Simultaneous design and control optimisation of combined rainwater harvesting and flood mitigation systems

The design and operational parameters of large-scale rainwater harvesting (RWH) systems should be optimised for its local environment to maximise their efficiency. This paper looks to address the barriers in RWH system performances when their design and operational strategies are optimised separately. This is achieved using a framework which identifies a set of candidate optimal designs with their corresponding optimal control policies by optimising each possible combination of control policy and actuator location. The globally optimal configuration is then determined using a high-resolution simulation model that evaluates their performance under a wide range of historically observed rainfall profiles. When implemented for a RWH system in a tropical city, the optimal configuration was found to improve harvested water yields by 15%–27% in comparison to when only its design is optimised. The 15% improvement is also achieved with a 25% reduction in capacity, reducing spatial competition with other key utilities for the estate.