Wind Turbines vs. Windmills: What’s the Difference?

Windmills, turbines… they’re the same…right? Wrong! While wind turbines are the modern predecessor to traditional windmills, the two structures are quite different. They have separate functions and so are built quite differently. While they seem easy to tell apart, some of us still don’t know the difference. Windmills are part of the ancient human tradition of harnessing the wind, and wind turbines are the latest iteration of that tradition. In this article, we’re going to break down what sets the two apart.

In short, the major difference between the two is their function. Windmills are primarily used to mill grain or pump water, and wind turbines are used to generate electricity. Wind turbines are also larger and more aerodynamic than windmills.

History of Wind Power

Wind energy has expanded greatly in the past ten years, but the idea of harnessing the wind’s energy has been around for quite a while. Sailors have been using the wind to drive their boats for millennia. The Egyptians were known for sailing the Mediterranean as far back as 3000 BCE. The Phoenicians and Austronesian peoples were also known to use sailboats to uphold their extensive trade networks.

The first recorded windmill can be traced back to the Sistan region, along the border of Iran and Afghanistan. This is where the Panemone windmill was invented. It was a simple vertical windmill that used four to eight fabric sails enclosed in a wall with narrow slits, which allowed the wind to pass through. The wall and slits amplified the wind, and the sails turned a central axle. The Panemone windmill was used as a grain grinder or water transportation device.

The panemone wasn’t very efficient, relying on drag to harness energy. It’s similar to a modern Savonius type vertical turbine, which today are used as anemometers or to provide energy to low-power devices. Still, the Panemone was useful enough to spread throughout the Muslim World and even into India and China.

Windmills

Windmills, as we’ve come to know them today, were first recorded in Northwestern Europe during the 12th century. The first known windmill dates back to Northern England in the year 1185 and was used for crushing grain. These windmills became common across the European landscape, especially in the Netherlands. Even today, windmills are considered an icon of Dutch culture.

Windmills were mainly used for crushing grain, hence the name; wind-mill. They used the power of the wind to spin an inner camshaft that drove a grain mill at its base. Windmills used an early gear system to transfer the energy from the sails to the camshaft and into the grain mill. The windmill was especially useful in areas where running water was scarce, as many riverside villages used a watermill for similar purposes. The traditional windmill was made of wood or brick masonry and had four large sails which were covered in fabric.

Some windmills were also used to pump water, called windpumps. While windpumps have been in use since the 9th century, the iconic windpump, commonly called the American windmill, became a staple across the Midwestern US in the 19th century. Farmers primarily used them to pump water from wells, though they were also used to grind grains and saw wood. Whereas the traditional European windmill was a large, wide structure made of wood and brick and had four large sails, the American windmill was perched upon a simple metal lattice framework, with a rotor consisting of several thin metal sails with an attached wind vane. The American windmill soon became a symbol of the Great Plains landscape.

Wind Turbines

Wind turbines are a new twist on the old windmill. Even though wind energy is just now becoming the norm, generator. Midwestern farmers later began generating small amounts of electricity using their windmills in the 1930s, as power lines had yet to reach the remote farms on the Great Plains. At the same time, the precursor to modern wind turbines was being developed in the Soviet Union, with the first being erected in Yalta in 1931. It was 30 feet tall and powered a 100 kW generator.

The first MW size turbine came online in Vermont in 1941. It only ran for about 1,000 hours before suffering from mechanical failures. Ten years later, the first grid-connected turbine went online in the UK. Just as things were looking up for green alternatives like wind energy, the proliferation of fossil fuels put the lid on the development of new turbines.

The oil crisis of the 1970s spurred the growth of the renewable energy sector. Thousands of wind turbines were installed in California, with the Altamont Pass Wind Farm going up in the 1980s. Many of these turbines had lattice towers, which attracted roosting eagles and led to the deaths of thousands of birds when they collided with the blades. This spurred controversy over wind farms and the danger to birds, which continues to this day.

The sleek, all-white, modern turbine design was conceptualized in the 1990s and 2000s. Wind energy in Europe took off during the new millennium, with countries like the Netherlands, Denmark, Germany, and the UK leading the way. Renewable energy incentives (such as the Solar Investment Tax Credit) offered by the US government also spurred development in the States. Today, wind energy is the most abundant form of renewable energy in the US, even overtaking hydroelectricity, with residential vertical wind turbines available at affordable prices (though their effectiveness is unfortunately not equal to that of horizontal turbines).

So what’s the difference?

The wind turbine is based on the classic windmill design, but there are some major differences. The two differ in function, aesthetics, and interior mechanics. Still, the lineage is pretty obvious. Countries like the Netherlands, which has a rich history of building windmills, have adopted the wind turbine as a modern cultural symbol.

The main function of a windmill is to turn wind energy into mechanical energy. Windmills are primarily used to mill grain or pump water. In contrast, with the help of a generator.

The functional differences between the two structures leads to a large difference in internal mechanics. The sails of a windmill are connected via gears to a vertical camshaft that runs down the center of the windmill. This usually drives a grain mill or water pump situated at the base of the windmill, which may or may not be underground. And so, the inside of a windmill tends to be quite spacious.

The energy in a wind turbine remains horizontally oriented. The blades drive bearings in a gearbox that connects to the generator. All the work in a wind turbine is done at the top, and no motion happens below the nacelle. Cables run down the tall tower of the wind turbine, which connects to the electrical grid. The inside of a turbine isn’t as spacious, but the tower has a hollow that allows workers to climb up to the nacelle. The inside of the nacelle is pretty cramped, with the gearbox and generator assembly taking up most of the space.

While windmills and turbines look similar, turbines are much larger. The massive blades of a wind turbine are situated between 60 and 100 meters high to take advantage of the higher wind speeds. Windmills average between 40 and 60 meters tall.

Another major distinction is that wind turbines have blades, while windmills have sails. They’re similar in appearance, but they’re fundamentally different. The blades of a wind turbine generate lift. They’re made of composite materials, and shaped like aerofoils, akin to the wings of an aircraft. The sails of a windmill have more in common with the sails of a ship. They usually have a lattice framework and are covered in cloth. They are powered by drag, making them less efficient.

The number of blades is also a major difference between the two. Traditional European windmills have four sails, while wind turbines usually have three blades. A few varieties of wind turbines have two blades, but they tend to be quite rare, and even rarer are those turbines with no blades at all.

Conclusion

Windmills and wind turbines have a lot in common, but they’re also quite different. What sets them apart is their function. Windmills do mechanical work while turbines provide electricity. Still, the modern wind turbine is a direct line from the traditional windmill, easily recognizable even with its tall profile and sleek aerodynamics. That’s why so many countries in Northern Europe were so open to adopting wind energy; they’ve already been using windmills for nearly a thousand years. It’s also the best place to see old windmills standing right alongside their modern counterparts. It’s an interesting look at the evolution of wind energy over the course of human history.