CH-15-C023 -- Estimating Water Savings from an Auxiliary Water Collection System as Part of an Integrated Thermal Energy and Water Storage System for Residential Buildings

This paper provides an overview of rainwater, graywater, and AC condensate collection (collectively referred to as auxiliary water) using a model of integrated systems in residential buildings. The model incorporates basic house geometry and characteristics, local meteorological data, and consumption information to estimate the potential for water collection. The model is then used to calculate the water savings from the collection system(s) for a range of configurations. A single family residential building in Austin, Texas and 2011 historical weather data was used as an example to illustrate the model’s capabilities. This analysis was limited to analyzing water consumption and savings from irrigation only. The analysis estimated significant annual water savings (74%) with a storage tank size of 1,500 gallons (5,678 L). For tank sizes larger than 1,500 gallons, the savings had diminishing returns, with a 12,000 gallon (45,425 L) tank needed to meet the annual irrigation demand.