How to prevent Wind Turbine Icing? – The WIPS Technology
Wicetec Ice Prevention System (WIPS) prevents ice formation on wind turbine blades, which means continuous energy production and lower maintenance costs for wind power plants.
The main benefits of WIPS are the following:
- It allows continuous turbine operation – no stoppages for heating cycles.
- It is designed to withstand severe icing and gives you a real “winter ride-through”.
- It functions as anti-icing: it detects ice quickly and prevents ice formation altogether.
Fields of application
New installations – WIPS components installed in wind turbine and blade factories:
WIPS technology has been fitted to numerous different wind turbine models. Integration to a wind turbine is possible due to modular design and flexible interfaces. Electrical and control cabinets are designed and made very compact without deteriorating functionality and reliability. The carbon fabric blade heating element production steps can be integrated into typical blade production process and line relatively easily. The heating element materials and production method are similar to normal blade production.
Retrofits for existing wind turbines
WIPS can be fitted to wind turbines which have already been installed. The system is the same as for new wind turbines. Only logistics differ from new installations. The retrofit installations are carried out as following: the original blades are taken down, moved indoors for heating element installation and lifted back up again after installation. The heating elements are installed indoors for two main reasons: it enables high quality lamination process in controlled conditions, and it minimizes weather risk for project schedule on windy site.
Recommended for sites with AEP losses > 3%.
Main parts of Wicetec Ice Prevention System are:
- Blade heating elements
- Temperature sensors in blades
- Blade cabinets in each blade root, creating lightning protection boundary
- Main control cabinet, being the “brains” of the system and an interface towards the wind turbine and outside world
Ice detection is taken care of by commercial ice detector(s) and a combination of weather and operational signals. Wicetec’s Farm Control and Service Support Center enables higher level control and O&M support.
Patented heating element technology
WIPS blade heating elements are the result of extensive research, development and testing: high tech electrical heaters. Heaters are made of carbon fabric, which gives several benefits over other heater types.
Carbon fabric conducts electricity just perfectly: the surface of the blades can be heated enough to prevent the ice build up. It is important to have quick heating response after ice detection to keep the blade free from ice. However, it is also important not to heat the blade too much to avoid degradation of blade material properties. The glass transition temperature of matrix material must be avoided.
Blade heating elements protects from icing the area critical to energy production. Heating of complete blade is not reasonable nor efficient.
Example from real life: Clean blade with WIPS heating elements, operating in Quebec, Canada.
The magic is beneath the surface. Infrared thermography testing from factory acceptance tests.
Material testing in laboratory is necessary for successful selection of materials and production methods.
Suitable mechanical properties: Carbon fabric heating elements tolerate the huge fatigue loading, which occurs when they are installed to flexible wind turbine blades. Heater material has been tested in laboratory with mechanical static and fatigue tests, highly accelerated lifetime test (HALT) and interlaminar shear strength (ILSS) testing. But most importantly, WIPS heaters have been tested in field, in actual wind turbines. Oldest heating elements based on this carbon fabric heating technology, an early version though, are still in operation after 20 years of “rotation”.
No effect on aerodynamics: Carbon fabric heater is so thin that it does not affect the aerodynamics of the blades at all. The added layers (heating element and its glass fabric protection layer) are only 0.5 mm thick. The surface is finished with normal smoothing and blade painting to achieve aerodynamic surface where added heaters are not visible. The magic is beneath the surface!
Lightning protection: Lightning protection of WIPS is coordinated together with the blade and wind turbine lightning protection. Successful incorporation of WIPS lightning protection requires that the wind turbine lightning protection is according to IEC 61400-24 standard. Lightning protection of carbon fabric heater in blade is based on two aspects. First of all, probability of direct lightning strikes to heating element must be minimized. This is done by locating the heating element correctly and avoiding the very tip of the blade. Another aspect is to handle conducted currents in case lighting strikes the heating system. When handling conducted currents, robust and reliable surge protection devices and clear lightning protection boundaries are essential. Several lightning tests have been passed where WIPS heating elements have been integrated into different blades.
Ice detection and control system: WIPS ice detection aims for quick start of blade heating. Therefore, using accurate sensor to detect icing condition is found to be a good solution. WIPS control and electrical system is modular and can be installed into different type of wind turbines. All control panels go through detailed testing before delivery to avoid expensive and time-consuming troubleshooting at the site.