Feasibility of using the water from the abandoned and flooded coal mines as an energy resource for space heating

This research project aims to study the feasibility of using the water from the abandoned and flooded coal mines for space heating applications using a Ground Source Heat Pump (GSHP) in open loop configuration and take a conceptual idea to a commercial deployment level. The flooded coal mines are the legacy that has been left behind after the three centuries of continuous operations by the coal mining industry. The closure of all coal mines in the UK has led to the flooding of all those abandoned underground workings and due to the subsequent rise in the water levels; mine water is posing a threat to the water table. Mine water in the abandoned coal mines can be considered as a low enthalpy energy resource with very little practical applications, however it can be upgraded to a high enthalpy resource by using a heat pump and used for heating applications. Heat pumps are considered as low carbon heating systems, using them for the space heating purpose is economically and environmentally beneficial compared to the conventional heating systems. A generic methodology has been developed to help in evaluating the process of harnessing the energy from mine water for the heating applications using an open loop GSHP. The methodology covers the core technical, environmental and economic aspects. An MS Excel based tool has been developed to assist in the design and commercial evaluation of a mine water based heating system. Financial model is created using Discounted Cash Flow (DCF) method to analyse the feasibility of implementing the system. Theoretical case studies have been conducted for three different sites using the software tool. Two pilot plants have been constructed at two different sites, namely at Markham, Alkane Energy and at Caphouse, National Coal Mining Museum (NCM) for the experimental work. The field trials from the two pilot plants show promising results in terms of reducing both the operating costs and carbon emissions. It also shows that with a careful design, the threat posed by mine water to the operations and maintenance of the plant can be minimised. The three theoretical case studies conducted show that the energy from the flooded coal mines is a good alternative source for heating and can contribute significantly in reducing the operating costs and the carbon emissions at those proposed sites. The abandoned mines underlie large parts of UK and at many sites, the water is being pumped out to prevent it from coming in contact with the water table and pollute the water bodies, these sites are ideal to implement the mine water based heating system, as they can support large thermal loads. The energy from the flooded coal mines is ideal to supplement or even replace the conventional sources of heating, as it is reliable and contributes to a reduction in carbon emissions and operating costs. Even though the initial capital costs are higher than other conventional heating systems, it becomes economically feasible with a good payback period, when additional financial incentives in the form of Renewable Heat Incentive (RHI), currently being offered by the government for GSHP technology, is taken into consideration. This research work shows that the energy from the mine water can be profitably harnessed to heat the buildings. The unique design developed to design the system, achieves continuous operation and minimises the maintenance requirements, even when a heavily polluted water is used

Performance analysis of using mine water from an abandoned coal mine for heating of buildings using an open loop based single shaft GSHP system

The application of ground source heat pumps (GSHP) for heating and cooling of buildings is currently increasing in popularity in the UK and globally. Traditional GSHP systems use the naturally available geothermal gradient of earth for heating and cooling purposes using open loop or closed loop systems. In this paper, the use of mine water from a flooded coal mine for heating of buildings is presented using a GSHP system with an open loop configuration. The novelty of this approach is that a single shaft is used to extract the warm water and inject the cooler water back into the same shaft, thereby minimising the area needed, initial capital costs in constructing a doublet system and also potentially overcome the time consuming process to address related environmental agencies regulation regarding the discharging of the mine water. The relatively stable temperature low enthalpy of mine water contained in the abandoned and flooded coal mines are ideal to be used for both heating and cooling of buildings when used in conjunction with heat pumps. The GSHP is considered to be an effective means of reducing the carbon emission as it gives more output in the form of thermal energy in comparison to the electrical energy it consumes as input. This research work reports on the performance of the system over the winter season and its long term potential in converting the mine water from an environmental liability to a sustainable energy resource and offers a means to regenerate the former coal mining areas

Water from abandoned mines as a heat source: practical experiences of open- and closed-loop strategies, United Kingdom

Pilot heat pump systems have been installed at two former collieries in Yorkshire/Derbyshire, England, to extract heat from mine water. The installations represent three fundamental configurations of heat exchanger. At Caphouse Colliery, mine water is pumped through a heat exchanger coupled to a heat pump and then discharged to waste (an open-loop heat exchange system). The system performs with high thermal efficiency, but the drawbacks are: (1) it can only be operated when mine water is being actively pumped from the colliery shaft for the purposes of regional water-level management, and (2) the fact that the water is partially oxygenated means that iron oxyhydroxide precipitation occurs, necessitating regular removal of filters for cleaning. At Markham Colliery, near Bolsover, a small amount of mine water is pumped from depth in a flooded shaft, circulated through a heat exchanger coupled to a heat pump and then returned to the same mine shaft at a slightly different depth (a standing column arrangement). This system’s fundamental thermal efficiency is negatively impacted by the electrical power required to run the shaft submersible pump, but clogging issues are not significant. In the third system, at Caphouse, a heat exchanger is submerged in a mine water treatment pond (a closed-loop system). This can be run at any time, irrespective of mine pumping regime, and being a closed-loop system, is not susceptible to clogging issues