Are Wind Turbines And Wind Mills The Same?

Wind turbines and windmills are two technologies that harness the power of wind. While they serve a similar purpose of converting wind energy into power, there are key differences between how wind turbines and windmills operate.

In this article, we will define what wind turbines and windmills are, and compare and contrast their designs, sizes, efficiency, cost, environmental impacts, and more. The goal is to understand if wind turbines and windmills are in fact the same technology.

History

Windmills first appeared in Persia around the 7th century CE (Source). These early windmills were vertical axis wind turbines, with the rotating shaft positioned vertically. They were mainly used for grinding grain and pumping water. The design gradually spread westward, reaching Europe by the 12th century (Source).

The Dutch greatly improved windmill technology in the late Middle Ages and are credited with inventing the horizontal axis windmill that could rotate to face the wind. By the 19th century, over 10,000 windmills dotted the Dutch countryside, used for industrial applications like sawmilling, papermaking, and land drainage (Source).

The first wind turbine designed specifically for generating electricity was built in Scotland in 1887 by Professor James Blyth. His 10 meter tall, cloth-sailed vertical axis turbine powered his holiday home (Source). Though a landmark achievement, Blyth’s turbine was too small and inefficient for commercial use.

Purpose

The main purpose of windmills is to grind grain. They use the wind to turn a large millstone, which then grinds wheat and other grains into flour. Windmills have been used for milling grain since the early Middle Ages in Europe and the 12th century in China and the Islamic world. They continued to be widely used in rural areas around the world until the arrival of steam power and electrical energy in the late 19th and early 20th centuries.

In contrast, the purpose of modern wind turbines is to generate electricity. Instead of millstones, they use blades that are turned by the wind. These blades spin a generator to produce electrical power. While windmills date back many centuries, wind turbines capable of generating electricity were first developed in the late 1800s. Their use expanded rapidly in the late 20th century as a source of renewable energy. Today, wind turbines are an important part of efforts to reduce reliance on fossil fuels and combat climate change.

So in summary, traditional windmills harness wind power for mechanical milling, while modern wind turbines convert wind energy into electricity. Their purposes evolved with changing technology over the centuries.

Source: https://www.treehugger.com/windmill-vs-wind-turbine-5649677

Design

Wind turbines and windmills have some key differences in their design. Modern wind turbines typically have a horizontal axis design, with two or three propeller-like blades that face into the wind. In contrast, traditional windmills have a vertical axis design, with sails or blades arrayed around a vertical shaft.

Horizontal axis turbines are able to take advantage of higher wind speeds at increased heights above the ground. The blades rotate parallel to the ground, perpendicular to the wind direction. This design requires a yaw control mechanism to turn the rotor against the wind. Horizontal axis turbines generate more energy and are more common today.

Vertical axis turbines have a main rotor shaft arranged vertically. The blades or sails can catch wind from any direction, without need for yaw rotation. However, they operate better at lower heights and slower wind speeds. According to one source, vertical axis turbines can generate power at lower wind speeds than horizontal versions but are less efficient overall (https://www.reddit.com/r/pics/comments/258a76/vertical_axis_wind_turbines/).

In terms of number of blades, most modern horizontal axis wind turbines have either two or three blades. More blades can increase energy capture but also increase cost and mechanical complexity. Vertical axis turbines can have numerous blades or sails.

Size

Modern wind turbines are much larger than traditional windmills. According to the U.S. Department of Energy, the average hub height for utility-scale land-based wind turbines has increased 73% since 1998–1999, to about 98 meters (~322 feet) in 2022. That’s about twice the height of the Statue of Liberty. The blades have also grown proportionally larger, with many commercial scale turbines having blades over 60 meters (197 feet) long. For example, GE’s Haliade-X offshore wind turbine stands 260 meters tall (853 feet) with each 107 meter long blade sweeping an area larger than a football field.

In comparison, traditional windmills were much smaller. The smock mill style windmills built by early Dutch settlers in New York were typically only 20-30 feet tall. The fantail windmills popular on farms in the 19th century stood around 30 feet tall with 15-20 foot long blades. So modern wind turbines dwarf the windmills of the past in size and generating capacity.

Location

Wind turbines are typically located in large groups called wind farms, often located in rural or remote areas. According to the U.S. Energy Information Administration, the top five states for wind power capacity in 2020 were Texas, Iowa, Oklahoma, Kansas, and California (Source). Some of the largest wind farms in the U.S. include the Alta Wind Energy Center in California, the Tehachapi Pass wind farm also in California, and the Roscoe Wind Farm in Texas.

While some individual wind turbines may be located on farms or near homes to provide personal electricity, large utility-scale wind turbines are almost always clustered together in large groups in remote areas. Wind farms allow energy companies to capture economies of scale and maximize wind energy production.

Efficiency

Wind turbines and windmills have very different efficiencies when it comes to generating power. Wind turbines are designed to convert the kinetic energy from wind into mechanical power, which is then converted into electricity by a generator. They can generate anywhere from 100 watts for small residential models up to several megawatts for large commercial wind turbines. The amount of power generated depends on the size, design and location of the wind turbine.

In contrast, windmills are designed for milling grain or pumping water, not generating electricity. Their efficiency is measured by how much physical work they can perform, like how much grain they can grind or water they can pump. The typical windmill used for milling has a power capacity of around 10 horsepower. While windmills can be applied for mechanical work, their power generation is far below what modern wind turbines can produce.

So when comparing electricity generation capacity, wind turbines are far more efficient and productive than traditional windmills. But for direct mechanical work, old-fashioned windmills still serve their purpose, albeit on a much smaller scale than massive wind farms designed specifically for renewable energy generation.

Cost

The installation and maintenance costs of wind turbines versus traditional windmills can differ significantly. According to research from the U.S. Department of Energy’s Lawrence Berkeley National Laboratory, the average cost of installing a utility-scale wind turbine declined from around $3,000 per kilowatt in 2009 to around $1,600 per kilowatt in 2019 Source. This reduction in turbine costs is attributed to technology improvements and economies of scale. In contrast, traditional windmills designed for milling or pumping water have much lower installation costs, often under $20,000 total depending on size and materials. However, wind turbines can generate significantly more electricity over their lifetime compared to windmills.

Maintenance costs are also substantially different. Wind turbines require regular maintenance and inspections, which for a utility-scale turbine can cost $10,000-$30,000 per year. Routine maintenance is needed on the gearbox, generator, blades, and other components. Windmills have lower maintenance costs, often just lubrication and blade repairs as-needed at a cost of a few hundred dollars annually. However, windmills generate less revenue given their purpose is usually not electricity production.

Overall, while wind turbines require a much higher initial investment and ongoing maintenance costs, their ability to generate revenue from electricity production over decades of operation makes them economical in the long run compared to traditional windmills in most cases.

Environmental Impact

When wind turbines are first installed, they can be visually intrusive on the landscape. The machines are very tall, often reaching over 400 feet high, and the spinning blades are visible for miles in open country. Many people find them an eyesore initially, spoiling views of the countryside. However, visual impacts tend to lessen over time as people get used to seeing turbines on the landscape.

There has also been concern about wind turbines killing birds and bats through collisions with the spinning blades. However, research shows that bird and bat deaths at wind farms are minimal compared to other man-made structures. Glass windows in buildings kill over 600 million birds per year in the US, whereas wind turbines kill less than a quarter million. Deaths from turbines are also negligible compared to habitat loss and cats, which together kill over 3 billion birds annually. Proper siting and design of wind farms can help minimize bird and bat impacts. Overall, wind energy has one of the lowest environmental impacts of any energy technology.

Conclusion

In summary, while windmills and wind turbines both harness the power of the wind, there are some key differences between them. Windmills are older technologies that use wind to perform mechanical tasks like milling grain or pumping water. They have been used for centuries for agricultural purposes. Wind turbines, on the other hand, are modern machines that convert wind energy into electricity. They have blades that spin as wind blows past them, turning a generator to produce power. While early wind turbines were small, modern utility-scale wind turbines can be massive in size and generate enough electricity to power thousands of homes. Both windmills and wind turbines provide clean, renewable energy from the wind, but wind turbines are much more efficient and effective at harnessing wind power to produce electricity on a large scale.