A 13-square-mile tract of ocean one to three miles off the south shore of Block Island is a prime candidate as a site for a 56-turbine wind farm, a state study concludes. Other candidates include ocean areas east and west of the Block Island ferry navigation channel not far from the mainland shore.
In all, the 132-page RIWINDS report issued last week identifies 11 sites where consultants believe the generation of electricity by wind would be feasible and economically competitive. Ten of the sites are off-shore; one is onshore, in Little Compton.
The site south of Block Island is entirely in state waters, as are all the other potential sites except one. That site, also about 13 square miles, lies about midway between Block Island and Montauk Point and is in federal waters. Establishing a wind farm there would require an additional level of permitting.
The two Block Island sites in state water, the farthest out to sea of the 11, have the advantage of the highest winds and consequently the lowest production costs of any of the sites identified, the study says.
The other potential offshore wind farm sites are an area south of Point Judith between the navigation lanes into Galilee and Narragansett Bay, two tracts off South Kingstown and Charlestown, one off Westerly and three off Newport and Little Compton.
15 percent goal
The study is a step toward meeting the state goal of reaping 15 percent of its electricity from the wind, part of the RIWINDS initiative announced by Gov. Donald Carcieri in January 2006. To help decide how to proceed with wind-farm decisions, Gov. Carcieri is assembling a task force of about 40 representatives of industry, environmental groups and communities.
“I signed the invitations today and yes, one is going to Block Island,” said Andrew Dzykewicz, commissioner of the state Office of Energy Resources, this week. “We’ll let the people of Rhode Island do what they want to do with this information.”
Carcieri commissioned the study last year. It cost $380,000 and was paid for with money from a monthly surcharge on electricity ratepayers plus a grant from Florida Power and Light, a major windfarm advocate.
The consulting firms that produced the document seemed to have pursued every conceivable angle, from 20 years of wind data to the cost of interest to the location of eel grass beds. The study is larded with both engineering and financing details.
But in the end, the study concludes, “Public acceptance of the offshore wind projects is critical “¦ public perception of these projects is difficult to predict.”
First Warden Kim Gaffett had no hesitancy about predicting. “I think wind farms would be acceptable to many people; they certainly are to me. I believe there’s been a shift of perception – we’re getting used to the idea and understand the need.”
The criteria used to eliminate most of the state’s land and sea and finally identify the potentially useful sites included wind speed, environmental sensitivity, navigation and cable lanes, air traffic, and water depth. The wind-speed data was derived from records of the National Oceanic and Atmospheric Administration monitoring station in Buzzard’s Bay.
Only waters between eight feet and 75 feet were considered – eight feet being minimum draft to accommodate the barges and boats used in constructing the towers and 75 feet being the limit of current construction technology.
The analysis was built around a large General Electric turbine now in common use in Europe, although larger machines are being developed. The hubs of the turbines would be 80 meters (about 260 feet) in the air. The data indicates that wind power at that height is considerably greater than at lower heights, but the gain in power at 100 meters is negligible.
To support the huge turbines, pilings 16 feet in diameter, with two-inch walls, would be driven as deep as 90 feet into the oceanbottom sand.
The consultants envisioned 56 turbines on five of the larger sites, including the two south and west of Block Island. They envisioned nine turbines for several of the areas closer to shore, including the one off Point Judith, and seven for the Little Compton site. Any two of the sites would provide space for enough turbines to meet the state’s 15 percent goal, Dzykewicz said.
Three different financing scenarios are sketched out in the study.
No surprise about wind
What sets the Block Island sites apart is wind speed. It averages around 9.25 meters per second (about 20.7 miles per hour) south of the island, while the areas closer to shore have average winds of 8.25 meters or 7.75 meters per second (18.4 mph and 17.3 mph, respectively).
As a consequence, the analysts believe electricity can be made most economically on the Block Island sites, despite the long cable run to the mainland. “The higher level of sustainable power is certainly significant,” said Dzykewicz.
The estimate of the price of producing power at those sites is $96 a megawatt, which the consultants believe would be little below predicted market rates. The price of generation at two other sites is a dollar more, and it runs on up.
The analysts point out that wind power costs are likely to be stable because there is no fuel cost, whereas the cost of coal and oil to produce power is variable and often unstable.
They also point out that the electricity transmission system in Rhode Island is “insufficient” to distribute power from large offshore wind farms. One of the most expensive features would be the cost of running cable inland to connect to high voltage transmission lines.
By Read Kingsbury
28 April 2007
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