Bringing life to old mines through clean energy

Mine closures often leave a negative legacy: land and water pollution can remain well after mine rehabilitation; potential land uses after rehabilitation decline due to a loss of biodiversity; and mine dumps along with the remaining infrastructure are often an eye sore. There have been examples globally of the deployment of renewable energy projects at abandoned mines, which indicates a potential for alternative energy generation on these facilities.

What is attractive about abandoned mines is often their proximity to electricity infrastructure such as substations and transmission lines, as well as road and transport infrastructure. The existence of infrastructure can lower renewable energy project costs. Open cast operations often cover extensive land areas and cause land utilisation challenges after mine closure.[i] It can be argued that the environmental impact of deploying renewable energy on old open cast operations will be less pronounced relative to other sites. This of course does not negate the need for the renewable energy feasibility assessment and the related environmental impact assessments. Furthermore, the socio-economic impacts of closing mines are well recognised. Alternative power generation offer opportunities for renewed economic activity in areas where high unemployment is expected due to mine closures.

The growing emphasis on sustainability has led to stricter regulations on the rehabilitation of the environment at decommissioned mines in South Africa. There is growing evidence of creative uses of old mines which could contribute towards mining rehabilitation. As demonstrated in the international examples that follow, renewable energy can play a meaningful role in mining clean-up activities by, addressing the social challenges arising from mine closures and generating income from what could easily be wastelands.

Examples of clean energy technologies that have been developed at old mines include: solar photovoltaics, wind, and hydropower in the form of pumped storage.

Solar Energy

Rehabilitated open cast operations can be ideal locations for the deployment of solar energy due to their expansive and often exposed positioning. A solar power plant was built over a landfill at the German coal mine of Leipzig, in 2004. At the time, the plant was one of the largest in the world at 5 megawatts (MW) of installed capacity which could supply power to 1 800 households.[ii] Active projects in the US include the Chevron Questa Mine in New Mexico with a 1MW concentrated photovoltaic facility constructed on a mining tailings dam. Questa was developed by Chevron as part of the mine clean-up operation. Solar energy has also been successfully used to power mine clean ups in remote areas like the Leviathan Mine in California,[iii] and to run a water treatment plant that removes high metal concentrations from acid mine drainage originating at the Summerville mining site in Colorado.[iv] Active projects in the UK include the Wheal Jane Park project, which is a 1.42 MW capacity solar power plant located at an abandoned tin mine in Cornwall (enough energy to power 430 homes).[v]

Wind

Large scale wind energy projects are increasingly being deployed on former mine sites in the US and Europe. Project examples from the US include the Casselman wind power project in Pennsylvania, with a capacity of 34.5 MW which can power up to 8000 homes. This project supports the local economy through lease payments to landowners and has also created local employment.[vi] The Glenrock Wind Project has an installed capacity of 99MW and is located at the retired and reclaimed surface coal operations of a mine in Wyoming.[vii] Project examples for Europe include the Black Law Windfarm in Scotland with an operating capacity of up to 124MW. The farm is located at a former coal mine and has been extended twice since operations commenced in 2005.[viii]

Due to the weight of wind turbines, additional remediation on the former mining site is often required to ensure that the site’s surface is structurally sound. Mine dump material can be unstable due to its muddy and ashy nature. Land with previous underground mining activities can be risky due to the prevalence of sink-holes. Such risks compromises the stability of the turbine foundation.[ix] Project examples such as Glenrock and Black Law demonstrate that such risks can be successfully managed to build utility scale plants. Ground conditions and the man-made structures that are required to support turbines can, whoever, result in higher engineering costs relative to a comparable greenfields site.

Hydropower

Pumped storage hydropower generation,[1] is an attractive alternative energy storage option, especially as the global share of renewable energy technologies in power generation is increasing. Due to the intermittency of renewable energy, energy storage at a large scale balances surplus energy generation and peaks in energy demand over short coverage intervals.

There are very few examples of old mine sites with an operational hydro power plant. In addition to the solar PV plant, Summerville Mine has a seasonal micro-hydroelectric power plant that supplements power for clean-up activities.

Pumped storage is increasingly being considered as an energy storage option that can be used in old open cast and underground mines, but it has not been successfully demonstrated yet examples of this in practice yet. There are however planned projects including Genex Power’s Kidson Project in Queensland Australia. This project is located at an old gold mine and will involve a transfer of water between two open-cast pits at different altitudes. The pumped storage project capacity is projected to be 450MW, and a solar PV plant of 150MW is also planned at the old mining site.[x] The development of underground pumped water storage is also under exploration in the US and Germany; examples include Elmhurst Quarry Pumped Storage Project proposed for development at an in Illinois,[xi] and Prosper-Haniel mine in Germany.[xii] Subsurface systems are, however, often challenging due to the construction risk associated with working underground – which may drive up costs relative to surface systems.

South African context

As seen above, renewable energy projects at abandoned mines can be either small or large scale. There are signs that local stakeholders in the industry are looking into addressing the negative legacy of mining in South Africa by using greener technologies. Promethium Carbon in collaboration with Harmony Gold and the British High Commission in Pretoria has developed a toolkit focused on combining renewable energy generation and the rehabilitation of mining-impacted land in order to uplift local communities.[xiii] Although the tool-kit was developed as an outcome of a small scale community-based renewable energy project, this work represents a crucial step towards exploiting renewable energy for the creation of a positive legacy for the mining industry.

There are an estimated 4000 – 60000 abandoned mines in South Africa. While it is unlikely that renewable energy projects could be rolled out at all or even the majority of these sites due to technical or financial reasons, there could still be significant potential for the deployment of renewable energy. It is therefore important to identify opportunities for the industry, specifically in the application of solar energy technologies.