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Solar baseload outshines ‘clean coal’ — and it always will

By Joe Romm

"Solar baseload outshines ‘clean coal’ — and it always will"


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Concentrated solar thermal power — aka solar baseload — remains hot. The Daily Climate has a nice update:

All told some 60 plants are either under construction or under contract worldwide — with most in either Spain or the United States — for a total capacity just north of 5,700 megawatts

Here is the world list of projects. Here is the U.S. list.

I remain as convinced as ever that solar baseload could well be The technology that will save humanity,” in large part because it is highly scalable, eventually able to achieve 50 to 100 gigawatts a year growth or more.

Indeed, given the immense challenges that coal with CCS faces (see “Is coal with carbon capture and storage a core climate solution?“), I’m still happy, indeed eager, to bet that concentrated solar thermal will continue delivering more power every year this century than so-called “clean coal” — and at a far lower cost per kilowatt-hour.

Solar baseload’s ultimate “trump card” is, of course, storage:

The ability to store power for later use is a holy grail of sorts for renewable energy developers. Wind and photovoltaic plants force utilities to use the power on the spot or dump the load. Various batteries and capacitors are in the works for those technologies, but none so far match the smooth efficiency or low cost of solar thermal’s ability to hoard sunlight.

A plant designed with storage can shunt the hot oil from the mirrors to a giant insulated heat sink — a vat of molten salt, say, or a chunk of concrete or pig iron. Then after the sun sets but while demand remains high, that heat can be tapped to generate steam.

Or if a cloud rolls over a plant’s mirrors, or an afternoon thunderstorm stalls overhead, hundreds of megawatts of juice won’t suddenly drop off the grid. Utility operators can simply tap the tank.

“We’ve sort of stumbled on this thing with storage,” said Tom R. Mancini, program manager for concentrated solar power technologies at Sandia National Laboratories in New Mexico. “The round-trip efficiency is 90 percent…. Solar thermal is made for this.”

Arizona Public Service is building a plant that can keep the sun’s power for six hours past sunset, allowing managers to meet evening demand with midafternoon sun. A utility in Spain hopes to develop a plant that can keep heat for seven. Engineers figure 14 hours or more is feasible.

Until “clean coal” sees this type of enthusiastic global embrace, with dozens of projects around the world, at power prices comparable to other types of new power plants, it will always remain a (CO2) pipe dream.

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24 Responses to Solar baseload outshines ‘clean coal’ — and it always will

  1. vakibs says:


    For one thing, I agree with you that clean coal sucks. It is (a) a dumb idea, sequestered CO2 has a huge probability of leaking (b) horribly expensive, if it ever becomes feasible.

    About solar baseload power, three words “hi hi hi” :D

  2. Tomas Martin says:

    As an analyst in the solar sector (and researcher into 3rd generation concentration onto thermionics) I agree with you. Solar baseload is THE technology governments should be investing in, as well as the power infrastructure to hook them up to the grid (I think grid infrastructure and infrastructure in general has been overlooked and will be the next boom after renewables as people realise that even if you build the power, you still need to get it where it needs to be)

    There are some great high-tech solutions in the solar space that will contribute as prices fall in the next 10 years and beyond (we hope our device will be one of them). But in the near-term, CST is a relatively simple, price competitive technology that should be rolled out everywhere with suitable insolation.

  3. scott says:

    i would like to feature this article on my site, http://www.solarfeeds.com

  4. Joe says:

    Scott — Go for it!

  5. Rick C says:

    I’ve got six words for you when it comes to CCS and it is Lake Nyos Carbon Dioxide outgassing Disaster.


  6. Jim Bullis says:


    It is discouraging to see terminology being developed which creates confusion.

    “Solar baseload” as a label for a source or generator of electricity adds more gibberish to the language since it contradicts existing and well understood definitions in the English language. A “load” is something that is carried, not something that does the carrying.

    In the world of electrical power, “load” is a term that refers to the energy using part of the system.

    “Thermal solar” seems perfectly adequate.

    It was some time ago that you made a determined effort to use “CO2″ instead of “carbon” which was a constructive step. When people talk of “carbon” it is clear what they mean, most of the time. But if anyone is interested in quantitative thinking, this is a shorthand that creates a real ambiguity.

    But on to technology, the Sterling engines in these thermal solar devices seem to be something of an enigma. If they are so reliable and inexpensive, why have we not seen them in general use?

    [JR: "Thermal solar" is inadequate for obvious reasons. I have a "thermal solar" hot water heater on my house. Now if you were assuming everybody knew you meant "thermal solar POWER" well, that applies to solar baseload too. I, however, I'm not interested in an "adequate" term -- I am trying to do some branding here. Solar baseload power is not gibberish nor does it create confusion -- certainly not more confusion than thermal solar or even concentrated solar power, which is an incredibly confusing term since PV can be concentrated.]

  7. alex says:

    I agree that CSP (or whatever you call it) is perhaps the most promising technology. The UK and Eurpope could use power generated in the Sahara distributed bia HVDC lines.

    The only problem is a commercial / energy security one. Do we want to turn N Africa into our next Saudi Arabia? Much better if we can figure out how to use our abundant wind, wave and tidal resources.

  8. Jane says:

    Joe, what’s your take on the enclosed article? There was one reply that appeared to differ with this stance.

    From Solar Feeds
    Solar panels bad for global warming?
    Friday, 14 November 2008 13:06 Greenbang 4841 1 2 3 4 5 (1 vote, average: 5.00 out of 5)
    Just when you thought putting up solar panels was the right way to reduce your carbon footprint and curb climate change, along comes research that turns your good deed into cause for feeling guilt.

    The disturbing news arrives courtesy of a study by scientists at the Scripps Institution of Oceanography at the University of California in San Diego.

    The problem lies with NF3, or nitrogen trifluoride. You couldn’t find that gas in the atmosphere much just a few years ago, but now its concentrations are rising by 11 percent a year. Worst yet, it’s 17,000 times more powerful a greenhouse gas than carbon dioxide (and lasts five times longer).

    And where does nitrogen trifluoride come from? From the manufacture of flat-screen television sets, computer displays, microcircuitry and … thin-film photovoltaic cells.

    The Scripps researchers found that, in 2006, there was far more NF3 in the air — three and a half times as much — than originally believed. This year, they measured 5,400 metric tons of the stuff in the atmosphere, and the levels continue to go up.

    “I’d say case closed,” said Michael Prather, a University of California atmospheric chemist who was not involved with the study. “It is now shown to be an important greenhouse gas. Now we need to get hard numbers on how much is flowing through the system, from production to disposal.”

    Out with the solar panels, in with … draft animals for energy? No, wait: livestock are also a major source of greenhouse gases. Sigh. Human power, anybody?


    Jay Mucha said:
    Yes, NF3 could become a serious global warming gas. That’s why some 5-10 years ago the industry created abatement protocols from removing it, and other long-lived fluorocarbon effluets, from manufacturing sites. The gas is used for etching circuits and cleanind deposition reactors and i would suspect, hope, that solar manufacturers have adopted the practice. I personally favor ClF3 for such activities, but it is real nasty stuff if mishandled, but it is so reactive with water that it is easily scrubbed and has vertually zero atmospheric lifetime. If you really want to target a greenhouse manufacturing gas try C2F6. The semiconductor industry has targeted it too, but aluminum extraction and purifican create a lot more of it than all the NF3 and C2F6 comming from solar panel manufacturing.

  9. Michael Totten says:

    While csp/ste/”solar baseload ” is very exciting for the reasons you note, one concern is water requirements, especially given desert sitings, an more frequent and severe droughts. The last figures I saw indicated csp was one of the highest users of of water per MWh generated among thermal power plants. A column on innovations in this area would be valuable, i.e., economic feasibility of air-cooled systems.

    [JR: Air cooling is a must for mass deployment. It does add cost and reduce efficiency. I'll see if I can get a post on this.]

  10. David B. Benson says:

    Rick C — CCS plans are not at all similar to Lake Nylos overturning. In CCS, the CO2 forced into deep saline formaltions becomes chemically attracted to some of the minerals there; up to some maximum, it is permanently bound.

    Biomass-fired boilers wth CCS are attractive since these are carbon-negative, reducing (slightly for each one) the concentration of CO2 in the atmosphere.

  11. Rick C says:

    David B. Benson,

    Ok, then does the entire liquefied CO2 bind to the minerals or is some of it dissolved in the saline water? If it is dissolved into the water what happens if there is a seismic rift and the dissolved gas is allowed to escape to the surface?

  12. David B. Benson says:

    Rick C — I haven’t kept up with the details of what is planned, nor know the details of the one pilot project (in Germany). Anyway geologists and geochemists view CCS as long-term safe storage.

    Some of course remains disolved in the salt water, just as it does in the oceans. The concentrations there are low; I suspect the goal for CCS is a simplar low, safe figure.

  13. I put up this website as an educational site about solar thermal electric/CSP with storage:


    If someone who knows drupal can help me, it can be made more interactive and richer in content.

  14. Bob Wallace says:

    Any projections as to how much of our (US) electricity needs could be supplied by thermal solar?

    Thermal solar is climate limited, not likely to be utilized in the Northeast, for example. Nor are we likely to ship power from Arizona to Maine….

  15. Joe says:

    Bob — As much as we want.
    We have nuclear, hydro, and there’s no need to get rid of natural gas for a long time. So efficiency, baseload solar, wind, PV (and other renewables) can do the rest, in that order.

  16. David B. Benson says:

    Bob Wallace — It seems that modern HVDC loses as little as 3% per 1000 km, plus less than 1% conversion costs (that is for both ends).

    So you can work out the operating losses of sending Arizona power to Maine.

  17. Bob Wallace says:

    It’s closer from the Great Plains to the northeast corner than from Arizona/New Mexico. And based on what I know (or incorrectly “know”) wind is a less expensive way to produce electricity. That suggests to me that we’re more likely to see wind used for power in that part of the country.

    [JR: Not correct. Wind is variable and mostly nighttime. Where daytime or load following is needed, CSP will rule.]

    A HVDC transmission line from the SW to the NE might be roughly 2,500 km so perhaps it’s not inconceivable that we would choose to ship power up there.

    I suppose I was trying to get a handle on how large a role thermal solar is likely to play in our future energy mix.

    [JR: I expect to be the single biggest source of low-carbon electricity.]

    Hydro is pretty fixed. There’s not much more potential that we are likely to tap. And I think the probability of significant new nuclear quite low due to non-competitive costs.

    Natural gas does release some sequestered carbon. It would seem to be in our best interest (once we’ve replaced coal) to “park” our NG plants and use them only if renewables lag behind demand at times. Additionally it’s going to get more expensive to purchase fuel so there’s going to be financial pressure to quit using NG as/if solar and storage drop in price and other renewables come on line.

  18. Bob Wallace says:

    How about drill-down hot rock geothermal? Seems like folks are starting to figure this one out.

    To me, this holds the most promise for 24/365 power. Can be created closer to point of use, saving transmission costs.

    Prices are hard to call at this point, but speculation seems to put it in the same range as thermal solar.

    [JR: Needs $$$, but could be big. I blogged about it here.]

  19. Cyril R. says:

    Bob Wallace, the new Raser plant (opens in december) is about 10 MWe and costs 50 million. 5 dollars per Watt, but you get very high capacity factor, and the running costs are very low, so they have a contract for selling the power at about 8 cents per kWh.

    If hydrogen fraction drilling is commercialized, expect deep geothermal power to be substantially cheaper.

  20. Cyril R. says:

    About nomenclature. The correct term would be:

    Concentrating Solar Thermal Electricity with High Effective Load Carrying Capacity. CSTEHELCC.

    But that’s such a mouthful, and such a strange acronym. Just call it CST load following for sake of brevity.

  21. Jim Bullis says:

    Cyril, this is a big improvement over the “base load” stuff which I find incomprehensible. I think it is trying to drag along an assertion about how its output would be used that might or might not be true.

    As to “High Effective Load Carrying Capacity,” how about just “high output?”

  22. Bob Wallace

    “Any projections as to how much of our (US) electricity needs could be supplied by thermal solar?”

    Here are a few numbers

    A study by Western Governors Association
    said the industry could build 13 GW by 2015
    and that 300 GW could be built near existing transmission lines.
    The power cost would fall when there were 4 GW installed, to under 10cents/kWh from present 12-17cents/kWh and with economy of scale would fall to 5-8cents/kWh after that.

    There are already 2 GW contracted for or being built in California. Look at the list of U.S. projects and proposed plants at the link in Joe’s article here near top of the page.
    It shows 4,161 MW solar thermal and a little over 200 MW CPV proposed or approved in U.S. Most of it’s in California, but also Florida and Arizona.

    Ausra and others say an area 92 by 92 miles could power the whole country.
    About 1% of southwest desert lands. Less land than now used for coal plants and coal mining.

    Present coal capacity is 313 GW – just under a third of national capacity and supplying 50% of kWhs in U.S.

    The Solar Grand Plan proposal published by Scientific American is worth reading. I think maybe someone from First Solar was on this board, because of it’s emphasis on thin film cadmium teluride concentrating PV, rather than the CSP that makes more sense.
    But it is a pretty detailed plan to provide 69% of U.S. electricity with solar by 2050. And they show how it could be paid for.
    Interestingly the $400 billion in tax dollars they propose spending in subsidies over about 40 years is about how much we give the fossil fuel industry in subsidies about every
    eight years.

    Another interesting proposal is TREC -
    a plan to power Europe, the MidEast, and Northern Africa with electricity, combined heat and power(CHP), and water desalinization, all from solar thermal plants. It includes building an HVDC transmission system throughout the area.

  23. Solar baseload need not be a water hog like other thermal power plants, such as coal and nuclear. Water waste occurs when exhaust steam is cooled in surface condensers, which discharge the heat in the cooling water by evaporation in cooling towers. The amount of water waste is huge. And unfortunately for solar baseload, where you have lots of sun water is scarce.

    An organic Rankine cycle, using a working fluid having a high molecular weight and a low boiling point, could produce power from low temperature heat sources. Geothermal too. No cooling towers or other water waste in condensing the working fluid — ambient air cooling will do. Honeywell has developed an organic working fluid which may be right.

  24. Serious Black: The Quest for Clean Coal

    The search for ways to reduce carbon emissions has led to government grant money for schemes ranging from promising to wacky. Recognizing that there is no currently viable replacement for fossil fuels, with the possible exception of nuclear power, the US and other countries with large coal deposits are desperately looking for ways to continue burning coal without incurring the wrath of nature or the IPCC. Clear evidence of the seriousness of this effort is evident in this week’s special edition of Science, dedicated to carbon capture and sequestration (CCS) technology.