One design also took care to insulate the fire tube. One example welded a restriction plate on the end of the fire tube and supplied air to the fire tube via nozzles, and closed off the hopper so all air entered the system through the nozzles. NOTE: Also, I'm aware of a couple successful attempts to modify a FEMA which took the form of essentially transforming the base FEMA design into an Imbert. A vehicle application where the output must vary over a wide range is probably the worst use for a FEMA (assuming wood/biomass is used and not charcoal). My experience is very limited, but I remain convinced that a FEMA using a very dry and regularly sized wood fuel can serve in a stationary application reliably for an extended period where the output of the system remains relatively high to keep temperature up. If you research other forums frequented by those with experience (such as, the Yahoo woodgas group, or All Power Labs), then you'll find accounts by those with experience who curse the FEMA with a lot more drama than I've mustered.
The reality is that wood + FEMA = tarry fuel gas.Īctually, I am likely more optimistic about the prospects for using a FEMA than those with more experience than I. With good charcoal one can generate a clean fuel gas with a steel can and a couple of tubing connections (see Gary Gilmore's work). If one removes most of the volatiles from wood (essentially making charcoal in the process), then gasifier design is not so critical. He got good results using charred wood chunks in a FEMA gasifier to fuel his trucks. This includes Wayne Keith whose work I consider to be extraordinary. However, all enthusiasts I know of who use gasification on a regular basis and who started with a FEMA unit have moved on. The FEMA is a good unit for learning, so in that sense it can be useful beyond an emergency unit. I consider the primary purpose of this forum as a resource for education, and I'm trying to encourage the reader to take the claim seriously. Wayne Keith worked pretty well with a modified FEMA design not that I can attest to any working experience as my knowledge is through literature. I am confident you have some insightful knowledge but this sounds a tad bit melodramatic to prove a point. Marcos Buenijo wrote: It is an emergency unit, and should be used as nothing more. I think it's important to provide this kind of disclaimer whenever the FEMA is introduced, especially for those new to the technology. Therefore, if one desires to fuel an engine over an extended period with biomass, then moving beyond the FEMA design is the wise decision. While it can do reasonably well with very dry fuel of a very regular size, it will make a lot more tar than the Imbert under all conditions.
It is an emergency unit, and should be used as nothing more. The purpose of this design is to get engines running quickly for essential functions when only biomass is available as fuel. The FEMA design is generally suited to introduce wood gasification and many variations of this design do power vehicles without destroying them. More to the point and my intention, I think it is polite to give credit to the person in the video who constructed a polished prototype and in my opinion presented the design very clearly. Personally, I find the videos rather interesting and chose not to marginalize the author's efforts.
I have to disagree with you on one point and that is this model is a proven design. The single best resource for this technology is the Handbook for Biomass Downdraft Gasifier Engine Systems: Īmedean Messan wrote:Thanks for the added link. However, it's probably best to take the next step and go with what is known as the "Imbert" design. Personally, I believe that a FEMA system could be optimized for a very particular fuel and, if run at a more or less constant output, then I believe it could make a reliable and useful unit. It's not a bad idea for use as an emergency unit when nothing else is available - more important, this is precisely what the system is designed to accomplish (emergency, and nothing more).
The problem with this is that an engine powered by such a unit will require a lot of regular maintenance. the "FEMA" gasifier) is well known among gasifier enthusiasts for generating a lot of tar. unless you wish to emphasize that it is proven to generate a lot of tar and destroy engines. I would stop short in calling this particular design as "proven".