Mini wind turbine for your home

Wind power for the home: opportunities & risks

Maurice Forgeng, EPOCH TIMES

The desire for more energy self-sufficiency is constantly growing – including in one’s own home. While photovoltaic systems have long been commonplace, private wind power still leads a niche existence. Yet mini wind turbines on roofs or in gardens promise an independent power supply around the clock. But how realistic is that?

To begin with, small wind turbines differ greatly in their design. The most common are horizontal turbines with three to six rotor blades. They resemble the large wind farms but are only a few metres high. Models with several blades can start up at lower wind speeds, which is important close to the ground. For where homeowners usually mount their systems – on roofs at heights of five to 30 metres – the wind is much weaker and more erratic than at great heights.

Besides these classic designs, there are spiral-shaped variants such as those from the Dutch manufacturer The Archimedes. These need a minimum wind speed of about 3 metres per second, i.e. wind force 3, and reach their maximum output at around 14 m/s. For comparison: large wind farms only shut down at wind force 9 or higher. This shows that the usable wind window of small systems is much narrower.

An alternative design is vertical wind turbines. Their vertical axis allows them to use wind from any direction, and their compact shape makes them less obtrusive. The generator can be placed close to the ground – an advantage for maintenance and stability. However, their efficiency is about 20 per cent lower than that of horizontal models. In addition, the design can lead to greater mechanical stress, which reduces their service life.

When it comes to costs, it quickly becomes clear why mini wind turbines have so far been rare: while simple balcony models are available from 200 euros, more powerful systems with mast and foundation quickly cost 30,000 to 40,000 euros. According to the German automobile club ADAC, investment averages between 3,000 and 10,000 euros per kilowatt of rated output – many times the cost of photovoltaic systems. At least systems up to ten metres high do not require a permit in Germany.

The small turbines also perform better than their big brothers when it comes to noise. According to the manufacturer TESUP, a horizontal turbine reaches around 37 decibels at a wind speed of 8 m/s – comparable to a quiet conversation. Spiral-shaped models reach up to 45 dB. On infrasound, i.e. low, inaudible vibrations, there are no measurement data. According to the physician Dr. Ursula Bellut-Staeck, “nobody measures any frequencies there”. She sees a clear need for further research.

The question of environmental compatibility also remains unresolved. Although manufacturers often stress that their systems are “bird- and bat-friendly”, the Competence Centre for Nature Conservation and the Energy Transition came to a different conclusion in 2018: the effects are “only partially known”. Isolated bird collisions have already been documented. The rotation of the rotors could also drive away animals in the immediate vicinity.

Whether a small wind turbine is worthwhile ultimately depends on the location. What matters are the wind conditions, the structural load capacity of the roof and the economic viability. Only with frequent, strong wind can the purchase pay off in the long term. Possible disturbances such as shadow casting or flicker should also be taken into account.

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