South Australia Approves World’s Largest Single-Tower Solar Thermal Plant

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The world’s largest single-tower solar thermal plant has gained approval to be built near Port Augusta, South Australia. The plant will join the recently opened world’s largest battery in solidifying the state’s position as a global leader in renewable energy. In combination, the two could be a game-changer in terms of perceptions of the viability of electricity supplies built around solar and wind.

Solar thermal power involves focusing sunlight, ultimately boiling water to drive turbines to produce electricity. Many different versions have been tested since it originated over a century ago using intermediaries to store the heat before production. Progress has been slow while the search for the optimum design continues.

In the meantime, photovoltaic (PV) panels have leaped ahead, leading many to question whether solar thermal energy will ever have its day in the Sun. Solar thermal is far less flexible than PV since it only works at large scales, is more affected by clouds, and is currently much more expensive.

Solar thermal does, however, have one big advantage over PV – it facilitates storing energy as heat, which can be used to generate electricity at night or whenever it is needed most. South Australia has some of the highest reliance on wind power in the world – over 50 percent in 2016-17 – and a long-running campaign has pushed to complement this with solar thermal, which can be ramped up when the wind dies down.

While the Australian federal government has fiercely backed coal, the South Australian government has gone the other way. To address the fluctuations caused by so much wind and solar, it famously had Tesla install the world’s biggest battery late last year, which has already saved the Australian grid from malfunctioning several times thanks to its millisecond response to frequency instability. The state also recently opened the world’s first farm running on seawater, which uses solar power to remove the salt.

The new plant, to be built by SolarReserve, should add to this stability. The 150-megawatt plant is expected to provide 4 percent of South Australia’s electricity, displacing gas and reducing coal-derived energy from other states. Although smaller than existing multi-tower facilities, it is being described as the largest single unit.

The plant will consist of 12,000 mirrors focusing light on a 220-meter (700-foot) tower, where molten salts will be heated to 565ºC (1,050ºF), with heat exchangers transferring this to water.

Only solar thermal engineers would describe salt at 288ºC as “cold”. SolarReserve

The South Australian government has described the AU$650-million (US$490-million) plant as the “cheapest option” for supplying the government’s energy contract, beating fossil fuels and other renewables with battery storage.

Solar thermal is never likely to be suitable for cloudy locations, but supporters hope diminishing costs will allow it to dominate electricity production in sunny regions.

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