Technical model for optimising PV/diesel/battery hybrid power systems

Abstract

A solar-based power supply system, such as a photovoltaic (PV)-diesel-battery system, is a particularly attractive option for decentralised power supply in southern Africa where solar radiation is ubiquitous in most countries. Such systems can make a positive contribution to the sustainability of rural communities in developing countries that do not have access to an electricity grid as they address the shortfalls of stand-alone systems. However, a lot more design effort and expertise is required for optimising the sizing and operational strategy of the PV-diesel-battery hybrid system than is required for single-source systems. Various models are available on the market and in research groups but the challenge is to customise these to suit local conditions. This paper presents the development and application of a simple spreadsheet-based mathematical model for sizing and performance prediction of a PV-diesel-battery autonomous power supply system. The model is employed to generate a set of sizing curves that define the design space for hybrid systems using dimensionless component size variables, for a specified supply reliability and diesel energy dispatch strategy. The outputs of the model reveal several important sizing and operational characteristics of the systems