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Comment by danans

13 hours ago

https://www.wesa.fm/environment-energy/2024-02-19/weirton-fo...

> Optimistically assuming 12 hours of sunlight per day, a 40MW datacenter would need 480MWh of batteries to cover the dark period, costing $50 million.

A 40MW data center doesn't run constantly at 40MW. That's its load rating. Like any industrial facility, actual peak loads are probably around 80% and average loads are lower.

Also, why do you assume that the data center has to be off-grid? That's a constraint of a space-based datacenter, not a ground based datacenter.

Datacenters with storage can complement grid power.

> The cheapest batteries today are around $100/kWh.

If we are comparing ground based data centers to hypothetical space based ones, then consider that grid scale iron air batteries are coming soon at $20/kWh.

https://www.wesa.fm/environment-energy/2024-02-19/weirton-fo...

You quoted me saying, "There's not much point in launching a datacenter into space if you can power it on the ground 24/7 with solar + batteries." and suggested, "...that the price of batteries is already cheap enough for terrestrial data centers to make more economic sense than launching a datacenter." So I replied with some napkin calculations estimating the cost of powering a datacenter 24/7 with current solar + batteries. You could assume those solar panels and batteries are on the grid, allowing excess capacity to be sold to others, but then you need another $20 million for backup generators.

I assumed the battery + solar setup would need to provide 40MW because while datacenters usually do run below capacity, you'd also want some extra capacity to account for cooling systems, battery/panel degradation, and the fact that for some tasks (such as AI training), you actually do get close to 100% capacity for long periods of time. Feel free to cut my numbers by 20%, but I don't think that would change the bottom line: off-grid datacenters could be cost competitive in some regions, but the upfront costs don't make them worthwhile right now. If battery costs go down (as I hope they will), that will likely change.

An orbital datacenter would not need significant batteries because it would be placed in a dawn-dusk sun-synchronous orbit. The panels would only be occluded during solar eclipses, which in low earth orbit last a few seconds. Starcloud is betting that launch costs will plummet but battery costs will not, and that they'll be able to cheaply solve space-specific issues related to cooling, maintenance, and reliability.

If you look at my other comments in this thread, you'll see I predict they will fail. A lot of people are coming to the same conclusion, but for mistaken reasons (eg: thinking that space-based datacenters would need as many batteries as ones on the ground). I'm just trying to correct that.

  • > If you look at my other comments in this thread, you'll see I predict they will fail.

    Yep, we agree on that.

    > off-grid datacenters could be cost competitive in some regions, but the upfront costs don't make them worthwhile right now.

    I still don't understand why the alternative to space based datacenters being proposed is off-grid datacenters.

    Why not compare it to grid-connected datacenters with enough behind the meter generation and storage to avoid peak grid prices? After all the ultimate comparison metric is cost (and ideally C02 emissions)