Engine Driven Air Conditioners
The world of HVAC is a very strange place to live some days. We commonly think of air conditioners as being electrical devices. Perhaps the only real exception to that is the air conditioner in your car, which is essentially powered by your car’s engine. In the early days of air conditioning and refrigeration however, the opposite was true: cooling systems were mainly mechanically powered.
The World Before Electricity
It’s the early 1900s. The telephone is still considered cutting-edge technology and you can go down to the local train station to send a telegram anywhere in the country. Electricity however, was not quite so common. In 1900, 3% of US homes had electricity. It wasn’t entirely feasible to just throw an air conditioner in your back room. Even businesses wouldn’t have had the easy option of just plugging in an air conditioning system, even if it occupied half their building.
At this point, most working-power was mechanical. Factories would have massive boilers, which produced steam, that turned enormous turbines or ran crank systems, that ultimately ran everything in the facility. In order for any particular innovation to take off, it almost had to be mechanically driven. If you couldn’t throw some coal and water in a machine to power it, you probably couldn’t have it.
Steam Powered AC
How exactly do we run an air conditioner on steam alone? Every motor in an air conditioner is doing just one thing: spinning. We spin a shaft in the compressor and we spin fan blades. This means we can use any spinning thing, be it electricity or a steam engine to crank an air conditioner. Early air conditioners could be powered by a wide array of equipment. Some systems were run from steam engines that powered entire buildings, others ran on propane.
The US Navy took this approach in the 1920s. Willis Carrier designed a system to be installed in the engine room of the USS Arkansas. It would ultimately be installed in the sister ship USS Wyoming instead in 1925. As near as we can tell, these systems would have been powered by the onboard steam before more powerful electric motors became viable. In many applications, particularly naval ones, space is at a premium. They could use electrical systems, but that might mean a bigger electrical generator and more space for electric motors. It was essential to simply use the most direct means of powering the system.
This carried over to early train air conditioning systems as well. They often use the wheels of the cars themselves to power the compressors and fans. Gears could be attached to the wheels or an additional wheel could be placed down from the compressor, which would drive the entire system through gears and chains as the train moved. There was the downside that the second the train stopped, so too did the air conditioning.
Use What You Have
These engine-driven air conditioners persist today. We don’t so much use steam to power air conditioners any more, but we do use direct power from motors. The belt in your car powers a compressor. In many small boats and yachts, the engine directly powers a compressor. In systems where we generate electricity to then power an electric motor, there’s a lot of waste in the back and forth between electricity and compressor motion. In places where space and efficiency matter, we drive the compressor as directly as possible.