Developing An Approach To Optimise Rainwater Tank Size and Efficiency

Abstract

Domestic rainwater harvesting is increasingly being used in households in urban areas to reduce dependence on mains water and also to mitigate the adverse impacts of increased stormwater runoff due to urbanisation. Most of the literature on rainwater harvesting looks into the installation and use of rainwater tanks by individual households. In recent years, communal rainwater harvesting has also gained popularity as another alternative for water supply. Some of the critical factors that have to be taken into consideration when installing rainwater tanks include roof size, non-potable household water demand, the estimated rainfall in the area, cost of tank (i.e. installation and maintenance costs) and the required level of reliability. Can the size of rainwater tanks be optimised to be more cost-efficient while meeting household demand? This is the focus of this research. The effect of communal rainwater tank (i.e. multiple households using the same rainwater tank), on cost, tank sizing and the ability to cater to water demand are also examined. The possibility of making the process of communal domestic rainwater harvesting system more robust and sustainable by reducing wastage of stored rainwater and reducing the need for larger rainwater tanks has also been studied. An optimisation tool has been developed during the course of this investigation that is able to optimise individual, dual and communal rainwater tank systems based on cost, while meeting the target reliability in household water demand. The performance of this optimisation tool has been further tested using seasonal demand and different rainfall inputs, and the tool is able to optimise rainwater tank size for the scenarios presented, except for extremely dry weather conditions. The functionality of the developed optimisation tool can be extended beyond what is currently in its configuration, and this has been outlined in the future work section.