greener calculations

Greener calculations

1 August 2011

As a world-leader in climate change research, the Met Office has a unique responsibility to reduce its own carbon emissions. We already operate out of a highly efficient head office building. But with so much of our work relying on the output of two power-hungry supercomputers — we faced the huge challenge of reducing electricity consumption without compromising capability.

Our ability to predict the weather, create complex climate models and turn raw scientific data into practical forecasts and advice is thanks, in part, to our supercomputers. Roughly the size of two small single-decker buses, they can handle more than 100 trillion calculations per second - vital for the hugely complex weather and climate models they produce.

Every day, data from the machines helps organisations around the world save millions of pounds, run more efficiently and, critically, reduce their carbon emissions. What's more, the detailed forecasts produced help people prepare for severe weather - which results in countless saved lives.

There is no dispute that the supercomputers are vital to the work of the Met Office. But this kind of computing power comes at a cost - both financially and environmentally - as average power consumption runs at more than 1.6 megawatts of electricity per year.

One of our supercomputers

The challenge was clear - even if the solution was not. How can the power consumption of the supercomputers be reduced without compromising performance?

Understanding power

As with so many innovations at the Met Office, the answer came from a brilliant piece of original thinking. The Met Office Property Management Building Services Engineer, Peter Clayton-White, came up with an elegant but untried idea. Rather than rethinking the processing of the computer itself, Peter looked at how the machines were powered, as he explains:

"Put simply, the supercomputers draw electricity from an AC power supply but actually run on DC power. Within the circuit, there were two stages at which AC was being converted into DC - which resulted in an energy loss in the form of heat."

Peter surmised that if both of those stages could be removed, an energy saving of around 11.5% could be made. He further realised that if they could save this energy - usually lost in the form of heat - they could also reduce reliance on the cooling system, used to stop the computer overheating, by a similar percentage - creating an additional energy saving.

Overcoming the challenges

To successfully turn theory into practice, Peter faced a number of hurdles. Not least of these was that all IT devices - from the humble laptop to massive supercomputers - are built to run on an AC (alternating current) power supply.

"One of the biggest challenges we faced was convincing IBM to convert the supercomputer so it could run on DC (direct current). But it didn't stop there, we also had to find a DC rectifier battery unit at the voltages we needed."

IBM was able to help solve the first problem by providing special power regulators - but the battery unit was a little trickier. A vital component, it will kick in if there is a power cut - yet it is no normal device. While an average car battery charger runs on around 12 volts DC, this needs 405 volts DC. You can't simply buy a device like that off the shelf, so we had to have a custom-made DC rectifier battery unit.

Groundbreaking results

Today, the Met Office is the only organisation in the world to run its supercomputers on DC power. By doing so, we expect to save 881 tonnes of CO2 emissions per year - which equates to approximately £111,000 at current energy prices. To put that into perspective, that's equivalent to more CO2 emissions than produced by all the flights taken by Met Office employees between 2009 and 2010.

For Peter and the Property Management team, the extraordinary achievement has not gone without recognition - they were a 'Highly Commended' Finalist at the 2010 Institute of Engineering and Technology Innovation Awards.

Green initiatives

The Property Management team has been responsible for a number of the Met Office's 'green initiatives' - all designed to reduce energy consumption and minimise our carbon footprint.

Super cool savings

Most of the energy the supercomputer consumes is turned into heat, which needs cooling. This cooling has traditionally been achieved with large energy-consuming chillers that pump chilled water across the site into the IT halls.

To reduce the energy required, the Met Office installed a 'free cooling' system in 2010. This is a roof-mounted system that harnesses the outside air temperature, whenever possible, to naturally chill the water. It has enabled the Met Office to save 9.1% of displaced electricity, or £100,000 at today's energy prices.

Harnessing the power of nature

Other energy saving initiatives include the installation of computer controlled lighting throughout the Met Office HQ, which dim down as the daylight level increases - saving up to 95% of lighting power.

The Property Management team also conducted several feasibility studies on alternative means of energy, including biomass, solar energy and wind power.

"The problem with photovoltaics is that they are expensive to install and will only produce around 1% of our total annual needs. Wind turbines present two issues - the spinning blades corrupt the data of landing instruments at nearby Exeter airport, as well as the weather data recorded on site here. Finally, to generate electricity from a steamed boiler running on sustainably-sourced chipped wood requires a huge capital investment," explains Peter.

We may not have all the answers yet. But, undeterred, we'll continue to explore innovative ways of using new, or refining existing, technology to reduce our carbon emissions.

From AC to DC video

This video describes how we changed the power supply for our supercomputer from AC to DC power.

Reducing carbon emissions through energy-efficient power conversion
We have successfully developed and implemented a process which means we can run our supercomputer more efficiently. Peter Clayton-White, Building Services Engineer, explains how we use Direct Current rather than Alternating Current power conversion.

Transcript of 'Coverting from AC to DC' video [103kb] (opens in a new window)

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