Wednesday, 28 September 2016
11:30 - 13:00 Turbines operating in low temperatures
Turbine technology  
          

Cold climate sites are characterised by the occurence of icing events and/or periods with temperatures below the  operational limits of standard wind turbines. This session will address specific challenges faced during the operation of wind farms in cold climates. Topics include low-temperature compliance testing of wind turbines, methods for detection and analysis of icing events, as well as the  operational performance of de- and anti-icing systems.

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Learning objectives

• Learn about the importance of the increasing market share of cold climate wind turbines and the effect of such environment on wind turbine components;
• Gain insights in the behaviour of certain critical components in (extreme) low temperatures, its cold start-up performance and potential failure modes which have to be taken into account during design;
• Get an overview about icing basics and ice detection systems for wind turbines;
• Learn about tools used for modelling the thermal behaviour of a blade and respective de- and anti-icing system;
• Understand the uncertainties related to them, the methodology for their validation and the application.

 

Additional speakers to be confirmed.

Co-chair(s):

René Cattin Meteotest, Switzerland
Co-authors:
René Cattin (1) ^F
(1) Meteotest, Bern, Switzerland (2) VGB Powertech, Essen, Germany

Evaluation of ice detection systems for wind turbines

Introduction

Atmospheric icing has a significant impact on the development and the operation of wind parks. To reach an optimal performance, the turbine must first be able to detect ice on the rotor blades immediately when it occurs. Second, it must provide a signal which states that the rotor blade is free of ice and thus normal operation can be resumed.

Approach

The goal of the study was to provide an independent overview on ice detection systems commercially available. The study consists of basics and important definitions regarding icing on structures. The main part is a detailed description of the ice detection systems based on information provided by the system manufacturers as well as publicly available documentation. Afterwards, the different systems are compared in an evaluation matrix. Additionally, short overviews on ice protection systems for wind turbines and on the state of the art regarding icing forecasts are given.

Main body of abstract

There are two different types of ice detection systems being evaluated and compared in the study:

- Nacelle based systems: ice detection with instruments installed at one point on the nacelle of a wind turbine.
- Rotor blade based systems: ice detection with devices installed on the rotor blade.

All nacelle based systems measure instrumental icing and therefore do not represent the effective conditions on the rotor blade. For a safe and efficient operation of wind turbines under icing conditions, measuring rotor icing is mandatory.

10 nacelle based systems and methods have been evaluated. The Labkotec LID-3300IP and the Goodrich 0871LH1 model have the highest technical maturity and the highest number of systems in use. Furthermore, they are the only certified systems. Several independent field studies exist for most systems. These studies show that all systems have their shortcomings under specific conditions.

5 blade based systems and methods have been evaluated. The power curve method is applied very frequently. The Bosch Rexroth BladeControl system has the highest number of systems in use. The other systems have significantly smaller numbers of systems in use. This is explained by the fact, that the fos4IceDetection, Wölfel IDD.Blade and eologix are very new systems. All blade based systems are certified. No independent field studies exist for the blade based systems.

The power curve method is the only blade based system which is not able to detect rotor icing during stand still of the wind turbine. All systems except the eologix system require a minimum wind speed of 2 m/s or higher to be able to detect rotor icing. The eologix system is the only system one which does not require access to real-time operational data of the wind turbine (pitch angle, rotational speed, wind speed). At the same time, eologix is the only blade based system which measures icing at specific spots on the rotor blade. The other systems are able to detect ice anywhere on the blade with increasing sensitivity towards the blade tip. The power curve method as well as the fos4IceDetection and the eologix system do not require any electrical wires in the blade. All blade based systems can be retrofitted.


Conclusion

For te fist time, a comprehensive overview on all ice detections systems existing on the market has been provided. For a safe and efficient operation of wind turbines under icing conditions, measuring rotor icing is mandatory. Today, four promising systems exist on the market which are able to measure rotor icing. However, there are currently no results of an independent field study available, thus field experience is missing.


Learning objectives
- Icing basics
- All about ice detetion systems for wind turbines