The goal was straightforward: build a generator that converts flowing water into electricity for as little money as possible. The final build came in at around $15, cheap enough to be realistically deployable in places without reliable power infrastructure. Off-grid homes, refugee camps, emergency zones.
The core mechanism is an Archimedes screw turbine, a design that has been around since ancient Greece, originally used to lift water uphill. Running it in reverse, with water flowing through it, spins a shaft connected to a DC generator. The faster the water moves, the more voltage the generator produces. In this model it powers two colored LEDs or a motor through a 2-pin micro connector.
What I liked about this project was how much physics went into something that looks so simple. I worked out the output voltage, current, RPM, and helical path length of the screw blade from scratch. The voltage formula alone connects water density, flow velocity, screw geometry, and generator efficiency. There is a lot going on inside a piece of PVC pipe.
The whole frame is wood, PVC pipe, and salvaged plastic. I soldered the connections, epoxied the screw blades to the shaft, and built the housing from a transparent plastic container. It works. That part still gets me.