Eeek, I can't imagine what this is like if it scales. What happens to the fire risk when theres 20,000 laptops with aging batteries all sitting together? I hope they take the batteries out, however many laptops use batteries to smooth out power fluctuations.

Laptops aren't designed to be servers - peg your laptop CPU and GPU at 100% and see how long it lasts, I've done this before and the answer is about "2 months", yep sure, this effort isn't targeting that workload, but how many bad apples does it take to start a fire? In their page they say "kubernetes server - no problem" kubernetes DOES keep the CPUs busy, not pegged, but busy enough so that they wont step down their frequency.

I admire the effort to reuse old tech, but boy oh boy would I not want to be a sysadmin here!

My old Lenovo t420 has been running 24/7 pegged as a multi-camera DVR since 2011, no issues whatsoever. Of course the battery is removed, but I don't see many decent laptops struggling running under load for prolonged periods.

I worked for a place that did something akin to this in the early 2010s. Someone figured out how to add 32-bit company laptops to the virtualization cluster (likely because they were using one as a stand in for a server that at the time would have been in the works but not yet purchased) and so once that work had been incurred they just kept "retiring" unserviceable company laptops to the cluster. Imagine a standard wire metro-rack crammed in a telecom closet beside a normal server rack. Now imagine that metro rack literally full of Toshiba Satellite Pro's from about 2005-9. The cluster hosted virtual machines for testing.

No fires, no hardware problems. No special cooling other than the mini-split that was in the closet to cool the server rack. They just kept trucking. But modern hardware is much more high strung and I don't doubt you'd have weird failures.

Edit: Back then VMs were how things were done and RAM was seemingly always the bottleneck by a mile, so the cluster did add up to a meaningful amount of extra performance compared to not having it.