POWER May 2015 - 64

COMMENTARY
Texas Reliably Integrates
Growing Wind Resource
H.B. " Trip " Doggett
I
f you have been paying attention to renewable energy growth
in the U.S. during the past decade, you likely know that Texas
leads the nation in wind power development.
In fact, the portion of the state that is served by the Electric
Reliability Council of Texas (ERCOT)-about 75% of land area
and about 90% of the electric load-ended 2014 with nearly
12,500 MW of installed wind generation capacity. Interconnection
agreements and studies indicate installed capacity could
surpass 18,000 MW by the end of this year, potentially topping
21,000 MW by the end of 2016.
At 14% of total generation capacity in 2014, wind provided
about 10.6% of the energy used on the ERCOT grid last year,
and instantaneous output reached a record 11,154 MW this
past February.
Although our competitive energy-only market does not favor
one fuel over another, ERCOT, as the independent system operator,
has worked to understand the unique aspects of wind
resources so we can integrate them effectively, efficiently, and
reliably into grid and market operations.
Managing Rapid Growth in the Nation's Leading Wind
Power State
The growth in wind capacity occurred rather quickly, from 116
MW in 2000 to more than 10,000 MW by the end of 2012, surpassing
the Renewable Portfolio Standard set forth in 2005 by
the Texas Legislature-10,000 MW by 2025-more than a dozen
years early.
At first, most wind capacity in the ERCOT region was concentrated
in West Texas, where there was little demand at the time
and few paths to move the power to load centers within the
ERCOT grid.
By the end of 2013, transmission providers had completed
about 3,600 miles of new 345-kV transmission facilities, with
capacity of 18,500 MW, to move power from the West Texas and
Panhandle areas to other parts of the grid. This $6.9 billion Competitive
Renewable Energy Zones project was directed by the
Texas Legislature and the Public Utility Commission of Texas.
Using Future Forecasts to Support Real-Time Success
As a result of rapid growth, ERCOT planners and operators have
learned a great deal in a short period of time about how wind
farms perform and what to expect under a variety of conditions.
The forecasts that help ERCOT manage this dynamic resource
in its nodal market must be as accurate as possible. In daily
operations, ERCOT experts evaluate wind forecasts-which consider
location, technology, and weather patterns-to prepare for
likely outcomes and position the system to maintain reliability.
ERCOT also takes wind generation variability into account when
determining ancillary services requirements.
For planning purposes, a combination of experience, improved
data, and wind generation technology has led ERCOT
to change how we model the capacity contribution from wind
64
generation resources, based on expected performance during
peak demand, for both its seasonal and longer-term resource
adequacy assessments.
Before we had significant historical data, ERCOT counted
wind resources at 10% of installed nameplate capacity. In
2007, we began to count wind capacity at 8.7%, based on
a probabilistic assessment of reliability compared to a dispatchable
resource. This " effective load carrying capability "
remained in place until 2014.
At 14% of total generation
capacity in 2014, wind provided
about 10.6% of the energy used
on the ERCOT grid last year.
After studies in 2010 indicated ERCOT could expect a higher
percentage of installed capacity over peak, we tested these assessments
and ultimately changed our practice. The passage of a
new market rule in October 2014 established a mechanism that
enables ERCOT to predict more accurately in our planning process
the wind resources upon which we can expect to rely as these
resources continue to increase and change.
The new method uses historical data from the top 20 peak
hours each year over a six-year period to project summer and
winter wind availability on peak. So, rather than applying a set
percentage to the entire portfolio, the formula accounts for performance
improvements and the location of facilities. In recent
years, development has increased along the Gulf Coast, where
coastal breezes are more likely to produce higher outputs during
hot summer afternoons, when power demands in the ERCOT
region are greatest.
Based on the new rules, ERCOT's 2014 Peak Average Wind Capacity
Percentage for facilities along the Gulf Coast is 56% during
the summer and 36% during the winter. We expect facilities
in other parts of the ERCOT region will provide 12% of nameplate
capacity during the summer and 19% during winter.
Continuing to Adapt and Look Ahead
Currently, it appears wind generation will continue to grow in
the ERCOT region. As we integrate more of this growing resource,
as well as emerging utility-scale solar power resources, we will
continue to learn and apply more understanding of our diverse
generation mix to provide a reliable grid and efficient market. ■
-H.B. " Trip " Doggett is president and CEO, Electric Reliability
Council of Texas Inc.
www.powermag.com
POWER | May 2015
http://www.powermag.com
POWER May 2015

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