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Ice-storage and Other Thermal Storage-related Systems (CABLE)


d.      Ice-storage and Other Thermal Storage-related Systems (CABLE)

This subtopic solicits proposals for high performance (efficient and cost-effective) ice-based thermal storage technologies that leverage CABLE enhanced thermal conductivity materials.


The water-ice phase change is attractive for thermal (cold) energy storage because of its large heat of fusion resulting in high energy density, low cost, near constant storage temperature (melt temperature) along with minimal environmental impact. Applications of ice storage include heating, ventilation, and air-conditioning (HVAC) and refrigeration technologies, including direct expansion and chilled water, load balancing, integrating renewable energy sources into the grid, etc.


During ice storage charging, a heat transfer fluid at a lower temperature is used to form ice, and during discharging, the process is reversed and ice melts into water and the heat transfer fluid is cooled down. The challenge with ice storage is that ice is a relatively poor thermal conductor. Thus, as ice is formed it becomes kinetically prohibitive to form more ice, limiting the total amount of stored energy over a fixed period. Typically, extensive piping is used to increase the total energy stored. Moreover, this approach leads to increased overall footprint and cost of the storage systems often making them marginally- or non-economical.


This subtopic therefore will support proposals that look to overcome these issues associated with thermal energy storage through new materials and thermal control approaches. This subtopic is interested in both passive and active approaches such as novel materials, high conductivity reinforcements, tunable conductivity, and use of external stimuli to control thermal conductivity.


Key metrics for such technologies are shown in the table below. The first row highlights one of the most important areas needing improvement: the time it takes or the rate at which the storage systems are charged and discharged. Applications must demonstrate progress in Phase I and achievement in Phase II of the following performance and cost targets.


High Performance Ice Storage Systems



Performance (charging/discharging rate)

>200% over current state of the art systems

Energy storage density (kWh/m3)


Round Trip Efficiency (%)



>50% reduction from the current state of the art ice storage systems


Similar or better than current state -of-the-art ice storage systems

Energy Storage System Cost ($/kWh)



Please refer to Topic 12 (BTO) for other opportunities related to Building technologies.


Questions – Contact: Fredericka Brown, Building Technologies Office,


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