Heat recovery potential of mine water treatment systems in Great Britain

Treatment of pollution from abandoned coal mines often requires significant inputs of electrical power, particularly at sites where long-term pumping of mine water is required. Given the large fossil fuel generation element of the UK electricity supply network, this has a direct impact on carbon emissions. The potential for recovery of low enthalpy heat at mine water treatment sites in Great Britain, such that they could become net sources of energy during operation, rather than consumers, was explored using data from April 2014 to March 2015. To do this, an inventory of coal mine water treatment systems across England, Scotland and Wales was first collated, including key variables for each site. The heat energy which could potentially be recovered was then assessed against the energy consumption of each site and reviewed at a national scale. It was found that 47.5 MW of thermal energy was available for recovery from mine waters, compared to 2.3 MW of electrical power already committed for pumping and treatment of these waters. Recovery of thermal energy might be achievable by the use of heat pumps for space heating of nearby properties. Yet, because of the high carbon cost of UK grid electricity required to power heat pumps, this approach would offer only very modest CO2 savings over domestic gas central heating. Calculations made in this paper suggests that just 0.33 kt CO2 savings are achievable using this approach, compared to existing emissions of 10.8 kt CO2 entailed by the pumping and treatment sites themselves.