Renewable energy vs. the electric grid - Solar, Wind and Land: Conflicts in Renewable Energy Development - page 160

On an electricity grid, supply and demand must be balanced continu-
ously to maintain a variety of physical network criteria—like frequency,
voltage, and capacity constraints—within narrow bounds. Electricity is
the ultimate “just in time” manufacturing process, where supply must
be produced to meet demand in real time. 55
Historically, grid operators have had a difficult enough time using conven-
tional coal—nuclear—or natural gas-fired power plants to balance
electricity supply and demand on electric grids. The aggregate quantity of
power demanded across a grid system varies from moment to moment as
electricity consumers respond to such factors as the outside temperature or
the time of day. Grid operators have little or no control over these minute-
by-minute changes in electricity demand, but fortunately they can exert
some control over the quantity of electricity that conventional power plants
supply to the grid. By ramping electricity production up and down at these
plants in response to real-time variations in electricity demand, utilities and
grid operators are typically able to ensure that no one goes without power
and that no excessive power overloads damage the grid. 56
Allowing wind and solar energy systems to feed electricity onto an
electric grid makes grid operators' perpetual balancing act at least twice as
difficult to perform. Adding intermittent renewable energy sources into the
power mix can force grid operators to simultaneously respond to fluctua-
tions in both the demand and the supply of electricity on the grid. Utilities
confronted with this arduous task have sometimes responded by cutting
back their electricity purchases from renewable energy projects that they
perceive to be the source of their problems. Whenever this occurs, disputes
between renewable energy generators and grid operators are bound to
follow.
Publicized clashes between wind energy generators and grid operators in
the northeastern United States highlight the tension that can build between
renewable energy generators and grid operators as renewable energy
systems feed ever more power onto the grid. To prevent the variability of
wind-generated electricity from damaging its transmission infrastructure,
ISO New England has been known to block wind-generating power from
entering its grid systems during periods when electricity supply far exceeds
demand. These “curtailment” practices have cost wind energy generators
in the region of millions of dollars, infuriating the owners of multiple
wind projects. 57 As an angry wind energy executive from the U.S. state of
Vermont put it:
We have a grid system that's not smart—it's kind of dumb, it's a
100-year-old system—and they run it like fossils and nukes are the only
things that matter and the rest of us, they can fiddle with. 58