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Wind
Integrating Wind's Unique Characteristics
Wind is intermittent, volatile, and
will ultimately be sited where the resources are most economical. Wind
generation output cannot be initiated and controlled by an operator, and
over any given 24-hour period, output can only be estimated. Wind resources
are notoriously volatile, at times rapidly ramping up from near zero output
to peak output and back again in a matter of hours. These characteristics
can complicate the integration of wind power into electrical systems for
a number of reasons. And even though the precise costs
and impacts of these complications on electrical systems are still a subject
of debate, they are nonetheless emerging as limiting factors, and the
long-term growth of wind power development in the United States depends
on their resolution. Consequently, these unanswered questions are the
subject of ample research by wind industry stakeholders.
Some of these integration issues
are outlined below:
- A primary concern for system area operators integrating intermittent
wind power is that when the wind turbines aren't producing electricity
to meet load, other generation resources must be available to maintain
line voltage requirements and ensure a balance between load and aggregated
power supply. Consequently, operational and scheduling systems must
adjust generation patterns to accommodate these fluctuations.
- Getting wind power from its source to the energy buyer may require that the electrons pass through multiple transmission areas, the process of "wheeling" the power, which add costs. The National Wind Coordinating Committee Transmission Case Studies Project includes an analysis of "virtual wheeling" (Case Study Two), a purely financial energy transaction that obviates the physical or spatial limitations of distant wind power.
- The American Wind Energy Association also provides a detailed outline of the operational issues of wind power integration.
Wind Forecasting
Wind forecasting is the technology that makes it possible to integrate bulk wind power into electric systems. Effective predictions of short-term availability are statistically predictable to within 1 to 2 hours and increase wind's value to the utility for supply scheduling purposes and decrease the costs associated with inefficient or unnecessary reserve while minimizing potential supply imbalance penalties. Next-hour and next-day wind resource forecasting has proven to be a highly reliable tool for resource scheduling.
Integrating Wind Power into Independent Transmission Organizations
Another concern, also stemming
from wind's volatility and inability to be scheduled far in advance, is
that the operating rules of some independent transmission organizations
are discriminatory to the intermittent nature of wind generation. Using
a tariff under FERC Order No. 888, these transmission areas can impose
supply imbalance penalties when supply is not delivered as scheduled.
Wind industry stakeholders view these penalties as excessive (partly because
they are more punitive than based on any marginal cost power delivery).
The party responsible for bearing the costs of any imposed imbalance penalties
varies by contract, and in recent wind power proposals to the California
Power Authority, two separate development deals specified the seller and
the buyer, respectively, as responsible for these charges.
Transmission rules and penalty
structures now vary by regional transmission organization, and many, especially
those with increasing amounts of wind power on the system, are addressing
wind's unique characteristics by eliminating or softening penalty structures
that the wind industry views as discriminatory. For example, ERCOT in
Texas requires that wind suppliers provide a 1-hour availability forecast
to schedulers, but it waives penalties for supply that is off in either
direction by less than 50 percent. Other entities in the West, such as
the Boneville Power Administration, currently have prohibitively high
penalties for just a few percentage points' deviation from anticipated
supply, but this likely to change. The National Wind Coordinating Committee
monitors the changing environment of regional
transmission operators.
American Wind Energy Association, a wind industry trade association, has established a set of transmission priorities and proposed solutions to overcome obstructions to wind power development that arise from current discriminatory policy, access and pricing practices. AWEA has published Fair Transmission Access for Wind: A Brief Discussion of Priority Issues.
NWCC's
Transmission Working Group has published Wind
Power in California's Restructured Electric Market: Wind and the California
Independent System Operator, a case study analyzing the independent
system operator's impacts on and future role in the state's wind power
development. Recognizing wind's potential in California's generation portfolio,
the California ISO recently developed a market arrangement using innovative,
state-of-the-art forecasting services to allow wind to be bid into wholesale
markets in a way that will minimize scheduling problems. "California
ISO Wind Generation Forecasting Design and Experience," detailing
this forecasting solution and its eventual role in the CA ISO.
One
potential solution to the wind power integration problem is proposed in
the study Coal and Wind Plant Integration which investigates placing
wind plants at or near the point of transmission interconnect for a new
or existing coal-fired power plant. The two power plants then share the
transmission capacity, with some amount of coal generation sacrificed
to transmit wind power. The study concludes that there are a variety of
benefits to integrating wind and coal generation, including reduced emissions
relative to a stand-alone coal plant, the creation of a combined system
with a stable price profile, and the ability to unlock wind resources
through new transmission developed for coal generation.
At the federal level, Pat Wood, the Federal Energy Regulatory Commission chairman, has declared it a FERC priority to spur transmission-line construction, strengthen federal power market oversight, and streamline transmission-line operations. Before assuminghis current post, Wood guided the Texas Public Utility Commission through a restructuring process that included aggressive measures to accommodate wind power integration. Because Wood is also a staunch proponent of competitive wholesale generation markets, it is likely that FERC will instigate actions to expand and facilitate the integration of intermittent generation while eliminating rules and practices that obstruct it.
Other reports on these and other transmission-related issues can be found on the National Wind Coordinating Committee's Web site.
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