and refers to a temperature when a lubricating medium becomes viscous. For example, some lubricating oils may become viscous at about +10 degrees C. The present invention can be used at any temperature and/or in any application where a viscous lubricating medium needs to be heated to become less viscous.
In some known solutions to this problem, and as illustrated in
Once the oil in gearbox 136 has warmed to a minimum operating temperature, pump 310 can be energized and transfer oil out of gearbox 136 via suction pipe 340. Pump 310 can include an internal valve (not shown) for selectively discharging oil into gearbox return pipe 350 or into heat exchanger input pipe 360. Typically, when the oil in gearbox heats up enough to require cooling by heat exchanger 320, it is normally returned to gearbox 136 via pipe 370. In alternative embodiments, the oil may pass through pump 310 before returning to gearbox 136.
Given enough time and power the system illustrated in
A thermal wrap 420 can be placed around pipe 410, and this wrap 420 can be used to heat the oil contained within pipe 410. The thermal wrap 420 can be a blanket like device having electrically heated wires or cables, a hot air jacket or heat transfer device. The thermal wrap 420 could also be embedded within the walls of pipe 410 (e.g., electrically powered heating wires within the pipe wall). A portion or the entirety of pipe 410 can be covered with the thermal wrap 420. The thermal wrap 420 can be attached to pipe 410 with any suitable fasteners (e.g., hook and loop, cable ties, magnets, etc.). Power can be supplied via a standard electrical plug (not shown) and the wrap 420 can be configured to run on AC or DC power.
One major advantage to this system is that only a small amount of power is needed to power thermal wrap 420. Another advantage is that since only a small amount of oil is heated (i.e., only the oil contained within pipe 410) the resulting low thermal mass of oil heats up very quickly. The pump 310 is constantly fed a supply of warm oil and can begin operation much faster than in the system shown in
In alternative embodiments the thermal wrap could be configured to cover all or a portion of gearbox 136. In one embodiment, only the lower portion of the gearbox could be heated, and in other embodiments the entire gearbox, or portions of the gearbox could be heated by one or more thermal wraps. It is also contemplated by aspects of the present invention that one or more wraps could be used to cover and heat, all or portions of, the gearbox 136, outlet pipe 410, pump 310, inlet pipe 350 and pipe 360.
As described above in conjunction with
Referring to
In some applications, the pipes or hoses used in a gearbox system are formed of a rubber or elastomeric material, and this rubber material can be damaged by oil that is too hot. It will be understood that the terms “pipe” or “pipes” and “hose” or hoses” are used interchangeably, and the present invention can be applied to any type of pipe or hose used in a machine requiring the lubrication medium to be transported between components. Additional aspects of the present invention can be utilized to monitor the temperature of pipe 410, and if this temperature exceeded or was approaching a maximum recommended temperature (i.e., the oil was making the pipe or hose too hot), then the heated wrap could be deactivated. The temperature control system may also decide to instruct pump 310 to route the oil through heat exchanger 320 to cool the oil. In additional embodiments, the heated wrap itself could contain a self-regulating device that deactivates itself when an over-temperature condition is approaching. The temperature control system 610 could also be controlled by the turbine control system (TCS). In some wind turbines the TCS monitors and controls a variety of subsystems (e.g. pitch motors, yaw drive, power converter, etc.). In additional embodiments, the thermal wrap could be controlled to cool the oil or pipe, if it was determined that an over-temperature condition was occurring or approaching.
In additional aspects of the present invention, the thermal wraps 420, 520 and/or 720 could comprise heating and/or cooling means. For example, the cooling means could be used if the oil in pipe 410 or pump 310 became too hot. In some applications, it may be possible for oil, over a predetermined temperature, to damage the pipe 410 and/or pump 310. Accordingly, a cooling means integrated with wrap 420, 520 or 720 could be used to cool oil that has become too hot. The cooling means could comprise a length of conduit or tubing that contains a heat transfer medium. The conduit could be connected to an external or internal heat exchanger, or to any other suitable cooling or refrigeration device. In one example embodiment, the conduit used for cooling could be connected to heat exchanger 320, or a thermo-electric cooling device could be employed. The thermal wrap, when placed over all or portions of gearbox 136, could also be used to cool all or portions of the gearbox when properly configured. The gearbox cooling embodiments could be used to augment or replace heat exchanger 320.
The thermal wrap 420, 520 or 720 could be used with gearboxes of the dry sump or wet sump type. A dry sump gearbox has its oil tank external to the gearbox, whereas a wet sump gearbox has at least a portion of its oil tank formed integrally or internally within the gearbox. In a dry sump application, the thermal wrap could be used to cover all or portions of the external oil tank.
In one cooling example, a pump or compressor 805 could be used to transfer a refrigerant medium between the wrap 820 and heat exchanger 815. Appropriate pipes or hoses can be arranged between the compressor 805 and the wrap 820, and between compressor 805 and heat exchanger 815 for transporting the refrigerant medium. Any suitable refrigerant medium could be used, including but not limited to, antifreeze, ethylene glycol, glycol mixtures, or any other thermo-dynamic gas or liquid capable of absorbing heat from the desired component to be cooled. The heat exchanger 815 could be located either inside or outside of nacelle 106. The heat exchanger 815 can be used to dissipate heat contained within the refrigerant medium. In some embodiments, heat exchanger 320 (as shown in
The wrap 820 shown in
In one heating example embodiment, the thermal wrap 920 can be used to heat the lubricant contained within oil sump tank 930. The thermal wrap 920 can be connected via conduit, pipes or hoses to a pump or compressor 805. A heat exchanger can be connected to compressor 805 via similar conduit, pipes or hoses. The compressor 805 and heat exchanger 815 can function in a similar manner as described previously in conjunction with
In one cooling example embodiment, thermal wrap 920 could be configured to cool the oil within oil sump tank 930. For cooling applications, the compressor 805 and heat exchanger 815 may be omitted, or they could be retained as dictated by the specific application.
In
In some applications, it may be possible to eliminate the use of large heat exchanger 320, by configuring the thermal wrap to cool the lubricant and/or gearbox 136. Alternatively, a smaller heat exchanger 320 could be used and placed in a greater variety of locations due to its reduced size. It could be possible to locate the heat exchanger 320 in a more thermally advantageous position to increase the dissipation of heat. For example, the heat exchanger could be placed in cooler positions within nacelle 106, or located externally to nacelle 106. Another advantage to using a smaller heat exchanger, is that a smaller pump could also be employed due to the lower flow resistance of the smaller heat exchanger.
The various aspects of the present invention herein described provide a system for quickly and efficiently heating or cooling the lubrication medium (e.g., oil) used in gearboxes. The oil is heated or cooled prior to entering the circulating pump and only a small thermal mass of oil is thermally processed (i.e., compared to the entire volume of oil used for gearbox lubrication). The result is a very quick start up time for machines utilizing gearboxes in cold weather environments. Any engine, vehicle or machine requiring a gearbox could employ the invention herein described. One application is in the use of wind turbines, and the present invention enables a quick start-up time during cold weather operation, while reducing the costs and disadvantages of prior solutions. The systems described herein could be applied to dry sump and/or wet sump type gearboxes.
While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.
