A small DIY hydro-electric power generator

I was involved with the development of a 5 kW hydro-electric power generator in 1985. It has now run for 25 years and I  publish this description of the plant to celebrate.

The system consists of several main parts: penstock, turbine, belt transmission, generator, voltage regulator and a frequency controller.

The turbine runner is an old Pelton found behind an outhouse in the area. Water flow is controlled by a needle valve inside the penstock nozzle. The runner drives the generator,  a belt transmission is used to increase the speed. The generator is of the synchronous type, the generated voltage level being controlled by varying the field current.

The nominal frequency of 50 Hz is achieved by an electrical controller for the nozzle valve, acting through several intermediate mechanisms:

  • The controller drives a windshield wiper motor in an on/off fashion
  • The motor drives a sprocket, chain, chainring train from an old bicycle to reduce the speed and bring the motor out of the splash zone
  • The chainring shaft drives the pinion of a rack and pinion mechanism taken from a worn out truck
  • The rack moves the plunger of the valve

A few photos taken during installation and testing, by Helge Mordt:

View towards turbine

View towards the turbine. A: penstock, B: turbine cover, C: belt transmission, D: flywheel, E: motor, F: rack and pinion.

View towards valve transmission

View towards the valve transmission. E: motor, G: valve plunger, H: end switches, I: sprocket and chain.

View towards generator

View towards the generator. J: frequency controller, K: voltage regulator, L: generator, M: frequency indicator.

2 Responses to “A small DIY hydro-electric power generator”


  • Very cool. If you were going to build your own hydro-electric generator today, what would be your first step. Thinking about powering a small home. As cost for the initial setup is a concern for me, I’m asking if you have any ideas. on your build, it looks as if you have used many spare parts, which I love. I, however, am not sure I have the technical savvy to construct such a machine without using some companies premanufactured system. thx Steve

  • I would start with searching for used parts: turbine, pipe nozzle, generator and other mechanical parts. For low power the easiest is perhaps to use a DC generator and use some easily available electronics for solar power to generate 110VAC from that.

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