Hot dry rock flow testing: What has it told us. What questions remain.

摘要

Flow testing at a pilot facility at Fenton Hill, NM has begun to provide answers to important questions about the practicality of extracting geothermal energy from hot dry rock (HDR). The plant was operated for continuous periods of up to 112 days with no drop in the temperature of water produced from an artificial geothermal reservoir and, in fact, evidence of increasing fluid access to hot rock as the test proceeded. Water consumption was shown to decline with time to the lowest levels ever achieved in HDR flow testing. Costs of pumping water through the HDR system were documented for the first time and the generation of excess energy was demonstrated. Geochemical results indicated low levels of dissolved solids and gases with no emissions to the environment during normal operations. Several issues regarding the construction and operation of HDR geothermal plants remain to be resolved. The long-term sustainability of the resource has not yet been unambiguously demonstrated. Many costs related to construction, operation and maintenance of HDR plants have yet been adequately addressed. Because so few HDR reservoir have been created, there is as yet limited confidence in the geographical and geological versatility of the technology. Nevertheless, substantial progress has recently been made toward showing that HDR can be an efficient source of clean energy.