Understanding U.S. Wind Fleet Underperformance

By Jennifer Delony

There is growing concern within the wind industry about underperformance of the U.S. wind farm fleet in actual operations as compared to preconstruction estimates. A poor performance trend across the board is not good news for the financial community if investors do not receive a high enough return from their wind preoject investments. ...

Director of engineering for Albany, N.Y.-based meteorological consulting firm AWS Truewind Eric White's comments on underperformance in the U.S. set the stage for a two-part discussion at the American Wind Energy Association's annual conference about the realities of actual wind farm energy production compared to preconstruction forecasts. He reported an average 10% underperformance for the U.S. overall versus expected wind farm performance values ...

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Motor Oversizing Wastes Energy

Atlanta-based WEG Electric Motors Corp. Product Manager Andrew Glover explains that energy efficiency losses through oversizing of pump electric motors by engineers are commonplace, and if motor specification far exceeds the application, it could be costing the industry billions of dollars in wasted energy.

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New High-Capacity Transmission Needed to Industrialize Rural and Wild America

Grid Enhancements Needed In Maine

Despite slow development progress to date, plans for new transmission in Maine could open capacity for more than $1 billion in wind energy projects.

By Jeff Siegel

Equally as important, the state is located near the high-use ISO New England (ISO-NE) market, where peak demand can hit 30,000 MW. But the state does not use much electricity itself, with peak demand in northern Maine at just 140 MW ... Hence, it would seem to make good sense to build wind in Maine to sell to the New England grid. Traditionally, there has been a number of obstacles to this strategy.

First, part of Maine is not on the New England grid ...

Second, low peak demand means inadequate transmission capacity for adding enough wind to sell to the New England grid. ...

Another obstacle to this strategy is the state's pride in its unspoiled rural areas. The new legislation has made it easier to permit and build wind farms ...

Finally, Maine's sense of political and cultural independence could deter utility-scale development. It is one thing to build wind facilities to generate electricity in Maine, with the attendant environmental concerns that have caused controversy. But it is another issue entirely to site a turbine in a forest, disturbing wildlife and driving away tourists so that people in Boston will have electricity. These issues also could hinder the development of new transmission.

Maine Could Get New Transmission

The Maine Public Service Co. (MPS), a subsidiary of Maine & Maritime Corp., and Central Maine Power Co. (CMP) have announced plans to construct a 345 kV transmission line from central Maine to northern Aroostook County.

... a 200-mile, 345 kV transmission line and related substations from the Detroit area to northern Aroostook County ...

NorthWestern Energy Files [Major Facility Siting Application]

NorthWestern Energy proposes to construct, operate and maintain the approximately 400-mile, 500 kV transmission line ... The new transmission line is expected to run from a new substation near Townsend, Mont., to a substation near Midpoint, Idaho.

New Transmission Company Formed

Topeka, Kan.-based Westar Energy Inc. and Electric Transmission America (ETA) have formed Prairie Wind Transmission LLC, a joint venture company that plans to construct ultra-high-capacity transmission facilities.

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International Finance Corp. Updates Lender Guidelines

The guidelines reflect rising pressure being placed on companies worldwide to protect the environment and the health and safety of workers as well as people living near wind energy projects.

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U.S. Slow To Engage Condition Monitoring

The authors of an Electric Power Research Institute report titled "Condition Monitoring of Wind Turbines" note the following: "Enough examples of premature failures exist to shed considerable doubt on the likelihood of a turbine reaching the 20-year design life without replacing one or more of the drivetrain components; estimates of 15% of the initial turbine capital cost for replacement parts over the life of the project are not unreasonable. Continuing premature failure of planetary/helical gearboxes indicates a mean time between failures may be as low as four to five years, on the average across all manufacturers."

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Relocating the wind: New strategies for moving wind generation from high-wind areas to high-loa

by Marcus A. Wood and Jennifer H. Martin

The western U.S. has excellent wind-generation resources stretching over a vast expanse of the West and the Great Plains. The U.S. also has great pent-up demand for wind generation, particularly up and down the West Coast and in the Midwest. Exploitation of this vast wind-generation resource, available where the wind blows hardest and most steadily, is greatly hampered by a lack of economic long-distance transmission facilities and by multiple east-to-west and north-to-south firm transmission constraints found on existing transmission paths.

Any long-distance transmission of large amounts of electric generation presents electrical engineering challenges. Utility engineers routinely surmount such challenges in the construction of long-distance transmission systems for conventional electric generation systems. However, transportation of wind by wire must also accommodate special characteristics of wind generation. Briefly, these key special characteristics are:

1. Low capacity factor. Even in the most energetic wind areas, sites with generation capacity factors of 40 to 45 percent are considered premium sites. By comparison, large thermal generation units can achieve capacity factors in the 85 to 95 percent range. Long high-voltage transmission lines are very expensive, and the reduced capacity factors for wind generation translate to a roughly 2-to-1 cost transmission disadvantage for long hauls of wind-generation megawatt-hours.

2. Hourly forecasting difficulty. Despite continuing improvements in wind forecasting techniques, actual wind generation in each hour can vary substantially from forecast levels. Generally, the geographic areas with the best wind potential are not part of any organized regional transmission organization with centralized dispatch. Instead, each transmitting utility schedules out-of-region deliveries of wind generation based on forecasts and may impose substantial charges for deviations between forecast and actual generation.

3. Intra-hour swings in generation. Wind generation, even if produced over an hour on average in the amount forecast, may vary greatly within the hour. The within-hour output swings can be particularly noticeable as weather fronts pass through. Although the Federal Energy Regulatory Commission's (FERC) Open Access Transmission Tariff does not address the cost of such intra-hour variations, transmission providers are beginning to assess sometimes substantial new transmission ancillary service charges to cover the supposed cost of such generation swings.

As a result of these aspects of wind generation intermittency, the cost per megawatt-hour of relocating wind generation to other regions can be much higher than the cost of similarly relocating thermal generation. An even greater problem arises when control area operators maintain that they lack the generation flexibility required to provide the necessary hour-to-hour and within-hour shaping of the wind generation required for interregional deliveries. ...

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Evaluating Project Risks With Monte Carlo Analysis

by Ralph E. Evans

Local concerns

Quantifiable issues of local consequence frequently include acoustic noise (both construction and operational), visual impact, setbacks, bird and bat collisions, future decommissioning requirements and effects upon archeological, recreational and historical districts. ,,,

State concerns

At the state level, permits may be required from the public utility commission and, in some states, from an energy or environmental agency. Some states have monitoring requirements to ensure expected parameters are observed, such as noise, bird kill and icefall as represented in the local conditional use permit.

Federal concerns

The third level of permitting is represented by the federal agencies of primary jurisdiction, such as the EPA (wetland protection), the Federal Aviation Administration (FAA) (aircraft hazard), the U.S. military (interference to long-range radar) and the FCC (telecommunications interference to microwave, two-way, public safety and broadcast facilities). Telecom interference can be caused by aperture blockage (turbines turning through a microwave beam), by re-eadiation from turbine support towers, or by unintentional radio frequency radiation from generators or electrical combining equipment.

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Understanding Turbine Sound Impact Studies

by Kenneth H. Kalinski

Turbine sound levels

The two most important parameters related to noise impacts from wind turbines are sound power and tonality. Sound power, which has units of watts, is a measure of the acoustical energy emitted by a source. Sound power is distinct from sound pressure. Sound pressure is the perceived level of fluctuation of air pressure at a point in space. Sound pressure is measured in Pascals. Because of the large range of sound power and pressure, both are usually reported in decibels, and therefore, are often confused. And although sound power cannot be directly measured, it can be calculated using several methods, including the measurement of the sound pressure at a given distance. ...

Wind turbines['] ... sound level is highly dependent on meteorological conditions. In addition, wind turbines generate some low-frequency sound, which tends to propagate better than higher-frequency sound. ...

Note that although winds may be blowing where turbines are located, there may be little or no wind at ground level near the project neighbors. This is because the "roughness" of ground cover slows surface winds. This effect is amplified in more mountainous areas, where hills further reduce valley winds.

... Wind shear is the difference in wind speeds by elevation, and temperature lapse rate is the temperature gradient by elevation. Under conditions with high wind shear (large gradient), sound levels upwind from the source tend to decrease and sound levels downwind tend to increase. With temperature lapse, when ground surface temperatures are higher than those aloft, sound levels on the ground will decrease. The opposite is true when ground temperatures are lower than those aloft - an inversion condition. ...

Infrasound is sound pressure fluctuations at frequencies below about 20 Hz - sound below this frequency is generally not audible. At very high sound levels, infrasound can cause health effects and rattle lightweight building partitions. ...

Low-frequency sound is in the audible range of human hearing that is, above 20 Hz but below 100 Hz to 200 Hz, depending on the definition. As with infrasound, high levels of low-frequency sound (e.g., above 70 dB at 31.5 Hz) can rattle lightweight partitions in buildings. In addition, low-frequency sound that is well above background sound levels at higher volumes can be annoying.

Wind turbines generate low-frequency sound, primarily from the generator and mechanical components. ... Low-frequency sound can also be generated at higher wind speeds when the inflow air is very turbulent. ...

Low-frequency sound propagates better than higher-frequency sound and tends to diffract more in the atmosphere under inversion conditions. ...

Electric power substation noise should also be considered, especially if transformers are located near residences.

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Industry Defends Billion-Dollar CREZ Estimates

by Jennifer Delony

Costs for CREZ transmission have raised concerns about the high price to introduce more wind energy to the ERCOT system.

The scenarios for wind energy integration outlined in ERCOT's report "CREZ Transmission Optimization Study" are provided in megawatts, making extrapolation of cost savings dependent on establishing the average MWh output for every 1 MW in a scenario. The report does not provide an assumption for this figure or estimate annual fuel-cost savings.

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NY Releases Study Guidelines

In January 2008, the New York State Department of Environmental Conservation (NYSDEC) released its "Draft Guidelines for Conducting Bird and Bat Studies at Commercial Wind Energy Projects." The draft guidelines outline the NYSDEC-proposed protocols for conducting pre-construction and post-construction studies at onshore wind energy projects in New York. The purpose of the protocols is to formalize the methods by which bird and bat resources are characterized, and the impacts resulting from construction and operation of wind projects in New York are estimated and documented. ...

Based on a number of factors, NYSDEC would recommend either "standard" or "expanded" protocols to assess potential impacts. ... Sites specifically identified as requiring an expanded protocol include the following:

• sites with habitat for listed bird or bat species,

• sites within five mites of the Atlantic coastline or the shoreline of one of the Great Lakes,

• sites located within a concentration area of raptors, waterfowl, or other vulnerable species or within two miles of such a concentration area, or within 10 miles of a major bat hibernaculum, and

• sites on which there is a specifically identified habitat or landscape feature (e.g., ridgeline) that functions to funnel or concentrate birds/bats during migration or for feeding, breeding, wintering or roosting activities.

Pre-construction studies for a standard site include breeding bird surveys, habitat surveys, raptor and songbird migration studies, and acoustical monitoring for bats. Radar studies are not currently included in the standard pre-construction protocol despite NYSDEC'S insistence that these studies be conducted at nearly all proposed sites over the past few years.

Pre-construction monitoring for a site requiring expanded studies could include:

• radar studies, waterfowl or wintering bird surveys,

• additional raptor migration or breeding bird studies, and

• studies specifically for the 1n- diana bat (Myotis somalia, a federally endangered species) or other migratory bats, in addition to the studies associated with a standard site.

Standard protocol post-construction studies include ground searches, searcher efficiency and carcass removal trials, bird habituation and avoidance studies, raptor migration surveys, acoustical monitoring for bats and bat specimen collection. Expanded post-construction protocols also could include radar studies and additional raptor migration surveys. For all projects, NYSDEC would require that samples of bat carcasses be provided for a nationwide genetic isotope analysis project. ...

The standard protocol requires one year of pre-construction monitoring. If an expanded protocol is deemed necessary, pre-construction monitoring would be lengthened to two or three years, significantly lengthening the period between the start of fieldwork and project permitting. Post-construction monitoring would be conducted for three years under both the standard and the expanded protocol.

-- Christine Sousa & Mike Morgante

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