How to Build a Windmill: 7 Essential Steps

Personal windmills are rapidly becoming very popular as more and more people are taking an interest in sustainable sources of energy and ways to reduce their dependency on the grid. Consequently, many are wondering how to build a windmill. These structures were one of the greatest breakthroughs in medieval technology. They were transforming wind into working power before the advent of steam and electricity to mill grain, hence the name.

It should be noted, however, that most modern windmills are actually referred to as wind turbines to distinguish them from their older cousins. This guide will teach you how to build a wind turbine; we will use the term “windmill” for the sake of convenience.

a Dutch windmill and multiple wind turbines behind it

Windmills: What to Consider First

Before you begin a project to build a windmill, it’s important to understand a few terms. You should also outline your purpose for building the windmill. If you’re only interested in how to build a windmill as a DIY proof of concept project, you can go ahead and skip to step 6.

Windmills are rated by their “capacity factor”. We can determine it by taking the average amount of power that the windmill generates and dividing it by the maximum (or peak) amount of power it can generate. Therefore, a windmill which can produce a maximum of 100 watts of power but averages 50 watts will have a capacity factor of 50%.

The reason why the capacity factor is so important is that the size, design, and materials used to build the windmill must be calculated by its capacity factor, sometimes referred to as its load factor. Effectively, you’ll be building your windmill based on its capacity factor rather than its maximum (peak) factor. Of course, how strong the wind blows and other factors will determine how much energy your windmill actually produce. Nonetheless, the capacity factor is a good way to estimate how much energy your windmill will be delivering.

Last but definitely not least, windmills are only designed to produce electricity and not store it. As you’ll see when learning how to build a windmill, if the wind stops blowing, your windmill won’t produce any power at all. In order to effectively smooth out variations in energy production, you will need to store the electricity in the form of batteries.

How to Build a Windmill

three men working on a wind turbine

Step 1 – Determine the wind speed

Before researching how to build a windmill, you’ll need to determine the average wind speed for the area that you’re going to install your windmill. Most of the time, you will want a minimum of 7-10 miles per hour (11-16 kph).

Depending on where you live, you may be able to find this information online (search for wind maps) but you can always use an anemometer to measure wind speeds at regular intervals. Remember that seasonal changes in windspeed can strongly affect how to build a windmill.

Step 2 – Check local codes

Every locality has their own rules and regulations about where and how to build windmills. Some jurisdictions impose limits on windmill height, how far the windmill will stand from an occupied structure, or even how close the windmill is to an adjacent property. It’s also a good idea to discuss your windmill plans with your neighbors if you’re building something big.

Step 3 – Evaluate the area

Learning how to build a windmill is relatively easy. Still, you need to make sure that there’s enough space around the windmill to use it properly. Most experts recommend at least half an acre of free space around smaller windmills. Allow a full acre for full-size windmills. Look for any trees or buildings that might interrupt the airflow reaching your windmill as well.

Step 4 – Choose your blades

Effectively, you have two options when it comes to building a windmill. You can buy pre-made blades or make the extra effort to building them yourself. If you’re not completely sure what you’re doing, it’s usually best to buy pre-made blades. You can always make the shaft and other components of the windmill yourself to be used with pre-made blades if you still want an authentic hands-on experience.

The blades of the windmill are what catch the wind and use it to turn it on its axis and generate power. The blades need to be carefully shaped and sculpted in order to get the most power from the wind. Almost all windmills use an odd number of blades for stability reasons. Three blades are the most common option as five or more blades cause the windmill to spin more slowly.

Step 5 – Pick a generator

The wind spinning the blades creates a torque (rotational energy), but you’ll need a generator to convert this into electricity. Most windmill generators deliver DC (direct current) that will have to be inverted to AC (alternating current) if you plan on using the electricity in your home or to power devices like laptops, lights, and televisions.

Much as with the windmill blades, you can choose to build your own generator or spend more for a manufactured generator. If you buy a generator, make sure it can handle low rotation speeds (RPM measured in the hundreds, not thousands). Some people like to repurpose car alternators as their windmill generator. However, this is not usually recommended, as alternators are designed to spin at several thousand RPM. They may not work if the wind speed is too low.

Step 6 – Place the base

Once you have your plan in place, it’s time to start building the windmill. The central verticle axis is known as the spindle, and you’ll need to secure this spindle. Most windmills use a spindle plate, a heavy piece of steel that is welded to the spindle.

Step 7 – Assemble the windmill

Carefully assemble all the components of the windmill; start with the hub, spoke flange, spokes, magnet rotor, spacers, nacelle, wiring, electrical components, and finally the blades.

Whether you decide to manufacture and assemble all parts of the windmill yourself or use some pre-made parts, learning how to build a windmill is a great introduction to using and understanding sustainable forms of energy. A quality windmill is virtually silent and extremely safe. It can produce substantial quantities of energy when mounted in the right location. Let us know how your project came out!


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