I wrote:
Very small; a stream falling 10 or 20 meters is enough as I recall. A garden hose is enough. This is easy to arrange in hilly country.
Not a garden hose. 1" PVC piping. You see it all over the place in Japanese farms, for gravity fed irrigation from cisterns. They also use it for running water in farmhouses (from an spring uphill). You don't have to go far up the hill to get pressure enough for hundreds of watts mechanical. Hydro is the oldest and still the best source of energy.
Before electricity was invented, Charles Babbage proposed using small water-pressure driven engines in houses, where today we use electric motors, because you can turn the power on and off instantly. Elevators using water as a counterweight were developed in the late 19th century, and some were still running in the mid 20th century.
Air-driven pneumatic engines, hammers and the like are still widely used. I just used one today, on my remodeling project.
- Jed
