Two towers almost a kilometer high have been announced for Wuhan, China. But they won't just be special because of their height - the towers will actually clean the polluted lake next to which they will sit.

At 830m high the Burj Khalifa has been the world's tallest building since 2010. However, these days that record seldom lasts long. UK architects Chetwoods are proposing to go for the full 1000m.

Tall buildings require a lot of power, particularly for lifts, but Adele Peters of business magazine Fast Company reports “Wind turbines, lightweight solar cladding, and hydrogen fuel cells running on the buildings’ waste will generate all of the power used by the towers, plus a little extra for the rest of the neighbourhood.”

Moreover, the designers propose to tackle Wuhan's notorious pollution. "The towers also have pollution-absorbing coatings to help clean the air, vertical gardens that filter more pollution, and a chimney in the middle of the larger tower naturally pulls air across the lake for better ventilation,”says Peters.

“The water goes up through a series of filters,” explains architect Laurie Chetwood. “We don’t use power to pull the water up, we’re using passive energy. As it goes through the filters and back, we’re also putting air back into the lake to make it healthier.”

Only the taller tower will have a wind turbine, allowing it to not only meet its own energy needs, but supply power to the other tower as well.

The timelines for the project are astonishingly tight, with construction proposed to start this year (despite mayor approval still being required) and completion in 2017 or 2018. By contrast the Burj Khalifa took six years to build from first excavation.