Icephobic Heat Exchange for Efficient, Resilient Building Cooling

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.