R&D icing and low temperatures tests in OWI-Lab’s climate chamber

Researchers of the Dutch Delft University of Technology have performed R&D icing and low temperatures tests on a new de-icing technique in OWI-Lab’s climate chamber. These tests will help them to further develop a de-icing technique based on ns-DBD plasma actuators.

As the deployment of wind energy in cold climate regions is growing, engineers are looking into optimisation projects that deal with cold climate compliance and potential icing issues that can occur on the rotor blades in cold climates. Due to good wind conditions at most cold climate sites, an increased air density, low population densities at such locations and new technological solutions that deal with the challenges associated to low temperatures and icing, the cold climate wind power market is gaining momentum.

Cold climate wind farm & example of severe icing on rotor blade

IEA Wind: Task 19 - Wind Power in cold climates, an international expert working group within IEA R&D Wind dealing with wind energy in cold climates since 2002, reported at the Winterwind Conference in 2014 the potential of this relatively new market for wind power. Apart from the market study that indicated a 60 GW installed base of wind power in cold climate back then in 2012, also 50 GW was projected for the near future between 2013 and 2017, which is currently in progress. The report also indicated an increase in the awareness for cold climate challenges and an increasing demand for dedicated cold climate technologies with regard to anti- and de-icing solutions for rotor blades (see publication). 

Cold climate testing

In 2012, OWI-Lab installed a large climatic test chamber, tailored to the demands of the wind power business, to deal with validation and verification testing in extreme climatic environments. The test facility enables companies and universities to deal with experiments and validation test projects in either cold climate, hot climate, tropical climate and offshore environment. Since its opening the facility has supported several OEMs and component suppliers with climate chamber testing of gearboxes, converters, transformers, service cages and other technologies associated to wind turbines.

Cold climate testing, mainly cold start-up performance testing and low temperature design verification testing of large and heavy components have become the lab's speciality. 

6.15 MW wind turbine gearbox tested for cold-start on the left and controlled icing test (3 mm ice layer) at OWI-Lab’s large climate chamber 

Due to the large dimensions (10.6 m x 7 m x 8 m), high cooling power and fast deep cooling possibilities to -60 °C the climate chamber is also useful for performing icing tests. Either anti-icing as well as de-icing prototypes can be validated by using ice-spray guns in the climate chamber, in order to perform experiments in a controlled environment. With regard to this topic, OWI-Lab supported TU Delft in the development of a new electro-thermal de-icing system based on nano-second pulsed DBD plasma actuation that has potential for rotor blade/wing anti-/de-icing. Certain R&D tests were performed in the climate chamber last year, in order to support the ongoing development of a prototype.  

DBD plasma actuators

DBD plasma actuators have been widely investigated in aerodynamic research during the past years for their unique features and their flow control properties. Nanosecond pulsed DBD plasma actuators, were found to drive an ultrafast gas heating mechanism. In literature temperature increases of the gas right above the actuator of several 100 K are reported. In order to find a useful application for this heating mechanism, experiments were performed at the OWI-Lab’s climate chamber to test the possibility of melting ice formed directly on DBD plasma actuators.

Nano-second pulsed dielectric barrier discharge plasma actuators in action

This conducted research could be interesting for the development of future de-icing applications using plasma actuators on aerodynamic surfaces such as wind turbine rotor blades. Different plasma actuator configurations were tested in the climate chamber at a temperature of -20 °C, while using an ice-spray gun to form layers of ice on the plasma actuators. The energy consumed by the plasma actuator during the de-icing process was monitored as well as the heating of the surface, using a thermal camera. The experiments showed that the actuator is able to melt several millimetres of  the ice layer within a few hundreds of milliseconds. With this speed, in combination with low energy consumption, this technique could offer a great advantage with respect to currently existing de-icing techniques. 

The TU Delft researchers: “We did a three-day testing campaign at the OWI-Lab, as this type of controlled testing environment is not available at the Delft University. The conducted tests gave us insights into what aspects to focus on while further developing a de-icing technique based on ns-DBD plasma actuators.”

TU Delft will present its research and insights on this newly developed de-icing technique at the Winterwind conference in Åre (Sweden), which takes place in February 2016.