Wednesday, 6 June 2012

Cool lasers could reduce Internet energy demand by 90%

A guest post from Stephen Sweeney, Professor of Physics, Head of Photonics and EPSRC Leadership Fellow at the University of Surrey.

Speed and power have always been the main drivers for the Internet, making it a platform for modern life for consumers, businesses and for economies as a whole. But machines that continually work harder and faster on a global scale also demand exponential increases in energy. The Internet is a vast maw for power.

In the US, Environmental Protection Agency data suggests that Internet usage - and all the servers and networks involved - will require more energy than 18 million average American households. Projected demand for 2014 is greater than Australia's total electricity consumption.

One part of the problem is the number of chips produced and their need for power, but the bigger issue is heat. Chips may be smaller, but they are typically clustered into much larger arrays, each generating waste heat. This means around 40% of energy use in a data centre goes on air conditioning. The current scale of data centres and server farms with hundreds of thousands of square feet of hungry arrays of chips means operations with the energy needs of small cities.

Novel ways are being found to cool servers. Google has built server farms on the Baltic Sea in order to be able to pump ice-cold water around its building, doing the cooling job for them and saving on some bills. It's a solution with only limited potential for most parts of the world. What has been needed is a way to reduce the energy demand at the source - a process which involves more light than heat.

Strained quantum well lasers are traditionally used to beam pulses of light which transfer data at extreme speeds. They are not just used in the optical fibres of the Internet but in most modern technologies, such as mobile phones, CD and DVD players, and supermarket checkouts. However, lasers are often temperature sensitive and control of temperature is needed for them to work effectively - it's this control which requires energy. The electronics involved constitute 80% of the energy needed by the servers, in addition to the air conditioning required due to all the waste heat being dumped into rooms.

Our work at the University of Surrey's Advanced Technology Institute has involved going back to basics, examining the properties of the crystal layer used for the laser and removing its dependence on temperature. When an electric current is put into the crystal, rather than producing light most ends up as heat and this self-heating causes the performance to degrade, requiring external control. To overcome this, we introduced another element into the crystal to change its behaviour. The crystal is based on a semiconductor alloy, just 5 nanometers thick where all of the light is produced. By altering the material at an atomic level - replacing around 10% of the arsenic or phosphorous atoms with bismuth atoms - the whole chain of unnecessary heat and energy is capped at the source.

The simple nature of the change means that no alterations are needed in the production process, which takes place in reactors, with no need for another stage or reactor chamber. Most importantly, the new approach is expected to mean a 5-10 fold reduction in energy demand relating to the Internet. The technology exists in working form and is currently being developed and trialled as part of the European Union funded BIANCHO project. Surrey University is in partnership with UK company CIP Technologies, a photonics developer and manufacturer based in Ipswich, along with several leading European academic partners. The aim is for commercial trialling of the lasers from 2013 onwards.

© The Green IT Review

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