Sizing of Hybrid Supercapacitors for Off-Grid PV Applications

Solar energy generated from photovoltaics (PV) suffers from intermittent and fluctuating power output, as it generates in limited hours during the day, affected by irradiation fluctuations, and power generation does not necessarily follow the consumption profile. Intermittent and fluctuating power is mitigated by energy storage, as the generated power can be stored and used at the needed time. Integrating a supercapacitor as energy storage with the PV panel provides advantages such as increased system flexibility but also adds challenges. Using supercapacitors as energy storage outdoors, exposes the whole system to variable temperature, and this will affect the storage capacity. This paper is determining the optimal sizing of supercapacitor energy storage through performing laboratory testing under different temperatures in climatic chambers and different C-rates of discharging. Moreover, a system model for an off-grid PV-supercapacitor system with variable load is also presented together with an optimization method to size the supercapacitor storage unit that is capable of powering the loads 24 hours a day under all weather conditions.