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Rolling blackouts returned to the California Independent System
Operator (CAISO) on Friday, 14 August, for the first time since the
2001 energy crisis. More than 400,000 customers lost electricity
between approximately 6:40 pm and 8:40 pm, equivalent to 1,000 MW
of load. Another blackout occurred the next day but only 500 MW of
load was lost for 20 minutes—between 6:30 pm and 6:50 pm. CAISO
warns that tight power supply and hot weather could lead to power
outages again later this summer.
The Friday electricity shortage took almost everyone by
surprise. Hot weather pushed power demand to its highest
year-to-date point, but not atypically so. Peak demand that day was
46,268 MW and was very similar to what occurred in 2018, despite
what a Stage 3 Emergency might imply.
Instead, peak net load was the challenge. Net load is
electricity demand less renewable generation and it must be met
with dispatchable generation (for example, natural gas and
batteries). Peak net load was 39,485 MW at 7 pm and might have gone
as high as 40,485 MW prior to the rolling blackouts; however, it
was not unprecedented. Peak net load was over 4,000 MW higher in
2017 and blackouts did not occur then.
Ultimately, the causes of the blackouts were on the supply side
of the power market. The dependability of renewable capacity, in
this case wind, during critical hours will likely be re-examined by
policymakers and the grid operator. Although sophisticated
simulations are used to determine what amount of renewables are
likely to be available during tight supply hours, the events of 14
August may provide additional data that can be used to improve
future evaluations.
Resource adequacy policy and its incentive structure for
dispatchable generation may also be reviewed. According to a CAISO
report, 5 GW of power plants were unavailable when the grid
operator only needed 1 GW of incremental supply to keep the lights
on. Natural gas units physically located in CAISO were the largest
type of generation unavailable, amounting to about 6% of total gas
capacity physically located in the market. However, this level of
gas outages is not abnormal—roughly twice as much was offline
on the peak net load day in 2018. Some hydroelectric capacity and
generators located outside CAISO were also unavailable when grid
operators needed them on 14 August.
Looking forward, California will likely continue transitioning
to lower carbon power supply and address reliability issues along
the way. Policymakers can look to eastern US power markets,
particularly PJM, for lessons learned about generator outages. In
addition, CAISO's resource adequacy position will be strengthened
in the coming years by greater battery build. Ultimately, lessons
learned from CAISO's 14-15 August blackouts could help other grid
operators avoid a similar event, thereby supporting the global
transition to lower carbon power supply.
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