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Comment by VorpalWay | Hacker News Reader

I never looked into this, but why would a datacenter consume water for cooling in the first place? Sure, they use some. But just like you fill up the cooling loop in a car, once it is there it just circulates between the heat source and radiators and/or heat exchangers, with perhaps some minimal top off needed (since flexible tubing isn't 100% water proof).

Or are they for some unfathomable reason using evaporative cooling in data centers?

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Evaporative cooling consumes less expensive electricity than air conditioning. Electricity is much more expensive than water (for the same cooling load) in most places DCs are located.

It’s usually open loop - closed loop, so closed loop goes through CRACs or liquid cooled equipment manifolds. That heated water circulates through an heat exchanger on the roof that uses open loop cooling to shed the heat to the surrounding environment.

How inefficient

Way more efficient, that's why they do it. Evaporating water carries an enormous amount of energy.

It uses almost half as much electricity, it’s way more efficient than air cooled chillers by themselves.

East of the 100 degree W line of longitude, there is more than enough water to use evaporative cooling if needed.

(ab)using fresh water in vast quantities is cheaper.

currently.

and also more energy efficient, because evaporating water away takes a lot of energy with it. you have to raise radiators to a higher temperature to keep up with that, or have much more surface area.

There's just a lot of fresh water almost anywhere you'd want to site a DC. In places where water is more expensive, obviously it doesn't make sense.

It’s very efficient. The net electrical energy saved using the latent heat of water is 30 to 100+ times greater than the energy required to desalinate or wastewater recycle the same volume of water.

the unfathomable reason is that it is significantly more energy efficient.

Then it’s not being measured adequately.

The loss of material must be included

If water is evaporated or spent out of the system.. it is not more efficient

Companies will never price in externalities unless they are forced to.

It is more efficient, in terms of cost the datacenter owner pays per unit of heat extracted. Water is cheap in places this is being done, relative to amount of heat vaporization can carry off.

You can certainly argue DCs should pay more for water than other uses, but who gets to decide what is a good vs bad use of water? Pricing in externalities is tricky, and water usage rights are especially complicated. I don't know what a good&fair solution is.

I would guess that evaporative cooling is usually still cheaper even if you price in externalities. In most of the world there isn't really a shortage of water.

Evaporative cooling is practically a cooling cheat code. Why unfathomable? What's more efficient?

Not more efficient at heat dissipation, but radiative cooling panels can achieve sub-ambient dissipation in conditions (like high humidity) that evaporative cooling performance declines in, and with no water consumption.

https://www.sciencedirect.com/science/article/abs/pii/S13594...

Yes, they are using evaporative cooling.

But you can do that in a closed system and recapture the water

You cannot have evaporative cooling without evaporating some water into the atmosphere.

A closed circuit cooling tower still has water spraying onto the closed loop process water heat exchanger coil and mixing with atmospheric air to evaporate and cool the process water indirectly instead of evaporating and recirculating the process water that doesn’t evaporate directly like in an open-loop cooling tower.

I suppose you could condense the evaporated water somehow by using a chilled umbrella or some other ridiculous contraption above the cooling tower, but why would you do that?

FWIW I sell and run commercial electrical work, primarily to mechanical contractors who are installing boilers, chillers, cooling towers, and pumps. I spend my professional life immersed in this type of equipment.

> I suppose you could condense the evaporated water somehow by using a chilled umbrella or some other ridiculous contraption above the cooling tower, but why would you do that?

Specifically to reduce the ongoing demand for water.

DCs need to get to net-zero on their energy requirements and their water consumption.

They are already losing their political license to operate because they're not.

That's independent of the noise and other impositions on the local communities.

For a DC to be politically acceptable it must be:

* Net zero emissions on energy consumption, preferably powered by renewables in addition to the existing local supply.

* Net zero on water consumption, especially fresh/drinking water from local supplies.

* Low to no noise or other pollution.

To quote the great Jeffrey Lebowski, “That’s just like, your opinion, man.”

You may think these are necessary things to do, but data centers are being built as we speak that are not net zero on energy or water consumption. That’s reality.

It would be ideal if data centers had net zero energy and water consumption, don’t get me wrong. That won’t happen without legislation, and even then legislative efforts will be a patchwork that won’t cover everyone due to some politicians selling out their constituents.

That's the current reality and people are realizing that they are being ripped off in their local communities, which will result in an already beginning backlash against datacenters and particularly AI datacenters.

I don't think this will change in the US, because your governments have been totally corrupted and you have much bigger problems than datacenters.

It will/is happening in more enlightened/democratic jurisdictions.

That is called a heat pipe and doesn't get you anything. It's exactly the same as a closed plain water loop with no phase-change involved.

At the scale DCs are operating at, losses from flexible tubing are not negligible either.

1gw of power converts approx 400 liters of cold water into steam _per second_.

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