Novel composite can handle heat and pressure of concentrated solar power

Solar power currently accounts for less than 2% of US electricity, but could make up much more if the cost of electricity generation and energy storage for use on cloudy days and at night-time were cheaper. A team led by scientists at Purdue University has now developed a new material and manufacturing process that could make one way of using solar power – as heat energy – more efficient for generating electricity.

This innovation is an important step towards putting solar heat-to-electricity generation in direct cost competition with fossil fuels, which currently generate more than 60% of electricity in the US.

"Storing solar energy as heat can already be cheaper than storing energy via batteries, so the next step is reducing the cost of generating electricity from the sun's heat with the added benefit of zero greenhouse gas emissions," said Kenneth Sandhage, professor of materials engineering at Purdue University.

The research, which was conducted at Purdue in collaboration with scientists from the Georgia Institute of Technology, the University of Wisconsin-Madison and Oak Ridge National Laboratory (ORNL), is reported in a paper in Nature.

Solar power doesn't only generate electricity via panels in fields or on rooftops. Another option is concentrated power plants that run on heat energy.

Concentrated solar power plants convert solar energy into electricity by using mirrors or lenses to concentrate a lot of light onto a small area, generating heat that is transferred to a molten salt. Heat from the molten salt is then transferred to a ‘working’ fluid – supercritical carbon dioxide – causing the fluid to expand and spin a turbine to generate electricity.

To make solar-powered electricity cheaper, the turbine engine would need to generate even more electricity for the same amount of heat, which means the engine needs to run hotter. The problem is that heat exchangers, which transfer heat from the hot molten salt to the working fluid, are currently made of stainless steel or nickel-based alloys that get too soft at the desired high temperatures and at the elevated pressure of supercritical carbon dioxide.

Inspired by materials his group had previously combined to make ‘composite’ materials that can handle high heat and pressure for applications like solid-fuel rocket nozzles, Sandhage worked with Asegun Henry, now at the Massachusetts Institute of Technology, to develop a similar composite for more robust heat exchangers.

Two materials showed promise together as a composite: the ceramic zirconium carbide and the metal tungsten. Purdue researchers created plates made of this ceramic-metal composite. The plates host customizable channels for tailoring the exchange of heat, based on simulations of the channels conducted at Georgia Tech.

Mechanical tests at ORNL and corrosion tests at the University of Wisconsin-Madison helped show that this new composite material could be tailored to successfully withstand the high temperatures and pressures needed for generating electricity more efficiently than today's heat exchangers. An economic analysis by researchers at Georgia Tech and Purdue University also showed that these heat exchangers could be manufactured at comparable or lower cost than existing stainless steel- and nickel alloy-based heat exchangers.

"Ultimately, with continued development, this technology would allow for large-scale penetration of renewable solar energy into the electricity grid," Sandhage said. "This would mean dramatic reductions in man-made carbon dioxide emissions from electricity production."

This story is adapted from material from Purdue University, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.