Horns Rev Newsletter
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December 2001
Read about:
- New turbine in Tjæreborg
- Life cycle assessment of the Vestas V80 turbine
- Status: Driving of foundation piles for Eltra's substation
- Grouting of turbine foundation and transition piece
| New
turbine in Tjæreborg
On December 5, 2001 Elsam erected a Horns Rev prototype turbine on the foundation of the old Tjæreborg turbine. The turbine is similar to the ones to be erected at Horns Rev in the North Sea in the summer of 2002. The turbine in Tjæreborg is state-of-the-art turbine technology. It provides the opportunity for service technicians and other service and maintenance staff to practice the service, maintenance and operating routines of an offshore turbine before Elsam starts erecting the World's largest offshore windfarm with 80 turbines next summer. In many ways, the offshore prototype differs from a standard onshore turbine. The changes are made because repair and maintenance are much more difficult and costly for an offshore turbine than an onshore turbine. This includes:
A number of other changes are made to ensure that the windfarm meets the demands defined for turbines connected to the national grid:
This means that in principle the windfarm operates as a traditional power station if an error or special operating conditions in the grid require so. New rules demand that offshore turbines be equipped with lights to warn air and marine traffic. The marking lights will be tested on the Tjæreborg turbine and will, after testing, be dismantled. Turbine data:
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| Life
cycle assessment of the Vestas V80 turbine
For 24 months Tech-wise have worked closely with Vestas to make a life cycle assessment (LCA) of turbines. This is also referred to as a cradle to grave analysis and it includes a description of the total environmental impact of a product, a process or service in its entire lifetime. An LCA covers all resources necessary for production, operation and for decommissioning and scrapping of a product. In phase 1 which ended in September 2001 an initial LCA was made for a V80 offshore turbine; i.e. the same type as for the Horns Rev windfarm. This was financed by PSO funds and was concentrated solely on the turbine and the foundation and did not include grid connection. The results of this phase-1 LCA show that the environmental impacts of wind turbines primarily derive from materials used for the production of the turbines. It is therefore of utmost importance that the materials are recycled when scrapping the turbine. In May 2002 another LCA will be made in co-operation with Vestas. This LCA will look at both an offshore and an onshore windfarm and this LCA will include the grid connection aspects. This LCA is partly financed by the Danish Energy Agency via ERP (energy research programme). The Horns Rev offshore windfarm will be part of this LCA. References: Livscyklusvurdering
af vindmøller, PSO 1999 Life cycle
assessment for wind turbines
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Status: Driving of
foundation piles for Eltra's substation
There is no news to report since the November Newsletter. Click
here to read the November news. The contractors are expecting to continue in January 2002.
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| Grouting
of turbine foundation and transition piece
A transition piece will be installed between the turbine foundation and turbine tower enabling adjustment ofany misalignment occurred during driving of the foundation pile. The transition piece will be installed after the pile has been driven 22-24 meters into the seabed. The transition piece will be grouted to the pile. The technique is often used in the offshore business where for instance oilrig jackets are grouted to the seabed with steel piles, which are then grouted to the rig's legs. The methods for calculating the grouts are based on the experience made in the offshore business and are therefore concentrated on describing how the axial loads are absorbed. The most important load impact on the foundation is however the thrust moment originating from the wind's load on the turbine rotor. Since these calculation methods are not suitable for dealing with the moments in question, Tech-wise took steps to make tests of the grouting to supplement the calculations. In the spring and summer of 2001, three tests were made in co-operation with the Densit A/S, the producer of the grout material and the University of Aalborg. The tests included extreme load testing (50-year wind/wave) and exhaust load testing. The tests showed that the chosen design is of sufficient strength and durability. The width of the full-scale joint is 70 mm and the grouting height is 6 meters. To close the joint in the bottom a rubber grout packer is used to hold the grout together while hardening. In the agreement with the main contractor, MT Hoejgaard, it is demanded that the grouting method be tested. MT Hoejgaard took this opportunity to test their proposed grout packer as well. The main contractor has also tested the grout packer in full scale (4-meter diameter) to test whether there was a risk of a scale factor when using a smaller diameter (curvature) of the grout packer. There wasn't. The grout packer passed the test.
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| Issued newsletters |
Elsam A/S
Overgade 45
DK-7000 Fredericia
Phone: +45 76222000
Fax: +45 76221962
www.elsam.com