What is Wind Electricity
Wind energy is a dynamic if invisible resource—the energy available in a moving mass of air. From grain grinding by simple wind-driven machines in ancient cultures to modern electricity-generating devices, the wind has been tapped to work for us.
Wind is a cubic energy resource. As the wind speed increases, the power available increases cubically. This means that it’s very important to get into higher wind speeds, and the way we do that is with taller towers. Regardless of the turbine or tower type, going higher is the tried-and-true, reliable way to increase performance in a wind generator. And the most common mistake in wind electricity is installing a turbine on a short tower.
The swept area of a wind turbine is the second most important factor (after the wind resource itself) that determines energy production. The circle “swept” by the blades is the collector area. It’s not possible to get a large amount of energy out of a small collector area. Betz’ theorem says we can only get about 60% of the energy out of the wind before we start slowing it down too much and actually decreasing performance. In the real world, well-designed machines can achieve about half of that.
Why Use Wind Power
People choose to use wind energy for a variety of reasons, including perhaps the most important one—they want to! More specific motivations include environmental, financial, independence, reliability, and social.
Energy and our energy choices have a huge impact on our physical environment. More than half of the electricity used in the United States is generated by burning coal. This coal is sourced by strip mining, pit mining, shaft mining, and mountaintop removal. All of these methods of extraction, and the burning of coal, have a deleterious effect on the ground, water, and air, not to mention the health of workers and nearby residents. Other major sources of electricity nationally are natural gas and nuclear energy, both of which have environmental damage and risk involved in fuel extraction and use.
While all energy producing endeavors have an impact, wind energy (as well as other renewables) have a lower impact overall, if well designed and implemented. There is embodied energy in wind-electric systems, but the fuel is free and recurs daily, and the ongoing impacts on the environment are negligible.
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How to Use Wind Power
Four basic types of wind-electric systems are possible, and three are common. Perhaps the simplest type is wind-electric water pumping, which couples a wind generator to an electric pump, usually via electronics. This may be a viable system type when remote water pumping is needed in a windy area. But few if any complete system packages are available for this application, and the need is most often served with wind-mechanical (water-pumping windmill) equipment and solar-electric systems. Direct heating systems are also possible, but typically end users want to do more with their systems than solely heat, and also don’t need heat year-round, so the energy is less useful.
An off-grid wind-electric system uses batteries, and often includes a solar-electric array and back-up generator. These systems must provide all the electrical energy, since utility electricity is not available or desired. This means that they will produce significantly more energy than is used, because they need to keep a battery bank charged, and because there will be times of excess wind where the surplus cannot be used.
A Battery-based grid-tie system is configured very similarly to an off-grid system, but also has a grid connection, and the ability to “sell” surplus energy to the local utility. These systems have the advantage, because of the battery bank, of providing limited backup during utility outages. Wind-electric back-up systems often function quite well because many utility outages are caused by storm, when wind is abundant.
Wind-electric systems can also be of financial benefit, depending on the situation. Off-grid system owners regularly see that having wind electricity in the windy season is more cost effective than utility line extension or increased generator usage. If you live on-grid, you will need a combination of a good wind resource, high utility rates, and decent incentives to compete with subsidized dirty energy.