Development of an analytical solution for optimum design of RWH systems—A case study in Guangzhou.

The implementation of rainwater harvesting (RWH) has emerged as a key strategy to cope with the water crisis in urban areas. However, the required design parameters of the RWH system in different buildings vary widely because of the differences in architectural characteristics. In this paper, the relationships between the building characteristics parameters and the optimal tank (Tc) capacity are investigated by simulating the RWH system for more than 120 buildings at different locations in Guangzhou. Explicit expressions relating the optimal storage volume of RWH systems to building characteristics are derived based on nonlinear regression analysis. A set of bivariate exponential equations for estimating the optimal tank size under different building conditions was obtained. The model has a MER of less than 10% for buildings with a C/D ratio between 17.5 and 85. In Guangzhou, the unit cost of an RWH system can be reduced to CNY 2.62/m2 with optimally designed tanks. Highlight: A generalization equation is proposed to assist in the design of cisterns for RWH systems.The validity range of the equation is verified.The derived analytical equation is adequate to determine the cistern volume for medium‐sized buildings. [ABSTRACT FROM AUTHOR]