Investment in environmentally sound sources of energy has risen nearly five-fold in the past four years, according to analysis by New Energy Finance, the consultancy. In 2004, investment in the sector stood at just over $33bn. Last year, it was more than $148bn.

The massive scale of investment has thrown up huge opportunities for entrepreneurs and a bewildering variety of new companies has sprung up, many startlingly unfamiliar to those in traditional energy businesses.