Arizona solar plant achieves six hours after sun goes down

I'm still waiting for these new solar plants to begin production of Hydrogen to be stored as fuel for later use, rather than outputting electricity directly into the grid. That way we can begin to build up our Hydrogen infrastructure by being able to produce decent amounts. The only downside I see to this, is these plants may begin to use up precious water in these dry sunny regions of the world.

I'm still waiting for these new solar plants to begin production of Hydrogen to be stored as fuel for later use

We'd need a hundred odd more of these plants before there's any point in talking about synthetic fuels being produced. Turning the energy to hydrogen would be a massive waste at this point because it would accomplish pretty much nothing.

The plant already stores 1.7 GWh worth in electric output, which is not bad at all. Four such installments would replace a single medium size coal power station completely with power to spare, which means they're on the same order of magnitude with conventional power generation. In practice, two might be enough for the typical load factor of a power plant.

Three more downsides:
1) Splitting water to get hydrogen is not a 100% efficient process.
2) Storing hydrogen needs either a lot of space, as a gas, or a lot of energy as a liquid.
3) Hydrogen is extremely flammable and, if mixed with air, explosive.

We'd need a hundred odd more of these plants

At 2bn a pop that doesn't sound so bad. And Arizona alone would have more than ample places to put them.

Hydrogen is extremely flammable and, if mixed with air, explosive.

That's sort of the point.

Some lomg term energy storage solution will need to be added in the future to counter variability. But that, also, doesn't seem like an insurmountable obstacle.

Sorry, we'll have to stick with coal because this solar silliness can't supply steady power to other planets, and is a subversive plot to replace our freedoms with socialism. ;) ;)

"Why not both?" Look, on one hand solar's great for providing electricity to stationary objects. On the other, solar energy stored through chemical means (natural/artificial photosynthesis, catalyzed electrolysis of water) is really useful for providing fuels that can be consumed by mobile objects (vehicles, even mobile devices with handheld fuel cells). There's a lot of progress being made on all of these fronts, and so we're not being over reliant on any one source, horray!

Splitting water to get hydrogen is not a 100% efficient process. ?

Multiple breakthroughs in Water splitting have already been reported by Dr. Nocera of MIT (his students research group) and at least two other Nano-materials split water cheaply. I'm sure with a quick search on You Tube or Phys.org you'll find an article or two that is peer reviewed.

...Multiple breakthroughs in Water splitting have already been reported by Dr. Nocera of MIT

From http://web.mit.ed...930.html :

At present, the leaf [Nocera's water-splitting device] can redirect about 2.5 percent of the energy of sunlight into hydrogen production in its wireless form; a variation using wires to connect the catalysts to the solar cell rather than bonding them together has attained 4.7 percent efficiency

Subtract from this efficiency the 60% efficiency of a fuel cell and you get 1,5 to 3% total solar to electricity efficiency. This is very far from the 20% efficiency of a thermal solar plant!

Hydrogen electrolysis from water is technology that will see the end someday in the near future.

http://www.prweb....8185.htm

efficiency and cost of feed stock will rule the day in hi vol. 1H future.

IEEE Spectrum refers to Gila Bend, Arizona, as a "solar power wonderland," with four solar plants approved in the area.

A hot ass hell hole is what it is, a wide spot in the road on the way to San Diego.

IEEE Spectrum refers to Gila Bend, Arizona, as a "solar power wonderland," with four solar plants approved in the area.

A hot ass hell hole is what it is, a wide spot in the road on the way to San Diego.

Well, as the saying goes, there's no place to go but up.

IEEE Spectrum refers to Gila Bend, Arizona, as a "solar power wonderland," with four solar plants approved in the area.

A hot ass hell hole is what it is, a wide spot in the road on the way to San Diego.

Gila Bend, in Google, for the curious. https://maps.goog...amp;z=12

IEEE Spectrum refers to Gila Bend, Arizona, as a "solar power wonderland," with four solar plants approved in the area.

A hot ass hell hole is what it is, a wide spot in the road on the way to San Diego.

@cantdrive, did you learn this by driving there, or did you go through on a bus? Or are you just dissing solar power by whatever means available?

A hot ass hell hole is what it is, a wide spot in the road on the way to San Diego.

What better place to put it in? The spot doesn't seem to be in comeptition for farming, living space or an abundance of fauna and flora that needs preserving.

All the speculation about hydrogen producing efficiency aside, hydrogen is just not a feasible automotive fuel. It takes too much space, it's very dangerous, and it's hard to store and transport.

So it's a huge red herring to talk about hydrogen as a means to store solar energy. There are better ways to do it for stationary purposes, like what they're already doing here, and you would have to come up with a more practical solution for mobile use so the hydrogen would be an intermediary at best.

The Fraunhofer institute in Germany already has power to methane processing plants. Methane - natural gas - is much more useful than raw hydrogen.

IEEE Spectrum refers to Gila Bend, Arizona, as a "solar power wonderland," with four solar plants approved in the area.

A hot ass hell hole is what it is, a wide spot in the road on the way to San Diego.

@cantdrive, did you learn this by driving there, or did you go through on a bus? Or are you just dissing solar power by whatever means available?

My statement didn't say a thing about solar, I was just commenting on what a hot ass shitty town Gila Bend is, just dissing a podunk town in AZ. I grew up in PHX area, drove through GB many many times via I-8 on way to SD, I'm intimately knowledgeable of the wasteland. And AA has a point, good spot for solar.

Sorry, we'll have to stick with coal because this solar silliness can't supply steady power to other planets, and is a subversive plot to replace our freedoms with socialism. ;) ;)

Looks like some dummie took you seriously...

Anyone have an accurate and complete energy budget comparison of thermal oil to eutectic salt storage?

Anyone have accurate and complete energy budget comparisons for at scale solar thermal, and solar hydrogen compared to at scale solar photovoltaic with molten salt battery storage?

With these energy budgets we can produce and economic feasibly analysis.

The answers to my above questions pretty much limits much of the opinions and discussions herein and much of the R&D being done by some clueless entrepreneurs. Without those answers it makes further discussion pretty much a waste of time. Obviously, I don't have the answers either, but at least I know the questions.

All the speculation about hydrogen producing efficiency aside, hydrogen is just not a feasible automotive fuel.
...
So it's a huge red herring to talk about hydrogen as a means to store solar energy. There are better ways to do it for stationary purposes, like what they're already doing here,

Why do you equate storage of hydrogen with an automotive fuel? That doesn't make sense in this context.

The point to use hydrogen is that you can store it indefinitely (unlike the solar heat in the thermal energy storage unit in this plant). This way you can tide over the occasional cloudy day or rainy season - which this type of plant can't.

To replace the old energy producing methods alternative energy powerplants need to be able to produce power 24/365 - with full adaptability to demand spikes and independent of external factors like weather. Solar powerplants need the ability to store up significant amounts of power somewhere.

All the speculation about hydrogen producing efficiency aside, hydrogen is just not a feasible automotive fuel. It takes too much space, it's very dangerous, and it's hard to store and transport

"...in late 2007, Ballard pulled out of the hydrogen vehicle sector of its business to focus on fuel cells for forklifts and stationary electrical generation... Research Capital analyst Jon Hykawy concluded that Ballard saw the industry going nowhere and said: "In my view, the hydrogen car was never alive. The problem was never, "Could you build a fuel cell that would consume hydrogen, produce electricity, and fit in a car?" The problem was always, "Can you make hydrogen fuel at a price point that makes any sense to anybody?" And the answer to that to date has been "No.""

The Fraunhofer institute in Germany already has power to methane processing plants. Methane - natural gas - is much more useful than raw hydrogen

"On 24 February 2010, Sridhar [Bloom Energy] claimed that his devices were making electricity for 8–10 cents/kWh using natural gas, cheaper than today's electricity prices in some parts of the United States, such as California Twenty percent of the cost savings depend upon avoiding transfer losses that result from energy grid use... Bloom claims a conversion efficiency of around 50%"
http://www.bloome...el-cell/

Looks remarkably like someone's Solar Farmville plot.

I smell a conspiracy formulating in some Tea-Tard brain.....

Sorry, we'll have to stick with coal because this solar silliness can't supply steady power to other planets, and is a subversive plot to replace our freedoms with socialism. ;) ;)

Looks like some dummie took you seriously...

I'm the target of bots and sockpuppets, no matter how innocuous the post. If I posted that the moon is not really made of green cheese, I'd get a 1 rating from them.

IEEE Spectrum refers to Gila Bend, Arizona, as a "solar power wonderland," with four solar plants approved in the area.

A hot ass hell hole is what it is, a wide spot in the road on the way to San Diego.

@cantdrive, did you learn this by driving there, or did you go through on a bus? Or are you just dissing solar power by whatever means available?

My statement didn't say a thing about solar, I was just commenting on what a hot ass shitty town Gila Bend is, just dissing a podunk town in AZ. I grew up in PHX area, drove through GB many many times via I-8 on way to SD, I'm intimately knowledgeable of the wasteland. And AA has a point, good spot for solar.

Solar and wind both need to be set in places where they need the construction jobs, there are not too many people to object, where agricultural land isn't taken and where important ecosystems are not disrupted. Picking that area looks like a bright idea. (pun intended)

Why do you equate storage of hydrogen with an automotive fuel? That doesn't make sense in this context.

I didn't. It was simply the rationale given for producing hydrogen.

The point to use hydrogen is that you can store it indefinitely (unlike the solar heat in the thermal energy storage unit in this plant). This way you can tide over the occasional cloudy day or rainy season - which this type of plant can't.

That's why I said you need four of these to replace a single conventional powerplant.

What's four times six hours?

The energy loss rate from the thermal storage can be made arbitrarily small if we want to, because the surface area to volume ratio of the system drops the larger you make it. That is, it becomes easier to insulate.

In contrast, there is no container that can hold the pressure of boiling liquid hydrogen, so loss by venting is inevitable. Gaseous hydrogen, again, takes immense volumes to store meaningful amounts of energy.

For example, a cubic meter of gaseous hydrogen at NTP contains just 12.7 MJ of energy, and that's the high heating value which is not concerned with the need to heat the other combustion gasses as well. Out of that, you can expect to get a third out in the form of electricity, so one cubic meter of gas is worth roughly 1 kWh and a bit.

So, in order to output the daily production of a 280 MW powerplant, you would need 6.72 million cubic meters of hydrogen gas, compressed to some meaningful yet manageable pressure.

Let's say you store it at 100 bars in high strenght steel tanks. That's still 67,200 cubic meters of space. If the tanks were tubular and one meter in diameter, three meters tall and laid in a square grid, they would take up a field of roughly 2 acres, access roads and all. There would be about 7200 individual tanks.

And I wouldn't want to be anywhere near when one blows up. It would probably wipe out the whole field of mirrors with it.

"And I wouldn't want to be anywhere near when one blows up. It would probably wipe out the whole field of mirrors with it." - Eikka

Explosive chemical oxidation is quite limited unless the oxygen is built into the fuel. Rapid combustion in air is limited by available oxygen and once a small volume is devoid of oxygen by the initial distribution of air and fuel, combustion only takes place a turbulent surface boundary between new fuel and new air.

After the initial pop who's size is dependent on the extent and completeness of the fuel/air mixture before ignition, R**3 you get a whoosh as the remainder of the fuel burns at a rate that is sub proportional to R**2.

In terms of expansion rate, R grows sub/linearly due to the time needed to accelerate the fuel to the velocity of the burn surface, and due to the pressure exerted by the expanding gas at that surface on the fuel yet to burn.

and like that there.

For those interested in very big and very low cost explosions, dump a fuel truck of gasoline, mix in a tanker of LOX, wait a minute and light a match.

Isn't that right Otto?

The energy loss rate from the thermal storage can be made arbitrarily small if we want to, because the surface area to volume ratio of the system drops the larger you make it. That is, it becomes easier to insulate.

In contrast, there is no container that can hold the pressure of boiling liquid hydrogen, so loss by venting is inevitable.

By that logic hydrogen is superior because you only have a single point of venting. E.g. Type 212 type submarines use liquid hydrogen as a fuel for their silent running operations and can stay submerged for 3 weeks. If venting were a problem that couldn't be achievable.

And I wouldn't want to be anywhere near when one blows up.

And you wouldn't want to be anywhere near the gas tanks dotting the landscape. Fortunately solar powerplants are in the middle of the friggin' desert - so you don't have to be near them. The damage would be very local and very inconsequential.

By that logic hydrogen is superior because you only have a single point of venting.

The rate of heat transfer into the vessel determines the rate of venting, so the problem with molten salt and liquid hydrogen is exactly the same - proper insulation - although hydrogen also diffuses through materials under pressure, so you got an additional loss there.

The submarine uses the venting hydrogen continuously to stay submerged, so the venting is not a problem, whereas it would be if you wanted to store energy for months without using or losing it.

The damage would be very local and very inconsequential.

The total loss of a 2 billion dollar solar facility is not "incosequential".

Explosive chemical oxidation is quite limited unless the oxygen is built into the fuel. Rapid combustion in air is limited by available oxygen and once a small volume is devoid of oxygen by the initial distribution of air and fuel, combustion only takes place a turbulent surface boundary between new fuel and new air

The initial blast of a gas leak explosion, or the destruction of a single tank in a field of hydrogen tanks serves as the dispersing charge of a fuel-air explosive device (thermobaric bomb), which have very large area effects due to the amount of atmosphere they displace.

The initial blast physically throws the fuel around and disperses it before it has a chance to be ignited, and hydrogen is the perfect fuel for this purpose because its rate of diffusion is very high, and it explodes over a very wide range of air-to-fuel ratios (7-75%) which means the mixture doesn't have to be very homogenous to get a blast going.

In terms of efficiency and cost, the heat storage method is still more economical than the hydrogen storage method, because the production and pressurization/liquefaction of hydrogen consumes a significant portion of the energy contents.

Beyond that, the two systems are similiar because the hydrogen is then converted to heat to drive turbines, which is a more cost-effective way than using fuel cells.

And since the solar facility operates by heat, it would lose 90% of the energy first in conversion of heat to electricity and then to hydrogen, and then back to electricity - compared to simply storing the heat in the first place and then making electricity out of that.

In effect, storing the heat gives you approximately three times more output than storing hydrogen.

For those interested in very big and very low cost explosions, dump a fuel truck of gasoline, mix in a tanker of LOX, wait a minute and light a match.

Isn't that right Otto?

Sounds like VD and his jihadi buddies are planning something. Who should I call VD? That's ok I'm sure they already know. You guys always trip up unless you're SUPPOSED to succeed.

God bless Empire.

total loss of a billion dollar facility

Again you discount engineer superpowers. They are well-versed in blast mitigation and damage-limiting construction.

...Beyond that, the two systems are similiar because the hydrogen is then converted to heat to drive turbines, which is a more cost-effective way than using fuel cells. ...

This will be a very silly way to use hydrogen! Fuel cell are at least twice as efficient as turbines!

This will be a very silly way to use hydrogen! Fuel cell are at least twice as efficient as turbines!

They aren't.

A combined cycle turbine achieves higher practical efficiencies than fuel cells, and requires less exotic materials, making it cheaper overall.

Again you discount engineer superpowers. They are well-versed in blast mitigation and damage-limiting construction.

I would like to see how much more it costs to blast- and shrapnel-proof three square miles of mirrors.

Also, how much higher your insurance costs are going to be with a couple acres of highly volatile gas on the premises.

And remember, that's only the start. If we're talking about using hydrogen for long term storage, 24 hours worth is not enough. Strategic reserves for energy have to last for weeks if not months.

-Are you saying they cant separate the storage system from the mirrors? It would be much harder to design an H2-producing setup that would destroy an entire complex, than not. Usually the first thing engrs think of is zoning and cutoff valves to isolate damage.

But I would probably think of looking through this first:

"The 2011 NFPA 2: Hydrogen Technologies Code is a brand new document that consolidates all the fire and life safety requirements applicable to generation, installation, storage, piping, use, and handling of hydrogen in compressed gas form or cryogenic liquid form into a single comprehensive resource."
http://www.nfpa.o...5Ftest=1

Also, how much higher your insurance costs are going to be

You talk as if you think nobody has ever considered these things. H2 is routinely used in industry and labs. Insurance underwriters publish standards and do design evaluations long before ground is broken.

whereas it would be if you wanted to store energy for months

The storage time needed for 100% alternative energy (mix of solar, hydro, biogas and wind) for full grid stability all year round is 3 days. 7 max if you cover all worst case scenarios.

The reason you don't have the issues as with fossil fuels is that you're not dependent on resources in countries that might decide to cut you off for political reasons. There's no more need for a strategic reserve. Also such a system is very much resistant to any kind of sabotage. It's really hard to blow up the number of solar power plants or eggbeaters to make a dent in energy production.

The total loss of a 2 billion dollar solar facility is not "incosequential".

Compared to the several hundred billion that Fukushima costs (construction, cleanup and decomission) - it is.
Also there is no reason to have the hydrogen tanks exactly on site. Electricity can be conveyed by these newfangled 'wires'. Fascinating tech.

The storage time needed for 100% alternative energy (mix of solar, hydro, biogas and wind) for full grid stability all year round is 3 days. 7 max if you cover all worst case scenarios.

Grid stability is one thing, stockpiling energy for security reasons and to account for seasonal variations in energy production and demand is another thing.

If you're going to be producing energy in the south and transmitting it north, you're going to have to ramp up your output in the winter when the demand goes up, and store your excess in the summer when the demand is low.

Compared to the several hundred billion that Fukushima costs...

But we're not making that comparison, and you're making a tu-quoque fallacy in pulling that argument.

Also there is no reason to have the hydrogen tanks exactly on site.

The hydrogen conversion and storage facility is not exactly free either. Point is, if you only need 3 days worth, molten salt will do better than fine.

The reason you don't have the issues as with fossil fuels is that you're not dependent on resources in countries that might decide to cut you off for political reasons. There's no more need for a strategic reserve.

There are many reasons, such as natural disasters like hurricanes mowing down a couple percent of your off-shore wind power, which would leave you in a deficit for years before you can rebuild and recover. Some years, you may have 10-20-30% less water power than previous years, or why not similiar yearly fluctuations in wind power. Maybe a bad year for biofuel crops.

If you're living hand-to-mouth with your energy policy with just a couple days to spare, you're going to run out of energy sooner or later.

You talk as if you think nobody has ever considered these things. H2 is routinely used in industry and labs.

Not in quantities that are measured in gigawatt-hours and millions of cubic meters. At best you have tanks measuring in a few thousand liters.

But, when accidents do happen, even with these small quantities, the results aren't pretty:

http://www.powerm...plosion/

stockpiling energy for security reasons and to account for seasonal variations in energy production and demand is another thing.

The 3 day limit already accounts for seasonal variation.
Security resaons? What security reasons would those be? It's not like you can contaminate an area by blowing up a solar power plant (or even a hydrogen storage tank)

Point is, if you only need 3 days worth, molten salt will do better than fine.

I don't think it will keep that long. Molten salt has the problem that if it ever goes solid in the pipes you can throw away your entire system. It's only good for very short storage soutions.

As for H2 tank safety: Even if you puncture one it'll burn off (at worst. Unless you ignite it it'll just escape).
H2 isn't falmmable if there is no oxygen (and since tank is at overpressure none can enter)

... Molten salt has the problem that if it ever goes solid in the pipes you can throw away your entire system. ...

You can simply keep the salts liquid with a natural gas burner, and you'll have a backup source of energy too. Why wasting so much money with hydrogen for a couple of cloudy days a year in the desert? For what I think every thermal solar plant should have this natural gas backup.

How long after sunrise, before full power is achieved?

For what I think every thermal solar plant should have this natural gas backup.

That solution means that you're doubling (actually more than that) your power production capability. Because if the salt ever is close to solidifying you aren't generating power from it - which means you need to have powerplants to fully backup the output of your solar powerplant.
That's not economical.

Why wasting so much money with hydrogen

Hydrogen isn't exactly an expensive technology.

For now salt is good as a proof of concept (and very cheap). But I guess it's not going to be a long term solution. It's just not flexible enough.

For what I think every thermal solar plant should have this natural gas backup.

That solution means that you're doubling (actually more than that) your power production capability. Because if the salt ever is close to solidifying you aren't generating power from it - which means you need to have powerplants to fully backup the output of your solar powerplant.
That's not economical.

Depends on what you want. Just enough heat to avoid salt solidification or full power without sun? Anyway, burning hydrogen or natural gas it's exactly the same.

Why wasting so much money with hydrogen

Hydrogen isn't exactly an expensive technology.

For now salt is good as a proof of concept (and very cheap). But I guess it's not going to be a long term solution. It's just not flexible enough.

Natural gas costs far less than hydrogen, to get, to store and to burn. There are a few thermal solar plants salt based working now, not proof of concept only.

Natural gas costs far less than hydrogen,

Currently. Natural gas is a limited resource. The price for that can only go up (whereas the price for hydrogen production/storage can only go down as new tech becomes available).
Natural gas also dumps additional CO2 into the atmosphere - something we shoould try to avoid.

Anyway, burning hydrogen or natural gas it's exactly the same.

Not quite. For one you'd not burn the hydrogen but pass it through a fuel cell. The result is water (which you can store to split again when excess energy becomes available). Burning natural gas produces CO2, CO, NOx, water vapor and Sulfur compounds as there is no such thing as a perfectly clean natural gas source. So you always have the pollution/greenhouse gas issue - which is what alternative energies are supposed to fix (among other things).

Nature already figured out several great ways to store hydrogen. On earth we can't just use gravity, so nature uses chemistry:

1) Carbon Cn(2n+2)H, where n=1, 3, 4, ~6, ~~12 already have infrastructure to handle them:
n=1:methane (natural gas),
n=3:propane (liquid at moderate pressure),
n=4:butane (liquid in a plastic lighter)
n= ~6: gasoline
n=~~12: diesel

2) Alcohols (just like above but with one H replaced with an OH).
n=1: methanol (liquid and works in some fuel cells)
n=2: ethanol (party!)
n=4: butanol (liquid approaching the energy density of gasoline)

A third common biological energy storage pathway that stores significant hydrogen is sugar and starch, but its chemistry is more complex and dissolvable solids are harder to work with than liquids.

In no case does nature store significant amounts of hydrogen as H2 here on earth.

@antialias_physorg: We are talking about cloudy days in the desert! How much natural gas do you think we'll need? Ok, we will produce CO2 and water vapour (for the other pollutant you wrote about there are good filters right now, and water vapour can be condensed), but about 1% of a full natural gas power plant. The price of natural gas can only go DOWN as we find more and more gas sources. See http://www.ft.com...hi69snbz . At last, we were talking about keeping molten salts liquid. Fuel cells cannot do that.

The price of natural gas can only go DOWN as we find more and more gas sources

You think natural gas sources grow on trees? Or somehow magically replenish? As long as they are finite they'll eventually run out. Using them less will just move back that inevitable date.
We should be looking for long term solutions - not quick fixes that need quick fixes that need ....

Fuel cells cannot do that.

And they don't need to, as hydrogen storage is a REPLACEMENT for thermal salt storage.

Edit to above: CnH(2n+2), not Cn(2n+2)H.

You think natural gas sources grow on trees?

No it comes from the ground. Natural gas prices have fallen precipitously due to fracking. As it is they are being kept unnaturally high.
http://www.infomi...gas/all/

"The nation is awash in so much natural gas that electric utilities, which burn the fuel in many generating plants, have curbed rate increases and switched more capacity to gas from coal, a dirtier fossil fuel."

"The Potential Gas Committee... estimated US natural gas resources ...in 2009 raised their estimate again to 2,247 trillion cubic feet (63,600 km3) (almost 100 times current annual consumption)."

Current price oct delivery: $3.562/million btu
Barclays projected price thru 2020-2030: $4.50-5.00

-But new sources are being discovered and developed all the time, especially in developing countries, the arctic, as well as new tech for exploiting untapped resources such as methane hydrate. So barclays numbers are probably way high.

"Sounds like VD and his jihadi buddies are planning something." - RyggTard

The failed American plan.

http://en.wikiped..._destiny

"Who should I call VD? " - Otto

A suggestion...

http://www.youtub...rfNt_Jxs

@antialias_physorg:

We should be looking for long term solutions - not quick fixes that need quick fixes that need

Some century worth of natural gas resources, found now, could be enough.

Fuel cells cannot do that.

And they don't need to, as hydrogen storage is a REPLACEMENT for thermal salt storage.

This is a very bad idea.
1) To use hydrogen storage you have to use synthetic oil instead of molten salts. This is more expensive and less efficient, as molten salts can withstand a much higher temperature.
2) Instead of storing heat directly you'll have to transform heat to electricity to hydrogen to electricity again. Big loss of efficiency.
3) A big tank of molten salt is much more economical and safe then the equivalent energy hydrogen storage.

To use hydrogen storage you have to use synthetic oil instead of molten salts

How does that follow? There must be 100 different ways of storing hydrogen - and synthetic hydrocarbons is only one of those.

as molten salts can withstand a much higher temperature.

So? How is that exactly an argument for/against ... anything?

Instead of storing heat directly you'll have to transform heat to electricity

Guess what this powerplant is doing after sundown: Converting heat to electricity in a very inefficient process.

Some century worth of natural gas resources

Doesn't help with the climate issue. We should leave fossil fuels where they are.

molten salt is much more economical and safe then the equivalent energy hydrogen storage.

Since safety is probably not an issue for such out-of-the-way places (and we do use hydrogen in the industry without blowing ourselves up regularly). So what?
Economical? Not for long term energy storage. Apples. Oranges.

@antialias_physorg: Do you remember we were talking about thermal solar plants?
1) If you don't store heat you can't use molten salts, as they will go solid at night.
2) The efficiency of a thermal power plant depends on the temperature. Molten salts can withstands an higher temperature, so the whole plant is more efficient.
3) Again, we are talking about thermal solar plants, not something else! And for a thermal solar plant thermal storage is the most simple and efficient way.
4) I'll better solve now 99% of fossil burning problem at a convenient cost then keep dreaming a 100% far future solution!
5) Safety mean money! Have you an idea of how much does it costs a big hydrogen tank?
Lastly, this article is about apples. If YOU want to talk about oranges, I don't like the whole thermal solar technology, or the big centralized plants. It will be much better to have little distributed photovoltaic generators, but we need better and more economical batteries.

Store the juice in liquid metal batteries:http://www.energy...sionid=1

@Newbeak: Seem interesting, but the liquid metal needs energy (or a very good thermal insulation) to stay liquid. Let's wait and see.

The 3 day limit already accounts for seasonal variation.

No it doesn't. It accounts for less than 1% of your yearly production. Water power for example can turn out up to 45% more or less depending on the year, wind power changes 15% up and down with the seasons, and solar power, depending on your latitude, goes from 100% to almost 0 in the winter months.

I don't think it will keep that long. Molten salt has the problem that if it ever goes solid in the pipes you can throw away your entire system.

You don't even know how the system operates!

The collection system uses hot oil instead of molten salt in the tubes.

Technically, the system doesn't even need to use molten salt. You could fill the heat container with gravel and the system would work. The point of the molten salt is that it maintains a steady high temperature at the phase change point until all the salt has solidified, kinda like how water in a cup does not go below 0 degreess until it has all frozen.

Plus, it would be trivial to add heating cables or dedicated heating tubes to any pipeline that carries molten salt. Push some hot oil into a smaller diameter pipe going inside the main line, and it melts the system.

But again to the seasonal variation. Here's the stats for Phoenix, Arizona

http://assets.new.../803.gif

In the winter you get half the amount of energy you get in the peak of summer.

Here's solar flux and electricity use in Yuma, Arizona

http://origin-ars...-gr1.gif

You see the monthly income and use often don't match, with a much bigger margin than just 3 days.

@Eikka:

...solar power, depending on your latitude, goes from 100% to almost 0 in the winter months. ...

I know nobody willing to build a solar plant in Alaska, do you? The AZ data you posted shows a + or - 20% solar flux variation. Nobody can really hope to substitute all the power plants in the world with solar ones, at last not with the present technology. But we can save millions and millions tons of fossil fuels with them! Nobody will ever power up a whole city with only one plant, neither with only one kind of energy. Smart power grids and careful planning of different power plants are, and will ever be, a must.

While I am not too happy with mechanical/boiling fluid+turbine solutions, I kinda like this one. Of course its efficiency will stand of fall on the insulation of the thermal storage tank. Cold oil turns no blades, as they say. The idea of six hours is fine, given that so much of the installed base of generation facilities is fuel based, this is not selling as base power but as supplementary power. AS such, the short storage time of less than a night can be acceptable in the light of the fact that by that time, all that reserve can be sold on the power market to facilities or users downstream up or down the grid. This kind of plant would be difficult to operate without the enabling tech of control computers.

I know nobody willing to build a solar plant in Alaska, do you?

I know some people are building solar plants in Germany, which is about 50 degrees north, along with southern Canada. Think about that for a moment.

The AZ data you posted shows a + or - 20% solar flux variation.

If you want to put it that way. One of the graphs measures deviation from the average, while the other shows absolute variation, which looks to go all the way down to half the output in winter.

But we can save millions and millions tons of fossil fuels with them!

Not good enough. We need a system that is independent of fossil fuels, or it will never replace them. So far all the renewable systems have been completely dependent on the long term dispatchability of fossil fuels, and that has to change.

Solar thermal can easily have 24 hours of storage, but right now we are short of power in the evening and have excess power at night so it doesn't make economic sense to have more than 6 hours of storage. Stored solar thermal is also fairly dispatchable - more dispatchable than coal and comparable to combined cycle (efficient) natural gas power plants, but less dispatchable than peaker plants.

One could even build in days worth of storage - with hot rocks instead of molten salts the storage cost scales mostly with the surface area rather than with the volume, so longer storage could be done. In most high-sun places the highest demand for electricity is in the summer, so seasonal storage isn't needed in those areas.

Practical seasonal storage is farther in the future - it would be best with photochemical or electrochemical syntheses of fuels (probably synthetic hydrocarbons, which would solve transportation energy as well).

with hot rocks instead of molten salts

While technically feasible, it carries the penalty of efficiency because the temperature of the hot rocks changes with the "state of charge", unlike with molten salts that make use of the phase change energy of the storage medium to maintain steady high temperature.

In most high-sun places the highest demand for electricity is in the summer, so seasonal storage isn't needed in those areas.

I think the big elephant in the room is that power is needed elsewhere as well, and if we plan to make significant portions of our energy with solar power, it has to be exported north and stored seasonally.

Unless you plan on moving the entire humanity to a narrow band on both sides of the equator.

In most high-sun places the highest demand for electricity is in the summer, so seasonal storage isn't needed in those areas.

Although if you look at the graphs above, you may notice that the solar influx peak in Arizona is around april-may and the electricity demand peak happens in july-august, so there has to be some sort of seasonal shifting there already to match the two.

(apparently there's some weather effect that reduces the solar influx at june-july where the peak should be)

@Eikka - the elephant is EVENTUALLY that solar power needs to be exported north. The high-sun areas can use an order of magnitude more solar power than the have today before even needing more than 6 hours of storage, and another half-order of magnitude after that before power needs to be shipped north.

The extra winter demand in the north is also low-grade heat (especially after LED lighting is adopted), so heat pumps can greatly reduce the electricity needed for this.

As for hot rocks, with parabolic troughs such as Solana (where the solar field limits the temperature) you are correct, but solar thermal is trending toward power towers. There the molten salt limits the temperature to less than hot rocks can handle, so there the rocks provide higher (although less constant) temperature and thus efficiency.

I know some people are building solar plants in Germany, which is about 50 degrees north, along with southern Canada.

Thats a very good and very understated point.

"Germany has five times as much solar power as the U.S. — despite Alaska levels of sun... Its annual solar resources are roughly comparable to Alaska's. Just about every single region in the continental United States has greater solar potential, on average, than Germany. Yet despite those limitations, Germany has still managed to be the world leader in solar power."

-Also:
http://en.wikiped...n_Alaska

@Eikka - the elephant is EVENTUALLY that solar power needs to be exported north

Well... apparently not...

@Ghost - the solar in Germany is all photovoltaics and not solar thermal. While that is fine for the daytime peak, there is currently no generally applicable cost-effective way to store it for night-time use.

Eikka was writing about trying to get essentially all our energy CO2-neutral, which includes nights and winter, rather than merely trying to get to 100% on a bright sunny day, and my response was in that vein (that's why the 'eventually' was capitalized, as it is NOT needed at today's percentage of solar on the grid, even in Germany).

If batteries, compressed air, pumped-hydro or sun-to-fuels become economical the issues is moot, but without those solar thermal is better for storage than PV is. And Germany doesn't have good (direct) sun for solar thermal (nor does the north-eastern U.S.), and hence the comments about sending power north.

so there the rocks provide higher (although less constant) temperature and thus efficiency.

That's not what I meant.

The rocks' temperature fall as the heat reservoir is drained, so the efficiency of conversion drops the more energy you take out of it. The molten salts can be heated to very high temperatures as well, but their main point is that the phase change stores large amounts of energy at a useful temperature. It's like the difference between a zinc-carbon and alkaline battery.

it is NOT needed at today's percentage of solar on the grid, even in Germany

But that's besides the point, which was that three days worth of storage is not enough for long term dispatchability and seasonal shifting like Anti_alias claims.

And Germany is already at the point where they're producing 100% of the load with PV at the peak. Since they can't just shut everything else down, they already have to export the excess while producing a mere 3% of their total demand with PV.

Rocks such as basalt and granite can go up to 1000C, and the low-cost nitrate salt mixtures I am familiar with have melting points only up to ~500C, and decompose around 600C.
For 1-axis concentration is parabolic troughs the higher temperature doesn't matter because the solar field is limited to ~500C, so the advantage goes to the salt with its phase change.
However in two-axis concentration much higher temperatures are achievable by the solar field, and the freezing of a liter of molten nitrate salt releases ~300 kJ, which is equivalent to only a 120 degree change for basalt or 150 degrees for granite. Therefore for power towers the volumetric advantage goes to rock.

Of course rock is hard to pump (although sand is experimental-stage) so one generally needs an extra heat exchanger, but this is a fixed cost whose relevance decreases proportionately with the amount of storage.

Regarding seasonal shifting, I agree with you that thermal is not practical and chemistry is needed.

@Ghost - the solar in Germany is all photovoltaics and not solar thermal. While that is fine for the daytime peak, there is currently no generally applicable cost-effective way to store it for night-time use

Yes but nevertheless thats what people are doing.

"On a sunny day last May, Germany produced 22 gigawatts of energy from the sun—half of the world's total and the equivalent of 20 nuclear power plants. The handful of companies that make inverters, the devices that reverse the flow of electricity and feed power from rooftop solar panels back into national grids, are almost all German."

"Already, Germany's power companies are closing power plants and scrapping plans for new ones... Meanwhile, energy prices continue to sink, and solar installation continues to grow. By decentralizing power generation, the renewables boom could do to the power industry what the Internet did to the media: Put power in the hands of the little guy."

-I guess they are figuring things out.

@Ghost - the solar in Germany is all photovoltaics and not solar thermal. While that is fine for the daytime peak, there is currently no generally applicable cost-effective way to store it for night-time use

Yes but nevertheless thats what people are doing. (Plus two paragraphs)

Ghost - I don't see where the paragraphs you quoted say that people are storing the solar power for night-time use...

otto I don't see where

Well you could drop either of those paragraphs into google to find the whole article. But the fact that it is growing so fast and produces such a large percentage of the total energy consumed, means that they are accommodating it somehow.

Perhaps storage isn't the issue you think it is, at least not in Deutschland.

@Ghost - perhaps you didn't notice that I agree with you that storage isn't currently a major issue, even in Germany. For example:

as it (referring to storage) is NOT needed at today's percentage of solar on the grid, even in Germany

and more generally

The high-sun areas can use an order of magnitude more solar power than the have today before even needing more than 6 hours of storage

In 2013 solar will produce roughly 6% of all electricity consumed in Germany, (and a lower percentage than that for total energy). The discussion with Eikka was regarding the need for storage (first time-of-day shifting and then cloudy-day ride-through, and finally potentially seasonal) as the amount of solar is pushed towards 100% of all energy consumed (there are many possible contributors to solutions, only a few of which are discussed in this thread).