In May 2014 a world first was achieved by CSIRO, which has used solar energy to generate ‘supercritical’ steam, at the highest temperatures ever achieved outside of fossil fuel sources.

CSIRO, the Commonwealth Scientific and Industrial Research Organisation, is Australia’s national science agency. 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.

A solar thermal power plant typically consists of a large number of mirrors, called heliostats, which reflect the energy from the sun onto a central tower. The plant then generates electricity the same way that most of the world’s electricity is produced, namely by heating water to create steam, to turn a steam turbine. However the breakthrough that CSIRO have achieved is the combination of pressure and temperature they have managed to achieve in the steam. This being 235 bara and 570 deg C. Existing 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 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.

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, currently only driven by coal or gas. Around 90% of Australia’s electricity is generated using fossil fuels. CSIRO are also developing advanced solar storage to provide solar electricity at any time, day or night.

Although this project using supercritical steam is still being developed for commercialisation, it is a significant achievement and one which brings solar thermal energy a step closer to cost competitiveness with fossil fuel generated power. The future of steam is clearly bright, in many different ways.

All images in this article copyright CSIRO