US power industry and wind get acquainted
by the CADDET US National Team

An innovative programme in the USA tests new wind turbines in challenging environments, ranging from locations north of the Arctic Circle in Alaska to remote prairies on the Southern Plains in Texas. Ten installations are operating, planned, or under construction. Their experience is reinforcing confidence in wind technology within the US power industry.

Ice on black blades.

Introduction

In 1999, electricity utilities in the USA are much more familiar with wind power than they were just seven years ago. At that time, only two US utilities purchased electricity directly from wind power plants, and none had experience of owning and operating the plants themselves. Today, the first utility-owned wind power plants are in operation, and additional installations are planned or under construction in 16 states.

 

Wind Turbine Verification Program locations.

 The Turbine Verification Program

Much of this change since 1992 can be traced to a collaborative project between the United States Department of Energy (US DOE), the Electric Power Research Institute (EPRI) of Palo Alto, California, and more than a dozen US power companies, called the US DOE-EPRI Wind Turbine Verification Program (TVP).

The objectives of the TVP are to:

  • verify the performance of new wind turbines in new areas;
  • gain experience with wind technology for electric utilities.

Under the programme, electricity utilities can participate in a cutting-edge wind project ­ using a new turbine design or operating turbines in a challenging climatic environment ­ without exposing their companies to excessive risk. The US DOE and EPRI provide some financial and technical support for the installations.

The utilities own (or partially own) and operate the wind power plants as they would any other plant in their generation systems. This means that they keep uniform statistics on performance and operations that meet utility specifications. For example, wind turbine availability is defined as total time ready for operation divided by the total hours in the measuring period, usually 8,760 hours/year ­ the same definition used for any type of power plant. These data are shared through the TVP and, because they summarise the experience of the participating utilities in terms that are familiar to them, help create confidence for future utility-sponsored wind power projects.

Technical accomplishments

Already the TVP is showing important technical results. For example, the operators of the first wind power plant constructed under the programme, which began operating in Fort Davis, Texas, in July 1996, had to learn about lightning. Located in south-west Texas, Fort Davis experiences frequent and violent thunderstorms in summer. As many as 300 lightning strikes/minute have been recorded within a 300 mile radius of the site.

During construction, lightning destroyed a generator before it was even put into operation. Even when the turbines were properly earthed, lightning knocked out motors and the communications links between the turbines and the control centre. Since then, the utility owner of the power plant, Central and South West Services Inc, working in conjunction with the US DOE's National Wind Technology Center in Golden, Colorado, has developed electronic lightning protection for the communications cables and has reinforced the earthing around the turbines. These improvements have significantly reduced equipment damage and downtime due to lightning.

The TVP's second project took on the challenge of cold weather operation. The plant located in the mountains of Vermont, New England, experiences major ice storms and cold, foggy, wet conditions in winter ­ not a turbine-friendly climate. For example, when the turbines were not operating, frost would often form on the inside of the turbine covers (nacelles). As it melted, water would fall on equipment, creating problems with corrosion. Adding heaters inside the nacelle eliminated this problem. Heaters were also added to cold-sensitive equipment, such as the control and hydraulic systems. Outside, ice would form on the surface of the blades during bad weather, changing the airfoils and sometimes preventing the turbines from turning. To solve the problem, the turbines were fitted with black blades that absorb solar energy to melt the ice and the blades were coated with Teflon™ so that snow and ice do not stick to them.

Associate TVP Projects

 Location

 Participating
utilities

 Plant
capacity
(MW)

 Turbine

 Turbine
rating
(kW)

 No. of
turbines

 Characteristics

 Glenmore,
Wisconsin

 Several
Wisconsin
utilities

 1.2

 Tacke
TW 600e
CWM

 600

 2

Designed to maximise electricity  output in low wind speed conditions

 Big Spring,
Texas

 TU Electric
Company

 34

 Vestas
V47-660
V66-1.65

 660 and
1,650

 42 and 4

The largesr turbines curently installed  in the USA

 Kotzebue,
Alaska

 Kotzebue,
Electric
Association

 0.66

 Atlantic
Orient
Corporation
AOC 15/50

 66

 10

Connected to 12.5 kV distribution  system. Augments diesel generation for a village

The installations

The Texas and Vermont projects already mentioned were the first wind power plants installed in the USA on the Great Plains and the eastern seaboard. The plants will operate for a period of three years.

The TVP has two other groups of projects under way, each involving different goals and hardware.

Distributed projects

Each of the distributed projects is smaller than the two original TVP projects, and is connected directly to utility distribution lines. This configuration is similar to many wind facilities in Europe where land is often scarce. This series of projects focuses on whether distributed clusters of wind turbines have a market in the USA. All types of US utilities are represented: investor-owned utilities; municipal utilities; and rural electricity co-operatives. Two of the plants are completing their first year of operation in 1999, and construction is expected to begin on two more during the year. The series includes a cold-weather turbine being tested in New York State for use in Alaska and, possibly, Antarctica.

Associate projects

For the original and distributed projects, funding is provided for turbine installation, start-up and acceptance testing, and collecting data. Associate TVP projects only receive funding from the programme for performance evaluation. Each of these projects involves turbines with different characteristics (see Table above).

Conclusion

As a result of the TVP, the US power industry's familiarity with wind power has grown, based on the increasing experience with projects and on support from its customers. By creating a utility database of operations and performance data for a variety of turbine designs, geographical locations and wind resource regimes, the TVP is laying the foundation for a long and fruitful relationship between US utilities and wind power.

For more information contact the CADDET US National Team at Golden, Colorado.

The CADDET Renewable Energy Newsletter is a quarterly magazine published by the CADDET Centre for Renewable Energy at ETSU, UK.

The articles published in the Newsletter reflect the opinions of the authors. They do not necessarily reflect the official view of CADDET.

Enquiries concerning the Newsletter should be addressed to Pauline Toole, Editor, CADDET Centre for Renewable Energy, ETSU, Harwell, Oxfordshire OX11 0RA, United Kingdom. Tel: +44 1235 432968, Fax: +44 1235 433595.