Plans for a one-kilometre tall “Solar Tower” that would provide clean energy for up to 200,000 homes have been approved by the Australian government. But some environmental campaigners are questioning the practical benefits of the scheme.

The 130 metre-wide tower would produce electricity using currents of air heated by the Sun’s rays. The tower itself would be surrounded by a vast greenhouse, seven kilometers across. Hot air inside the greenhouse would be effectively sucked up the tower through turbines at its base.

