The C3—an alternative anemometer for resource assessment


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Executive Summary.
Second Wind Inc. is pleased to offer a new standard anemometer for resource assessment that incorporates industry proven geometry and features. The new three-cup anemometer, the Second Wind Model C3, is physically similar to a popular anemometer designed by Maximum, Inc. and used in the wind industry for more than 30 years. However, the C3 employs more durable materials with high-quality manufacturing methods that make it an extremely reliable alternative for wind assessment.

Key benefits include:

  • A second source for the industry’s most popular anemometer design. This provides a new choice for customers.
  • Choice of calibrated or uncalibrated units.
  • Confirmation from wind tunnel tests that there is no appreciable difference in wind speed or energy measurement between the Second Wind-manufactured C3 and the Max/NRG# 40 manufactured by NRG Systems Inc.
  • Indications of slightly less product variability than the Max/NRG#40, which was previously sold by
  • Second Wind, based on the same wind-tunnel tests involving hundreds of units.
  • Confirmation that the C3’s field performance is virtually identical to the many thousands of similar units employed in the wind industry, based on data from hundreds of C3 prototypes in active use.
  • The use of tough polycarbonate and single-piece construction for all molded plastic, in place of lessdurable ABS employed in Second Wind’s previous anemometer offering.

This paper provides background on the anemometer’s development, then describes the testing of the C3 and presents the results.

Background on Second Wind’s Anemometer Offerings
In 1980, Second Wind Inc. (SWI) designed a new system (the AL-2000) for wind resource assessment. Then as now such systems need wind speed and direction sensors. After an exhaustive search we selected the wind speed sensor designed and manufactured by Maximum, Inc., then of Natick, Massachusetts. The selection followed a design review at the Maximum factory with Mr. Gordon White, inventor of the anemometer. In addition, Second Wind tested several Model 40 cups in the wind tunnel at the University of Massachusetts at Amherst. We found them to be well suited to the field of wind resource assessment.

For many years Second Wind supplied these cups and, starting in 1993, offered a version calibrated in Massachusetts Institute of Technology’s Wright Brothers wind tunnel. The calibration method and equipment were designed by a team including SWI President Walter Sass, MIT Professor Eugene E. Covert1, and Wright Brothers tunnel operator Frank Durgin. By this time Maximum, Inc. had appointed NRG Systems of Hinesburg, Vermont (“NRG”) the sole distributor of the sensor to the wind energy industry.

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