A water coolant loop is usually part of the thermal control system for manned spacecraft. The water loop then interfaces with a Freon or ammonia loop to reject heat to the heat sink systems. A simpler approach would be to design the water coolant heat exchangers to be freeze tolerant and utilize the phase change of water to ice as part of the thermal control system. This would eliminate the need for a second heavier fluid loop using Freon or ammonia (heavier because these fluids are poorer heat transfer media). Further, a water/ice heat exchanger can use the buildup of ice to self-regulate heat transport from the spacecraft to space. This approach to thermal control will result in a safer and more reliable system. In spacesuits, a freeze tolerant heat exchanger/radiator system will dramatically reduce (by roughly 75%) the single largest consumable during EVA. A spacesuit radiator can replace the PLSS covering with very little net increase in weight and yet will cut the amount of water needed to cool the astronaut during an EVA by up to 6 lbs. This will represent a significant cost savings to future missions and especially in Lunar and Mars EVA missions where the reduction in water loss is not merely nice, it is essential.
The largest and nearest term commercial applications are the use of freeze tolerant tubing on earth. These earth-based applications include sprinkler systems and potable water supply in homes and commercial buildings. This market is potentially very large and virtually un-tapped because of the lack of a viable freeze tolerant tube. The Insurance Institute for Property Loss Reduction says frozen pipes have cost the insurance companies in the USA $4 billion in damage to insured homes and buildings over the past decade (i.e., about $400,000,000 per year). The savings in insurance rates alone could more than offset the cost to the user, who would have the added benefit of not having valuables destroyed by water damage and their lives disturbed during repairs of the water damage.