GEK 5.0 - How does it work?

The GEK has apparently a new heart design?

The web page states:

  1. Increased fuel flexibility via “Reversed Flow Reduction”

New compound hearth architecture: Downward combustion, Upward reduction

Eliminate reduction bell packing by “fluffing” fuel with horizontal and vertical gas flow

Might explain why they have abandoned there forum for the GEK. This new unit is not open source, if you have $26,995 USD you can buy this version 5 power pallet but will increase very soon.

I am very pleased with the results I am getting from my GEK TOTTI that I have built. It is being used as a back up to a solar off grid power system. I can get 6 hours running with a single 200 litre hopper fill, so I can get over 24 KWH. This is more than sufficient to replace lack of solar power for 1 day due to thick cloud cover. I built it with this goal in mind and I achieved it, total cost without the generator is under $1,000 AUD (not counting my labour).

I made few variations to the original design that have worked well and would have liked to have shared it on their site but many attempts to register as user have not been approved.

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looks like their new hearth isn’t open source

Perhaps they have gone with their earlier idea?

Hey Guys,
I’ve been watching the All Power Labs videos by Jim Mason and he gets into energy and heat conservation and rearranging the 4 zones physically to best utilize lost heat. Very interesting and informative, you have to watch it all. It is a series of insightful tutorials explaining exactly what can be done for maximizing heat efficiency and quality gas production. I haven’t seen any “new hearth” design as such, just a reconfiguration of the zones. Maybe I missed it. He does mention steam injection and a reburning tars adaption, as Magne pointed out.
Definitely a great learning experience.
I’ve posted some links, there are more you’ll see in the sidebar when you watch these.
Note that Mason is using very uniform wood chips as fuel. I’m using 1" to 2 1/2" d branches cut 2" long-- about. So it’s difficult, say, to augur feed my fuel, so there’s moisture over my hearth sucking heat from it. Fill your hopper with 20 degrees fuel and it will “suck” heat from the only source available-your hearth area thus cooling it from the drying stage right down through to the reduction stage until it stabilizes. Etc, etc. Good listening videos.
part 7/7

part 7/10

part 8/10

part 9/10

part 10/10

I think APL mostly use wood chips rather than pellets. He does mention in those videos somewhere that he thinks chunks of wood could still be pyrolising in the core still after they enter the reduction zone. The system I have built uses the gas and engine exhaust to preheat the chips. They are well over 100 degrees Celsius even before the exhaust heat gets to them. I can run chips that are too damp to get burning if you try to light them outside the gasifier.

Hi Gary, You are correct, he is using well graded wood chips. My fingers got ahead of my brain. I edited the pellets out of my remark. The point I was trying to make was that my chunky fuel would be difficult to augur and leaves me out for isolating the drying stage like the Totti. However, I should be able to dry and preheat a measured load of fuel with exhaust heat. I could use an Arvid type funnel set up in another container through which I can run waste heat. Shut down, open up hopper, load hot fuel, close up and restart. Not as convenient or efficient as the Totti, but better for my design and fuel size.
The rest of my post is to get folks to see just how important it is to do this research on the science of it all before they build. I found the physical separation of the stages very logical energy and efficiency wise.
I did see the part where wood could still be pyrolysing in the reduction zone (very interesting). This is why I am trying smaller diam fuel chunks.
There’s a ton of wisdom in his presentations.
Thanks for the comment.

Have you tried getting wood chips? I can get all I want for free just down the road, however I plan to move away from this area out into the bush. Then I will need to make my own wood chips, I am thinking of either finding a cheap second hand chipper (not the garden size I have one of those) or building a chunker but setting it up to make something the size of wood chips.

Have a look at the Pyrocoil design from APL, should not be hard to add that to an existing gasifier. The idea of it is to heat the wood to the point that it starts to give off tar.

We have a power generating plant 29 miles down the road that eats up just about every wood chip in the county. The towns, etc that used to leave piles on the edge of the woods now have a source of income from the sale of chips and shoot them into trucks.
The short answer, no.
I saw the pyrocoil in a video, but didn’t take a real close look. I’ll check it out and hopefully find an exploded view of it. I do remember that we want to keep the drying/heating temp just below the pyrolysis temperature so as not to introduce tars in it. I like the flow charts he uses to explain his system changes. It all makes perfect sense…now, lol.
I re-watch Jim Mason’s vids and pick up a nugget or two every time.

The pyrocoil is part of the gasifier so any tar produced is used. Some where on those video’s Jim Mason says the tars produced at the lower temperatures in the pyrocoil are also easier to crack in the reduction zone.

hi folks,

i was just told someone was asking about the v5 specifics so i came and looked. yes, i am going to explain all the details for what’s going on inside with CAD files and miles of text as usual. i’m just not quite there yet. i’m going to be stepping through many topics in the v5, as they relate to new and old learning, over the next few months. the lack of specifics currently is only an artifact of where i’ve got to so far with doc.

more generally, i need to apologize for being gone from the general DIY gasifier discussion for most of the last two years. this does not relate to a change in my or APL’s methods, but rather to distractions from deaths in my family, annoying romantic drama, large business stones needing carrying up big hills, and then nearly cutting off my right hand this summer with an angle grinder con cutoff wheel. all things much better avoided i would offer. also, this v5 design and transition took me about 1.5 years longer than imagined. early designs are much easier when your knowledge and definition of the problem has yet to be complicated by the world.

either way, things are once again calm enough that i think i can show up and enjoy the show again. maybe even contribute something. wayne and chris have been doing a fabulous thing here with drive on wood. i’m really impressed with what you all are accomplishing. it is great to see. though wayne still won’t accept my bet to race for pink slips at bonneville . . . :wink:

and yes, the externally driven pyrolysis using exh heat results in a lower temp pyrolysis over longer residence time. the lower temp creates tars that are easier to crack downstream, as they have less evolution to the double carbon bonded forms that form at higher temps. more primary tars than secondary and tertiary tars. the externally driven pyrolysis is the most important thing we’ve done to improve tar conversion.

however once tar conversion is reasonable, then you start fighting the realities of solid material handling as it relates to hearth flow and bell packing. a good deal of the v5 work deals with this. the hearth and grate solution is very different than what was done previously. it is a projected hearth, with combustion going down, then reduction going upwards around the outside. the char is moved upwards by both mechanical means as well as gas flow. some other curiosities allow you to control the amount of flow and purge of ash as fuel types change.

these issues are much less important with vehicle gasifiers which don’t usually run as long as a generator based gasifier. imagine driving your car for 10-20 hours straight everyday. this is what people want to do with gasifier power generators. you don’t get to stop and poke it. in fact, you aren’t even there operating it to know anything went wrong. much better to have an expert operator trapped in the cab right there with the machine and forced to watch it . . .

more soon.


ps- here’s what the outside looks like for now. there is also a walkaround animation at: - YouTube


Hi Jim,
Thanks for stopping by, it’s nice to hear from you. I’ve been watching and rewatching the Science of Gasification videos and others and continue to mine nuggets that will improve my particular design and understanding of the processes at work. I’ve been plugging them to new members as a must read. Thanks so much for sharing your efforts and plans.
I understand the viable business end of this and wish you every success.


thanks for the info. We look forward to find out about the char moving design and reverse flow reduction. Hopefully your new product sells well. Best wishes for the new year!


Hello Jim,

Thanks much for stopping by the

Thanks to you and your folks in Berkeley for pushing the envelope on gasification , Great job !

Time flies by and you owe me a visit. It seems like yesterday but it has been over five years that we were out there . If you visit I will furnish enough wood for your return trip but it is near 7,400 miles here and back if you make detours to see the country and scenery.

Sorry but I can’t promise a party like you gave us. WOW what a party !! Even shuttle service while we were there. ( pics below)

Also a pic of us in your wood pile processing the wood, powered from the truck gasifier.

Thanks again Jim. If not for your invitation and hospitality I may have never seen California.


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Jim Mason has now explained the inner workings of the V5 on the GEK wiki:

From Max Gasman on the yahoo wood gas group.

1924 George Imbert patented a fundamental version of this basket. Then he discarded it before 1926.

1926 he patented his first version of a straight firetube…


I’m not sure what I think about the high rise basket. I feel the holes on the side will just get plugged. Also, doesn’t it seem the ash would be more likely not fall but want to follow the gas?
By the way, thanks Chris for giving us a peek.

The idea is to keep everything moving above the grate, any ash that rises will either drop due to the reduced velocity of the gas or be collected in the cyclone. Charcoal that has risen up will eventually turn to ash so will either have to fall down or rise up out the top of the grate.

There is certainly enough information in the link to attempt building this design, at the stage I am happy with the performance of my earlier version of the GEK. Although I am not trying to run 24/7 which is what this design is intended to achieve.

I consider designing a grate a balancing act between plugging and excess carbon dust spillage. With a very narrow line between them, while that line moves when different wood is used. Fir acts totally different, compared to beech.

Jim’s new grate sure does look similar to the (pre) war time grates. Nothing wrong with the war time gasifiers. One can read the progress made during the war. I still consider Toblers “Bericht nr. 7” from 1944 the most accurate book on gasifying. Condensed information collected over years, by many engineering teams. Unfortunately a rare book and in German.

I know of a German guy that put the entire gasifier upside down: He feeds the fuel by auger and thus forces charcoal and dust also up. Since gravity is the grate, plugging is impossible. The auger eventually pushes the excess dust over the rim. The patented version seems to have a stirring device to prevent channelling.

Back to Jim’s basket. Not sure if the whole basket remains loose by only gas flow. I can imagine to develope packing on the bottem and sides. That why shaking is still necessary.
Jim, is shaking -together with the relatively small holes- enough to keep the bed loose? What about a U-shaped scraper on the inner side of the basket?



thanks for dropping by. Do you have a link to the Tobler book at a book dealer or something? Antique books are rare but no impossible to find if you can wait :slight_smile:

Any news on the chevy?