DataCenterKnowledge has a post on Ultra-Low PUE.

Designing for ‘Ultra-Low’ Efficiency and PUE
September 10th, 2009 : Rich Miller
The ongoing industry debate about energy efficiency reporting based on the Power Usage Efficiency (PUE) metric is about to get another jolt. Veteran data center specialist KC Mares reports that he has worked on three projects this year that used unconventional design decisions to achieve “ultra-low PUEs” of between 1.046 and 1.08. Those PUE numbers are even lower than those publicly reported by Google, which has announced an average PUE of 1.20 across its facilities, with one facility performing at a 1.11 PUE in the first quarter of 2009.

KC’s post has more details.

Is it possible, a data center PUE of 1.04, today?

I’ve been involved in the design and development of over $6 billion of data centers, maybe about $10 billion now, I lost count after $5 billion a few years ago, so I’ve seen a few things. One thing I do see in the data center industry is more or less, the same design over and over again. Yes, we push the envelope as an industry, yes, we do design some pretty cool stuff but rarely do we sit down with our client, the end-user, and ask them what they really need. They often tell us a certain Tier level, or availability they want, and the MWs of IT load to support, but what do they really need? Often everyone in the design charrette assumes what a data center should look like without really diving deep into what is important.

And KC asks the tough questions.

Rarely did I get the answers from the end-users I wanted to hear, where they really questioned the traditional thinking and what a data center should be and why, but we did get to some unconventional conclusions about what they needed instead of automatically assuming what they needed or wanted.

…

We questioned what they thought a data center should be: how much redundancy did they really need? Could we exceed ASHRAE TC9.9 recommended or even allowable ranges? Did all the IT load really NEED to be on UPS? Was N+1 really needed during the few peak hours a year or could we get by with just N during those few peak hours each year and N+1 the rest of the year?

KC provides background we wish others would share.

Now, you ask, how did we get to a PUE of 1.05? Let me hopefully answer a few of your questions: 1) yes, based on annual hourly site weather data; 2) all three have densities of 400-500 watts/sf; 3) all three are roughly Tier III to Tier III+, so all have roughly N+1 (I explain a little more below); 4) all three are in climates that exceed 90F in summer; 5) none use a body of water to transfer heat (i.e. lake, river, etc); 6) all are roughly 10 MWs of IT load, so pretty normal size; 7) all operate within TC9.9 recommended ranges except for a few hours a year within the allowable range; and most importantly, all have construction budgets equal to or LESS than standard data center construction. Oh, and one more thing: even though each of these sites have some renewable energy generation, this is not counted in the PUE to reduce it; I don’t believe that is in the spirit of the metric.

If you want higher efficiencies and lower costs you need to be ready to the tough questions.

The easy thing to do is collect the requirements of various stakeholders and say this is what we need built. And, don’t ask the questions of how much does that requirement cost?

I know KC’s blog entry has others curious, and he has lots more appointments.

Hopefully this will wake up many others to ask the tough questions of “how much does that data center requirement cost?”