Zeolite Refrigerants.

Claude Blaizat is a French inventor who has patented the use of zeolites in the transfer of heat using the evaporation and condensation of water in a closed vacuum-system. I have discussed zeolites previously in their application as ion-exchange materials for cleaning toxic metal cations from the environment. For example half a million tonnes of zeolites were used in the clean-up operation after the disaster at Chernobyl in 1986, mainly to remove radioactive strontium and caesium from contaminated land and water supplies. Zeolites were fed to cows to keep the radioactive contamination out of their milk, and even baked into bread and cookies to remove similar contamination from the bodies of children. It is the presence of cations, which are strongly hydrated by water, that provides the basis of the zeolite-cooling system. In its simplest form, water is placed at one end of the apparatus the the dried zeolite at the other. The whole is pumped-out under vacuum which encourages the water to evaporate, so taking heat from its surroundings and providing cooling. The water vapour is adsorbed into the zeolite, which causes heating. Because the heat of hydration of the cations is greater than the heat of condensation of liquid water, around twice the amount of heat is generated by using the zeolite. Such systems can be combined with a solar collector, so that during the day, water is driven out of the zeolite by the heat from the Sun's rays, and at night heat is provided by evaporation and re-adsorption of water into the zeolite. The principle can be incorporated into a heating-system.
It is reported that the technology has been demonstrated in the food industry, for quick evaporative cooling of fresh and cooked products resulting in freezing with a minimum effect of the quality of the food, and also blanching, cooking and cooling fruits and vegetables without any production of wastewater and also for freeze-drying food. Large refrigerated containers have also been demonstrated of up to 10,000 gallons capacity that do not require energy to keep their cargo cool, just so long as there is water in the system to be evaporated and the zeolite is not saturated with water. A heat-pump that could draw its energy either from a renewable source like biomass or from the exhaust gas of an engine has also been demonstrated. In the latter example, cold water can be provided in an air-conditioning unit for truck or train cabs or even for drinking.
Writing in "Chemical and Engineering News" Jean-Paul Vignal commented: "That this technology has never been industrially developed puzzles me. Maybe the price of oil is still way too low and the greenhouse effect way too unproven? The Department of Energy and the Natural Resources Ecology lab. told me that the matter had been extensively investigated and that it would never work. I have seen it work well and maintain a 22-foot container between 0 and 3 deg. C for several days without wires or an onboard generator."
If true the latter does sound like an amazing device, but even as applied on the smaller scale of a solar-powered adsorption cooling tube, 4 kg of water can be heated to about 50 deg. C in daytime and to about 39 deg. C at night while also producing a refrigeration capacity of about 276 kJ. This amounts to a heating power of around 5 kW... and all for free in terms of energy input! Combined with the waste heat from the exhaust of an engine, water at 8 - 12 deg. C can be provided for the fan-coil in a locomotive operator cabin, and 10 kW might thus be achieved.