Unexpected Application: Liquid Metal Pump For Better Solar Power Efficiency

© AP Photo / Xinhua, Liu XiaoWorkers check solar panels in Yulin, northwest China's Shaanxi Province, as the traditional mineral-resource-rich city turned its development on clean energy industries such as wind power or solar power
Workers check solar panels in Yulin, northwest China's Shaanxi Province, as the traditional mineral-resource-rich city turned its development on clean energy industries such as wind power or solar power - Sputnik International
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A newly-designed pump intended to work with liquid metal at extreme temperatures just found an unexpected application in solar power plants.

A new hydraulic pump has been invented recently by a team of researchers from the Georgia Institute of Technology, Stanford, and Purdue University, according to a report by Ars Technica. Several new technological solutions allow for the pump to operate at extreme temperatures of 1,673K (approximately 1,400 degrees Celsius).

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This is pretty cool (no pun intended), considering that existing pumps can only operate at temperatures up to 1,300K (1,027 degrees Celsius), after which they either break or become chemically unstable.

The new pump, made of ceramics, graphite, tungsten and a material called Shapal, "a machinable aluminium-nitride-rich composite," has been precision-designed to accommodate the material expansion that happens in extreme heat — the whole device has reportedly expanded about 1mm vertically during tests.

The machine worked without failure for 72 hours without breaking, researchers reported, noting that the temperature ceiling of 1,673K was established because their heater could not give more, therefore, the real cap is yet to be determined.

Now, instead of metallurgy, researchers using the material have turned their gaze toward solar power. How are these two processes connected?

The answer comes from SolarReserve's 110 MW Crescent Dunes, an enormous solar energy installation in the state of Nevada, in which a tower housing a reservoir of molten salt heated by a whole lot of mirrors called "heliostats" that reflect the sunlight onto the superheated mineral, which then powers a steam turbine that generates electricity.

​Why molten salt? Because this substance is a good heat carrier. Hydraulic pumps drive the heated liquid salt from the reservoir toward heat exchangers where water becomes steam to further rotate turbines to generate electrical power.

The challenge is that liquid salt has a temperature of ‘only' 566 degrees Celsius. Recent studies found that molten salt can be replaced with liquid tin, which has a much higher level of thermal conductivity and can be used while heated at 1,400 degrees Celsius, momentarily increasing the heat transfer coefficient by "two to three orders of magnitude," Ars Technica reports.

That's where the new pump comes in handy.

The pump makers estimate that using molten metals and their invention will allow for "a relative increase in efficiency of approximately 50 percent" at concentrated thermal solar plants, "reducing costs by 20-30 percent."

There is still work to be done. After those 72 hour tests gears "experienced visible wear," so a design alteration will be required to make the pump reliable for long term use.

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