OxiCool Air Conditioner Uses Plain Old Water as a Refrigerant

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Square silver OxiCool fridge unit with vent on top


Introduced at CES, this could be a very big deal.

It has always been counterintuitive, trying to explain how absorption fridges and coolers which run on propane or gas work. But they and almost every fridge or air conditioner work on the same principle: when a liquid turns into a gas (or ice changes to water) it absorbs heat. It's called latent heat or the heat of transformation. Most fridges and air conditioners use fluorinated gases; we have shown heat pumps that work with CO2 and propane as refrigerants; absorption units use ammonia that evaporates when heat is applied.

Closed Loop

One of the top innovations at CES 2020 was the HomeCool from OxiCool, a new air conditioning unit that uses water as the refrigerant. My first thought on seeing it was that it was probably just an evaporative cooler, but this is a very different thing, a form of adsorption cooler that may turn the air conditioning world upside down.

Patent drawing for refrigeration technique
Ravikant T. Barot Brandon K. Wilcox David Lee Martin /Public Domain

How OxiCool Works

OxiCool was developed and patented by Ravikant Barot, and the unit replaces all of those toxic chemicals with plain water. As best as I can understand it from reading the patents, water evaporates in a vacuum, changing state and absorbing heat, which provides the cooling action. The water molecules then are pumped over to the adsorbent chamber, filled with a desiccant, absorbing even more heat in the process. Then the cycle is reversed; heat is added and the water is returned to the condenser. One problem with water as a refrigerant is that if it freezes, it expands and can destroy the system; desiccants hold single molecules of water and cannot freeze. Does that make sense?

No other company or country has ever figured out how to use water as a refrigerant in a nonfreezing capacity until OxiCool invented and patented the technology. That inability to use water as a refrigerant, and inability to get around water’s huge expansion factor during phase change, is why the world has been forced to cool itself using chemicals that are helping to rapidly warm the planet to its breaking point. It is a clean technology using molecular sieves in vacuum-sealed units made from stainless steel.
Patent drawing truck configuration
OxiCool / Public Domain

It's all sealed in a box; just add heat at the right time at one end and it will cool at the other; Then you reverse and recharge the system. Because there is no compressor, it is quieter and uses less energy. And it can be really small; it was originally developed to keep truck cabs cool when drivers were resting so that they didn't have to idle their engines. This makes it interesting for Passive House designs that have really small heating and cooling loads, as well as tiny houses.

Oxicool diagram of air conditioning process

The Homecool unit introduced at CES is bigger in size and cooling capacity; one site lists it at 20,000 BTU/hr for a Gang of Four heat exchangers costing $10,000. For some reason, it is also integrated with motion detectors and it talks to Alexa. Barot also got his first patent on it in 2009 so it has been a long time coming.

I wish there was more technical data and history so we could determine if this was a real ready-for-market device or if it was just water vaporware. But if it works, it could be big.