In the movie Back to the Future II, Doc Brown returns from the distant future with a new addition to his time-traveling DeLorean. Rather than the hook and pole that captured the 1.21 "jigawatts" from a lighting strike necessary to propel the car back to 1995, this future version of the car is simply powered by a "Mr. Fusion." A banana peel and a half-empty can of beer are now all it takes to provide the energy for a new adventure in time travel.
Over on Instructables, I found a link to the "Fusion Jr." Home Energy Reactor. Disappointingly, it is strictly chemical, not nuclear, in its operation. However, it's still a pretty clever device, and when reading about it I learned something about how my wood-burning stove works.
In this project, Trevor Nestor built a gasifier out of some steel cans and camping pans. The basic idea of a gasifier is that you burn wood, trash, or other unwanted organic items in an environment low on oxygen. The incomplete combustion of the fuel results in a mixture of carbon monoxide, methane, carbon dioxide, and hydrogen. These gases, called producer gas, or syngas, can be removed, purified, and stored for later combustion. Gasifiers have been used to power trucks and tractors, especially during wartime when petroleum is in short supply.
Nestor's gasifier doesn't store gas; it simply burns it. He attaches Peltier junction devices to the combustion chamber to generate electricity. Peltier junctions are notoriously inefficient, but they're easy to use and will at least prove the concept. Nestor notes that despite the Peltier junction inefficiency, they still produce electricity more cheaply than solar cells. The Peltier devices charge a 12V lead acid battery, which in turn is connected to an inverter, to power whatever he decides to plug into it.
This Instructable is not very well written. There are virtually no instructions regarding how the gasifier is constructed, the size or spacing of the air holes (a critical element since it controls the flow of oxygen to the combustion), the wiring of the Peltier devices, or any measurement of how much energy he was able to generate. There is an unsubstantiated claim on one page that this setup could produce 2kW.
All of the systems I have read about generate gas and feed it to a conventional gas generator with a modified carburetor. Another possibility is to burn the producer gas as "Fusion Jr." does, but, instead of Peltier devices, to use the heat to generate steam for a small steam turbine. Or to use another working fluid such as a refrigerant, running a scroll compressor in reverse to generate mechanical energy.
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