A Utility Perspective of Wind Energy - Wind Turbine Technology: Fundamental Concepts of Wind Turbine Engineering - page 733

lished Clean Renewable Energy Zones (CREZ) with additional transmission capacity built as
needed, so individual wind projects do not have to bear the cost of new transmission lines. In
Germany, power companies are required to bring the power lines to new projects, again at no
cost to the project developer. Of course, in both cases the consumer or tax payers cover the
transmission line and substation cost, which is similar to the process used when major hydro
electric plants were built.
Grid Access Rules
In addition to transmission lines, grid access priority is an increasingly important issue
as wind penetration grows above 15 percent. In regions with strict “least-cost” and “first-
in last-out” power generation dispatch policies, this becomes the primary impediment to
realizing the full potential of wind power. In February 2007, the Federal Energy Regula-
tory Commission made a ruling titled Preventing Undue Discrimination and Preference in
Transmission Service to allow greater access to transmission lines for power generators of
all generation types, including renewable energy projects [FERC 2007]. The new rule ex-
empts intermittent power generators, such as wind power plants, from excessive “imbalance”
charges when the amount of energy they deliver is different from the amount of energy they
were scheduled to deliver. To help accommodate less predictable forms of renewable power
generation, the rule creates a “conditional firm” service to deliver power from a generator to
a customer, allowing the power supplier to provide firm service for most, but not all, hours
in the requested time period.
A key aspect of the new rule is that it eliminates the broad discretion that transmission
providers currently possess in calculating the unused, available capacity on their transmission
lines. Instead, the new rule requires public utilities to work with the North American Reli-
ability Corporation to develop consistent methods of calculating the available capacity and
to publish those calculations to increase transparency.
In the future it is expected that grid access priority policy will shift from “least cost” to
“least carbon” in determining priority access to the grid. “Least carbon” may in fact be least
cost, if health affects, climate change costs, and security costs are considered along with the
price of electricity.
Power line capacity rating systems may also unduly restrict wind plants. Transmission
line capacity rating is typically based on the high-temperature thermal capacity under worst-
case conditions. This occurs on the hottest summer days with no wind for convective cooling
of the wires. Of course wind plants would not be operating under those conditions.
Technical Issues
As discussed in Chapter 4, integrating wind power into existing utility power systems
has been successfully accomplished in a variety of geographical locations, using many differ-
ent turbine configurations. Utilities are still concerned, however, that as the size and numbers
of wind power plants increase, there could be adverse effects on power system operating
strategies, system protection, and personnel safety. The expanding experience of utilities
working with independent power producers in operating large-scale wind power plants has
reduced these concerns. By 2008, wind generation capacity has surpassed 7.5 percent in
Minnesota and Iowa with no significant impact on grid system operations, and wind power
has more than 4 percent penetration in Colorado, South Dakota, Oregon and New Mexico.
Texas has over 7,000 MW of wind plants and 6 percent wind penetration.