Spanish CSP Plant with Storage Produces Electricity for 24 Hours Straight

Lorin...

1) "store heat and produce electricity " -- this immediately means you're operating at Carnot efficiency and below, meaning at very best less than a multi-stage coal/gas-fired Brayton turbine. Heat to electricity (or any mechanical motions) suffers thermodynamic loss regardless of where the ehat comes from. That's why photonic conversion to electricity is preferred and will gradually surpass all others for solar.

2) "heat collected by a CSP plant from converting sunlight would all be dissipated as waste heat on the desert floor if it were not collected " -- wrong (quoting you), the heat wasted depends on the albedo (reflectivity of the natural surface being covered. And, it further depends on both the IR reflectivity (high for living plants) and on the visible/UV surface reflectivity. If the latter is low, indeed heat is unnaturally created by downconversion to IR. But, any natural area whose reflectivity is better than the CSP plant's overall (light-to-electricity) efficiency will be better without the plant in place.

Just because sunlight can make something hot enough to turn a generator doesn't mean the system's doing an efficient job of using that sunlight to reduce global warming. Therein lies the devil in the details of what's 'green' vs what's green.
;]

DrAlex, most domestic PV installations will be on sites subject to local pollution and having 10-20% less insolation than the desert sites selected for CSP units, where the 5-10% transmission loss is accepted to achieve higher output/square meter of collector or land used. Advanced CSP systems, such as the Senner/Torresol plant at the head of all this, can store heat and produce electricity on demand, economically. The larger capacity factor essentially pays for the storage by providing more MWhrs from a smaller turbine. PV systems are a long way from achieving 24 hour operation at any reasonable cost of batteries.
Parabolic dishes with Stirling engines do operate at high temperatures and high efficiency with air cooling so no water use, except for mirror washing, which is minor. Storage is a problem though. Tower systems have been built and tested by Germany (in Spain) using very high temperature air receivers. They work, and ceramic bed storage units have been used successfully with them. Of course, any tower system can be equipped with a Brayton topping unit. It does make the design a bit messier and more complex to operate, so few are choosing that route right now. Once tower systems are commonplace, any topping system that works with a coal fired plant can be added if society or economics calls for it.
Incidentally, in an earlier comment you complained that CSP systems were typically 15% less efficient than fossil plants, and so contributed a lot more to global warming. Wrong. The heat collected by a CSP plant from converting sunlight would all be dissipated as waste heat on the desert floor if it were not collected and 40% of it converted to electricity. On the other hand, 100% of the heat generated by a coal fired plant is new heat added to the atmosphere, on top of the CO2 contribution to global warming. You need to be a little bit fair in your attacks on large scale solar systems.

So for Geof & Steve...

1) We don't get to 90% efficiency with any remote system -- typical transmission loss is ~10%. The thermal part will never be better than 50% for the hottests fluid you can build a system to contain (<800C).

If we choose to use solar PV for the same area, we can be sure of over 40% in a few years. So, use local solar PV, called DG, and avoid the 10% permanent loss for massed remote systems. That's exactly what's afoot in many places, because it both fits with local utility distruicts and avoids control by large utilities.

2) What could be grown on the mirror farm? Well, just look at the picture f the Spanish system -- looks like at least grazing is going on around it. But no matter, because with local, non-thermal solar plus solar water heating, land waste doesn't occur.

3) Talking about pessimists & detractors when you visit your doctor and he says lower your weight/cholesterol or die? Really?

Only fools and those not caring about their descendents ignore facts. And facts are against massed solar thermal.

Geoffrey, We didn't end the stone age because we ran out of stones.
Oil is only getting more expensive by the barrel. That AGE was nice but it's almost over, and the general public is just coming to realize that. There will be numerous 'break thru's' in the near future relacing fossils with renewables. Count on it. Or kiss your --- good bye. Read about decentralizing or municipalizing our power, and get involved.(on the state and local level) It is unfortunate that we live in changing times and have little leadership at the federal level about energy.

steve-poppitz-157135: Good thinking about a hybrid system - base power solar, top off with natural gas. We will eventually get to replace much of our fossil fuel usage with renewable energy, despite all the naysayers. The route there will be littered with detractors, pessimists, oil lobbyists etc., but it will come - it MUST come. We went through silly arguments during the steam age. The population was warned that the human frame would be crushed at speeds above 12 mph (despite the fact that sprinters had run faster than that). Early road vehicles were forced to drive behind a man carrying a red flag at 4 mph, 60 yds ahead. So much time and human energy is wasted on specious arguments.

good point Geoffrey G,
which is why we should be crowding these areas with more solar power plants, experimenting and modifying, until we get huge results. What else ya gunna du , raise saltbush?

DrAlexC says "Think of the food not able to be grown on that wasted land."

Why does he assume that any food can be grown on this land? I don't know where the site is in Spain, but much of the interior of Spain is arid, stoney ground and nothing of interest grows there. Talk about "jumping to conclusions." The same applies to vast tracts of inland California, Nevada, Arizona and West Texas. Take a drive out there - there's nothing there, unless you think you can make a meal out of saltbush.

This is why I'm a fan of hybrid systems. Use the sun to get most of the way to design temperature, then add enough natural gas to get there (700 c stated above). Is there a problem with utility scale solar being only 3/4 renewable? As more of these systems are built,I'm guessing we'll get to 90% or so.

Ok Lorin, here's the deal, we have a choice -- operate at efficient temps above 700C or waste 15-20% of the input energy (regardless of source) as heat. That latter adds directly to global warming, regardless of any GHG emissions. And, add in the transmission loss of ~10% and we begin to see that conc. solar even at 500C makes little sense.

The problem with many 'renewables' is their evaluations are nearly as dishonest as coal's. At least coal/gas burning operates at hundreds of degC above what solar thermal can. And, if the plant uses no water for turbines/cooling, but the inert gas Brayton Cycle, then air cooling eliminates water issues.

Perhaps folks don't realize how important working-fluid temp is -- efficiency is never better than 1 - Tcold / Thot. Thot is the inlet temp to the turbine generators. Tcold is the exhaust temp from the generators' last stage. With steam, we lose 100C right away, because it condenses to water then. If we only start at 500C, then you can understand why a 400C differential is far less efficient than a >700-ambient is.

This knowledge of thermodynamics is real and as old as Messrs Watt, Joule, etc. Not only does a higher working temp increase efficiency and make the system consume less of all resources, a lower exhaust temp directly reduces unnatural atmospheric warming.

Steam turbines are also huge, while Brayton, inert-gas turbines starting at 700C are teeny. Everything that hurts efficiency and consumes resources makes a power source less 'green'. Solar thermal is right down there with the poorer choices.

No one is saying combustion sources are better long run, but that's not the choice to be made. We're 49 years behind on safe nuclear power and 100+ years behind on addressing global warming at all. Even in the '60s scientists were warning that we needed to eliminate combustion power or start planting a trillion new trees a year -- each person 200. How are we each doing?
;]

here here ! lorin-vant-hull,

my sentiments exactly.

I guess I just don't get it. Why must a plant burning a fuel that is free and generates no pollution (sunlight) match the efficiency of a plant that uses expensive fuel and pollutes like crazy? High efficiency requires less water use and perhaps less capital investment but it has little effect on the basic argument that we must reduce CO2 production and all the other stuff delivered by fossil and nuclear plants along with the electricity.
By the way, the mirror cleaning is covered by the 'other' 8 gal/MWh, which is a pretty small amount compared to the 500 to 750 reported for nearly all plants using wet cooling.

But, Lorin, regardless of heat-transfer fluid (it's not simply for cooling), the mirrors in all these systems need frequent cleaning via purified water. This is usually ignored, yet it not only demands more water than do other generation forms, it hides access-path construction and vehicular fuel consumption.

In contrast, not only do modern fossil-fuelled thermal plants operate at higher temperatures than 500C, they can use the Brayton Cucle for turbines, ending with air cooling -- no water needed.

That's the target solar thermal can try to match but cannot. It's also the target conventional nuclear can't match. But it's exactly the target the molten-salt reactors match, such as Thorium Fluoride systems (LFTRs).

Matching/exceeding the 40+% overall thermal efficiency of fossil plants is the key for any truly 'green' power generation. Concentrating solar of any form fails that.

OK, the Sandia report is assuming wet cooling towers for the solar plants. The references are from 1999 and 2002 when that was the only technology used. Clearly the authors did not consult the solar experts at Sandia who could have given them current data. It does report also that dry cooling for solar plants increases the cost of electricity by about 10% (a few percent loss in efficiency and some added capital cost). Essentially all plants currently in design or construction in the US desert regions use dry cooling because of the environmental impact of drawing that much water from the desert water table. Thus, the remaning water use is the 'other' reported as 8 gal/MWhr, which is undoubtedly for washing the mirrors etc.
Incidentally, the report lists the same usage for solar troughs as for solar towers, but the new generation of tower plants operate at 500C + compared to ~400C - for trough plants. The result is significantly higher efficiency and so lower water use. Surely significantly less than for nuclear which also operate at lower temperatures.
The lower water usage of some of the fossil plants is due to the high efficiency combined cycle system, which runs a very high temperature gas turbine as a topping cycle, and so can achieve overall higher efficiency (and lower cooling water use/MWhr).

but DrAlxC,
on the good side; PV prices keep going down, and efficiencies keep going up.

Right Steve, but 100+ acres of common PV is >500kW x 100 = 50MW. Assume 4hrs a day of sun and 4 x 365 x 50,000,000 is at least 1/2 of 110GWyr, with only 20% efficient cells. Military/space cells are already >40%, so beat this very high-maintenance system already. And, it can't be put on structures.

As solar PV continues its efficiency rise toward 3MW/acre, these massed systems, including wind, will be expensive jokes, much as they became in the '70s here in Calif.

Plus, they suffer all the permanent costs of distant transmission loss, failure vulnerability, and waste of valuable land. We've already used 40% of all arable land available on earth and ~100% of the water. Systems like these do nothing but acerbate that and head us nowhere toward solving how we'll feed 50% more people by 2050. Of course, they do waste heat and get subsidy $.
;]

dear DrLexC, I'm surprised at your responce. Don't get me wrong, I'm all in favor of PV on existing structures. BUT, they claim to get 110 GWh / yr. from this tower, and they compare that to 40 GWh / yr. in a similar PV project. I'm hopeful.

How wasteful -- about 150 acres and all they get is 20MW -- 130kW/acre. Solar PV on existing structures gets 600kW/acre now, right near the loads. And, PV's present 20% efficiency is on its way up to another doubling or so.

Think of the food not able to be grown on that wasted land. Think of all the purified water needed to keep those mirrors clean. Think of the thermal inefficiency of the overnight cycle.

Someone's making subsidized $ from this, but not the Spanish people. Reality will eventually set in, as it has begun here in the US, in England, China, etc.

Assuming operation was at full rated capacity, this is truly an impressive accomplishment, and something that should quiet the fossil naysayers for a while.

The statement in the news release is a bit misleading, as Solar Two, the 10 MWe molten salt central receiver at Barstow, CA operated continuously on the grid for 153 hours in July of 1998. They did cheat a bit, as the storage was only rated at 3 hours, so they de-rated the turbine down to 1.1 MWe at night to extend operating hours, and continued at that level the next day until the storage was full. The test was terminated by a cloudy day which prevented recharging storage, but the plant was back to full capacity operation the next day.

back to the topic.

It uses a "molten salt and heat transfer fluid". Well, are these terribly expensive? Are they rare and unavailable? Mirrors, piping, pumps and heat-exchangers all seem readily available...right? If we aren't running out of these "ingredients" I can't see why we don't build 100 of these this year, from LA to Dallas and back. About 100GWh / year vs. 40GWh / year for more PV...I bet this is a hands down winner.

PaulFelixSchott seems to think that Archimedes ( 287 BC – 212 BC) invented the laser. Only out by about 2,200 years. Bad history, bad physics and bad English.

You really believe it is a joke? How's that werkin out fer yah?

Phil, dooood, you're taking this way too literally. It's a pun, a sarcastic play of words.

Since you're older than the Great Wall of China, you'll certainly remember that in the US everything boils down to a war of some kind; war on drugs, war on terrorism, war on obesity, war on communism, Civil War, Spanish War, Mexican War, Star Wars, WWI, WWII, Panama, Vietnam, Afghanistan, Iraq, the works. Do you get the joke now?

VMH

Wonderful accomplishment!

VMH No.3, What can be demonstrative about seeing everything in terms of madness and war? I am already seeing that the investment gurus are stiring the pot of competition and lack to generate profits for them to skim. What is wrong with a new peaceful paradigm in energy provision? All that has been spent in support of wars on earth could have benefitted people much more when shared to elevate all those who have less or are in need. Has not the prevalence of suffering and destructive conflicts throughout the history of the world shown the futility of war? There is NOthing in a presumed Christian society that supports war, yet how often we react in this self destructive way.

We are on the threshhold af an entirely new way to BE in the world through peaceful means of abundance for all. Let not the least among us, (perhaps politicians), teach us that constant conflict is the way. Each of us has a far more enlightened teacher available to our mind that those who would teach a belief in lack and dominance is important or needed.

When I was a child, I thought as a child. When I became older, I remembered not to laugh at childish imaginings, and believed them real. Now, in the evening light of grace my mind hears yet another Voice of Peace and True Abundance for all. I am always free to choose again, and see the truth of my choice.

Archimedes of Syracuse a Brilliant Mathematician, Engineer,Inventor, Physicist, Astronomer and one of the Smartist Scientist ever on Earth. Build the First ever very powerful Sun Powered Laser Ray Amplifying the Sun's Energy to make a beam of Light Energy so powerful his Laser Beam Ray set Ships on Fire that Attacked Syracuse in day light.
Today thanks to Albert Einstein and Northrop Grumman The United States Of America can stop any aircraft or tank with a Laser. Power from the SUN i pray this is put to good use for all on earth. All Leaders on Earth need to start to not just look at Solar energy put to start useing it. For the Good of all.
GOD Bless and may he Guide the Good at Heart
The Lord's Little Helper
Paul Felix Schott
solardowork@yahoo.com

Awesome! Good for you, Spanish friends!

Now, if us gringos could get p-o'ed and start a renewable energy war against the Spaniards and show'em we can do better, wouldn't that be an awesome win-win war worth fighting for?

VMH

Hope these type of plants will help Solar Energy to become Mainstream Power soon. The cost has to come down with more capacity gets commissioned like the price of Solar PV whose price is now around $1/Wp This cost is very much more reported clese where as close to $18/W

This is an important milestone for concentrating solar thermal electric technology.

But way back in 1981 we visited the salt gradient solar pond electric plant at Ein Bokek on the edge of the Dead Sea -- which even then was capable of generating electricity for much more than 24 hours from storage.

The nearby 5 MWe plant at Bet Ha'Arev (near ancient Jericho) was officially switched on by the Energy minister at midnight a few months later, and could generate for several times 24 hours from storage. These plants had low cost, but also low overall (solar-to-electric) energy efficiency, and I do not know whether they are still operational.