For less than $50 you can build a low head, medium power, super low cost and low tech hydro turbine. Can be plugged into any appropriate waterway, uses only basic off the shelf and recycled materials, and simple hand tools. Aiming for 200 to 500 watts of power/ 5-12 kWh per day from 2 meters of drop at about 50 liters per second. This technology was produced in partnership with COACT, an open source green tech incubator in Barcelona. COACT exists to help all kinds of innovators working on green technologies.
Credit Open Source Low Tech