Tag Archives: California Energy Commission

Hey, PG&E! Energy Storage is Not the Same as Energy Generation!!

Peter Lobner, updated 20 February 2022

The two-unit Diablo Canyon nuclear power plant, which is owned and operated by Pacific Gas & Electric (PG&E), is the last operating nuclear power station in California. In the five year period from 2016 – 2020, the average annual load factor performance of these power plants was as follows:

  • Diablo Canyon 1:  1,138 MWe net @ 91.56% = 1.042 Gigawatt-years (GW-years) generated per year
  • Diablo Canyon 2:  1,118 MWe net @ 85.64% = 0.957 GW-years generated per year

Over that five year period, the average annual amount of electricity delivered to the California electrical grid by the two-unit Diablo Canyon nuclear power plant was about 2.0 GW-years (2,000 Megawatt-years or 17,520,000 Megawatt-hours). On a daily basis, that’s an average of about 48,000 MW-hours. This electricity was generated reliably, 24/7 (except during planned outages), with zero carbon emissions.

The Diablo Canyon nuclear plant in Avila Beach, CA. 
Source: Joe Johnston / San Luis Obispo Tribune via LA Times (2018)

In 2016, I reported (http://lynceans.org/all-posts/the-nuclear-renaissance-is-over-in-the-u-s/):

“On 21 June 2016, PG&E issued a press release announcing that they will withdraw their application to the NRC for a 20-year license extension for the Diablo Canyon 1 & 2 nuclear power plants and will close these plants by 2025 when their current operating licenses expire.  PGE will walk away from about 41 GW-years of carbon-free electric power generation.”

The shutdown plan was approved by the California Public Utilities Commission in January 2018.

In 2019, PG&E reported that their mix of generation sources (owned and purchased from a third-party) looked like this:

Source: PG&E (2019)

A few interesting points about this PG&E generation source chart:

  • Nuclear power generation is the biggest piece of the pie chart. Shutdown of Diablo Canyon by 2025 will eliminate this piece.
  • Renewables include wind, solar, small hydro, geothermal and biomass / waste.  Batteries are not included because they are energy storage devices, not energy generation sources.  The energy stored in a grid-scale battery comes from a generator, or simply, from the grid.
  • Large hydro depends on the associated reservoirs having enough water in them. The Edward Hyatt hydroelectric power plant at Lake Oroville (California’s second-largest reservoir) was shut down in August 2021 for the first time since it opened in 1967 because of low water levels during the persistent drought affecting the US West. Power production at Oroville resumed in January 2022 with only a single hydroelectric generator, after heavy winter precipitation increased lake water level. If the drought continues, the large hydro piece of the pie chart will shrink.

Another point is that the PG&E generation source mix is quite different from the California state-wide generation source mix reported by the California Energy Commission in 2020 and shown in the following pie chart.  Not all of the generation sources represented in this chart are physically located in California (more on that later).

Source: Data from California Energy Commission (2020)
 

Diablo Canyon has a disproportionate impact on the PG&E  generation mix because they own the nuclear power plant and they take credit for its entire net generation.  State-wide, nuclear power makes up only 9.33% of the state generation mix in a much larger electric power market.

When Diablo Canyon is shut down in 2025, I would think that the PG&E energy generation mix will look a lot more like the California state-wide generation mix, with most of the nuclear power generation share being replaced, at least in the short term, by fossil fuel-powered generators.

In January 2022, PG&E announced that they have a plan: “PG&E Corp. said it has reached agreements to install nine new battery energy storage projects as part of a push to replace a retiring nuclear power plant and help decarbonize California’s power grid.”

So, let me see if I’ve got this right.  PG&E is going to use grid-scale storage batteries that produces zero carbon emissions during their operation to partially replace a nuclear power generating station that produces zero carbon emissions during 24/7 operation. Where will the power come from to charge those batteries?  It’ll come from the California Independent System Operator (CAISO) grid, which has the California state-wide generation source mix shown above, with almost 40% coming from fossil fuel-powered generators in 2020, and likely to increase after Diablo Canyon’s retirement. So, one charge-discharge cycle of a grid-scale battery isn’t carbon-free.

PG&E further announced, “The proposed projects would have a total capacity of about 1,600 megawatts, which would bring its total battery energy storage capacity to more than 3,300 gigawatts by 2024…”

On the surface, that sounds like an impressive amount of battery capacity, but let’s put it in perspective.

The former Moss Landing fossil power station on Monterey Bay was decommissioned and transformed into a grid-scale energy storage facility. In August 2021, after completing Phase II of the transformation, the facility was operating with a capacity of 400 MW / 1,600 MW-hours, making it the world’s largest grid-storage project. The facility’s owner, Vistra Energy, said the Moss Landing facility could be expanded to a capacity of up to 1,600 MW / 6,000 MWh.

At its current discharge capacity of 400 MW, the Moss Landing batteries could discharge their full energy storage capacity of 1,600 MW-hours in about four hours.  Then the battery is “empty” and needs to be recharged from the CAISO grid (as we discussed, that’s about 40% from fossil-powered generation sources in 2020). Of course, a grid-storage facility wouldn’t be operated regularly on such a stressful cycle. But my point is that the world’s largest grid-storage project is be capable of delivering no more than 3.3% of the 48,000 MW-hours of electricity delivered daily, 24/7, with zero carbon emissions, by the Diablo Canyon nuclear power plant.

California has a huge, and growing, energy problem of its own making. With Diablo Canyon and several fossil-powered generators scheduled for retirement in the next few years, the state needs new generating capacity.  However, the development time scale for a new large generating facility in California, especially considering the state’s challenging regulatory environment, might have to be measured in decades.

One of California’s solutions to its shortfall of electrical generating capacity is to import electric power from other states and nations.  The U.S. Energy Information Administration (EIA) reported that California was the largest net electricity importer, by a wide margin, of any state in 2019. Its net electricity imports were 70.8 million MW-hours, or 25% of the state’s total electricity usage. California utilities partly own and import power from several power plants in Arizona and Utah. In addition, California’s electricity imports include hydroelectric power from the Pacific Northwest and power from fossil and wind generators in Mexico.

Source: EIA

Grid-scale battery storage is not going to solve the state’s shortfall of electrical generating capacity. Rather, the batteries are a means to mitigate short-term demand peaks and help stabilize the grid as generators attempt to match energy supply with demand.

Another mitigating measure used by CAISO is a “flex alert,” which asks consumers to cut back on electricity usage and move their electricity usage to off-peak hours, typically after 9 pm.  CAISO issued five flex alerts in 2020 and eight in 2021. When a grid-scale battery is discharged during a flex alert, recharging it would add a large load on an already strained grid; probably not a good idea.

California is throwing away valuable 24/7 generating capacity and replacing it with intermittent renewable generators, with grid-scale energy storage facilities to provide short-term mitigation that doesn’t address the real underlying problem.  There is no substitute for adequate generating capacity, sized to meet the current and future demands of businesses and individuals as we try to move together into a more electrified future.

Failing that, I can see increasing electric power rates, more flex alerts, and in California, I wouldn’t be surprised to see some form of legislated energy rationing coupled with higher energy use taxation. So much for that vision of a more electrified future.

Don’t sell you gasoline or diesel-powered car yet.  You may need it during the next flex alert.

20 February 2022 update: Moss Landing battery fires

Since becoming operational, Vistra Energy’s Moss Landing battery storage facility on Monterey Bay experienced two damaging fire events in lithium-ion battery packs. A fire on 4 September 2021 set off fire suppression system sprinklers that damaged about 7,000 batteries. Vistra Energy reported corrective actions following this fire on 21 January 2022.  Another fire on 13 February 2022 resulted in 10 melted lithium-ion battery packs. The latest fire event was contained by the facility’s fire suppression system. Vistra reported that it was looking further into the latest incident, while the Moss Landing facility remains offline during the investigation.

For more information

Dispatchable Power from Energy Storage Systems Help Maintain Grid Stability

Peter Lobner

On 3 March 2015, Mitsubishi Electric Corporation announced the delivery of the world’s largest energy storage system, which has a rated output of 50 MW and a storage capacity of 300 MWh. The battery-based system is installed in Japan at Kyushu Electric Power Company’s Buzen Power Plant as part of a pilot project to demonstrate the use of high-capacity energy storage systems to balance supply and demand on a grid that has significant, weather-dependent (intermittent), renewable power sources (i.e., solar and/or wind turbine generators). This system offers energy-storage and dispatch capabilities similar to those of a pumped hydro facility. You can read the Mitsubishi press release at the following link:

http://www.mitsubishielectric.com/news/2016/pdf/0303-b.pdf

The energy storage system and associated electrical substation installation at Buzen Power Plant are shown below. The energy storage system is comprised of 63 4-module units, where each module contains sodium-sulfur (NaS) batteries with a rated output of 200 kW. The modules are double stacked to reduce the facility’s footprint and cost.

Buzen Power Plant - JapanSource: Mitsubishi

The following simplified diagram shows how the Mitsubishi grid supervisory control and data acquisition (SCADA) system matches supply with variable demand on a grid with three dispatchable energy sources (thermal, pumped hydro and battery storage) and one non-dispatchable (intermittent) energy source (solar photovoltaic, PV). As demand varies through the day, thermal power plants can maneuver (within limits) to meet increasing load demand, supplemented by pumped hydro and battery storage to meet peak demands and to respond to the short-term variability of power from PV generators. A short-term power excess is used to recharge the batteries. Pumped hydro typically is recharged over night, when the system load demand is lower.

Mitsubishi SCADA

Above diagram: Mitsubishi BLEnDer® RE Battery SCADA System (Source: Mitsubishi)

Battery storage is only one of several technologies available for grid-connected energy storage systems. You can read about the many other alternatives in the December 2013 Department of Energy (DOE) report, “Grid Energy Storage”, which you can download at the following link:

http://www.sandia.gov/ess/docs/other/Grid_Energy_Storage_Dec_2013.pdf

This 2013 report includes the following figure, which shows the rated power of U.S. grid storage projects, including announced projects.

US 2013 grid  storage projectsSource: DOE

As you can see, battery storage systems, such as the Mitsubishi system at Buzen Power Plant, comprise only a small fraction of grid-connected energy storage systems, which currently are dominated in the U.S. by pumped hydro systems. DOE reported that, as of August 2013, there were 202 energy storage systems deployed in the U.S. with a total installed power rating of 24.6 GW. Energy storage capacity (i.e., GWh) was not stated. In contrast, total U.S. installed generating capacity in 2013 was over 1,000 GW, so fully-charged storage systems can support about 2.4% of the nation’s load demand for a short period of time.

Among DOE’s 2013 strategic goals for grid energy storage systems are the following cost goals:

  • Near-term energy storage systems:
    • System capital cost: < $1,750/kW; < $250/kWh
    • Levelized cost: < 20¢ / kWh / cycle
    • System efficiency: > 75%
    • Cycle life: > 4,000 cycles
  • Long-term energy storage systems:
    • System capital cost: < $1,250/kW; < $150/kWh
    • Levelized cost: < 10¢ / kWh / cycle
    • System efficiency: > 80%
    • Cycle life: > 5,000 cycles

Using the DOE near-term cost goals, we can estimate the cost of the energy storage system at the Buzen Power Plant to be in the range from $75 – 87.5 million. DOE estimated that the storage devices contributed 30 – 40% of the cost of an energy storage system.  That becomes a recurring operating cost when the storage devices reach their cycle life limit and need to be replaced.

The Energy Information Agency (EIA) defines capacity factor as the ratio of a generator’s actual generation over a specified period of time to its maximum possible generation over that same period of time. EIA reported the following installed generating capacities and capacity factors for U.S. wind and solar generators in 2015:

US renewable power 2015

Currently there are 86 GW of intermittent power sources connected to the U.S. grid and that total is growing year-on-year. As shown below, EIA expects 28% growth in solar generation and 16% growth in wind generation in the U.S. in 2016.

Screen Shot 2016-03-03 at 1.22.06 PMSource: EIA

The reason we need dispatchable grid storage systems is because of the proliferation of grid-connected intermittent generators and the need for grid operators to manage grid stability regionally and across the nation.

California’s Renewables Portfolio Standard (RPS) Program has required that utilities procure 33% of their electricity from “eligible renewable energy resources” by 2020. On 7 October 2015, Governor Jerry Brown signed into law a bill (SB 350) that increased this goal to 50% by 2030. There is no concise definition of “eligible renewable energy resources,” but you can get a good understanding of this term in the 2011 California Energy Commission guidebook, “Renewables Portfolio Standard Eligibility – 4th Edition,” which you can download at the following link:

http://www.energy.ca.gov/2010publications/CEC-300-2010-007/CEC-300-2010-007-CMF.PDF

The “eligible renewable energy resources” include solar, wind, and other resources, several of which would not be intermittent generators.

In 2014, the installed capacity of California’s 1,051 in-state power plants (greater than 0.1 megawatts – MW) was 86.9 GW. These plants produced 198,908 GWh of electricity in 2014. An additional 97,735 GWh (about 33%) was imported from out-of-state generators, yielding a 2014 statewide total electricity consumption of almost 300,000 GWh of electricity. By 2030, 50% of total generation is mandated to be from “eligible renewable energy resources,” and a good fraction of those resources will be operating intermittently at average capacity factors in the range from 22 – 33%.

The rates we pay as electric power customers in California already are among the highest in the nation, largely because of the Renewables Portfolio Standard (RPS) Program. With the higher targets for 2030, we soon will be paying even more for the deployment, operation and maintenance of massive new grid-connected storage infrastructure that will be needed to keep the state and regional grids stable.