An energy strategy that can take the heat

An energy strategy that can take the heat
Water and energy are tightly linked in the 21st century. Per Peterson’s research seeks to develop water-saving ways of cooling energy plants, both nuclear and solar. Credit: Peg Skorpinski

At first, it sounds ominous: Molten salts, heated to 600 or even 900 °C (about 1,700°F, pumped through the pipes surrounding a nuclear reactor. But a molten salt mixture may make a smart substitute for water to extract heat from nuclear reactors—or thermal solar power plants—and deliver it to turbines to generate electricity.

Whatever material is used to transport heat energy from a reactor, the laws of thermodynamics dictate that much of the energy is lost when the heat is turned into . When is the heat transporter, most of the energy is lost—up the cooling tower in the form of steam.

Hotter temperatures would yield greater efficiency— a godsend in regions hungry for electrical power and threatened by a shrinking water supply. But the laws of physics also dictate that when water boils and becomes vapor, higher temperature means higher pressure.

As in a car radiator, rising water pressure can threaten the pipes that contain it. At only 310°C the pressure of water circulating inside the reactor becomes more than 100 times greater than our atmosphere's pressure at the earth's surface, requiring heavy and bulky piping systems.

"The high pressure of water creates major technical challenges and limitations," says Per Peterson, professor of nuclear engineering. "Reaching higher temperatures, and making electricity more efficiently, requires new strategies."

As one of its research priorities, CERC-WET aims to advance technologies to improve thermoelectric power generation while reducing the need for water in the process. Peterson leads this effort on the U.S. side. He has been working with his counterparts at the Shanghai Institute of Applied Physics to explore and refine technology to use molten salts in both nuclear and solar energy production.

An energy strategy that can take the heat
Researchers in the UCB Compact Integral Effects Test facility, pictured here, develop high-fidelity data to validate models of molten salt effectiveness. Credit: Peg Skorpinski

Fluoride salts perform best for this purpose, he says. They melt at about 400°C but do not boil until they reach more than 1400°C.

Peterson and his Chinese colleagues focus on molten salts at about 600 to 800°C. Because the salts are nowhere near boiling at this temperature, pressure inside pipes remains low. Using molten salts to deliver heat at these temperatures can increase the efficiency of electricity production by 50 percent and reduce waste heat by half, Peterson says. Under these conditions, virtually no water would need to be consumed to make electricity.

The research is advancing rapidly. "We are spending a lot of time to see how you could couple the molten salt technology to existing nuclear reactors and to certain types of ."

A solar power strategy now in use, called concentrated solar power, focuses hundreds of mirrors on a fairly small volume of water to provide the energy to produce electricity. The plants are usually built in areas with relatively little cloud cover. But by definition, this means areas with limited water.

"We build these concentrating solar plants in places like Barstow, California, where there is a lot of sun but water is scarce. The plants have low thermal efficiency. They lose a lot of water to cooling." Heating instead of water would yield electricity much more efficiently.

Because most of the water consumption in conventional plants occurs as water evaporates into the atmosphere, CERC-WET researchers are also studying technologies to reduce the water consumed by cooling. This includes hybrid cooling methods, where advanced coatings applied to heat exchange surfaces spread water efficiently for optimal cooling, and dry-cooling methods where air-flow is regulated to eliminate the need for water completely.

Molten salts won't flow through power plant plumbing tomorrow, but Peterson thinks high-temperature molten salt technology can be demonstrated within a decade and become commercially available shortly after that, to boost clean-energy power production, save water and avert at least some of the looming resource crises.


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Citation: An energy strategy that can take the heat (2016, May 16) retrieved 24 August 2019 from https://phys.org/news/2016-05-energy-strategy.html
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May 16, 2016
You cannot run molten salts through a turbine. You need a working fluid like water.

Look up what happens when water and molten salts get together.

https://video.sea...=yhs-002

May 16, 2016
I suppose it's easy to pretend you know more than real engineers when you're already pretending to be an engineer to begin with, like gkam/george kamburoff.

May 17, 2016
Do you have anything to say? Trolls like you, hiding behind phony names are cheap, otto. And they are usually adolescents or shut-ins, folk without friends.

If you have more experience with power systems than I do, then tell us. Otherwise, please go back to high school or twitter or wherever the kids hang out.

Thanks.

May 18, 2016
Here's my name & phone, Gkam, so you can call me to discuss why you're ignorant on the subject of molten-salt reactors.
--
Dr. A. Cannara
650 400 3071

May 18, 2016
Dr Alex, Thanks. What is your investment in this technology? How is this one going to "work" when all the other promises led to Fukushima and Chernobyl?

Sorry, but in my almost 72 years, I have heard all the promises. I know the little secrets like Brown's Ferry and Fermi 1 and SL-1 which actually exploded. but was covered up.

We do not need a magic box for power, and be dependent on any Nuclear Priesthood for our power. I get mine from the roof, which is integrated with the grid, which works really well, and produces no intensely-radioactive nuclear waste.

You nuke folks took the hard classes in the hope you could provide us with power for society. But the dream has turned bad, and you are too invested in it to give up, it being a life's work.

The road led to a bad place. We have to take another.

May 18, 2016
Sorry, but in my almost 72 years
yeah it is almost impossible to teach an old dog new tricks, even more to an ancient maniac sociopath fear-monger liar.

May 18, 2016
Steam does not come from power plant cooling towers.....water entering the towers is already condensed.....might see some vapor, depending on temperature/humidity differential, much like fog.....sometime you have to wonder about the writing in these articles

May 18, 2016
Do you have anything to say? Trolls like you, hiding behind phony names are cheap, otto. And they are usually adolescents or shut-ins, folk without friends
Well I could make things up and pretend to be who and what I am not, and then pretend that the people here don't know the difference.

Like George kamburoff.

But I would be ashamed to do so and would also consider it an enormous waste of time.

May 18, 2016
"Cleckley's seminal hypothesis concerning the psychopath is that he suffers from a very real mental illness indeed: a profound and incurable affective deficit. If he really feels anything at all, they are emotions of only the shallowest kind. He does bizarre and self-destructive things because consequences that would fill the ordinary man with shame, self-loathing, and embarrassment simply do not affect the psychopath at all. What to others would be a disaster is to him merely a fleeting inconvenience."

"Conscience seems to depend on the ability to imagine consequences. But most "consequences" relate to pain in some way, and psychopaths really don't understand pain in the emotional sense. They understand frustration of not getting what they want, and to them, that is pain."

May 18, 2016
Not to mention its the pressure and the resulting expansion energy in the steam that spins the turbine, which turns the generator. As was already mentioned, the molten salts can only replace part of the water cycle in thermal power production, like the primary coolant loop in a PWR. Still need steam generators, steam turbine, condenser, cooling towers, etc....

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