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Intel Shows Data Centers Can Get By (Mostly) With Little AC
Ted Samson IW writes "InfoWorld reports on an experiment in air economization, aka 'free cooling,' conducted by Intel. For 10 months, the chipmaker had 500 production servers, working at 90 percent utilization, cooled almost exclusively by outside air at a facility in New Mexico. Only when the temperature exceeded 90 degrees Fahrenheit did they crank on some artificial air conditioning. Intel did very little to address air-born contaminants and dust, and nothing at all to deal with fluctuating humidity. The result: a slightly higher failure rate — around 0.6 percent more — among the air-cooled servers compared to those in the company's main datacenter — and a potential savings of $2.87 million per year in a 10MW datacenter using free cooling over traditional cooling."
The fluctuating humidity probably wouldn't be a problem in New Mexico either. The rest of us might have a problem.
One benefit to going DC is that you can wire your battery modules directly into the DC distribution grid for the CPUs (with appropriate charge and cutover circuits), and forgo the inefficiencies in converting AC to DC at the UPS, and then back out again, only to convert the AC back to DC at the CPU.
Having multiple of a commonly used voltage used in renewable energy also helps if, for example, you want to feed your datacenter directly from say wind or solar, in addition to a set of AC to DC converter.
Sun is also running a comparable experiment with Belgacom and allows you to log in to a live interface to view stats on in- and outlet temperatures and more at http://wikis.sun.com/display/freeaircooling/Free+Air+Cooling+Proof+of+Concept For more details and analysis see http://www.datacenterknowledge.com/archives/2008/09/18/intel-servers-do-fine-with-outside-air/ or http://securityandthe.net/2008/09/18/intel-sees-the-future-of-datacenters-and-it-does-not-include-airconditioning/
DC Knowledge also has a nice video of this experiment at http://www.datacenterknowledge.com/archives/2008/09/18/video-intels-air-side-economization-test/
Having very large PSUs is a pain in the ass. Failures tend to be catastrophic and dangerous. They're more expensive to build and maintain. (think basic economy of scale problems) They also may not be any more efficient than distributed conversion. You also tend to distribute much lower voltages with DC than you do with AC. (240vac vs 48vdc) This gives very high amperages which requires much thicker wiring. Copper is EXPENSIVE right now, this makes it a big factor in the cap-ex of building a new DC.
This is why a lot of work is going into improving the efficiency of commodity power supplies. Groups like 80plus.org are doing great things.
Also some other links:
http://www.treehugger.com/files/2007/07/secret_efficien.php
http://services.google.com/blog_resources/PSU_white_paper.pdf
I can say with much certainty that most of the big vendors are starting to warm up to this and know that needless cooling is not going to stand up to scrutiny much longer. In fact, Intel is not the only one looking at this. These standards that we apply for acceptable heat and humidity levels were a) never designed for IT equipment and b) were never actually tested. The come from old telecom standards and they were primarily assumptions based on very old technology. Anyone looking at datacenter eff is looking real hard at these and asking themselves, what are the real acceptable ranges for modern equipment, under modern conditions. When this is all said and done, the answers are going to be much more heat tolerance and far greater humidity tolerance in both directions.
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We're talking less than a minute needed. In the end they couldn't use the several large and expensive flywheels because they could not provide power long enough.
If you're powering your whole data center 'for a while' with these... you must have very few servers (like a handful).
Experience teaches only the teachable. -AH
100% relative humidity is when the dewpoint is reached and water condenses out of the air (aka fog). The popular idea that 100% rel humidity = rain is not accurate.
You're only half right. If you actually read any of the articles you linked to you'd know that.
Aluminum wire by itself is no hazard at all. It just doesn't do well when you connect it copper or other galvanically dissimilar materials that can cause corrosion. And there are some issues with dissimilar thermal expansion rates, but that's largely dependent on the terminal size and type.
You're right that the standard 14-10 AWG wiring used in homes is typically not aluminum, and that the wiring of that size that was aluminum and installed in the the 60s and 70s needs to be treated specially.
But aluminum was and still is commonly used in large-gauge wiring, starting around 8 AWG -- the ~2 AWG feed for many homes *is* aluminum. And it's entirely possible to safely wiring aluminum, even of smaller gauges, even of older alloy types, so long as you understand the limitations and use CO/ALR-rated devices.