Mory Ghomshei, British Columbia Institure of Technology
With an average temperature gradient of 20 to 25°C/km, the virgin rock temperature at a depth of 2000m in most mines can reach 45 to 60°C. Conventional (centralized) cooling methods in such thermal conditions could lead to exorbitantly high operating costs. Distributed water to air geothermal heat pumps can significantly reduce the cost of cooling, through using the environmental factors for optimization of heat pump operating parameters. Costs of centralized absorption chillers (using natural gas as the source of energy) are compared with those of localized in-mine heat pumps. It is shown that distributed heat pumps can be more cost-effective in most t cases, especially when the waste heat from lower mine levels are used for heating shallower mine workings or for providing energy to facilities at the surface. The present paper discusses innovative ideas in cooling deep mines, through efficient use of distributed heat pumps (using mine waters as the heat carrier). Viability of distributed heat pumps and their restricting economic conditions (such as price of electricity and NG) are discussed. The ratio of the price of NG to Electricity is used as an indicator in assessing viability of distributed heat pumps in mine cooling. Economic viability of a 1MW demonstration project for a Sudbury Mine (e.g. Creighton Mine) has been modeled and conditions for viability of distributed heat are discussed. A 20 year life cycle model has been presented and sensitivity of the cash flow to major factors (e.g. temperature gradient, price of Natural gas, Price of electricity, mine depth, and outside air temperature) are discussed. The price of Natural gas and electrify are found to be the most important factors in deciding between the two systems.
