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Published on July 21st, 2013 | by Zachary Shahan

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Intermittency Of Renewables?… Not So Much



Below was a great summary (if a bit simplified in parts) comment from one of our readers on one of our posts last week. I thought it deserved a few more eyes. Also, I happened to go back to a roundtable discussion of utility CEOs today that supports the overall “the ‘intermittency’ of renewable energy issue is overhyped” argument. More on that below the reader comment.

Here’s the comment from Victor Provenzano (paragraph formatting and some links added):

To sum up the so-called “intermittency and storage” problem for renewables: Geothermal has no intermittency issues and experiences fewer ephemeral shut downs than coal, nuclear, and natural gas. Solar thermal — with molten salt as its storage medium — can be designed to have no intermittency issues. Offshore wind yields power more or less 24/7 with relatively limited intermittency compared with onshore wind. The two most common sources of renewable electricity, onshore wind and solar photovoltaics, are, of course, complementary: wind turbines (which, in the case of GE, already have built-in storage capacity) yield more power at night, while solar panels yield power during the day; hence, used in tandem, they can provide electricity 24/7 with “intermittency” being experienced only locally at each individual solar installation. The experience in Germany shows that the more wind and solar PV installations one has in the various regions of one’s country, the less the so-called intermittency problem is an issue because electricity is generated at varying wattages in the various locations more or less 24/7 and the actual total daily electric power levels become more and more stable and more and more foreseeable as the number of installations increases nationwide. At that point, the intermittency deficit is more easily and more predictably counterbalanced with reserve power (natural gas and hydro), storage (pumped hydro, compressed air, flywheels, grid storage batteries), and grid power from neighboring nations.

The European experience shows that the “intermittency” issue is being widely and very inaccurately exaggerated by America’s energy specialists. What is more, if one has a mix of renewable energy sources online that includes the non-intermittent forms of renewable energy (hydro, geothermal, and solar thermal with molten salt), the far less intermittent sources (offshore wind), and the complementary locally “intermittent” sources (solar PV and onshore wind with its own built-in storage capacity), then the limited remaining “intermittency problem” can be far more easily overcome.

Well summarized.

In a utility company CEO roundtable at Solar Power International 2011 (video here), the General Manager of Austin Energy through up the same sort of anti-solar lob that the commenter above was addressing. What was great to see was that a couple of other utility company CEOs stood up very strongly to the (intentional or unintentional) propaganda and explained why integrating renewable energy into the grid was not an issue. (To watch the responses quoted below, jump to 1:25:29 in the video.)

solar power international utility ceo roundtable



First, the then CEO and President of Florida Power & Light, Armando Olivera, chimed in. “I spent a lot of time in operations in our company. Of all the things that I worry about, regulating using solar, or renewables, really doesn’t worry me. I think you gotta be at a really huge scale of solar before that becomes an issue. And in the meantime, we’ve got a lot of enabling technology going into these grids… about half of the meters at FPL are already automated devices. We are learning a huge… we’re seeing benefits that we didn’t fully anticipate in terms of managing the grid. We’re also putting in a lot of smart technology that can adjust at a very local level whenever there’s a problem. So, you know, I think there’s a huge foundation that’s being laid out today that will facilitate all of these technologies….”

Doyle Beneby, President & CEO of CPS Energy, backed him up. ”Yeah, I would agree with Armando, I don’t worry about that at all…. Generally, if you’ve got automated meters, if you’ve got the means for a home area network, I think you can easily reduce demand to follow — I call it load-following — for solar. What we found, also, is that there are a very discreet set of customers out there who would volunteer to have their load reduced to follow the drop in output for solar…. So I think that’s a big opportunity out (there) for us. I really think concerns about the grid, so to speak, and even to a degree intermittency, should not at all impede the progress of solar.”

Robert Powers, President of AEP Utilities, also chimed in and said, “I agree with my colleague that near-term there’s no, no issue with grid stability with deploying solar.”

I thought that was all a great, serendipitous addendum to this reader comment. And I’m happy that after about two years I got around to transcribing that. I also transcribed much more back around the time of the conference and roundtable.

By the way, just following that discussion was some more fun discussion around the benefits of solar in protecting against cyber attacks, something two CEOs noted the military was well aware of that and already using solar and microgrids for security reasons. To watch to that section, jump to 1:27:53. And, if you want even more, a very interesting section on what these utility company CEOs and Presidents would wish for if they had one wish that could really help them ramp up solar started at 1:31:05. Or just watch the whole thing….

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About the Author

is the director of CleanTechnica, the most popular cleantech-focused website in the world, and Planetsave, a world-leading green and science news site. He has been covering green news of various sorts since 2008, and he has been especially focused on solar energy, electric vehicles, and wind energy for the past four years or so. Aside from his work on CleanTechnica and Planetsave, he's the Network Manager for their parent organization – Important Media – and he's the Owner/Founder of Solar Love, EV Obsession, and Bikocity. To connect with Zach on some of your favorite social networks, go to ZacharyShahan.com and click on the relevant buttons.



  • Christian Abel

    Sorry, bozo, on this page we see the erratic output of wind.
    LOL

  • karl burkart

    This has been proven in computer simulations by the team at Stanford led by Mark Jocobsen, provided the different intermittencies balance each other out. Moreover, the more renewables on grid the greater grid efficiency – http://news.stanford.edu/news/2013/march/new-york-energy-031213.html

    • Bob_Wallace

      Mark Z. rules.

      (It’s Jacobson)

    • http://zacharyshahan.com/ Zachary Shahan

      Thanks, Karl!

  • http://neilblanchard.blogspot.com/ Neil Blanchard

    A couple of important renewable energy sources that were not mentioned (I think?) in the article:

    Wave power is quite constant if well sited, and only really varies in amplitude. There are at least three companies around the world that already build working systems. There are two types: buoys with tall columns underwater that have suspended magnets (think giant shake flashlights!) and an array of ~66-70 buoys can produce 10MW. The other type is a floating series of horizontal tubes, that are hinged together – hydraulic pumps at the hinges build pressure in accumulators, and then this is used in hydraulic motors to spin generators. Each 500′ long (5 sections of 100′ each) produces ~0.75MW.

    Tidal power is very consistent and predictable; though obviously cyclical. Underwater turbines make a lot of power because of the immense torque provided by the flowing water. Again, there are several companies already making these.

    Methane gas can be made from sewage, and from farm waste (plant and animal) and this can be stored, and used in gas turbine peaker plants. After the methane is made, the resulting material makes a high quality fixed nitrogen fertilizer – which can replace synthetic fertilizer now made from natural gas. This avoids another very large source of greenhouse gas!

    Neil

  • heinbloed

    ” Intermittent electricity ” covered more than 60% in Germany yesterday around noon.

    http://www.agora-energiewende.de/service/aktuelle-stromdaten/stromerzeugung-und-verbrauch/

    No fuse blew, no transformer caught fire and no cable melted.

    At night time only around 20% ” intermittent electricity ” was available to cover German demand. And no fuse blew,no transformer cought fire and no cable froze-up.

    Btw.: ” intermittent ” is all AC electricity.

    • anti_banker

      Only problem is that the site you linked to is all written in German ;-)

      • Bob_Wallace

        Google translate whips it into shape.

        • anti_banker

          yeah, except Google translate didn’t seems to popup when the page loaded (as it normally does).

  • Ervin Gazy

    On PJM’s webpage it states that their is 19,000 MW of quedued wind power on
    there system, I guess if there was 50,000 MW on the system there might have
    been more than .00033% contrbution from wind power

    • Bob_Wallace

      Funny.

      It’s right there in the article at the top of the page and you either refuse to read the article or can’t understand it.

      Oh, well….

      • RobS

        I fell bad that he went to the effort of creating a profile with a picture and those 2 rambling irrelevant contributions were the best he could come up with, I certainly wouldn’t want people to be able to recognise me if that was the most intelligent comment I could make.

        • Bob_Wallace

          It’s rather amazing that some people seem to think that people who work in renewable energy have never noticed that the wind doesn’t blow all the time and that the Sun goes down at night.

          And they seem to not know that coal and nuclear plants break from time to time. Even when it’s in the news with some regularity.

          Go figure….

          • RobS

            Agree particularly the point about ff plants. People love to point out how wind and solar need spinning reserves, they don’t seem to realise that grid management rules say that the grid must be able to remain stable in the event of the failure of the largest plant on the grid, that means that gargantuan coal plants also require spinning reserve in case they trip. The ability to be able to cover an unexpected supply drop is not in any way confined to renewables.

          • Bob_Wallace

            How about a couple of years back when an earthquake took two reactors off line in Virginia?

            That’s a hole that isn’t easily filled, especially when it was totally unexpected. Earthquakes in Virginia?

          • Christian Abel

            It isn’t that they haven’t noticed, it’s that they expect the population to be so fucking retarded – which is usually the case.

            “And they seem to not know that coal and nuclear plants break from time to time”

            You are so fucking retarded.

          • Bob_Wallace

            You can clean up your act or get tossed.

            Your call.

          • Guest

            Fascist pig.

          • Christian Abel

            It isn’t that they haven’t noticed, it’s that they expect the population to be that retarded – which is usually the case.

    • http://zacharyshahan.com/ Zachary Shahan

      Already, “wind provides about 1.5 percent of the electricity to PJM’s customers” http://thinkprogress.org/climate/2013/05/09/1988391/more-wind-in-pjms-sails-could-save-consumers-69-billion-per-year/

  • Ronald Brakels

    Here in Australia we have a radical method of ensuring a reliable electricity supply. We pay people to provide us with electricity when we want it. It turns out that people are willing to supply electricity as long as we’re willing to pay for it. (Who would have thunk it?) I understand that one or two other countries also use this method. Oddly enough though, there seem to be plenty of Americans on the internet who appear to doubt the ability of markets to supply goods in this manner. Maybe it’s a cultural thing and Americans just aren’t into market economies?

  • jburt56

    As the years go by and the data keep getting written up the skeptics will have to concede. That first terawatt is the hardest!!

  • Robert Means

    I generally agree with the posting, but it is necessary to distinguish between two problems of intermittent renewable generation. One has a relatively short time frame. The task is to maintain a stable voltage and frequency and to avoid unpredictable changes in output. (From the standpoint of running an electricity system, it’s OK for wind output to drop; it’s not OK for it to drop substantially with only a few minutes’ notice.) As the posting notes, this problem can be greatly reduced by geographical and technology diversification, and in the future the remaining problem probably can be dealt with by storage. (GE touts this as being one of the functions of their new wind turbines with integrated storage.)

    The second problem is to deal with the longer periods of time (like windless August nights) when there is neither wind nor sun. (GE explicitly states that its new turbines are not directed at this problem.) Two relatively recent studies deal with this second problem. One is by NREL (www.nrel.gov/analysis/re_futures) and assesses how U.S. could supply 80% of its electricity with renewables by 2050. The other is by the California Council on Science and Technology (ccst.us/publications/2011/2011energy.php) and assesses how California could reduce its own emissions to 20% of the 1990 level by 2050 — a goal set in a Schwarzenegger executive order. The NREL study concludes that its posited goal, but only with VERY large investments in transmission and dispatchable renewables (geothermal, etc.)

    • Bob_Wallace

      You might want to read the Budischak et al. 2013 paper that uses four
      years of demand data along with wind and solar data to see how well a
      real world grid would work with nothing but wind, solar, storage and a
      tiny bit (~0.1%) of dispatchable gas. A 99.9% wind and solar grid.

      They used data for 1999 through 2002 from the PJM Interconnection, a
      large regional grid that services all or part of 13 states from New
      Jersey west to Illinois, from Pennsylvania south into Tennessee and
      North Carolina. This is the world’s largest competitive wholesale
      electricity market, serving 60 million customers, and it represents
      one-fifth of the United States’ total electric grid.

      And they used 35 hours of gas generation across four years.

      ttps://docs.google.com/file/d/1NrBZJejkUTRYJv5YE__kBFuecdDL2pDTvKLyBjfCPr_8yR7eCTDhLGm8oEPo/edit

      • Robert Means

        Thanks for the reference.

      • http://zacharyshahan.com/ Zachary Shahan

        the link is missing. seems like it’s because the first letter is missing. will try to fix.

      • Keith Pickering

        Yeah, Budischak points out that you only have to overbuild wind by a factor of three to make wind reliable enough to reach a point that gives us three times worse than the current 99.97% reliability.

        At which point, the consumer cost triples, as Budischak also shows. And getting that last .07%? Forget about it. Nobody wants to go there.

        • Bob_Wallace

          Had you read with comprehension then you would understand that they purposely left out hydro, geothermal, load-shifting, biomass, residual nuclear, and power trading with other grids.

          Add those in and the need to overbuild drops significantly.

          Furthermore they used 2030 costs which are already out of date. Wind costs are below what they used and solar is far below.

          As well, it’s fairly likely we’ll have cheaper storage than what they used to produce their numbers.

          The last “.07%”? You mean the last 0.01%?

          If we could get fossil fuel use down that low there would be dancing in the streets.

          • A. Antoine

            Why would they leave out the more useful stuff?

          • Bob_Wallace

            As they say in the first sentence of the introduction -

            “What would the electric system look like if based primarily on renewable energy sources whose output varies with weather and sunlight?”

            The paper is a ‘worst case, could it be done?’ study. If all we had was wind and sunshine could we build a reliable and affordable grid?

            The answer is “yes”, but it’s not the cheapest of all grids. Adding in other renewables, using load-shifting, and exchanging power with adjacent grids would make it cheaper.

            Most people would agree that we could build a grid on hydro and geothermal if we had enough of it. But people frequently claim that it would be impossible to run a real grid on only wind and solar. This study shows it quite possible.

      • Christian Abel

        Obviously anything can work with “storage”.
        The issue is how much storage you need.

        • Bob_Wallace

          Correct. The chore ahead will be to balance generation, storage and load-shifting as well as becoming as efficient as reasonable.

          That’s exactly what the Budischak paper deals with. It builds a ‘best solution’ model based on the technology available when the paper was written. Since it was written technology has improved some and costs have dropped quite a bit which would change the ‘best mix’.

          Post publication the cost of solar dropped significantly. That likely means that a current best cost model would over build solar more than when the publication model was run. And that’s what we will do as things progress. Cheaper storage could cause the mix to be readjusted, for example.

          We’ve got to get off fossil fuels and we will not have unlimited funds to make the transition.

    • Bob_Wallace

      ” only with VERY large investments in transmission and dispatchable renewables (geothermal, etc.)”

      Which bill do you suspect would be lower, transitioning our grids to renewables or dealing with extreme climate change?

      You know, rebuilding our coastal cities on higher ground, abandoning much of our most productive agricultural land, relocating large parts of the population to where they can obtain fresh water, writing off the bottom half of Florida, ….

      • Christian Abel

        Well, nuclear is cheaper. Way, way cheaper.

        • Bob_Wallace

          That’s something one here’s from people who haven’t kept up with what has happened in the energy world in the last decade.

          They are, of course, badly wrong.

          • Christian Abel

            And France once again shows that the deniers are wrong.

  • Ervin Gazy

    July 18, 2013 PJM’s 2pm load 150,000 MW contrbution from wind 50 MW

    • Bob_Wallace

      Why do people embarrass themselves by posting stuff like this?

      Do they not even bother to read the article before they post?

      • http://soltesza.wordpress.com/ sola

        If they could actually read (and think about what they have just read), they wouldn’t spew so much nonsense.

  • Matt

    Oh dang, I’ve become as conservative as the CEO of a power company. Been a broken record for years, we need a price on carbon and a energy policy that is written by the fossil fuel suppliers.

    • http://zacharyshahan.com/ Zachary Shahan

      haha :D

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