Wind energy production is fast expanding in remote areas where wind turbines need to work under extreme climatic conditions. Such remote locations very often have profitable wind conditions and are not affected by the ‘not in my backyard syndrome’. On the other hand, the climatic conditions can be very harsh to operate such a remote located wind turbine.
A large amount of such turbines are installed at sites affected by extreme temperatures which in the worst case affect the turbine’s availability if components fail or don’t work efficient due to extreme conditions.
Usually onshore and offshore wind turbines are designed to operate in a temperature range between -10°C to +40°C, but in some cold climate locations like for example Canada, Scandinavian countries, Inner Mongolia, … the ambient air temperature can even drop lower than -40°C. After some days of no wind in these hostile environments also the turbine components can cool down to -30°C or even -40°C. Such events have to be taken into account as extreme temperatures can cause unplanned failures due to low temperature effects on materials (brittle fractures of metals, seals, cables,… ), and insufficient lubrication due to viscous and stiff oils and greases. Because of this effect also pumps can be risk and overheating problems can occur. Also, long cold start-up times can have negative effects on the energy yield and the wind turbines business case.
This illustrates why the wind energy industry needs robust and validated components capable of surviving and operating in these extreme conditions in order to be cost-effective. OEM’s and component suppliers are more and more aware that extreme temperature events and its effects on their machines need to be taken into account. Modeling is certainly contributing to this goal, but also physical testing and validation tests are required in order to substantiate confidence in its designs and to gain insights in the behavior and performance in extreme conditions.
The lack of multifunctional climate chambers to cope with these challenges is known within the wind industry in comparison to available test chambers for the automotive and aerospace industry for example. Wind turbine components are much bigger in dimensions and heavier than cars and therefore cannot be tested in the same climatic test chambers. Also the needed auxiliaries (electrical power, specialized test benches,…) for testing such heavy machinery is different for this industry.
To come to this necessity a dedicated test facility in the Port of Antwerp has been built by OWI-Lab containing a large climatic chamber for wind turbine component testing in a wide range of temperatures. Both mechanical, hydraulic and electrical turbine components up to 150 tonnes can be tested in a temperature range from -60°C to +60°C. In order to cope with the test need of large rotating wind turbine equipment like for example wind turbine gearboxes, OWI-Lab invested in a dedicated no-load test bench suitable for cold start testing.
This unique mobile no-load test bench can cope with maximum weights up to 150 ton and has a break-away torque of 10kNm and will therefore be suitable to test cold start-ups of the next generation of multi-MW drivetrain components. The full test setup can be used for cold start-up tests up to -40°C and hot climate no-load tests up to +60°C. In order to substantiate confidence in its designs, validation tests are necessary to gain insights in the behavior and performance in extreme conditions. ZF Wind Power Antwerp NV, a leading manufacturer of wind gearboxes, is also aware of the benefit to validate its gearboxes in extreme temperature conditions. In order to do so, the company teamed up with OWI-Lab. Controlled laboratory tests were carried out at OWI-Lab on a 2.1MW wind turbine gearbox in order to validate the cold start-up behavior and cold start-up time of the machine in -40°C conditions.
A gearbox can be sensitive to extreme temperatures if their effects are not taken into account. For example during start-up of a wind turbine after idling in cold conditions, the rotating elements in a gearbox can be at risk because of insufficient lubrication and/or differential thermal expansion of its components. Lubricants become highly viscous due to extreme cold which affects the oil flows in the gearbox and other auxiliaries mounted on a wind turbine gearbox system. On the other hand, cooling systems can experience overheating problems during extreme heat in the case of hot climatic conditions. These potential failure modes illustrate the requirement for qualitative engineering of the lubrication mechanism, thermal management system and appropriate control strategy in case of cold start-up events. Validating these systems in a controlled environment has been successfully performed by ZF Wind Power Antwerp NV and OWI-Lab.
[mappress]
Press release, November 19, 2013; Image: OWI-Lab