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Solar Concentrating Plants

For a while, I have been writing that traditional silicon/germanium based solar-electric panels are not yet economic as an electricity source.

I have hopes for other technologies eventually making direct solar conversion to electricity.  However, there seems to be some activity in solar concentrating plants, where solar energy is reflected onto tubes to boil water and drive traditional steam turbines to generate electricity.  Fortune has an article on one such plant opening recently:

The completed solar arrays will be trucked to California where Ausra is building a 177-megawatt solar power station for utility PG&E (PCG)  on 640 acres of agricultural land in San Luis Obispo County. (To see a video of the robots in action, click here.) The arrays focus sunlight on water-filled tubes to create steam to drive a turbine. Ausra manufacturing exec David McKay points to where standard-issue boiler pipe will be fed into a machine and treated with a proprietary coating that transforms it into a solar receiver.

I would love for this to work, but the article goes on to say that this approach still requires federal tax subsidies to compete with other electricity sources.  I am not very familiar with the economics of such plants.  Does anyone have a link or source that delves into the economics.  I am increasingly frustrated of late with alternate energy articles that fail to give any of the relevent economic info.  For example, I read an article in the Arizona Republic (sorry, lost the link) about Arizona's first wind project, but I could not get a sense from the article if the power was being purchased at market rates or some special inflated rate.

Posted on July 29, 2008 at 10:17 PM | Permalink


Unfortunately I can't point you to any references, but a friend who did some work on similar solar projects mentioned that's there's another big environmental concern which is rarely addressed in these articles, namely water usage. The mirrors for these systems need to be washed regularly to keep them operating efficiently. This can be a big problem since the best places to locate the facilities are in deserts. Trying to balance the environmental gains from lower carbon emissions with the environmental costs from water consumption is an arbitrary decision. It's the same kind of trade off as ethanol, except with water instead of land use and deforestation issues.

Posted by: SB7 | Jul 29, 2008 11:44:20 PM

Nevada Solar 1

The data was on Nevada Solar 1, a 64MW CSP facility completed last year. The Nevada Solar 1 site covers 400 acres, and was completed last year at a cost of over 260 million dollars. Nevada Solar 1 was upon completion the third largest solar generating facility in the world. Nevada Solar 1 produced 134,000,000 kWh in a year. Assuming 8 hours a day of useful sunshine, Nevada Solar 1 averages producing 45 million KWh. This gives us a 23% capacity factor. Reported cost of 10 - 12 cents/kWh.

How? Subsidies

Note that the $260 million cost of Nevada Solar1, does not include the cost of electrical transmission lines.

If Nevada Solar 1 were scaled up to produce the equivalent annual electrical production of one AP-1000 nuclear plant, the solar power plant would occupy about 42 square miles of desert, and would cost $17 Billion. Overnight storage of heat, electrical transmission lines, and interest would carry additional costs. The 1 GW solar facility would annually consume nearly 27000 acre feet of rare desert water.

In contrast, the1.7 GW Mitsubishi's Advanced Pressurized Water Reactor (APWR) Luminant Energy is planning to build at Comanche Peak is currently estimated to cost $5-6 billion.

Solana CPS

Solana CPS facility under construction at Gila Bend, Ariz., will have a name plate capacity of 284 megawatts. The facility will cover about 1,900 acres. And its cost is piously estimated at $1 billion. No power output estimate is reported but the power will reportedly sell for 4 billion dollars over a 30 year period of time. Assuming a 23% capacity factor that we calculated from Nevada Solar 1, the daily power out put would be 24 X 280 MWs x 0.23 = 1.5456 GWh per day, the $1 billion dollar figure would appear to be proportional the Nevada Solar 1 construction costs.

Solar investment exists because of government subsidies: The government now pays 30 percent of the capitol investment costs for businesses that invest in solar power to meet our energy need.

Renewable energy production tax credit: This program gives wind, solar, geothermal and other renewable power sources a leg up with a 1.9-cent per kilowatt-hour tax credit, which makes them more competitive with natural gas or coal-fired power plants.

Posted by: Stan/Tx | Jul 30, 2008 12:13:35 AM

If "sprawl" is bad, why do eco-freaks tolerate wasting the huge amount of land these installations require?

Posted by: Bob Smith | Jul 30, 2008 1:24:05 AM

If "sprawl" is bad, why do eco-freaks tolerate wasting the huge amount of land these installations require?

Posted by: Bob Smith | Jul 30, 2008 1:25:27 AM

If "sprawl" is bad, why do eco-freaks tolerate wasting the huge amount of land these installations require?

Posted by: Bob Smith | Jul 30, 2008 1:25:33 AM

First, here's the link to the AZ Republic's article:

Ariz. to get first wind-power farm

Second, here's another company that's developed a solar collection-type method for power production, based in Phoenix with a couple of large projects underway in California - their technology ought to appeal to your inner mechanical engineer.

Posted by: Ironman | Jul 30, 2008 6:32:23 AM

I love it!

"The completed solar arrays will be trucked ..."

Will that show up in the cost accounting?

What happens when sage brush or kangaroo mice become endangered species?

Posted by: Larry Sheldon | Jul 30, 2008 9:22:51 AM

Newspapers no longer exist to give useful information.

For example, if you read about wildfires in California, do they show a map of the fire? No, instead they fill up their text with interviews with victims.

As for engineering numbers... a Masters in Journalism from Columbia does not require one significant math or math-based science course. These folks are uneducated in anything that matters.

Posted by: John Moore | Jul 30, 2008 9:31:19 AM

@Bob Smith: If "sprawl" is bad, why do eco-freaks tolerate wasting the huge amount of land these installations require?

Because there will be no eeevil humans living where the installations blight Gaia. To ecotards, there is nothing as menacing as a tidy community of family homes.

Posted by: skh.pcola | Jul 30, 2008 9:57:20 AM

Instructions for "Conservatives" arguing against Alternative Energy

It's important that you frame the debate so that no alternative to current conventional sources is possible. Here is what you must do:

1. First, ignore the orders-of-magnitude larger subsidy for conventional energy sources.

In federal spending, conventional energy receives 29 times more funding than renewables. If you want to count what the economists call "externalities" the World Resources Institute (wri.org) says that the subsidy for petroleum alone in the U.S. is $300 billion annually. This includes things like the depletion allowance (a tax write-off from oil producers) and defending essential overseas pipelines and oilfields -- and WRI's figure is pre-Gulf-War-I.

2. *Never* mention that the cheapest alternative "fuel," is already competitive with conventional sources: conservation. Certainly *never* mention the lack of interest by Wall Street in funding things like nuclear, even with 100% subsidies. (see http://www.democracynow.org/2008/7/16/amory_lovins_expanding_nuclear_power_makes)

By concentrating on the inadequacy of things like radioactive cat farts as an alternative fuel, you are certain to make eco-freaks look ridiculous. Suggested statement: "And where are we going to get the water to treat the cat farts? Eh, Mr. Smarty-pants Eco-Freak?!"

3. Sell the story that it's legitimate to compare a mature industry that has literally hundreds of years to refine its engineering and distribution -- one that burns a fuel that stores the ancient sunlight of millenia -- with some infant industry's product that tries to store the sunlight (or wind, etc.) from a single day. In other words, try to make petroleum and other conventional sources compete on a level with renewables (and don't mention conservation!!!)

Speculate about why this infant can't beat up the equivalent of a heavyweight fighter. Cluck your tongues at the foolishness of eco-freaks. Why don't they get a clue?! Why aren't their solutions as elegant and economically correct as conventional sources? OK, so the Germans are refining their solar technology because they're subsidizing it, but will that really help them corner the market in the future?

4. Ask disingenuous questions that attempt to insult your opponents with name-calling. For example: "If 'sprawl' is bad, why do eco-freaks tolerate wasting the huge amount of land these installations require?"

Ensure you ignore the obvious that a) Sprawl requires large populations of commuters burning gas on the road, of necessity, while solar power plants don't, b) environmental reviews are actually preventing many solar installations from being built, and c) the question compares apples and oranges.

5. Whatever you do, compare these renewables installations to nuclear which is bound to be cheaper. Do *not*, however, mention the egregious off-books subsidy of the Price-Anderson act that makes the U.S. government the insurer of last resort for nuclear plants. Do *not* mention that, if they're so safe, why aren't any private insurers offering to cover them? Do *not* mention that none would be built without insurance. And, especially, do *not* mention that peak uranium is slated to be 2050 unless we build a lot of nuclear plants. Then it will be 2015.

I think if you follow these instructions, everything should be jake, and you will get your thank-you prize from Exxon.

Posted by: Yoshdad | Jul 30, 2008 10:15:15 AM

Yoshdad: everything you wrote is as foolish as your last point. "Peak uranium?" Perhaps you have never heard of breeder reactors, or fueling a CANDU with thorium? Pfui.

Posted by: Oh Not That Again | Jul 30, 2008 11:06:24 AM

The efficiency of modern steam turbines is 45-50%. AC Generators ~98%.
The quality of the steam produced by the collectors is very important.
Quality in this context means how much superheat; basically, superheat is how much higher is the temperature compared to the boiling point of at a given pressure. The steam turbine is at it's most efficient when it is fed with steam at it's design pressure and temperature. So, a lot of control valves and such are needed to provide this correct steam quality, probably at a loss of transfer efficiency from the boiler tubes to the turbine(s). That is the unknown in the equation as far as my limited knowledge is concerned. Solar energy in the right place at the right time (solar noon, dead overhead) provides ~1000 watts per horizontal square meter. So, the collector mirrors' area comes into the equation and then the heat transfer from the tubes' outer surface to the water inside is a big factor. The emissivity of the surface determines how much energy is passed to the pipe, ie not reflected away. My guess is about 85% goes into the metal, which will pass some energy to the water and lose some by radiation back to the surrounding. I'll guess 80% goes into the water. And, I'll guess 20% loss through the control valves, ie 80% of the energy gets through. So, the overall efficiency, maybe, is .47 x .98 X .85 x .80 x .80 = 0.25 = 25% on a perfect day.

Since solar energy is free per se, the rules of economics apply: capital cost of equipment and land (or rental of same), gross operating costs less any government incentives, etc etc, just like any other business.

What is disturbing is the question of water supply (the next valuable commodity?) meaning that the system had best be closed loop (more capital cost, less effiency - heat exchangers with large electric fans).

Posted by: xpatUSA | Jul 30, 2008 11:06:25 AM

Er, heat exchangers would likely be needed to turn the steam coming out of the turbine back into water before it goes back into the solar boiler tubes.

cheers all, this is a great blog BTW, IMHO, TTFN!

Posted by: xpatUSA | Jul 30, 2008 11:13:59 AM

xpatuSA: thanks for the good summary.

I would add that using solar heat to produce steam has been done since the 19th Century. It works but but cheaper fuel has always beaten it. That will be ending. Modern materials and computerized control systems will overcome durability and control problems.

The quality of the steam is important but the quality of the water is also important. The water available in dry regions usually has a high mineral content. In common terms it is hard water and not good for steam generation equipment.

As you note closed loop cooling using is the best solution. The water can be kept clean and little is wasted. But dry heat exchangers are the most expensive.

Posted by: K | Jul 30, 2008 1:08:12 PM

the cheapest alternative "fuel," is already competitive with conventional sources: conservation.

Thinking like economists, we would expect conservation at the margins to be competitive with conventional sources. And I'm all for conservation, as long as it's done efficiently, which usually means via the mechanism of higher prices and individual decisions. However, conservation has the problem of diminishing returns in a way that increasing our energy supplies does not - if we add 20% to our electrical (power) capacity by building new plants, that extra energy should be as cheap or cheaper than what we have now, whereas with conservation it is rather likely that the next (marginal) unit of energy saved/produced will be rather more expensive than the first. So if I seem not to spend a lot of time discussing conservation, it's because
A) I expect it to happen largely automatically (without government encouragement) via prices
B) it's not a complete solution to our future energy needs

Your point about subsidies to existing energy is well-taken, however. You didn't even touch on the atrocity of coal-fired power generation, which combines production subsidies, environmental costs for production, *and* environmental costs burning the stuff - a winning combination of mercury, radioactivity, and CO2 for those who care about it).

I've looked into the Stirling Solar technology before. At the time it seemed to be still too expensive by a factor of 3, but a lot of that was because of the fairly high cost of manufacturing the assemblies. One manufacturing rule of thumb is that you can cut costs by 10-15% for every doubling of the number of pieces you make (due to economies of scale), which suggests to me that Stirling could be competitive under the right conditions, i.e. if a sufficient price shock allowed them to expand about a thousandfold. I don't actually expect this to happen, but I do find it reassuring that we have such alternatives as a backstop in case the peak oilers and other doomsayers turn out to be half-right.

Posted by: bbartlog | Jul 30, 2008 1:50:40 PM

Subsidies for Energy in the USA

A frequently quoted theme is the vast government subsidies that both oil and nuclear enjoy should be stopped and help given to the renewable energy sources. This is usually followed by some number in the billions of dollars without a reference.

To put this in perspective we need to look at the DOE energy consumption numbers for a base line. The following are from the 2007 data and I rounded to the nearest percentage.

Coal = 33%
Oil & Gas = 46%
Nuclear = 12%
Other = 9%

According to EIA, federal provisions that can be considered direct and not merely the application of tax credits available to any US industry, we have the following.

Coal = $3.3 Billion (2.37 Billion to “Clean Coal” and 0.932 Billion to normal coal)
Oil and Gas = $2.15 Billion
Nuclear = $1.267 Billion
Renewables = $4.875 Billion.

In the Renewable category is Hydro power at about 36% and what is called BioMass at 53%. Wind, Solar and Other make up the remaining 11%.

So we have 42% of the government subsidies going to the group that produces the smallest amount of energy.

BioMass is where Ethanol lives. However, there are additional subsidies for ethanol that do not show in the energy subsidies. The Heritage Foundation estimates that the farm industry receives about $25 Billion a year from the government. Part of that subsidy goes to produce Ethanol.

Posted by: Stan/Tx | Jul 30, 2008 3:23:14 PM

I researched these some time back. If done in the middle of the desert in hottest parts of the US, they are only slightly more expensive than nuclear power - except that most of your customers do not live in the hottest and driest parts of the hottest deserts. If you add in the costs of power lines from where the burning sun is seldom interrupted by clouds, to where customers are, they are a lot more expensive than nuclear.

But right now, they are the most realistic alternative renewable power source. If those greenie earth worshippers force us to go renewable, we could do it by covering a large chunk of death valley with these solar concentrating power generators - except that that they would probably discover a vitally important ecology in death valley in the same way they did in the middle of the arctic tundra.

Posted by: James A. Donald | Jul 30, 2008 4:22:54 PM

Hmmm...177 MW divided by (4047 sq. meters/acre X 640 acres X 1kW/acre) X 100% = less than 7% efficient.....worse than a solar cell.

Posted by: Bill | Jul 30, 2008 6:02:27 PM

There is an interesting story out today about Capstone Turbine and Heliofocus working on solar heat power generation in Israel. They intend to use small turbines run with heated air. More intention than fact so far.

Their approach would use water and have no cooling problems. Anyway the address below should take you there. I never post live links.


Posted by: K | Jul 30, 2008 7:52:25 PM

Drat. And several other words. Correction.

Their approach would use NO water and have no cooling problems. Anyway the address below should take you there. I never post live links.


Posted by: K | Jul 30, 2008 7:55:17 PM

Y'know, Yoshidad, everything that you've listed above is U.S.-centric. But, despite being the undisputed global champion in almost everything, America isn't all that there is to the world.

If you care to look around, you'll learn that Europe and Asia have each addressed some of those concerns or problems.

And as for #4, ask disingenuous questions that attempt to insult your opponents with name-calling, you seem to be psychologically projecting, since you're the King of Gratuitous Ad Hominem - as far as I've seen, you always START OUT with the assumption of hostility, which naturally becomes a self-fulfilling prophecy.

Further, anyone posting about "peak uranium" has clearly and obviously NEVER DONE ANY RESEARCH WHATSOEVER into the subject, such as can be done in ten minutes, with one web-search.

Anyone who's willing to spend fifteen minutes writing a lengthy blog post, but ZERO minutes learning anything about the subject, without doubt has problems.

In any case, there are estimated to be 4.6 billion tonnes of uranium in seawater alone, or the energy equivalent of 360 trillion barrels of oil. This uranium can be extracted from seawater for no more than 10 times the cost of traditional mining (assuming that one can trust the science of those notoriously non-technical Japanese) [/sarcasm].

Combine all of that uranium with pebble-bed reactors, and Bob's your uncle. Cheap, safe energy - no possibility of Three Mile Island or Chernobyl.

So speaking of "peak uranium" makes about as much sense as speaking of "peak sunlight" for solar - yeah, theoretically it could happen, but by that time everyone reading this blog will have long been dust.


Finally, to diverge for a moment to "conservation vs. oil drilling", even James "The Long Emergency, Hand-Crafted World" Kunstler advocates for drilling, even though he sees it as a stop-gap, at best, and Kunstler of course is as dystopian as they come.

Posted by: Solar Lad | Jul 31, 2008 4:02:33 AM

James Kunstler's site

Posted by: Solar Lad | Jul 31, 2008 4:08:07 AM

OK, third time's the charm: James Kunstler's site

Posted by: Solar Lad | Jul 31, 2008 4:12:46 AM


So, the Universe is telling me to be more humble.
Don't attempt to use the above Kunstler links.

James Howard Kunstler

Posted by: Solar Lad | Jul 31, 2008 4:20:00 AM

"In federal spending, conventional energy receives 29 times more funding than renewables."

Hm, Stan/Tx cited just one (of many) subsidies for solar at 30% of capital costs. Is Yoshidad claiming that subsidies for conventional power amount to 870%?

Posted by: | Jul 31, 2008 6:47:26 PM

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