MODELING THE VIABILITY OF UNDERGROUND COAL FIRESAS A HEAT SOURCE FOR ELECTRICAL POWER GENERATION

摘要

The objective of this study is to examine the viabilityrnof extracting thermal energy produced fromrnunderground coal mine fires for electrical powerrngeneration. Underground coal mine fires present arnhigh temperature heat source available at relativelyrnshallow depths as compared to conventionalrngeothermal resources. Several hundreds of burningrnunderground coal mines are believed to existrnworldwide. They may extend in plan area up to tensrnof square kilometers and are estimated to burn for uprnto tens of decades.rnThe performance of a closed-loop thermal energyrnextraction system, consisting of an array of verticalrnboreholes, is modeled using computer simulation. Atrnvarious underground temperatures, a two-variablernoptimization scheme is used to determine minimumrnborehole depth and mass flow rate required to yield arnfluid temperature of 100℃ entering a theoreticalrnbinary-cycle power plant. Geologic and thermal datarnfor the model are taken from field studies of an actualrnunderground coal mine fire in Wyoming, USA. Lifecyclerncost analyses are conducted to assess thernfeasibility of production of 100 kWe to 1000 kWe.rnSimulation results show that, under certainrnconditions, the concept is economically comparablernto other alternative power generation technologies.