A recent development would make electricity generation from the sun's heat more efficient, by using ceramic-metal plates for heat transfer at higher temperatures and at elevated pressures. Source: Purdue University/Raymond Hassan

A research team from Purdue University has created a new material and a new production process that could make solar power the most efficient energy source available. The key is harnessing heat energy.

"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, Purdue's Reilly Professor of Materials Engineering.

Solar power could generate heat energy in concentrated power plants. Concentrated power plants convert solar energy into electricity using mirrors or lenses. The mirrors or lenses concentrate considerable light on a small area and generate heat, which is then transformed into a molten salt. The heat in the molten salt is transferred into a “working” fluid called supercritical carbon dioxide. The supercritical carbon dioxide expands and spins a turbine, which then creates electricity.

Turbine engines need to generate more electricity with the same amount of heat currently used to create cheap, solar-powered energy. This means that the engine needs to run hotter than the current standard.

Heat exchangers used in turbine engines are currently made of either stainless steel or a nickel-based alloy. However, these materials get too soft at the high temperatures and high pressure of carbon dioxide, leading the team to find a material that could withstand the difficult conditions.

During research, the team found two materials that could work in the environment. Ceramic zirconium carbide and metal tungsten were used to create plates of the ceramic-metal composite. The plates act like customizable channels that can be tailored for heat exchange.

Mechanical testing of the plates was done at Oak Ridge National Laboratory and the corrosion tests were conducted at the University of Wisconsin-Madison. Testing proved that the composite material could be adjusted to thrive under high temperatures and pressure. The testing also found that scaled-up manufacturing of the heat exchanges could happen with the new plates, and they would be cheaper than current heat exchanges.

"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."

The paper on the new material was published in the journal Nature.