Helium is the only element on the planet that is a completely nonrenewable resource.
On Earth, helium is generated deep underground through the natural radioactive decay of elements such as uranium and thorium. "It takes many, many millennia to make the helium that's here on the Earth," says Sophia Hayes, a chemist at Washington University in St. Louis. The helium seeps up through the Earth's crust and gets trapped in pockets of natural gas, where it can be extracted.
Like hydrogen, its immediate predecessor on the periodic table, helium is lightweight. But unlike hydrogen, it doesn't readily combine with other elements. So, once helium reaches the surface, it can easily escape the Earth's gravitational pull.
Other resources, such as oil and gas, may turn into pollution or be difficult to recycle. But only helium physically disappears from the planet. "It's the one element out of the entire periodic table that escapes the Earth and goes out into outer space," Hayes says.
[0] - https://www.npr.org/2019/11/01/775554343/the-world-is-consta...
N₂ boils at −195.8 °C, but that will be higher at 30 bar.
Next question: why do they need gas at lower temperatures to achieve higher temperatures? Do temperatures inside that acoustic wave vary that much?
Really cool to see a company getting this in the market. I'm surprised though to see a standing-wave device instead of a traveling-wave device.
I thought I read somewhere that we are running out of He.