| Abstract |
In a hot dry rock geothermal power generation system, two or more wells are drilled into hot dry rock located underground and an artificial fracture is formed by injecting high-pressure water through one of the wells. After the wells become connected by the artificial fracture, the injected water passes through the fracture and is recovered at ground level in the form of steam or hot water, which can then be used for power generation. In 1985, NEDO started R&D of hot dry rock at Hijiori, Yamagata Prefecture. By 1994, two artificial reservoirs were formed by hydraulic fracturing at an each depth of about 1,800m and 2,200 m. The long-term circulation experiment was conducted for one year and seven months (from December 2000 to August 2002) to confirm the feasibility of hot dry rock power generation. For the first year, ôDeep Circulationö was operated to evaluate the long-term performance of the lower reservoir. For the last seven months, ôDual Circulationö was operated to confirm the interaction and to evaluate the performance of injecting into both reservoirs. For the last three months of the Dual Circulation, ôGenerator Testö was also implemented to demonstrate the performance of reservoirs using a binary power unit (130KW). These circulations were successfully achieved over a period of approximately 550 days whereby valuable data was obtained towards the practical use of a Hot Dry Rock Power Generation System. |