Solar cooling system keeps water at 9 degrees Celsius for up to three months

The prototype developed in the Research Department in Zeolites, at the Institute of Science of the Meritorious University of Puebla (BUAP), in center Mexico, works 24 hours and keeps the cold for up to three months.

The researcher developed the prototype in the Black Mountain Range of the state, where she has achieve to maintain water at nine degrees Celsius "with that temperature we can cool food, though the goal is to get as low as five, with this fish can be preserved without denaturing its proteins."

The BUAP design is inexpensive, easy to manufacture and environmentally beneficial. "Normal cooling systems use chlorofluorocarbon chemicals that destroy the ozone layer and contribute to greenhouse gases, ours is friendly to the environment," explains Toledo Flores.

It works with solar radiation and the cooling is achieved by means of a thermodynamic adsorption-desorption cycle lasting 24 hours. Methanol is used as a refrigerant and as zeolite (mineral) as an adsorbent.

Toledo Flores says the system has two stages, during the day "warming, desorption and the period of condensation happens. Solar energy heats the zeolite and increases the methanol vapor pressure, the refrigerant is condensed and stored in a tank flowing to the evaporator. "

Overnight the cooling process is achieved, adsorption and evaporation period is performed. "The adsorbent bed temperature decreases after sunset, therefore, the refrigerant pressure is reduced and evaporates while the absorbent is cooled. During this period the coolant begins to evaporate and is again adsorbed by zeolite generating cooling temperatures of five degrees Celsius. The adsorption process continues all night until morning. "

The equipment is composed of a solar collector, adsorbent bed, condenser and evaporator. To build it, the researcher calculates the amount of water to be cooled, thereby knows how many zeolite to use. She also considers the room temperature, in this case of 20 degrees Celsius.

Furthermore, the system "is not only designed to cool foods. It may also serve as an air conditioning, for example, in communities like Tecali de Herrera, Puebla, where there are areas without electricity and the system could adapt well to preserve their foods and medicine, bringing them better quality of life," says Toledo Flores.

The project was presented at the International Congress of Solar Energy at Germany.