Abstract:

A small off-grid wind-photovoltaic pumped hydroelectric energy storage (PV-PHES) hybrid system for remote rural areas is proposed, based on the complementary characteristics of wind and solar energy and an open well common in rural areas as a lower reservoir for a PHES system. In this paper, a novel power generation technique is used, where the output power and voltage of the system are unaffected by changes in wind speed or solar irradiation and does not require the use of batteries, inverters, controllers, or controlling circuits. A mathematical model of the proposed system is also established in this paper. The simulation and comparative analysis of the power output characteristics of the constant voltage power supply system is carried out using real data of a remote rural area in the Hunan Province over a period of 24 hours. The results indicate that the proposed system can achieve continuous and stable operation day and night, with an output power almost equal to the design value of 0.3 kW, and a nearly constant output voltage of 220 V. During the peak hours of 822 h, the average output power of the whole system was 294.5 W, the maximum value reached 300 W, and the average output voltage was 217.8 V, with a power deviation of 1.8% and a voltage deviation of 1% from the design value. Compared to the results of the combined operation of wind-PHES and PV-PHES hybrid systems, the power deviation is reduced by 28.8% and 34.8%, respectively, and the voltage deviation is reduced by 27.7% and 34.1%, respectively. The proposed system has the desirable features of simplicity, reliability, low failure rate, no pollution, and the ability to generate constant power at a constant voltage, which helps to provide low-cost and high-quality electricity to remote rural residents in areas with poor wind and solar resources.

Key words: wind energy, photovoltaic power, pumped hydroelectric energy storage, constant voltage