Innovative Approach for Heating of Buildings Using Water from a Flooded Coal Mine Through an Open Loop Based Single Shaft GSHP System

Geothermal energy, deep and shallow, has always been identified as an important renewable energy resource. The stable temperature and relatively low enthalpy of mine water contained in the abandoned and flooded coal mines have the potential to form a geothermal resource to be used in conjunction with heat pumps to provide heating and cooling for buildings. The usage of heat pump for space heating and cooling can be classified as a low carbon technology and if heat pump is powered by solar or wind energy it can be classified as a truly renewable technology. This paper presents a novel application of Ground Source Heat Pump (GSHP) for space heating and cooling using a flooded coal mine through an open loop based single shaft system. In this novel application, a single shaft is used for both extraction and injection of mine water for the heating application. This research work will report on the performance of the system and its long term potential in comparison to standard gas boilers heating systems. The usage of a single shaft system has been found effective in developing an efficient heating system with reduced cost and neutral environmental impact

The design and development of an innovative simulator for an open loop system for extracting energy from flooded coal mines

Water source heat pumps, in comparison to air-to-air heat pumps, have significant advantage for heating or cooling applications due to the relatively regulated temperature of most water resources. In the UK, similar to many other countries, disused coal mines have untapped potential for low cost green energy due to the flooding of coal mines with water at reasonable warm temperature due to the availability of geothermal energy at different depths. This allows to use water source heat pumps in locations away from rivers and seas for heating and cooling applications. Extracting energy from flooded coal mines using water heat pumps with open loop systems is still relatively a new concept, but can provide much heating capacity due to eliminating the time needed for heat transfer between the external environment and the heating loop in case of closed loop systems. The use of real systems to conduct research could be an expensive task or impractical to users of the application such as the residents of the served building. On the other hand, computer simulation includes significant assumptions that might not be accurate in many real situations. In this paper, the authors have developed a small scale simulator to help in understanding such energy systems and to conduct research in this field for the benefit of researchers, educators and students within the applied and renewable energy field. The paper describes the detailed design, the complete prototype and initial assessment of the system using infrared thermography and temperature monitoring. The results show that the system has been found successful in conveying the concept of extracting energy from coal mines and to characterize the general performance

Hydrochemistry and stable isotopes as tools for understanding the sustainability of minewater geothermal energy production from a ‘standing column’ heat pump system : Markham Colliery, Bolsover, Derbyshire, UK

The abandoned workings of the former Markham Colliery are still in the process of flooding. They are being exploited, via a‘standing column’heat pump arrangement in Markham No. 3 shaft, to produce thermal energy.From 2012, water was pumped from 235 m below ground level in the shaft at c. 15 °C and 2–3 l/s, through shell and tube heat exchangers coupled to a 20 kW heat pump, to supply space heating to commercial offices.The thermally spent (cool) water was returned to the same shaft at c. 250 m bgl at around 12 °C. The minewater contained iron, c. 6000 mg/l chloride, and was highly reducing. Avoiding contact with oxygen was effective in preventing problems with ochre scaling. In January 2015, taking advantage of rising water levels, the pump was repositioned at 170 m bgl, and the reinjection diffuser at 153 m bgl. Since then, both iron concentration and salinity have fallen significantly, suggesting stratification in the shaft. Stable isotope data from sampling in 2015 generally show little variation. Sulphate δ34S exhibits values typical for British Coal Measures (c. +5‰),whilstδ18O/δ2H indicate influence of fresh meteoric waters. Chloride and sodium concentrations have gradually increased since May 2015, possibly indicating a renewed influence of deeper, more saline, waters and reflecting the gradual rise of mine water in the shaft. Further monitoring of mine water chemistry and isotopic compositionis required to better assess the sustainability of the Markham heat pump scheme and advise on optimal management of this mine water resource

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

Extracting energy from flooded coal mines for heating and air-conditioning of buildings: opportunities and challenges

Extraction energy from flooded coal mines for heating and/or air-conditioning applications could provide a low-carbon and sustainable technology for the future. In heating applications, the implementation normally utilises heat pump technologies to upgrade the temperature of water from a nominal value of normally about 12 to 20 °C to a level above 45 °C. For cooling applications, the water could be used directly or via a heating pump for the cooling process, depending on the temperature of the water. This paper outlines two case studies implemented in the UK at Caphouse Colliery and Markham Colliery. The paper highlights the opportunities and challenges of the technology; it compares between the two systems in terms of configuration, water quality and the need for maintenance. The paper also outlines the commercialisation aspect of the technology and the potential challenges and opportunities captured via a technical workshop and an online survey. The paper also discusses the geohazard prospective of coal mines when used for extracting the thermal energy. The results show that extracting energy from flooded coal mines is unlikely to create any significant geohazard risk, but has the benefits to develop and regenerate the former coal mining areas. The technology can be used to provide low-carbon sustainable energy to homes and businesses in the UK towards zero-carbon future. However, more effort is needed to enhance public awareness and encourage future investments to allow the technology to be utilised in new and existing residential and commercial buildings