Ausra Building First U.S. Production Facility for Thermal Solar

Ausra Inc., a developer of utility-scale solar thermal power, announced Friday it is building the first U.S. manufacturing plant for solar thermal power systems, in Las Vegas. The 130,000-square-foot, highly automated manufacturing and distribution center will produce the reflectors, towers, absorber tubes, and other key components of the company’s solar thermal power plants.

“Ausra can fill four square miles with solar collectors every year from this one factory, enough to provide market-priced zero-pollution power to 500,000 homes,"

Bob Fishman, president and CEO of Ausra.

In November 2007, Ausra and California utility PG&E announced a power purchase agreement for a one-square-mile, 177-megawatt power plant, enough to power over 120,000 homes, to be built in central California

The production plant will begin regular operation in April 2008. Ausra’s new Las Vegas facility will manufacture the solar field equipment for the PG&E project and for other power projects throughout the American Southwest. The factory, the first of its kind in the U.S., will be capable of making over 700 megawatts (electric) of solar collectors per year.

In Ausra’s Compact Linear Fresnel Reflector (CLFR) solar technology, previous post, flat mirror solar collectors focus the suns rays on tubes filled with water, rather than a heat transfer fluid, thus directly producing steam to power steam turbine generators, in much the same way as traditional fossil-fuel power plants, but without use of fuels or emissions.  Ausra's solar collectors will be mass-produced, using lower cost flat mirrors, rather than curved troughs, and sit low to the ground reducing wind loads.

Storage of heat from solar power plants can allow solar power plants to operate around the clock. David Mills, Ausra's founder and chairman says that solar-thermal plants are preferred because storing heat is much easier than storing electricity (as from wind power or PV solar). Mills estimates that, thanks to that advantage, solar-thermal plants capable of storing 16 hours' worth of heat could provide more than 90 percent of current U.S. power demand at prices competitive with coal and natural gas. A proprietary heat-energy-storage system being developed by Ausra should be ready by 2009.

Ausra claims that It can generate electricity for 10 cents/kWh now, under 8 cents/kWh in 3 yrs. It also claims that using Ausra’s current solar technologies, all U.S. electric power, day and night, can be generated using a land area smaller than 92 by 92 miles.

Ausra, Inc.is a privately held company funded by Khosla Ventures and Kleiner, Perkins, Caufield & Byers.

Comments

[bigTom]

Tis a start. 700MW (peak?)/year is unfortunately barely a drop in the bucket. Hopefully once some actual operating experience is gained output can be ramped up several fold. Does anyone know what they mean by 700MW. Is that peak capacity (i.e. at full sun), or averaged over say a 16hour/day with thermal storage. The difference is significant.

[Nathan]

92 x 92 = 8464. At the rate of 4 square miles a year thats roughly 2100 years. Of course this can be increased with more plants and greater efficiency. 100 plants in 20 years? Seems somewhat doable when compared to the enormity of the current electrical infrastructure.

I imagine many of those plants will need to keep running for replacement parts 20 years down the line, so these aren't just temporary job creations.

[Paul H.]

The whole southwest is a wasteland of hot bare ground. What on earth is stopping the U.S. from doing this? Liquid Coal??!! What? Does Mitt Romney have special needs?

[Kit P]

“Ausra Inc., a developer of utility-scale solar thermal power,...”

They mean 'wanna be' developer. There is a way that utility-scale developers of steam electric station do business, there is a way the clueless do business, and there is a way scam artist rake in the cash.

Just because the best developers have failed to deliver a utility-scale solar thermal power plant does not mean the clueless are doomed to fail.

[Nathan]

Not sure what you are saying... Why would scam artist keep the company private? Although if Khosla is involved, its bound to be wasting money.

[Lad]

I would hope a company like P.G.& E. would check out their contractors before committing financial resources to a project.

There have been projects similar to this one for some time. The Daggett, California thermal power system has been online since 1986-7 and has proven the idea is feasible.
http://www.solel.com/products/pgeneration/ls2/daggett/

[DaveMart]

BigTom, I'm pretty confident that this is 700MW of peak capacity.
Of course this is not enough to totally replace capacity in the States, but all they need to do (all!) is bring in power at less than their target of 10c, and hopefully demonstrate their steam storage technology, and more capacity will rapidly get built.
I really like this technology, as it follows KISS, and every expense has been spared whenever possible.
Not sure how its a scam, as Khosla has put in several tens of millions of his own money, and I thought the idea of a scam was to take someone elses.

[Cyril R.]

It's always peak capacity isn't it? And their proprietary water based storage system isn't ready yet. 2009? Why, it sounds so simple.

Although this may be a drop in the bucket, at the same time it's important to realise this is the biggest real solar manufacturing capacity announcement ever!

They've shown a fairly aggressive manufacturing schedule so far, especially for a solar thermal electric manufacturer.

[Kit P]

Lad thanks for the link.

The difference between a scam and the clueless, is who money is being wasted while electricity is not being produced.

FPL would an example of a company that is a utility-scale developers of steam electric stations. FPL is also good at picking up failed projects at fire sale prices and making them work. In the Solel press release we find that the original solar collectors are being replaced. We also know that FPL augments solar with natural gas.

In another Solel press release, “Solel's receivers will provide power to the Nevada Solar One solar thermal power plant, scheduled to go on-line with commercial production sometime this year.” However, I have been waiting since May for the press release that the project is working.

So what do we know so far about solar. It feasible but does not work yet. The inept fail, the good have made it work for a little while with adequate incentives. Solar is clearly not what has been advertised. Maybe someday. Wait for it! What about cold fusion?

[DaveMart]

It's nice to see that Ausra's figures allow for actual output, rather than peak.
At around 200MW per square mile, rounding up, and also rounding up their 92sq mile block to 100miles square so you have 10,000 miles to play with, gives you a peak output of around 2,000GW, so they are giving an efficiency of around 25% for the needed average output of around 500GW for electricity in the States - the right kind of figure.
No question that you are talking about a lot of land though, at average output of around 40MW square mile.

[david foster]

I like the inherent energy storage capability of solar thermal, which seems like a real advantage over photovoltaic. But I wonder about cooling-water considerations: In a typical steam-turbine plant, water from a nearby river or lake is used to condense the steam for reuse. (I believe this can be avoided with cooling towers, but at a cost in efficiency.) So perhaps solar-thermal plants are more restricted in their location options than are PV plants.

[Ronald Brak]

Is solar thermal's ability to store energy as heat a large advantage over photovoltaic solar? As it shouldn't be difficult to use electricity from photovoltaics to efficiently generate heat, does solar thermal have a significant advantage in providing baseload power?

[Ken]

The technology is pretty basic and avoids the high cost aspects of other solar thermal systems - no parabolic mirrors, just flat glass flexed to a shallow curve, fixed in place collector pipes, direct heating of water, galvanised steel construction. Why wouldn't it work? This is a technology that is safe to set up in any nation with sunshine, not just "good" ones. No watchdogs and international regulators needed, just straightforward engineering certification for steam vessels.

[DaveMart]

Ronald, at current costs for PV thermal has a massive advantage, even before taking into account the further cost savings inherent in Ausra's approach.
Of course, that could change if someone like Nanosolar is successful in it's plans to greatly reduce PV costs, but it is the case at the moment.
The easier storage bit does not really relate to use for base-load, but to using electricity you collect during the day-time at night.
That is difficult and expensive for electricity - batteries and so on are expensive.
If they did as you suggest and used the electricity to generate heat and stored that, then generated electricity again from the heat, you would loose efficiency at every stage in the process, it is much simpler to store the heat in one go, then generate electricity from it.
Ways of storing heat include molten salt and heating up concrete, but apparently Ausra is choosing to store the steam directly.
How that will work out is the most uncertain part of the project.
Initially it seems they plan to extend the time you can generate electricity by about an hour, which they say will improve economics and obviously reduces storage needs compared to trying to generate electricity 24 hours a day.

[Angus]

If the land use is an issue then why not try and combine it with Geo Thermal or wind turbines to reduce the footprint?

Seems to me that Nevada has some pretty good Geo Thermal sites so this solar thermal technology would be a good addition. Also maybe the used steam could be pumped back into the Geo Thermal units to avoid cooling or vice versa.

No doubt the idea has some merit. With regards to land use, a 2900MW dam is proposed for Northern Canada(Labrador) and the area to be flooded is in the thousands of square miles. No system is innocent in regards to this.

[DaveMart]

The land can also be perfectly restored when not needed fro generating electricity.
The topped mountains in WV from excavating coal aren't going to grow again, and the lakes full of tailings from oil from sand in Alberta aren't going to go away.

[Kit P]

What 'inherent energy storage capability of solar thermal' are you referring to? A certain amount of thermal storage must be provided just to keep the plant from destroying itself if a cloud passes over. When a steam turbine self destructs be someplace else or be dead. Radiative heat transferee works both ways.

A huge amount of heat storage is required to provide any capacity to provide power to summer peak demand. An incredible amount of storage will be required to produce electricity 24/7.

[Ronald Brak]

Thanks for your answer DaveMart. Giving it some thought I realize that although we can convert PV electricity into heat with pretty much 100% efficiency, that's not the only thing that needs to be considered. Solar thermal may be about 20% efficient at turning sunlight into electricity, but would actually be much more efficient at storing heat than PV, making it much more suitable for this purpose.

[DaveMart]

From the figures they have given it looks like Ausra are only counting on their process being 7-10% efficient.
Four square miles for a peak output of 700MW works out to around 70watts a square meter, and they should presumably be counting on around 1kw a square meter as maximum incidence.
Of course we don't know how much of the land area Ausra would leave clear, or even if such area is included in their 4 square miles, nor do we know if their 700MW is before or after storing some of it and re-releasing it to generate electricity.
Ausra have already said that they sacrificed the maximum possible output per square meter to keeping things simple to keep costs low though.

[david foster]

Kit..the Ausra site is quoting energy storage of 16-20 hours. At least one of the references suggests that they are using underground cavern storage.

Even if the storage capacity was only 1-2 hours, that would surely be far superior from a standpoint of grid stability than instantaneous or nearly instantaneous fluctuations from an unbuffered PV plant.

[DaveMart]

'Using reasonable financial assumptions, the table above shows that Ausra’s current
CLFR solar array technology combined with 700MWe turbines and 16 hours of thermal
energy storage could deliver energy at costs that are directly competitive with new gas- -
fired generation facilities and much cheaper than coal-fired plants with sequestration.'
That's from Ausra's pdf.
Couldn't find the reference to caverns though, and I had assumed that they were talking about building containers for pressurised steam.

[bigTom]

As a fan of CPV, whereby (relatively) cheap reflector area is used to take advantage of high performance multi-junction cells (40% efficient) I think there is promise (by not yet fact) for somewhat cheap PV utility sized plants. Such units would not have the output buffering possible with solar thermal, but high system efficiency and smaller footprint is at least possible. If collectors are placed overhead it is possible that the land could be dual use, say PV generation and grazing, or PV generation and urban/subburban mall parking lot etc. It certainly seems possible to me that we won't have to sacrifice a lot of land to utilize solar.

[DaveMart]

Hi bigTom,
Couldn't agree more.
In the end,no one technology is going to sweep the board.
Statements like the one from Ausra that a square 92miles on a side could power the US are only useful in that they help to safeguard against wasting money on minor solutions which cannot make a major contribution (cough, ethanol from corn cough)
One of the concentrated solar ideas I saw is in the form of panels for people's roofs:
http://www.technologyreview.com/Energy/18718/
this would minimise costs of transmitting power to where it is needed too, besides obviously economising on land.
It seems likely that costs should reduce in PV production of power in one way or another by a substantial amount within the next ten years or so,and whilst storing the power may be more difficult it is by no means impossible and there are other advantages which will make it a serious contender.

[bigTom]

davemart:
Soliant might be a reasonable solution for the homeowner who insists on generating his own power. I think the real future of solar is utility scale projects. These have an economy of scale -perhaps even having a full time expert to insure proper maintainance etc. Soliant might have a good idea, in that bulk solar trackers probably can't be made very cheap and may present maintainance issues. Using micromechanical devices internally for small scale tracking would be a way perhaps to leverage advances in micromachining. I suspect distributed building integrated PV will likely be low efficiency thin film, that is economical only because of its low cost -and possibly because we charge more to deliver power to end users, than we pay for power at the powerplant.

[Cyril R.]

CPV would be more effective (that is, it could have a big market share) if an efficient, cheap, scalable, environmentally friendly method of storing electricity would be available. Untill that is available, solar thermal seems to have an edge, at least in principle...

[DaveMart]

Thinking further about integrating concentrated PV with solar thermal, it occurs to me that Ausra are not planning on storing all their production.
So, if the target is around 16hours begerating capacity, then you might have to store around 1/3rd of the energy produced to meet this target.
Now let's suppose you build two plants, one using Ausra's technology, efficient to around 7-10%, the other solar concentrating, efficient to perhaps 30%.
Of course, tracking wound have to be better on the concentrating plant, but you would need a lot less of it as the plant would be only around 1/3rd the size for a given output - but let's build it to the same size as the Ausra plant, so that 3 out of every 4 units of electricity produced would be from the concentrated plant.
Now let's back up the Ausra plant at 100%, instead of the 1/3rd or so Ausra are apparently planning at the moment.
So you now have a combined system which uses the strengths of the thermal system, ie easier storage, and the compactness of the concentrated system, as you are saving 1/2 the space you would have taken up with a purely Ausra system.
My figures don't match exactly, as for simplicity we are only generating .25 of the power from the Ausra system, not the requires .33 and so on.
Just the same the principle is clear.
If, and it's a big if, the Ausra system allows economical storage of energy, it will facilitate not hinder the development of utility scale concentrated PV, which can go and do it's thing of producing maximum power when the sun is shining, with load following taken care of by Ausra.
For completeness it should be noted that some thermal plants at the moment are combination plants, using natural gas for the load following, and solar for tracking the sun.
So that there are half-way houses available, if the technology is not 100% successful at first, which would still demonstrate large savings in carbon dioxide emissions.

[Cyril R.]

DaveMart that is an interesting idea.

However you won't be getting such high efficiencies from current generation high flux CPV plants because of mirror spacing and geometry. This ground utilasation is very low in conventional dual axis trackers, and line-focus CPV has so far not been cost effective due to the lower concentration ratios (which means more of the very expensive high efficiency cells per unit of power).

Perhaps an MTSA design could be a solution?

[DaveMart]

Interesting stuff there, Cyril.
Don't you start bringing actual engineering into the debate here though!- Amazingly, hand waving and appeals to 'technological progress' and 'mass production' seem to be more popular! :-)
I think the splitter idea that you reference is further proof that solar thermal with or without storage and PV are not inimical, cut complimentary.

[bigTom]

They could be complimentary, with the thermal being used for the nighttime part of the picture. Of course if the cost/KWhr differ substantially then I would expect the cheaper system to dominate.
I have no problem with backing up solar-thermal with NG. Used in such a way the solar component stretches the NG fuel supply. It may not be satisfying for purists, but building a bride towards largescale generation should take precedence.

[Cyril R.]

The MTSA could also be constructed over parking lots or on top of large buildings so space use would be multifunctional.

Beam splitting is certainly an appealing option, although it may be a bit too ambitious for the immediate future. At any rate, land use is rather a non-issue right now, considering how little surface area these proposed project will require - several square miles per year. The most suitable Mojave land typically cost only a few bucks per square meter, and there's several thousand GW available even when strict criteria are used.

Even if they ramp up to, say, 7000 MWp/year (a serious accomplishment) it won't be a problem in our lifetimes.

And solar thermal efficiency could still be improved incrementally but continuosly over the next decades. Improvements in site geometry, mirror spacing, mirror reflectance (they're using cheaper mirrors right now) turbine efficiency, higher heat regimes, novel turbine cycles and materials (ceramic turbines?), alternative working fluids with lower evaporation temperatures such as ammonia/water solutions instead of pure water? Or propane maybe in Kalina cycles or... oops is that too much engineering? :)

[Cyril R.]

BigTom, Ausra seems to think that hybridization comes with a lot of extra capital costs for their design. They think that low temperature operation is cheaper, especially if combined with large relatively cheap turbines where the water can be flashed in directly, and even more so if their water based storage system is as cheap and good as they say it'll be. It's almost 2008 now, 2009 isn't that far away...

[Cyril R.]

I also like the idea mentioned above by Angus, of using solar thermal heat to boost geothermal production. The same power block and BOP equipment could be shared. Perhaps this could also increase the average temperature of cooler wells that otherwise wouldn't be economical or practical to exploit? It could certainly increase thermodynamic efficiency. Binary geothermal plants using propane as working fluid can yield relatively high net turbine efficiencies with lower temperatures. The solar thermal part would just provide heat, which Ausra has proven already in the Australian coal reheater project to be cost-effective.

[DaveMart]

That system of MTSA where it is stationed on roofs sounds weird to me.
I though a lot of the expense of these systems was in the actuators and so on to move it around to get the sun right?
The really small reflectors you would need to put them on roofs sounds as though the cost would be prohibitive.

[bigTom]

Cyril: you may be right about hybridization (solar-thermal plus NG). If the working temperature is low, the thermal efficiency suffers. We could end up burning the NG for low efficiency conversion to electricty.

Dave my presumption with Soliant was that the collectors contain a combination of sensors/actuators to maintain focus/tracking. The concentration efficiency is low (maybe 10 times) likely precluding the use of high efficiency multijunction cells. I think they were thinking of second generation with 2D concentrators, higher amplification/smaller area of silicon, but tougher tracking. In any case small scale moving parts which are protected from the weather would seem to be a plus. SolFocus's system is much more elegant, but the entire panel must be mounted on a large scale tracker.

[Randy Lee]

Say, speaking of sequestration, wouldn't it make more sense to duct the CO2 to a plant growing structure like a greenhouse? Instead of the sequestering plant? Then the CO2 would be sequestered as food for people to eat instead of useless inert salts.

[Luigi Aronson]

I really like the Ausra solution. First of all, 92 square miles is ten per cent of the federal land in Nevada. You could put these power stations over land already turned to trinitite. So I think that land area is not an issue for CSP.

This is a cheap easy solution. Environmentally clean, maintenance should be easy, it is a typical steam plant. They should outsource the steam plant manufacture.

As far as energy storage, I think storing heat and compressed air will not be the answer. I think the massive battery, in the vein of Altairnano is prototyping for AES will be the answer. Once again, low maintenance will be the reason.

Read the ausra solar thermal 101. Looks like Vegas will be sin city and sun city.

[Kit P]

I think Luigi should build and work at “power stations over land already turned to trinitite” and then he would learn the fallacy of statements like,

“This is a cheap easy solution. Environmentally clean, maintenance should be easy, it is a typical steam plant.”

People who make electricity love cheap easy solution that are environmentally clean because they usually live near the power plant that is why solar is mandated by clueless. Good engineers can make it viable. However, wind and solar are not good environmental choices because they are not good ways to make electricity.

[paul]

Has anyone made economic comparison between concentrated solar farms that are thermal versus multi-junction PV (~40% at 500 suns)? http://www.solarsystems.com.au/154MWVictorianProject.html
I would guess going straight to electricity with concentrated PV (without the expense and inefficiency of steam-to-electricity), would be significantly more economical, even with the greater expense of multi-junction cells.

[DaveMart]

That is pretty much what the different pilot plants will do, move the assessment of the output and potential of the various technologies on and give proper figures.
Going straight to electricity via PV though would negate one of the claimed advantages of the Ausra system though, the ability to cheaply store energy.

[Cyril R.]

We could end up burning the NG for low efficiency conversion to electricty.

Yes bigTom that's what I was worried about too. We're probably looking at 25-35% for hybrid NG efficiency in the solar thermal plant. Combined cycle NG plants are 55-60% efficiency. Plus, they can be relatively compact so they can be put in more urban areas, with the waste heat used to supply nearby buildings with low grade heat. Or even high grade if there are high grade heat demanding industries nearby. You can then get 85% total efficiency.

Modern domestic water boilers are already above 90% efficiency. Although in this case it would usually be better to get as much as the heat as possible from solar thermal panels and use the NG for efficient backup, or even hot water on demand (electric).

[Cyril R.]

Another option that seems promising is an MTSA thermal only design. With point-focus systems, very high temperatures can be reached, because of the high concentrations possible, without too much receiver losses simply because the receiver is relatively tiny. 60% turbine efficiency might be possible if an alternative working fluid is used.

Then, we'd get

90% beam utilization
90% mirror reflectance (silver backed are higher but there will be some dirt losses despite regular washing)
95% receiver efficiency (maybe sputtered cermet coatings)
60% turbine efficiency
5% system use

about 44% total efficiency. And low cost thermal storage systems could still be used.

Now, if you're an idealist, beam splitting could be added in as well for even higher total efficiency and more peaking power.

[Cyril R.]

About peaking power: it just occured to me that if rooftop PV becomes really succesful in the future, and there will be significant grid upgrades so that all this can be fed into a large grid, then wouldn't we already have a lot of solar peaking?

CPV might have a hard time competing against rooftop PV as it's wholesale vs retail prices.

If they can compete, then it's down to future developments in storage again...

[bigTom]

CPV might have a hard time competing against rooftop PV as it's wholesale vs retail prices

I can't believe we would continue to allow retail pricing for selling excess PV back to the grid, if PV became pervasive. At some point that model just doesn't work economically (unless the government pays for the grid). Nevertheless it seems very likely to me that PV consumed internally by the homeowner/small business owner would probably displace retail power.

[Cyril R.]

Well it could a be slightly lower than retail feed in rate to cover up for T&D costs. There's usually a rather big difference between retail and wholesale costs.

Government vs private grid is a very important point. The Europeans appear to follow a model that looks like a mostly government controlled grid but liberal generation. At least, that's what they're trying... Perhaps some form of non-profit body would be needed to ensure grid availability and minimal outage. At any rate, major investments have to be made for improving and extending the current grid. Would private companies be willing to pay for it all by themselves? Probably not. Or not fast enough...

[sheila]

I'm just joining this conversation, but I'm concerned about a few points raised.

Firstly, I'm a fan of having ALL COSTS of a product, including energy, be paid entirely by the consumer of the product, a TRUE "free market" approach, rather than the current model of socializing the costs (global warming, total destruction of wilderness with solar arrays, enormous subsidies for pet projects, etc.) and privatizing the profits (utilities).

No doubt that will make me unpopular because the entrenched thinking seems to be that there is NO cost to completely obliterating ecosystems (even though the switch to renewable power is ostensibly to prevent the obliteration of ecosystems via GHG), and there are enormous costs to highly centralized grid functions with heavy remote-generation and lengthy transmission models (market manipulation, fire, blackouts, etc.) which are not accounted for when comparing to local, decentralized generation (PV greatly reduces thermal heat island effects, for example).

Anyone else here see these themes?

Secondly, I keep hearing mixed messages about the technical process of "net metering" from PV - is the structure powered first, then the excess fed to the grid (which would make Cyril's last point moot, since widespread PV would actually GREATLY reduce grid loads), or is all power fed to the grid, and all power sucked out of it in an unrelated way other than the net for billing purposes? If the latter, wouldn't a grid upgrade be terribly cost-effective for utilities who get any over-production of power from PV for FREE?

thanks!

[Clee]

How net metering works depends on where you are. In California, where I am, the structure gets powered first and the excess fed to the grid. In some other state it's common to have two meters, one for power going from the grid into the home and a second meter for power going from the home to the grid. This enables separate prices depending on which way the power is flowing. I think typically the structure still gets powered first, but I'm not absolutely sure.

But even on short winter days, our rooftop PV array generates more power than we use around 1pm, so we feed power to the grid at 1pm, even though if you tally up the whole day, we use more power from the grid than we put in. It can cause a big problem if solar ever becomes a significant portion of the electric supply (if the storage issue isn't addressed). But it's not really a problem at the current less than half a percent. That's why there is a limit to how much net metering a utility is required to accept. In California the limit has been raised to when the total rated generating capacity of net metering customers reaches "2.5 percent of the electric service provider's aggregate customer peak demand".

[Cyril R.]

I keep hearing mixed messages about the technical process of "net metering" from PV - is the structure powered first, then the excess fed to the grid (which would make Cyril's last point moot, since widespread PV would actually GREATLY reduce grid loads)

You've overlooked something. Lowering the feed-back tariff slightly below retail will stimulate homeowners to use more of their own PV production. Because they get less for feeding it back into the grid. Which actually enforces your point that the structure would preferably be powered first.

The feed-back tariff doesn't have to be much less. Say, 90% or 80% of retail. It would depend on how much PV there is on the grid. The difference between utility costs/kWh and retail consumer price/kWh is usually really big so that's still quite significant and there's plenty of room to play with.

Besides, transmission costs will never be zero (no really) so you'd have to lower the feed-back tariff slightly anyway.

Solar PV can also be quite unreliable sometimes. Even with geographical distribution - and that would increase transmission investments and thus costs - other power sources would have to make up for the difference/backup. So I think significant transmission costs are what we're looking at one way or another.

And then there's the fact that there just isn't enough good rooftop space available for PV to provide all electricity.

What's important is that solar-thermal has some enticing advantages over solar-PV. Cheap storage and cheap biogas/biosyngas emergency backup can make solar thermal as reliable as nuclear powerplants. You just can't do that with PV alone, batteries are very expensive and don't provide emergency backup from longer periods of less sunshine.

PV could contribute, but if you think all of the US could be mostly powered by PV without problems or additional externalities, and at a cost most would be willing to pay, you need a reality check.

[Cyril R.]

Oh, and your comments about "destruction of wilderness" and "completely obliterating ecosystems" were hilarious.

Perhaps you should consider going to Cramer Junction sometime and see how rediculous those comments really are.

[Cyril R.]

Even Greenpeace, considered by many the world's leading environmental/eco-nutty/irrational propagandist, tells us that solar thermal power has "little adverse environmental impacts".

Do you really need more authority than that :)

[DaveMart]

Greenpeace does tend to have solar as one of their 'pet projects' to use Sheila's phrase, and sometimes I feel that they pretty readily discount damage form the sources which they have predetermined to be 'good' - for instance noise and obliteration of beauty spots with windmills.
In general though, I would agree that solar PV and thermal promise no obliteration of ecosystems, although there could be local impact.
A darn sight less than coal though.