Concentrating solar power – what is it?

Last night I was reading through the Beyond Zero Emissions summary report, the one which lays out a plan for Australia to move to 100% renewable energy by 2020. Their plan relies lots of energy efficiency to cut back on the amount of baseload we need. Then we switch to nearly 40% wind power, which we’re all familiar with, and on nearly 60% ‘concentrating solar thermal’, which I had to look up.

CST is really interesting technology. As you might guess from it’s name, it’s a type of solar power. But instead of photovoltaic panels, it uses mirrors to reflect sunlight at a tower. You could use this energy to heat water, to drive a steam turbine to generate electricity the same way old-fashioned coal plants do.

But the Beyond Zero plan relies on molten salt storage technology being attached to the tower. It’s exactly what it sounds like – the heat and energy are used to keep salt hot instead of water. Then the molten salt can be stored until it’s needed, at which point its heat is transferred to water for the turbines.

You can read all about the technical details on Wikipedia – concentrating solar power, solar power towers, and molten salt. Or just take a peek at this illustration from the Beyond Zero report:

Solar Power Tower: click to open full size in a new window

There’s a commercial CST electricity plant already running in Spain – the PS10 – and another one in the USA – the Sierra Sun Tower. They don’t have the salt storage though. And there are other operational concentrating solar projects around the world too.

The way Beyond Zero tells it, CST in Australia could be run as follows:

• 12 solar power tower sites across Australia
• each site approximately 15km x 15km
• total land required about the size of Kangaroo Island, or a couple of Northern Territory cattle stations
• only using 12% of the water needed for conventional coal plants
• costs 5 – 6 cents per kilowatt hour after all sites complete (comparable to coal now)
• costs $175 billion to set up (about 2% of our current GDP)
• as much of the labour and components to be sourced from Australia as possible, to create jobs.

It’s a fascinating idea and I really like it. It’d need a really strong committment from the government to see it though, but then again, so would any solution to our dirty energy problems. What do you think?