Data Centers: The Green Grid for electrical efficiency

Energy consumption of “data centers” (centers for the processing and storage of electronic data) represents the dark side of the rapid development of the Internet. They are reported to be responsible for over 2% of CO2 emissions of human origin. An ecological and economic issue for companies of the sector.

Google, Yahoo, Microsoft, Apple … The big computer companies use huge power and storage capacities: a Google search launched from a computer harnesses this computing power and renders the results in less than a second. A site visited is necessarily “hosted”, that is to say, stored on a server, which delivers its content click after click. The Internet thus works using huge interconnected computing and data storage centers. Various studies have estimated the energy costs of simple actions on the Internet: making a Google search, maintaining an avatar on Second Life, using a computer etc. Daily actions with energy costs that can sometimes be considerable.

The Green Grid

Several giants of the sector (including HP, IBM, Intel etc.) came together to form the Green Grid consortium in 2007 developing methods and standards to improve the energy efficiency of their data centers. Among the key indicators developed:

-       Power Usage Effectiveness (PUE, 2007) is calculated by dividing the total energy consumed by the “data center” by the total energy used by the computer hardware alone (servers, storage, network). The difference represents the energy used for non-computer elements (external power systems, cooling systems, lighting etc.) A PUE equal to 1 means that the data center is perfectly efficient: all the energy consumed is devoted only to operating the computer hardware. In a data center with a PUE of 3.0, supplying a 600 watt server actually requires the supply of 1800 watts to the data center overall. The PUE of companies is now on average fairly close to 2: for each watt used by servers, storage and Internet networks, another Watt is consumed by the cooling systems and the power distribution.

-       Carbon Usage Effectiveness (CUE, 2010) measures the carbon footprint of a data center. It is the ratio between the amount of greenhouse gas emissions generated by the total energy consumption of the data center and the energy consumed by IT hardware. It is expressed in kilograms of CO2 emitted per kilowatt-hour (kWh).  The result is a point between 0 and 1. A 0 means the data center does not emit any CO2. Emissions are calculated on the basis of the primary energy used to operate the data center and provide it with electricity.

How to improve data centers’ energy performance

The majority of the “waste” of electricity or carbon results from air conditioning systems required to offset the heat generated by continuously running servers. Several avenues are being explored to deal more effectively with the problem: optimizing the utilization of servers, improving the management of power delivery, using more frugal cooling systems etc.

More radically, the members of Green Grid recommend building future data centers in geographical areas rich in renewable energy (self-production of electricity) or that are naturally cold. Silicon Valley, the location preferred by many start-ups to date and a hot semi-desert area is a glaring example of what not to do.

Taxing CO2 emissions in the future might encourage hosting services to focus on these more economical areas.

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