Turbomachinery considerations for Underground Pumped Hydroelectric Storage plants (UPHS)

UPHS plant costs for plants equipped with advanced reversible pumped turbines has been considered. Equipments used include single and two-stage reversible pump/turbines with operating heads from 500 to 1500 m. The effects of machinery costs, operating heads, plant configurations and sizes has been taken into account. The results indicate that the use of advanced machinery seems to push the UPHS plant cost minimum if it exists to beyond 1500 m. The employment of advanced reversible pump/tubines seems to be economically attractive. It turns out that the problems of pump/tubines seems to be economically attractive. It turns out that the pump/turbine efficiencies and the so-called charge/discharge ratio are very important design parameters for UPHS applications. The interactive effects have been analyzed. The results show that under certain conditions a pump/turbine option with higher charge discharge ratio at the expense of somewhat lower operating efficiency may be desirable.