Robust composite to reduce price of converting solar heat to electricity

Although the majority of solar power around the world is generated by photovoltaic panels, this is not the only method for generating electricity from the sun’s energy. Concentrating solar power is an adaptation of the oldest way of harnessing our star: the same way that greenhouses work. Large arrays of mirrors and lenses focus the sun’s rays onto a reservoir of a salt with a relatively low melting point. The hot molten salt is pumped into a heat exchanger, where it forces a working fluid to expand into a turbine, which spins to generate current. Researchers at Purdue University in Indiana have been working on the current stumbling point for the technology – the heat exchanger – and claim to have invented a new material to make this technique cheaper and more efficient.

The key to affordable concentrating solar power (CSP) is to convert as much heat as possible into electricity, which means that rather than using steam as a working fluid, it would be preferable to use supercritical carbon dioxide. The current problem is that to operate with this fluid, the heat exchangers would need to work at an extremely high temperature and pressure to cope with the conditions under which carbon dioxide becomes supercritical – and stainless steel and nickel alloys start to soften under these conditions. The Purdue team, led by professor of materials engineering Kenneth Sandhage, had previously worked on ceramic-metal composites for the exhaust nozzles of solid-fuelled rockets, and applied this experience to the heat exchanger problem.