Wind Turbines: Generating Electricity from Wind Energy
Have you ever seen a wind turbine? If you have, you’ll surely agree that those gigantic blades turning in the wind are a sight to behold. You’ve also probably wondered how a wind turbine works and managed to turn those enormous propellers. It’s mind-boggling, really, considering that the bigger ones have to be transported in trucks with 100-foot trailers.
But what exactly does a wind turbine do, and how does it help deploy renewable energy in the country? To find out, let’s take a look at the details, from how a wind turbine works to its significance in the quest for clean energy.
Explaining Wind Energy and How it is Formed
The wind is the movement of air and other gases through the earth’s surface, and it occurs due to a combination of several factors. These are:
- The uneven heating of the atmosphere
- The earth’s rotation
- Irregularities of the surface of the earth
The heat coming from the sun causes the land to accumulate thermal energy. The same also happens with the air over the land. The air heats up and expands, which causes it to rise as it becomes less dense.
The rising air creates an area of low pressure, forming a vacuum. This vacuum draws in cooler and denser air, causing it to flow into the area of low pressure to fill in the void that developed due to the heated air’s upward motion. The movement produces a convection current, which involves the transfer of energy from one place to another. In such a manner, the thermal energy that accumulated over the earth’s surface and the surrounding air turns into kinetic mechanical energy in the form of moving air.
Wind speeds and flow patterns vary across the country under the influence of factors like vegetation, bodies of water, and terrain differences.
Even during olden times, humans have been using the power of the wind for different purposes. The use of wind power to propel boats, for instance, was recorded in early 500 B.C., and water pumps driven by wind energy were documented in 200 B.C.
Wind Turbine – From Mechanical to Electrical Energy
Wind power is one of the rapidly growing renewable energy sources. In fact, it has surpassed hydropower as the number one supplier of electricity, generating around 300 million megawatt-hours in 2019. That figure exceeded the power coming from hydro by 26 million megawatt-hours.
But how does the wind turn into wind power or wind energy? By using wind turbines to harness the force of blowing wind, that’s how.
In a way, wind power can be considered a form of solar energy. That’s because the sun’s heat is one of the causes of wind flow. Like that of blowing wind, every moving object has kinetic energy, which can be transformed into other forms of energy.
Wind turbines harness the kinetic energy of moving air and turn it into electricity. The blades of the wind turbines spin when hit by the wind. And it doesn’t necessarily have to be a strong gust, either. The force created by a gentle breeze (a wind speed of about 3-5 meters per second) can spin the propellers of most wind turbines. The propellers are attached to a rotor, which turns a driveshaft in the nacelle, a box-like structure that houses the tower-top of a wind turbine. A generator inside the nacelle converts the energy of the turning shaft into electricity.
The amount of energy a wind turbine creates varies depending on its size and model. Small wind turbines can generate around 100 kilowatts of electricity from the wind’s kinetic energy. That’s enough to power the needs of a typical household. Meanwhile, massive wind turbines can supply between 4.8 to 9.5 megawatts of electricity using wind energy.
Different Types of Wind Turbines
Wind turbines vary in size, from small turbines or microturbines that produce around 10 kW of power to gigantic ones that can generate approximately 15 megawatts. Large turbines are typically grouped together to create wind farms that supply power to electricity grids.
The length of the blades is one of the most significant factors that determines how much electric power a wind turbine can generate.
Wind turbines fall into two basic types. These are the Horizontal-Axis Wind Turbines (HAWTs) and the Vertical-Axis Wind Turbines (VAWTs).
HAWTs are what most people picture in their minds when they hear the words wind turbine. That because these are the most common type of wind turbines due to their efficiency and strength. This wind turbine typically has three long and thin blades that look like airplane propellers and are fitted to a rotor. The rotor can be positioned either upwind (where the wind strikes the blades before the tower) or downwind (where the wind hits the tower before reaching the blades).
Because the propellers of horizontal-axis turbines are perpendicular to the wind, they can generate more power when they spin compared to vertical-axis turbines. However, they are more affected by changes in wind direction and wind speeds than vertical axis turbines.
The blades of some of the largest horizontal-axis turbines are more than 100 feet long, and they stand as tall as a 20-story building. Their size has a bearing on their energy-producing capacity as the longer the blades and the more elevated the turbines, the more wind energy they capture. In turn, they also generate more power.
A vertical-axis wind turbine has blades installed at the top and the bottom of a vertical rotor. They come in several varieties, and the most common among them is the Darrieus wind turbine, named after the engineer who patented its design. Darrieus wind turbines look like two-bladed giant egg beaters.
Another type of vertical-axis turbine is the Savonius wind turbine which contains solid vanes and can self-start. This means these wind turbines work without the need for an external force (like a gust of wind) to propel them from the point of rest.
VAWTs are omnidirectional. That is, blowing air coming from 360 degrees around them can power the turbines.
Whereas the blades of the horizontal-axis wind turbines are perpendicular to the wind, the turning axis of VAWTs is perpendicular to the ground. This property makes the vertical-axis wind turbines ideal for places with low wind speed or variable wind directions. Even in such areas, these turbines will capture enough power from the wind’s kinetic energy to produce electricity.
Different Applications of Wind Turbines
Wind-based energy production has shown impressive growth. The energy generated by wind turbines can now amply supplement the power coming from fossil-fuel-based sources. Moreover, the technology’s adaptability led to different applications in employing wind power.
Land-based wind turbines are, as their name implies, wind turbine installations situated on the land. They range in size, from a small turbine that generates only around 100 kilowatts to large ones that produce megawatts of power.
Small turbines are usually installed close to where the electric power will be used, such as homes, water pumping stations, or telecommunication facilities.
Meanwhile, the larger ones are most often used by power utilities and are grouped together to form wind farms. These wind farms generate huge amounts of electricity that can power thousands of homes.
- Because they’re installed on land, the infrastructure needed to distribute the electricity they produce involves lower costs compared to offshore wind turbines. That makes them very cost-effective, and the payback time is relatively shorter.
- Land-based wind farms are usually built closer to the end-users, which tend to lessen voltage drop on the cabling.
- The power generated by land-based turbines is less consistent than that coming from offshore wind facilities. That’s because several factors, such as blockages from the surrounding area, can affect how the wind blows.
- Land-based wind turbines impact the physical environment more than offshore wind installations as they can disrupt the wildlife in the area.
Whereas land-based wind turbines use the force of the wind blowing over the land to produce electricity, offshore wind technology harnesses the power of the wind gusting over the open water. Offshore wind installations are geared for large-scale electricity production. Being able to capture powerful ocean winds, they can produce thousands of gigawatts of electricity.
- The wind force is typically greater over open waters. There are also less physical barriers, such as hills or buildings so offshore wind facilities can produce more electricity.
- Being installed far out at sea, the turbines don’t harm birds, bats and other wildlife. Thus, they have lesser negative effects on the environment.
- Constructing offshore wind facilities is extremely expensive. The same goes for maintenance.
- Designing and building offshore wind turbines are more challenging because of the location and environment of the installation areas.
Also known as community wind, distributed wind refers to the use of smaller wind turbines which can supplement the energy needs of homes, businesses, farms, and public facilities.
- The power coming from small wind turbines can help lessen the pressure on the electric grid, which minimizes black-outs.
- There’s no need to build new transmission infrastructures. Instead, this application can use the existing capacity of local distribution grids.
- Like with land-based facilities, distributed wind turbines can also impact the surrounding area.
- The operational costs of distributed wind make it difficult for the application to compete with conventional power sources.
How do Wind Turbines Work When it is not Windy?
Wind turbines work only when the wind is blowing. Without the wind, they stop turning and cease producing energy. But you may have seen windmills turning even during a windless day. The fact that the blades are spinning only means that some wind must still be blowing.
Luckily, it doesn’t take much wind to keep the wind turbines working. A gentle breeze is enough to turn the blades and once wind turbines get going it usually takes a several hours to slow down their rotation even in the absence of blowing wind.
However, during those times when the blades are moving slowly, the wind turbines are also producing less energy.
Why do Wind Turbines not Turn All the Time?
The first thing that may pop into your mind when you see an idle wind turbine is that there’s no blowing wind to propel the blades. While that may be true, that’s not the only reason why wind turbines stop turning.
Here are some factors that may be behind those stationary propellers.
Not enough wind: The wind may be blowing, but it’s not enough to drive the turbines. The rotors and propellers of wind turbines need a significant and sustained wind speed to get going and start producing energy. If that speed isn’t reached, the wind turbines won’t turn.
Too strong wind: On the other hand, when the wind is too strong, the turbines also cease to spin. That’s because high wind speeds can damage the propellers. To prevent this from happening, wind turbines have built-in safety mechanisms that shut them off when the speed of the wind exceeds a certain threshold.
Maintenance or mechanical failures: Wind turbines need routine maintenance to keep them in top operating condition. During repairs and maintenance work, the turbines are shut down.
Demand has been met: In wind farms, wind turbines are sometimes powered down when their energy output equals the demand or if the electric grid can no longer accommodate the supply.
What are 3 Disadvantages of Wind Energy?
Although wind energy is the top source of renewable energy at the moment, it also has its drawbacks. Here are some of them.
1. It fluctuates: Although the planet won’t run out of blowing wind, the speed and force by which it blows vary. This can hamper the efficiency of wind turbines and affect the sustainability of wind energy.
2. The expenses involved are prohibitive: The processes associated with the construction and operation of wind turbines are financially challenging. Small wind turbines cost roughly around $3000–$8000 per kW of capacity, while the price tag of utility-scale ones ranges between $1.3 million to $2.2 million per megawatt of installed capacity.
3. It suits only certain regions: Not all places in the country can put up wind farms or even small wind turbines. Areas that don’t receive enough wind to generate electricity from wind energy won’t benefit from installing them.
How Long Does it Take for a Wind Turbine to Pay for Itself?
A wind turbine typically has a lifetime of around 20 years and can pay for the cost it took to build it in 15 years. As such, the turbine owner can enjoy the profits coming from wind energy for the remaining years of the machine’s life span.
In terms of carbon and energy payback, it takes around 6 months to a year for a wind turbine to offset the energy and carbon emissions associated with its construction.
Wind power is one of the best sources of energy to fill in some of the world’s ever-increasing needs. It’s clean because a wind turbine transforms the wind’s kinetic energy into electricity without emitting greenhouse gases. It’s also renewable. As long as the wind blows, we’ll have wind resources we can turn to when generating electricity from traditional power suppliers isn’t enough for the growing demand. More importantly, it’s nature-friendly because it produces significantly lower emissions that accelerate global warming.
However, before we can entirely rely on our wind resources to produce enough electrical energy to cover our requirements fully, the technology must become more cost-effective. Moreover, the disadvantages associated with it should be addressed.
Be that as it may, the wind industry has made great strides in the U.S., generating electricity amounting to 338 billion kWh in 2020 and supplying over 8% of the country’s utility-scale electricity production.
Wind farms not only supply additional power to the grid but also bring economic benefits to the community as they add new jobs and sources of revenue for the people in the area. In this regard, like solar energy, using wind power to augment the country’s electricity supply will benefit the environment and us, the consumers.