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Solar cooling system keeps water at 9°C for up to three months

02 April 2015

A Mexican researcher has developed an inexpensive solar cooling system based on a 24-hour thermodynamic adsorption-desorption cycle.

Susana Elvia Toledo Flores with her prototype solar cooling system

The prototype, developed by researcher, Susana Elvia Toledo Flores of the Research Department in Zeolites, at the Institute of Science of the Meritorious University of Puebla (BUAP) in central Mexico, works on a 24 hour cycle and maintains a steady temperature of 9°C for up to three months.

"At that temperature we can cool food, though the goal is to get as low as five; at this temperature, fish can be preserved without denaturing its proteins," she says.

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," says Toledo Flores.

Cooling is achieved by means of a 24-hour thermodynamic adsorption-desorption cycle. Methanol is used as a refrigerant and zeolite as an adsorbent. The device, comprising a solar collector, adsorbent bed, condenser and evaporator, works on a two-stage process:

During the day warming, desorption and a period of condensation occurs. Solar energy heats the zeolite and increases the methanol vapour pressure; the refrigerant is condensed and stored in a tank connected to the evaporator.

Overnight, the cooling cycle is achieved during adsorption and evaporation. "The adsorbent bed temperature decreases after sunset, so the refrigerant pressure is reduced; it evaporates and the absorbent is cooled," Toledo Flores explains. During this night-time period the coolant evaporates and is adsorbed by the zeolite, generating a cooling effect.

As well as keeping food and medicines cool, Toledo Flores believes her system could also be used as an air conditioner for off-grid communities in warm climates.


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