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Case study:
Modelling site suitability for wind farms

Manual

1. Introduction
2. Context
3. GIS Data Management
4. GIS Modelling and Analysis
5. Results & Outcomes

Appendix 1
Appendix 2

2. Context

2.1 Wind Power: A Bright Potential for Renewable Energy

Wind Power remains one of the few bright spots in 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 (see Fig. 2 below). Many of the criteria necessary for the development of wind energy are met in the UK and it is only a combination of conservatism, investment and conservation considerations, which prevent it's extended development.

Fig 2 - European Wind Speeds

Wind power is typically generated by a number of large wind turbines. These range from 50 to 100 metres high and are generally gathered together in numbers to create a 'wind farm'. The siting of a wind farm is a significant initial step in the process of developing wind energy and it is this part of the process that will be the real focus of the case study. Some comment will be made on the context and environmental issues surrounding wind farm development but the advantage from a GIS point of view is it presents a very coherent setting for a decision-making cases study, which has a fundamentally 'geographical' context.

The object of this study is to apply selective parts of the initial phase of the British Wind Energy Association planning process for developers, to a target area in the South East region of the United Kingdom. The planning 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.

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 and ozone depleting 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.

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." (Brocklehurst 1999). These wind farms can stretch for several kilometres across the countryside, but provide locally produced electricity for large local communities.

There is currently a power 'shortage' in the South-East of England and with a concentration of wind farm development in the South West of the United Kingdom (most viable, high wind speeds). There is increasing pressure on developers to find ways of economically developing the lower wind speed sites. This pressure translates into the developers widening the scope of their search for potential sites, with the South East as a target region required to provide 6% of the total onshore wind resource. The development process requires the combination of technology and the landscape through a broad initial study eventually focusing onto a 'shortlist of sites'.

The aim of the study can be to fix a maximum generation capacity and search for a suitable site that fulfils these criteria. Within the GIS Case Study this will provide the opportunity to examine two separate routes to identify suitable sites. Essentially the Case Study will be carried out in two phases. Phase I will expect the student to take an INITIAL CRITERIA (IC) approach and then re-work the process using a MODIFIED CRITERIA (MC) approach. These processes will be explained in more detail below. Phase II will then carry out further modelling on the selected sites by applying additional technical and environmental specification to help identify optimal site location(s).

2.2 GIS Issues, Sources & Materials

The Case Study will employ a rich mix of resources and materials. These will include GIS software, digital maps, wind speed modelling programmes and technical documentation associated with wind farms. The aim is to make sure that GIS Students will use a variety of skills to build up the required files in ArcView to do the modelling. The base data will be derived from Digimap and the ETSU NOABL Wind Speed Programme. The materials will be put together in a structured way and the sequence of development is outlined in the subsequent chapters. The first phase is to identify key criteria associated with Wind Farm location modelling. These criteria will be standard but there is no guarantee that they will produce matched outcomes in different areas of the South-East.

The second and third phases are key elements of all GIS projects, namely data identification & collection and data collation to get the collected data into a form usable within the GIS. These are major elements of the case study and the time required to complete these should not be underestimated. The data identification phase will involved students using their knowledge of the UK National Grid to download the appropriate digital map tiles from Digimap as well as using the same knowledge to identify matching data from the wind speed model. The precise digital map base and layers to be downloaded and converted (through MapManager) will be made clear in the section on criteria. Once downloaded the data must be matched and converted through natural geo-processing.

At this stage all of the different layers required will be ready to be saved in a project in the GIS. The modelling stage will involve further transformation which will test student skills in key GIS analytical tasks such as querying, buffering, interpolation, surface modelling, boolean operations and scenario modelling. Provided the base layers have been correctly put together then a number of options can be tested based on the technical specification of wind farm modelling to produce a series of scenarios. This may optionally involve a number of other GIS operations such as cookie-cutting, viewshed modelling, scripting and vector data analysis. These will produce outcomes based on local demographic data to give the project an economic and social dimension to add to the technical specifications. It is not expected that there will be a single answer or single site identified. Part of the value of the exercise is to teach students that a GIS is best placed to produce a series of optional outcomes, which can then be explored further outside of the system to come up with appropriate locational decisions. The power of GIS and indeed geography is that we can model a vast number of locational decisions in a simple and fast system that greatly speeds up the process and allows the decision-maker to experiment with different options without slowing them down too much.

Last updated: December 4, 2003