As reported on Slashdot earlier today, Intel has experimented with a data center without any serious airconditioning. Apparently the results are pretty good; they were able to achieve major savings in power usage:

By using air economizers 91 percent of the time (accounting for times when outside air might not be adequate), the company says it could enjoy an estimated 67 percent in power savings at a 10MW datacenter, which would total a very cool $2.87 million.

They allowed the servers run with only outside air as cooling until the outside air reached 90 degrees Fahrenheit (32 degrees Celsius). There was no humidity control, and only a simple air filter. These were pretty basic servers, no special hardware; the setup is detailed below:

For more details, see this video. Overall, over a 10 month period the failure rates of the servers without AC were about double that of the “normal” servers. That sounds bad, but is actually pretty reasonable. In any large server farm, you’ll always have to account for failures, and the savings in AC costs will generally outweigh the extra hardware costs. The downside? This will only work in areas with high temperatures and low humidity such as Las Vegas. Seriously: Las Vegas is a good place to host datacenters! For people that are not in such a lucky position, Sun has calculated that you can also save power by simple setting their AC temperatures a bit higher. For every degree of increase in your temperature, you can save about 4% in cooling costs.

This all sounds remarkably similar to an experiment by Sun and Belgacom with “Free Air Cooling”; this was performed in a less favourable climate (Scotland: it’s wet and cool, instead of the warm and dry Mexico in the Intel experiment). This technology is already used in commercial facilities such as EvoSwitch in the Netherlands, which claims it’s AC units are idle about 40% of the time.

All in all, there are two conclusions that can be drawn from these experiments:

  1. You can save power by turning off your AC units when outside air is cool enough, or your servers can tolerate higher ambient temperatures;
  2. You’ll still need to have those AC units present; none of the experiments has been able to do without them yet. So while your operating costs might go down, your initial investment won’t.