Clean Power cost of solar CSP SunShot

Published on May 20th, 2016 | by Tina Casey

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DOE Recaps Solar Success Story, CSP Makes The Cut

May 20th, 2016 by  

The US Department of Energy has just cast a super-critical eye over its SunShot solar energy initiative in a suite of eight newly published reports, including one that zeroes in on the controversial field of concentrating solar power. The complexity and expense of concentrating technology has been attracting a giant stinkeye from some industry observers, but according to the Energy Department, reports of its death are premature.

In fact, the way the Energy Department sees it, CSP will play a vital role in the ability of solar energy to penetrate more deeply into the mainstream grid mix. cost of solar CSP SunShot

What’s Up With Concentrating Solar?

For those of you new to the topic, concentrating solar power (CSP) refers to systems that collect solar energy in a wide field and focus it on a narrower field. A typical CSP system will use that focused energy to heat a liquid, which is then deployed to run a steam-powered electricity generator.

Not too long ago, CSP looked like a competitive alternative to photovoltaic (PV) systems, aka solar cells, which generate electricity directly from sunlight.

More recently, though, the cost of PV technology has been rocketing down (and it hasn’t hit bottom yet). CSP costs have also been falling, but not quite as fast.

Another stumbling block to market penetration is scale. PV systems easily scale down to just a few kilowatts, but the size and complexity of CSP requires megawatt-scale installations.

Solar And The Energy Storage Factor

CSP does have one strong advantage highlighted by the Energy Department, and that is its built-in penchant for storing large amounts of solar energy in the form of heated molten salt.

Last fall CleanTechnica interviewed Fred Redell, Managing Director of the global CSP leader Abengoa, who made the case that CSP with energy storage has the potential to “revolutionize” the solar field.

That may have been a little premature in terms of today’s marketplace — the company has been restructuring this year — but the Energy Department still has its eye on the big picture.

Last fall, the agency awarded $32 million in new funding for its CSP: APOLLO initiative, aimed at next-generation improvements in concentrating solar technology, with the aim of bringing costs down.

The new funding, some of which went to Abengoa, builds on the success of a previous CSP R&D initiative.

The chart below gives you an idea of the size and scope of that initial commitment:

cost of solar CSP

A Bright Future For CSP In The USA

The new concentrating solar power report outlines the significant drop in the cost of CSP…

LCOE solar energy CSP

…and it describes the major technology improvements that have brought about the decline.

The Energy Department measures success against the SunShot goal of getting the cost of CSP down to 6 cents per kilowatt hour by 2020. According to the new report, CSP technology is “well on the path” to achieving that goal, one major factor being a decline in the cost of heliostats (those are the special mirrors used to focus solar energy on a collection point).

Unfortunately for CSP fans, the cost of PV is dropping faster, and the new report notes that “…CSP systems are more complex to develop, design, construct, and operate.” In addition, according to the Energy Department, in order to be effective, CSP systems need to be at least 50 megawatts, which greatly limits site selection.

Here’s the money quote, though:

However, the ability of CSP to use thermal energy storage—and thus provide continuous power for long periods when the sun is not shining—could give CSP a vital role in evolving electricity systems.

If you want all the details, the new CSP report is available as a free download. For those of you on the go, the gist of the argument is that if you want to have more variable energy — namely, wind and solar — in your grid, then you’ve got to have more energy storage.

The key point is whether or not CSP storage gets you closer to your grid goals than the alternative, which would be more PV with storage. The Energy Department refers to a recent report by the National Renewable Energy Laboratory on exactly that topic. That report examined the benefits of operational flexibility and capacity for both CSP and PV systems with storage, assuming a grid goal of 40 percent renewable energy. The report concluded:

The analysis found that the value of CSP, compared to variable-generation PV, demonstrated an increase in value of up to 6 cents/kWh under a 40% RPS.

The Energy Department’s basic case is that you can’t measure value to the grid just by calculating the cost of a solar system. You also need to factor in storage value, and by that metric, CSP systems can provide for a higher degree of grid flexibility.

What If…

The report takes it a step further by arguing that CSP has yet to realize its full strength in grid operations, due to competition from low cost natural gas. Under a scenario of low natural gas prices, the role of CSP systems is largely confined to “peaking” operations (peaking plants are constructed to provide additional power to handle peak load periods).

If the cost of natural gas rises, the options for CSP deployment are more broad. That’s especially true if lifecycle carbon emissions — and their costs — are factored in:

In that case, each of the CSP configurations compares very favorably against the conventional alternatives, with systems having intermediate to high capacity factor becoming the preferred alternatives. (Capacity factor is defined as the ratio of actual annual generation to the amount of generation had the plant operated at its nameplate capacity for the entire year.)

The Energy Department also notes that CSP’s affinity with thermal energy storage provides it with a potential lifecycle cost advantage, due to open questions about the cost and longevity of battery-type systems associated with PV.

The bottom line: despite the doubters, the Energy Department is fully committed to advancing CSP technology.

The CSP report is just one of eight new reports on the past, present, and future state of the US solar energy field, so stay tuned for more.

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Images: via US Department of Energy.





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About the Author

specializes in military and corporate sustainability, advanced technology, emerging materials, biofuels, and water and wastewater issues. Tina’s articles are reposted frequently on Reuters, Scientific American, and many other sites. Views expressed are her own. Follow her on Twitter @TinaMCasey and Google+.



  • super390

    It would have been great if there was a way to combine low-cost photovoltaic cells with a heat-storage system. Maybe troughs to concentrate light on a single coolant-filled tube coated with PV.

  • Matt

    Another example of where leveling the energy market by pricing carbon externals would greatly speed implementation. If they were build 10/year instead of 1 the learning curve would bring the cost down much faster.

  • TinaCasey

    Thank you all for a lively discussion. As you collectively point out, there is still a lot of untapped potential in CSP. Here’s the link for that APOLLO program, which has more details about DOE’s areas of focus http://energy.gov/eere/sunshot/concentrating-solar-power-advanced-projects-offering-low-lcoe-opportunities-csp-apollo

  • Bob_Wallace

    If they can hit 6c/kWh I think they have a winner. Even if solar reaches 2c/kWh it’s going to be hard to get storage down to 4c. Plus the CSP plants should be able to run on gas if their stored heat runs out. That makes them potential ‘deep backup’ for the rare times when both wind and solar go way low for a few days.

  • JamesWimberley

    Skimming the report, I ran across a old friend in the way of miracle materials:

    “The use of perovskites as sand-like particles is being studied as part of theU.S. Department of Energy’s … ELEMENTS program. These particles may be a means to collect, store, and transfer heat for high-temperature applications using reduction/oxidation reactions.”

    The DoE is also looking at the Real Men version of CSP, the direct Brayton cycle (aka gas turbine) using either CO2 in a closed loop (700 deg C) or just hot air at 1200 deg C. The latter is reasonably described as “challenging”, i.e. mad, especially as they want to have storage too.

  • GCO

    The best part is, it’s not CSP or PV, it’s both, combined. If PV is more economical during the day, great, let’s use that first while CSP stores away; it will take over as the sun sets.

    I trust that this is exactly the idea behind hybrid plants like Atacama-1 in Chile and Noor in Morocco.

    • Frank

      Oh for sure. The competition for CSP is pv + storage, or maybe gas. The one is for cheap bulk power, the other for control.

  • eveee

    DOE is right. The cost is only part of the equation. Payback matters, too. CSP can deliver power not just during the day, but at night, and critically, into the ducks head, where wholesale power rates are higher.
    That gives it the opportunity of higher payback. Places like California, Nevada, Arizona, and other southern states will see first benefit from storage as PV solar reaches higher concentrations. The combination is a one two punch that delivers energy at low cost across the whole demand curve.

  • J.H.

    Good write up. Just wish the article exposed the difference in cost with reference to Tower vs trough designs. Trough design appears to be a much simpler system which may lower cost and is less likely to damage to bird population.

    • nitpicker357

      My understanding is that the bird problem is largely solved; don’t focus the mirrors on a point unless that point is the tower. Which leaves cost as the critical variable. The included chart shows tower being cheaper. It also seems like the degree of concentration is higher for tower, which is good for storage.

      • J.H.

        I see the chart now, its hard to ague with the data, and yes I would agree on the concentration is higher. But its is hard for me to see the over all cost is cheaper.

        • nitpicker357

          Parabolic trough implies parabolic mirrors. More expensive. The receiver is a long tube, which loses more energy. The tower needs pointing systems, but computers are approximately free. I could believe it either way, but they say tower is cheaper.

          • J.H.

            Implies parabolic mirrors”. There is a few options available as opposed to the use of a mirror. 3M has a film, stainless steel, ect. Losses can be managed, but I do agree that towers provide more gain and higher Temps, more suitable for utility scale. On a community scale, tough design is functional for delivering heat to the community.

      • nitpicker357

        I would have thought this went without saying, but apparently not: don’t focus the mirrors on any single point but the collector. Apparently there are bad places on the tower to focus the mirrors on. Oops.

        • Bob_Wallace

          Make sure no more than four reflected beams converge at the same point in the air above the tower.

          It took less than a day to reprogram the computer to “park” the mirrors so that they didn’t create hot spots.

          And the number of bird kills claimed were extremely overblown. Someone noticed things getting burned and falling. They called them ‘streamers’. And they estimated one every couple of minutes or something like that.
          Someone else (someone who seems to be on an anti-renewable energy campaign) decided that a casual “every couple of minutes was 30 per hour. And that every streamer was a bird. Actually most streamers seem to have been insects and bits of trash being blown around by the wind.

          It’s Al Gore inventing the internet, all over again.

          • Sailingsoul

            If a bird flies close enough to the reciever they are instantly fried. Any first grader get’s that, why cant you? There is a death zone no matter how you focus, think about it if that’s possible.

          • nitpicker357

            It can’t be instantaneous, any first grader knows that. It’s “receiver”, not “reciever”. I would expect birds to veer away from the very bright, hot spots. Living things are funny that way.
            Cats are estimated to kill between 1.4 and 3.7 billion birds a year.
            Bored with it. Show me that there is a problem.

          • Sailingsoul

            “Cats are estimated to kill between 1.4 and 3.7 billion birds a year.” What does mentioning that brings to the conversation and how it’s relevant? Care to bring up all the millions of birds called chickens that are killed each year too? If that is what your going to argue, you obviously have no argument.

          • Bob_Wallace

            It’s relevant in that is shows that bird kills at a thermal solar plant is a tiny, tiny percentage of bird kills overall. But perhaps your interest is not in what kills birds but what electricity generation technology kills the most birds.

            Now we don’t have current kill data for Ivanpah. But we do have some data to contemplate.

            Based on bird kills per gigawatt hour of electricity produced.

            Wind farms kill roughly 0.27 birds per GWh.

            Nuclear plants kill about 0.6 birds per GWh. (2.2x wind)

            Fossil-fueled power stations kill about 9.4 birds per GWh. (34.8x wind)

            http://papers.ssrn.com/sol3/papers.cfm?abstract_id=2198024

            Seems like before the grape juice bird kills at Ivanpah were under 1,000 per year which would make kills less than 1 per GWh. Not as good as wind but certainly a lot better than coal.

            Susan should be bringing us some thermal solar data.

          • Sailingsoul

            Your last reply was much more effective raising issues you feel are relevant. I would not choose your first approach over the latter going forward. The latter was a more effective reply. cheers

          • Bob_Wallace

            My first approach? In which I explained that the high bird kill numbers for Ivanpah were incorrect and why they were?

      • Sailingsoul

        Are you serious? For flying birds your simply dead wrong! There still is a high temp’ dead zone all around the receiver that birds are killed by simply flying into, no matter how you focus the heliostats. That cannot be elinimated, period.

        • That danger can be eliminated. After testing various options, Ivanpah now uses a grape juice aerosol that deters birds from going that close to the receiver.

          There are lots of industrial precedents for bird deterrent technologies; it used to be that massive numbers of seagulls were killed at airports for example, now they are kept away with bird deterrents.

          • Bob_Wallace

            “a grape juice aerosol ”

            Would you expand on that please?

            How is it delivered? Is there a chance that it will foul the receiver or mirrors?

            How the hell did they hit on grape juice?

          • No, this is sprayed close to the receiver at the top of the tower – the closest mirrors are like 300 ft away or even more. IIRC ( a year since I spoke to BrightSource) it is sprayed when radar detects birds heading towards the tower.

            How indeed did the solution turn out to be grape juice? Bizarre, but apparently an already widely used bird deterrent.

          • Bob_Wallace

            Perhaps it’s time for a bird update. The myth that birds are crashing into the receiver and being toasted seems to be on the rise. It would be good to get some facts out front.

            Are the bird kill studies continuing? Data?

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