Molten Salt May Be Solution to Solar Energy Storage

June 29th, 2008 by Carol Gulyas

While adoption of solar energy steps up around the world, two key challenges remain: how to store the energy created during the day so it can be used through the night and how to dispatch the energy to where it is needed. Both of these problems may be solved by coupling molten salt with concentrating solar power (CSP), according to a June 26 article in Renewable Energy World.

You will recall from previous CleanTechnica postings that CSP technology concentrates the sun’s power to create steam, which turns a turbine to make electricity. But how did molten salt get into the picture?

“Terry Murphy, Chief Executive Officer for SolarReserve, who along with others helped develop the molten salt technology at Rocketdyne. ‘Molten salt is a heat storage medium that retains thermal energy very effectively over time and operates at temperatures greater than 1000°F, which matches well with the most efficient steam turbines. Second, it remains in a liquid state throughout the plant’s operating regime, which will improve long-term reliability and reduce operation and maintenance costs. And third, it’s totally ‘green,’ molten salt is a non-toxic, readily available material…..'”

Molten salt storage was a key component of the Solar Grand Plan, published in Scientific American in December 2007, which outlined a plan to supply 69% of U.S. electricity and 35% of its total energy by 2050. The Grand Plan, written by By Ken Zweibel, James Mason and Vasilis Fthenakis, proposes molten salt storage concentrating solar, among other proven technologies, and calls for an aggressive plan of government subsidies to allow solar energy to compete fairly with oil and other fossil fuels.

About the Author

Carol Gulyas Carol Gulyas is a leader in the renewable energy community in Illinois, where she serves as VP of the Board of the Illinois Solar Energy Association. Recently she co-founded EcoAchievers -- a provider of online education for the renewable energy and sustainable living community. She spent 18 years in the direct marketing industry in New York and Chicago, and is currently a teaching librarian at Columbia College Chicago. Carol grew up in a small town in central Indiana, then lived in the Pacific Northwest, Lima, Peru, and New York City. She is inspired by reducing energy consumption through the use of renewable energy, energy efficiency, and green building technology.

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Gangbang rocks!
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http://www.PlanetThoughts.org David – green thoughts

It looks like “kent beuchert” and “kerry beauert” seem to be the same person. I am surprised the names chosen were so similar. But what really gives it away is that they make almost identical points, with identical writing styles. I guess there is strength in numbers, whether real or fictitious….
http://www.PlanetThoughts.org David – green thoughts

It looks like “kent beuchert” and “kerry beauert” seem to be the same person. I am surprised the names chosen were so similar. But what really gives it away is that they make almost identical points, with identical writing styles. I guess there is strength in numbers, whether real or fictitious….
Keith

Kent: You don’t really understand what you are talking about. For starters, there is nothing more reliable than wave energy. There is, so far, no large scale demonstration (that I know of), however it has been proposed to provide the major power source for the desalination plant to be built in Victoria, Australia. This is hardly a base-load application, however it has also been proposed for base-load application in Australia’s far north west for the entire City of Broome where huge tidal differences would make its application almost trivial.

Furthermore, Molten-Salt Reactors may be just the thing to rescue the Nuclear industry. There is currently a 1000MWe design with proposed commissioning in 2025 (according to Wikipedia). Solar Thermal can deliver that much quicker than 2025.

Wind farms are doing quite nicely supplying power to many remote Australian towns and a large percentage of some European countries. In fact, why do you claim that they are unreliable? In fact why do you claim any of these technologies are unreliable? They are providing electricity into the grid that would otherwise have to be provided by fossil (or nuclear) fuels, thus reducing the need for the fossil fuel. No one is claiming that the existing state of these technologies is ready to replace fossil fuels entirely. Keep in mind however that, in Australia at least, coal is much cheaper than say solar. But ONLY BECAUSE OF THE HUGE GOVERNMENT SUBSIDIES THAT COAL OPERATORS ENJOY. Give those subsidies to the renewable energy providers and the picture changes entirely.

Joe: #1 Don’t know. The Solar Tower in California has been using Molten Salt for years. Don’t know what its duty cycle is or the Molten Salt capacity.

Joe: #2 I would suspect that when engineers build a Molten Salt Heat Exchanger they would figure out a containment vessel and heat exchange pipes that would stand up to the corrosion problem. Glass? Ceramic? Molten Salt does not necessarily mean table salt. Some compounds may be less corrosive than others.

Molten Salt as heat storage for solar thermal has been proposed at least as far back as the 1960’s to my knowledge (work done at University of Arizona, can’t recall the researcher’s name).

Molten Salt is used in the ZEBRA battery which is currently being used to directly replace Lead-Acid batteries in submarines where they *eliminate* corrosion problems. The ZEBRA is also being developed for automobiles.
Keith

Kent: You don’t really understand what you are talking about. For starters, there is nothing more reliable than wave energy. There is, so far, no large scale demonstration (that I know of), however it has been proposed to provide the major power source for the desalination plant to be built in Victoria, Australia. This is hardly a base-load application, however it has also been proposed for base-load application in Australia’s far north west for the entire City of Broome where huge tidal differences would make its application almost trivial.

Furthermore, Molten-Salt Reactors may be just the thing to rescue the Nuclear industry. There is currently a 1000MWe design with proposed commissioning in 2025 (according to Wikipedia). Solar Thermal can deliver that much quicker than 2025.

Wind farms are doing quite nicely supplying power to many remote Australian towns and a large percentage of some European countries. In fact, why do you claim that they are unreliable? In fact why do you claim any of these technologies are unreliable? They are providing electricity into the grid that would otherwise have to be provided by fossil (or nuclear) fuels, thus reducing the need for the fossil fuel. No one is claiming that the existing state of these technologies is ready to replace fossil fuels entirely. Keep in mind however that, in Australia at least, coal is much cheaper than say solar. But ONLY BECAUSE OF THE HUGE GOVERNMENT SUBSIDIES THAT COAL OPERATORS ENJOY. Give those subsidies to the renewable energy providers and the picture changes entirely.

Joe: #1 Don’t know. The Solar Tower in California has been using Molten Salt for years. Don’t know what its duty cycle is or the Molten Salt capacity.

Joe: #2 I would suspect that when engineers build a Molten Salt Heat Exchanger they would figure out a containment vessel and heat exchange pipes that would stand up to the corrosion problem. Glass? Ceramic? Molten Salt does not necessarily mean table salt. Some compounds may be less corrosive than others.

Molten Salt as heat storage for solar thermal has been proposed at least as far back as the 1960’s to my knowledge (work done at University of Arizona, can’t recall the researcher’s name).

Molten Salt is used in the ZEBRA battery which is currently being used to directly replace Lead-Acid batteries in submarines where they *eliminate* corrosion problems. The ZEBRA is also being developed for automobiles.
Joe

MOLTEN SALT at 1000 F is the same temperature that the big Coal fire plants run. What I want to know about Molten salt is.

#1. How much Molten salt will we have to store at 1000 F to produce say 1000 mag watts for say 14 hours? That would keep this Power Plant running until the sun came up the next day. Are we talking about a 5 or 10 Million Gallon tank?

#2. What kind of Steel pipe is going to hold up to salt? and how long will the system last before the Molten salt eats holes through the steel?

By the way I think this is one of the best Ideas out there.

Joe in Florida
Joe

MOLTEN SALT at 1000 F is the same temperature that the big Coal fire plants run. What I want to know about Molten salt is.

#1. How much Molten salt will we have to store at 1000 F to produce say 1000 mag watts for say 14 hours? That would keep this Power Plant running until the sun came up the next day. Are we talking about a 5 or 10 Million Gallon tank?

#2. What kind of Steel pipe is going to hold up to salt? and how long will the system last before the Molten salt eats holes through the steel?

By the way I think this is one of the best Ideas out there.

Joe in Florida
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http://solarenergynewsandreview.blogspot.com/ Kevin

several assumptions are off here. cloudy days still generate heat, especially with solar concentrators. the key is to be able to produce electricity with lower temperatures. there are some co-gen products that can produce electricity with temps as low as 200 degrees. also the assumption that subsidies are necessary for alternative energy to be successful is just wrong. government subsidies go to the highest bidder. just look at the ethanol debacle. price pressure will drive true innovation. we need to get the government out of the energy business all together.
http://solarenergynewsandreview.blogspot.com/ Kevin

several assumptions are off here. cloudy days still generate heat, especially with solar concentrators. the key is to be able to produce electricity with lower temperatures. there are some co-gen products that can produce electricity with temps as low as 200 degrees. also the assumption that subsidies are necessary for alternative energy to be successful is just wrong. government subsidies go to the highest bidder. just look at the ethanol debacle. price pressure will drive true innovation. we need to get the government out of the energy business all together.
Solar God

Yes, solar is the perfect peaking source and now it looks like it can also be used as base load. New nuclear is now being estimated to cost 30 cents per kwh and the US is more dependent on imported uranium than imported oil. This in not a solution to anything. We must use fuel sources that we have available where the power is needed: wind, geothermal, hydro, and the sun.
Solar God

Yes, solar is the perfect peaking source and now it looks like it can also be used as base load. New nuclear is now being estimated to cost 30 cents per kwh and the US is more dependent on imported uranium than imported oil. This in not a solution to anything. We must use fuel sources that we have available where the power is needed: wind, geothermal, hydro, and the sun.
Daleus

High salt content water has long been used by micro heat exchange builders.

Where I live, there are next to no manufacturers of alternative energy systems, so many of us tired of waiting for big business and big government to get their act in gear, have had to find alternatives.

I know several people who have build salt water ponds to fuel a heat exchange system. Simply, put the pond has a clear top that lets in the light and warms the salt solution. Piping then runs through the salt pond, picking up heat and transferring to either a solar boiler or to an old fashioned water and rock filled heat sink.

It works remarkably well.
- http://rebbeca.com rebeca
  
  watt do u call a solution when its in a solution
Daleus

High salt content water has long been used by micro heat exchange builders.

Where I live, there are next to no manufacturers of alternative energy systems, so many of us tired of waiting for big business and big government to get their act in gear, have had to find alternatives.

I know several people who have build salt water ponds to fuel a heat exchange system. Simply, put the pond has a clear top that lets in the light and warms the salt solution. Piping then runs through the salt pond, picking up heat and transferring to either a solar boiler or to an old fashioned water and rock filled heat sink.

It works remarkably well.
Sol Shapiro

Right on. We need to get those tax credits for solar renewed for the long term. There’s enough going on in the west now that with such tax credits it will become apparent in 5 years whether the solar thermal world will be on the path to be the backbone of our electrical energy supply. My guess is that it will achieve its goal.
Sol Shapiro

Right on. We need to get those tax credits for solar renewed for the long term. There’s enough going on in the west now that with such tax credits it will become apparent in 5 years whether the solar thermal world will be on the path to be the backbone of our electrical energy supply. My guess is that it will achieve its goal.
kerry beauert

Carol Guyas is somewhat confused. Molton salt storage does not mean that soalr thermal is a reliable energy source, only that it is more grid-friendly and produces more highly valued power than either wind, wave or solar PV power, all of which are basically useless because of their inability to meet peak demand, AT ANY TIME. Solar thermal can meet peak demand , BUT ONLY WHEN THE SUN HAS PROVIDED THE ENERGY. Even the sunniest deserts in the U.S. are cloudy 30 days of the year and obviously will not be providing power every day of the year either. Of more interest is why people such as Gulyas are trying

so hard to push obviously immature and very expensive technologies like solar thermal and others, all of which are unreliable and have the expensive side effect of requiring that their capacities be duplicated by reliable power plant construction. They also, by their vaiability can increase emissions by 15% because of the need for their varying power input

to be mirrored by reliable (fossil) power.
kerry beauert

Carol Guyas is somewhat confused. Molton salt storage does not mean that soalr thermal is a reliable energy source, only that it is more grid-friendly and produces more highly valued power than either wind, wave or solar PV power, all of which are basically useless because of their inability to meet peak demand, AT ANY TIME. Solar thermal can meet peak demand , BUT ONLY WHEN THE SUN HAS PROVIDED THE ENERGY. Even the sunniest deserts in the U.S. are cloudy 30 days of the year and obviously will not be providing power every day of the year either. Of more interest is why people such as Gulyas are trying

so hard to push obviously immature and very expensive technologies like solar thermal and others, all of which are unreliable and have the expensive side effect of requiring that their capacities be duplicated by reliable power plant construction. They also, by their vaiability can increase emissions by 15% because of the need for their varying power input

to be mirrored by reliable (fossil) power.
kent beuchert

I find it disturbing that apparently intelligent people would believe that having a 16 hour storage capability “makes solar thermal energy reliable.”

What it actually does, of course, is make any electricity that it may generate available during critical peak hours, something that primitive wind energy cannot do. In that sense it’s miles ahead of wind and wave, but it is NOT in fact reliabble. Even in our sunniest regions, 30 days a year are cloudy and therefore solar thermal plants will not produce any electricity for over 30 hours, regardless of any storage capabilities they may have. Reliable power plants will have to step in to replace all the power that was lost. So even though solar thermal plants

can shift their power output by a number of hours, a day’s sun lost is a day’s power lost and therefore solar is almost as unreliable as the others. But not quite, since the grid operators will know well in advance that power will not be available if clouds prevail. Solar thermal is therefore grid-friendly than the PV solar crap or wind crap or wave crap. But the additional costs (which alternative energy “experts” never admit to) that each year the power demand goes up, additional reliable (i.e. fossil fueled) plant capacity wil have to be built as well. That is a gigantic side effect cost that’s never entered into the calculations when pricing costs. And compresed air for storing energy is rather idiotic – it reqiires the burning of enormous amounts of natural gas to warm the compressed air. Such energy storage invalidates any claim by wind operators that their technology is carbon free and their massive subsidies of 2 cents a kWhr(which would completely pay for a kWhr of nuclear energy)

should be withdrawn.
kent beuchert

I find it disturbing that apparently intelligent people would believe that having a 16 hour storage capability “makes solar thermal energy reliable.”

What it actually does, of course, is make any electricity that it may generate available during critical peak hours, something that primitive wind energy cannot do. In that sense it’s miles ahead of wind and wave, but it is NOT in fact reliabble. Even in our sunniest regions, 30 days a year are cloudy and therefore solar thermal plants will not produce any electricity for over 30 hours, regardless of any storage capabilities they may have. Reliable power plants will have to step in to replace all the power that was lost. So even though solar thermal plants

can shift their power output by a number of hours, a day’s sun lost is a day’s power lost and therefore solar is almost as unreliable as the others. But not quite, since the grid operators will know well in advance that power will not be available if clouds prevail. Solar thermal is therefore grid-friendly than the PV solar crap or wind crap or wave crap. But the additional costs (which alternative energy “experts” never admit to) that each year the power demand goes up, additional reliable (i.e. fossil fueled) plant capacity wil have to be built as well. That is a gigantic side effect cost that’s never entered into the calculations when pricing costs. And compresed air for storing energy is rather idiotic – it reqiires the burning of enormous amounts of natural gas to warm the compressed air. Such energy storage invalidates any claim by wind operators that their technology is carbon free and their massive subsidies of 2 cents a kWhr(which would completely pay for a kWhr of nuclear energy)

should be withdrawn.
- Uriel Ayala
  
  This is true for just one solar power plant at an specific location. Try four or five plants separated by 50 or 100 miles apart and the scene changes. The probability of having most of them under a cloud will turn to be better that the probability of a conventional fosil fuelled plant to be down by an electrical or mechanical failure.