There are a large number of various objections that can apply to persuade local planning authorities to reject planning permission for wind farms.
The physical space available on land is not an issue, however, the physical space minus the restrictions puts a more practical limit on the availability of sites.
The three factors above provide the unrestricted rules for identification of potential wind farm sites. From this list of sites, hard and soft restrictions are then considered.
Offshore wind farm sites are subject to similar physical restrictions but are less restricted by the socio-political factors that strongly influence onshore developments. Offshore developments are currently restricted by water depth and the associated technical limitations. The higher cost of offshore development compared to that of onshore, and the fact that there are sufficient sites available onshore, means that developers have not considered any offshore sites around the Scottish coast. England however, has initiated an intensive development of their offshore resource based in part on the scarcity of onshore sites.
New planning policy guidance (England) has been put forward to force local planning authorities to look at the wider long term environmental considerations as well as immediate impacts. It is often the case that once planning permission for a potential site has been rejected, subsequent requests for permission on the same site are more readily rejected. One of the main shortfalls of the old policy was that the planning authorities often rejected planning applications based on their assumptions about technical feasibility. In particular, their assumptions that a site with a low wind speed profile is not suitable, this does not take in to account future technological advances that could make the site feasible.
Authorities should be aware that the planning process as it is, unfairly biases against future planning applications, by making assumptions that apply at present, which may not be true in the near future.
Geographical Information System (GIS) tool
The GIS tool is essentially a digital map upon which multiple layers (themes) are laid. The themes represent specific data such as wind speed, relief, land use, transmission grid etc. Common grid co-ordinates link the individual layers. The grid co-ordinates act as 'bins' that the corresponding data can be placed in.
This tool is extremely useful for wind farm site selection. All the relevant data for discriminating a site is available visually and numerically. A potential site can for example be visually identified by a good wind speed characteristic and a close proximity to grid connection.
The latest advancement of this tool uses a GIS database of relevant information for site discrimination, along with parallel software, which determines the electrical implications for the local grid. The user can click on a specific site that they deem suitable, the software then determines the best route for connection to the grid, offering a number of alternatives. The electrical software then determines the electrical implications at each connection point, returning the user with information on grid upgrade requirements for the site and its connection.