Image caption The government hopes wind turbines can help reduce carbon emissions

The statistics are astounding, the gigantic scale of some of the world's largest wind turbines hard to comprehend - even when you're close enough to touch.

Each blade of the latest turbines to be installed in British waters stretches for a staggering 60 metres - that's slightly longer than the entire wingspan of a Boeing 747 jumbo jet.

The massive rotor is about the same size as the London Eye and, if laid on the ground, would cover most of two football pitches.

The towers that hold the blades aloft are about 100 metres high, which makes them taller than Big Ben.

Thirty of them, constructed for the Swedish power company Vattenfall, are being installed in the Irish Sea off the coast of Cumbria.

This is the newest of a dozen offshore wind farms around the UK, a key part of the government's plans to use green energy to try to meet tough targets for cutting carbon emissions.

Blade power

Built by the German firm REpower, the massive components were prepared for assembly on the quayside at the Harland & Wolff shipyard in Belfast.

Starting at the razor-sharp tip of one of the blades, where it is thinnest, the impression is of a slender wing - seemingly too delicate to endure the brutal storms of the ocean.

But the closer you get to the hub, the sturdier the blade becomes, even resembling the hull of some sizeable vessel.

Each designed to generate 5 MW of electricity, these leviathans have nearly twice the output of earlier models - part of a trend in this fledgling industry of gradually increasing size.

The new wind farm, known as Ormonde, stands off the coast near Barrow-in-Furness.

The logic of planting turbines out at sea is that the winds are usually stronger than on land - and there are fewer people likely to object.

But the challenge of fixing foundations to the seabed and then constructing and maintaining these structures means the bill is huge - this one wind farm is costing £500m.

And its total power output - when the wind blows - is due to be 150 MW. By comparison, a conventionally-powered gas or coal station might produce 1,000MW.

Future plans

At the moment, price is the great weakness of offshore wind. Right now, it's the most expensive means of generating electricity, costlier even than nuclear.

The power companies earn an attractive subsidy for power produced this way but the costs will find their way on to household bills and critics warn that this could make offshore wind highly unpopular.

The government hopes that prices will fall as technology advances and it wants thousands of turbines to be installed in the waters around Britain in the next decade.

Current plans call for 18,000 MW of offshore wind capacity by the year 2020 - that would amount to roughly a quarter of the country's entire electricity output.

Business figures say it is just about feasible to meet that target, but only with a surge in production, and with the political will to support it.

My impression is that, as with any new industry, experience reveals how some components and building techniques work better than others, and how people are keen to adapt.

Skill requirements

In Belfast, the Harland & Wolff shipyard made the switch from constructing vessels to handling wind turbines.

And hundreds of people are acquiring the climbing skills needed to work on turbines - our team had to go through a training course on working at heights, designed by the wind industry, before embarking on this assignment.

The big unknown is whether plans for really massive offshore wind farms, the so-called Round Three projects, will go ahead. These are slated to be on a world-beating scale, forests of giant turbines standing in deeper waters, but at the eye-watering cost of well over £100bn.

Ministers argue that this will create thousands of new green jobs, cut emissions, reduce our dependence on foreign fuel and take advantage of being an island nation blessed with plenty of windy ocean.

Love them or hate them - turbines are sprouting up in a seascape somewhere near you. The question, as energy bills rise, is whether they are the right solution for Britain's consumers.