Design optimization of hybrid solar-gravity energy storage for elevation system

Abstract

Solar energy has become an increasingly important component in the global shift toward renewable energy. However, conventional solar energy systems that depend only on chemical batteries often face limitations such as high cost, energy degradation, and short operational lifespan, particularly in elevation-based applications. The objective was to design and optimize a hybrid energy storage system by integrating solar PV, battery, and gravity-based storage, and to evaluate its performance under real operating conditions. The goal was to optimize the design using a 50-Watt Solar PV, an 18Ah SLA Battery, and a Water Gravity Energy Storage Tank. The method included three steps and used five data loggers: a flow meter, a pyranometer, and three-watt meters. First, a fully charged SLA Battery was tested at various tank heights (from 1.5m to 3.5m) every 15 minutes. Then, the 50-Watt Solar PV was tested directly at a height of 3 meters. Lastly, the Solar Hybrid Gravity System with Battery Energy Storage was monitored over seven days at a 3-meter height. Energy use was measured through the SLA Battery, Solar PV, and a 22-Watt Water Pump at different tank heights to see improvements in efficiency and battery life. The results showed a 600% improvement in battery performance at 80% Depth of Discharge (DOD), proving the battery's potential as a reliable backup power source and extending its lifespan. The SLA Battery had a 22.1% energy loss during charging and discharging at 5% DOD, while the 22-Watt Water Pump achieved a flow rate of 11.0 L/min at peak solar irradiance of 900 W/m², with a maximum motor power of 24.32 Watts. A minimum of 300 W/m² solar irradiance was needed for the pump to run efficiently. In conclusion, the energy efficiency of the solar hybrid gravity system was optimized, reducing reliance on the battery and extending its lifespan, making it a sustainable solution for elevation applications. This system can be applied in water pumping, agricultural irrigation, and elevator systems in off-grid or rural areas, offering a cost-effective and environmentally friendly energy storage alternative.