(Editor’s note: This report was provided by the city of Salem.)
In January and again in the spring, a sophisticated wind-measuring device will be sited on the roof of the South Essex Sewage District (SESD) plant on Fort Avenue. SESD treats domestic waste from five member communities: Salem, Beverly, Danvers, Marblehead and Peabody. This effort to collect wind speed and quality data is the second step in the city of Salem’s effort to locate a wind turbine.
The study is funded by grants from the Massachusetts Technology Collaborative (MTC), which is the commonwealth’s development agency for renewable energy. The wind-measuring device will be on loan from the UMASS Renewable Energy Research Lab (RERL).
The first step in this process, also paid for by MTC, reviewed nine locations within the city’s boundary (SESD, Winter Island, Forest River, Salem Willows, Salem High, Bertram Field, Salem Greens and the Bentley and Saltonstall Schools) to determine if any were candidates for a turbine. That evaluation revealed that SESD was one of the more promising locations. Now, in the second study, Salem needs to determine whether there is actually sufficient wind flow at that site.
The wind-measuring device, called a SODAR, is 6 feet by 6 feet and comes in several pieces that together weight from 150 to 200 pounds.
SODAR stands for SOnic Detection And Ranging. It works like sonar; sonar systems detect the presence and location of objects submerged in water by means of sonic waves reflected back to the source. Sodar systems are similar except the medium is air instead of water and reflection is due to sound being scattered by atmospheric turbulence.
Most sodar systems operate by issuing an acoustic pulse and then listening for the return signal for a short period of time. Generally, both the intensity and the frequency of the return signal are analyzed to determine the wind speed, wind direction, and turbulent character of the atmosphere. A profile of the atmosphere as a function of height can be obtained by analyzing the return signal at a series of times following the transmission of each pulse. Data will be collected at heights from 30 to 150 meters at 10-meter increments.
The pulse projected is sometimes referred to as a “chirp,” which the unit emits a few times a minute. The sound can be heard at distances of 300 to 350 meters. Visit this web location to hear a representation of the “chirp” sound www.sodar.com.
Data from the winter and spring SODAR runs will be analyzed by UMass’ RERL staff and forwarded in a report to city officials as the number of kilowatt hours per year that could be generated at the SESD site. Then it is up to Salem’s leaders to determine whether installing a turbine would be cost effective.
Should the numbers indicate a positive answer, Salem may be in line to qualify for a turbine from an unlikely source. Excelerate Energy, the company constructing the Northeast Gateway LNG offshore terminal 13 miles southeast of Gloucester, has ponied up considerable mitigation money to offset on and offshore impacts of its project. Among them is a $400,000 grant to the Massachusetts Energy Consumers Alliance.
In August, the Alliance announced it would use the money to donate a turbine to a coastal community. Winning the Alliances’s turbine would be a real boon for several reasons: turbines are expensive and, because they are much in demand worldwide, the devices are back ordered. Salem notified the Alliance of its interest in the turbine as soon as the opportunity was announced.
If Salem does not secure the alliance’s turbine, Mayor Kim Driscoll has stated that the city would apply for funds to purchase and install one through the MTC and search for a potential partner to assist with the costs.
29 December 2007
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