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The Science of Energy: Wind
Whether you are sitting outside during a hot summer day with a cool breeze or bundling up to survive the bone-chilling winds of winter, wind is all around when spending time outdoors. Its power has been harnessed for millennia, from ships sailing on the Nile River seven thousand years ago and the windmills of pre-industrial Holland to the electricity generating technology of modern wind turbines that has taken off all over the world.
By: Matthew Novak
Wind is the movement of air from an area of high pressure to an area of low pressure. Wind flow is affected by atmospheric circulation, the uneven heating of the atmosphere from the sun, surface irregularities, like mountains and hills, and the rotation of the Earth. A property of this wind movement is the energy of motion, called kinetic energy, which can be harnessed to sail ships on the high seas or converted into a useable form of electricity that can make a smoothie in a blender or charge smartphones and laptops.
The main components that make up a modern wind turbine are three angled blades connected to a central shaft, a series of gears, and a generator perched atop a tower a couple hundred feet in the air. To produce electricity, wind flowing toward a wind turbine hits the blades, which turns the gears, increasing the revolutions per minute by a factor of one hundred. This converts kinetic energy from the wind into mechanical energy within the blades and shaft, which spin a copper coil in between two magnets within a generator, creating an electric current. By this process, the mechanical energy is converted into electricity within the generator. Electricity can be transported through thick wiring across many miles toward a central power station, much like solar panels, before it gets distributed to houses, businesses, electric car charging stations, and other areas that use electricity.
After the energy crisis of the 1970s made Americans think more about the potential for local renewable energy, a modern wind energy era in the United States began in California in the 1980s. Small companies began to install wind turbines, and as the businesses grew, so did the wind turbines themselves. Taller turbines were more expensive, but were able to produce more energy. However the industry grew faster than demand, which along with political pressure, caused investments to dry up. The wind industry went through a series of boom-and-bust cycles in the early 2000s, because of the on-again off-again nature of federal tax incentives at the time. Since 2006, stable incentives and growing concern for the environment have increased wind power to more than ten percent of the total energy production in the U.S. The Production Tax Credit (PTC), a major federal incentive, as well as state-level incentives, work in tandem to help turbine installers manage the high upfront cost of wind farms within the U.S.
Besides economic and policy fluctuations, a major struggle for wind power is the inconsistent speed and direction of wind. If wind flow is too slow or stops, the blades cannot turn, and if wind flow is too fast, the turbines shut off to avoid damage. Through two major technological advances, that has been partially curbed. Constant speed turbines, in which the angle of the blades change as winds alternate speed, help the turbine maintain a consistent rotation. Variable speed turbines have the ability to rotate at different speeds, while a control system regulates the outflow of power to the grid. While all turbines have upper and lower wind speed limitations, variable speed turbines have the advantage of being able to operate through a wider range of those variations because of their control system technology. Due to the intermittent nature of wind that led to the turbine advances, batteries have also been used to provide a more consistent supply of power to the grid. These technological advances have helped increase the demand for wind turbines significantly, despite the high upfront cost.
The global scale of wind turbine manufacturers and installers has also made individual turbines more affordable, but increased the environmental impact of the industry. The copper, steel, aluminum, plastics, fiberglass, and neodymium (a rare element on Earth) used to make turbines have to be mined, refined, and shipped to other countries to be assembled into the blades, gears, generators, and towers that make up a turbine. All of those are then shipped to wind energy companies throughout the world that truck them to local wind farms for installation, which uses heavy machinery to assemble the turbines on-site. Some of these issues can be mitigated with increased technology, cleaner transport systems, and the use of recycled products in the construction of wind turbines.
Wind is considered a renewable and clean energy source that has become a staple for electricity generation throughout the world. While wind energy in the U.S. only provides ten percent of the total electricity production, some other countries, like Germany, are generating wind power at upwards of thirty percent. With world leaders in wind energy producing more wind power every year and technology rapidly advancing, the future of wind energy is definitely blowing in the right direction!
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