Yes, you can technically use a car alternator for a small wind turbine, but it is generally an inefficient and unreliable solution for consistent power generation. While it seems like a low-cost DIY project, a standard alternator is designed for high-RPM operation with a consistent mechanical input from a car engine, not the variable, low-RPM winds of a natural environment. For a practical and efficient home energy system, a purpose-built permanent magnet generator (PMG) is a far superior investment.
The core issue is the alternator's excitation current. A car alternator requires a small amount of electricity to energize its rotor (the field coil) before it can start generating power. In a vehicle, this initial power comes from the car battery. In a wind turbine setup, you need a charged battery connected at all times just to get the alternator to start working, which is inefficient. Furthermore, alternators have a high cut-in speed—the rotational speed at which they begin producing useful power. Most need to spin at over 1,000 RPM, requiring significant gearing to achieve from slow-turning wind turbine blades.
Here’s a comparison of key performance factors:
| Feature | Car Alternator | Purpose-Built PMG for Wind |
|---|
| Cut-in Speed | High (often 1000+ RPM) | Low (150-300 RPM) |
| Efficiency at Low RPM | Very Poor (0-30%) | High (60-80%) |
| Durability in Weather | Low (open bearings, corrosion) | High (sealed, weatherproof) |
| Maintenance Needs | High (brushes wear out) | Low (brushless design) |
| Initial Cost | Low ($50 - $150) | Moderate ($200 - $600) |
| Long-Term Value | Poor | Excellent |
For a viable DIY project, you would need to heavily modify the alternator, such as converting it to use permanent magnets (a "re-wind") to eliminate the excitation current requirement. This is a complex process that requires specialized knowledge. Even then, its efficiency won't match a commercial PMG. If you're serious about generating wind power, investing in a proper low-speed PMG designed for the task will save you frustration and yield significantly better energy output over time.
