CSIRO has used solar energy to generate hot pressurised “supercritical” steam, at the highest temperatures ever achieved in the world outside of fossil fuel sources.
Supercritical steam is a breakthrough for solar energy, and means that one day the sun could be used to drive the most advanced power stations in the world, that are currently only driven by coal or gas.
CSIRO’s Energy Director, Dr Alex Wonhas said this milestone is a game-changer for the renewable energy industry.
“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.
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.”
The world record, set in May this year, was at a pressure of 23.5 megapascals (a measure of force per unit area), equivalent to being 2 kilometres under the ocean’s surface, or about 100 times as high as the pressure in car tyres, and temperatures up to 570°C, which is around the point where aluminium alloy would start melting.
As impressive as that is by itself, this is the first time solar power has ever been used to create these “supercritical” levels on this scale, previously only ever reached using the burning of fossil fuels.
Solar thermal, or concentrating solar power (CSP) power plants have traditionally only ever operated at “subcritical” levels, meaning they could not match the efficiency or output of the world’s most state of the art fossil fuel power plants. Supercritical steam is performed at a much higher pressure, when you boost pressure the efficiency is also boosted, leading to lower costs.
The $5.68 million research program is supported by the Australian Renewable Energy Agency (ARENA), and is part of a broader collaboration with Abengoa Solar, the largest supplier of solar thermal electricity in the world. CSIRO and Abengoa, with support from ARENA, are developing advanced solar storage to provide solar electricity at any time, day or night.
The breakthrough was made at the CSIRO Energy Centre, Newcastle, home to Australia’s low emission and renewable energy research. The centre includes two solar thermal test plants featuring more than 600 mirrors (heliostats) directed at two towers housing solar receivers and turbines.
They have developed a fully automated control system which predicts the heat delivered from every mirror, allowing them to achieve maximum heat transfer, without overheating and fatiguing the receiver. With this amount of control, they were able to accurately recreate the temperature and pressures needed for supercritical success.
ARENA CEO Ivor Frischknecht acknowledged the significant achievement saying it demonstrates the importance of research and development.
“This breakthrough brings solar thermal energy a step closer to cost competitiveness with fossil fuel generated power.”