An optimisation and sizing of photovoltaic system with supercapacitor for improving self-consumption

Abstract

On-Grid photovoltaic household-prosumers systems without energy storage typically undergo many fast and short-term energy flows to and from the grid due to the solar irradiation fluctuation and rapid local fluctuations of load. This negatively affects grid system stability and decreases renewable energy system self-consumption and efficiency. Battery energy storage may resolve these issues; however, with considerable investment and maintenance cost, they usually involve unreasonable expenditure. On the other hand, supercapacitors are the most promising, cheap and no maintenance, a short-time electrical energy storage device. Due to long-term reliability and very-high current in a short-time, they can be used as short term power backup and grid stabilisation device. In this work a photovoltaic system working with a supercapacitor device demonstrates its large potential in self-consumption improvement and in grid stabilisation. The optimal supercapacitor size configuration is determined by a technical assessment. The evaluated results show that by adding small but fast-response energy storage, self-consumption can be increased as much as 83% and 114% for a sunny and partly cloudy day, respectively, in reference to the system without any local energy storage and the yearly averaged self-consumption increase for the presented load exceeds 100%. The additional benefit is grid fluctuation decrease which is found to be a significant problem in the near future and the reason for the possible penalties for poor energy quality dispatch to the grid. In this work the issue related to the analysis uncertainty due to the load temporal resolution is also presented.