A black day for data centre carbon emissions

Learn why it is important to reduce your data centre’s carbon emissions and how to improve your energy efficiency, according to our data centre expert.

This article can also be found in the Premium Editorial Download: IT in Europe: Building a business case for a green data centre

If we don’t get a grip on carbon emissions, the world will end, right? I doubt that your organisation sees things in this light, yet it is likely that its carbon emissions will come under close scrutiny over the coming years. Business electricity prices have been notoriously variable over the past couple of decades, but the...

trend underlying the variability has been unavoidably upward.

At just a basic level, as the dependency on IT has grown, the percentage of an organisation’s energy bill attributed to the data centre has grown and has created a focal point for the business.  When finances are tight, the immediate reaction is to look for soft targets -- and the data centre power bill is one of them.

UK carbon emission reduction

The situation is worsening as governments around the world increase their commitments to reduce carbon emissions. The UK is a good example: The government have taken on heavy carbon emission reduction targets, and have put laws in place to put pressure on organisations to achieve these. The Carbon Reduction Commitment (CRC) Energy Efficiency Scheme was put forwards as a carrot-and-stick approach for heavier energy users. Those making the biggest savings would make money out of the scheme, while those performing badly would pay penalties.

This has now been changed, and all organisations caught in the CRC net will end up paying for their carbon outputs in the form of a “carbon tax”. Because the government needs more tax revenues, you can take it as a given that even more organisations will be taxed in the future.

So it doesn’t really matter whether your organisation wants to control carbon emissions for global sustainability reasons or not -- the cost of not working on lowering output may be enough to break the camel’s back and be beyond capacity.

Power distribution and high levels of carbon emissions

Let’s look at a couple of the major reasons for concern about energy usage in the data centre: power distribution and overall efficiency.

In a fossil fuel power station, typically there will be a 10% loss in energy capability just in burning the fuel. In effect, only 90% of the available energy actually creates electricity through becoming steam to drive a turbine. The overall energy efficiency in creating electricity in this manner will be around 45%.The high-voltage transmission losses from the power station to the local substation will also be around 10%, so we’re already down to around 36.5% overall efficiency.

From the substation to the data centre, there should be only one transformer in place, with further losses of around 2%.  In the data centre itself, each transformer will introduce around 2% losses -- and there may be five or more transformers in play before the electricity gets to a point where the IT equipment can make good use of it. That makes for further losses of nearly 11%, and lowers our overall energy efficiency from 45% to around 32%. All of the losses will be in the form of heat -- which means that even more energy is required for cooling.

How carbon emissions are linked to PUE

But this low-level energy efficiency is attributed to the data centre equipment itself, before a single CPU cycle has been turned or a byte of data processed. How much of the electricity that actually reaches the IT equipment is carrying out useful work? Power Usage Effectiveness (PUE) is increasingly used to measure the overall energy efficiency of a data centre through dividing total data centre power usage by the power used for running IT workloads. Uptime Institute research has shown that the typical data centre has an average PUE of 2.5. This means that for every 2.5 watts in at the utility meter, only one watt is delivered out to the IT load. Uptime Institute estimates most facilities could achieve 1.6 PUE using the most efficient equipment and best practices.

Only 40% of electricity coming into a data centre is used to run workloads. The rest is “wasted” through cooling, UPS and other secondary systems. A further 60% of the energy is not used for “real” IT work. This means that only 13% of the oil/coal/gas we started with is actually available to drive useful data centre work. Even when the electricity hits the server, there will be more transformers in place, losing even more energy in the process.

But the worst is yet to come. Let’s assume that 80% of the electricity is used in the server environment (the other 20% being in storage and networking equipment). Again, research shows that the “average” utilisation of servers in a standard distributed computing environment is between 5% and 10%. Therefore, 90% of electricity used in running servers is actually wasted because there is no workload being applied to it. Now, our already poor overall energy efficiency has suddenly shrunk to around 1.3% -- if we consider the storage and network environments to be almost 100% efficient.



Overall efficiency

Coal burning



Electricity production



High voltage transmission and initial transformation



Lower voltage distribution to point of commercial use



Data centre distribution



PUE impact



Workload efficiency




Overall efficiency of 1.3% is not sustainable–, so organisations are right to look at energy utilisation in the data centre to lower their carbon emissions -- and their energy costs. For every 10 grams of carbon emissions created, directly at the data centre, nearly  1 kg of carbon emissions will be created at the power station.

A lot can be done within the data centre itself to address the generation/transmission losses involved, but it’s not the only place in an organisation where energy consumption can be reduced. IT can help with these reductions, for example, by making energy-intensive business processes more efficient or reducing the need for employees to travel in and out of the office to be able to access the company’s services. Surprisingly, there is more that can be done outside the data centre by looking at newer means of power generation that can impact the 65% energy losses involved before electricity even gets to your organisation.

In the coming months, research and analysis company Quocirca will be studying how organisations can look at various aspects of the data centre to create a more energy-effective environment. This will range from short-term fixes to long-term strategic directions. In addition, it will look at how IT can be positioned to create an energy-efficient organisation, not just an energy-efficient data centre.

Clive Longbottom is a service director at UK analyst Quocirca Ltd. and a contributor to SearchVirtualDataCentre.co.UK.


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