Blowing in the Wind

By Kendra Rand

According to most records, the first windmill started turning in Persia around 200 BC. Life was a little different then…think invention of the horseshoe and the first calculation of the Earth’s circumference. But if you type “windmill” into Google, Bing, or your search engine of choice today, you will still get millions of hits. That is not too bad for a piece of 2,200-year-old technology.

The Pitstone Windmill, located in Buckinghamshire, England, dates back to at least 1627.
Photo by Michael Reeve
Creative Commons

At fourteen, William Kamkwamba used a library book, bicycle parts, trees, pvc pipe, and a few scrap parts to build the first windmill he had ever seen. His work set off a chain of events that have dramatically improved his community and the entire country of Malawi. Read more on his website, www.williamkamkwamba.com.
Photo by Tom Rielly, Creative Commons

The Brazos Wind Farm in the plains of West Texas.
Public domain

The designs and infrastructure have evolved, but the motivation for using windmills is still about the same. Early windmills were primarily used to automate pumping water and grinding grain. Today, people use the electricity produced by windmills (or wind turbines) to power hot water heaters and coffee grinders.

Wind energy is attractive because it is renewable—putting up a farm of windmills doesn’t use up a limited supply of wind like mining does to coal.

Flying kites and tumbling plastic bags show that wind carries kinetic energy. The purpose of a windmill is to harness that energy and transform it into mechanical or electrical energy—energy that can be used to do work. Wind turbines, which are getting most of the attention these days, are windmills that harness wind energy and turn it into electrical energy for homes and businesses.

How do wind turbines work?

The blades harness the kinetic energy of the wind

As wind blows through a windmill, the blades catch the wind and lift up, like a kite.

Kinetic energy is transformed into mechanical energy

Unlike a kite, the blades on a windmill are fixed on one end and so they rotate in the wind. The fixed end is connected to a long rod, or drive shaft. As the blades rotate, the shaft spins.

Mechanical energy is transformed into electrical energy

The mechanical energy from the spinning drive shaft powers a generator, which turns the mechanical energy into electrical energy. The electricity is then run out through power lines and into to the electrical grid.

In 2008, wind turbines generated 1.26% of all of the electricity generated in the United States, and about 1.5% of all of the electricity generated in the world.

Many people would like to see wind energy play a larger role in energy production, because it is a renewable and clean source of energy. However, wind turbines are still only about 20-35% efficient. Continue reading to find out how scientists are trying to increase the efficiency of turbines so they can play a larger role in energy production.

Research

The year 2030 is an important date for wind energy—the U.S. Department of Energy (DOE) and others are pushing for 20% of the electricity in the U.S. to be produced by wind by 2030. Going from 1.26% to 20% is a big jump, and the DOE is relying on their new windmill to help them reach the target.

The windmill, nicknamed “DOE 1.5”, because it can produce 1.5-megwatts of electricity (enough to power about 450 homes), was recently installed just outside of Boulder, Colorado, at the National Renewable Energy Laboratory (NREL). The commercially available windmill isn’t the biggest on record, but it can hold its own! Scientists at the lab will use DOE 1.5 in all kinds of research related to increasing the performance and lowering the cost of wind turbines.

Here are a couple of areas that scientists are planning to explore,

Blades: Long blades enable a wind turbine to capture more energy than short blades, but there is a trade-off—longer blades are heavier and so they are more likely to deform. The key to making more efficient blades is to optimize length, strength, and stiffness, while minimizing weight. One way to do this is to make the blade from more than one material. For example, by sandwiching a lightweight material between two heavier, stiffer sheets, kind of like an Oreo cookie. New materials and manufacturing methods are making it possible for scientists to create new types of blades, and DOE 1.5 will be a good testing site for them.

Trucks capable of transporting wind turbine blades are some of the largest and heaviest vehicles driving on the nation's roadways. Delivery routes must be carefully planned and approved to avoid urban rush hours, narrow lanes, sharp curves and weak bridges.
Credit: Jim Green / NREL

Controls: More wind is always better, right? Well, not all of the time. Imagine these lightweight blades in the middle of a violent windstorm. If there is no way to slow the blades down, they will keep going faster and faster until, well, take a look at this youtube video to find out happens.

In order to keep the blades from flying out of control and windmills from being destroyed in high winds, they need to have some kind of braking system.

The flip side of this is also true. Windmills operate best under certain conditions that are dictated by their design. But, wind speeds are constantly changing. In order to get high efficiency out of a windmill, it needs to be able to work well across a range of wind speeds. Newer windmills are able to adjust the tilt of the blades and other features to control the rotation speed, but there is a lot of room for improvement in this area.

DOE 1.5 is primarily for research, so it will have lots of instruments built in to measure power output, stress on the blades, and other indicators of its performance. The turbine will also power some of the facilities on site and any extra power will feed into the local grid. This installation is an exciting sign of the potential of wind turbines to play a much larger part in energy production in the US. There is a lot to learn about capturing energy from the wind, and DOE 1.5 is sure to keep scientists busy for quite a while!

Blue skies and calm conditions contributed to a smooth installation of DOE 1.5, a General Electric 1.5 MW wind turbine at the National Wind Technology Center.
Credit: Pat Corkery / NREL

The DOE 1.5 at sunset. The wind turbine was obtained from GE.
Credit: Susan Hinnen / NREL

Mark Handschy, senior advisor to DOE Under Secretary Kristina Johnson and Megan McClure, program manager for the U.S. Department of Energy Wind and Hydropower Technologies Program, cut the commissioning ribbon to celebrate the installation of the DOE 1.5-MW turbine installed at NREL's National Wind Technology Center (NWTC).
Credit: Joe Peollot / NREL