The YouTube channel Hyperspace Pirate[0] has been consistently uploading fantastic videos documenting their attempts to make their own homemade liquid nitrogen machine. They don't shy away from including all the technical details, and throw in plenty of hilarious deadpan humor too. Highly recommend them if you're interested in this topic.

[0]https://www.youtube.com/@HyperspacePirate

Related:

Homemade Liquid Nitrogen Generator - https://news.ycombinator.com/item?id=23828316 - July 2020 (67 comments)

I fabricobbled a liquid nitrogen generator using a cryocooler at home using the same design as Ben at Applied Science [0]. It works very well, I've used it to make liquid nitrogen ice cream many times. It's just slow so I run it overnight.

Applied Science is fantastic channel if you haven't seen it. He's also on HN.

OP's design is much more impressive and hard to build than using a Stirling cryocooler like I did.

[0] - https://www.youtube.com/watch?v=7PWESWqhD8s

I wonder if in the time since this was written if anyone has found a good source for small turbo expanders.

Liquefied air is a potentially interesting mode of energy storage for islanded solar because it doesn't require high pressure storage (which has safety concerns)-- for that application the round trip efficiency isn't critical as there is nothing else to do with the power... but it can't be a total joke. And the basic JT cycle is really poor. I understand that simply adding an expander and another heat exchange stage can improve it a lot.

kids, be sure not to have your cigarette lit whilst separating N2 from air.