What are the design assumptions for the project?

The planning application will utilise a ‘micro-siting approach’, which means we assume the maximum design parameters with the highest impacts of all options available. There are two design options which can be accommodated at the site: a three turbine design with turbines up to 185m and a four turbine design with turbines up to 150m (How tall is a wind turbine?).  The micro-site approach instead assumes four turbines up to 185m tall – again, the maximum design limitations rather than a realistic design.

All of the turbines will be located within Earystane plantation itself. Earystane plantation has a total size of 178 acres but the windfarm ‘site’ consists of the turbine bases only with construction roads serving the turbines following existing tracks within the plantation. None of the Scard area is being developed for onshore wind, though some biodiversity improvement works could be undertaken on this portion of land, if required.

The specific design (including specific foundation types) will only be confirmed once a manufacturer and construction contractor are appointed. All design assumptions to date therefore assume the most restrictive limitations for the planning application.  Several types of foundation exist for wind turbines: not all require large concrete bases. Indeed these, are more usually associated with thick sediment where there is no stable geological foundation beneath the turbine base. However, Earystane plantation overlies thick, solid metamorphic rock which could accommodate rock anchors as an alternative solution.

There has been no confirmation of which type of foundations will be used for the development and it will not be possible to confirm which type will be used without the appointment of a manufacturer. It is the manufacturer who will specify which foundations are best suited for their design given the site geology. The micro-site design assumes the highest impact and highest cost foundations.

The cost assumptions for the project are also based on the micro-site design and represent the total project cost from inception to completion including: feasibility assessments, Environmental Impact Assessment, planning application preparation, consultation events, manufacturing, site preparation (inclusive of drainage and flood defences, cost of land purchase where required, site access tracks, project resourcing including construction, electrical infrastructure and connection to the 33kV transmission network), transport costs from manufacturing facility to the Isle of Man (Port of Douglas) and transport costs from the Port of Douglas to Earystane, installation of turbines at the site, commissioning and all mitigation actions. A contingency factor has also been included within costs. 

Information on what happens to the turbines at the end of the projects life is available on the following FAQ - How will equipment be disposed of at its end of life?

A Quantity Surveyor has been appointed to provide accurate cost estimates as far as possible for the designs proposed which are also broken down to individual project elements.  All estimated costs are based around the outer parameter assumptions for the micro-design i.e. 4 turbine bases and associated foundations, and 4 of the most expensive, largest turbine models. The costs quoted to date (i.e. c. £40M) are an accurate reflection of the current worst-case design assumptions.

The generation costs quoted in pence per kWh (<5p/kWH) have been derived from this pessimistic cost figure. More information is available in the following FAQ - How much will the windfarm cost? The figure represents a reduction in overall electricity costs relative to current gas prices.

Information on how the windfarm will be funded and the differences between Manx Utilities and Isle of Man Government in terms of funding is available on the following FAQ -How will the windfarm be funded?