IEEE Power & Energy Magazine - March/April 2021 - 29

Efforts to
Coordinate
Electric and
Gas Systems

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of meeting 60% of its electrical supply
needs with renewable energy by 2030
and 100% of them by 2045.
With the rapid transformation to a
cleaner but more variable and energylimited generation fleet, CAISO is developing new policies and practices to support the unprecedented transformation of
its electric system. This transformation
is rapidly changing the landscape of the
system's generation mix to meet demand.
Currently, the supply mix of the CAISO
system is composed of generating facilities with different technologies and fuel
sources, namely nuclear, gas, hydro,
solar, wind, and, more recently, batteries.
CAISO also relies on imports from the
northwest that are predominantly hydro.
Clean and variable energy production is
growing in the system while more conventional thermal generation is retiring as part
of environmental goals, such as meeting a
once-through-cooling compliance policy,
which results in the retirement, repowering, or remediation of coastal power
plants. Figure 2 illustrates an hourly production mix on a typical 2019 summer day. Gas generation accounted for about 32%,
followed by renewables with 26%, and imports with 22%. As
renewable production steeply reduces in the evening, gas and
hydro generation, together with imports, ramp up to compensate
for it.

excess renewable energy available to participating utilities
at a low cost rather than curtailing the production of clean
energy. This also leverages the regional and economic
diversity of the broader area and allows for more flexibility in scheduling and dispatching generation. Since its
inception in 2014, the EIM has resulted in gross economic
benefits of more than US$1 billion. In the context of gas
supply availability, the EIM allows for more geographical, economical, and technological diversification in the
extended market footprint.

The Supply Mix in California
Is Rapidly Evolving
The electric grid is rapidly evolving and transitioning
toward a clean and environmentally sustainable electric system. Grids around the world are working to meet aggressive
renewable goals. As a result of California's SB100 legislation, passed in 2018, the state is working toward its goal
march/april 2021

Supply Adequacy
and Availability
The CAISO system relies on a bilateral-based mechanism to
secure capacity, unlike some other ISOs that rely on capacity
markets. This resource-adequacy program is administered by
CAISO and developed by local regulatory authorities with the
California Public Utilities Commission (CPUC). At the onset
of this program in 2006, the generation mix of the system was
predominantly conventional generation technologies, such
as nuclear, gas, and hydro resources. Some of these resources
had a limitation on the energy they could produce due to
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IEEE Power & Energy Magazine - March/April 2021

Table of Contents for the Digital Edition of IEEE Power & Energy Magazine - March/April 2021