A CSIRO breakthrough is raising the efficiency of solar thermal power production.

4 June 2014 — A  breakthrough technology by CSIRO has made solar thermal energy a step closer to cost competitiveness with fossil fuel generated power.

The CSIRO’s high-temperature, or supercritical, steam innovation enables the most efficient turbines powered by steam produced from burning coal to be one day be powered by steam generated by solar energy. And given solar thermal’s ability to store energy as heat, the project team is also getting closer to developing technology that can produce power 24 hours a day.

CSIRO solar thermal research leader Robbie McNaughton told The Fifth Estate, “We have achieved what we set out to achieve, which is to replicate the conditions in a state of the art turbine power plant,” said Mr McNaughton.

The result could be described as similar to a cleaner, greener way to boil a big kettle, he said.

“The vast majority of the world’s electricity is produced by steam, even in nuclear power plants.

“What we will do next is start on the path of making the system robust. We will basically start putting it through daily cycles of heat and cool down, which is very [intense] for the steel [components]. No-one knows what the impact of the cycle on the steel will be. We have also discovered the supercritical water is very corrosive.”

The method is based on the physics of boiling water, which boils at higher temperatures under pressure. The supercritical approach applied a pressure of 23.5 megapascals and then heated the water to 570 degrees Centigrade using solar energy – and the team actually set a world record for highest temperature reached for boiling water.

The solar heating process was made more effective through another CSIRO innovation, which is a unique method of controlling the solar energy through making adjustments as to where the sun hits the heliostat (mirror) array.

Australia only has a small number of coal-fired power plants that use supercritical steam. McNaughton said these types of plants have a 40 per cent efficiency, compared to a standard coal fired plant, which works at around 35 per cent efficiency.

Commercial solar thermal power plants around the world use subcritical steam, operating at similar temperatures but at lower pressure. If these plants were able to move to supercritical steam, it would increase the efficiency and help to lower the cost of solar electricity.

The $5.8 million research project was funded by the Australian Renewable Energy Agency, and a spokesperson for the organisation said this soon-to-conclude project, and a related project on solar thermal energy storage technologies, have not had their funding cut in the recent federal budget.

“Everything that’s been committed to in terms of projects [before the budget], that money is locked in,” the spokesman said.

“There are 180 projects currently funded by ARENA which will not be affected.”

The research is part of a broader collaboration between CSIRO and Abengoa Solar, a leading global supplier of solar thermal electricity in the world. The related project, developing advanced solar storage for electricity, will continue for some months, and Mr McNaughton said molten salt technology, which is currently being used in Spain, is a promising example of what is possible.

The breakthrough was made at the CSIRO Energy Centre, Newcastle, which has two solar thermal test plants featuring more than 600 mirrors (heliostats) directed at two towers housing solar receivers and turbines.

ARENA chief executive Ivor Frischknecht acknowledged the research team’s significant achievement, saying it demonstrated the importance of research and development.

“This breakthrough brings solar thermal energy a step closer to cost competitiveness with fossil fuel generated power,” Mr Frischknecht said.

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