Are bigger wind turbines really the answer?

Wind turbines have proven their usefulness over the past several decades for generating electricity. This wind farm, consisting of 4,000 windmills, at Tracy, California has been generating clean, renewable electricity for two decades.

The design is very simple: the main rotor shaft and electrical generator sit at the top of the tower and must be pointed into the wind for maximum effect. On larger turbines, a wind sensor, coupled with a servo motor, directs the propeller into the wind and a gearbox magnifies the propeller rotation to get more suitable electrical generating power from the generator.

Historically, wind mills have been used to turn machinery which was then used to grind grain, or to pump water from wells into tanks, or to pump water from low-lying areas.

Modern wind turbines are generally used in wind farms to generate electricity. They use computers to control the servo motors and propeller speeds to provide the most efficient electrical generation even when the wind is not at its most optimum speed.

At the end of 2006, worldwide capacity of wind-powered generators was 73.9 gigawatts which represents just over 1 percent of world-wide electricity use. The U.S. reached the 10-gigawatt milestone in 2006, enough to power about 2,500,000 average American homes. A gigawatt is one billion watts of energy.

In striving to generate more electrical power, the Enercon E-126 has been designed to be the world’s largest wind turbine. It is billed to produce over 7 megawatts of energy. Assuming a household consumes 938 kWh per month, one of these wind turbines can supply almost 1,800 homes.

The efficiency of a wind turbine has been proven to max out at 59 percent. Since wind flow can not remain at a constant optimum speed, wind turbine output is never constant. This difference between theoretical capacity and actual productivity is called the capacity factor, which is typically 20-40 percent. Size does not matter when it comes to wind turbine capacity factor.

Therefore, when evaluating a wind turbine’s productivity, it is important to refer to the capacity factor to determine real-life output. A 1 megawatt turbine with a capacity factor of 35% will not produce the advertised 8,760 megawatt hours in a year, but only 0.35x24x365 = 3,066 MWh.

The main advantage to building larger wind turbines is that you don’t have to have as many to get the power you need.

The main disadvantage is their size. The FAA has raised concerns about tall turbines’ effects on radar in proximity to air force bases. Other disadvantages are: too many of them can be an eyesore, they are noisy, and the environmental impact is such that birds are being chopped up by the tens of thousands.

A market for residential wind power is developing for small wind turbines to produce electricity to cut your dependency on the local utility but homeowners are facing opposition from neighbors who don’t want to see a tall, noisy wind mill in the next yard.

Single small turbines, below 100 kilowatts, are used for homes, telecommunications dishes, or water pumping. Small turbines are sometimes used in connection with diesel generators, batteries, and photovoltaic systems. These systems are called hybrid wind systems and are typically used in remote, off-grid locations, where a connection to the utility grid is not available. They can generate enough electrical power for up to 6 average homes.

Larger turbines, typically used in wind farms, on average, produce up to 6 MW each (now 7 MW with the Enercon E-126), which can provide power to 1,500-1,800 average homes per year.

To address the need for larger scale energy production, turbines need to be better designed, not bigger. They need to be less noisy and have less impact on the environment.

For residential use, a long vertical rod with blades along its axis, and attached to the home's roof line at the top of the house or hanging under the eaves would look a lot better than a tall wind mill. Of course the efficiency would have to be tested to see if it is feasible.

There has got to be a more acceptable method of harnessing the wind than with larger propellers and towers.

What is your opinion?