Making liquid nitrogen from scratch (an absurd amount)

TL;DR

The creator built a home liquid nitrogen generator for ~$17,000 that outperforms $24,000 commercial Chinese systems, producing over 1 liter per hour.

Key Points

• 1.The three core components were a membrane nitrogen generator (already owned, from Veritasium), a Gifford-McMahon cryocooler ($5,600, brand new from eBay), and a 30-year-old liquid helium dewar ($1,100).
• 2.The biggest unexpected cost was a dedicated external helium compressor at just over $10,000, required because large cryocoolers don't have integrated compressors like smaller units do.
• 3.Total project cost came to nearly $17,000 — still over $7,000 cheaper than the cheapest Chinese commercial system quoted at $24,000.
• 4.The cryocooler works by compressing helium gas (~100 PSI spike), dumping heat into a water chiller, then expanding the cooled helium inside the cryocooler to reach near-absolute-zero temperatures.
• 5.A custom stainless steel mounting plate was machined to attach the cryocooler to the dewar, with ports for nitrogen gas input, pressure gauges, and safety relief valves.
• 6.The membrane nitrogen generator purifies compressed air to ~100% nitrogen by using hollow polymer fibers that selectively pass oxygen and water vapor through their walls.
• 7.First run produced ~30 liters at 0.58 L/hour (~14 L/day), but was contaminated with oxygen and water vapor because gas demand exceeded the generator's 4 L/min capacity.
• 8.After upgrades — including a new nitrogen generator seven times larger — output doubled to over 1 liter/hour, and nearly 100 liters of crystal-clear liquid nitrogen was collected over a few days.
• 9.Extraction used a pressurized siphon tube system (pressurizing the dewar to ~4 PSI); after upgrading the tube and hose, a full bowl filled in ~2 minutes vs. the original ~12 minutes.
• 10.The dewar developed a small vacuum leak, requiring the vacuum pump to run continuously during operation — a minor inconvenience the creator plans to fix in a future video.