It looks like a set from a sci-fi epic – but this solar plant in the scorching Nevada desert has a far more practical purpose.
High in the stark Nevada desert – a couple of hundred miles north-west of Las Vegas is the shimmering circular mirage of Crescent Dunes.
Ten thousand silvery glass panes – each measuring 115 square metres – surround a tall central tower – which stands like a twinkling needle in the featureless landscape around it.
Resembling a fabulous alien metropolis Crescent Dunes is in fact a highly sophisticated mile-and-a-half-wide solar power plant – ‘the next generation in solar energy’ according to Kevin Smith one of the project’s founders.
The glass panes which comprise a combined area of more than a million square metres are not photovoltaic (PV) panels like those installed on rooftops and in solar farms worldwide.
Instead they are simply vast multifaceted mirrors which track the course of the sun like heliotropic plants.
This field of mirrors harnesses and concentrates the blazing Nevada sunshine – directing it precisely towards the top of the central tower.
‘The difficulty with photovoltaic is that it’s intermittent’ says Smith who is CEO of Crescent Dunes’s parent company SolarReserve.
‘When the sun goes down you’re done’.
‘Engineers have long sought methods of storing solar energy – in water – in batteries – in fluid-filled ‘parabolic troughs’ – but Smith claims that Crescent Dunes demonstrates ‘the world’s most advanced energy-storage technology’ known as molten-salt storage.
The central tower secretes a reservoir of potassium and sodium nitrate – about 25,000 metric tonnes of it – heated in advance to 288°C – at which temperature the mixture is a clear water-like liquid.
This is circulated in narrow thin-walled tubes- rising dramatically in temperature when exposed to the fearsome concentrated sunlight at the top of the tower.
‘We heat it to 560°C’ says Smith ‘it flows back down the tower and we capture it in a large tank’.
(ed:..now..isn’t that cool..?..)