Abstract
(Englisch)
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According to a study of wind-energy potential in Switzerland made in 1996, 3.5% of the present electricity consumption can be met using wind power. A large proportion of the high-potential areas lie in cold regions heavily affected by rime and ice. The Weco project (wind energy production in cold climate) is a research Project carried out within the framework of the EU's joule III program. The main aim of this project is the research into and the reduction of climatic influences on wind power production in those cold climates where a high energy production potential is available.
In Switzerland, attention was focussed onto the following questions:
- collection of data on the climatic situation at locations suitable for wind power applications;
- quantification of production losses caused by rime and icing-up;
- exchange of data and integration of results in the Weco project;
- utilisation of the results by plant operators and instrumentation manufacturers.
Main results
Icing-up map (wp 1)
Based on an analysis of information provided by 20 Swiss meteorological institute (SMA) weather stations, the following conclusions can be made:
- at locations lying between an altitude of 1,000 and 1,500 meters in the Jura and pre-alpine areas, icing-up conditions must be expected on 30 to 60 days per year.
- at locations in the Alps at an altitude of around 2,000 meters icing-up conditions must be expected on 10 to 30 days per year.
Energy production, field measurements and observations (wp 2 and wp 4)
In spite of the relatively mild winter 1997/98 with correspondingly little icing-up, detailed analysis of comprehensive measurements and observations madeAt the 'Grenchenberg' (150 kw-bonus) and 'Titlis' (30Kw-HSW) sites, along with information from further locations, allow the following conclusions to be made:
The production capacity of wind power plant is substantially reduced by icing-up for the following reasons:
- Modification of the rotor blades' aerodynamic profile
- Iced-up anemometers deliver erroneous data, which can result in the plant -- not starting even if wind conditions are good.
- Low delivered power (for a particular wind speed) is interpreted by the plant control system as an error thus causing the plant to be shut down.
Observations show that compact ice layers are rarely formed - ice is usually deposited loosely as hoarfrost. The risk of injury or damage being caused by ice thrown off is therefore very low.
Measurement equipment (wp 3)
At the 'Grenchenberg' and 'Titlis' locations, anemometers with heating elements were set up alongside those instruments without heating. Contacts were made to swiss manufacturers of wind-measurement equipment and ice detectors. Here are some of the findings:
- The deployment of both heated and non-heated anemometers allows the detection of ice formation to a more or less reliable degree of certainty.
- Under very severe conditions (Titlis) even anemometers with shaft or cup heating be covered with ice or snow, which - in extreme cases - can lead to the loss of individual cups.
- Ice detectors available on the Swiss market today are relatively expensive as far as their use in site-evaluation is concerned, but are well suited for use as part of anti-icing and de-icing systems for wind farms.
- The Swiss meteorological institute is developing a hot-wire anemometer which could have good sales opportunities in the wind energy business.
- The EU has estimated the following annual sales figures for the period up to 2010:
- ice-free anemometers 16 million fr. /a
- ice detectors 1.1 million fr. /a
Project meetings and seminars (wp 6)
The project was reviewed and further developed on the following occasions:
- 6 project-team meetings
- 4 meetings within the framework of the eu-project
- 2 visits by the EU co-ordinator in Switzerland
- presentation of the Weco results during two professional conferences in Switzerland
- organisation of a workshop for climatologists and plant operators.
Recommendations
The following recommendations can be made as a result of the experience gained during the Weco project:
Evaluation of sites
- the periods when icing-up can possibly occur can be approximately estimated using the icing-up maps.
- visual observations on climatic conditions should be made and registered in written form during the whole site evaluation period.
- at least one of the anemometers used should have a shaft or cup heating system.
- for larger projects, the use of ice detectors can be worthwhile.
- temperatures should also be registered.
- expert opinion on climatological factors as well as wind factors should be obtained.
Wind power plant
- if icing-up conditions often prevail, the deployment of wind power plant with anti-icing systems (e.g. rotor-blade heating etc.) Should be considered. Several manufacturers already offer such equipment.
- instrumentation used to control the wind plant must be fitted with heating elements
- anti-icing systems are particularly recommended for wind power plant in highly frequented areas such as ski resorts
Planning guidelines for wind energy plant in Switzerland
The most important results obtained during the Weco-project have been included in guidelines1 which will be published in spring 1999.
The guidelines address the following parties:
- government: national, cantonal, regional and community authorities involved with specific projects and general planning activities.
- site developers: investors, landowners, owners of facilities who are directly involved in the realisation of wind power plant and wind parks.
- engineers, planners: professionals who carry out site-evaluation, cost/benefit calculations, ecological compatibility checks etc. On behalf of site developers.
Promotion of wind-power site evaluation by the Swiss federal office of Energy
The results obtained during the Weco project clearly show that the recording of periods when icing-up can occur is absolutely necessary when evaluating sites for wind energy plant. This leads to the conclusion that, when clarifying questions concerning projects supported by the p+d wind program, climatological factors must also be taken into account.
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