Category Archives: Heat Pumps

Evaporative Refrigerator

Evaporative Refrigerator

A group of students from the University of Calgary have developed a simple evaporative refrigerator. It was inspired by the way that animals and insects keep themselves cool.

Warm air from the surroundings is funneled into a pipe network to evaporate water moisture, which carries heat away from the air. Once the air is cooled, it moves into the chamber where the food is kept. The only power requirement to bring the temperature down to 4C is to power a small fan to move this cool air, which can be done with a very small battery setup powered by a small solar panel.  The refrigerator still works with no electricity but works best with the fan.

To learn more, go here: http://challenge.biomimicry.org/en/custom/gallery/view/2576

Silent Refrigeration

A refrigerator uses a traditional heat pump. A compressor is powered usually by electricity and that circulates a “refrigerant” like freon or some synthetic version through some tubes that go through heat exchangers – the bottom line is that is pulls the heat out of the fridge to make it cold.

An AC is just another variation of this as is all other heat pump technologies such as heat pump hot water heaters. Some give you cold while expelling the heat and some give you heat while expelling the cold.

Heat pumps are a really great technology and are very reliable and have made our lives much easier. There are a few drawbacks such as the noise and occasional maintenance due to moving parts.

Phononic is a company, which has eliminated these problems by building a completely silent and solid state refrigerator using hundred year old Peltier junctions…they’re semiconductors basically that get hot on one side and cold on the other.

Peltier’s definitely work but their drawback is that they are very inefficient…it takes a lot of watt hours to produce any substantial heating or cooling, but Phononic has scaled them up and have made them more efficient than ever. Normally, they’re under 10% efficient, but now they’re over 30%!

Phononic heat pump

Even at 30%, they can’t compete with heat pumps in terms of Coefficient of Performance (COP), but being that they are much smaller than normal compressor heat pumps and they’re silent, they do have their place.

While this advancement in Peltier technology isn’t going to get anyone off the grid, it is a very welcome improvement as a three times increase in efficiency in anything doesn’t happen every day.

To put that into perspective – the automobile engine was commonly under 20% efficient and the newest cars on the road today are lucky to achieve 30% efficiency – and that is over many, many decades of automotive advancements.

Go here for more of the story on Phononic: http://www.treehugger.com/clean-technology/your-refrigerator-running-soon-it-will-be-doing-doing-it-solid-state.html