...AND CHEAPER...:

On Orkney and Shetland, which are nearer to Norway than London, giant standing stones are a visual reminder of the ancient Neolithic past.

Now, gleaming white wind turbines are seen as symbols of a brighter, more sustainable future.

"A lot of people describe Orkney as a living laboratory," said Jerry Gibson, operations technician at the European Marine Energy Centre (EMEC), which tests wave and tidal energy converters on Orkney.

"And we have lots of test sites and various different companies that are all working together... in this sort of green economy that we've got going on."

EMEC itself produces "green" hydrogen from renewable sources via a tidal turbine and electrolysis using seawater from Eday, one of Orkney's 20 inhabited islands.

The hydrogen is pressurised and transported 16 miles (26 kilometres) south to the port of Kirkwall, where it is transformed into electricity to power the ferries at the quayside.

Given its plentiful natural resources from wind and waves, Orkney -- home to some 22,000 people -- produces more energy than it uses.

"Hydrogen is important because it's another means of storing energy rather than using batteries or going straight to the electricity grid," said Gibson.

EMEC is also testing wave energy generators in the laboratory, which is more complex to model than tidal energy.

On the island of Yell, some 100 miles northeast on the former Viking stronghold of Shetland, another company, Nova Innovation, is also betting on the ebb and flow of tides.

"The beauty of tidal energy is that it's totally predictable," said Tom Wills, offshore manager at the company. 

"So I can tell you tomorrow or 2,000 years from now, how much tide is going to be flowing through that channel out there, our energy resources are not dependent on the weather."

That predictability is crucial for the stability of energy supply as economies try to move away from high-polluting hydrocarbons.

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