On Efficiency of Load-Lifting Rope-Traction Mechanisms Used in Gravity Energy Storage Systems

According to the American Council for an Energy-Efficient Economy, transition from conventional wire ropes to PU-coated multiple-rope belts has significantly increased energy efficiency of lifting mechanisms, so expanding this experience to the design of gravity energy storage systems seems very promising. In the present paper, an algorithm to calculate the round-trip efficiency (RTE) of gravity energy storage systems with a rope traction mechanism using PU-coated multiple-rope belts is presented. The algorithm includes a mathematical model describing belt/hoisting unit interaction. Efficiency calculation for a specific design of a gravity energy storage system is given as an example. High sensitivity of the system's RTE to the mechanical parameters of the lifting mechanism is demonstrated. The estimated RTE has comprised 86 % for a 900-kW lifting system that transports a weight at a nominal speed of 1.5 m/s. Such multiple systems working together as a single facility can become a powerful gravity storage.