Anti-icing and de-icing technology
De- and anti-icing systems in the market
Nordex Energy – Anti-icing System
Nordex provides AIS to their developers. AIS operate while the turbine is running and consists of localized heating of the aerodynamically relevant blade surface. The system has reliable and lightweight electrical resistance heaters and optional manual control of heating, which means the system itself is autonomous. If data indicates the presence of conditions liable to cause icing, the heating elements are automatically activated. Energy-efficient heating prevents ice from accumulating on the rotor blades.
In the rotor blades there are heating elements, sensors, electrical connection lines for power and signal transfer and a lightning protection system.
With the anti-icing system in place the wind turbine would not need to be shut down even if ice were to form during operations. The system automatically removes any ice that has accumulated along the front edge of the blade and reduces the risk of potentially dangerous situations caused by falling ice. The advantages with this system are maximum yield even in protracted sub-zero temperatures. The system starts as a result of a number of factors such as ambient humidity, wind and temperatures, especially in the range of -5°C and-10°C (Nordex, 2012). The system has lower internal power consumption and the internal power requirements for the anti-icing system are less than 0,3 per cent and are already factored into the test results (Nordex, 2012). Other advantages of the system are resilient solution integrated into the blade structure and the ability of removing ice during operation does not cause any drop in yield.
The system consists of one ice sensor, and heating elements on parts of the leading edge of each rotor blade.
In manual mode the automatic heating control is deactivated. The following options can be selected for heating control: No heating (the heating control is deactivated), Level 1 (the contractor of the star connection is controlled for the period defined by a paramenter chosen Nordex) and Level 2 (the cntractor level of the delta connection is controlled for the period defined by a parameter chosen by Nordex.
Siemens has electrically heated carbon fiber foil on the turbines. The system consists three elements. It has an ice detection system, the heating of the blades and a system to control the strategy for de-icing. The system includes power connections at the root and heating element integrated into the blade surface at manufacture control system based on existing sensors. It has full retention of the aerodynamic profile and no effect on nose levels. Their first generation of Siemens de-icing system was installed and tested in 2011 at two wind farms in Sweden. Today, more than 50% of the turbines Siemens supplies in Sweden are equipped with de-icing system. Turbine with this system is available with the company’s SWT-2.3-101, SWT-3.0-101, SWT-2.3-113, and SWT-3.0-113 turbines.
Vestas de-icing technology use circulation of hot air to heat the blades and melt the ice. It is similar to Enercon’s system. The system consists of a heating unit in the hub to distribute hot air throughout the blades, and a control unit which is integrated into the turbine’s SCADA system. This system is available for company’s V112-3,3 MW turbine, and have installed a prototype in Sweden.
The system is designed to de-ice the outer 1/3 of the blade full chord, and the outer 2/3 of the leading edge towards the tip end, to maximize power curve recovery. This targeted approach does not compromise de-icing efficiency according to Vestas, but is critical in regaining full power curve quickly. It also reduced the risk of run-back icing, and can minimize the danger of ice throws from the blade tip.
Enercon has a technology that combines an ice detection system with a fan heater installed at the root of the blade. It circulates a stream of hot air right up to the tip of the blade inside the turbine blades to melt ice after it has formed. The ice detection system works on a specially developed power curve analysis method. Rotor speed, wind speed and other operating values data are analyzed during operation and are plotted into an operating map. Ice build-up on the blades alters the aerodynamic properties and this is shown on the operating map. When certain criteria are fulfilled and ice is detected, the turbine is stopped and the de-icing procedure is initiated. The temperature of the blade surface is heated to 0°C, and the ice build-up is melted. The de-icing procedure can take place while the turbine remains in motion, thawing thin layers of ice at an early stage of formation. If ice continues to form, it becomes essential to stop the turbine while the process takes place.
|Nordex||Anti-Icing For Rotor Blades||Electro-Thermal||Heating|
|Enercon||Rotor Blade De-Icing System||Warm-air circulation|
|Vestas||Rotor Blade De-Icing System||Electro-Thermal elements||Heating|
|Donfang's||De-Icing System||Uses hot air in the blades and electrically heated carbon fibre film on the blades.|
|GE Energy||De-icing System||Warm-air circulation|
|WinWind||Blade Ice Prevention System||Electro-Thermal heating elements||Heating|
Table 14 An overview of known anti-and de-icing systems