The "Duck Curve"
was used by California
Independent System
Operator (CAISO)
to explain how the
addition of renewables
affected the electric grid.
The top line
of the duck shape
is the hour by hour
electric generation
BEFORE the addition
of renewable sources
of electricity.
The orange
duck-shaped
body depicts
the effect of
adding renewables
to an electric grid,
year by year,
starting in 2013
( top of duck body ) ,
and ending in 2020
( bottom of duck body ).
Lighter lines inside
the "duck" body
are for the
intervening years,
depicting the load
supplied by baseline
power generation
gradually declining
as renewable energy
sources ramp up.
The entire orange area
is supplied by renewables
as of 2020 ( an estimate ).
"Baseload power"
is typically natural
gas combined cycle
( NGCC )
power plants,
coal, nuclear, and
hydro power.
As more renewables
are added to the grid,
the amount of electricity
supplied during daylight
hours is increasingly
coming from renewables,
primarily solar energy,
in this California depiction.
Baseload power
must be reduced
quickly as the sun rises,
to allow renewables
to supply the grid.
When the sun sets,
baseload power
must suddenly
ramp up to meet
the electricity demand
in the evening.
The sudden ramping up,
and ramping down,
of the power
affects power plants,
with extra wear,
( except hydro power )
and also affects
various components
of the grid, from
thermal expansions
and contractions.
Renewables
provide only
intermittent
electric power.
The sun may become
partially blocked by clouds.
The wind can stop blowing
( less than a 6 mph wind )
or blow too fast for turbines
( over 55 mph wind ) ,
or the temperature can
become too cold for turbines
( below -20 degree F. ).
Constantly varying
solar and wind power
means baseload
power plants
must be cycled up
and down to offset
those variations.
Power plants
are less efficient
when they are cycled
that way, which also
causes an increase
in their air pollution,
such as NOx.
During nights,
most electricity
must come from
baseload power
plants.
They cannot
be dismantled
and eliminated
unless electricity
generated during
the day can be stored.
As renewables supply
an increasing amount
of electricity,
the above
problems
get worse,
and baseload
power plants
become money
losers.
They may be
closed down,
unless they receive
government subsidies.
Storage of electricity
needed for 24 hours
is possible, but also
very expensive.
Storage
of electricity
needed for three
consecutive days,
( that are cloudy with little wind ),
would cost trillions
of dollars for the
entire nation.
Who would pay ?