They have captured the imagination of children, writers and even the renaissance genius Leonardo da Vinci. But beyond the fun they bring, what practical purpose do kites serve?

A handful of entrepreneurs believe they have the answer. Kites, they say, could harness untapped winds high above the earth. They could pull cables to generate electricity at a lower cost than wind turbines. Microsoft founder Bill Gates has said there is a chance – if only a one in 10 chance – that kite technology could provide a "magic solution" to some of the world’s energy needs.

These are ambitious claims. But the technology has moved a step closer to commercialisation after Kite Power Systems (KPS), a British start-up founded in 2011, received a joint £5 million investment from three energy firms, including Shell. The start-up’s plan is to build one of the world's first kite power stations using technology it believes could generate hundreds of megawatts of energy by 2030.

The technology is simple. Two kites are tethered to a spool. As they soar at speeds of around 100 miles per hour in figures of eight, they pull cables which turn the drum, rather like an unrolling spool of thread. This generates electricity. As one kite descends, the other rises, so electricity is generated continually.