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Could molten metal help solve renewable energy's storage problem?

Joseph Flaig

Stock image (Credit: iStock)
Stock image (Credit: iStock)

Molten metal could help solve a key issue with renewable power by storing energy efficiently and cheaply, researchers have claimed.

A team at Georgia Tech’s Woodruff School of Mechanical Engineering in the US created a ceramic-based mechanical pump able to operate at temperatures of more than 1,400oC. They claimed the device, which transfers incredibly hot liquids such as molten tin, could facilitate a new generation of energy conversion and storage systems.

As wind and solar power boom worldwide, grid operators and governments are still searching for efficient electricity storage methods for when the sun is not shining and the wind is not blowing. The Georgia researchers said the scorching temperatures enabled by the temperature-resistant ceramics and graphite seals could efficiently store energy, with generated electricity heating the metal and then being tapped from the heat energy when needed.

“Until now, we've had a ceiling for the highest temperatures at which we could move heat and store it, so this demonstration really enables energy advances, especially in renewables,” said mechanical engineer Asegun Henry. “The hotter we can operate, the more efficiently we can store and utilise thermal energy. This work will provide a step change in the infrastructure because now we can use some of the highest-temperature materials to transfer heat.”

Challenging the assumption that brittle ceramics are not suitable for pumps, Henry and Caleb Amy, the first author of the research paper, built a small prototype device with rotating gear teeth to suck in liquid tin and push it out of an outlet. The pump ran for 72 hours with several hundred revolutions per minute, at an average temperature of 1,200oC and a peak of 1,500oC.

The pump used gears just 36mm in diameter, and the total heat transferred was limited to 10kW. However, the researchers claimed that increasing the pump dimensions by four or five times and operating near its top speed could increase the total transferable heat by a factor of a thousand.

The technique could provide relatively low-cost energy storage, claimed Henry. “This would allow us to create a new type of battery,” he said. “You would put electricity in when you have an excess, and get electricity back out when you need it.”

However, energy storage expert and engineer Dénes Csala from Lancaster University, who was not involved in the research, said the technology has a long way to go before commercialisation.

“There is good potential in this, but it’s very, very nascent,” he told Professional Engineering. “We have only seen a lab experiment so far – which has gone well so far – but we have to see much bigger lab experiments, on a much bigger scale where we actually start talking about useable quantities of power.”

The research was published in Nature

Content published by Professional Engineering does not necessarily represent the views of the Institution of Mechanical Engineers.

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