ICEPHOBIC HEAT EXCHANGE FOR EFFICIENT, RESILIENT BUILDING COOLING

Space cooling in buildings or “air conditioning” presents a big challenge for a sustainable future: the International Energy Agency’s Future of Cooling reports that a fifth of all electricity used in buildings is for cooling, and that worldwide cooling demand will triple by 2050. But space cooling offers an even bigger opportunity: this demand can be harnessed, made dynamic and flexible with thermal energy storage, to enable greater penetration of intermittent renewable power sources like wind and solar. Lowtemperature storage provides the cobenefit of backup cooling during emergencies. Unfortunately, today’s ice storage technology is too expensive and inefficient for widespread adoption. Icephobic heat exchange technology, which eliminates adhesion between freezing water and cold surfaces, enables ice storage to reach its potential. This SBIR project’s objective is to use icephobic heat exchange technology to increase the round trip energy efficiency of ice thermal storage to >90% a ~15% improvement compared to today’s iceoncoil technology and develop storage systems that can deliver a day’s worth of backup cooling, while generating enough cost savings to pay for themselves within 30 months. During Phase I, proof of concept for this energy efficiency increase was shown by operating an icephobic system 9°F warmer than iceoncoil systems with 4X the heat transfer coefficient. Warmer operating conditions and higher cooling rates result in more efficient refrigeration systems and lower cost storage. New icephobic storage systems were designed to capture this benefit. Designs were evaluated for their economic and resiliency benefit by simulating their performance over a year during both normal and emergency conditions, and several configurations provided 12 hours of resilient cooling with <30 month payback periods. Phase II will build on this momentum to create commercialscale IHEXenabled ice thermal storage systems that meet the 15% energy efficiency enhancement, offer payback periods of less than 30 months, and provide a day’s worth of backup cooling. A modelbased predictive controller will be developed to optimally balance operational cost savings with resiliency constraints. The National Renewable Energy Laboratory NREL and our commercialization partners will work with us to showcase the system’s performance. Lowcost, efficient ice thermal energy storage, enabled by icephobic heat exchange, will help change the relationship between buildings and the grid. Instead of acting as a passive recipient, the building will modulate its power consumption based on price signals from the utility. This grid interactive building will deliver the same thermal comfort, while lowering energy costs for the operator. And if power goes out, this resilient storage system will continue delivering cooling. The power grid—stressed by age and electrification—could use support from buildings to maintain reliability. Icephobic thermal energy storage helps meet this need.