SBIR-STTR Award

Aging infrastructure, climate change, severe weather—today’s facts of life pose a formidable challenge to the current and future building stock’s ability to maintain safety and comfort. By maintaining critical functions (e.g., space cooling) during power disruptions, resilient buildings improve quality of life for occupants. Ice thermal energy storage holds promise to increase the cooling resiliency of buildings, but its full potential is yet to be realized. Installed costs are high; energy efficiency is low; and its slow thermal response is poorly matched to immediately meet cooling load in the event of an outage. Icephobic heat exchange stops freezing water from sticking to cold surfaces and can unlock the potential of ice thermal storage. Advancing this technology through this SBIR program willmake ice thermal energy storage more cost effective, efficient, and capable of improving the resiliency of buildings. During Phase I, the icephobic heat exchanger design will be improved, allowing the system to directly use low-global-warming-potential refrigerant for ice making, which will result in a 15% energy efficiency improvement proof of concept (on a single heat exchanger plate). Further, a resilient cooling system that utilizes icephobic heat exchange will be designed. This system’s operation, during both normal and emergency events, will be modeled over the course of a year to show favorable resiliency and economics: twelve hours of sustained cooling with backup power and a payback of less than three years. Beyond Phase I, the icephobic heat exchange plates must be parallelized and packed into a single unit, and the energy efficiency improvement must be demonstrated at the system level. This icephobic thermal energy storage system will then be operated against building loads before, during, and after a power outage. Tests will evaluate the system’s ability to rapidly meet cooling load when power first goes down, sustain cooling output for the duration of the outage (with minimal electric power consumption), and recover from the outage (recondition any space that was left uncooled during the event). Low-cost, 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 efficiently deliver the same thermal comfort to its occupants, while lowering energy costs for the operator. And if power goes out, this resilient thermal storage system, with minimal assistance from backup power, 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.

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.