Small wind turbines for house roofs garden industry agriculture

We live on the Wurster North Sea coast and have already tested several small vertical axis wind turbines (VAWT) on site in the strong wind area. The reason for this is that we want to take advantage of the constant wind here. Unfortunately, we have had to accept one disappointment after another when it comes to the quality and performance of the wind turbines offered on the major portals. At least we were able to hold some manufacturers liable for this.
It was not planned that this experience would lead to a business, i.e. trading in functioning products, but this is how it turned out thanks to the knowledge gained and a good product with a unique selling point.

We would like to share our unfortunately predominantly negative results and experiences with you here:

These findings are based on measurements:

VAWT vertical wind turbine in use:

• the speed,
• the wind speed
• of the output power

of the generators in a dynamometer:

• the speed
• of the delivered voltage
• of the emitted current

We can therefore demonstrably publish the following findings on these products:

Smartwind/ Domus/ Eolo: The rotor blades (partly Darrieus, partly Savonius) are far too small to be able to absorb the promised/ nominal energy (kWh)! Actually <1% of the nominal power!

There are plenty of products of these designs on the market, especially on the major shopping portals.

• Rotor diameter or height less than 1m. How can such limited diameters generate the required torque or such small surfaces absorb the energy mentioned?
• Speeds of up to 1000 or 2000 revolutions per minute at rated power! Which wind turbine achieves such speeds (certainly not vertical Savonius wind turbines, as they are self-braking)?
• Who wants to put up with the noise or vibrations generated at these speeds?
• The manufacturer recommends / supplies vibration dampers? The appliance vibrates, otherwise they would not be necessary. What about the disturbing noises that arise?
• Good wind turbines should also produce at low speeds (e.g. in summer). So make sure you have a(slow rotor = ) permanent magnet generator (PMG) – the larger the diameter, the better!
• Have the so-called power curve (power/wind speed) shown to you as proof – atwhat wind, what power. This is part of a good product!
• A wind turbine with 10kW for 1000 EUR? Even a functioning 10kW generator alone has higher manufacturing costs (even in China!)

Our recommendation: Stay away from such products.
A wind turbine that is supposed to permanently deliver nominal power costs accordingly!