Turbines

Importer: DC Power Systems • 800-967-6917 ■ www.dcpower-systems.com

Kestrel 800

Rotor diameter: 7 feet (2.1 m) Swept area: 38.5 square feet (3.6 m2) Rated rpm: 1,000

ds: 75 KWH per

Predicted energy output at average wind speeds: 40 KWH per month at 8 mph; 80 at 10 mph; 125 at 12 mph Application: Batteryless grid-tie or 12, 24, 48 VDC battery charging

Price (MSRP): $1,995 without controller or inverter Warranty: 5 years

Kestrel 1000

Rotor diameter: 10 feet (3 m Swept area: 79 square feet (7. Rated rpm: 650

Predicted energy output at ave month at 8 mph; 130 at 10 mph; 210 at 12 mph Application: 12, 24, 48 VDC battery charging Price (MSRP): $2,950 without controller or inverter Warranty: 5 years

Kestrel 3000

Rotor diameter: 12.5 feet (3.8 m) Swept area: 120 square feet (11.2 m2) Rated rpm: 500

Predicted energy output at average wind speeds: 130 KWH per month at 8 mph; 230 at 10 mph; 375 at 12 mph Application: Batteryless grid-tie or 48 VDC battery charging Price (MSRP): $8,400 with controller and dump load, without inverter

Warranty: 5 years

Eoltec 6 KW

Kestrel 800

Kestrel 1000

Kestrel 3000

Understanding the Ratings

Wind turbine rating is a tricky affair. While solar-electric module or microhydro-electric turbine production can be predicted fairly realistically based on rated output, this number is very misleading with wind turbines. Why? Because rated output is pegged to a particular wind speed, and different manufacturers use different wind speeds to determine rated output. Also, the power available in the wind varies with the cube of its speed, so small increases in wind speed result in large increases in power available to the rotor. A 10 percent increase in wind speed yields a 33 percent increase in power available in the wind. Conversely, this means that a turbine rated at 1,000 watts at 28 mph might produce only 125 watts or less at half that wind speed, 14 mph.

So what's a wind turbine buyer to do? Ignore the peak output and the power curve. Look for the monthly or annual energy numbers for the turbine, estimated for the average wind speed you expect or measure at your site. These will be given in KWH per month (or year) in the manufacturer's specifications for each turbine. Energy is what you're after, not peak power! If, for example, you are looking for a turbine that can produce 300 KWH per month, and you know that you have a 10 mph average wind speed at the proposed turbine height, you can shop for a turbine that is predicted to generate that much energy in that average wind speed.

If you can't get energy production estimates from the manufacturer or a turbine owner, look for a different manufacturer. This is basic information that any manufacturer should supply. However, knowing a turbine's swept area may also help you calculate the annual energy output for the wind turbine. All other things being equal, "there's no replacement for displacement." Hugh Piggott gives a rough formula for calculating output based on average wind speed and swept area in his HP102 article (see Access). Jim Green at the National Renewable Energy Lab (NREL) developed a similar formula: annual energy output (AEO) in KWH = 0.01328 x rotor diameter (ft.) squared x average wind speed (mph) cubed.

Prouen Energy

Importers:

Lake Michigan Wind & Sun • 920-743-0456 • www.windandsun.com Solar Wind Works • 877-682-4503 • www.solarwindworks.com

Proven WT 0.6

Rotor diameter: 8.4 feet (2.6 i Swept area: 55 square feet (5. Rated rpm: 500

Predicted energy output at average wind speeds: 42 KWH per month at 8 mph; 83 at 10 mph; 124 at 12 mph Application: Batteryless grid-tie; 12, 24, 48 VDC battery charging Price (MSRP): $4,870 without controller or inverter Warranty: 2 years; extended warranty available

Proven WT 2.5

Rotor diameter: 11.1 feet (3.4 m) Swept area: 97 square feet (9 m2) Rated rpm: 300

Predicted energy output at average wind speeds: 167 KWH per month at 8 mph; 293 at 10 mph; 417 at 12 mph Application: Batteryless grid-tie; 24, 48 VDC battery charging Price (MSRP): $9,650 without controller or inverter Warranty: 2 years; extended warranty available

Proven WT 6

Rotor diameter: 18 feet (5.5 m) Swept area: 254 square feet I Rated rpm: 200

Predicted energy output at average wind speeds: 417 KWH per month at 8 mph; 667 at 10 mph; 1,083 at 12 mph Application: Batteryless grid-tie or 48 VDC battery charging Price (MSRP): $20,500 without controller or inverter Warranty: 2 years; extended warranty available

Proven WT 15

Rotor diameter: 29.5 feet (9 m) Swept area: 683 square feet (63.5 m2) Rated rpm: 15C

Predicted energy output at average wind speeds: 777 KWH per month at 8 mph; 1,451 at 10 mph; 3,080 at 12 mph Application: Batteryless grid-tie or 48 VDC battery charging Price (MSRP): $39,340 without controller or inverter Warranty: 2 years; extended warranty available

Proven WT 6

Other Considerations

A turbine's revolutions per minute (rpm) at its rated wind speed can give you some idea of the relative aerodynamic sound of the machine, and also speaks to longevity. Slower-turning wind turbines tend to be quieter and last longer. High rpm machines wear out components, such as bearings, much faster. In addition, the faster blades move through the air, the greater the possibility that they will waste some of that energy as sound from the blades.

Some manufacturers make only battery-charging machines, and may offer a variety of turbine voltages. Others produce machines intended to connect to grid-synchronous inverters without batteries. One machine even includes an inverter integrated with the turbine itself. Make sure you're buying a machine that is appropriate for your intended use.

Make Your Choice

Trying to keep an inexpensive wind generator running can be an uphill battle that you'll soon tire of. But expect to pay more for a better machine—it's a tough job to design and manufacture a long-lasting, small-scale wind generator.

The bottom line: Buy a turbine that has a very good track record and a good warranty—five years is preferable but not always available in the small wind industry. A warranty is one indication of the manufacturer's confidence in their product, and their intention to stand behind it.

Real-world reports from users carry even more weight than a warranty, so search for people who own the model of turbine you're considering buying, and get the straight scoop from them about performance, durability, reliability, and maintenance issues.

Note that a number of the wind turbines listed here are relatively new introductions with not very much customer run-time in North America. These turbines include the ARE, Eoltec, Kestrel, and Skystream. We recommend that you contact either your local wind turbine installer, or the manufacturers or importers and find out how many of these machines are actually operating in North

Southwest UJindpoujer

Manufacturer: 928-779-9463 • www.windenergy.com

H per

H per

Whisper 100

Rotor diameter: 7 feet (2.1 m) Swept area: 38.5 square feet (3.6 m2) Rated rpm: 1,200

Predicted energy output at average wind speeds: 30

month at 8 mph; 65 at 10 mph; 100 at 12 mph Application: 12, 24, 36, 48 VDC battery charging Price (MSRP): $2,475 with controller Warranty: 5 years

Whisper 200

Rotor diameter: 9 feet (2.7 m) Swept area: 63.5 square feet (5.9 m2) Rated rpm: 1,100

Predicted energy output at average wind speeds: 60 KWH per month at 8 mph; 125 at 10 mph; 190 at 12 mph Application: 12, 24, 36, 48 VDC battery charging Price (MSRP): $2,995 with controller Warranty: 5 years

Skystream 3.7

Rotor diameter: 12 feet ( Swept area: 113 square 1 Rated rpm: 325

Predicted energy output at average wind speeds: 100 KWH per month at 8 mph; 240 at 10 mph; 380 at 12 mph Application: Batteryless grid-tie, or battery charging through battery-based inverter (not included) AC input Price (MSRP): $5,400, including turbine-integrated batteryless inverter

Warranty: 5 years

Whisper 500

Rotor diameter: 15 feet (4.6 m) Swept area: 176 square feet (16.4 m2) Rated rpm: 800

Predicted energy output at average wind speeds: 170 KWH per month at 8 mph; 330 at 10 mph; 538 at 12 mph Application: Batteryless grid-tie; 24, 32, 48 VDC battery charging Price (MSRP): $7,675 for battery charging with controller; $12,125 for grid tied with inverter Warranty: 5 years

Whisper 100

Whisper 200

Skystream 3.7

Whisper 500

America. Then contact the owners, and inquire about their experience and satisfaction with both the machine and the manufacturer or importer.

When you look at prices, keep in mind that just buying a wind turbine will not get you any wind-generated electricity. You'll also need most or all of the components mentioned earlier. Also budget for equipment rental, like a backhoe and crane, concrete and rebar, electrical components, shipping, and sales tax. Unless you do all of the work yourself, also factor in installation labor expenses. These costs can add up significantly, so make sure that you research and understand all of the associated expenses before committing to a purchase. Many people are quite surprised to learn that the wind turbine cost can range from only 10 percent to as much as 40 percent of the entire wind system's expenses.

Small-scale wind energy is not for the half-hearted, uninvolved, or uncommitted, and probably not for folks who never change the oil in their vehicles (or are willing to spend the bucks to hire someone to do the tower work). The

North American landscape is littered with failed installations: Designs not fully thought-out or tested, machines bought because they were cheap, and installations that required more time and money for repairs than they ever yielded in electricity generated. Many of the failures were the result of wishful thinking and too little research. That said, there are tens of thousands of happy wind-electric system owners. These owners did their homework—purchasing, designing, and installing rugged and well-thought-out systems on adequately sized towers. In addition, they are either committed to maintaining the systems, or to hiring someone to do this regular work.

While many first-time wind turbine buyers may be looking for a bargain, second-time wind turbine buyers are seeking the most rugged machine they can afford. You can avoid a painful "learning experience" by focusing on durability, production, warranty, and track record, and not on price alone, or on peak output. You don't want to depend on the low bidder for something as important to you as your long-term energy investment.

Rebuilders:

Energy Maintenance Service LLC • 605-272-5398 • www.energyms.com

Halus Power Systems • 510-780-0591 • www.halus.com

Vestas V-15

Rotor diameter: 50 feet (15 m) Swept area: 1,964 square feet (182 m2) Rated rpm: 53

Predicted energy output at average wind speeds: N/A at 8 mph; 3,354 KWH per month at 10 mph; 5,371 at Application: Batteryless grid-tie Price (MSRP): $140,000 installed on 110-foot tower Warranty: 1 year; extended warranties available

Vestas V-17

Rotor diameter: 56 feet (17 m) Swept area: 2,462 square feet (229 m2) Rated rpm: 45-50

Predicted energy output at average wind speeds: N/A at 8 mph; 5,060 KWH per month at 10 mph; 8,198 at 12 mph Application: Batteryless grid-tie Price (MSRP): $180,000 installed on 132-foot tower rranty: 1 year; extended warranty available

IUmd Turbine Industries anufacturer: 952-447-6064 • www.windturbine.net

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