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Any way the wind blows....

Mon, 07/21/2014 - 9:14am
Joshua Israelsohn, Director, JAS Technical Media

When I hear or read the phrase wind power, I immediately imagine tall-towered machines with tri-blade impellers tracing out huge arcing sweeps against partly cloudy skies. Your imagery may vary.

Globally, wind generation capacity climbed to 318 GW in 2013 and has increased, year-over-year, an average of 37 MW since 2008 (Figure 1). The People’s Republic of China leads the world in terms of cumulative installed wind-generation capacity with 91.4 GW or almost 29% of the global total (Table 1).

Figure 1. Global wind-powered electricity-generating capacity in GW from 1996 through 2013. (source: GWEC)

Although the United States ranks second in cumulative installed capacity, it’s sixth in new capacity installed during calendar 2013 (Table 2). Several turbine manufacturers I’ve spoken with attribute the US’s lagging capacity build out, not to a lack of investment interest in wind power or to a shortage opportunities for wind-power technologies, but to a hostile permitting environment. The Cape Wind project exemplifies their concerns:

The Cape Wind project is the first offshore wind farm cited in the United States. It will operate 130 Siemens 3.6-MW turbines installed in a grid covering about 24 square miles. The project kicked off on November 15, 2001 with the submission of permit applications to 17 state and federal agencies. Three years later, the US Army Corps of Engineers issued a favorable draft Environmental Impact Statement – a short note of only 4,000 pages.

Table 1. Top ten countries for cumulative wind-powered electricity-generating capacity as of end of 2013. (source: GWEC)

In April 2006, members of the Alaskan (yes, I did say Alaskan) congressional delegation attempted to stop Cape Wind with an amendment to a Coast Guard bill. (For reference, Juneau is 2,948 miles from Martha’s Vineyard.) The amendment was stripped from the final legislation and I’ve yet to find anyone who can explain how a wind farm in Massachusetts affects anyone in Alaska.

Since then, Cape Wind has completed the permitting process, secured both financing and purchasing agreements with electric power distributors, and survived several legal challenges to the permitting process. A federal court decided the last of the legal challenges in the project’s favor just this past March. All told: 12 ½ years just to get permission to start construction.

Table 2. Top ten countries for new wind-powered electricity-generating capacity added during calendar 2013. (source: GWEC)

Thankfully, wind generation technologies scale… in both directions.

Up the coast, a quite modest wind generation facility started producing with a single 1.5-MW turbine in August of 2011. A second 2-MW machine came on line December of 2012. The combined output of the Ipswich Wind project supplies about 7% of the town’s electricity needs and serves to buffer ratepayers from price volatility.

Output data from the Ipswich Wind facility also reveals an interesting attribute of wind patterns, at least those enjoyed by the New England coast: Winter months are much windier than are summer months (figure 2). This pattern suggests hybrid wind/solar generating facilities in which the seasonal advantages of one energy source offset the seasonal deficits of the other. (For insight into the wind patterns in your area, periodically visit the nearly-real-time wind map at http://bit.ly/1q6Tm9O. Click to zoom in on regions of interest.)

Figure 2. Data from the Ipswich Wind installation reveals the seasonality of wind speed, which is a common characteristic of the New England coastline.

Horizontal-shaft wind generators nearly always suffer multi-year site-selection and permitting processes. Ipswich Wind’s process was comparatively quick with only eight years between the start of the site survey and the start of production. These turbines nearly always have a hub elevation of at least 80 m, and thus require FAA approval even in cases that don’t otherwise require Federal agency sign offs.

There are, however, small-scale vertical-shaft machines that invite one to look at wind generation from a different perspective. Horizontal-shaft generators are usually built to utility-power scale, providing capacities between a large fraction of a MW and 8 MW. They connect to a generic base load through distribution cables, mitigating the power demand serviced by traditionally fueled generators.

By contrast, manufacturers of small vertical-shaft generators usually size their products between single digit and several tens of kW—between one and three orders of magnitude smaller than the utility-class turbines. Vertical-shaft generating systems do not require steering mechanisms—they are always facing into the wind. Nor do they require blade-pitch adjustment, which greatly simplifies their mechanical design.

Customers often size and site these small generators for a specific load or installation. An early example is the 50 kW vertical-shaft generator from Eastern Wind Power. The 50 kW Sky Farm turbine uses a Siemens inverter to automatically synch with and connect to the local power grid. The turbine blades are only 20 feet high and the machine occupies a footprint of only 16 feet on edge. Multiple vertical-shaft wind turbines can share a site with only 16 foot spacings—useful for rooftop installations or ground-level applications with space restrictions.

Originally designed for permanent installations, this design has been adapted for portable applications including disaster relief, rural electrification micro-grids, rural communication ground stations, and military field operations (figure 3).

Figure 3. Eastern Wind Power adapted its 50 kW Sky Farm vertical-axis turbine to fit in and assemble out of a 20’ ISO shipping container. The container serves as the turbine’s foundation. (graphic courtesy Eastern Wind Power)

Smaller still, a hybrid wind / solar generator from Wing Power Energy supplies off-grid loads such as 4G LTE communication base stations (figure 4). The system also maintains the charge for a seven-day backup battery, which supplies power on still evenings and in case of multiple days of overcast skies.

Figure 4. Two of three hybrid wind / solar generators mounted on the roof of a Salem, MA parking garage provide power for a Verizon 4G LTE base station. The small footprint generators take less than two parking spaces each. (Photo courtesy JAS Technical Media)

The Wing Power Energy design can provide power in areas where utility service is unavailable. Communication companies, such as Verizon, can use these systems to fill in their coverage maps, particularly in rural locales.

Retailer Walgreens is using a pair of Wing Power Energy turbines with 850 solar panels and a geothermal system to power what the company asserts is the nation’s first net-zero-energy retail store, located in Evanston, IL.

A goal of Wing Power Energy’s blade design is to produce useful power at low wind speeds. The company claims a cut in speed of only 5 MPH making the system attractive in locations otherwise not well suited to wind energy capture.

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