Published: 21 October 2018 14:04:17
Researchers have developed a material that can be used to harvest electricity from the sun's heat, which provides ways to generate less expensive solar power during cloudy days and at night. Innovation is an important step for solar thermal power generation in direct competition with fossil fuels, researchers say.
"Storage of solar energy because heat can already be cheaper than saving energy through batteries, so the next step is reducing the cost of generating electricity from the sun's heat with the added benefit of greenhouse gas emissions," says Kenneth Sandhage, Professor at Purdue University in the United States. Concentrated solar power plants convert solar energy into electricity using mirrors or lenses to concentrate a lot of light on a small area, which generates heat that is transferred to a molten salt.
Heat from the molten salt is then transferred to a "working" liquid, supercritical carbon dioxide, which expands and works to rotate 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 that transfer heat from the hot melt salt to the working fluid are currently made of stainless steel or nickel-based alloys that become too soft at the desired higher temperatures and at elevated pressure of supercritical carbon dioxide. Researchers thought of a ceramic zirconium carbide and metal tungsten composite for more robust heat exchanger. They created ceramic metal composite plates. The plates are customizable channels to customize heat exchange.
Mechanical tests and corrosion tests showed that the composite material could be tailored to meet the higher temperature, high-pressure supercritical carbon dioxide needed to generate electricity more efficient than today's heat exchanger.
An economic analysis also showed that the upgraded manufacturing of these heat exchangers could be performed at comparable or lower cost than for stainless steel or nickel-based. "In the end, with continued development, this technology would allow large-scale penetration of renewable solar energy into the grid," said Sandhage. "This would mean dramatic reductions in human CO2 emissions from power generation," he said.
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