A Self-Contained Architecture for Energy Recovery in Hydraulic Elevators Available to Purchase

This paper presents a novel energy storage and recovery architecture for speed-controlled hydraulic actuation in hydraulic elevators. The study is motivated by a need to increase efficiency in the fluid power industry, in general, and hydraulic elevators, in particular. In contrast to previously employed systems, the proposed architecture eliminates the need for throttling and inefficient energy conversions in electric motor/generators. The system has 6 main components: 1 actuator, 1 hydraulic transformer composed of 2 pump/motors, 2 accumulators, a reservoir or small auxiliary accumulator, and a small auxiliary electric motor to recharge accumulators. By operating in 3 different modes, the system is always able to recapture energy when decreasing actuation speed, and return energy if needed when increasing actuation speed. Assessment of the proposed architecture is accomplished through high-fidelity simulations and a simplified analytical model. The analytical model is derived with the pump/motor displacements as a single input. A heuristic rule-based control is developed to control the high-fidelity simulation through an operation cycle and a comparison to a counterweighted elevator simulation is done to validate energy advantages of the novel system. Preliminary results demonstrate the ability of the system to follow a velocity profile using a single input. Comparison with a conventional counterweighted hydraulic elevator shows a large increase in energy efficiency. It is believed the architecture may have additional applicability to a wide range of hydraulic machines, such as heavy equipment used in construction, manufacturing, forestry, etc.