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Supercritical solar: CSIRO’s solar breakthrough offers new opportunities

If there is one thing Australia has in abundance it is sunlight, so the idea of harnessing that power for our energy needs is attractive. Sure, there are solar options already out there and Aussies are embracing them en masse, but the world is still very much dependent on fossil fuels. A breakthrough by the Commonwealth Scientific and Industrial Research Organisation (CSIRO) may hold the key to changing that.

In June, the CSIRO announced that it had managed to generate supercritical steam using solar energy. The CSIRO’s Energy Director Dr Alex Wonhas called it a game-changer.

“It’s like breaking the sound barrier; this step change proves solar has the potential to compete with the peak performance capabilities of fossil fuel sources.”

According to the CSIRO, supercritical solar steam is “water pressurised at enormous force and heated using solar radiation”. Wonhas noted, “Instead of relying on burning fossil fuels to produce supercritical steam, this breakthrough demonstrates that the power plants of the future could instead be using the free, zero emission energy of the sun to achieve the same result.”

Sarah Miller of CSIRO Energy Technology explained that thermal power stations produce steam that spins a turbine, which converts the steam’s thermal energy into mechanical energy to drive an electrical generator that ultimately produces electricity.

“The efficiency of the thermal to mechanical energy conversion depends on the quality of the steam,” she said. “Conventional thermal power stations using coal, gas and nuclear fuels have been improving in efficiency since the steam turbine was invented, progressing from subcritical to supercritical to ultra-supercritical steam.

“To date, concentrating solar thermal power stations have used subcritical steam, so ‘this step change proves solar has the potential to compete with the peak performance capabilities of fossil fuel sources’.”

Miller said that the uptake of concentrating solar thermal power has dramatically accelerated over the past decade. She cites the example of Gemasolar in Spain, which in 2011 was the first concentrating solar thermal power plant in the world to supply uninterrupted power for 24 hours. She said that the technology exists to really make use of concentrating solar thermal power.

Huon Hoogesteger, CEO and founder Smart Commercial Solar, said, “This is an important breakthrough, looks viable and is about centralised power which photovoltaics isn’t. It has the potential to make power stations much more efficient.”

Miller noted that there are barriers to widespread uptake of concentrating solar thermal power, namely the costs, perceived risks, and challenges of valuing the other benefits of concentrating solar thermal technologies.

The CSIRO leads the Australian Solar Thermal Research Initiative (ASTRI) which believes the cost of generating concentrating solar thermal power could be reduced from 26.5 cents per kilowatt hour to around 12 cents by 2020.

“This reduction in costs would mean that concentrating solar thermal power station would be cost competitive with traditional power plants and will be able to provide near-zero emissions electricity without destabilising the grid,” Miller said. “Concentrating solar thermal power technologies have advantages over many other renewable energy technologies because thermal energy can be stored and converted to electricity when needed, allowing dispatchable power generation.

“Concentrating solar thermal technologies can also be used to produce high quality process heat and drive chemical reactions. A future concentrating solar thermal world achievement will be 24 hour production of supercritical steam from storage.”

But, Hoogesteger said, it’s also important to recognise that one of the advantages of solar power is that solar often works best by decentralising power generation.

“You don’t necessarily want to use solar to duplicate the traditional power plant,” he said. “It’s not about just swapping out oil, coal and gas for solar, because you still have all the massive cost of power network infrastructure like transformers and power lines.

“Solar means that we need to think differently. As a result of the kind of ongoing, gradual innovation that doesn’t always get the headlines, businesses and homes can be their own power plants right now. So it would be wrong to seize on this one innovation and overlook what solar is already doing for business, government and households.”

Despite this, the CSIRO’s breakthrough represents a step forward in terms of solar as a viable option at a larger scale than previously envisaged.

Where solar will go from here remains to be seen, but it will play a role as we negotiate an increasingly post-fossil fuel-dependent energy landscape.

About the author

Freelance journalist Bianca Wright has been published in magazines and online publications around the world. A self-confessed geek and lover of all things tech, she spends her spare time searching the web for new gadgets or watching reruns of Star Trek and Firefly.

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