A hundred miles of mirrors

Solar thermal can save us, but it needs public clamor

Posted by Ted Nace (Guest Contributor) at 10:52 AM on 22 Jun 2008

Read more about: climate | energy | climate change impacts

[Editor's note: When this post was originally run, the phrase "100 miles by 100 miles" was changed to "100 square miles," which is very different. The article has now been corrected (or rather, unmiscorrected) and the appropriate intern flogged; our apologies to Ted and Alex.]

This post was coauthored with Alex Carlin, organizer of Let's Go Solar and instigator of the recent Environment America study (PDF), "On the Rise: Solar Thermal Power and the Fight Against Global Warming."

Every day more people are finally hearing about what Joe Romm calls "the solar power you don't hear about" -- solar thermal power, utility-scale arrays of mirrors that create heat (and then electricity) so efficiently that they can do everything a coal plant can do except melt the South Pole.

Without any special promotion, solar thermal (concentrating solar power, or CSP) will eventually grow into a major supplier of our electric grid, simply because, according to the California Energy Commission, it is an increasingly economical technology with per kilowatt-hour costs estimated to be 27 percent lower than new integrated gasification combined cycle (IGCC) coal plants with carbon capture-and-storage -- 12.7 cents/kWh for CSP versus 17.3 cents/kwh for IGCC plus CCS.

The technology is moving forward, with five plants already operational, eight under construction, and 20 more announced. Several of these plants include on-site thermal storage, an option that makes CSP a reliable source of baseload power.

The problem is the timeline of global warming. If we take seriously what the science is telling us, we must conclude that CSP has arrived in the nick of time. James Hansen's latest team effort (PDF) tells us that earth has had many eras with ice-free North and South Poles. The report concludes: "If humanity wishes to preserve a planet similar to that on which civilization developed ... CO2 will need to be reduced from its current 385 ppm to at most 350 ppm." On the other hand, if we continue to burn coal for our electric power, those poles will melt, sending sea levels so high that cities like New York and Miami would have no chance to survive.

You probably already knew that, but did you know this? Just 100 miles by 100 miles of CSP installations would supply 100 percent of the U.S. electric grid. That's being conservative: Ausra's chairman David Mills pegs the figure at 92 miles by 92 miles. Put similar installations in Morocco for Europe and the Gobi desert for China and we have our golden opportunity -- our last chance -- of keeping those poles under ice and our cities above water.

How much land is 100 miles by 100 miles?

About the same as all the land disturbed by coal mines.
About one-sixth of the area devoted to lawns.
About 1/15 of the area once devoted to raising feed for horses.
Less than 1/30 of the area devoted to parks, wilderness, and wildlife refuges.
Not much to ask to avoid unspeakable disaster.

But we need to get this done fast. James Hansen says that coal emissions must be phased out (PDF) by 2025 (developed countries) or 2030 (developing countries) (PDF). That's a lot faster than utilities will move on their own. Something has to break through the inertia that seems certain to doom all our best efforts. That something is public clamor. The slogan "100 miles of mirrors" is catchy. It's simple enough, and it could cause a chain reaction. Bumper stickers, graffiti, calls to talk radio, letters to newspapers, gossiping, rumor milling -- it can become a national phenomenon that unites right-wingers with left-wingers to "just build those 100 miles of mirrors." Why not? It saves our country from near certain doom.

Wind, geothermal, efficiency, and all the other good ideas will have their place. In fact, these additional alternatives mean that we may need far less than 100 miles of mirrors. But because it can provide a direct baseload substitute for coal plants, CSP has a unique role to play in rallying the public around a simple message -- and generating public clamor requires an extremely simple message:

You wanna burn coal?
You melt the South Pole!
100 miles of mirrors or it won't be pretty.
Solar saves Miami and New York City!

For story: A hundred miles of mirrors
35 Comments | Post a Comment

Just how stupid are solar advocates?

Ted Nace, claims "Just 100 square miles of CSP installations would supply 100 percent of the U.S. electric grid." Wow. and to think That Scientific American was talking about thousands of square miles of PV installations only in January. Nace is either bucking to be world champion lier for 2008, or he does not understand the difference between 100 square miles, and a 100 mile by 100 mile square. Rest assured Ausra's chairman David Mills talked about 92 miles by 92 miles which equals 8464 square miles not 92 square miles as Nace claims.

Charles Barton

by Charles Barton at 11:17 AM on 22 Jun 2008

Yes

But of course with conservation power use could be cut in half, and wind could takeover 20% of what we now use. 40% after conservation takes hold.

Rooftop solar could do half of the reduced demand, leaving the rest for CSP installations and biogas from waste as ultimate backup.

That's more symbiotic, like natural rythyms of wind, sun, clouds, it works with nature.

Large centralized expanses of CSP taking over square miles of land aren't so symbiotic. Try smaller CSP to power factories, from the roof and land surrounding the plants. It can still power 10 or 20% of the new level of power consumption after conswervation kicks in.

With 10 or 20 square miles total, a half a square mile or quarter per factory site.

http://amazngdrx.blogharbor.com/blog John Schneider, Northern Wisconsin

by amazingdrx at 11:24 AM on 22 Jun 2008

Comparing Apples to Oranges

PV does not equal CSP

PV or photo-voltaics are polycrystalline layered platters that only convert a portion (about 28%-30%) of the amount of energy that falls upon them.

CSP or Concentrated Solar Power, relies upon reflectors which to concentrate energy collected from a large area upon a central tube which superheats it and the liquid inside, which then powers a generator akin to the way that gas-fired steam turbine plants work.

PV's would require 1,000's of square miles to power the grid.

CSP's on the other hand are more efficient, and therefore would only require 100 square miles to produce the same amount of energy.

by tnrkitect at 12:36 PM on 22 Jun 2008
[ Parent ]

That's right

Make that 1000 square miles, one installation per factory averaging 1/2 square mile, on 2000 factories. Well within the realm of practicality.

A 100 mile square equals 10,000 square miles. Whoops. One tenth, 1000 square miles of CSP, could power 10% of present power use, 20% of use after conservation.

http://amazngdrx.blogharbor.com/blog John Schneider, Northern Wisconsin

by amazingdrx at 12:44 PM on 22 Jun 2008

CSP: An unfortunate acronym

Unfortunately.

CSP can refer to both Concentrating PV, and Concentrating SolarThermal.

CPV, CST would be better acronymns.

However CST, "Central Standard Time" is already kinda taken....

-David Ahlport

by GreyFlcn at 1:03 PM on 22 Jun 2008

Definitely 92 miles by 92, not 92 sq miles

The relative efficiency of solar thermal vs. photovoltaic is only a factor of 2 or 3, not a factor of 100 or more. So yes, we would definitely need cover an area close to 100 miles on a side.

But that said, even that isn't really that much area. The US has an "impervious surface area" (roads, buildings, etc.) considerably larger than that, so it's well within the range of our capabilities.

by apsmith at 1:18 PM on 22 Jun 2008

Oh noes!

re: Charles Barton
OMG Solar thermal would take 8,464 to 11,600 square miles!
The Horror!

136,000 square miles were devoted to corn planting in 2007. [@]
Roughly 43,000 square miles of which were devoted exclusively to corn ethanol production.

So yeah, it is a considerable area. However it's not like that would be a real limiting factor in any serious discussion.

-David Ahlport

by GreyFlcn at 1:21 PM on 22 Jun 2008

Some math

About 868,000 square kilometers of "Warm Desert" in North America

0.386102159 square miles per square kilometer

335,000 square miles of "Warm Desert" in North America.

Is that enough?

-David Ahlport

by GreyFlcn at 1:29 PM on 22 Jun 2008

Fortunes of acronymity

I guess solar furnaces could have solar PV surrounding the heat receiver, to catch the inevitable leakage at the focus. So that would make it solar cogeneration.

Like wise solar PV is much better fed by concentrated light and cooled to collect heat. So solar cogeneration works on both applications. And solar furnace mirrors can go over parking lots, on roofs, and even over highways.

The hot desert regions have plenty of space and sun. "Impervious surface areas" preffered! Over wilderness land.

http://amazngdrx.blogharbor.com/blog John Schneider, Northern Wisconsin

by amazingdrx at 1:38 PM on 22 Jun 2008

Solar dish mirrors - MIT

Shameless self promotion from Cambridge last week --

http://features.csmonitor.com/innovation/2008/06/18/mit-t ...
http://web.mit.edu/mitei/education/spotlights/solar-dish. ...
http://www.harbornet.com/sunflower/pvdish.html

-- Doug.

by sunflower at 2:07 PM on 22 Jun 2008

Making thermal solar more believable...

Thermal solar is up and working. Has been for several years in California.

What would make it more exciting(?) for a lot of people is if there was a working plant with significant heat storage so that electricity could continue to flow after the sun sets.

I understand that there is one such plant being constructed in Spain at the moment.

But to appeal to the larger portion of Americans (many who think that no good ideas are to be found past our shores) a "see it here, now" project would make the system concrete and generate a more accepting climate.

by Bob Wallace at 2:19 PM on 22 Jun 2008

Uhg... we did that already

What would make it more exciting(?) for a lot of people is if there was a working plant with significant heat storage so that electricity could continue to flow after the sun sets.

You mean like this solar power storage plant built in 1981? "Solar Two".

http://ucdcms.ucdavis.edu/solar2/photos
http://ludb.clui.org/ex/i/CA4989/

-David Ahlport

by GreyFlcn at 2:32 PM on 22 Jun 2008

Re: Solar dish mirrors - MIT

Great stuff, Doug!

One of the keys to making an inexpensive design was something Wood discovered by accident as he built a variety of solar dishes over the years: Smaller really is better. Unlike many technologies where economies of scale dictate large sizes, a smaller dish requires so much less support structure that it ends up costing only a third as much, for a given collecting area.
MIT Sloan School of Management lecturer David Pelly, in whose class this project first took shape last fall, says that "I've looked for years at a variety of solar approaches, and this is the cheapest I've seen. And the key thing in scaling it globally is that all of the materials are inexpensive and accessible anywhere in the world."

Just how cheap is this dish, compared to other solar tech?

Ped Shed Blog

by Laurence Aurbach at 4:02 PM on 22 Jun 2008

How cheap can solar get?

Good question.

Ausra (line focus) claims $100/m², BrightSource (power tower heliostats) $150/m², Matrix Solar Dish (me) $100/m².

All these leading solar concentrators have one to three year simple paybacks against oil and gas in Colorado type climates, double that in cloudy climates. Concentrator lifetimes are 30 to 50 years with the new glass/silver/palladium/paint mirrors from Guardian Industries.

Solar dishes have the edge on performance due to no cosine losses from directly tracking the sun in two axes, and due to small high-intensity point-focus receivers.

No new tooling requirements enable rapid global scale-up using existing commodities assembled with existing labor skills.

by sunflower at 4:53 PM on 22 Jun 2008

Brang it on !!!!

The only thing I ask is that these facilities are sited in good places, and that transmission lines can be built without screwing up the environment too much.

Take a look at the maps. Some areas get more sun, other areas are prone to floods, harsh winters, fogs, and hurricanes, not good for concentrated solar furnaces (CCF sounds good to me!). The transmission lines might be the weakest link in the system ... I think many are thinking about the desert Southwest here.

Solar concentrator furnaces are NOT a good idea in urban areas, IMHO.

Onward through the fog

by Sam Wells at 6:12 PM on 22 Jun 2008

Huh?

Because we built one 25 years ago with 25 year old technology we shouldn't build one today with today's technology?

Is that what you mean?

Someone built an electric car prior to 1839.

We shouldn't try that again?

Just not following your logic.

by Bob Wallace at 6:28 PM on 22 Jun 2008
[ Parent ]

Pacific DC Intertie

We've already got a HVDC line running from north to south along the west coast. It was built to bring hydro-generated power to Southern California.

It sweeps east through western Nevada as it ducks around the Sierra. Pretty close to some of those very sunny climes.

by Bob Wallace at 6:33 PM on 22 Jun 2008
[ Parent ]

Thanks Bob, that was interesting.

I hope we can eventually get beyond the mantra of power and use solar concentrators for what they are best suited for, displacing fossil fuels. Applications include industrial process heat, preheating existing power cycles, commercial and residential HVAC, desalination, and so on. Later, much later, we can do base load solar power plants.

The value of solar concentrators is the value of fuel displaced. Do the simple stuff first.

by sunflower at 7:28 PM on 22 Jun 2008

Is CSP really over 200% efficient?

Tnrkitect wrote: PV's would require 1,000's of square miles to power the grid.

CSP's on the other hand are more efficient, and therefore would only require 100 square miles to produce the same amount of energy.

If we take that implied PV/CSP ratio to be at least 20 (2,000sqm/100sqm), and if we assume that PV has an efficiency of at least 10%, your statement seems to imply that CSP has an efficiency of at least 200%.

Is that really what you meant to imply?

by Nucbuddy at 7:47 PM on 22 Jun 2008
[ Parent ]

Diffuse fuels never scale

GreyFlcn wrote: 335,000 square miles of "Warm Desert" in North America. Is that enough?

If Nevada Solar One is averaging ~10 MW/sqm, it would need to be scaled up to ~50,000 square-miles to cover the present average electrical market of the United States. As the United States electricity market expanded to 10 times its present size, the solar power plant would need to scale up to ~500,000 square-miles (but that little, only if all of those square-miles were as optimal as the first square-mile), exceeding all of the "Warm Desert" land area in North America.

by Nucbuddy at 10:17 PM on 22 Jun 2008
[ Parent ]

Solar Thermal land area for US load-matching

Good article and summation of extant literature on solar thermal electrical generation and its ability to match US electrical load. However, there is the frequent error of referring to the reflector array sufficient to power the US - it is the square of 92 miles, not 92 square miles. That is: 92x92, which is 8,460 square miles.

This is still a very small land area even if you narrow it to just available publicly-managed lands in only California's section of the Mojave desert.

David Mills of Ausra elaborates this quite clearly:
http://ausra.com/pdfs/SolarPACESMills-Morgan.pdf
as well as in:
http://ausra.com/pdfs/T_1_1_David_Mills_2049.pdf

Nathaniel Bullard
Senior Analyst, Solar Thermal
New Energy Finance

by nwbullard at 3:52 AM on 23 Jun 2008

Silly time :P

As the United States electricity market expanded to 10 times its present size

Heh, and now you're just trying to be silly and difficult. :)

"CENTURIES AND CENTURIES FROM NOW WE MIGHT HAVE A PROBLEM! OOOOH."

By the time your nitpicking would even have any chance to come into play we'd probably be getting more desert. (Good ol global warming, eh?)
Why would we be using first generation power plants centuries from now?
Why are we limited to only 1 technology? PV for instance could be dirt cheap by then. Or Hot Rock Geothermal. Or wave power. Or fusion! Or maybe we'll build us a super-cool dyson sphere.

-David Ahlport

by GreyFlcn at 5:04 AM on 23 Jun 2008

PV getting dirt cheap...

NanoSolar has their (first) one gig thin-film solar plant up and running. They can crank out one gigawatts of PV per year. Positioned in a high insolation area that gets 5 hours of good sun a day means that each year that one single printer can bring 5 gigawatt hours on line per year.

The machinery to produce one gig of thin-film cost $1.6 million. Chump change in the world of power production.

http://www.nanosolar.com/blog3/

by Bob Wallace at 6:58 AM on 23 Jun 2008

Water

One factor that I rarely hear brought up in discussions of CSP is the requirement for water for cooling and heat rejection.

The commonest way to make electricity from concentrated solar power is a steam cycle, i.e. rankine cycle, i.e. the same basic cycle used by all thermoelectric power plants (coal, nuclear, whatever).

This cycle requires the ability to reject a substantial amount of heat. Even after all the useful power has been gotten from the steam, it is necessary to re-condense to water before running it back through the plant. This is typically done with cooling tower, which lost a great deal of water to evaporation.

If you're planning to locate your plant in the desert, this is a problem. How much of a problem, however, I do not know: I have been unable to locate a good reference for the water requirements of nuclear vs. coal vs. solar thermal power. But I know it's an issue, and one that seems to be consistently overlooked. (If anyone has a reference, please let me know!)

There are a couple of ways around the problem. One is to use the heat somewhere else, in a combined heat and power (i.e. cogen) application. That's great, if you can do it, because you can get rid of your excess heat and displace boiler fuel in the process. However, this requires that the plant be located near the load, which is not a feature of most of the "carpet the desert with CSP" proposals that are out there.

The other way is to do a thermal-to-mechanical conversion, ala. Stirling Energy Systems. These units do not, as far as I know, require active cooling. However, they are most likely much more expensive per kW and certainly more maintenance-intensive than a large-scale steam-cycle CSP plant.

by GreenEngineer at 11:55 AM on 23 Jun 2008

Cool it at night

SES in Oz cools with holding ponds. Dry cooling at night is also an option. High-intensity pv can be located near hot water loads. Stirling dry cools behind the engines with large radiators. Waste heat can also be dumped into oceans, rivers, aquifers, city water companies, sewage treatment, and irrigation. Some propose using concentrator frames for dry cooling 24/7.

by sunflower at 12:55 PM on 23 Jun 2008

Water Requirements

The water requirements, independent of heat source, are directly related to the high temperature in the cycle. The higher the temperature, the greater the cycle efficiency and the lower the (relative) amount of heat required to be removed by the cooling medium. Therfore, Coal requires a little less than nuclear and CSP is probably similar to coal (at least for the systems I've seen). If you have the operating temperatures of facility, calculation of the water requirements is very simple.

Dry cooling is an option but the ability to take advantage of the daily cycle (greater cooling at night) is probably not practical due to the great investment necessary in storage. Dry cooling is used for some conventional power stations and falls within the cost effective range.

The Palo Verde nuclear unit in Arizona is cooled by treating aste water from Phoenix which solves two problems at once.

by KenG at 1:15 PM on 23 Jun 2008

Error has been fixed

Please note that the error noted by Charles Barton and Nathaniel Bullard (100 square miles is wrong -- 100 miles by 100 miles is correct) has been corrected and Grist has printed a mea culpa and an apology to the authors for mis-editing their post.

Help build coalSwarm-- a shared informational resource on coal and alternatives to coal.

by Ted Nace at 4:16 PM on 23 Jun 2008
[ Parent ]

An apology to Ted

I must apologize to Ted Nace for my remarks in the first post. Ted stated to me that he was not at fault for the errors for which I criticized him. According to Ted the errors were allowed to creep into his Gristmill post after he had submitted it to Gristmill.

Charles Barton

by Charles Barton at 4:28 AM on 24 Jun 2008

Solar thermal in desert

The least expensive way to cool solar thermal in the desert is to use waste heat in a closed loop for desalinization. That is your condesor coils are in a closed loop, cooled by the liquid you are purifying.

You add capital costs - not just in your system but in the water purification plant. (Desalination is only one part of the purification process. ) But the clean water is valuable enough, especially in the desert, to lower your costs.

by Gar Lipow at 11:54 AM on 24 Jun 2008

Re: Solar thermal in desert

Re: Solar thermal in desert by Gar Lipow,

That is a beautiful combo. Love it. Can you say "pipeline from Gulf of California to Arizona border"?

-Christopher

by christophersj at 1:11 PM on 24 Jun 2008

Re:Water, use dirt.

One possible solution to cooling water needs is to use a geothermal loop to cool your water. Provided that you have enough wells or enough separation between your hot well and cold well in an open loop system the ground loop could be used for daytime thermal storage.

At night the loop is reversed and solar updraft towers could cool the water in the ground loop while providing overnight power. In the winter the ground loop could preheat intake water or provide a thermal boost to an updraft tower on rare cloudy days.

In Australia, South Africa, Baja California and Chile there are areas with high insolation and little or no rainfall directly next to the ocean. A solar concentrator field next to the sea can combine with an ocean loop (OTEC) and provide significantly increased efficiencies and fresh water in some quantity. These could be areas where high energy industrial processes might be relocated to take advantage of power availability.

Combining known systems such as geothermal loops with solar concentrators or solar concentrators with updraft towers or all three could provide greater efficiencies than single systems.

Put the Carbon Back

by Pangolin at 1:15 PM on 24 Jun 2008

100 miles of mirrors

Hey, this is a cool forum; there are actually people here who can think, and not many personal attacks.

Hey, I love Pangolin's idea of using this "waste heat" to power a desalinization plant. Re Chile, is it really sunny there? I've been to extreme southern Peru, near the Chilean border, and it never rains, basically, but there's nine months of fog per year. Weird. Guess the fog doesn't affect northern Chile?

I've been hooked up to a 3Kw PV system for about five years. it's great, but I hope we can get systems for less money in the future. Meanwhile, I've been enamored with solar troughs for years. i'd rather give up EITHER 100 or 10,000 square miles of desert in exchange for all the benefits, e.g. have you ever flown over the eastern/central US, and seen the innumerable plumes of black smoke from the (coal fired?) power plants?

Wanna save time, money, and the environment? Support PRT (Personal Rapid Transit) Not hip to PRT? Google it!

by jumpoff joe at 4:46 PM on 03 Jul 2008

Telescopes go in the Atacama desert ...

which is in Chile. If they can see out, I guess the sun can see in.

... have you ever flown over the eastern/central US, and seen the innumerable plumes of black smoke from the (coal fired?) power plants?

I have been on such a flight a couple of times, but didn't see black plumes. When I saw a plume from a coal plant stack from the ground, it wasn't black, just slightly dusty-looking. Maybe they were crashing a lot of gasoline tankers that day.

--- G.R.L. Cowan, H2 energy fan 'til ~1996
http://www.eagle.ca/~gcowan/Paper_for_11th_CHC.html

by GRLCowan at 5:58 PM on 03 Jul 2008
[ Parent ]

"unmiscorrected"

Is the flogging of the anti-Euclidean intern in question on YouTube yet?

Chickens deserve our true friendship! So do fish! So do other sentient beings! Let us learn to be kind.

by caniscandida at 11:29 PM on 03 Jul 2008

Joy

I got my chart back!
http://greyfalcon.net/energy2.png

I like this chart :)

-David Ahlport

by GreyFlcn at 7:01 PM on 07 Jul 2008

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