But there are hundreds of other ideas that go beyond technical innovation, ideas about how we organise and run our society or the way we live our lives, that can have a dramatic impact on millions of people.

The abolition of slavery, votes for women, universal health care are all examples.

So what are the big ideas of the 21st Century? This series looks at some of the most ambitious schemes currently being dreamt up.

Viewers can then decide – is this a stroke of inspired genius or a hopeless pipedream?

In September 2004, Amory Lovins and his team of scientists, engineers and economists at the Rocky Mountain Institute published a detailed step by step blue-print for achieving an oil-free America by 2050.

It was a serious piece of work, co-sponsored by the Pentagon and peer-reviewed, but despite an initial flurry of press reports his ‘big idea’ seemed destined to remain just that – an idea.

Five years later, however, and his idea is on the brink of going mainstream. Last July Al Gore joined the cause, challenging the United States to end its reliance on fossil fuels by 2018.

Generating 100% of the country’s electricity needs from renewable sources, he said, was a goal that was both achievable and affordable.

A new President has embarked on a raft of policies to reduce America’s global warming emissions. Is it conceivable that Obama could eventually sign up to even more radical measures?

In a film for BBC World News, Amory Lovins lays out his grand plan. He sets out the technical solutions that are already there, what Government has to do, what industry has to do and what American consumers can expect. Along the way we hear from fellow enthusiasts and sceptics as he tries to sell his vision.

By the end, the viewer can decide – inspired genius or a futile pipedream?