Siting wind turbines

This learning object investigates how Digital Elevation Models can be used to identify potential sites for wind farms.

Context – planning future energy sources

The Kyoto Agreement has led to a need in many countries to reduce their reliance on fossil fuels for electricity generation and to increase their renewable energy capacity. Wind Power remains one of the more widely adopted sources of renewable energy in the 21st Century. Several European countries, in particular Denmark, produce a high percentage of their energy from wind power. Current share of energy production in Denmark is around 15% with a not unrealistic aim of producing 50% of Denmark’s energy need from wind farms by 2030.

Although the wind energy proportion of energy produced in the United Kingdom is only 0.4%, the country has one of the highest average wind speeds in Europe and has as a result, a vast potential for the development of wind energy as a renewable energy source. The importance of increasing the number of wind farms in the United Kingdom is displayed in the current government’s response to the Kyoto Summit on the Environment. To reduce environmentally damaging emissions, the power generating companies are required to produce 10% of the total power capacity by 2010 from non-fossil fuel renewable resources. There is the requirement that 26% of this will come from onshore wind generation and as a result there is considerable pressure to identify appropriate sites for such developments.

Wind power is typically generated by a number of large wind turbines. The typical Wind Energy turbine has a tower ranging from 50 to 100 metres high, with a set of two or three rotating blades attached to a hub containing a gearbox and turbine generator connected to the national power grid. It is necessary to group wind turbines together so that they are financially and practically viable and to minimise their environmental impact. These wind farms can stretch for several kilometres across the countryside, but provide locally produced electricity for large local communities. The siting of a wind farm is a significant initial step in the process of developing wind energy.

In the UK, the British Wind Energy Association has developed planning guidelines for identifying potential wind farm sites. These guidelines are an advice tool to assist the developer and local council to foster appropriate and commendable wind energy development. They are voluntary, with no enforcement except when the developer presents a proposal to the local planning committee or the Secretary of State for the Environment and a public enquiry is instigated on behalf of the local population.

Using DEMs to site wind turbines

As part of these guidelines, elevation has a significant role to play in identifying appropriate sites for wind turbines:

·         Visual impact: One of the main difficulties in siting a wind turbine is the potential opposition of local residents. Of particular concern is the visual impact of wind turbines on the landscape, both for tourists and residents. DEMs can be used to assess this visual impact as part of the planning process.

·         Assessing local wind climate: The electricity-generating potential of a given site is related to the cube of the wind speeds at that site. For a prospective site to be viable financially, it is therefore critically important that the local wind climate is assessed accurately. Terrain is known to affect wind speeds. Sites at higher altitudes are typically windier and ridges and plains often experience higher wind speeds than sheltered valley bottoms. The relationship between wind climate and terrain is, however, complicated. As a result, a specialist software package known as WASP (see references) has been developed to assess local wind micro-climates. The WASP software includes some of the functions of a GIS, makes use of digital elevation data, and can be used for evaluating wind farm sites. Rather than using this specialist and detailed tool here, however, we will use standard GIS software to assess potential wind farm sites.