Newly Released Data Indicates Ivanpah Gas is Under 5%

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The use of gas for generation at the world’s largest direct steam solar tower has never exceeded 5 percent, according to newly released data from NRG and confirmed by EIA and the California Energy Commission (CEC).

Ivanpah- 2015 Total MWh Generated from Solar Versus Natural Gas
Data Source: EIA, NRG

At the 377 MW Ivanpah CSP project, the use of natural gas is limited to 5 percent of generation, despite media reports that imply otherwise.

In one example, David Lamfrom, desert project manager of the National Parks Conservation Association, is quoted by the Press Enterprise as saying that he doubted that the project would have gone forward if it had been billed a hybrid plant: that “if it had been billed as a 75 percent renewable energy project, the BLM might have said ‘no.’”

This suggests to the reader that Ivanpah is only 75% renewable, and gets a quarter of its generation from gas. That is factually incorrect.

Adam Ward, spokesman for the CEC, confirmed that Ivanpah generates 5 percent or less of its megawatt hours from natural gas.

(Ivanpah must remain at least 95 percent renewable because it must meet the Renewable Portfolio Standard (RPS) guidelines under which it was certified.)

I asked NRG spokesman David Knox why the data on generation from natural gas didn’t show up at EIA in 2014. He told me that the plant was not able to report generation from natural gas until 2015, as the CEC had not yet decided on the methodology for calculating it.

Knox forwarded me NRG’s spreadsheet including newly released figures for January to August 2015 (indicated in red) which are not yet included on the EIA site, where you can check the monthly generation for Ivanpah Unit 1, Unit 2 and Unit 3.

EIA spokesman Jonathan Cogan told me that EIA has had delays getting the first months of data online, but expects to have it up later in the year. “When we finalize the 2015 data files, that will be incorporated into the browser,” he said.

Documents provided to me by NRG reveal new details about how many megawatt hours of generation came from natural gas in 2015.

Ivanpah 2015 Total MWh of Solar v Natural Gas

Source: EIA and NRG

How the CEC decided on a method for counting natural gas generation in 2015

It turns out that it took quite a few meetings with the CEC to find a methodology on how to accurately determine how much gas contributed to power generated, after the project increased its use of natural gas in September of 2014 to 5 percent. Some of that now went towards generation, but how to know how much?

Knox said it was not that straightforward to determine how many megawatthours were generated by gas or by solar. Steam generated by the natural gas boiler mixes with the steam from the solar boiler at an intermediate stage in the steam turbine steam path – so it was hard to separate electric generation from natural gas alone.

Once the method of calculating how much gas was contributing to generation was worked out with the CEC, Ivanpah was able to report the generation from natural gas and from solar. When the generator breaker is closed, any gas that is consumed on-site is deemed to contribute towards electricity generation.

“So we meter the amount of gas consumed while the generator breaker is closed and use an agreed upon conversion factor to convert the energy from gas combustion into net MWh of electrical output,” explained Knox.

Ivanpah project


The Ivanpah concentrated solar tower project is the first-of-its-kind direct steam plant at utility-scale; 377 MW. Thousands of huge mirrors reflect sunlight onto a receiver where water is turned to steam by the heat of the focused sunlight.

Ivanpah has a PPA (Power Purchase Agreement) with PG&E for two of the three tower units comprising the plant, units 1 and 3.

In 2014, Ivanpah operators had asked the CEC to be permitted to raise gas use from a low initially planned 2 percent for parasitic overnight use to 5 percent.

The additional use was approved, and some generation was permitted from gas as a result of that, with the first morning steam created by burning gas, and during cloudy periods.

Ivanpah’s initial bad start caused the project to fall short of the 70% required output for the first two year look-back period, during a four year ramp-up to full generation.

In the first two-year look-back period, Ivanpah units 1 and 3 were generating on average 19% short of the contracted percentage. But by the second year, generation was only 3% below target and still improving.

PG&E asked the CPUC to let Ivanpah keep its PPA, as poor initial performance is fairly routine with new technology during a ramp-up period, and this 377 MW direct steam solar tower technology was without precedent when it began, other than small projects at 11 MW.

Current generation in the first quarter of 2016 has actually been above mature year requirements (the 100% level due in 2018) of 640,000 MWh for these two units.

Gas for keeping warm overnight helped speed morning start-up

A major cause of the very slow morning startups in early 2014 – just how cold the turbine gets by morning –  had some very low tech solutions.

“The initial thinking of how warm the steam turbine would remain overnight was off quite a bit,” said Mitchell Samulelian, NRG’s vice president of operation for utility-scale renewable generation.

“A typical power plant steam turbine takes anywhere from four to 24 hours of warming to get hot enough to start up. But obviously if you take 24 hours to warm a solar plant, you are never going to make any money!”

The solution to that overnight cooling was to increase the ceiling steam heat – using gas, as well as to insulate the turbine. That has successfully kept the turbine at well above 750 Fahrenheit at night so that it wouldn’t cool off.

By keeping warm overnight, Ivanpah can now start up very quickly in the morning; going from 4 hours to under 25 minutes.

In a gas or coal power plant, this use of gas overnight for what is called “parasitic load” – providing energy needs onsite that is not for sale to the grid – is fairly routine.

“If a coal plant the size of Ivanpah at 400 MW is shut down overnight, and needed to run in the morning, this would also consume natural gas, because they would be using natural gas to make steam seals for the turbine in order to draw a vacuum and start up,” said Samuelian.

“So a lot of our fossil fuel plants have an auxiliary boiler that is for supplemental heating when the plant is off-line, no different than Ivanpah.”

The additional gas use (up to 5 percent of generated electricity) was approved for parasitic overnight use, and to create that first morning steam to speed morning start-up times, and during cloudy periods.

To stay under 5 percent the gas is closed off if necessary 

“We can regulate how much gas we use,” Samuelian pointed out. “We can make a choice to actually not add any natural gas to stay online, if it’s a very cloudy day – versus just coming offline – if we think we’re getting close to our limit.”

And in 2016, gas has not even been as high as 5 percent.

“In these latest three to four months our gas use is in the 3 percent to 4 percent range,” said Samuelian.

Susan Kraemer is currently researching the transition to renewable energy for an upcoming book:

How We Learned to Run a Civilization on Infinite Energy:
Chronicling the engineering challenges overcome in launching a renewable energy economy, based on first hand accounts

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46 thoughts on “Newly Released Data Indicates Ivanpah Gas is Under 5%

  • The irony is that a different renewable energy technology is ruining the economics of this renewable energy technology.

    You know renewables have won when a one is replacing another.

    Literally in the time it took to build that power plant, solar PV went from way more expensive to way cheaper. #21stCenturySpeed

    • Yeah someone in the comment section on GTM said that electrons from solar PV are cheaper than electrons from solar thermal.

      The only thing is with molten salt, maybe the overnight supply of electrons is cheaper from a CSP station compared to solar PV + batteries.

      • It’s so unfortunate that Ivanpah was one of the first big solar thermal projects in the US because its technology is already dated. Crescent Dunes, just upstate, is proving remarkably successful from the start.
        Thermal storage is the answer and can provide 24/7 solar power. Perhaps Ivanpah can retrofit storage…

        • No, for several reasons. Steam is not that great of a storage medium. Molten salt can stay ready in the storage tank essentially for months. But “bolting on” a molten salt system with a storage tank, to a direct steam tower CSP like Ivanpah is simply too expensive if you are not already running molten salt through the tower first like SolarReserve does.

          Abengoa’s direct steam Khi Solar One (only 50 MW) will store for only two hours. So that’s only 100 MWh a day; not much. (Crescent Dunes is 1,100 MWh a day)

          Unfortunately, it it’s hard to get technical info from Abengoa. But this ARPA-E winner doing storage R&D once told me:

          …. that storage with direct steam doesn’t work well, and that’s why only such a modest few MWh as that is all you can get if you run and store in steam.

      • This may be the role for thermal solar, holding back it’s generation for the house when Sun and wind are not supplying demand.

        I wonder. They’re using NG to heat a boiler. Would it make sense to first pass the gas through a turbine? Might the amount of energy be increased? More electricity during the 25 minute warmup.

        It’s possible that the extra electricity produced would never pay for the turbine but I’m thinking a longer game. Those hours a year when the grid is really strapped for electricity, the turbine might be useful to increase total generation out of the plant. If the plant was generating too much power for the transmission line then send some heat to storage and use it in the evening. The turbine could bite into both the duck’s head and butt….

        • A steam turbine will have significant design differences when compared to gas turbine. Those design differences are due to the different gas and water thermal properties and the different densities. Burning natural gas inside a steam turbine would not produce power

          • Combined cycle gas plants consist of a gas turbine and a steam turbine. The waste heat from the gas turbine provides the heat to run the steam turbine.

            I was wondering if it would make sense to use the waste heat to warm up the solar thermal water to the flash point. Would running a CCNG as the early morning heater be a more efficient fuel use?

            Why can’t the water from a steam operation like Ivanpah be stored at just below the boiling point? Rather than losing all that heat, lose just enough to condense the steam. Drain it off into a “thermos bottle”.

  • Susan – Thanks for setting the record straight. I like the way you do your research and quash loose rumors.

      • Yep. That about sums up my feelings. Let the cards fall where they may. But don’t tip the scales one way or the other. And I will try like crazy to get it right and keep it there.

        • There’s plenty getting it wrong. Either by the “loyal opposition” pooh-poohing whatever weak link can be found (like one Tesla owner with a problem) because they have a whole traditional energy industry to protect — or alternatively by a tendency by enthusiasts to cover clean tech as if it is some kind of instant magic that need not bother with the laws of physics.

          • You have a full time job. 🙂

  • This data is not going to quiet the critics. This data is determined by natural gas use when the turbine i generating power. The critics didn’t have that information so they calculated how much power could have been generated. they had the power output data to the pant and know the amount of natal gas the plant is allowed to burn. So that calculated how much power could have been generated with gas Ivanpah consumed Then they compared that to the actual numbers. The critics can also say the conversion factor used is not correct.

    So neither the critics or Ivanpah are wrong. Each is using valid data. Each is using different assumptions in their calculation. And there is nothing wrong with either of those assumptions. The critics are looking at the total gas consumption while Ivanpah’s data is only for gas consumed when the generator is generating.

    • Future solar thermal plants might need to use an underground ‘thermos bottle’ to store the hot water between cycles.

      • The Cressent dunes solar thermal tower in Nevada will not need a thermos or natural gas since it is using molten salt.Cressent dunes will set asside some hot salt to preheat the turbine just before the sun comes up.

        • I suspect any future thermal solar will use molten salt in order for the output to be dispatchable. I doubt thermal solar can go head to head with either PV solar or wind when they are producing.

          The question, I suspect, is whether it can compete with stored wind and PV solar.

          • Susan stated –

            “Molten salt can stay ready in the storage tank essentially for months”

            If this is the case then thermal solar might play a major role in ‘deep storage’. During periods where we have sequential days with low wind/solar input we might be able to pull power out of massive underground caverns of molten salt.

            Too far off base?

          • I’d be nervous storing any 1050 degree F liquids in natural formations under ground! The tanks are a pretty cheap part of the plant.

          • Excavate a cavern. Line it with concrete. Insulate over the top.

            Leaked salt would not be an ecological disaster. You’d basically just have a big lump of fertilizer (whatever was used as the salt).

            “The last 1%” may be the most valuable power on our grids. If you haven’t read the Budischak paper you might give it a quick look. They modeled an all wind/solar grid using real world demand and wind/solar production for a four year period.

            They found that storage and overbuilding was too expensive for the last little bit (about seven hours a year). They used natural gas to fill in that last bit. That, and “days three, four, …” of low wind/solar input might be a place where thermal solar could make some money. If they had big amounts of very hot salt stored away.

            The orange blips in the bottom line. That was the part that they turned to natural gas to supply.

            Budischak, et al. –


          • Thanks, will read that. Yes, its a benign material but my concern about storing it underground is the temperature extreme. 1050 degrees F is hot!

          • I don’t think it’s zero sum. We need more than two renewables to kill off all coal, gas and oil, AND switch out gasoline transport for EVs. Once EVs finish off the ICE cars that will create a massive new electricity demand. Mainly, I see thermal solar for evenings with storage.

          • Yes. That’s what I’ve thought for a long time. But the question will be whether thermal with storage will be less expensive than solar/wind stored in a more generic system (batteries, PuHS).

          • We’ll know by 2021 when the first battery with as much storage as a solar thermal storage online now (Abengoa’s Solana is the most after pumped hydro at IIRC ~2,000 MWh/a day, at least 30 years of cycling) comes online. In 2012 we’ll know did batteries work at that scale, and is it feasible with short cycle life? It is a big jump from the few MWh now. Crescent Dunes is 1,100 MWh a day. No battery does that.

            We don’t want to get to 2021 and realize, uhoh, to avoid curtailment, PV needs more battery at utility-scale than is possible: the utilities will then argue lets build a gas plant instead.

    • Sorry. Susan went to all that trouble to get all those number and publish them. To honor her work, you need to show some numbers for the critics which are valid. Which NG is used when not used for generation? How much. Whats it for? References.
      I don’t read her article that way, but maybe I am wrong. Clarify.
      There need not be any rumors. Critics are fine, but reliably sourced numbers and facts are better.

      • The critics are not calculating how much natural gas was used for power generation. Instead they are totalling up all the CO2 emmissions of Ivanpah and comaring that to conventional natural gas power plants Their calculations concluded that Ivanpah’s total emmissions were equivelent to Ivanpah’s power production being 25% from natural gas.

        In Comparison A conventional motlen Salt solar thermal facility will not burn any natural gas for months. A PV solar facility will never burn natural gas. Ivanpah burns natural gas daily.

        In comparison Ivanpah is not counting any CO2 emissions from the burning of natural gas when the generator is not producing power. The natural gas is burned to keep things warm at night. If everything stays warm then the system can immediately start producing power when the sun comes up The nighttime consumption of natural gas is not counted in Ivanpah’s data. However in reality some additional gas will need to be burned in the morning for the turbine startup.

        • Steven – thanks. You are a gentleman and a scholar. Perhaps ivanpah will switch to storage to maintain night heat. Looks like molten salt is more favorable. IMO, these projects are viewed unfairly. They are large scale development projects that can provide new data points, energy benefits, and advance development lowering cost. They are not BAU generation. That’s why Crescent Dunes is already different tech with molten salt.
          They should be viewed as valuable steps along the development path.

  • This solar thermal contraption obviously cannot economically compete with PV during the day.

    My question is: when are we going to see real operating data showing how well it is doing at producing energy from stored heat? Saving the head of the duck is where this kind of technology has value. Does the existing proof of concept system have no real thermal storage at all?

    I periodically check California’s ISOs Daily Renewable Report and only see it running during the day. For example, yesterday solar thermal peaked at 9:01 AM and production slumped to almost nothing in the afternoon while PV was still pumping out 4GW+. In many cases the production seems to *lead* rather than lag the PV production.

    Off topic but CA is producing 12GW of renewables as I type… I think it’s a record but I’m not sure. LMP prices in central california are negative once again during a work day.

    • Why is this system generating electricity during the day? Does it not have suitable storage? It is clear that the only good application for solar thermal is at night, so it really should be heating up in the day and then turn on the turbines at sunset.

    • This project was not built with storage. PG&E and SCE didn’t want storage in 2008. Direct steam is not suited to storage and why: see my comment upthread.

      • Simultaneous response. Tiebreaker to Susan. Yeah!

      • In 2008 PV was a lot more expensive than it is now. The current cost of PV solar is about 25% of what it was in 2008.

        It seems reasonable to have planned a system without storage if the projected price of electricity was lower than what was expected for PV.
        That’s my guess….

      • Thanks for the clarification. It would make sense in 2008 because nobody would have cared about storage much then as cheap PV seemed somewhat fanciful back then. I never really looked much at the details of the different solar thermal systems and projects so I just didn’t know.

        So since Ivanpah is just steam, is there any more “learning” that can be done with this plant compared to some of the other CSP solar thermal projects? Because if the opex to run the steam pot is high (not saying it is) and there’s not much more to learn in figuring out how to point the mirrors then why keep it going? Obviously this steam business is a dead end.

        Would it make sense to just tear down the steam towers and put up some new huge molten salt system that would be a unique R&D project compared to the other solar thermals because of its scale?

        • “…if the opex to run the steam pot is high (not saying it is) and there’s not much more to learn in figuring out how to point the mirrors then why keep it going? Obviously this steam business is a dead end”

          No, PG&E is sending out every MWh it generates. It is not just a test: every plant that’s built lowers the cost for the next one, even if not exactly the same. That’s how PV got so cheap, both silicon and thin film.

          The price per kWh (the various numbers thrown around range from 13 cents to 21 cents) is not that high compared to gas peaker plants (though, it is extremely difficult to get hold of gas PPAs as they are confidential) but which some estimate which appear to be in the 20-25 cent range per kWh.

          So are peaker plants considered to be an expensive experiment that should be torn down?

          • “So are peaker plants considered to be an expensive experiment that should be torn down?” I think that isn’t a bad question actually. Combined cycle is much more efficient. Batteries are much faster. If they contine to get cheaper, I can imagine them taking over long enough for the combined cycle plants to spin up. That could really pinch the peakers hours of operation, increasing their costs, and pricing them out of the market.

          • Are combined cycle power palnts used as peakers?

            I (with German/Austrian background) was under the impression that CC does not work as peaker for technical and commercial reasons (too low FLH).

            Here in Europe CC power plants are mid-load.

          • The gas turbines fire up quickly. It takes about three hours (?) for the steam turbine to reach full production. I wouldn’t think we’d build CCNG plants if we only needed short duration output, the steam turbine cost would be wasted.

          • Yes, same in the US: single cycle has traditionally been used for peaker plants as they are faster starting than CC. But some new models of CC are speeding up start times, so clean energy alternatives like batteries and thermal storage will be competing against CC as well.

          • Peakers are highly dispatchable. They hit above their weight class.

            I also wonder if it would make sense to covert over to salt so that storage could be added….

          • Conversion of fossil plants to solar thermal: wow – that IS an interesting idea to cover. I will ask around and see what the obstacles are

      • Okay… but you already have three giant concrete towers, surrounded by acres of tunable mirrors. All the paperwork, EIA studies, political backscratching, financing, structural design etc is already done. The big electrical connections to the grid are in place, as well as the giant generator and various bits of recitfying gear.

        Surely it should be possible, somehow, to build a new “circulatory system” that relies on molten salt rather than steam. All the expensive bits are already in place. We need some pipes, pumps, storage tanks, and potentially a different turbine.
        Why not simply strip out all the bits associated with steam, and replace with bits suitable for salt? Is it really impossible?
        (This is not a rhetorical question. I’d like to know.)

        • Yep, monumental: “All the paperwork, EIA studies, political backscratching, financing, structural design etc is already done. The big electrical connections to the grid are in place, as well as the giant generator and various bits of recitfying gear.”

          I’ll ask. Interesting question.

        • The turbine would not have to be replaced for the conversion. There is no advantage to changing it. Molten salt systems use the same steam turbines that Ivanpah uses.

          As to the mirrors those won’t have to be replaced but the mirror field may need to be reconfigured due to changes in the tower

          However the towers are probably not adaptable to a molten salt system:
          1) Molten salt is heavier than water or steam so Ivanpah’s steel towers may not be strong enough to handle the added weight of a molten salt system.

          2) Also the receivers that heat the water as well as the water pipes will fail at the higher temperatures of a molten salt system. At the higher molten salt temperatures the expansion and contraction of metal would be several times greater and things will breaks.

          3) The salt is corrosive so different steel would be needed.

          4) The ground mounted steam generator for the turbine would have to be scrapped. the salt to water heat exchanger for the molten salt system would have to be placed above the salt storage tanks. The salt must drain out at night to prevent salt freezing in the pipes. The added weight might require a new foundation.

          So realistically speaking they may have to replace the entire tower to switch to a molten salt system. Time to do it would be about 2 years. Add to that the removal cost of the boilers that are no longer need. It’s not going to be cheep and they will loss about 2 years of income.

          I am not saying it won’t happen. I am just saying the economics would have to look very good for them to decide to do it. Right now it makes a lot more sense to try and improve the performance by adding more insulation or by modifying the turbine. Once the construction loan is payed off it might make sense to switch to molten salt.

    • Yes. No storage. Its not a mistake, depending on how you view it. They were trying to build the next generation of very large CSP. If they designed with storage it would have been delayed. CSP doesn’t get much respect. And I agree with you, thermal storage is its ace.
      This design is an evolutionary one. Years ago, wind turbines were like this. They were still coming down the cost curve. Only now we have multiple renewables coming down in cost. I nice problem to have, IMO, you agree?

  • It would be nice if the 5% natural gas could be replaced with biogas from landfill waste, food waste or animal waste. NG has a lot of bad environmental trade off, including fracking and earthquakes.

    • What a great idea! And IIRC there are quite a few big dumps on the other side of the border…

Comments are closed.