Abstract: To solve the disadvantages of high energy consumption and low efficiency in hydraulic lift system, an innovative energy-saving technology of variable counterweight is proposed. The energy-saving concept is given and the working principles of two kinds of variable counterweight system are introduced, namely variable hydraulic counterweight and mechanical counterweight with variable speed. And the system applying the variable hydraulic counterweight is discussed in detail, including the installed power, the energy consumption, the efficiency and the poor working condition. Compared with the conventional variable voltage variable frequency (VVVF) hydraulic system, the installed power and energy consumption of the system with variable hydraulic counterweight decreases by 67% and 35% respectively, and the efficiency increases 30%, which means the system saves energy remarkably. Then the problems of the system are discussed, mainly involving efficiency, dynamic response and so on, and the solutions are presented. Finally, the development of the variable counterweight technology is prospected.

Key words: Energy consumption, Energy-saving, Hydraulic lift system, Variable voltage variable frequency (VVVF), Varying counterweight, Material flow, Numerical simulation, Review, Friction stir welding