This Outdoor Air Conditioner Runs on Liquid Nitrogen

Propane-powered patio heaters suck. Treehugger has complained about them for years, with contributor Sami Grover calling them "absurd," asking the most obvious question about their existence: "If it's not warm enough to sit outside, why not move indoors?"

But as the world gets warmer and summers become unbearably hot, we face a new absurdity: patio air conditioners. Neither patio heaters nor patio air conditioners seem as absurd in the pandemic world, where many no longer want to move indoors.

Many so-called outdoor air conditioners are essentially evaporative coolers with big electric fans blowing across the water and exhausting cooler, moister air. The amount of coolth depends on the air moved, so a decent one will move over 5,000 cubic feet per minute of air and use 430 watts of electricity to run the fan. Since the air is more humid, it is less effective at cooling the person on the patio.

Now, an Israeli company has what appears to be a much better idea: an outdoor air conditioner you don't have to plug in. The Kenshō from Green Kenoko is filled with liquid nitrogen. CEO Tal Leizer told Israeli tech site NoCamels, "We have invented an outside air conditioner which doesn't need electricity. It creates its own energy. We use liquid nitrogen at minus 196 degrees. When it turns into a gas it creates a very strong pressure and we use that pressure to activate a mechanical engine."

Indeed, it is a very strong pressure, with nitrogen having a liquid-to-gas ratio of 1:694 at 68 degrees Fahrenheit. This is clever. We can only assume they use the evaporating liquid nitrogen to create pressure which drives fans, delivering nitrogen-cooled air. (Treehugger reached out to the company and has not heard back.)

“We are now calculating the carbon footprint. We are using liquid nitrogen, which is a byproduct of the oxygen manufactured for hospitals. And our device emits nitrogen, an inert gas that we are breathing,” said Leizer.

The implication here is that liquid nitrogen is a byproduct and doesn't have a footprint of its own. Leizer continued: "Compare that to other air conditioners with gas that is toxic and polluting. We don’t have any polluting gases. And we don’t consume electricity. An electric air conditioner adds heat to the atmosphere. We have an alternative that doesn’t add heat to the atmosphere."

However, liquid nitrogen is widely used industrially and has its own carbon footprint. A European study found it took 0.549 kilowatt-hours to make a kilogram of liquid nitrogen, and Israel's electricity is not too clean, with a carbon intensity of 560 grams of carbon dioxide per kilowatt-hour.

We don't know how much liquid nitrogen the device uses, but it is disingenuous to claim the device "does not emit greenhouse gases to the atmosphere, hence does not increase planet-warming emissions." But even in Israel, the electricity supply is getting cleaner all the time, and so will the liquid nitrogen.

The Kenshō also doesn't add moisture to the air, so it is going to take less cooled air to cool the body, and it will work in any climate. An evaporative cooler won't work in New Orleans, but this would actually dehumidify the air as well as cool it.

The Green Konoko site makes a big deal about climate change, noting:

"Our goal is to create an effective cooling solution that not only enhances people's outdoor experience but also contributes to the environment and helps to cope with global warming. Our technology solves many environmental challenges such as greenhouse gas emissions, electricity consumption, noise, and humidity creation."

This is a story of adaptation—addressing the effect but not the cause of the problem. What we need is a lot more mitigation, which is defined by the Intergovernmental Panel on Climate Change as “human intervention to reduce the sources or enhance the sinks of greenhouse gases.”

Perhaps Green Konoko can find some solar power to run the compressors and coolers that liquefy the nitrogen. Then they would be doing both adapting and mitigating. But I should chill and stop complaining—this is a very cool idea.