Building-integrated solar water disinfection system for reliable year-round drinking water safety

Waterborne pathogens pose a major threat to global water safety. Solar energy could provide a critical opportunity for households without reliable access to safe water; however, many solar-driven household water treatment systems (HWTS) fail to provide adequate year-round quantities of clean drinking water, as they often cannot remove viruses during low-sun periods, exposing users to waterborne diseases. We demonstrate the disinfection capacity of a novel concentrating solar water-energy management system for building envelopes that integrates on-site water collection with phyto-derived photosensitization, solar water disinfection (SODIS), and solar pasteurization (SOPAS) within a roofing system suitable for a range of housing types. By combining outdoor testing in field settings with computational modeling, we demonstrate the water treatment capacity as a function of the year-round variations in solar resources available in different climates: Cape Town, South Africa; Sololá, Guatemala; and Phoenix, AZ, USA. Modeled annual performance across each site indicates that the approach could treat more than 70 L/m2 per day of potable water, guaranteeing the United Nations (UN) minimum of 15 L per person per day, year-round. The integrated systemic approach reduces viral treatment times by up to two orders of magnitude compared to conventional SODIS, thereby achieving adequate daily water production rates that meet household needs, even in low solar periods. The building-integrated solar system combines water heating and disinfection, supplying up to 94% of domestic hot water demand, thereby reducing household energy costs and resource insecurity.