A water and greenhouse gas inventory for hygroscopic and conventional evaporative building-scale cooling systems
Freshwater scarcity is a major threat to the resilience of our society, and the challenges are only being exacerbated by the worsening impacts of climate change. The U.S. Department of Defense's Environmental Security Technology Certification Program demonstrated a novel heating, ventilation, and air conditioning (HVAC) cooling tower technology with the goal of reducing water usage. In this study, direct and indirect water usage and greenhouse gas emissions were quantified to analyze the tradeoffs associated with transitioning from a conventional wet-cooling HVAC tower to a novel hygroscopic system. Greenhouse gas emissions (GHG) were quantified for direct electricity consumption and the energy associated with water and wastewater conveyance and treatment using power plant and cooling system data, municipal water treatment data for California, and fuel-type emissions factors. Water usage was estimated using power plant data and cooling water factors from literature and the U.S. Energy Information Administration. It was found that the impact of increased electricity is greater than the indirect energy savings from the decrease in water usage, resulting in a net increase in GHG emissions. The indirect water consumption associated with cooling water for electricity generation is comparatively low when compared to the volume of direct water usage that is reduced by switching from conventional wet cooling to the hygroscopic system. The hygroscopic cooling technology shows promising water savings ability that will be more feasible in regions with extreme water scarcity, high water sourcing and treatment energy intensity, and/or when the electricity is sourced from low-carbon sources.
energy-water nexus, water, energy, greenhouse gas, GHG, greenhouse gas inventory, life-cycle assessment, cooling tower, HVAC, cooling water, water consumption, water withdrawal, electric generation, power plant, hygroscopic, hygroscopic cooling tower, blowdown, California
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign