A simulation of rainwater harvesting design and demand-side controls for large hospitals

Abstract

Inpatient health buildings in the United States are the most intensive users of water among large commercial buildings. Large facilities (greater than 1 million square feet) consume an average of 90 million gallons per building per year. The distribution and treatment of water imposes a significant electrical power demand, which may be the single largest energy requirement for various states. Supply and demand-side solutions are needed, particularly in arid and semi-arid regions where water is scarce. This study uses continuous simulations based on 71 years of historical data to estimate how rainwater harvesting systems and demand-side interventions (e.g., low-flow devices, xeriscaping) would offset the demand for externally-provided water sources in a semi-arid region. Simulations from time series models are used to generate alternative rainfall models to account for potential non-stationarity and volatility. Results demonstrate that hospital external water consumption might be reduced by approximately 25% using conservative assumptions and depending on the design of experiment parameters associated with rainfall capture area, building size, holding tank specifications, and conservation efforts.