Pipe dream at Moss Landing: another reason Ontario was smart to get out of WCI

Moss Landing unit 7 was a California steam cycle electricity generator that ran on natural gas. Its nameplate capacity was 739 megawatts. That meant that its operator could have run it at or near capacity, i.e. at 739 MW, for days at a time if it so wished. Though it was an uncommonly efficient steam cycle generator, its owner, Dynegy, stopped producing power from it at the end of 2016 because of inability to profit in the California electricity system. The site owner, the regulated utility PG&E, recently received utility commission approval to install a battery pack on the site, with a capacity rating of 730 MWh.

At first glance, you could be forgiven for thinking there is some similarity in the capacity of the old steam plant (739 MW) and the capacity of the new battery pack (730 MWh).

But there is a significant difference. Note the “h” in the capacity unit for the battery: it stands for “hours.” That is to say, the battery pack is rated in megawatt-hours, not megawatts. That is to say, the battery capacity is given in energy units, not power units. Power is to energy as speed is to distance.

So will the new 730 MWh battery pack at Moss Landing be able to deliver anything close to 730 MW, like the old steam-cycle gas plant was? No. Like all batteries, it will be constrained by its C-rate, i.e. its current discharge rate; or, when expressed in terms of power, its E-rate. From the report of one Tesla enthusiast, the Moss Landing battery pack would discharge electrical power at the rate of 182.5 MW, for four hours. Assuming this is true, the battery pack would then need four hours to recharge. So over say a 24-hour period, it could theoretically provide three 4-hour blocks of 182.5 MW, for a total of 2,190 MWh. And there would be three 4-hour gaps in between those four-hour 187.5 MW bursts, during which the pack would be recharged, also at a rate of 182.5 MW. See the figure.

In light of this, is it not misleading to say, as Tesla cheerleaders do, that this battery pack will replace the gas plant with clean energy? Leaving aside that we haven’t even gotten around to how the battery will be charged, it is plainly false to say that a 730 MWh battery can replace a 739 MW steam plant.

The old steam cycle gas plant running at capacity (the dotted line in the upper figure) could have provided 17,520 MWh in the same 24 hours—8 times as much energy. But most important, it would have been able to output 730 MW continuously over those 24 hours; that’s why the dotted line is flat.

To get 730 MW for 24 hours straight, from batteries of the type Tesla is building at Moss Landing, how many battery packs would it take? Nominally, at least eight (don’t forget the four-hour recharge periods—i.e. those periods in which the green line in the upper figure is at zero).

The figure shows the Moss Landing Battery output at its theoretical (actually, its claimed) maximum, over a theoretical 24-hour day. Note that there are rechargings from midnight at the beginning of the day till 3 a.m., then 7 a.m. to 11 a.m, and then 3 p.m. to 7 p.m. The first recharge period occurs in the middle of the night, which obviously rules out solar as the recharge power source. Solar-based recharging is possible in the two daytime recharge periods, with many millions of square meters of solar PV panels installed somewhere, at somebody’s expense.

To show what I mean, see the figure below. It gives what would be needed to recharge a single Moss Landing battery pack. I put the panels at 32° North (the same latitude as San Diego, i.e. in the southern part of the state), and assumed perfect sun on the first day of summer.

The power (green curve) in the figure performs one of the chargings in the valley portion of the first figure. Note it occupies the entire day. Remember from the upper figure that there are three such chargings in the theoretical 24 hour day.

But solar-based recharging would be feasible only if there were a surplus of solar power, or rather a surplus of power during those periods—otherwise why would anybody in their right mind pay money to store electricity at a time that they need electricity.

In those periods where there is a surplus of power that makes storage theoretically desireable, the idea is obviously to supply that power from solar panels. As mentioned, many millions of panels would be needed. Unlike the hundreds of thousands of panels in the lower figure, many if not most of the panels to charge Moss Landing would actually be mounted on the roofs of high-priced urban and suburban homes, an expensive proposition both because of difficulty of installation and the value of the installation platform. You could be forgiven for thinking this will drive up the per-kWh cost of that solar power, and hence grid power, as it did in Ontario.

Add in the cost of battery storage, and you’re looking at extremely expensive electricity. My guess is, long before California gets anywhere close to actually outputting electricity from batteries anywhere close to the level of the old Moss Landing gas-fired steam unit, the state will have abandoned this patently idiotic idea.

But in the mean time, what will this spike in electricity prices do to the price of menial labour in California?

The California Public Utilities Commission okayed PG&E’s proposal for the Moss Landing battery project.

The Ontario media criticizes the new Ontario PC government for pulling out of the cap and trade system with California, the CO2 permit auction proceeds of which might have been funnelled into pipe dreams like the Moss Landing battery project.

To put it mildly, it’s a good thing we pulled out.

7 comments for “Pipe dream at Moss Landing: another reason Ontario was smart to get out of WCI

  1. November 26, 2018 at 18:42

    You have to wonder:  are these reporters deliberately sowing confusion by conflating MW with MWh?  Or is the source doing this, certain that the reporters won’t know the difference?

    If I haven’t made a mistake somewhere, it would take 24 Moss-sized packs to provide 730 MW continuously for 24 hours, not a mere 8.

    • November 26, 2018 at 19:30

      contributory obfuscation is my read, and let’s include CPUC, which has made a mockery of public utility regulation.

      My arithmetic: 4 182.5 MW packs = 730 MW. Each 24 hours they discharge 730 MW for three 4-hr blocks = 12 hours. So that much capacity again fills the valleys in the green curve, no?

      I’m the guy who recycles Daniel Kahneman’s story about the baseball bat and ball, don’t tell me I’ve repeated the usual error.

      All this is 100 percent based on Tesla’s claims.

      • November 26, 2018 at 20:04

        You said “730 MW for 24 hours straight” to be equivalent to the gas plant, not charging and discharging during the day.  Change the assumptions, change the conclusion.

  2. NukeWorker
    November 27, 2018 at 09:38

    I’m not sure I get the math. If the battery produces power for 12 hours a day at 182.5 MW, that’s 12 x 182.5 = 2190 MWh in a 24-hour period, not 547.5 MWh. Am I missing something here?

    Still a far cry from the 17,736 MWh per day of the gas plant.

  3. December 7, 2018 at 04:12

    As an adverse intervenor in CPUC Proceeding A.16-08-006, nonprofit NGO Californians for Green Nuclear Power, Inc (CGNP) roundly criticized the claim that solar power could replace the firm 2,240 MW generating capacity of Diablo Canyon Power Plant (DCPP) – which safely, reliably, cost-effectively generates 18 billion kilowatt-hours every year – with zero emissions. Our Opening written testimony developed the rough outlines of such a system. It would require about 200 square miles of solar panels which would be replaced every 20 years, a massive transmission system of 13 500 kilovolt 3-phase power lines spanning at least 200 miles, and a network of seven (7) Helms Pumped Storage Plants. The cost was an estimated $71 billion USD. Note that DCPP’s basis is about $8 billion and it is designed to last a century.

    CGNP observed legislation being passed when we testified against bills that were harmful to DCPP’s future before California Senate and California Assembly Committees in Sacramento at the State Capitol. In 2018, our targets were SB 1090, which passed and AB 813 which failed. Clearly, it is advantageous to be a deep-pocketed subsidy-seeker in order to procure California legislation .

    Sadly, the purpose of both solar and wind power in California appears to be to serve as public relations props to support the fossil-fired status quo.

    • December 7, 2018 at 10:29

      that’s their purpose everywhere—they’re physical PR, baked into the public mind as the wave of the future.

      They are why Tesla shares are going for well over $300.

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