Summary description of project context and objectives:

By their nature, wind turbines are placed in exposed positions and snow and ice is always a threat in colder climates. The build-up of ice on a turbine blade will affect its performance and may lead to damage and even catastrophic failure. Ideally, the accumulation of ice should be stopped at the moment of creation. To overcome this problem, the DeICE-UT system will operate in two modes; anti-icing and de-icing.

Existing passive solutions to the ice build-up problem include; special coatings applied to the surface of the wind turbine blade to reduce the adhesive properties of the ice, painting the turbine blade black to enhance solar heating and applying chemicals to the surface to lower the freezing point of water. None of these is entirely satisfactory. Coatings are not totally effective in hindering ice formation, the solar heating effect only works in bright sunny conditions and chemical applications are problematic at height and are pollutants.

The most common active solution is to creat a thin film of water under the ice with thin-foil electrical resistors embedded in the blade. This process can consume 12% of the turbine’s nominal power output. Another active solution is to circulate hot-air within the blade, but GRP blade material is a thermal insulator and to melt the ice may consume as much as 15% of turbine output. Pulse Electro-thermal De-Icing is another active solution that claims to use less power by sending pulses of current through the heating elements, but there are no commercially available systems. Finally the Electro Expulsive Separation System de-icing device passes currents through wires glued on to the surface of a blade causing them to interact electromagnetically, creating slight movements that shake off the ice. The manufacturers claim very low power consumption, but the system has only been tested on the leading edges of small aircraft blades.

Active Pitching is a solution that doesn’t need an external device or supply. It relies on rotating the blades through their centreline axis to a point when the leading edge of the blade faces the airflow beyond a certain angle, causing turbulent flow and forces that shake off the ice. Of course there is a risk of damage to the blade.

The DeICE-UT project aims to overcome the limitations relating to the Anti-icing / De-icing of wind turbine blades by integrating two technologies which use low cost components that require relatively low energy and have the potential to achieve both anti-icing and de-icing at temperatures down to -20°C. The two technologies are Low Frequency Vibration and Guided Wave Ultrasonics.

The DeICE-UT project seeks to build on previous research and the initial investigations of the SME consortium. The project has 9 partners from 6 EU member states, including five SMEs. The SMEs include high technology organisations manufacturing composite parts (Floteks), high power ultrasonic transducers (Smart Materials) and electronic amplifiers and instruments (BS-Rotor and DTK). In addition, Tureb, as a large enterprise that provides customer support to the world's infrastructure markets in the fields of power generation will act as the initial route to market. The project is supported by three Research organisations; Brunel University (UK), which is providing expertise in numerical modelling, West Pomeranian Technical University (Poland), which is providing expertise in hardware for arduous conditions and TWI (UK), which will be developing the techniques and acting as project coordinator.

The DeICE-UT system concept is illustrated in Figure 1. The two techniques are activated from two sets of transducers placed inside the turbine blade. One set is placed centrally along the blade at distances calculated to give maximum vibration. Another set is in the form of an array that propagates guided ultrasonic waves around the leading edge of the blade. The technical objectives are to optimise two these techniques to prevent ice formation and remove ice.

Description of work performed and main results:

The project is at the 9-month stage of a two-year programme. The work performed so far has been carried out within four work packages.

WP-1 End-user requirements and hardware specifications.

In this work package, a functional specification for the prototype system based on a survey of end-user requirements has been drawn up, from which specific technical specifications for system components are written as the techniques are developed. A sample section of wind turbine has been acquired and a venue for the final system trials has been agreed at one of MIRA’s vehicle environmental testing chambers.

WP 2 Theoretical study and modelling.

This work package has been divided into three tasks. In the first, guided wave propagation around the skin of the turbine blade has been investigated and the optimum conditions for breaking the adhesion between the accreted ice and the substrate. The Interface Stress Concentration Coefficient (ISCC) parameter for a range of ice thickness accumulations has identified for guided wave modes in the so-called dispersion curves that plot their phase velocity against frequency. In the second task low frequency vibrations that excite resonance modes in the turbine blade have been investigated. The displacement, acceleration and stress responses of the blade to a range of resonating modes were used to identify optimum shaker frequencies and placements along the blade. In the final task the effect of these resonating modes on the fatigue life of the blade was investigated, to ensure they did not cause a problem. All shaker arrays were found to generate stresses well within the tolerable loading cycles that literature have proposed for composite wind turbine blades. 

WP 3 Ultrasonic transducer and vibration shaker

Only the ultrasonic transducers have been investigated during this first reporting period. The original work programme had proposed the use of Commercially available off-the-shelf high powered (HP) transducers incorporating acoustic wedges to propagate guided waves. These HP transducers are used in ultrasound cleaners and plastic welders and an inexpensive source was identified and transducers acquired for the GUW technique and low temperature pulser-receiver (WP4) development. For the technique development the use of wedges to propagate specific wave modes was investigated both experimentally and with numerical models and the relationship between wedge angle and phase velocity established. The data from the experiments and from the models were then used to construct dispersion curves to match those used in WP2. The wedge angle and transducer frequency could then be selected to generate the specified ISCC. However it was found that the HP transducers mounted on wedges could only propagate guided waves with out-of-plane displacement (longitudinal), whereas WP2 identified guided waves with in-plane displacement (shear) as the most effective at breaking the ice adhesion.

The work programme has therefore been revised to use arrays of shear transducers. These are not available commercially.

WP-4: Low temperature pulser-receiver and shaker

A low temperature pulser-receiver for the commercially available HP transducers has been developed during this reporting period. A limit of -20°C has been set to avoid having to use very expensive electronic components in the prototype. HP transducers rely a resonance to maximise their output and a novel way of controlling this according to the transducer’s loading has been developed. The pulser-receiver is having to be modified to operate with arrays of shear transducers.

WP7 Results Dissemination and Exploitation activities

As part of this work, a project website has been created and a draft plan for use and dissemination of knowledge has been written. 


Expected final results and potential impacts:

Wind energy is the most popular renewable energy technology both globally and within the EU due to the availability of wind resources and the relative simplicity of the technology. Wind energy currently provides approximately 6% of the overall European electricity production and its expansion into cold climates is inevitable. Here icing on any exposed part of the turbine can occur in the form of wet snow, freezing rain or drizzle, or in-cloud icing. Icing decreases performance of the turbine and therefore the successful solution to the problem proposed by the DeICE-UT system will have a significant strategic impact. The successful implementation of the key deliverables of the DeICE-UT project will enable the SMEs involved to exhibit sustainable growth which will be in line with the growth expected for the wind energy industry overall. Furthermore, the project will contribute towards the improvement of the wind power generation competitiveness in comparison to fossil fuels and other competing energy production methods.

The final cost of installation of the DeICE-UT technology into (3-5MW) wind turbines can only be approximated at this time and in addition will be dependent on a number of factors such as turbine size. More accurate costing of the technology will be undertaken within the project. However, based on our initial design, we estimate the cost of an installed DeICE-UT system to be €40k per installation. From the additional wind turbines planned in Europe, only a 6% market penetration by 2020 should yield revenue of Euro 86M giving the SMEs a return of 45:1 on their investment.

At a societal level, DeICE-UT will increase the number of available jobs in the EU wind energy industry in line with economic growth, reduce the need for dangerous maintenance work in cold climates by inspection personnel, further promote the involvement of female employees in a male-dominated industry, contribute to sustainable industrial growth within Europe, increase public confidence in renewable energy sources across Europe, enable wind farms to be located in areas with optimum conditions, away from populated areas and optimise the production of European wind farms in Icing regions - year round production.

A road-map has been developed for taking the DeICE-UT system beyond the prototype stage, which will include thorough market research, a business plan for attracting new finance and a projected work plan to raise the system’s technology readiness level. 





De ICE UT concept diagram