Green data centers: Identifying truly energy-efficient data centers

December 27, 2013 by  
Filed under Green Energy News

Energy-efficient data center facilities are important. But plenty of data centers base their
green credentials on promises that cannot be fully supported or statements that are too glib to be

People increasingly perceive
data centers as energy hogs

prompting technology vendors to position their products as
sustainably made or “green.” Even large data center owners are claiming to have green facilities,
yet some of these promotions should probably be taken with a large dose of cynicism.

Carbon-neutral data centers

The biggest claim that IT equipment vendors and green data centers make is that all items are
carbon neutral: Supposedly, the overall amount of carbon used in the creation or operation of an
item is offset in some way. In essence, the same amount of carbon released through owning or using
the device is being trapped through other means that are under the control of the vendor or

The main way to reach carbon neutrality is through planting trees — which is good, but is it
all as it appears to be? What possible carbon output is really being measured? If it is the total
amount of carbon used in the manufacture of any piece of IT equipment, then it is doubtful that
this is being offset completely. IT equipment is made from a variety of materials, ranging from
petro-chemicals to rare metals and silicon. Acquiring the raw materials for each of these is not
particularly carbon efficient, and it is doubtful if anyone could carry out the necessary modeling
to calculate how much carbon has been used in procuring the raw materials for a single server or
network switch.

So, let’s be a little looser with the definition and just look at the carbon used in operating
IT equipment. Then this just comes down to a simple calculation of energy usage by the equipment,
right? Yes — and no. Energy usage within the equipment itself is just one part of the equation –
there is also the other equipment that is dependent on the item or that which the item itself
depends on. So a 150W server running in a data center with a power usage
effectiveness (PUE)
of 2 would require a carbon offset of at least 300W.

However, as more IT functionality creeps outside of the on-premises data center, how about the
proportion of energy that the organization’s other, cloud-based data centers use? ¬†What about
the energy the servers and systems running the Internet consume? And what about the bring your own
device movement that has employees using data center energy as well?

Then there is the carbon offset side of things. If this is based on planting trees, does it
consider the age of the tree for the amount of carbon it can produce or leave when it dies? Does it
take into account the failure rate of newly planted trees? It’s 70%. Clearly, carbon offsets are
fraught with issues.

Data centers using renewable energy

There is also the claim that a facility is powered by renewable energy. In some cases, this is
demonstrably true. There are data centers built in countries, such as Iceland, where the vast
majority of energy is provided from hydro
or thermal sources
and is, therefore, renewably generated.

Some facilities are built right next to specific hydro or other renewable
sources (such as many
in Colorado
) and only tap into the grid energy network should there be problems with the main
renewable source.

But for the majority of so-called green data centers, the energy contract is with a company that
invests in renewable energy — but that does not mean the energy a facility gets comes from those
investments. For example, in the U.K., the vast majority of energy comes from the National Grid,
and a specific electron cannot be forced to a specific place from any particular generator.
Therefore, although a facility owner may be paying on a renewables contract, the energy can come
from nuclear, coal, gas or oil just as well as it could be from wind, hydro, solar or any other
green system. In fact, less than 10% of the U.K.’s overall energy is provided via renewable means.
So, there is a 90% chance that the power is not coming from renewable sources.

In one case in the U.S., a data center facility boasted of its green credentials through a
contract with a local wind farm. The wind farm was built to provide more than 300,000 homes with
energy, but the data center took most of this. The homes could no longer be viewed as green — as
was the idea — unless the companies were double-accounting for the energy.

Finally, there are PUE claims. On its own, the PUE indicator is easily manipulated. PUE is a
measure of the proportion of energy used in powering a data center facility against how much is
used to power IT equipment. A facility where peripherals use 1 watt of energy to every 1 watt used
at the server has a PUE of 2. This shows 2 watts of data center power against 1 watt of IT
equipment power.

In theory, a data center with a PUE of 1.5 is more energy efficient than one with a PUE of 2.
However, what happens if you virtualize all the IT servers so that 80% of existing servers can be
turned off, but do not change the peripheral equipment operations? The overall IT equipment wattage
drops by 80%, but the peripheral wattage stays the same. There is now an IT platform that is far
more utilized and energy efficient, but the PUE has risen appreciably — which has to be wrong.

Don’t fall for greenwashing. Make sure that green claims are provable and that you can stand by

This was first published in December 2013

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