It was a couple of years back that the Green Grid started to make noises about reducing the amount of water used by data centers.

It proposed that alongside its iconic efficiency measure PUE (power usage effectiveness), data centers should be using other measure - CUE (carbon usage effectiveness) to measure their carbon footprint, or how much renewable energy they use, and WUE (water usage effectiveness) to measure how much water the center uses.

Now WUE was always going to be a tricky one to implement as it needs a lot of definitions. Are we concerned with using water, or soiling it? And what if water emerges from the plant unfit for drinking, but hot enough to use for heating?

I’ve not heard many people talking about data center water use since the Green Grid announcement, but earlier this month, Microsoft made commitments to cut the water used by its four of its data centers to zero. The blog post by Microsoft architect Brian Janous, explained that “water has traditionally been used in data center cooling systems. However, our latest air-cooled data centers in Iowa, Ireland, Virginia, and Washington are designed to use 1-3 percent of the water required for a traditional data center, and the only water loss in these new systems is through evaporation, resulting in no waste water.”

The post has a graphic, contrasting a traditional “water cooled” 20MW data center, which uses 9.86 million gallons of water a year, and produces 2.46 million gallons of waste water, with Microsoft’s “air-cooled” data center, which uses only 230,000 gallons of water, producing no waste water at all.

Like many graphics it’s short on real information, and the words on the graphic are perhaps confusing. What is the old-fashioned “water cooled” data center they are speaking of? Water cooling of server hardware is probably the way of the future, and a truly water cooled data center will save lots of energy.

However, very few data centers are currently truly water cooled. I think the two data centers being compared are both air cooled. The “old fasioned” one uses CRAC air conditioning units, which are thirsty on both power and water, while the new “air-cooled” one is cooled by the outside air when possible, (so-called “free air” cooling) and only uses a bit of water for evaporative cooling when the outside temperature is too warm.

It’s good to have a reminder that moving to more efficient cooling systems reduces water use as well as energy use. But, since I don’t think Microsoft’s cooling technology is far in advance of the rest of the world, I suspect several other large players could easily make the same claim as Microsoft.

It’s interesting that no one else has yet made a big noise about water use - and probably indicative of the way Green IT in data centers is still finding its voice and working out which issues to talk about.

Microsoft tallks in the same blog post about reducing the use of diesel back-up but, again, this is something that other players could make equal claims about.

Still, whether it’s leading on the issue or not, credit to Microsoft for reminding us that water is an issue. There are shortages of clean water in many parts of the world, and in other places, considerable energy is used to provide it.

It’s all part of the same problem, and any moves to improve things are good.