CASE STUDY

Crystal Rig Wind Farm

Project Particulars:

Project Value: £7.0M

Programme: 2003-2004

Client: Fred Olsen Renewables

Project Description

This project comprises of 20 large wind turbines, each capable of producing 2.5MW of power with an overall height of 100m. Birse Process was awarded the EPC contract to design and build all the civil engineering, building and electrical works on the project. The German company, Nordex, then erected their turbines on completed foundations and connected into the electrical system. In order to deliver the large, heavy turbine components a number of detailed modifications were needed to the public highway and a new 6km access track was constructed along the remote hillside to Crystal Rig site. A new 33kV substation was built at the grid connection point near Dunbar and a larger control building was built on site. Birse Process installed an 11km HV underground cable connection over the hills between the two buildings. Large reinforced concrete turbine and anemometer foundations were constructed using a concrete batching plant on site.

Our Involvement

Birse Process Engineering won this contract against a very competitive field of contractors. With the help of Birse Technical Services the submitted bid was of very high quality and demonstrated how we proposed to overcome the considerable civil engineering challenges of constructing massive turbines in a high, remote environment. Duncan Noble led the engineering team on behalf of Birse Technical designing much of the tender and contract stage works without using external provision, and was responsible for schedule and cost management of the design works.

Birse Technical Services were responsible for the design of all the civils permanent works on the project. The extensive site tracks and highway modifications required a detailed knowledge of how the massive components for the turbines were to be transported and erected. This was a challenge which had to be done in an environmentally sensitive location high in the Scottish Borders. Each blade is 40m long and transported as a single load from Germany, that’s approximately 3 times longer than a standard UK trailer.

The turbine foundation design was carried out by a specialist consultant on behalf of Technical Services. Together we endeavoured to find the most efficient possible foundation solution. Even a small volume of reinforced concrete designed out of each base can multiply into considerable savings over the whole wind farm, concrete works carried out on a Scottish mountain are not cheap! We carried out a significant value engineering exercise on all aspects of the base, in particular the holding down bolt arrangement and overall concrete volume, to provide a very efficient and effective design. Each turbine base has an individual drainage system, which links into the network of drainage channels on site, designed to control buoyancy effects on the gravity bases.

The cranes used to erect the turbines were among the largest crawler cranes available in Europe. We designed the yard areas to accommodate the bearing pressures from these giant cranes, using site won stone.

We also designed the control building on-site and the substation off-site at the grid connection point, some 11km from the site. These buildings need to withstand very harsh weather conditions and house sensitive control equipment.

By working closely and cooperatively with many specialist advisors we were able to provide Birse Process and the Client with a high degree of support on site. The wind farm is now fully operational and the Client regularly exports the full 50MW capacity to the national grid.