closed-loop pumped-storage power generation
Technical term in energy engineering. Refers to a pumped-storage hydroelectric system that does not rely on natural inflow, using only water cycled between upper and lower reservoirs.
Closed-loop pumped-storage power generation is a pumped-storage method that does not depend on natural river inflow.
揚水発電 is a broader term for pumped-storage hydroelectricity, which may include open-loop systems with natural inflow. 純揚水発電 specifically refers to closed-loop systems without natural inflow.
Compound of 純 (pure, solely) + 揚水 (pumping water) + 発電 (power generation). The term is a modern technical coinage.