Building your own wind turbine can be a fun and educational project. However, without proper planning and design, your homemade turbine is likely to be quite inefficient at generating electricity. In this article, I will walk you through the steps I took to build my own inefficient wind turbine.
Selecting the Turbine Design
The first step is choosing what type of wind turbine design to build. There are two main options:
Horizontal Axis Turbines
This is the classic windmill style design, with blades spinning on a horizontal axis. Horizontal axis turbines are generally more efficient, but also more complex to build.
Vertical Axis Turbines
Vertical axis turbines have blades spinning on a vertical axis. A common design is the Savonius turbine, which uses curved blades. Vertical axis turbines are simpler to construct, but less efficient.
For my first homemade wind turbine, I opted for the simpler vertical axis Savonius turbine design. While it would be less efficient, it would be easier for me to build as a beginner.
Calculating Blade Size and Shape
The size and curvature of the turbine blades have a significant impact on efficiency. Some key calculations include:
- Swept area – The total area the blades cover as they spin. A larger swept area means more wind can be captured.
- Overlap – How much the blades overlap one another. More overlap reduces efficiency.
- Aspect ratio – The ratio of blade height to width. A higher aspect ratio increases efficiency.
I did not perform any calculations and just guessed at the blade size and shape. This resulted in blades with a small swept area, high overlap, and low aspect ratio – all decreasing efficiency.
The materials used for the blades and other components also impact efficiency. Ideal materials are strong, lightweight, and shaped aerodynamically.
For my project, I used heavy plywood for the blades. While easy to work with, the heavy plywood created a lot of drag and reduced efficiency. I also used a metal bar for the turbine axis which added unnecessary weight.
Lighter woods, or even better – fiberglass, would have been better choices. But I was limited by my available materials.
When assembling the turbine, I made a few key mistakes that impacted efficiency:
- Imprecise alignment – The blade axis was slightly crooked. This imbalance created vibration and friction.
- Loose fasteners – I did not properly tighten the bolts attaching the blades to the axis. This allowed vibration and slippage during spinning.
- No bracing – I did not include any bracing to reinforce the turbine structure. The loose structure flexed in the wind, wasting energy.
Taking more time to precisely construct and reinforce the assembly would have improved efficiency. Rushing the assembly resulted in imbalance and structural instability.
To produce electricity, your wind turbine needs to spin a generator. I wanted to use a generator I had handy, instead of buying one sized for my turbine.
The generator I used was:
- Small – Built for a much smaller turbine. My turbine could not achieve the RPMs needed to effectively power it.
- Low efficiency – Even at optimal RPMs, my generator converted only 40% of power into electricity. More efficient models are over 90%.
Using a generator matched to the turbine size and optimized for efficiency is crucial. Otherwise, much of the turbine’s mechanical power is wasted.
Finally, where you place your wind turbine has a huge impact on efficiency. Key factors include:
- Average wind speed – Turbines perform best at sites with average wind speeds of at least 10 mph. My location had just 5-6 mph winds.
- Turbulence – Turbulent, gusty winds reduce efficiency. My turbine was subjected to a lot of turbulence around nearby buildings.
- Height – Wind speed increases with height. My turbine was only 10 ft off the ground, missing faster winds at higher altitudes.
Siting the turbine in an area with high winds, low turbulence, and sufficient elevation is essential for good efficiency. Unfortunately, I sited my turbine in nearly the worst possible spot.
Building your own wind turbine can certainly be a rewarding project. But if efficiency is your goal, be sure to research and plan out your design, materials, assembly, generator sizing, and siting. Otherwise, you may end up with an inefficient system like my homemade turbine! The key factors are proper blade design, lightweight and strong materials, precise assembly, matching your generator, and siting in a windy low-turbulence area. Follow these best practices, and you’ll have yourself an efficient wind turbine.