Martin Impler, 45, built three water wheels in 2022. The year before it wasn’t either. During the pandemic years, the master carpenter from Bad Feilnbach in Upper Bavaria preferred not to travel so far, and he sometimes covers a few hundred kilometers for his water wheels. Demand is increasing, says Impler. Some buy the wheels for decorative purposes, for example to set them up in the beer garden, others use the wheels to generate energy.
For many centuries, people have harnessed the power of water to grind grain or power saws to cut wood. They were sung to: “The mill rattles by the rushing brook, clip, clip”, almost everyone knows the children’s song. Many of these small hydroelectric power plants have disappeared in recent decades. Sometimes people whose house is on a creek call the carpenter Impler and ask if he can build them a bike or repair the old one. “It’s not that easy. I have to cancel most of them,” says Impler.
If you want to operate such a wheel, you need a water right, the authorities have to approve the system. In the case of old systems, water rights sometimes still exist, says Impler. For new plants are the regulatory requirements high. Fish stocks must not be endangered. Impler often has to say no on the phone. “It depends a lot on the location,” he says. The slope has to be right, the stream has to have enough water and be wide enough.
Water wheels run day and night
Impler has already built more than a hundred wheels, with a diameter of two to eight meters and an output of 0.5 to 20 kilowatts. “4,000 kilowatt hours of annual output is about enough to cover the electricity needs of a family of four. That’s what a wheel with an output of 0.5 kilowatts achieves if it runs 8,000 hours a year. Water wheels usually run day and night,” he says. Some are made of wood, others are made of steel. The carpenter needs 200 to 300 hours to build a wheel. On-site assembly then takes a few more days.
Martin Impler has already built more than a hundred water wheels.
(Photo: Elisabeth Dostert)
And the price? It depends not only on the size of the bike, but also on the location. 15 000 to 150 000 euros – approximately. He used to be able to calculate the price relatively quickly, “now it’s not so easy because the costs for the material are constantly changing, if it is available at all”. There are, says Impler, only around a dozen commercial providers of such water wheels in Germany. “I do it because I can and I like doing it, but I have to be able to make a living from it.”
The remuneration for renewable electricity from hydropower according to the Renewable Energy Sources Act (EEG) varies in the power class of systems up to 500 kilowatts between 7.67 and 12.52 cents per kilowatt hour, depending on the assignment to the different versions of the law (EEG 2000 – EEG 2021), it says at Federal Association of German Hydroelectric Power Plants.
According to the association, there are currently around 7,300 hydroelectric power plants in Germany with a total installed capacity of around 5,600 megawatts. 6900 plants are classified as small hydroelectric power plants with an output of less than one megawatt. For a while it looked as if the remuneration for systems with an output of up to 500 kilowatts would be abolished. That’s what the “Easter package” from Federal Economics Minister Robert Habeck originally intended. It didn’t get that far after all. Schreiner Impler is also relieved about this.