Farming Secure Water: Building-integrated Solar Water Disinfection using Agricultural Plant Dyes | 2023

Location: West-Vlaanderen, Belgium
Architects: Mandi Pretorius and Anna Dyson, Yale Center for Ecosystems + Architecture, Yale School of Architecture, Yale University, New Haven, Connecticut, USA
Client: Yale Center for Ecosystems + Architecture, Yale School of Architecture, Yale University, New Haven, Connecticut, USA
Photographers: Yale CEA

FARMING SECURE WATER addresses the problem of guaranteeing year-round safe drinking water through solar disinfection by combining plant-based photochemistry to bolster the action of the sun, reducing the time to disinfect viruses from 30 hours to 10 minutes, thereby rendering solar water disinfection accessible and viable for low-income households around the world.

By 2050, approximately a third of the global population will live in informal settlements. Over 40% will live in water-stressed regions, where decentralized water management will be vital. Overcoming unsafe, inaccessible water resources requires a distributed approach to meet Water-Energy-Food Nexus needs across disparate households. Yale Center for Ecosystems + Architecture (CEA) investigates novel plant-based Solar Water Disinfection (SODIS) techniques integrated into building façades and roofs to expand on-site, renewable water recuperation. FARMING SECURE WATER demonstrates a low-cost approach to strategically integrating on-site water treatment in informal to middle-income housing. This novel approach embeds synergistic solar water treatment mechanisms into a building-integrated solar collector, enhancing year-round water treatment by capturing and concentrating solar energy for disinfection, heating, and daylighting. FARMING SECURE WATER addresses cost, efficacy, and adoption limitations for domestic-scale point-of-use water treatment, making it viable for various building types, climates, and vulnerable demographics, including low-income households.

A Building-Integrated Approach to Resource Access and Affordability
FARMING SECURE WATER can be adopted by various actors, from informal homebuilders to housing authorities, as an affordable, scalable, building-integrated system for on-site water security. To enhance adoption across contexts, the system integrates novel design criteria into widely accepted low-cost roofing assemblies, modifying its geometry to incorporate solar concentrating optics while maintaining key elements for systemic deployment. The glazed roofing system converts solar energy for water treatment, heating, and power while shielding components and enclosing interiors using a lightweight assembly with selectively programmed surface and material behaviors.

Ensuring Year-Round Drinking Water Quality
To reduce dependence on costly input energy and materials that limit household water treatment adoption, FARMING SECURE WATER integrates solar pasteurization (SOPAS), solar disinfection (SODIS), and photosensitization, maximizing available solar energy for disinfection and domestic water heating. The system incorporates common locally-grown photosensitizing plant dyes, which react under visible-spectrum sunlight to inactivate >99.99% of viruses within minutes and provide a visual indication and assurance to vulnerable communities in changing pink-to-clear that the water is safe to drink. Results suggest that the multimodal approach can treat a median of 60-90 L/m2 per day, guaranteeing the UN minimum of 15 L-pp-d to ensure water safety year-round, regardless of climate or seasonal variation.

Improving Household Energy Security:
FARMING SECURE WATER delivers up to 95% of annual domestic hot water across regions within ±35° latitude, thereby reducing between 20-60% of household energy bills and dependence on unreliable municipal utilities. FARMING SECURE WATER reduces glare, permitting large fenestration areas and adequate cool daylighting while minimizing artificial lighting bills. We will test this approach to transforming distributed water systems within an Ecological Living Module for COP30 in Brazil, a collaboration between Yale CEA and the UN Environmental Program exploring the Water-Energy-Food-Air Quality Nexus in housing.