The Tech Blog

A few months ago around CES, I wrote about Donut Lab’s “all-solid-state” battery. I was skeptical then, but wondered whether some surface-storage or capacitor-like mechanism could explain its claims. A lot has happened since then. So I owe it to whoever reads my posts an update on that.

Donut commissioned Finland’s VTT institute to test its cells. The results show there is a real rechargeable battery here. It held charge for 10 days, so the super capacitor theory looks unlikely. VTT also measured 0–80% charging in about 4.5 minutes at 11C, although a full charge took roughly 7–8 minutes.

Then Ryan@Ziroth did a detailed investigation with more than 20 battery experts. Their strongest clue is in Donut’s own VTT data. The voltage curve looks similar to high-nickel lithium-ion, while the measured cell expansion has a distinctive shape associated with lithium entering a graphite anode(Check Pics). I think the evidence that the tested cell is lithium-based is now quite strong.

The bigger issue is what VTT has not verified. Donut still claims 400Wh/kg and a design life of 100,000 cycles. VTT has independently measured neither. Thats where the problem lies.

And 400 Wh/kg alone is no longer a science fiction. Amprius Tech publishes silicon-anode lithium-ion cells around 400–450 Wh/kg(Will deep dive on this some other day). Those cells make different compromises on power and cycle life, but they show why energy density alone cannot prove exotic chemistry.

Donut Lab rejects Ziroth’s conclusions and says it stands behind its technology. For me, I think consensus is shifting to Donut’s claims being borderline false, on a good number of items. They are still not releasing a product or any serious data to back it up. It is getting close to vaporware territory. Will see how this goes ahead.

Battery tech in EVs is moving very quickly though. Even mature chemistries like LFP are being pushed to limits by folks at BYD. That’s worth looking into soon as well if there is interest.

There is a lot of buzz in this literal “space” about moving data centers into orbit. Space sounds cold, so it may seem like a cooling engineer’s dream. But I think this is one of the most misleading parts of the pitch.

A processor converts almost all its electrical power into heat. A 1 MW AI cluster therefore produces roughly 1 MW of waste heat. On Earth, air or water carries it to chillers, cooling towers or dry coolers. In vacuum, no surrounding fluid carries heat away. You must conduct it from the chips into cold plates and liquid loops, then spread it across radiators that emit infrared energy into space.

Radiated power follows the Stefan-Boltzmann law. It rises with radiator area and the fourth power of temp. It’s estimated that a 40 kW AI rack would need about 80 m² of radiator near 60 °C, facing deep space. At 100 MW, that becomes roughly 0.2 km². At 1 GW, it approaches 2 km², before degradation.

Now running a radiator hotter reduces its required area (though efficiency drops). But heat must flow from a hotter chip to cooler liquid and then to the radiator. Higher temperatures increase leakage, can reduce compute efficiency and shorten component life. Radiators should also face away from sunlight while solar arrays face the Sun, complicating plumbing and attitude control.

This cooling system is far from free. Radiators, pumps, pipes and coolant loops must be built, folded into a rocket, launched, deployed and protected against micrometeoroids, orbital debris, atomic oxygen and surface degradation. The same analysis estimates that coating degradation over five years could require about 40% more radiator area.

Cooling alone does not make orbital computing impossible. But it joins launch cost, radiation, high-bandwidth networking, maintenance and rapid chip obsolescence as reasons space-based AI data centers do not yet make financial sense. I can cover the other issues, with estimated numbers, in a future post. I do hope that more of this investment is directed toward R&D for more pressing problems in the world.