Modelling and Simulation of an Off-Grid Photovoltaic System using Hybrid Energy Storage System for Electrification in Nigeria

Abstract

In this work, the objectives of this research is to simulate the combination of a photovoltaic system with multiple energy system comprising of a battery and a supercapacitor. The results from the modelling of the photovoltaic system was compared with the current, voltage and power output of an LG datasheet. From the results obtained it was observed that when the area of the photovoltaic panel was reduced slightly by 0.01, the output current decreased by 0.001 but an increase in the area did not result in any significant change on the output current or voltage .This shows that the area of the photovoltaic panel does not affect the output current, voltage and power. During discharging mode (battery only), using a controlled current source which was connected to a load of 12.5A, State of Charge and current at 50% and 100AH respectively for 3,600s, we obtain Iout equals to 12.5A, SOC equals to 50% with Vout equals to 13.78V. Discharging occurs, although slowly. During charging mode (battery only), using a controlled current source which was connected to the load, at same voltage.We obtained SOC equals to 50.0007%, Vout equals to 13.81V, I equals to 10.0A. Charging occurs, also slowly. During discharging mode (battery and supercapacitor connected to the off-grid Photovoltaic panel to an AC load), at an initial SOC value equals to 50%, we obtain SOC equals to 49.95, Iout equals to 35A and Vout equals to 13.75. During charging mode (battery and supercapacitor connected to the off-grid Photovoltaic panel to an AC load), we obtain SOC equals to 50.31%, Iout equals to 220A, Vout equals to 14.07V. The output current and voltage of the off-grid photovoltaic system rose faster when connected to the supercapacitor.

Introduction

The text explains the design and modeling of photovoltaic (PV) systems combined with hybrid energy storage for renewable energy applications. It highlights that renewable sources like solar power often produce energy that does not match demand, making energy storage systems essential. Advanced storage technologies such as supercapacitors and flywheels can be combined with batteries to balance power and energy needs.

PV systems can be standalone, grid-connected, or hybrid, and are widely used for electricity generation, especially in remote areas. Their performance depends on factors like solar irradiance, temperature, and system design. Microgrids are introduced as efficient small-scale power systems that integrate multiple energy sources and storage units, offering reliable electricity without extensive infrastructure.

The methodology involves mathematically modeling and simulating PV systems and hybrid energy storage (battery + supercapacitor) using tools like MATLAB/Simulink. Key electrical parameters such as photocurrent, saturation current, and resistance currents are derived and modeled through equations.

Overall, the study demonstrates that integrating hybrid energy storage with PV systems improves system performance, reliability, and efficiency, particularly in off-grid applications.

Conclusion

In this work, the output current decreased by 0.001A but an increase in the area did not result in any significant change on the output current and voltage. This shows that the area of the photovoltaic panel is independent of the output current , voltage and power. It was also observed that the supercapacitor helps in boosting the charging capacity of the battery and reduces its discharge. The supercapacitor possesses unique properties that can complement other energy storage technologies, such as batteries due to its fast charge and discharge capability, highly reversible process functionality, high power density, high recyclability and relatively small internal resistance. It is an attractive alternative in hybrid electric energy systems. An equivalent supercapacitor model was formalized based on electric characterization, which was used in simulations of the off-grid PV/HESS model. When characterizing the supercapacitor, a capacitance voltage dependency was detected, which is important to take into account, since it affects the output current and voltage of the hybrid energy system. When conducting simulations of the passive hybrid system, it was found that the model probably should be simplified in order to adequately capture the system\'s short-term behavior under transient loading. Regarding performance of the system, we found that when the resistance of the applied load demand was varied, the passive hybrid system could in theory meet a pulse load amplitude up to nine times as large as the rated power of the battery. The simulation confirmed that the power rating of the system can be increased by hybridization, The output current decreased with decreasing area of the panel while it remained fairly constant with increasing area of the photovoltaic panel. It was found that when the system experiences increase in load demand the state of charge of the battery-only system experienced a sharp decline or slow charge with respect to the amount of current that is being supplied from the photovoltaic panel. On the other hand, when load demand is being varied using the battery-supercapacitor hybrid system the battery experienced a slow discharging and fast charging. This is as a result of the supercapacitor being utilized, relieving the battery of large voltage fluctuations and reducing the maximum battery current.

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Copyright

Copyright © 2026 T. C. Atasie, L. O. Uzoechi, S. O. Okozi. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.