EVALUATION OF MAGMA ENERGY POWER-GENERATION SYSTEMS

A study of power generation schemes for magma energy systems is reported. In the magma energy concept thermal energy is removed from the molten region below the Earth's crust by circulation of water from the surface. The heated water is then assumed to drive a thermal cycle. Thermodynamic analyses of three general cycles are considered. In the first, the heated water is assumed to be used directly in an expander. This case is treated here with a variety of expander efficiencies to model conventional turbines as well as direct expansion devices when the entering state is liquid. A closed Rankine cycle (where the well fluid exchanges heat with the power cycle fluid) is also considered. Finally, a flashed cycle is also evaluated. The state of the input fluid to the power cycle is determined from a downhole model that represents many facets of the anticipated heat transfer and fluid flow. Power output and other results are presented as a function of mass flow rate, effective thermal conductivity of the heat exchange zone, and specific cycle parameters. Conclusions are drawn about which cycles show potential for maximizing power output. It is shown that the magma energy scheme holds great promise for economic power generation. © 1990.