To make my turbine more than just spinning blades, I used math and sensors to measure how much energy it can actually produce. Here’s the step-by-step process:
1. From Pulses to RPM
The encoder creates tiny electrical pulses every time the turbine spins. By counting how many pulses happen in one second, and dividing by the number of pulses per full spin (in my case, 1200), I know how many rotations per second the turbine makes. Multiply that by 60, and I get RPM (rotations per minute).
2. From RPM to Wind Speed
Each full spin of the blade covers the circle’s circumference. Circumference = pi × diameter.
So, wind speed = revolutions per second × circumference.
For my turbine with a 0.33 m diameter, one spin equals about 1.04 meters of air moved.
3. From Wind Speed to Power
Wind carries kinetic energy, and the power in the wind can be estimated with this formula:
Power = 0.5 × air density × swept area × (wind speed³) × efficiency factor
Where:
Air density ≈ 1.225 kg per cubic meter (at sea level)
Swept area = pi × (diameter / 2)²
Wind speed = calculated from RPM as above
Efficiency factor (called Cp) = about 0.35 for my DIY turbine
The interesting part is that wind speed is cubed, which means even a small increase in wind speed makes power rise dramatically.