Combined Cycle of Steam Topping and a Binary Bottoming Power Plant

Abstract

Geothermal energy is a naturally occurring, semirenewable source of thermal energy. Power generation from geothermal energy is cost-competitive with most combustion-based power generation technologies, and it offers additional benefits to society by producing significantly less carbon dioxide and other pollutants per kilowatt-hour.

The four basic geothermal cycles are: direct steam cycle, flash steam cycle, binary cycle, and a combined cycle which is used to improve plantÆs efficiencies. Combined cycle is composed of flash vessel wherein the flashed steam is fed to steam turbine, and the brine from flash vessel is fed to binary cycle.

Upper Mahiao Power Plant of CalEnergy International, Ltd. - Leyte Operations is a combined cycle. It is composed of two binary cycles; one is a simple brine binary cycle, and the other one is a combination of direct steam topping cycle with a binary bottoming cycle. The secondary working fluid used in these two binary cycles is normal pentane.