Mailbag: Matt Writes: Shares a response on how wind energy works in the grid and some limitations of wind.

This was a response to a question concerning wind
energy and how it works in the grid. Thanks, Matt

> Let me attempt to clarify answers to the question
you recently posed
> about wind energy and grid capacity, building upon
the responses you
> received from Tom Hewson and Eric Rosenbloom. If you
want a more
detailed
> understanding of these issues, I suggest you read my
paper, Less for
> More: The Rube Goldberg Nature of Industrial Wind
Technology.
>
> Power grids maintain a dynamic equilibrium between a
range of supply
> generators and the pulsating fluctuations of demand
(more commonly
known
> as "load"), using large, inflexible but very
effective power plants
such
> as nuclear, large coal plants, and, in certain areas
where it is
> relatively abundant, hydro, to supply base load and
bringing on
board as
> needed smaller, flexibly responding generators such
as natural gas,
coal,
> oil, and hydro to respond to various levels of
demand, including
> minute-by-minute load fluctuations. Unlike wind
turbines, all of
these
> conventional generating units must pass rigorous
performance tests
to
> insure they can function reliably and can generate
an expected,
steady,
> stream of electricity. (This, by the way, is the
standard definition
of
> "power": energy that is available and can perform
as expected when
needed
> for use.)
>
> Wind technology poses two fundamental problems with
the way it sends
> energy to the grid. First, the wind typically blows
hardest when it
is
> least needed to supply demand--at night, when
inflexible base load
> generators hold sway. At small levels of penetration
during this
time,
> wind energy is simply treated as "negative load,"
for grid operators
> simply see more energy than there is demand for it
and turn down or
off
> an existing flexible conventional generator to
compensate. If the
> penetration levels of wind energy approach, say, 5%
of the grid's
> installed capacity, such an amount at night may be
more than can be
> compensated for by existing levels of load following
generators, in
which
> case the grid has three options: it can refuse to
accept the wind
energy,
> as occurs occasionally in the US and much more
commonly in Germany
> (recently a province in Canada has placed a
moratorium on future
wind
> facilities there because of this concern); it can
build expensive
> transmission systems to shunt the wind energy to
sections within or
> without the grid region that can accept and balance
the wind
energy--as
> Tom pointed out ( West Denmark does this with
regularity,
dispatching its
> "excess wind energy to Sweden and Norway, where it
displaces hydro,
with
> no real savings in carbon emissions); or it can add
very costly
back-up
> conventional generation to follow and balance this
excess wind flux
> (Germany has also done this).
>
> As Tom also noted, wind energy is so unpredictable
and variable (a
recent
> Canadian analysis showed it was four times more
volatile than load
flux)
> that it brings virtually no capacity to the function
of the
grid--that
> is, it can rarely be depended upon to provide energy
when needed.
This is
> why it is a misnomer to refer to wind energy as
wind "power."
Estimates
> projecting a 10% or higher capacity credit for wind
energy are far
too
> optimistic, given real time analysis; the figure is
likely between
2-5%.
> This is the reason wind technology cannot really
replace significant
> levels of conventional generation, as Tom has
pointed out in a
number of
> forums. Given the fact that our demand for
electricity continues to
grow
> rapaciously, and since wind technology has no
functional capacity,
we
> will need additional conventional power plants in
the future--no
matter
> how many wind plants are constructed.
>
> The second problem with wind energy is its
unpredictable
intermittency
> and its volatile variability. A wind plant with a
rated capacity of
100MW
> may dump sporadically 70MW onto the grid and, 15
minutes later, may
be
> sending only 20 and, 15 minutes later, may be
sending nothing. And
so on
> and so on. Even at small levels of penetration,
this kind of
variability
> destabilizes the equilibrium between supply and
demand, requiring
exiting
> load following generators to work harder. Moreover,
and this is a
central
> point, NO ONE KNOWS WHICH GENERATORS WIND ENERGY
MIGHT TEMPORARILY
> DISPLACE AND WHICH GENERATORS WILL FOLLOW AND
BALANCE WIND ENERGY
> FLUCTUATIONS, ESPECIALLY IN LIGHT OF THE FACT THAT
GRID OPERATORS
> TYPICALLY USE A CONCEPT KNOWN AS 'ECONOMIC
DISPATCH' TO SELECT THE
POWER
> GENERATORS USED TO MEET TARGETED DEMAND LEVELS.
Given these economic
> considerations, it may well be that wind energy
might temporarily
> displace power from a dependable, flexible (but more
expensive)
natural
> gas unit, which emits less CO2 than coal units or a
hydro unit,
which
> emits no CO2. It is not at all clear that in most
areas of the
country
> wind energy would of necessity displace power from
coal units. AND,
ON
> THE FLIP SIDE, it is not at all clear that wind
flux would be
followed
> and balanced by clean hydro units or even
cleaner-burning natural
gas
> units. In many parts of the country, including my
own in Maryland,
the
> grid instability caused wind flux may well be
followed and balanced
by
> inefficiently operated flexible peak load coal
units, emitting a lot
of
> CO2 in the process. All these circumstances are
difficult to track.
As
> far as I know, there has been no independent
confirmation of wind
> industry estimates of carbon emission abatement due
to wind
technology
> based upon actual wind projects and system-wide
grid operations.
Industry
> "averaging" techniques should not be considered a
valid way to
measure
> this phenomenon.
>
> At large levels of wind penetration, the very
security of the grid
system
> becomes at risk, which would take a lot more
paragraphs to explain.
> Suffice it to say here that compensating for wind
flux, even at the
> smallest level, where it is indistinguishable from
load flux, has
> implications for costs: the costs of increased CO2
emissions, as
well as
> the economic cost of the conventional generation
needed to support
the
> wind energy.
>
> Hope this helps. Jon Boone