Abstract:

The research examines the feasibility of Underground Thermal Energy Storage (UTES) application in Australian underground mines and their respective camps. UTES offers a viable solution to mitigate the challenges of utilizing renewable energies and its associated infrastructural costs and security.

Australia's diverse geological formations, particularly Western Australia, have advantages for UTES systems, such as Aquifer Thermal Energy Storage (ATES), Borehole Thermal Energy Storage (BTES), and Cavern Thermal Energy Storage (CTES) and its applications in the mining sector are significant which include enhancing the utilization of surplus energy, alleviating peak energy demand, lower cost option, reducing strain on the power grid, creating a more stable and reliable energy supply for mine operations and also serving as refrigeration system for underground mine ventilation.

Additionally, through this research, it was realised that the granite-rich areas in Western Australia are well-suited for the application of UTES, especially for the BTES system. These areas have high thermal conductivity, which is important for effective energy storage and retrieval. For instance, the rock formations (sandstone, quartz, felspar, plagioclase, mudstone, andesite, conglomerate and gritstone) have an average thermal conductivity of around 3.656 W/m·K which makes it ideal for the BTES systems.

The integration of refrigeration system with the BTES system and renewable energy sources such as solar thermal collectors and geothermal heat pumps presents significant potential for cost and emission reduction. At 85% efficiency, the integrated system operates effectively at a high level to convert and utilize large amount of energy which resulted in a 25% reduction in the annual peak electricity demand with cost savings of approximately $200,000. The BTES system have the ability to store annual total energy requirement of 253,924 kWh/year during low demand periods and release it during peak times with optimal temperature control which leads to improved comfort and safety for workers.

Despite the high initial capital investment, the economic evaluations indicate that UTES systems offer long-term financial advantages through lower operational expenses and energy conservation. A specific example involves the evaluation of this BTES project with an initial investment of $1,661,696 and annual cash flows of $114,788, where calculations of the Net Present Value (NPV) and Return on Investment (ROI) indicate a payback period of around 14.5 years and
an ROI of 72.7%. In the situations where the initial investment is decreased by 30%, the net present value (NPV) turns positive at around $62,460, showing better financial feasibility. Additionally, increasing the annual cash flows to $200,000 raises the NPV to about $473,304, with a return on investment (ROI) of 200.8% and a payback time of 8.3 years.

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Mr. Oscar Opoku