Ice is nice, hot is not
Phoenix, Arizona in the US has an average annual temperature of over 22 degrees, soaring to over 40 degrees in summer. It's not the most intuitive place to put a datacentre, yet a company recently launched a 180,000 square foot co-location centre there.
The unusual element of the story, the part that has grabbed a couple of headlines, is its use of ice balls to cool the facility.
Using cheaper night-time energy, the facility, which is owned and run by i/o Data Centers, uses hundreds of small, dimpled balls floating in a glycol solution cooled to minus five degrees. The glycol is pumped around the chilling system, cooling air that passes over the datacentre's computing systems. The system that cools the glycol only runs overnight, with the ice acting as a thermal cache.
According to Cryogel, the maker of the cooling system, it saves energy and around USS$1,250 per kW, costing around US$60 per ton for each hour of cooling. Users will recoup the investment in up to three to five years, and it's greener, reckons Cryogel, because utility companies tend to burn less expensive fossil fuel overnight because demand is lower, although HP has contested this claim.
The obvious question, is to ask why anyone would build a datacentre in Phoenix's hot desert climate at all. According to this story, there's a couple of core reasons: Phoenix has a stable climate with none of the US mid-west's phenomena such as typhoons and hurricanes, and its dry air makes evaporative cooling much more efficient. Space is also relatively cheap, which enables Cryogel's large installations to be economic, while most datacentres wouldn't be able to cost-justify the space.
But despite i/o's plan to install 4.5MW of solar power on the roof, the installation could hardly be described as green. Maybe if the company had dug down 10 metres and built the system underground, where temperatures are much more stable, it could justify the description.
As it is, a fancy cooling system that just might result in fewer fossil fuels being burnt is thin justification. By all accounts, the facility doesn't even export its waste heat to be used for other purposes.
A colo company has to go some way these days to grab some press and while green may be the right button to press from a PR perspective, locating it in the Arizona desert is not.