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All you need is love sun

Solar thermal company says its generation/storage combo can power the nation

Posted by David Roberts at 8:48 AM on 23 Sep 2007

Read more about: energy | solar thermal power | electricity grid | energy storage

A new design for solar thermal electric generators could bust the technology out of niche status and supply the country's entire electric load, according to ... people who make solar thermal electric generators.

... physicist David Mills, chief scientific officer and founder of Palo Alto, Calif.-based solar-thermal company Ausra, has bigger ideas: concentrating the sun's power to provide all of the electricity needs of the U.S., including a switch to electric cars feeding off the grid. "Within 18 months, with storage, we will not only reduce [the] cost of [solar-thermal] electricity but also satisfy the requirements for a modern society," Mills claims. "Supplying [electricity] 24 hours a day and effectively replacing the function of coal or gas."

The company insists it can do this at a cost of just 10 cents per kilowatt-hour, analogous to the price of electricity from burning natural gas in California if a cost was imposed for the emission of carbon dioxide, the leading greenhouse gas (as the state's Public Utilities Commission is considering).

The new design involves building lots of low-to-ground, resilient mirrors instead of one ginormous parabolic mirror:

Mills's design -- a compact linear Fresnel reflector -- allows for greater ground coverage, lower weight and greater durability than precision-shaped parabolic mirrors. "You can drop stones on it and they bounce off," Mills says. "We would be able to build these in Florida in the hurricane zone."

This Fresnel solar thermal plant also eliminates oil, directly heating water to a lower temperature of roughly 535 degrees F (280 degrees C) at a higher pressure, about 50 bars, or 50 times atmospheric pressure. Then, it uses the resultant steam to turn the same low-temperature turbines as those employed in nuclear reactors.

The amount of electricity produced is simply a function of the sun's bounty and the number of mirrors. "We're moving from 80- to 100-megawatt designs to 700 megawatts and above," says John O'Donnell, Ausra's executive vice president.

Naturally, skeptics abound:

"The issue of the linear Fresnel concept is proof of performance of a large system, not just a prototype system in the field," says Mark Mehos, concentrating solar power program manager at the National Renewable Energy Laboratory (NREL) in Golden, Colo. Ausra and other companies that employ the same technology, such as New York City–based SkyFuel and Solar Power Group in Munich, Germany, "are making large claims," he says, "without testing in the field."

Of course, any renewable tech faces the same problem: they need a way of storing the electricity they make. Looks like Ausra's got that handled too:

"The maximum you can get into the grid is about 25 percent from solar," including photovoltaics, Mills says. But "once you have storage, it changes from this niche thing to something that could be the big gorilla on the grid equivalent to coal."

Ausra claims to have solved the storage problem without using molten salts or other expensive means of conserving heat. In fact, the company estimates that the price of its electricity will drop to roughly 8¢ per kilowatt hour if it can store heat for 16 hours. "Thermal storage is generally considered to be quite a bit cheaper than electrical storage," says Nate Blair, a senior analyst at NREL. "There isn't a lot of power generation combined with storage systems that can take advantage of that. [Concentrated solar power] has a leg up on storage in the grid or flow batteries or even ultracapacitors."

The system will employ pressure and a steam accumulator to accomplish the trick. "You allow some of the steam to recondense," O'Donnell explains. "It flashes back to steam when you reduce the pressure just by opening the valve to the turbine."

Of course that storage mechanism, coupled with baseload generation, is risky and unproven, but if it works out ...

... such solar-thermal power plants could match the electricity needs of both California and Texas. And, by combining a system that would meet the needs of California and Texas, solar-thermal plants could supply 96 percent of the national electricity demand. "The entire energy use of 2006, the current technology including storage would use a patch of land 92 miles by 92 miles," O'Donnell says. "Ten percent of the [Bureau of Land Management] land in Nevada is enough."

Wouldn't that be nice?

For story: All you need is ~~love~~ sun
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Twirling in the sun

Khosla, in addition to his other green investments, is placing a big bet on solar-thermal technology - what he considers the best weapon in the "war on coal power generation."
"Solar thermal has been ignored completely in favour of sexier photovoltaics," he says. "When I started looking at solar thermal early last year, I couldn't find anybody who was paying attention, which sort of surprised me. It's a great technology, and about one-fourth the cost of PV with the kind of reliability that utilities actually like."

http://www.thestar.com/columnists/article/250043

Ausra CEO Peter Le Lièvre.
Ausra, a Palo Alto, Calif.-based solar-thermal startup, came out of stealth mode Monday with an announcement that it raised "more than" $40 million from venture-capital firms Khosla Ventures and Kleiner Perkins Caufield and Byers.

http://www.greentechmedia.com/articles/ausra-raises-40m-f ...

"It's probably the most exciting time in my career," Dr. David Mills, 60, told Tyler Hamilton. "Better late than never." After years of trying to attract serious interest in his technology in Australia, Mills says he was getting ready to throw in the towel and retire. Then, last fall, he got an offer to go meet Vinod Khosla, followed by the folks at Kleiner Perkins, in October. "We clicked really well," recalls Mills. By February, Ausra got its first funding and by March the company relocated its headquarters to California and started hiring like crazy...
http://www.scribemedia.org/2007/09/11/ausra-gets-awesome/ ...

Davis Mills is the innovator and appears honest. But once you get in bed with CEO VCs then the spin begins, say anything to sell stock value. It is like the border-line ponzi scheme of the dot.com bubble.

This line-focus technology is very good as far as it goes. The positives are durability, low profile, smaller mirrors, low tooling, and fast scale up. The negatives are low concentration ratio, cosine losses (sun to mirror angles), large receivers, heat loss. Dual-axis point-focus (heliostat and dish) economics could spin circles around line-focus technologies.

Had Bush not "zeroed out concentrators" then NREL would supply peer review. Solar thermal and solar concentrator dreams are shared by all. Reverse economic engineering is easy. Missing, as usual, are hard cost and performance numbers.

by sunflower at 10:45 AM on 23 Sep 2007

Winter is still a problem ...

or anyway, the parts of it after the first 16 hours are.

--- G. R. L. Cowan, former H2 energy fan
Internal combustion power without exhaust --
http://www.eagle.ca/~gcowan/boron_blast.html

by GRLCowan at 10:57 AM on 23 Sep 2007

Seasonal power storage.

In a large system, one year high-temperature deep ground storage is possible.

That said, near-term storage will not be required for the first $200 billion solar thermal deployments.

by sunflower at 11:19 AM on 23 Sep 2007

Disliking spin from amateurs as you seem to...

and having in mind that there are people here who "trust you implicitly", when you say,

In a large system, one year high-temperature deep ground storage is possible...

by "high-temperature" how high do you mean, and by "deep" how deep, for, say, an electrical megawatt-month? I suppose that would have to be five or six or seven thermal gigawatt-days in the underground cache.

Collecting interstellar material to construct a 24-kt full-scale gold replica of the earth is "possible"; it just takes a long time, and the surface gravity is awkward for pedestrians, but it could be done.

--- G. R. L. Cowan, former H2 energy fan
Internal combustion power without exhaust --
http://www.eagle.ca/~gcowan/boron_blast.html

by GRLCowan at 4:32 PM on 23 Sep 2007

Oops

an electrical megawatt-month? I suppose that would have to be five or six or seven thermal gigawatt-days ...

For "gigawatt-days" please read "megawatt-months". I put in two references to the larger unit, then thought, that's an opening for him to say gigawatts are an outmoded, corporatist concept -- or some such thing -- and tried to change them all, without immediate success.

by GRLCowan at 4:39 PM on 23 Sep 2007

there are 3 numbers I'm interested in

3 numbers I'm interested in.

What is the ERORI of the best (which would be the cheapest) Concentrated Solar Power Plant. Energy Returned on Energy Invested, would tell you how much we got to put into these things to get our energy back. I think I remember reading onetime it's 4 to 1, which is really bad. What if the thing runs 30 years, it would take 7 years to get the energy back? That seems way to low. I'm looking. I wish I keep those links.

What is the ratio of wind in the summer compared to the winter in the midwest? I think it is 70 percent. (winter more wind than summer)

What is the ratio of sun for the winter compared to the summer in CSP areas, (CA.AZ.NM.TX) that might be somewhere around that 70 percent or lower.

Anyway, the place I would go with this is wind power from the windy states combined with solar power for the sun states, would be a good combination for year round power. Sure, there would be gaps, but just because there are gaps that would have to be filled with Fossil fuel plants, doesn't mean the combination couldn't be the majority of electrical power.

As I have read, 3 states, North Dakota, Kansas and Texas wind could replace all of the fossil fuel used for electricity. An area the size of Indiana or half of North Dakota in wind turbine area (1 1/2 percent of lower 48 states area) with 400 000 wind turbines at 2.5 MWatts each.

Does that make sense or not? Just hook the whole combo together at New Mexico and Kansas.

by trock at 6:24 PM on 23 Sep 2007

Concentrator ERORI less than one year

solar insolation charts
http://rredc.nrel.gov/solar/old_data/nsrdb/redbook/atlas/ ...

by sunflower at 8:40 PM on 23 Sep 2007

I don't know if this particular idea will work

but I am pretty confident we will finally hit on one that will.

In the end, it all comes down to biodiversity. Poison Darts--Protecting the biodiversity of our world

by biodiversivist at 11:02 PM on 23 Sep 2007

All you need is a $20/ft2 mirror tracking the sun.

All prospectors need is a ream of blank paper and sharp pencils.

by sunflower at 6:39 AM on 24 Sep 2007

GRL, my head is in the sand

and in the fog from a 20 mile Sound kayak adventure.

If this mornings calcs are correct then sand 100 feet deep by 500 x 500 feet square at a delta temperature 250 degrees F. (750 - 500 F.) equals 4 gigawatt-years thermal.

by sunflower at 7:17 AM on 24 Sep 2007

ERORI of less than year would be good

ERORI of less than one year would definitely be good. I think I did see ERORI of 4 for CSP, but that may have been someone trying to be negative to CSP and be pushing some other form of energy. It's so hard to get real numbers for stuff. Of course, who measures it has something to do with it as well, some might include the energy of workers to drive to work. Depends on what you want to do with the numbers.

I've read that wind turbines are 3 months to 9 months.

Photovoltaics are 2 years, hence their cost.

by trock at 7:38 AM on 24 Sep 2007
[ Parent ]

CSP pays back setup energy in weeks, like nukes

I worked out a crude upper bound, plus a little farther along in that discussion managed to set down plainly how EROEI almost never matters:

How high could the EROEI have been of something that fossil fuel energy undercut on price shortly after 1912? The fact of the undercutting does not imply any limit. It could have been a million, and if gross energy from fossil fuels had to be, just to pick a number randomly, 13 percent ploughed back into getting them -- EROEI 7.7 -- fossil fuel could still shut down the solar industry if that gross energy were cheap enough. In fact to beat a source with infinite EROEI, if all other costs are equal, a source with 7.7 EROEI just has to use gross energy that is 13 percent cheaper. Since all other costs are never equal, and lots of things are scarce besides energy, even that isn't guaranteed.

--- G. R. L. Cowan, former H2 energy fan
Internal combustion without exhaust --
http://www.eagle.ca/~gcowan/boron_blast.html

by GRLCowan at 10:20 AM on 24 Sep 2007

How about a sphere

If this mornings calcs are correct then sand 100 feet deep by 500 x 500 feet square at a delta temperature 250 degrees F. (750 - 500 F.) equals 4 gigawatt-years thermal.

A block 500 by 500 by 100 seems unnecessarily high in surface area per unit volume; especially at the corners. Its heat would leak away quicker than from a sphere of diameter 362.8, which has the same volume.

One would have to be sending hot fluid down a pipe network when the sun was shining, and having a spherical region percolated by those pipes warm up. Supposing the sand to be pure silica, in a temperature range centred at 625 Fahrenheit, ~600 K, its heat capacity is 64.42 joules per mole-kelvin, that's 1.072 megajoules per tonne-kelvin, and over a 139-K delta 'T' that makes 149 megajoules per tonne.

And in the cold months, the fluid would be sent down cold and come up hot, and boil water that would turn a generator; the pipes would have to get close enough to every part of the sand sphere that heat could get from that part to a pipe within a few weeks in winter, and the other way in summer.

I'm curious what diameter you get for a spherical region holding enough thermal megawatt-months at the mentioned 149-MJ/tonne loading to make one electrical megawatt-month.

--- G. R. L. Cowan, former H2 energy fan
Internal combustion power without exhaust --
http://www.eagle.ca/~gcowan/boron_blast.html

by GRLCowan at 12:48 PM on 24 Sep 2007

Seasonal heat storage engineering.

I am not an engineer and was only projecting from 90 C. Swedish systems. The 100 foot depth comes from typical pile driving depth of wells. The field circumference is often a polygon. The heat exchange is serial, starting (or ending depending on direction) at the edge and working inward towards the center. Dry sand has poor heat transfer, requiring more wells. Rock is ideal but more expensive to drill. High temperature storage needs intensive engineering followed by hard data on cost and performance measured from prototypes. Currently, it is just an old concept, a possibility.

I purchased a mothballed 700 psi pressure tank from the Satsop nuclear plant, 10 feet wide, 40 feet long, 2.5 inches thick, stainless lined, weighs 45 tons, cost $500,000 when new. If that is what the solar-thermal company Ausra is using for high-pressure high-temperature storage, then that would be both expensive and dangerous. I wonder how adding big expensive storage tanks reduces cost from $0.10/kWh to $0.08/kWh. Perhaps it is because they get better capacity factors from expensive heat engines. But, to get to those numbers, their heat engines would need to be really cheap. Those solar thermal numbers are possible, just difficult, especially for line-focus single-axis tracking concentrators and mid-temperature heat engines. Ausra sounds aspirational to me.

We need the solar thermal budget restored at NREL, ASAP.

by sunflower at 1:28 PM on 24 Sep 2007

As I keep mentioning

Sun energy is something which we sure do have a lot of :)
http://greyfalcon.net/greenenergy.png

by GreyFlcn at 1:49 PM on 24 Sep 2007

"I am not an engineer"

That doesn't really let you out of doing proper calculations if you're going to talk like one. If spherical geometry is too hard, please at least review your 500-by-500-by-100-foot slab calculation.

--- G. R. L. Cowan, former H2 energy fan
Internal combustion power without exhaust --
http://www.eagle.ca/~gcowan/boron_blast.html

by GRLCowan at 9:14 AM on 25 Sep 2007

I did not peer this luau

So I dropped it. In round numbers from my failing memory -- One pound of sand is 0.2 Btu/F. One cubic foot is 100 pounds. 3413 Btu=1 kWh(t). At a temperature change of 250 F. 1 ft3 sand = 1.465 kWh(t). 100 x 500 x 500 feet = 35 GWh(t) = 4 MW(t) years. If used for 16 hour power at night then the power is 2 GW(t). If $1000 heat wells are every 10 ft2 surface then the cost is $25 million, $0.01 per Watt(t). Sounds wild.

by sunflower at 10:02 AM on 25 Sep 2007

Much better

... One pound of sand is 0.2 Btu/F. One cubic foot is 100 pounds. 3413 Btu=1 kWh(t). At a temperature change of 250 F. 1 ft3 sand = 1.465 kWh(t). 100 x 500 x 500 feet = 35 GWh(t) = 4 MW(t) years...

Thank you, four thermal megawatt-years sounds a lot better than four thermal gigawatt-years, which is a thousand times more.

... If used for 16 hour power at night then the power is 2 GW(t)...

I don't follow that. I thought the subject was a couple of thousand dark winter hours, day and night both, and having heat available through that time because during the ~1,000 brightest hours of summer it was put by.

--- G. R. L. Cowan, former energy fan
Internal combustion power without exhaust --
http://www.eagle.ca/~gcowan/boron_blast.html

by GRLCowan at 10:57 AM on 25 Sep 2007
[ Parent ]

I am also not a politician

Baseload winter solar power has sexy political connotations but it is not relevant for big markets, does not wag my tail. There might be a niche market after the first $ trillion has been deployed for 24 hour solar power. District heating/cooling with seasonal heat storage makes more economic/political sense.

I am not convinced seasonal solar power storage is useful. If the solar system is double sized for power and storage input then it is big enough for winter power output without storage. Middle ground? Three months of supplemental heat storage might cost $1/Watt(t). If solar HIPV costs $1/Watt(e) then it might be more profitable to oversize the solar power plant for summer conditions. It all depends on technology cost/benefit and market demand/supply. I suspect winter loads are less due to summer electric air conditioners.

by sunflower at 11:38 AM on 25 Sep 2007

EROEI isn't the most important measure

I agree that EROEI isn't the most important measure. It was just an indication of whether it is worth doing. Like ethanol, which is only worth doing politically, not for the energy gotten out of it.

I've read that if coal plants were required to buy all the coal they needed 30 years ahead of time, that would make them uneconomical. (not hard to imagine) That's what a solar or wind plant has to do, basically buy all their costs upfront in more material and design costs in machines that harvests the sunshine or wind.

Also their value as reliable power, whether peak, shoulder, base or none of these.

I could imagine that if some of these get built and the claim of cheaper power is working, they still could be combined with the CSP's that have the higher working temperature. It's important at the turbine to get as high a temp as possible and the combination of the lower cost, lower temp collectors as a step to the higher cost, higher temp collectors might make for a better system. But they still have to get them to work for now.

by trock at 12:40 PM on 25 Sep 2007
[ Parent ]

Cost reduction is where all the fun is.

Reducing cost is the challenge, the fun. No matter how cheap solar gets, it can always get cheaper. Remove one bolt, one dollar, and you make a million on a million collectors. Cost engineering requires discipline for simplicity. Like simplifying writing, simplifying technology requires thought, time, and effort.

Low temperature systems do not cost less than high temperature systems. Flat plate collectors cost more than line-focus collectors, which cost more than point-focus collectors. It is materials intensity, not temperatures, that drive costs. Other significant variables include ground support v. steel support, system lifetime, O&M, annual energy performance, tooling, indigenous scale-up, labor skills, cost of capital, and overhead. The $40 million for Ausra will generate an overhead ache for cost reduction. I can not imagine why they need so much money.

by sunflower at 1:12 PM on 25 Sep 2007

thermal storage

Storage can be used to keep the power output stable and maybe extend a little but until the majority of daytime needs around the country are met, storage won't be needed. This can be used once coal and other dirty sources are being used only for night time generation. Then it can finish phasing them out.

Ground solar thermal storage should start taking off for home heating any day.

by solar greg at 2:57 PM on 25 Sep 2007

ADVERTISING POLICY

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