How We Build a Wind Farm

By Will G Douglas

How We Build a Wind Farm is a good place to start if you're curious about wind turbines, new to the industry or thinking about a career in the wind industry. The book takes you from an idea, through development and then into construction, from digging the foundation, through erection and commissioning of

• Language: English
• Publisher: Will Douglas
• Release date: Sep 23, 2022
• ISBN: 9798986701004

Book preview

Part 1

The Basics

Chapter 1

The Basics

A wind turbine is a device that converts the wind’s kinetic energy into electrical energy. A wind farm—or the proper term, plant—is a cluster of wind turbines in the same general area, connected together by electrical cables. The turbines and wires that connect them converge at a single point and provide electricity to the grid. (The grid is the overall conglomerate of electrical lines and generators that transmits electricity to users.)

Figure 1-1: Old kilowatt turbines in Palm Springs, California.

In recent history, the shortages and higher petroleum prices of the 1970s and 1980s forced people to rediscover alternative methods of power generation and apply them to larger utility scales. This is how wind farms as we know them today were developed. The early generators, which stood on a 70’–80’ steel tower, were around 40 kW (kilowatts).* Figure 1-1 shows an example of these generators.

By the late 1990s manufacturers were pumping out 1000 kW machines that worked better on tubular towers; each one was equivalent to 25 of the smaller 40 kW machines. In the early 2000s the 1.5 MW machine was the workhorse of the industry whereas today we put up many 3 MW–4 MW machines onshore. Offshore machines can produce up to 10 MW each and stand over 700’ high with a rotor diameter of over 500’! Both onshore and offshore models are growing by the day.

*kW (kilowatt) = 1000 watts and MW (megawatt) = 1,000,000 watts

Some wind farms have just a few turbines while others are composed of hundreds. Onshore wind turbines range in height from around 60’ with the old kilowatt machines to 262’, 328’, and even over 360’ towers, which we are installing now. When their blades reach the top of their rotation, they can reach over 580’ in the air!

For years, I was involved with installing 1.5 MW and 2 MW machines. They stood on 80 m towers; their rotor diameter was 92 m. But, as with all things except electronics, the turbines keep getting bigger while producing more power. The advantage of producing more power is clear, but we have to pay closer attention to where we place them. In addition, because the components are getting bigger and heavier, we need to develop more inventive ways of transporting them to the sites.

Meters and feet: Because the most-used brands historically come from Europe, the wind industry uses the metric system as the standard for measurement. As a result, the heights of the turbines can seem odd for many people in the United States. Common heights for turbines are: 80, 90, 100, and 110 meters. These translate approximately into 262’, 295’, 328’, and 360’. If you’re used to the metric system, then no translation is needed.

Figure 1-2 illustrates the key components of a wind turbine: the blades, hub, nacelle, tower, and transformer. Blades are connected to the hub. These together are called the rotor. The hub houses the pitch system, which twists the blades in and out of the wind using hydraulics. (This allows the blades to either catch the wind or shed the wind.) Next is the low-speed shaft which rotates at the same rpm (rotations per minute) as the rotor. The low-speed shaft bolts to the gearbox. The gearbox changes the rpm speed to 100 times its original speed. The high-speed shaft exits the gearbox and enters the generator, where the rotor and stator are. The generator is where the electricity is made. The power then goes to the transformer where the smaller voltage is stepped-up to a larger voltage and eventually makes its way to the substation.

Figure 1-2: Basic parts of a turbine.

Chapter 2

Development

It all begins with an idea. It could be a group of landowners, a community, or developers that decide they want to build a wind farm. Most of the upfront work is performed by developers who will figure out the best areas to build the farm, secure the land, and then work through much of the permitting and regulatory processes, including connection to a utility.

Developers begin with a wind resource map from NREL (National Renewable Energy Laboratories (see Figure 2-1). They look at where the wind resource is both high enough to run modern wind turbines and consistent enough to run the turbines a good percentage of time. Surprisingly enough, this percentage has a wide range, somewhere between 30% and 49%.

Figure 2-1: This wind source map from the National Renewable Energy Laboratories shows the categories of wind strength throughout the United States. (Courtesy: National Renewable Energy Lab)

We aren’t going to get too deep into wind analytics in this book. Let’s just say that our journey begins at the cross section of where the wind is good and electrical lines are readily available to send the power somewhere it can be used. Therefore, along with a wind resource, large capacity power lines are the next requirement. We need transmission lines to carry the massive power that will be produced.

Development is its own large undertaking and this book focuses on building wind farms. Although we won’t delve into development too deeply, for the sake of understanding let’s cover some key concepts.

Note: Although distributed generation is becoming more and more popular, we will focus our attention on transmission. Transmission lines are the large electrical lines that run across the country. They have large towers holding them up and normally look like they cut through the landscape (See Figure 2-2). These lines hold much higher voltages than the distribution lines that bring smaller voltages to your individual house.

Figure 2-2: Transmission lines. These commonly seen towers with wires are part of the grid and carry electricity from a wind farm to a nearby metropolitan area.

Once the developers find an area that has suitable wind resources and proximity to power lines, their next step is to secure interest in the land for this type of use. They need to approach landowners to see who is interested in leasing their land, whether to the developers or the end customer. (Here, the end customer is the future wind farm owner who will eventually assume the lease from the developers and then have wind