| Authors |
Yamada, Y., Taguchi, Y., Yamaoka, K., Fujita, T. and Morita, K. |
| Abstract |
A unique system, as illustrated in Fig.1 and named as Downhole Coaxial Heat Exchanger (DCHE) System, to extract geothermal energy is proposed. Heat extraction medium (water) is heated during its downward flowing through annulus and flows up via insulated inner pipe without cooling down by downward flowing water as well as lower temperature formation at upper zone. The system is featured with (1) no pollutant emission, (2) minimum drilling risk to hit empty (non-productive) well, (3) simple configuration, etc. Details of the DCHE system and its anticipated performance are introduced by Morita and Sugimoto (1988), where the Effective Thermal Conductivity of the formation was assumed to be 2.7, 10, 20 and 30 kcal/mhK (hereinafter referred to as Cases I, 2, 3 and 4, respectively). One of the possible utilizations of the extracted heat by the DCHE would be power generation. of which the authors studied technoeconomical feasibility. Combination of the DCHE with Biphase turbine and stea~ turbine system is selected to convert the extracted thermal energy to electrical energy efficiently, since the turbine is fed with liquid phase hot water at saturation pressure, but not super heated steam. The principle and the most effective combination of the consisting unit systems are discussed by Sugimoto and Morita (1988). Design parameters of the plants to be considered in 'this report are summarized in Table 1. which consist of 15 DCHEs and one power generation plant. The design of the DCHEs and the surface facilities of the above mentioned system, which are basic information for the economic analysis (Fujita, T. et al., 1988). are described in this paper. |