Modeling and experimental analysis of battery charge controllers for comparing three off-grid photovoltaic power plants

Heliyon. 2021 Nov 8;7(11):e08331. doi: 10.1016/j.heliyon.2021.e08331. eCollection 2021 Nov.


The study of battery charge algorithm as a sole power storage agent in off-grid systems is essential. The battery charge algorithm has various methods, and the battery in these methods relies on the quantity of charges. Hence, a charge controller is used to safeguard and regulate battery charge and discharge for off-grid photovoltaic (PV) systems. This study presents the 11.4 kWp power plant analysis comprising three 3.8 kWp each of off-grid, hybrid and grid-assisted systems with battery capacities of 900 Ah, 1235 Ah and 910 Ah, respectively, where all the systems were reconfigured to function as off-grids. The battery charge controller charges the lead-acid battery using a three-stage charging strategy, including constant current, constant voltage and float charge stage. A DT80 data logger was installed to simultaneously record the electrical parameters of the systems, while Kipp & Zonen CMP 11 pyranometer was selected to measure solar radiation data. Experimentation with three electric bar heaters, each with fan and humidifier, were used as loads to draw constant power of 1.2 kW from batteries of each system on charging and discharging on an overcast and clear sky days for a week. The useful study is performed in the following ways, MPPT tracking performance, battery charging and discharging performance and charge controller efficiency. The performance results reveal that the MPPT can track the PV module maximum point at solar irradiance from 07h15 to around 12h00 maximum power tracking efficiency. An irradiance of illumination fluctuates from 5 W/m2 to 850 W/m2 while the electrical energy consumed by the loads in off-grid, hybrid and grid-assisted systems are 456.12, 568.87 and 80.00 Wh, respectively. It is estimated that individual owners could charge electric appliances from residential and commercial buildings of solar arrays of clean, renewable solar energy.

Keywords: Battery system; Charge and discharge; Charge controller; Off-grid system; Photovoltaics.