Fluidyne (and Solar Powered!) Engines

Q: If the fluidyne pump is reliably self-starting it could move water to tilt the collector until a part of the collector shadows it. Something would have to let the water flow back at night to re-aim the collector towards the sunrise. A controlled leak will also rotate the collector eastward (widdershins, opposite the sun's motion) when the sunlight isn't strong enough to start the pump. If you allow electrical controls and a solar cell + battery powered motor you could drive plastic 2:1 reduction gears from the hour hand shaft of a cheap battery clock. The larger gear will move at the same rate as the sun. Size the solar cell to charge the battery, it doesn't have to run the motor directly. Only track when the cell's output is above a threshold so the battery doesn't run down during a week of rain. Some time at night a cam switches on reverse power to reset the collector for dawn. Limit switches stop the motor when the collector reaches the sunrise and sunset positions for June 21.

A: It's a Stirling cycle engine whose only moving parts are a gas (air) and a liquid (water). They're fundamentally a plumbing construct. I have conceptual drawings, a short video of a tiny fluidyne, and a photo of a fuluidyne built largely of 4-inch Schedule-40 PVC drain pipe) at http://www.iedu.com/DeSoto/Projects/Stirling/Dyne.html Other folks have joined the engine development effort and you can see photos and videos of their engines at http://www.iedu.com/DeSoto/Projects/Stirling/Elsewhere/ For a bit of the nitty-gritty stuff, there are pressure, volume, and temperature formulas at They are self-starting, so that might help. The collector may be either a flat panel (for low-temperature versions) or parabolic concentrator (for high-temperature versions). I like the idea of using the pump to power the tracker, but would like to avoid weight-shifting strategies because I think they wouldn't be stable in breezy conditions. Totally automating the tracking mechanism would be ideal. Imagine an unattended pump somewhere in the Kalahari keeping a pond filled for wildlife in a species-preservation project... If it can be made to work really well, the application possibilities go considerably beyond agriculture. Have you played with scouring pads, Chore Boy make in copper if I remember? Total area & type (copper, aluminum, ...) of regenerator material seems to determine volume of heat stored, while the thickness of regenerator material seems to determine the rate of the material's heat transfer. Both are important.

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