2012-01-12 / News

Turbine consultant releases initial wind-speed estimates

BY HARLEY LEE


The Portsmouth Abbey School machine was erected in 2006. The 240- foot turbine was Rhode Island’s first commercial-sized wind turbine. 
PHOTO COURTESY OF PORTSMOUTHABBEY.ORG The Portsmouth Abbey School machine was erected in 2006. The 240- foot turbine was Rhode Island’s first commercial-sized wind turbine. PHOTO COURTESY OF PORTSMOUTHABBEY.ORG One of the key elements of a wind project is to have a good understanding of the wind resource at the site of a proposed project. While wind turbines are operating successfully in Portsmouth and Newport, it helps to measure at a proposed site. That allows an accurate estimate of the output of a proposed turbine. This, in turn, allows accurate revenue and savings projections.

Jamestown hired a contractor to install a high-tech wind-measuring device out by the town garage last May. This device, called a sodar, emits a chirping sound, which is used to measure the winds all the way up to 200 meters (about 660 feet) above ground level.

We had a meteorologist take the data collected to date and perform a correlation analysis with wind measurements taken at a buoy near the Naval War College. Since there was a good correlation, we now have a reliable estimate of the long-term average wind speed to use in our projections. We also found that wind turbulence from the bridge is not an issue.

The estimated annual average wind speed is 6.26 meters per second – about 13.8 mph – at 67 meters (about 220 feet) above ground level. This is quite close to the wind speed reported in Portsmouth as well as close to the estimate from the earlier feasibility study. We picked 67 meters because that is the maximum tower height that will keep the tip of the blade under the Federal Aviation Administration maximum height of about 400 feet above sea level.

Using these wind data, our meteorologist estimated the output of various wind turbines using various tower heights. (Note: A kilowatt hour [kwh] is the amount of electrical energy consumed when 1,000 watts are used for one hour).

• The Vestas 660, with a hub height of 50 meters, has a 660 kw rating. Its estimated wind speed in meters per second is 5.78 (measured at the hub height), with a net kwh output of 1,052,000.

• The Gamesa G87 has a height of 67 meters, a 2,000 kw rating, a 6.26 wind speed and a 4,364,000 net kwh output.

• The GE 1.62 has a height of 100 meters, a 1,620 kw rating, a 7.03 wind speed and a net kwh output of 6,171,000.

To put the net kwh figure into perspective, the town of Jamestown uses about 2 million kwh a year. The Vestas turbine is the same model used at Portsmouth Abbey. The Gamesa G87 is slightly larger than the wind turbine used at the Portsmouth High School. I asked the meteorologist to include the GE machine out of curiosity as it has a tall tower and is optimized for lower wind speed sites.

Our next steps include photo simulations of a medium and a larger wind turbine including one the same size as the Vestas 660 and the G87. We will also prepare financial analyses of these two turbines. That will give the Town Council information on the cost savings available from these two sizes of turbines and the visual impacts. That will allow them to choose a size that will then be used to conduct electrical and other studies and get final estimates.

The author is president of Endless Energy Corporation, a consultant chosen by the Town Council in December to conduct studies necessary to determine the costs and potential profitability of a Jamestown wind turbine.

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