Photos: University of Santa Maria.
Even if each time the words ‘solar refrigerator’ come in the news it sounds like a groundbreaking story, truth is the idea of using heat to create cold is pretty old. A French inventor came up with a concept to do this as far back as 1858, there are records that show a machine prototype from 1935, and the concept of evaporative cooling has been widely explored, as Lloyd notes in a previous article.
However, it’s always interesting to see new prototypes. This one comes from South America and is based on adsorption, using methane as gas and active carbon as the absorbent solid material. Get the details and larger pics in the extended.Details of the Solar Refrigerator Prototype from Chile
The fridge was developed by mechanic engineering students Frederik Knop, Nicolás Ripoll, and Olivier Bernade, the last one a French exchange student.
The prototype is based on adsorption, which Wikipedia explains in the following way:
Absorptive refrigeration uses a source of heat to provide the energy needed to drive the cooling process.[...] The classic gas absorption refrigerator sends liquid ammonia into a hydrogen gas. The liquid ammonia evaporates in the presence of hydrogen gas, providing the cooling. The now-gaseous ammonia is sent into a container holding water, which absorbs the ammonia. The water-ammonia solution is then directed past a heater, which boils ammonia gas out of the water-ammonia solution. The ammonia gas is then condensed into a liquid. The liquid ammonia is then sent back through the hydrogen gas, completing the cycle.
The principle of adsorption cooling was invented in 1858 by a French scientist called Ferdinand Carré. Some prototypes that don't work with heat coming from the sun but induced have been invented and sold commercially: a crazy model called The Icyball, other industrial ones from Lehman's, and even some recreational vehicles have refrigerators based in this principle. Venture capitalist Adam Grosser even presented a project to build a heat-based small refrigerator for poor regions at TED 2007.
So what's the difference in the Chilean model? First of all, the heat, which comes from the sun. Second: the choice of substances for the process.
Most of these models (except the one from Grosser) use ammonia as gas, which can create too much pressure if heated up and can be dangerous if leaked. The Chilean prototype uses methane as gas and active carbon as absorbent. While production of active carbon is a very energy intensive process, methane is highly biodegradable if spilled and less inflammable (although it can be toxic if ingested or in contact with eyes).
So the way it works (in a simplified way) is: after attaching the methane to the active carbon, this substance absorbs the sun’s heat and creates methane vapor that then condensates into licuated methane, expelling heat in the process. Then the carbon absorbs the methane and the cycle begins again. In short, the heat that comes from one side activates a process which removes heat from the other side, cooling it.
We're not calling this new or one of a kind, but I couldn't find any prototypes with these characteristics. I did found records about an investigation to produce a fridge like this, but not the implementation of it. Of course if any of you readers know another model feel free to share in the comments.
The fridge is just a prototype so far, but the students are hoping to find development support as they think it could be benefitial for rural areas with strong radiation.
For more information, contact the University of Santa Maria in Chile.
More on Solar Cooling:
Wayback Machine: Solar Powered Refrigerator (in 1935!)
Solar Powered Refrigerator Could Bring Health and Energy Savings to Rural India
Solar Powered Air Conditioning Just Makes Sense