Absorption cooling for soldier drinking water.

Creare engineers have developed a novel form of refrigeration that is lightweight, compact and can be used in virtually any environment—from the searing heat of deserts to the challenge of cooling in deep space—with minimal power requirements. The regenerable heat absorber (RHA) system stores the energy in chemical form (as concentrated lithium chloride (LiCl) salt solution) until it is needed to trigger refrigeration. This concept can also be used to advance lifesaving and health-enhancing technologies for a variety of applications.

Creare initially developed this refrigeration technology for NASA as a cooling system for spacesuits. NASA has need of a lightweight system that does not vent water for its future extra-vehicular activity (EVA) missions. The Creare RHA cooling system uses water as a refrigerant and LiCl as an absorber. The water evaporates to remove metabolic heat and the LiCl solution absorbs the water vapor. Because LiCl solution has a very low water vapor pressure and the absorber radiates heat at a much higher temperature than the water evaporation temperature, the system functions as a heat pump. After use, the system is regenerated thermally by heating the absorber and recondensing the water into the evaporator. We built and tested a prototype absorber and evaporator and demonstrated excellent thermal performance in our laboratory. If integrated with a spacesuit, we expect that the cooling system would weigh less than 9 kg and provide 1000 W-hr of cooling for the astronaut. Compared to existing spacesuits, Creare’s design saves 2.4 kg of water for each four-hour EVA.

Back on earth, medical journals have reported recently on the effectiveness of mild therapeutic hypothermia for the victims of heart attack and stroke. Patients who have their core body temperature lowered by 4º C show dramatically improved neurological outcomes. Currently, 10 to 30 percent of cardiac arrest survivors (outside the hospital setting) later die from anoxic brain injury. Many others suffer long-term neurological problems ranging from subtle to profound disability.

Using our RHA technology, we have developed a compact, portable refrigeration unit that can be stored for long periods of time in ambulances, fire trucks, or police cars and used by paramedics and first responders when rendering first-aid. Water is chilled in a regenerable heat absorber and circulated through cooling pads that can be easily wrapped around the head, neck, torso, and limbs. The system requires only 5W for a small fan and a water circulation pump, which can easily be supplied by a small battery.

We’ve also used RHA technology to design and demonstrate a compact, lightweight water cooler for soldiers in hot environments. Our Individual Cooling Element (ICE) requires no electricity and quickly cools one liter of drinking water by 20º F, encouraging consumption and maintaining healthy levels of hydration. The warm water flows from the soldier’s hydration pouch through the ICE, emerging as chilled water. Both the absorber and the evaporator, as well as a heat sink, are made of flexible, lightweight materials, and are rolled up into a compact package that weighs less than 6 ounces.

The market potential for technology that provides cooling without bulk or excessive power requirements is significant. We foresee applications such as cooling units incorporated into protective firefighting gear, medical applications for transporting medicines into remote geographical areas, and also recreational uses such as camping and boating, where size and duration of independent operation are essential.

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