As we head into another windy season in Buffalo (October to April), perhaps this is a good time to review what the wind resource is, and how it compares to other parts of the country. In general, there are a pair of publicly available wind resource measurements that have been taken in the same locations for a considerable length of time - the US Coast Guard (USCG) station at the mouth of the Buffalo River, and at the airport in Cheektowaga. For example, this year the airport winds have averaged 4.18 m/s, while the USCG has average 4.61 m/s (Sep 08 to Aug 09). There is also the modeled data at the NY State Wind Map which is useful for estimation, but is different than actual data. Finally, there is the data from the met tower at the Lackawanna Steelwinds wind farm of First Wind - but that is private, and not public. There are also data available from the National Data Climate Center, but a lot of that also costs money. Your tax dollars not at work...
Discussion
Here are 7 years worth of data summarized in one graph (August 2002 to July 2009) from the USCG:
This data is collected at a 10 meter height above the ground, and the location appears to be about 5 meters (15 feet) above the level of Lake Erie. The location is fairly well exposed to Lake Erie winds, and fairly shielded from onshore winds - especially those from the southeast to north, and somewhat from the north to the northwest. There is also the breakwall located about 1500 feet due west of the USCG station - itself 14 feet high. This is single point data - no real knowledge on the wind shear (change in wind speed with change in height above the ground/water surface) is readily derived. The big value of the data is that it shows the monthly variation, and there is also the yearly variation information.There is also 6 full year averages:
Year .............. m/s
2003 ............ 4.373
2004 ............ 4.378
2005 ............ 4.135
2006 ............ 4.506
2007 ............ 4.554
2008 ............ 4.661
Average ....... 4.435
The wind speed varies by -6.6% to +5.1% of the average at this site. Of course, this does not necessarily say what the wind speeds would be at an 80 meter height, where most commercial wind turbines operate.
Comparing this:
According to the NREL (National Renewable Energy Laboratory) website, this is a really lame wind site - a "Class 2" site, barely. For their standards, a decent wind site would need to be 5.6 m/s at a 10 meter height...for a site with a wind shear exponent of 1/7 (0.143), which is about the same as a roughness length (RL) of 0.023 meters. At 80 meters, a Class 4 site would average about 7.5 to 8 m/s at a site with a 1/7th wind shear exponent.
However, there was the NYSERDA wind study done in 2003 to 2004. At the site of the present Steelfield windfarm, wind speeds were measured at 7 m/s at 48.4 meters height, with a roughness length of 0.115 meters (about a wind speed exponent of 0.158). At 80 meters, the winds should average 7.6 m/s...and thus this is a Class 3 site. This is considered marginal by NREL standards, and not capable or barely capable of commercial wind derived electricity generation.... Another of the sites examined in this NYSERDA study was the NFTA property at 975 Fuhrman Blvd, where wind speeds of 7.4 m/s were MEASURED at 109 meters height above the ground.
This stands in contrast with what is a well known experience - it's windy by the Lake Erie coastline in the Buffalo region. And the investors in Steelwinds project poured about $45 million into their 20 MW wind farm, because they considered the location to have a commercially viable wind resource, coupled to a great grid connection point. So, maybe there is something wrong with the NREL standards...
Actually, there are places in the U.S. with such great wind resources - offshore in the Great Lakes, on the oceanic coastlines (Pacific, Atlantic, Gulf of Mexico (GOMEX) ) as well as offshore, and in much of the Great Plains, in some wind canyons, and on the down side on the Rockies (where air gets pushed up to high altitudes by prevailing westerly winds, cools significantly, and then falls "downhill" due to its higher density onto the flat Great Plains...). However, many of these great wind sites, such as the Lakota Sioux land in south-central South Dakota where winds average near 8.7 m/s at 80 meter heights, are located far away from "load centers", or in many cases, available transmission lines. As such, the wind energy is considered "stranded". Getting electricity from windy regions to populated regions can be quite expensive, and it may well be less expensive to use the local, but less windy resource rather than the remote but high quality source. Besides, geographic variety in sites leads to a very stable average electricity production, in effect, baseload power.
But back to the NREL standards...they are, apparently, outdated. And, there are a new set of wind turbines which are well tuned to moderate wind speeds which were not present when the NREL wind resource classification and guidelines were composed. Furthermore, the assumption of the smooth ground surface profile and hence low wind shear values is generally not warranted in areas with hills, buildings and trees - such as onshore in the Great Lakes/Northeast U.S. regions, where trees are ever present, and one of the dominant lifeforms. Here, wind shears are much greater than are present in the flat Great Plains, deserts and over water, which means that wind speeds at 10 meter heights will be much less than those present at 80 and 100 meter heights, and the 1/7 "Power Law" does not apply. Since the power that can be produced is proportional to the cube of the wind speed...a small difference in wind speed means a huge difference in power output. For example, at the Bethlehem Steel slag bluffs (Steelwinds), the 10 meter height wind speed would be 5.21 m/s, and would be expected to give only 80% of the energy output per year (power) that a barely Class 3 wind site (5.6 m/s) would produce. This is not the case - outputs at the 80 meter height are roughly equivalent at an ideal Class 3 site versus the Bethlehem Steel site - perhaps even greater at this Lackawanna location.
As one proceeds inland from Lake Erie, wind shears rise, and ground level wind speeds drop significantly. The effects are even seen at 80 and 100 meter heights, though the effect is not as pronounced. Thus, wind turbines that are "tailored" to the blazing fast wind resource of South Dakota (small rotor diameter to generator capacity ratio, relatively low hub height (center of rotor)) may not be appropriate for a region such as Western New York. In fact, the NREL has had a program called the Low Wind Speed Turbine (LWST) technology project since 2001. Unfortunately, there seems to be no great hurry in this (the funding never got rolling until 2002-2003 time frame, and this was quite sparse considering that over 50% of the continental US qualifies as "low wind speed").
However, in Europe, the Feed-in Laws, coupled with onshore wind resources often considered pathetic by North American standards, have provided an immense incentive to concentrate on this area of wind turbine technology. And even though there is minimal direct governmental funding, the ability to make a profit selling electricity from sites with 80 meter height wind speeds near 6 m/s has provided European wind turbine manufacturers with all the incentive they need - that is, they have a viable, unsubsidized market for such products. And unfortunately for the U.S., all the government R&D (and there really hasn't been that much, and what there is is often too late - scooped by the Europeans) cannot overcome the lack of a Feed-In Law and a stable market - despite the vastly superior wind resource of the U.S. The only European country with U.S. style laws (Great Britain) also has an awesome wind resource, and effectively no significant wind turbine manufacturing industry (= green jobs)...maybe there is a connection?
There are two main ways to overcome a "moderate" wind resource. One is to use a taller tower - wind speeds increase as the height above the ground (hub height) increases. The other is to use larger size rotors (blade length) with the same or smaller size generators. Quite often the longer blade lengths require taller towers, simply to keep the blades in decent wind regimes when they pass through the lower part of their rotation. For example, Enercon routinely uses 113 meter tall towers with its 82 meter rotor diameter x 2 MW wind turbine (E-82). The lack of a gear speed increaser (their turbines are "gearless") also helps by eliminating this slight energy loss (about 5% of a "geared" turbine's output is lost in the gearing). Finally, they have patented the use of "winglets" at the tips of their blades to add another 5% efficiency increase (at low wind speeds). Fuhrlaender offers a 160 meter lattice tower for their 2.5 MW wind turbine, and Nordex utilizes a "hybrid" tower of 120 meters with their units (the bottom 60 meters are concrete, the top 60 meters are steel). Finally, the new "mega" scale wind turbines (5 and 6 MW) feature rotor diameters of more than 120 meters, and hub heights of between 100 to 138 meters, allowing the blades to tap into the faster winds present at the 150 to 200 meter heights above the ground.
One example of the push to LWST can be seen with Vestas (not the only company interested in this new business). They offer a 3 MW "fast wind turbine (V90 x 3 MW) which actually has lower energy yields at moderate winds than their 1.65, 1.8 and 2 MW units. The key to their new business is longer blade lengths coupled to higher tower heights and smaller generators. For example, here is a summary of some of their products (Generator Ratio is defined as the ratio of swept rotor area (m^2) to generator rating (kw) - a higher number is better tuned to low wind speeds):
Model ...... Tower Height (m) ...... Rotor diameter (m) ...... Generator (MW) ...... Generator Ratio
V80 .......... 68, 80 ....................... 80 .................................. 1.8 ........................... 2.79 m^2/kw
V82 .......... 80 ............................. 82 .................................. 1.65 ......................... 3.20 m^2/kw
V90 a ....... 80 ............................. 90 .................................. 3.0 ........................... 2.12 m^2/kw
V90 b ...... 80 ............................. 90 ................................. 1.8 ........................... 3.53 m^2/kw
V100 ........ 95 ............................. 100 ................................ 1.8 ........................... 4.36 m^2/kw
V112 ......... 95, 110 ...................... 112 ................................. 3.0 ........................... 3.28 m^2/kw
Thus, the days of "one size fits all" wind turbines may be evolving into units customized for the wind resource. This could "free up" over half of the continental U.S. land area to commercial scale wind turbines at generated prices in the 8 to 15 c/kw-hr range (depends of financing loan terms, wind resource, proximity to transmission lines/electricity markets). And the result would be the end of ANY excuse not to power up this country (electrically speaking) with wind turbines COMPLETELY, and then some. The "then some" power (i.e. more than 400 GW (gigawatt) on a delivered basis) could be used to replace the natural gas now used for most heating applications, and to produce materials such as ammonia and liquid fuels via reduction of CO2 derived renewably with electrolytic hydrogen, obtained from water and wind turbine derived electricity.
DB
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