Windmills have been used for centuries, with the first wind turbine for electricity developed in the late 1800’s. Winds are caused by rotation of the earth, solar heating of the atmosphere and the earth’s surface. We can harness wind energy and use it to generate power as long as sun shines and wind blows. Wind tower electrical generation is one of the fastest energy, and renewable, generation systems today. While there are positives and some drawbacks to wind electric generations, it is a lot like solar in that the actual generation of energy is clean with no pollution during or afterwards. The wind towers however do have to be built and that requires a lot of minerals that need to be mined, smelted and then all used in manufacturing the towers. The wind blades are made of fiber-reinforced epoxy or unsaturated polyester. The towers themselves are primarily made of steel – earlier ones as a steel frame tower and modern ones as steel tubular towers. The turbine, of course has a copper coils – about 4 tons of copper for each MW generation capacity. If you drive by a wind field you will notice that each tower uses three blades. This is optimum for minimum drag (reduced wind resistance) and also to prevent (gyroscopic precession – wobbling) although some smaller tower do use just two blades. Current towers have a life-time expectancy of 20-25 years before they have to be reconditioned and or replaced.
Obviously, when the wind doesn’t blow the tower isn’t generating anything. Wind turbines work between wind speeds of 5-55 mph. Below 5 mph they do not have the momentum to start up and above 55 mph the stress of a fast turning shaft can damage the system. If a high wind above 55 mph do occur then the rotor is locked down. Newer turbines have gearing systems included in the nacelle (the generator part at the top of the tower) that can maintain a constant rotation speed for optimum efficiency. The nacelle and blades can swivel on top of the tower to orientate into the wind to capture the maximum amount of energy. When siting multiple wind towers, the turbulence occurring from the blades has to be taken into account so you will notice that they are evenly spaced where possible – a lot has to do with the land ownership and where towers might be sited. In some places like Iowa, the towers are more randomly placed as some farmers will not have towers in the land. Wind fields are specifically located after extensive long-term evaluation using anemometers that measure wind. The whole of the USA has been surveyed and optimum locations are well established.
The Positives of Wind Energy Generation
It is a non-polluting, clean and renewable source of energy, local, and free. You only need the technology to capture it. It is cost-effective with good return on investment (ROI). Each tower has a small footprint (250 square feet) plus a narrow access road. Once built, the disturbed land around the tower can be reused for farming and grazing. Land owners can create substantial earning for siting a tower. The appearance is seen by many as an attractive statement of renewability, although there are those that consider them an eyesore – beauty is in the eye of the beholder. Currently, wind energy accounts for only about 2.5% of the worlds electrical generation, so has immense potential for expansion.
The drawbacks of wind energy generation
Wind turbines require a consistent source of wind, and even though areas in which they are sited tend to be reliable, calm periods are always problematic. While wind cannot be a primary source at this time, it can be a major contributor as new storage systems are developed and integrated into the grid system. The borders of a wind field can be problematic for wildlife, especially birds and bats that can be hit by wind blades as they rotate. Since wind towers by necessity require open areas the numbers of birds that may be harmed is somewhat reduced. Wind towers do generate some noise as they cut through the air of about 50 decibels (consider that the tips of the blades may be travelling at 200 mph as they move around), which is about equal to someone talking next to you. As stated above, they can be viewed by some as eyesores that tarnish the beauty of rural landscapes. Extensive Investment is necessary and ROI may not be fast enough for some groups. As with any technology that people may object to, there are some fears about safety of wind tower generation. There is the possibility that the towers could be damaged in a storm and threaten the health of people immediately nearby if the blades tore loose from the nacelle. Since these wind fields are only economically placed at key wind locations, there are transmission lines needed, but this is true for any electrical generation site.
Current research and development of wind energy generation
One way to reduce bird and bat deaths is locating wind fields not in major raptor areas or migration flyways. Federal wildlife officials are working with the industry to finalized stricter siting practices. The use of radar technology helps wind field operators know when flocks or migrations of birds or endangered species that are tagged are approaching at heights below 400 feet (the top height of the blades) the field allowing the towers to be temporarily stopped. Ultrasonic acoustic signals on the towers have been found to deter bats from entering a wind field zone. There has also been some dopler signal and bright light research that similarly deters birds, but research is still ongoing. Other biological research studies show that bats are less active in the wind field zone when wind speeds are above 5.5 meters per second, so wind tower operators can stop the generators with lower speeds without affecting power generation output too much. Recent studies have found that painting the towers in a variety of colors or painting the blades in red stripes seems to deter birds from a wind field zone. Of course, we are used to seeing the typical wind tower with three blades, but they do not have to be like that. There is much research in using vertical axis or FloDesign turbines where the rotors are contained in a housing making bird and bat strikes unlikely. What is important to note is that much biological research is ongoing to minimize or eventually remove this problem to wild life as the positive potential of wind energy is utilized more.