Pacific Gas & Electric
( PG&E )
has shut down
substantial portions
of its electric
transmission lines
in northern California
several times.
The utility claims
wind / tree damage
to infrastructure
could start wildfires.
That makes sense.
Of course having
proper maintenance
of the trees near
transmission lines
makes more sense.
The Federal Energy
Regulatory Commission
( FERC )
and North American
Electric Reliability
Corporation
( NERC )
allowed PG&E to do
electricity shutdowns.
I'm wondering
if there was
a second reason,
not discussed, for
PG&E to temporarily
shut off electricity.
Maybe not enough
PG&E electricity
was available for all
PG&E customers,
because their
wind turbines
automatically
shut down
from the high
wind speeds
that were
spreading
the wildfires ?
Here's the story:
According to Energy
Information Administration
data, California generated
74.3% of its electricity
from fossil fuels
and nuclear energy
in 2001.
Hydroelectric,
geothermal,
and biomass-power,
accounted for most
of the remaining 25.7%,
with wind and solar
providing only 1.98%.
By 2018,
renewables
were 43.8%
with wind
and solar
up to 17.9%.
Solar power
depends on
sunlight.
So at night,
when the
solar panels
are worthless,
you would hope
there's enough
wind speed
to move the
wind turbines.
But not too much wind !
Wind power
depends on
wind speed.
A 6 or 7 mph wind
gets a turbine moving.
( aka "cut in speed" )
A 30 mph wind
is required
to generate
maximum power.
But if wind speed
is too high, typically
around 55 mph,
the wind turbine
will shut down.
( aka "cut-out speed" )
A wind turbine rotor
is connected to
an electric generator.
The connection is
made through
a gearbox,
that turns
the generator
at the
speed needed
to produce
60 Hertz AC power.
Wind turbine blades
are airfoils.
Adjusting the pitch
(angle) of the blades
allows the rotor
to maintain a
constant speed,
which allows
the generator
to maintain the
constant speed
it needs to
safely deliver
power to the grid.
Blade pitch
adjustment
is limited.
If the wind
is blowing
so hard that
pitch adjustment
is not possible,
the wind turbine
shuts down.
And that's
a second
electricity
problem
caused by
high winds.