How utilities integrate wind energy

One concern surrounding wind power and its ability to provide a significant portion of the nation’s electricity supply in coming years is its variable output: Wind energy output is determined by Mother Nature, not by flipping a switch in a utility control room. Specifically, utilities and transmission system operators are frequently asked, or ask themselves, “How can we integrate larger amounts of wind power into our grid when the variable nature of wind energy output is not within our direct control?”

That question largely has been answered. Recent studies, as well as European experience, have shown that utilities typically can add wind generation to their power supply mixes without major adjustments in planning and operations and without affecting their systems’ reliability.

To address the questions about wind energy variable output, utilities and grid operators have conducted wind-integration studies. What’s more, real-life wind power growth has accelerated in regions demonstrating that wind projects can be successfully integrated throughout the United States where robust and geographically large markets exist, with no significant problems or cost implications.

Necessary Components

Increasing numbers of wind-integration studies performed for systems in parts of North America continue to assess how to integrate larger penetrations of wind power into utility and system grids. These studies are being conducted to determine how a large share of variable resources such as wind power impacts transmission system operations. These studies continue to show that wind power can be accommodated into the electricity grid at penetration levels up to 20 percent with minimal costs and impacts on the system and other generators.

These studies frequently point to certain factors for wind power to be integrated successfully. First, they point to the need for robust markets and geographic scope to accommodate large wind energy penetration, and they almost always point to the need for more transmission capacity to accommodate more wind power. With larger markets representing a broader region, more resources can be used to accommodate the variable energy output from wind projects at lower costs.

Second, the studies show the benefits to system operation and to the control room operators that come from having reasonable wind plant output predictions: This is wind forecasting’s unique and important role. Wind forecasting techniques provide system operators in the control room with detailed, expected, wind plant power output forecasts, allowing operators to effectively anticipate and plan accordingly. They can determine whether they’ll need to bring additional resources on-line, ramp down other resources and so forth.

The Backup and Cost Questions

To address wind energy’s variability, some incremental generation might be required for system balancing. While this is not a reliability issue, it can add a modest amount to the electricity’s cost. These include the costs of keeping the generators available and ready to operate and the fuel cost for operating them. The exact amount depends on the mix of generation on a given system and other factors.

A document prepared by the Utility Wind Integration Group in coordination with the trade associations of all three utility sectors (investor-owned, public and cooperative), along with utility studies and wind-integration experiences found that:

• Wind resources’ impacts can be managed through proper plant interconnection, integration, transmission planning and system and market operations.
• System operating cost increases caused from wind variability and uncertainty amount to about 10 percent or less of wind energy’s wholesale value.
• A variety of tools, such as commercially available wind forecasting, can be employed to reduce costs.
• In many cases, customers’ electricity costs can be reduced when wind is added to the system because operating-cost increases are offset by savings that arise from displacing fossil fuel generation.

Based on studies and surveys it conducted in different parts of the country, the Utility Wind Integration Group said, “(These studies) lay to rest one of the major concerns often expressed about wind power: that a wind plant would need to be backed up with an equal amount of dispatchable generation.”

Wind power in the United States will continue to grow, and the challenges of wind integration appear manageable. A 2008 U.S. Department of Energy report, “20% Wind Energy by 2030,” said that wind power can play a major role in meeting America’s increasing demand for electricity.

The 20 percent scenario analyzed in this report projects an aggressive increase in U.S. wind power growth. The portion of the study that looked at wind integration, however, found that the costs to integrate wind power are reasonable, reflecting the same results from the wind integration studies and real-life experiences documented to date.

Modest Challenges, Multiple Benefits

Wind power growth will present challenges and changes in grid operation, but they do not represent a major impediment to U.S. wind power growth. Utilities can integrate wind with little impact on operations or reliability. Wind power benefits utilities in ways beyond being clean and renewable.

Wind power provides a hedge against fossil fuel price volatility because the ongoing costs of wind energy are relatively fixed. This ability to hedge fuel price fluctuations in a utility generation portfolio, combined with increasing customer demand for renewable energy, makes wind energy more valuable to utilities than ever before. Thus, utilities are finding integrating wind manageable, and there are reasons to embrace the clean renewable energy because it makes good business sense. Modest changes promise to yield big benefits.

Jeff Anthony is manager of utility programs for the American Wind Energy Association.

This article was reprinted with permission from Utility Automation & Engineering T&D as part of the PennWell Corporation Renewable Energy World Network and may not be reproduced without express written permission from the publisher.