Since falling ice fragments can be a security risk for the environs of the wind turbine, the authorities request measures to reduce the risk from icefall to an acceptable level. Thus, R.ICE is focussing on modelling of resulting ice-fall zones and an estimation of the energy losses from icing. Furthemore, shut downs due to ice can cause considerable economic losses. N.Ice therefore analysis the possibiltiy to avoid icelayers by laser treated materials.
R.Ice – Risk analysis on the impact of wind turbine icing
Project duration: April 2016 to June 2019
The research project R.ICE is focussing on modelling of resulting ice-fall zones and an estimation of the energy losses from icing, site-specific information about the number and intensity of icing events is required. As there is, also in the international context, only little experience on ice formation on rotor blades and on the properties of the falling ice pieces (size distribution, flight trajectories, falling distances), this project focused on the foundations and effects of wind turbine icing, with special consideration of the Austrian conditions. An important part were suitable measures and regulations, to ensure the observation of permissible risk limits in approval procedures of wind energy projects.
The project included of the following work packages:
- Modelling and provision of an icing map in a spatial resolution of 3x3km for the entire of Austria (ice accumulation on a 3cm standard cylinder, acc. to ISO 12494).
- Evaluation of the icing map using long-term wind turbine operating data and provision of a regional icing climatology for wind turbines with including average number, duration and intensity of icing events.
- Monitoring of icing events at wind turbines using an innovative imaging method to generate a data base in terms of number, size, distance and possible flight trajectories of falling ice fragments.
- Determination of ice-fall zones around the wind turbines through modelling of the falling trajectories of the ice fragments.
- Development of scientifically based measures and policies for possible further reduction of the ice fall ice-fall, in collaboration with law experts and technical experts.
N.ICE – Reduction of ice formation by nanostructuring of surfaces with an ultrashort pulse laser
Project duration: April 2019 to March 2022
The aim of the project NICE is to establish nanostructured surfaces for demanding applications such as on rotor blades of wind turbines. Icing of surfaces potentially affects operational safety and functionality in many areas such as: towers, power lines, aircraft wings, or rotor blades of wind turbines. Nano-structured surfaces produced through laser ablation are often hydrophobic and thus can be used to delay or to inhibit ice-formation on a surface.
Nanostructuring of surfaces with lasers is one of the main research topics on the Institute for manufacturing and high energy laser technology at the Vienna University of Technology. By using an ultra-short pulse laser (USPL) strong hydrophobic surfaces can be produced. This can reduce the adherence of ice on a surface, or, in the best case, prevent surface icing altogether. As part of the project NICE, ice formation on surface samples will be observed under defined conditions in a climate wind tunnel. In addition, a multi-physics simulation model for the icing-formation on surfaces will be set up, simplifying the targeted creation of surfaces with desired properties.
In a second part of the project, surface samples are exposed to harsh meteorological conditions in a field test designed and conducted by Energiewerkstatt. This takes place on a site in Styria owned by the Österreichischen Bundesforste, where also a number of wind turbines are operated. The field test includes the exposition of the surfaces on a stationary rig as well as under moving conditions. For the latter, the samples have been attached to the rotor blades of a small wind turbine. The icing behavior and the environmental conditions are continuously monitored by high-resolution cameras and sensors. The analysis of the collected data will show the long-term effects of harsh weather conditions on the nanostructured surfaces and can be used to improve the laser processing.