Optimal sizing of storage tanks for domestic rainwater harvesting in Sicily

In this paper, a dimensionless methodology for the optimal design of domestic rainwater harvesting systems (DRWH) is presented. The methodology is based on the results of daily water balance simulations carried out for 17 rainfall gauging stations in Sicily (Italy). A novel dimensionless parameter to describe the intra-annual rainfall patterns is introduced and easy-to- use regional regressive models are developed to estimate water savings and overflows from harvesting systems in the region. A minimum-cost-based approach together with obtained regressive models is used to evaluate the optimal DRWH tank size. Results of the approach point out that the economical convenience of large tanks decreases as rainwater availability decreases.