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Want an energy efficient datacenter? Build it underwater

spectrum.ieee.org

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Re: Want an energy efficient datacenter? Build it underwater

#81

Post by wpaladin »

linkregister wrote: post #78
fryguy wrote: post #37

Earlier quoted context omitted.

For a, you can put a sacrificial anode on the frame. Given that the rate of corrosion should be known, the size of it can be calculated to however long the pod is expected to be in service.

This sounds really interesting, can you explain it further for a layman? (Not being snarky, I genuinely know very little about chemistry)

This is probably what OP meant:

"They are made from a metal alloy with a more "active" voltage (more negative reduction potential / more positive electrochemical potential) than the metal of the structure. The difference in potential between the two metals means that the galvanic anode corrodes, so that the anode material is consumed in preference to the structure." https://en.wikipedia.org/wiki/Galvanic_anode

Re: Want an energy efficient datacenter? Build it underwater

#83

Post by marze »

nkoren wrote: post #70
longerthoughts wrote: post #58

Earlier quoted context omitted.

> b) Isn't marine biology highly sensitive to heat pollution? Impact on the marine environment is briefly mentioned in the last couple of paragraphs of the article, although they're a little dismissive and don't provide any evidence supporting their claim of negligible impact.

Nuclear power plants usually dump their tertiary cooling water into the ocean. That's not a great situation for the local sea life (within a few hundred meters, IIRC), but doesn't have much significance beyond that. That is several orders of magnitudes more heat output than could conceivably come off a data centre. So their dismissiveness is likely warranted. A bit more concerning is the notion of relocating these da…

A 1 GW reactor puts 2 GW+ heat into the sea, a river, or lake.

A server sub would put 200W * (say) 1000 servers, or 0.0002 GW.

Re: Want an energy efficient datacenter? Build it underwater

#84

Post by saeranv »

ouid wrote: post #64
smallnamespace wrote: post #32

Earlier quoted context omitted.

> Isn't land-based biology highly sensitive to heat pollution? No, land-based organisms comparatively have a much, much higher tolerance to temperature swings. Water's high heat capacity and conductivity means that most marine environments have extremely stable temperature ranges (a few degrees one way or other), so most marine species are adapted to live in only that range, and quickly die otherwise. Tropical fish a…

Sunlight imparts about a kilowatt per square meter to the surface of the ocean at noon, I'm not exactly sure how to use that information, but it does seem relevant for bounding the problem.

This gets a lot lower with differing latitudes and seasonal and daily cloud cover/evening time - closer to 100 W/m2 [1]. So over a day you'd get 2.4 kWh. In comparison an electric space heater uses about 1 kWh of energy in an hour.

So how much will 2.4 kWh change the temperature of a cubic meter of water at the ocean surface?

Density of water = 1000kg/1m3 so mass = 1000 kg

2.4 kWh = 8640 kJ

Heat_Energy = Conductance * Mass * change_in_temp

8640kJ = 4.186 kJ/(kg⋅K) * 1000kg * xC

x = 2C

So solar heat will change the first meter of water by about 2C over the course of a day. That's a small number b/c solar radiation is not a huge contributer to temperature swings. Instead what will effect the temperature difference is the seasonal change. If we can calculate the heat energy gained or lost due to seasonal extremes and water temp, then we can figure out what the range of acceptable heat energy is for surface water.

[1] https://www.withouthotair.com/c6/page_38.shtml

ETA: logic.

Re: Want an energy efficient datacenter? Build it underwater

#85

Post by verelo »

nkoren wrote: post #70
longerthoughts wrote: post #58

Earlier quoted context omitted.

> b) Isn't marine biology highly sensitive to heat pollution? Impact on the marine environment is briefly mentioned in the last couple of paragraphs of the article, although they're a little dismissive and don't provide any evidence supporting their claim of negligible impact.

Nuclear power plants usually dump their tertiary cooling water into the ocean. That's not a great situation for the local sea life (within a few hundred meters, IIRC), but doesn't have much significance beyond that. That is several orders of magnitudes more heat output than could conceivably come off a data centre. So their dismissiveness is likely warranted. A bit more concerning is the notion of relocating these da…

> "A bit more concerning is the notion of relocating these data centre pods"

What are the requirements for cargo ships? I suspect they run into this regularly when in a dock for extended periods or undergoing maintenance that doesn't require a dry-dock.

Re: Want an energy efficient datacenter? Build it underwater

#86

Post by theptip »

longerthoughts wrote: post #58
jefflombardjr wrote: post #24

I'm all for exploring new approaches, however: a) Salt water is highly corrosive. Wouldn't maintenance costs be high? b) Isn't marine biology highly sensitive to heat pollution? For high latency services like Amazon Glacier, wouldn't it make sense to host in a place like Iceland? Really cheap hydrothermic/clean power. Highly educated local talent pool, and relatively consistent cool temperatures. If you're maintainin…

> b) Isn't marine biology highly sensitive to heat pollution? Impact on the marine environment is briefly mentioned in the last couple of paragraphs of the article, although they're a little dismissive and don't provide any evidence supporting their claim of negligible impact.

The claim is:

> The water just meters downstream of a Natick vessel would get a few thousandths of a degree warmer at most.

Sounds negligible to me, but I'm not a marine biologist. Would be interested to hear a specialist weigh in.

Re: Want an energy efficient datacenter? Build it underwater

#89

Post by fryguy »

linkregister wrote: post #78
fryguy wrote: post #37

Earlier quoted context omitted.

For a, you can put a sacrificial anode on the frame. Given that the rate of corrosion should be known, the size of it can be calculated to however long the pod is expected to be in service.

This sounds really interesting, can you explain it further for a layman? (Not being snarky, I genuinely know very little about chemistry)

Basically, the reason that things corrode is that there are dissimilar metals, one with more electrons than the other creating a voltage between them. So your part is a battery and the ocean is the "wire". The electrons move from your part (corroding them), to other parts with less electrons. If instead you have a sacrificial piece of zinc, the zinc has more electrons than your part so the electrons will come from the sacrificial piece of zinc instead of your part. Think of it like a lightning rod, but for corrosion instead of lightning. It's more complicated than this, but that's the general idea.
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