Peter Whitbread-Abrutat and Nick Coppin, Wardell Armstrong International
April 13, 2012 | 0 Comments
How can the potential negative legacy of a mine site be converted into a positive inheritance for the wider environment and local communities? Recent imaginative renewable energy projects give good grounds for confidence that many former mine sites can be ideal locations for developing alternative energy generation facilities, simply by looking in a new light at some of the qualities that made them problematic in the first place.
Possibilities range from wind, solar photovoltaics (PV), geothermal, hydropower and energy crops to test-beds for a variety of more experimental power generation technologies.
As with any development, mine site conversion to renewable energy generation must of course take due account of impacts on the local environment and communities. But when done well, these can provide ongoing and long term value in the form of an alternative income stream well after mining operations have ceased. Specific benefits can include the mitigation of cleanup costs, reusing infrastructure to reduce decommissioning cost, enabling re-employment of a skilled mining workforce and/or new local employment opportunities, and a clean and usually quiet after-use for a mine site that can also create a potential source of carbon credits with tradable value.
So why might mine sites prove to be ideal locations for the generation of renewable energy?
First, and maybe most obviously, mine sites often cover extensive areas of up to thousands of hectares or more where wind and solar power structures will have less environmental impact and are therefore less likely to meet with opposition. Mine sites often already have the necessary electricity transmission lines and transport infrastructure in place, avoiding extra capital costs. Land transaction costs are generally lower and the process can be simpler because brownfield areas tend to be owned by fewer landowners than a similar area of greenfield. Brownfield redevelopment for green energy can also reduce development pressure on greenfield sites, maintaining their carbon sink benefits. Furthermore, other forms of redevelopment may not be an option due to the remoteness of the site, or the environmental conditions may rule out residential or commercial use without significant extra development cost.
Large-scale wind energy projects are an increasingly common alternative energy use on former mine sites, particularly in Europe and the US. Just one example is the largest wind farm planned in Virginia. With 166 turbines sited on over 4000 hectares of land disturbed by coal and hard rock mining activities, 99% of the land remains usable for other activities including farming. In Scotland, Black Law Wind Farm near Forth covers 1850 hectares of abandoned coal mine land, grazing land and commercial forestry, with 42 wind turbines generating 97 MW, and plans for expansion potentially increasing the total generating capacity to 193 MW.
The visual impact of wind turbines may be less controversial in areas already affected by mining landscapes. Mineral waste dumps often give increased elevation and exposure to enable increased output, while underlying land can also still be used for other purposes. However, there may be technical challenges to overcome due to the nature and stability of the dump material and constructing adequate foundations for turbines.
At the Hazlehead Wind Farm site in West Yorkshire, wind power is now being generated on the site of a former clay quarry spoil tip and landfill site, with three turbines and a proposed installed capacity of 6 MW. A community benefits fund will run alongside the wind farm when it is fully operational, providing support for local community groups, environmental and voluntary projects to help ensure a long-term positive impact on the area. Engineering and environmental consultancy Wardell Armstrong carried out an initial feasibility study, detailed site investigation, geotechnical testing and slope stability work. The results were used to determine the practicality of siting the turbine foundations within the tipped material mudstone material, as well as creating a suitable landform.
In 2009 a study of former coal mining land across the UK was undertaken to examine its potential for wind power generation. This was based on identifying suitable sites of sufficient area, far enough from existing habitation, with an annual average wind speed >6.5m/sec, reasonable access, free of other constraints and the potential to link to the grid. 106 sites were identified, with the potential for nearly 4 GW of generating capacity, some 10 TWh/year. If developed, this would displace the output of a typical coal-fired power station. However, there would be significant UK permitting hurdles to overcome. Also, the ground conditions on most of the sites, being man-made ground, means that engineering costs for foundations would be higher than for greenfield sites, which would affect the economics.
Former mine sites can be ideal locations for solar energy generation, thanks to their often expansive and exposed positions, especially in areas with an aspect facing the sun. Germany is utilising its old mine sites in this way. The Geosol solar plant at Espenhain, Leipzig, constructed on a former lignite mine ash site, generates 5 MW and saves around 3700 tonnes of CO2 every year. The site of the former Göttelborn coal mine in Saarland, southwest Germany, has been converted into a solar energy park - the largest of its type when opened. It generates 8 MW from 50,000 photovoltaic panels covering 165,000 m2.
Other countries are following suit, with the UK’s first large-scale solar PV farm developed by Lightsource Renewable Energy now live on the south-facing site of the former Wheal Jane tin mine near Truro in Cornwall. The solar farm houses 5680 panels with a peak generating capacity of 1437 MWh. To bring this project to fruition, a detailed landscape management plan was created. There was also pre-consultation; screening and scoping; feasibility studies including specific studies on glint, glare and ecology; a full environmental impact assessment; planning submission and post-submission consultation. There are now plans for further development to create the UK’s first earth science park using energy from solar, wind, hydro, and shallow and deep geothermal sources, as well as an 18,288 m2 business park.
Since the ambient temperature of the Earth increases with depth, underground mine workings provide a convenient collection point for groundwater. This resource may be sufficiently warm to raise the starting temperature of the water used for heating and hot water in buildings and horticulture, often involving ground-source or water-source heat pumps. Mine and quarry sites can also offer opportunities for access to deep geothermal resources, involving hotter water or even superheated steam power generation via a turbine.
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