I have to hand it to the guys at Microsoft, love them or hate them, they work on some really cool projects and this is one is definitely one of their coolest (literally). Check this out! They actually built an air-cooled data center for underwater deployment called the Natick project!
Now why you would want to go through all the trouble to build an underwater data center so you can get a 1.05 PUE, when we can already build a data center using SLIC technology and get a PUE of 1.03 for 1 - 100K servers, I don't know (maybe the fish really need their Office 365 in the drink?) But anyway, I love this kind of project, because it forces you to think way outside the box (or in this case outside the fish tank?)
But wait a minute, why did these guys go through all the trouble of building a big heavy steel hollow steel tube (called the "capsule") and then filling it with computers and nitrogen gas, when there is a so much simpler and far more robust method to build an underwater data center. So, if someone called me up (out of the blue) and said 'Hey Gary, I want to build a data center that I can deploy 1000's of feet underwater..." how would I respond...
I would basically get a big fiberglass box (thats right why use a steel tube which is so space inefficient and heavy and expensive when you can use a box!), put my SLIC Cooled Servers in standard racks, and then I would fill the entire box with our ElectroCool EC-120! Basically I would create a pressure impervious container using our ElectroCool Dielectric Coolant to act as a pressure compensation fluid, a coolant, and preservative against water impregnation, rust and all other sorts of contaminants!
Basically, the problem with the Microsoft Natick approach in my opinion is that they couldn't think far enough outside the fish tank with their approach. If they had spoken to a manufacturer of underwater ROV's or underwater cables I'm sure they would have been told that their approach is flawed in that it relies entirely on the strength of their giant steel capsule and their ability to seal it against the pressure of the water to determine how deep they can put it and how long it will likely last. If Mother Nature can be a bitch at sea level, she can be an absolute terror underwater!
A far more robust method is use a pressure compensating fluid to simply pass through all the pressure right throughout the device. Now, yes we need to ensure that we evacuate all the air in our container before we sink it, but that isn't really all that difficult as we already have to do this with servers we put in SLIC tanks (vibrate them and fill them up slowly). The benefits of using EC-120 as a pressure compensating fluid are pretty interesting actually.
Since we don't have to rely on the strength of the container to support all that pressure, we can use any shape or materials we want for our container, personally I would use something shaped like a 20 or 40 foot standard shipping container made from fiberglass cloth and resin since there are thousands of ships and ports designed to transport and support that shape and fiberglass is pretty cheap and with a good epoxy gel coat on it impervious to water.
Next, while I have to seal my container, I don't really have to worry about small leaks - Wait a minute you say! Just keep in mind that the MSFT guys need to worry about even the smallest leak as it will eventually fill up their container. or likely cause implosion due to pressure (have you ever seen that youtube video of what happens to a styrofoam cup taken down by the Nautilus https://www.youtube.com/watch?v=NHnv1e8cGns? .Well, because I have already occupied the entire volume of my container with EC-120, there is no vacuum to draw in water, and if I put a slight positive pressure inside my container using a simple spring operated pressure compensating piston on the exterior of my container with a small reservoir of coolant it would actually cause the Biodegradable EC-120 to flow OUT of our container through the leak instead of allowing water flowing in! Volia! I can go as deep as want without worrying about the pressure or leaks! Of course, I would also have a small pressure sensor to monitor if I'm leaking EC-120 out, but at least now I have time to react and retrieve my container and save my electronics!
Also because the whole container is filled with EC-120, my servers will basically use the entire container skin as a heat sink and the ocean water as my heat dump. The difference is that EC-120 has a significantly higher heat density than nitrogen gas (EC-120 has roughly 2,000 times heat density) which means I'm going to get excellent cooling without much effort. In fact because of the delta T involved (assuming the water is near 1C in temp and the servers are operating at 45C) I likely don't even have to circulate the coolant in our container, I can just use 100% convective circulation thereby eliminating all the fans, pumps, etc.
Finally, because of ElectroCool's great material compatibility, I can deploy almost any device in our underwater data center (as long as they have no trapped air in their components) without having to worry about corrosion due to saltwater, or any other contaminants. Oh, and before I forget, because EC-120 is fully dielectric, I don't have to worry about any stray currents coming from our devices and causing electrolysis to our container.
Now, I know, there are probably a 100 other things I would have to figure out, but frankly once you solve the pressure problem, the cooling problem, the container shape problem, and the leak problem, the other problems are likely solvable as well. Isn't that what Covey said in the "7 Habits of Highly Effective People" solve the big problems first and you can get in all the pebbles and sand in later?
Oh and by the way, to be fully honest - I didn't figure any of this out, I just basically applied the same technological solutions used by our underwater ROV customers to make their products dive to the bottom of the ocean with ElectroCool EC-120.
So if you want to drop your server or bit miner to the bottom of the ocean - call me, I'll hook you up!
Here is the link to the Microsoft project, you should really check it out! Again I think it is very cool, just wish they called us first! We could have saved them a bundle on all that steel pipe!