Mining is one of the most energy intensive industries in the world, leaving operators exposed to unpredictable and expensive energy markets. A new study from the Earth/Mine Energy Research Group (EMERG), comprising researchers from the University of British Columbia (UBC) and McGill University, makes the case that mines can reduce their reliance on fossil fuels by sourcing geothermal energy from water that collects on site in active underground mines.
Ali G. Madiseh is an assistant professor at the Norman B. Keevil Institute of Mining Engineering at UBC, and is part of EMERG, which researches energy-efficient technologies in mining. EMERG has spent a decade studying how geothermal energy can be extracted from water in underground mines to serve either nearby communities or the mines themselves. Data collected at over 20 mine sites demonstrate that mines that implement the technology will see considerable economic and environmental benefits.
CIM: Has geothermal energy been extracted from underground mines before?
Madiseh: Canada was the first place in the world to establish geothermal energy using a mine in 1987. An abandoned coal mine in Springhill, Nova Scotia, currently heats a plastics manufacturing factory and a couple of other surface buildings. However, the project didn’t grow to its full potential. The best global example of how a community can benefit from geothermal energy from a mine is the town of Heerlen in the Netherlands. There, an abandoned coal mine is being used as a geothermal reservoir, not only to extract heat, but to store energy. Whole clusters of the city are being provided with energy for heating and cooling.
CIM: How does the technology work?
Madiseh: Traditionally, water that collects underground in mines is constantly pumped up to the surface by pumps called “sump pumps.” At the surface, the water is treated and returned to the environment. There is a considerable amount of water in some mines, often in the range of 300 to 1,000 litres per minute.
Our idea is to install heat pumps or thermal chillers as a step in the dewatering process [of an active mine]. Underground mine water can be as hot as 30 C, and by the time it has reached the surface it is around 15-18 C, depending on how much water the mine has. The heat pump or thermal chiller would remove 4-6 C of heat out of that surface water and “upgrade” the heat to a higher temperature range of 40-60 C using a small amount of electricity.
Heat pumps and geothermal chillers are both refrigeration equipment, working in the same way that a kitchen fridge takes cold air and makes it colder. They contain an evaporator and a condenser. In the evaporator, the low-temperature refrigerant receives the heat from the mine water, resulting in a raise in refrigerant temperature. In the condenser, the higher temperature refrigerant conveys the heat to the circulating fluid of a heating system, in either the form of water or air. This can then be conveyed to the end user.
Heat pumps and thermal chillers are very mature technologies and a good number of Canadians have been using geothermal heating in their homes for decades. However, this is the first time that geothermal energy would be extracted from an active mine site for mine ventilation purposes.
CIM: Where can the geothermal energy be used on a mine site?
Madiseh: Canada’s long, cold winters mean mines need a huge amount of pre-heating to function, often for over 160 days of the year. You can’t draw -30 to -40 C air into an underground formation. Humans can’t operate and all the pipes, bearings, openings and shafts will freeze and break. So the air is warmed up using gas-powered heaters before being sent underground. This is currently done at a huge cost, using millions of gallons of natural gas or propane. We are thinking of doing the same with the geothermal energy extracted from the mine water.
The geothermal energy can also be used to cool Canada’s ultra-deep mines in the summer months.
CIM: How else can the energy be used?
Madiseh: Local communities can also benefit from geothermal energy from mines, like in Heerlen. A community must be near the mine for this to work, as it’s not economically viable to transport heat long distances. Sudbury would be perfect for this. Herleen is a success story, and they only have one mine; in Sudbury, there are more than ten mines, which could power the entire city.
There is great public relations value for mining companies in projects that provide a clean source of renewable energy to local communities, especially as the mine will continue to harvest heat long after it has been decommissioned. However, we appreciate that a lot of negotiations between the mining company and local communities are required for this to work. So for the moment we are focusing on how the energy can be used to heat and cool mine sites.
CIM: What types of benefits could mines see from extracting this type of energy?
Madiseh: Our study demonstrated that mines can save between $200,000 and $300,000 each year in energy costs. And this is the most conservative scenario; it varies from case to case, depending on how much thermal heat a mine produces and its current energy bill.
There are huge environmental benefits. Mines will drastically cut their fossil fuel intake and their carbon emissions. On top of this, in a few years, the federal government is likely to introduce a carbon tax. Mines that develop this technology can save on these taxes, and even make revenue by exchanging credits if the tax involves a cap and trade system.
Finally, geothermal energy is not dependant on changes in the energy market (beyond the small amount of electricity needed for the geothermal chiller or heat pump). Costs will no longer be bound to the unpredictable cost of fossil fuels. This is what we call “energy independence.”
CIM: Are you proposing that the technology be implemented in both active and abandoned mines?
Madiseh: If a mine is abandoned, there are hurdles that need to be resolved before the technology is installed. For example, underground galleries can be blocked and water may not be able to move through these openings. There has to be drilling tests, which increases the cost of the project. But an active mine sidesteps these issues. And unlike any other European or first world countries, Canada has a lot of active mines, which is why the technology is perfect here.
Ideally, we are looking at implementing the technology in opening mines so that the company can invest in the geothermal system and cut costs by avoiding the more conventional fossil-based heating system entirely.
Installing the technology has some costs and will have some requirements on infrastructure, but it’s not a huge renovation project.
CIM: Given the success in Heerlen, why has geothermal energy not already been adopted in mine sites in Canada?
Madiseh: First off, in Europe they have a greater incentive to turn to projects like this. Electricity is more expensive there and they rely on imported natural gas. And while the capital investment involved in installing and maintaining these geothermal projects does pay off, Canada is less inclined to turn to it, as we have relatively cheaper energy.
Moreover, the project in the Netherlands wouldn’t have worked without support from the local community, who advocated for the project. Canada needs champions to go to the community, get their interest and backing for such projects, and go back to mining companies with plans of collaboration and support.
CIM: Will we see it adopted by mines soon?
Madiseh: We are in the process of talking to mines to entice them to invest in these technologies and we are hoping to have their support in the near future. I can’t mention any names or titles at this point, but hopefully we will have some good news soon.
The process takes time because the mining industry has a genetic attitude of only investing in technologies that are already well-proven in other industries. While geothermal energy is not new – it has been used to heat residential buildings for more than 30 years – implementing a geothermal chiller or geothermal heat pump in an active mine is a new concept, which is why miners are wary.
We are hoping that they put this attitude to the side and invest in technology especially designed for their application. We need one mine to become our champion project, which will in turn encourage other mines to adopt the technology.