HOW DOES THE WIND CREATE ENERGY?

It all starts with the sun, which heats the earth, including the air, the land, and the sea. Different areas heat at different rates (think about snow which reflects the sun vs. blacktop which absorbs it and is hot to walk on barefoot). The changes in heat create high and low pressure areas, and air will move from high pressure areas to lower pressure areas. This can be amplified by topographical features (i.e. mountains) and by land/water interfaces. The moving air converts potential energy to kinetic energy, which has the ability to do work. Picture a bowling ball on a shelf – left alone, it has potential energy. Pushed off the shelf, it is converting the energy to kinetic energy, which can then damage the floor it lands on. In the case of wind, this energy can blow a hat off your head, turn your umbrella inside out, and it can spin the blades on a wind turbine.

There are various designs to wind turbines (vertical axis vs. horizontal axis turbines and numerous blade designs for each), but the majority of turbines are horizontal axis (where the wind is blowing perpendicular to the swept area of the blades), and the blades function very similarly to airplane wings. Instead of wind causing lift in an airplane, the blades are fixed to a stationary object, so the blades are designed to rotate. The spinning blades turn a generator, thereby creating electricity. The energy available from the wind is proportional to the 3rd power of the speed of the wind. (For example, when you double the speed of the wind, you receive 8 times more energy, not two times.) This is important from a siting perspective. You not only need a good wind resource, but you need to be free of obstructions which may only slightly reduce the speed, but drastically reduce the power you will receive.

Typically, turbines are designed to have a “cut in” speed – the speed at which the wind must be blowing for the turbine to start spinning and a “cut out” speed – a speed above which the turbine will stop turning (for the safety of the system and the power output).

Wind turbines are given a nameplate capacity, which is its maximum power output. For instance, a 100kW wind turbine will not always be generating 100kW. When the wind is blowing a little bit, it will be generating less power. Therefore, one must look at the combination of the nameplate capacity, and the capacity factor (which is a function of a number of variables). Typical capacity factors range from 20-30%. Therefore, to determine the kWh your system will produce in a year, you must multiply the nameplate capacity by the number of hours in a year, and then by the capacity factor (e.g. 100kW x 8760 hours/year x .25 = 219,000 kWh/year).

ARE WIND TURBINES SAFE?

In short, yes. Proper siting of wind turbines is the key. Concern over ice throw, noise, flicker, and un-specified health problems have all been brought up. There are excellent resources for information on many of these topics from the thousands of wind turbines up and running around the globe. But wind turbines, when compared to other forms of energy generation, have an excellent track record.

For Birds/Bats

The studies on birds are well documented. Human activity kills hundreds of thousands of birds a year. Most of those deaths come from stationary buildings (birds flying into the sides of them), and cars. Wind turbines are insignificant when compared to the other obstacles human development has created. Studies on bat mortality continue, with some claiming that the low pressure area down wind of the turbine being harmful to bats. Again, it needs to be compared to other, more impactful activities that humans take part in. Proper siting removes many of the potential issues surrounding wind turbines, and as an energy generator, they are quite benign.

What can I do to find out if wind energy is right for me or my business?

Contact Waterline for information and a site visit.

We'll be happy to answer your questions about your specific location and needs, and help you answer the important questions when considering wind.

For more questions, visit the fact sheets page at AWEA, or check out our  Wind Energy Resources.