Sustainable Data Centres, Part I
MAY 12, 2021
The data centre 'industry' has reached a strange positioning on 'greenness,' 'zero-carbon,' and 'sustainability.' Call it what you will. It appears from what we read and are told that all ICT clients want 'it,' whatever 'it' is. While many operators are using 'green' terminology in their publicity, in my 33 years of experience in data centre power & cooling, I have yet to find a colocation developer or enterprise client who puts a low PUE as the #1 priority in a design. First comes reliability/availability, as it always has been. Then, goals of affordability, scalability, and energy effectiveness.
From my discussions with contacts in the industry, this view is widely held, although rarely expressed in public.
The current fad for sustainability follows hard on the heels of the claims of low PUEs, even those below 1.0, but at the same time, many share my feeling that PUE is no longer a hot topic. Could this be because PUE has stagnated and remained stable for the past 4-5 years? I feel that I should remind anyone who will listen that PUE should never be used to compare facilities or as any part of a sales promotion. Even the mighty Google (1.12) and Facebook (1.07) have not improved and appear to have stopped shouting about it. It's obvious why.
Once you have optimised your design to match desired energy effectiveness with your reliability aspirations at a given load and read all the best practice guides, there is not much else you can do. Yet, we still have several hundred facilities participating in the EU CoC scheme publicly reporting an average PUE of above 1.7. and why not? It reflects the reality of partial load in colocation facilities with high availability targets, hopefully measured in years of mean time between failures, not minutes of unavailability per year. Even with demand for redundancy and concurrent maintainability, there is still a healthy profit for the operators.
There is nothing wrong with a PUE of 1.7 if it represents a 30% loaded facility designed for a PUE of 1.35. A good design strategy in the M&E solutions is to minimise the impact of partial load and, to avoid doubt, partial loads of 35-40% in many facilities is typical, if not even lower, for the first 3-4 years of service.
One amusing parallel between the sustainability claims of today and the low-PUE of a decade ago is that we already have the 'below 1.0' claims in terms of 'climate positive.' Just as PUE<1.0 claims before them, these claims always appear to be based on rewriting definitions and making assumptions about where 'waste' energy goes. They're potentially good solutions but never reverse climate change in the zero-sum game of carbon accounting. Just the other day, I saw the old argument of putting the switch-mode power supplies and the cooling fans inside a server into the M&E part to claim a saving in IT load. What goes around comes around.
So, what about 'true' sustainability? If you study sustainable energy systems, as I did once-upon-a-time, three distinct steps must be taken in strict order to achieve a sustainable system:
● First, reduce the demand on the system.
● Next, improve the process.
● Third, power the system with renewable energy.
Unfortunately, our present data centre industry seems to think that we must start at the last instead of the first. Then tinker with the second by sweeping ICT equipment that idles at high power and does the exact opposite of the first under the carpet while talking about little else but more bandwidth, new applications, and unfettered consumption.
However, one important point is very rarely discussed - that data centres are only one part of the ICT load. The others are the network/transport/access and the energy consumed at the point of data use and data generation. That would mean us, the people using our mobile phones.
In Part 2 of this series, I will touch on the part that data centres account for in our ICT usage. The three steps to a sustainable data centre, Reduce, Improve and only then consume Renewable Energy, are dealt with in Parts 2-4.