The water treatment takes care of pathogens - no one that I know of just runs drinking fountains directly into the tower sump (the most common grey water sources I know of are rainwater from a cistern and RO reject water, which is not available for datacenters but a great option for cleanroom fabs). The largest concern I'd have is actually synthetic pharmaceuticals getting dumped down the sink, but that can be a concern with some tap water sources too. As a sidenote, there isn't much done on opinion in this area. You'd be surprised at the research that has gone into this - kill one or two people and suddenly everyone wants you to measure stuff. Sheesh.

Yes, if you grab surface water (as it commonly done by electrical generation plants, as you note) it is a fine idea, but it is not as much of a home run as one would think. Piping is frightfully expensive and the maintainable can be a pain.

Evaporating a single gallon of water rejects about 8330 btus. If you want to schlup water in and out of the system, you have to move about 50 gallons through to get the same cooling as that single gallon. You can do it, but only in rare situations. I've only pulled it off once, and that was for a water municipality who literally owned the water stream at the point we hooked in a side car loop setup to reject heat. Might pull it off once more if we can convince the water company it's OK as long as we tap their feed line prior to the treatment plant. But usually there is no appropriately sized water stream near the datacenter site and, even if there is, water companies freak out about you injecting anything back into their mains (backflow preventors are mandatory on all connections to their mains).

It's a lot of sucking to get 12,000 gpm of really deep cold water up and put right back in. If you can do that, you're in the rare situation of sitting on top a subterranean river. Which can work great, but why not just build next to a surface river or lake?

Actually, yes. You don't have to boil the water to evaporate it. However, most datacenter facilities do not want to be in the desalination business and even with the free heat I don't know if it would be cost competitive with reverse osmosis plants. Note that free low grade heat is not a very rare commodity - most low-water locals can get the same grade of heat with very cheap solar collection.

I would be no more concerned about grey water than I am about city water used in a tower. The typical infection path for legionella is city water, usually to immune-system-compromised patients in hospitals taking showers. Cooling towers (properly operated) actively treat the water specifically to deal with Legionella.

Nope. If you're pushing 15 MW out of a couple towers 24/7 they will not freeze up. You do run the cooling tower fans backwards for a few minutes every once in a while to thaw any ice that forms from splashing on the intake louvers, but the tower itself doesn't freeze up. Last time I put a tower into a 0F design climate, I used a dry sump so if the tower wasn't on the basin was dry.

An annoying fact of physics is that when it gets really cold, evaporative cooling becomes less effective. The air just can't hold much water, and it's the phase change from liquid to vapor that gets rid of your heat. So, it's not freezing that make low temperatures worrisome but actually loss of capacity.

Datacenters, like 99% of facilities with large cooling loads, evaporate water to reject the heat. The water comes in and is essentially boiled off through devices called cooling towers. You reject 1000 btus per pound of water evaporated - there is no more efficient way to reject heat. Not coincidently (if you believe in evolution), your body rejects heat the exact same way.

It doesn't really work for a couple reasons. First, heat doesn't get destroyed in the ground or wicked away (unless you have an underground river, which changes the whole story), it is stored. This is awesome for a building that pumps heat into the ground in the summer and then needs to pull it back out in the winter, but sucks for a datacenter that is pumping out MW of heat 8760 hours a year. Second, massive quantities of heat. A rule of thumb would be 200 feet of well per 3.5 kW of cooling. A modest datacenter is around 15 MW of waste heat, so you need 860,000 linear feet of well (with double that much piping making a U down each well). And after a year you're screwed anyhow because of issue #1.

I'm guessing you must not be from the US because evaporation based cooling systems are THE standard for state of the art industrial and commercial cooling in the US. If you have over 250 tons of load, you have an open cooling tower - dead standard ASHRAE design. The evaporation of water via a cooling tower is THE way you reject heat. If you want to do it dry (as is common in Europe due to much higher fear of Legionella and local code officials freaking out about it), it is FAR less efficient in almost every case, even in monsoon climates like Banglore a wet cooling tower is more efficient.

The real benefit to a 100F setpoint is the free cooling it allows. You can use filtered out door air or evaporatively cooled water from a cooling tower to keep a datacenter at 100F year round just about anywhere. This is a 90% reduction in cooling energy right there using decades old, mature HVAC tech.

The main benefit is that it allows free cooling, either bringing in filtered out door air directly or using a cooling tower to generate evaporatively cooled water for direct use in coils. At a space temperature of 100F, you could cut out 90% of the cooling - even in a full-time humid climate like Malaysia. In most US climes, you can do better.

This just is not true. I work in the industry, performing studies of this nature. The Uptime Institute, 24/7 Group, etc. are not enough to promote sharing of this data between rivals. In a similar arena (semiconductor cleanroom critical environments), I've been paid to do the same damn study three times - but the third and last time it was funded by the government (LBNL) and disseminated publicly (something industry groups, such as SEMATECH, do not do). That is efficiency that saves money on an industry wide scale (and I have plenty of work, I don't need to do the same thing over and over for every little group of companies out there). The government's investment saved industry ten, possibly a hundred fold, expenditure. That's good business on a national economy scale. Who else would be willing to invest in the economic commons?

The Energy Star program has proven across numerous fields the value of providing information to the market. Are you at all familiar with it's evaluated successes? How do you know the most efficient car to buy (government standardized test)? Most efficient refrigerator (government standardized test)? Most efficient hot water heater (government standardized test)? Or would you rather leave all those details in the hands of the lawyer-funded Consumer Reports or something?

Data center operators do not know what an efficient system is, just as you probably do not know how your house's energy use compares to similar houses in your climate (unless you utilized the government's "useless" Energy Star database that has led to no regulation).

Here's a clue: If you live in a first world country there's a 100% chance your economy is based directly on the laissez-faire model. Chances are also high that the areas the most screwed up (i.e. telecom monopolies, etc) are the areas with the most government regulation and meddling. Until you can point out a single thriving economy based on socialism, communism, or whatever it is you're advocating, please STFU about how laissez-faire doesn't work.

You express scorn for publicly funded research (what this entire thread is about) and call it worthless, "socialist," especially if it does not lead to regulation (odd emphasis for you to make, but so be it). Thriving economies that fall under your distorted definition of socialist (ie, government funding of basic research, the subject of this thread) include: The US, United Kingdom, Ireland, Australia, Israel, Germany, France (OK, a bit of stretch there) - actually, can you give me a single country that DOES NOT fund basic research and provide data to the public that has a successful industry? Your absolutist vision of Laissez-faire does not work and has never been implemented (I would argue that based on his writings, Adam Smith clearly accepted the value of public investment in the commons and the extension of that to include intellectual development).