Strong Wind Uncovers Weaknesses - Wind energy installations grew at a record pace in 2005. With the extension of production tax credits, the wind industry is in a boom cycle. However, challenges still buffet the industry.

The U.S. wind energy industry easily broke earlier records during 2005 by installing more than 2,400 MW-at a value of more than $3 billion-of new generating equipment in 22 states, according the American Wind Energy Association (AWEA). AWEA reported that the 2,431 MW of new wind capacity installed in 2005 boosted the cumulative U.S. installed wind power fleet by more than 35 percent, bringing the industry’s total generating capacity to 9,149 MW. An increasing demand by electricity consumers for clean renewable generating technologies, growing pressure on power producers to reduce CO2 emissions, increasing fossil fuel costs, renewable energy portfolio standards in many states and the extension of Federal Production Tax Credits (PTCs), which were part of the Energy Policy Act of 2005, all played a part in wind energy’s record-breaking year.

“Wind is likely to lead the market in investment and new installations over the next 10 years,” said Richard Germain, Associate Director with Navigant Consulting.

To continue its rapid growth, wind energy must overcome some major hurdles in the next few years. Market development in the United States is strongly dependent on the federal PTCs, which for now must be periodically renewed by Congress. The uncertainty surrounding when and if PTCs will be extended creates significant volatility in annual installations. Existing PTCs, which were scheduled to expire on December 31, 2005 but were extended to December 31, 2007 by the Energy Policy Act, provide a 1.9 cent per kWh tax credit for electricity generated with wind turbines. These PTCs continue over the first 10 years of a project’s operations and also contain annual inflation adjustment provisions.

That 1.9 cent tax credit can comprise up to one-third of a project’s revenues, said Lisa Frantzis, a director with Navigant’s renewable energy consulting practice. The current start-stop federal policy regarding tax credits has a major effect on wind project development. That, in turn, has a major effect on U.S. renewable energy development as a whole. Wind projects at present make up around 80 percent of all new renewable energy projects.

With PTCs extended through 2007, the wind industry is booming. A potential downside exists, however. The boom, and to some degree rising steel costs, have created market constraints that are causing wind energy facilities’ construction costs to rise. Most available wind turbine manufacturing capacity is booked until 2008. And according to Jeff Sterba, Public Service New Mexico’s (PSNM’s) CEO, costs have risen by more than 60 percent in the past three and a half years. “There is growing concern on Capitol Hill about extending PTCs on equipment that is increasing in costs when that cost increase can’t be tied to input cost,” said Sterba, who spoke at the recent POWER-GEN Renewable Energy and Fuels Conference Keynote Session.

Sterba said that most of PSNM’s renewable capacity, which accounts for almost 10 percent of the company’s total generating capacity, comes from wind energy. PSNM owns and operates the world’s third-largest nonregulated wind farm. Sterba told conference attendees that PSNM built the wind farm not because it was the most economical source of capacity, but because it was what customers wanted. Sterba discussed the most important factors that utilities consider when determining where to invest their generating dollars. Those factors include customer preferences, cost, price stability, environmental performance, resource reliability and dispatchability, and cost recovery. “Costs are critical and renewable technologies are still more expensive than coal and nuclear,” Sterba said. As Table 1 illustrates, even with federal PTCs, wind energy still ranks third.

“Renewable energy technologies must become more efficient to compete. They must be able to produce electricity at 4.5 cents per kWh,” Sterba said. He believes renewable energy must also be able to compete without relying on PTCs. Regional markets are the logical way to make this happen, he said. “Creation of regional markets is one of renewable energy’s biggest challenges,” Sterba told the audience. “The industry must find a way to create robust markets with the best technology for the region, not with the technology that is most politically advantageous at the time,” he added.

Wind Turbine Verification

Improving wind energy’s performance and increasing its competitiveness have long been the subject of R&D efforts. In 1992, the Electric Power Research Institute (EPRI) and the U.S. Department of Energy (DOE) initiated the Utility Wind Turbine Performance Verification Program (TVP). Specifically, the program was created to provide a bridge between development and commercial sales of advanced turbines, allow utilities to gain experience with the purchase and operation of wind power plants, obtain field performance verification of prototype state-of-the-art wind turbines and communicate the experience to other members of the utility and wind community.

Dr. Charles McGowin, an EPRI senior project manager, also spoke at the 2006 POWER-GEN Renewable Energy and Fuels conference. He presented a paper, “DOE-EPRI Wind Turbine Verification Program: 10 Years of Field Utility Wind Experience and Future Plans,” that addressed the objectives and scope of the DOE-EPRI TVP Program and the lessons learned during the TVP’s first 10 years, from 1995 to 2004. Over that period, the program supported eight wind turbine verification projects, including two TVP projects in Texas and Vermont, two distributed wind generation projects in Iowa and Nebraska, and four Associate TVP projects in Wisconsin, Alaska, Texas and Tennessee. According to McGowin, the TVP projects represent a broad range of turbine designs, sizes, wind resources, soil, humidity, ambient temperatures, lightning and other site conditions. In addition to the eight wind projects, the TVP Program supported a wind energy forecasting application at a ninth wind project in Texas, and the formation of technology transfer and outreach organizations (National Wind Coordinating Committee and TVP outreach workshops).

DOE-EPRI recently added the Arklow Offshore Wind Project in Ireland to the TVP Project. That project, which begins this year and is slated to last 30 months, will document development and operating experience of GE’s 3.6 MW offshore turbines.

Big Wind at Big Springs

The Big Springs Wind Power Project in Big Springs, Texas, is the largest TVP project, with a total generating capacity of 34.32 MW, as well as the program’s longest-monitored project. It consists of 34 Vestas V47-660 kW wind turbines and four Vestas V66-1.65 MW wind turbines. The project was evaluated from September 2001 through February 2004. McGowin talked about the performance and O&M experiences at the project from 1999 to 2004 and reviewed the lessons learned.

The Big Springs Wind Power Plant began as a commercial project developed and owned by York Research Corp. Under a 15-year power purchase agreement, Big Springs supplies power to TXU Energy. Construction began in July 1998 and the facility was commissioned in May 1999. In 2003, York sold the project to Texas Big Spring L.P., a unit of Caithness Energy. The project became part of the DOE-EPRI TVP as an associate project in 1999. At that time, a supervisory control and data acquisition (SCADA) system was installed to collect wind and turbine performance data. The project evaluation covers all of operating years three and four and the first half of operating year five.

During the project life, the average wind speeds were 7.9 meters per second (m/s) or 17.7 mph at 65 meters (213 feet, the V47’s height) and 8.4 m/s or 18.8 mph at 80 meters (262 feet, the V66’s height). As Table 2 illustrates, April has the highest average wind speeds; September the lowest. The 42 V47s produced 365 GWh of electricity, 84 percent of the project’s energy. The four V66s produced 68 GWh, bringing the project’s total output to 433 GWh. The V47s had an average availability of 93 percent while the V66s were available 80 percent of the time. The project’s total availability was 92 percent with a capacity factor of 32 percent.

The facility’s 92 percent availability factor equates to 145,000 hours of downtime - 3,160 hours of downtime per turbine. According to McGowin, the largest contributors to downtime were gearbox bearing failures, with generator bearings and windings coming in second. During the project life, 22 gearbox bearing failures occurred in the V47s. The bearings were replaced in 18 of these incidents, one gearbox was rebuilt and three gearboxes were replaced. The V66s experienced three gearbox failures. Two were repaired and one was replaced. Two other V66 gearboxes were replaced for unknown problems.

Other failures that occurred included 10 generator bearings or generator windings in the V47s. All 10 were repaired. In the V66s, seven generators failed due to bearing failure or bad windings. Two were repaired and five were replaced. All V66 repairs and replacements occurred under warranty.

Weather (wind), crane availability and equipment procurement had a big impact on downtime during failure repairs. York’s financial difficulties made it hard to obtain parts when needed, as well as maintain the proper spare parts inventory. The delay in obtaining parts increased downtime significantly. Project data reveals that while wind or crane scheduling can delay a repair up to two weeks, a lack of parts can delay a repair for a month or more.

Thus, Big Springs adopted an O&M strategy that includes closely monitoring the turbine through monthly oil sampling and quarterly SWANTECH (stress wave analysis) testing. The plant also implemented a spare parts program to ensure spare parts inventory is, and will continue to be, maintained. The spare parts inventory includes a V47 gearbox and generator.

Lessons Learned

The TVP tracked Big Springs during both warranty and post-warranty operation. There were a few rough spots during the transition of O&M responsibilities from the original equipment manufacturer (OEM) to site staff. Following are a few issues that surfaced:

Parts and Suppliers. Lack of spare parts can substantially increase downtime and lost revenue. Because OEM parts are often more expensive and many wind turbine components are standard, cheaper parts can be obtained from competitors. Therefore, before the warranty expires, personnel should create not only a spare parts list, but also a supplier list for those spare parts.

Spare Parts. The lack of spare parts contributed greatly to turbine downtime, therefore a fully-stocked spare parts inventory is a necessity. When Big Spring’s parts were available, downtime was reduced to a fraction of what it would have been if the parts had to be ordered and shipped.

Monitoring. Tracking parts consumption and retrofits can uncover patterns that can be used to schedule routine maintenance. In addition, condition monitoring should begin as soon as the facility becomes commercial. Oil sampling and analysis should be conducted routinely and the analytical results should be reviewed to find trends in the data.

Documentation. Manuals and service bulletins must be kept current. Copies of service reports should be maintained. It is important to document the operating conditions at the time a failure occurred. Documenting failures can help personnel better understand the underlying causes of failures.

Staff Capabilities. The warranty period should be used to train field technicians on O&M procedures and to give them hands-on practice to help ensure a smooth transition from the warranty period.

Although these tips were developed based on specifics from the Big Spring Wind Power Plant TVP, they can apply to almost any commercial wind project. In addition to the preceding issues and tips, McGowin shared a list of lessons learned, which were discovered based on experiences at all the TVP sites. They are:

    * Conduct thorough site characterization that includes: wind resource assessment such as ambient temperature, pressure, humidity and precipitation; lightning, hail, winter icing and dust storms; soil resistivity and groundwater level.
    * Tailor wind turbine specs to site conditions.
    * Ensure good grounding, shielding and blade conductors are installed.
    * Address expectations in procurement and warranty agreements.
    * Involve O&M crews in project installation and startup.
    * Seek public support early and proactively.

Pictured here are several Vestas V47 turbines: 660 kW; 390 volt; 65 meter tower; 47 meter rotor diameter. Photo courtesy of National Renewable Energy Laboratory.

McGowin also stressed that as many years of site assessment as possible should be obtained before siting a wind facility. “We discovered that weather and climate conditions can vary widely from year-to-year,” he said.

More information about Big Springs Wind Power Project TVP, as well as the other TVP projects is available at https://www.epri.com. (Type TVP Wind Power Projects in the Search Box.)