The humble air compressor is a staple of the modern workshop, underpinning everything from tire inflation to air tools, factory equipment, research gear and paint sprayers. But there’s always a better way to do things, and one California company believes it’s come up with a design that cuts down markedly on noise, lasts longer, manages heat better and drops the total cost of ownership as much as 20 percent while using no oil.
The Carnot compressor uses a strange centrifugal process to vastly cut down the number of moving parts in the device. It’s inspired, the team tells me, by a sixteenth-century device called a trompe, which used the force and weight of falling water, suffused with air bubbles, to compress the air and force it through a pipe with no moving parts whatsoever. These were commonly used in mining, as well as being a signature element of forges in Catalonia.
A trompe needs to be huge to create any real pressure, though – one built at Ragged Chute, Ontario, uses a 345-foot (105-meter) drop to create just 128 psi, so the Carnot team looked to another way of accelerating bubbly water to achieve the same effect, and arrived at a centrifuge.
So, the Carnot compressor sucks in air through a filter at the top, and mixes it with water at the top of a fast-spinning drum. The faster you spin it, the heavier the water gets, much like swinging a bucket of water around your head. Thus, the water squashes and compresses the air, and the mixture is forced out the bottom, getting separated into compressed air and water as it passes through the exit channels.
The compressed air goes into a tank as per usual. The water, which through this process absorbs much of the heat of compression, is then fed through a heat exchanger, which cools the water, radiates the heat out, and feeds the cool water back into the drum. Job done. The only moving parts are the spinning drum, powered by a relatively quiet electric motor, and any exhaust fan you might need on the radiator, if you need one at all.
Indeed this exhaust fan, says Carnot Compression CEO Todd Thompson, is the noisiest part of the whole device, as the compressor drum itself spins very quietly in the device: “For a commercial design with the proper enclosure and fan arrangement, the system will be able to operate indoors at below 70 dB.”
Carnot has a prototype, a fully integrated machine being developed and tested in Reno that Thompson says was funded by a grant from the California Energy Commission. The company initially plans to release a product in the 10-20 horsepower range, but it’ll easily scale for applications over 100 horsepower as the technology matures. “We also see the potential to compress different gases than air,” says Thompson.
On top of using significantly less energy and lasting longer than a traditional piston-forced air compressor, Carnot says the fact that this design uses no oil has benefits of its own, as it ensures no oil contamination in the airstream, which is critical in some manufacturing, research, painting, food and beverage use cases where air purity is a big deal.
Carnot is still in the development stage and seeking investors to take this technology to a market expected to be worth around US$40+ billion by 2025. An interesting and promising technology.
Carnot puts a centrifugal spin on a 500-year-old air compressor design [New Atlas]