IT’S about 40 feet long, painted mostly white, and looks for all the world like a petrol lorry container without the wheels. Inside is enough computing power to serve a small city, but now it is all but invisible.

For Microsoft’s newest data centre has been sunk down into the depths in chilly waters off Orkney in an attempt to solve a serious problem for tech companies – how do you keep your equipment cool without using expensive and greenhouse gas-causing energy?

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The data centre – they are the backbone of the internet – contains 864 servers, which is equivalent to about 5000 PCs, and has enough memory to store five million movies. A single cable connects the container to Orkney’s renowned wind, wave and tidal energy sources, and the same cable also carries data from the centre to the wider internet.

The data centre could be left in the sea for up to five years as part of Microsoft’s experiment known as Project Natick. The company wants to find less expensive ways of cooling its data centres – the Orkney centre is tiny compared to the giant warehouses used to store the world’s information, but if the experiment is successful, Microsoft envisage building whole clusters of centres on the seabed.

The Orkney experiment has already proven one thing – Microsoft hope to be able to deploy a data centre offshore in 90 days, while doing do on land can take years.

The cylinder was built in France by shipbuilding company Naval and driven to Orkney, the world’s leading region for testing wave and tidal power – a key issue for Microsoft which is committed to using sustainable renewables sources of power.

Microsoft said: “More than half of the world’s population lives within about 120 miles of the coast.

“By putting data centres in bodies of water near coastal cities, data would have a short distance to travel to reach coastal communities.”

Cindy Rose, Microsoft’s UK Chief Executive, said: “Creating solutions that are sustainable is critical for Microsoft, and Project Natick is a step towards our vision of data centres with their own sustainable power supply.

“It builds on environmental promises Microsoft has made, including a $50 million pledge to use AI to help protect the planet.

“I often hear of exciting research projects taking place at our headquarters in Redmond and other locations in the US, so I’m delighted this venture is taking place in the UK. It sends a message that Microsoft understands this country is at the cutting-edge of technology, a leader in cloud computing, artificial intelligence and machine learning.”

Rose quoted corporate vice-president of Microsoft AI and research, Peter Lee, as saying that Project Natick’s demands are “crazy”, but she added: “These are the lengths our company is going to in order to make potentially revolutionary ideas a reality.

“I’m proud that some of the first milestones achieved by Project Natick will occur in UK waters, and hope that the work being done in the Orkney Islands will be replicated in similar data centres in other locations in the future.”

Paul Wheelhouse, the Scottish Government’s Energy Minister, said: “With our supportive policy environment, skilled supply chain, and our renewable energy resources and expertise, Scotland is the ideal place to invest in projects such as this.

“This development is especially welcome news also for the local economy in Orkney and a boost to the low carbon cluster there. It helps to strengthen Scotland’s position as a champion of the new ideas that will shape the future.”