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They do it with Mirrors: Concentrating Solar Power

December 7, 2006 at 4:48 pm Filed under Concentrating Solar Power, csp, PV, Renewable Energy, solar

thermal

Note 5/3/09 Some more recent CSP articles are here.

Ive just spent some time reviewing a pile of reports on concentrating solar power (CSP) technologies for

Ratepayers United Colorado (RUC), so here is a summary of the various types.

Technology descriptions

Concentrating Photovoltaic

o This technology uses mirrors or lenses to focus sunlight on high-efficiency photovoltaic chips.

The extra sunlight makes it worth the expense of making a more efficient higher complexity

chip because each chip can convert more sunlight to electricity, with conversion efficiencies oftentwice as high as the efficiencies of conventional soar panels. This also has the advantage of

saving silicon (which is in short supply) for making chips. Problems are that they do not work as

well as conventional panels in diffuse light through clouds (because the light cannot be focused)

so they are only appropriate for areas with very little cloud cover, and the extra light heats the

chips more, which lowers their efficiency, and so may require some sort of additional cooling

loop.

o Article links:

o http://thefraserdomain.typepad.com/energy/2006/03/concentrix_conc.html

o http://thefraserdomain.typepad.com/energy/2005/11/stellaris_conce.html

Parabolic trough

o The oldest CSP technology, parabolic trough plants, known as SEGS 1 through 9, have been

operating reliably in the

California and Nevada deserts since the 1970. Parabolic

trough plants work by focusing sunlight on pipes by means of

parabolic mirrors. These pipes contain a working fluid

(several have been used, from water and superheated steam

to molten nitrate salts.)

o Parabolic trough technology is currently experiencing a

revival, with several new plants being built. The using ofOrganinc Rankine Cycle generators allows solar trough plants

as small as 1 MW to be built (such as the new Saguaro plant

north of

Tucson, AZ.

o Parabolic trough technology allows energy to be stored as heat, which is much less expensive

than storing electricity. This allows the energy from these plants to be available at times of peak

demand, making the electricity much more valuable.

o Steve Raabe recently wrote an article for the Denver Post providing a good overview of the

prospects of this technology in

6/27/2011 They do it with Mirrors: Concentrating S

cleanenergywonk.com//they-do-it-wit 1/


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Colorado. The only point that he missed is the potential for hybridization with existing coal and

gas plants. By preheating steam for an existing fossil fuel fired turbine, CSP can make an old

power plant operate much more efficiently. Arnold Leitner of SkyFuel (www.skyfuel.com) tells

me Our preliminary engineering estimates, satellite imagery of the locations and solar data show

that SkyFuel could supply 50-100 MW-electric solar steam to the Comanche power plants

generating an estimated 65,700-131,400 MWh of pure solar power at the facility via the existing

steam turbine. SkyFuel could deliver this solar-generated steam to the power plant at an effective

fuel cost commensurate to the fuel cost of burning natural gas at a modern combined cycle powerplant at fuel price of 7-8 cents/mmBtu. In other words, through a FuelSaverTMat a coal-fired

power plant SkyFuel could provide solar energy at the price of natural gas generation.

o Considering that solar power is available during peak demand, gas ifered generation is the

appropriate cost comparison (as opposed to wind power, which does not deserve (or need) a

price premium due to its unpredictable timing.

o A variant on this called Concentrating Linear Fresnel Reflector (CLFR) uses many thin mirror strips instead

of parabolic

troughs to concentrate sunlight from a large field onto justtwo tubes of working fluid. This has the advantage

that flat mirrors are much cheaper to produce that

parabolic mirrors, and also allows for a greater

density of reflectors in the array, allowing more of the

sunlight to be used.

Power Tower

o Power Tower technology is similar to solar trough technology in

that it uses mirrors to concentrate sunlight on a working fluid which isthen used to superheat steam to run a turbine. The difference is that

the mirrors concentrate all the sunlight onto a single receiver at the top

of a tower. This allows for higher temperatures, but leads to

engineering problems because of the high temperature at the receiver.

o Lower price per watt is theoretically possible

compared to trough technology because of the higher

temperatures.

o So far, only two pilot plants have been built and

operated, called Solar One and Solar Two (actuallythe same facility as Solar One, but converted to use nitrate salts as the working fluid rather than

superheated steam). Both Solar One and Two incorporated thermal energy storage. Due to

the success in demonstrating the technology of Solar Two, a commercial 15MW plant Solar Tres

is in the planning stations. This station will incorporate enough thermal storage in molten salt

tanks for 24h operation.

Solar Chimney

o A Solar chimney consists of a large greenhouse (multiple square miles of area covered by a




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transparent roof) which is sloped gently

up to a central hollow tower or

chimney. The sun heats the air in the

greenhouse which then rises up the

chimney driving an air turbine (similar to

the hydroelectric turbines used to

generate power at dams) in the chimney

as it rises. Water filled tubes on thefloor of the greenhouse serve as heat

storage which allows the chimney to

operate even at night and on cloudy

days. The amount of water in the tubes can be changed to alter the profile of power production

and match it closely to the power demand the chimney serves.

o The edges of the greenhouse can actually be used for agribusiness to grow plants, so not all the

space taken up is solely devoted to electric production.

o The beauty of solar chimneys is that they are extremely low tech, and can be built without heavy

equipment using simple materials. The only exception to this is the turbine, and even that is much

less complex than turbines used to generate power from wind, because the wind in a solarchimney is much more regular than naturally occurring winds and storms that wind turbines have

to deal with.

o The first solar chimney was built in

Manzanares, Spain and ran continuously for 32 months in the late 1980s with 95% availability

(considerably better than most coal and nuclear plants.) See a video tour of this chimney I ran

across on EcoGeek.

o A 200MW chimney is planned by EnviroMissionof Melbourne Austrailia for the Austrailian

Outback.

o

It may be possible to build solar chimneys on south-facing slopes or simply as an extra layer ofglazing on tall buildings with a turbine at the top which would make them even cheaper by

avoiding the necessity of building the tall chimney (my idea).

Dish Stirling

o A Dish Stirling system is a parabolic mirror which focuses heat directly on a Stirling engine, a

simple closed-cycle engine which operates

simply using any heat source. Sometimes

hybridized with a fossil fuel source to provide

heat when the sun is not shining.

o DishSterling systems have the advantage of small

size and scalability, because each individual

mirror-engine system produces only around

25kW, but many can by linked together.

o Because the suns rays are focused directly on

the engine, there is little opportunity for

thermal storage, a great advantage of several

other thermal concentrating technologies.

o Stirling Energy Systems currently has a few demonstration systems in operation. They have




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Like Be the f irst to like this post.

signed purchase agreements with two

California utilities to build a total of around 1 GW of electric generation, but both projects are stil

in early testing phases.

o According to Sandia National labs, this is the most efficient technology for converting sunlight

into electricity.

CSP Technology comparisons

Technology Scale Levelized cost

per MWh

Pros/Cons Complexity/

deploymentConcentrating PV Any $15-$20 No storage option;

does not work well

on cloudy days

High. Beginning to

be deployed in last

couple years.

Dish

Sterling

25 kW per dish Unknown High efficiency,

modular. No

thermal storage.

Just beginning to be

deploy

Parabolic Trough Most: >50 MW for

economies of scale;

Organic Rankine

Cycle 1MW+

$8-$18 current

$6 potential

Can hybridize with

existing fossil

plants.

Storage, well

understood

technology, needs

water for efficient

cooling.

Plants operating

consistently for 30

years in CA.

Solar Tower >30 MW $18+ current,

$5 potential,

can hybridize with

existing fossil

plants.

Storage.

Potentially cheaper

than solar trough.

Needs water for

efficient cooling.

2 pilot plants with

operational

history. First

commercial plant

now operational.

Solar Chimney 100-200MW Not yet known. Baseload power,

low maintenance.

Low complexity,

great potential for

3rd world.

Permalink




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23 Comments

1.

Leslie Glustrom said

December 8, 2006 @ 6:56 pm

Great summary TomThanks!

I especially like the idea of doing a solar greenhouse with turbine in combination with tall buildings.

Whether that particular idea works or not, it is part of what Ive long said about unleashing our ingenuity.

It is going to be such fun once we get going on all of this for real!

Thanks again. It is great to have you working on clean energy for the citizens of Coloradoand the world!

Leslie

P.S. Check out the trec-uk website.:) and then you might want to get hooked up with Gerry who runs

that site. He and I exchanged e-mails earlier this week. Good things are happening!

Reply

2.

anthea said

March 7, 2007 @ 7:30 pm

what do people use at night?

Reply

3.

Tom said

March 7, 2007 @ 9:27 pm

The great thing about CSP is that it is a lot easier t store heat than electricity. The heat can variously be

stored in large insulated tanks of water, molten salt, or oil. The heat stored that way can be used to

generate electricity at night or on cloudy days.

Reply

4.




6/14

peter kyte said

March 29, 2007 @ 6:52 am

Ive become interested in concentrated solar power do you feel it will be private sector or government

led and are there any avenues to invest in the stock market for CSP???

Reply

5.

Tom said

March 29, 2007 @ 8:20 pm

Government will have to get the policies right to get these projects started, but the investments will be

made by privately owned companies. Unfortunately, there are not American listed stocks that are deeply

involved in this field, but there are a few publicly traded compaines in world markets.

Acciona: a Spanish firm which was part of the consortium that build Nevada Solar One

Iberdrola: A spanish utility that has a CSP arm, and is moving into the US.

Enviromission: An Australian company that is construction solar chimneys.

In the US markets, you can buy FPL (Florida Power and Light): A US utility that owns the majority of the

SEGS built in California nad Nevada in the 70s and 80s. It may be reasonable to presume that they have

some interest in building more because they have experience running the existing CSP plants.

Note: This is just a listing of the public companies I know of that are involved in CSP. The decision to or

not to invest in any or all of these is your own. I cannot make a reccomendation without knowing yourpersonal financial situation.

Reply

6.

Bonnici said

June 5, 2007 @ 4:32 pm

I saw a solar power car in Colorado where can I find more information on them?

TK: I just read an article about solar powering your Prius on EcoGeek.

Reply

7.

Fred Kirsch said




7/14

June 18, 2007 @ 1:57 pm

Im researching alternatives to RECs for Fort Collins green energy plan. Any investment opportunities

in CSP for city dollars?

Reply

8.

Tom said

June 18, 2007 @ 2:50 pm

Fred- as far as I know, there are no current plans on the drawing board for a CSP plant but that might

change very soon. The only recent plants built in the US are a small one in Arizona, and Nevada Solar

One, both of which were built to help meet those states RPS requirements, so I doubt there are SRECs

available from them.

Ill to pass your contact information on to other people who who may know anyone trying to get a CSPproject started in Colorado.

Reply

9. Alt Energy Stocks Blog Archive A Solar Technology for Every Application

said

September 30, 2007 @ 4:44 pm

[...] Linear Fresnel Reflector (CLFR) developer Ausra has been keeping long-underappreciatedConcentrating Solar Power (CSP) technology in the news recently. I consider this great news, because

the potential for [...]

Reply

10. Alt Energy Stocks Blog Archive The Arizona Renewable Energy Assessment:

An Investors Perspective said

October 28, 2007 @ 2:43 pm

[...] The only exception to this broad trend is the selection of "Parabolic Dish Engine" (which I usually refer

to as Dish-Stirling) and the emphasis of large scale Photovoltaic over small scale residential solar

photovoltaic (most [...]

Reply

11.

C J vd Merwe said




8/14

November 18, 2007 @ 2:41 am

I am farmer of South Africa developing an irrigation farm and enjoys 345 days without any clouds per

year. Can CSP be an option?

Reply

12.

Tom said

November 18, 2007 @ 10:24 am

CJ: South africa has a good solar resource for CSP, especially in the NE of the country.

Click here for a map.

So there is potential. Most projects tend to be very large, however, to acheive economies of scale.

Reply

13. Clean Energy Intro: Solar Thermal : CleanTechnica said

March 10, 2008 @ 12:13 pm

[...] exciting news has been emerging about solar-thermal. Its been demonstrated as reliable for over

twenty years, and new plants are coming online, or being planned, across the world. Energy is not the only

[...]

Reply

14.

George said

April 30, 2008 @ 6:01 pm

Anybody know of any CSP technology for individuals i.e for the cottage, campers etc?

Reply

15.

Solar Dave said

May 5, 2008 @ 9:03 pm

I went by the largest PV planet in the US in Alamosa Colorado (I took some video and put it on my site)

and I scratched my head an thought why they didnt use concentrated solar instead.




9/14

Reply

16.

Tom said

May 8, 2008 @ 10:34 pm

Solar Dave:I believe they chose not to use CSP for 2 reasons: the site is only 8MW, and CSP works best at over 15

MW for solar towers, and 200 MW for parabolic trough. The other reason was that the site has limited

water, which means that the turbine would need air colling, which lowers the efficiency.

Reply

17.

Caferacer said

September 7, 2008 @ 1:33 pm

There is a small private company in Nevada doing research on small scale csp. They are building a

prototype this fall.

Reply

18. Renewzle Knowledge Base Blog Archive Clean Energy Intro: What is

Solar Thermal Power? said

September 16, 2008 @ 9:00 pm

[...] exciting news has been emerging about solar-thermal. Its been demonstrated as reliable for over

twenty years, and new plants are coming online, or being planned, across the world. Energy is not the only

[...]

Reply

19.

Linn Gillsaid

January 14, 2010 @ 9:53 pm

I see everyone is still chasing the sun , Well if someone would ask nicely I would show them an easier and

cheaper way to get the same or better results. I wount sell the cow for beans but if somone wants to see

how to produce power from sun light even in the dark give me a e-mail @ TAGz3339 yohh

Reply




10/14

20.

byezz said

May 6, 2010 @ 7:12 am

anybody could give some info about difference between parabolic dish,dish sterling and parabolic trough?

im student interested in green tech-solar powered electrical system..tq

Reply

21.

IXLNXS said

July 3, 2010 @ 2:00 pm

Using the principles of reflective light and heat you can easily build water treament plants that would notonly produce clean drinking water but also electricity. All the parts already exist in differing mechanisms

and just need to be combined to begin distilling seawater for a multitued of purposes.

Reply

22.

reza said

November 24, 2010 @ 9:12 am

dear

I want completly information about this tecnology and money and capital for buy 20 Mwat of this system

for instalation near a ready powerhouse by gas fuel .

I want completly information about money and capital for buy a gas turbine sysytem by 20Mwat power

tancks alot

Reply

23.

Dale Jamer said

February 19, 2011 @ 10:17 pm

Great Post this will help keep up the good work.

Reply




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is a policy wonk and investment analyst specializing in Renewable Energy and Energy Efficiency.

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