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Post by droggema on Oct 24, 2011 20:23:04 GMT -8
Hello, my name is Daniel and this is my first time posting. About a year ago, I started building and playing around with an RMH prototype that could co-fire stick/cord wood together with hand pressed, biomass briquettes. My intent was to explore the potential of "flexi-fueled" variations of the RMH design and see if such technologies could provide viable heating solutions for people living at high altitudes and/or cold regions of the developing world (The greater Himalayan and central Asian plateaus, the Andes, the Atlas mountains etc)- These regions are experiencing depletion of high grade biomass fuel, and many folks living in these areas now have to make due with flimsy brushwood and dung. In January of 2011 I sent an email to a handfull of people/organizations who in different ways have a vested interest/involvement in the issue of household energy in high altitude/ cold regions of the developing world. The email included a free of charge pdf of the RMH book (authorized by Ernie Wisner), a brief presentation of the prototype and a few personal thoughts on why I thought this may be worth some further exploration. I wish I had more material to substantiate my "presentation" but with my limited resources and abilities it was all I had to offer. I sent the email hoping that despite its shortcomings, some of the recipients would perhaps see the potential value of RMH design in appropriate tech. development work. It was also a call for collaboration to get RMH designs properly tested. I have pasted a copy of the email beneath this video clip presentation of the prototype; vimeo.com/19415675 I have received feedback from several of the recipients; Nothing big or conclusive, just general curiosity/interest and few words of encouragement as well as updates and challenges concerning their own projects (most notably so from Geres, GTZ (now GIZ) and Sjoerd Nienhuys whose work I greatly admire - look for web-links of the recipients posted at bottom of the email copy). I have also had some interesting e-mail discussions about RMHs with Crispin Pemberton-Piggott. He is a well respected key player in the arena of Improved (Cooking-) Stove programs in the developing world and very active on the bioenergylists.org /stoves forum etc. Many of his comments were directed more directly at the RMH publication - Observations of certain errors and possible half-truths stated in it etc. Through our dialog I have tried to map out and establish the different factors that need to be tested, analysed and established in order to gain more interest from the established stove community. Unfortunately I have not been able to provide Crispin with any of the technical data he has requested.- of special interest was Excess Air using a specific draft calculation formula, the system's thermal efficiency using the Siegert Formula, and potential development of positive pressures in the bench flues. I have no instrumentation nor do I have any idea on how correctly conduct such tests. In the light of all the high quality postings here lately, in particular by peterberg, (-thank you very much for sharing with us Peter) it is tempting to invite Crispin to the list. In spite of the scepticism he has voiced concerning the safety of the RMH design, Crispin has been very forthcoming in our correspondences. This last year he has been heavily involved with developing and testing improved cooking/heating stoves for use in Mongolia. After our correspondences, I have also seen him express interest in learning more about the RMH design in postings he has made on the stoveslist forum at bioenergylists.org. I see that peterberg has a Testo 327-1 ; Peter, have you ever run tests on a basic RMH model? -And if you have, would you be willing to share the results?
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Post by pinhead on Oct 24, 2011 22:40:07 GMT -8
I love your design! In fact, my prototype RMH has some of the same features as yours (I'm not as far along, though; I've just cast the burn chamber). What are you using to make your briquettes? Sawdust and paper? What are the dimensions of your RMH? It definitely has a strong draft even with both inlets open... In my experience (with a 6-inch system) if I leave the bottom inlet open the top inlet tends to smoke-back a little. Do you suppose you're getting stronger draft due to your tall exhaust pipe? Petersburg's Small-scale Development thread has some exhaust analyses included in his posts.
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Post by stovol on Oct 25, 2011 5:07:48 GMT -8
great stuff daniel! thanks for sharing. the briquette system is nice, esp with the hole for air.. i wonder how these would perform in high altitude with the lower oxygen? would system have to be resized in any way you think.. like pinhead said, the draft is strong so hopefully it wouldnt be a problem.. i wish you could get someone to do a test with a combustion analyzer on that.. i wonder if there is some cheap contraption like a lever operated hydraulic cylinder that could be used to press dung etc briquettes.. that way one or two people could press many in one day for the rest of the people to use
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Post by peterberg on Oct 25, 2011 8:46:22 GMT -8
I see that peterberg has a Testo 327-1 ; Peter, have you ever run tests on a basic RMH model? -And if you have, would you be willing to share the results? As it is, the Netherlands are not exactly riddled with RMH's. Personally, I'd join a workshop in August and last Saturday I've visited the place again. I've sold my Testo 327-1 about two years ago, the one I'm using since is a Testo 330-2 which can be coupled to a computer and is able to produce computer-generated spreadsheets and graphics. So, I was able to hook the Testo to the RMH which was already running for an hour or so. To my regret, the temperature sensor didn't function properly for 42 minutes and the graphic became one of the ugliest I've ever produced. But oh well, the rest of it is clear enough, so please ignore the rubbish in the first half. The RMH is built as an 8" system, there is no pipe in the bench, instead the room inside is about 4 times system size. As such, it qualifies as a bell. There are some mountain peaks of the CO-line, caused by letting the fuel lean to the side of the burn tunnel. And clearing up again when the air can get through to the tunnel unrestricted. The stove was running at about half power mode, because the bench wasn't terribly dry at that moment. The exhaust temperature was hovering under 100 centigrade, about 210 F. Excess air is too high, I am expecting running at full power could produce better results.
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Post by droggema on Oct 25, 2011 19:56:50 GMT -8
"What are you using to make your briquettes? Sawdust and paper?" -soaked paper pulp, sawdust, crushed leaves, straw shakes,wood shavings and some goat shit. For general info on biomass briquettes visit; www.legacyfound.org www.youtube.com/watch?v=X3VcqINLV4o" if I leave the bottom inlet open the top inlet tends to smoke-back a little" -this seems to be a common experience for those who have experimented with primary air being fed through air inlet at the bottom of the fuelmagazine (ie not in a down draft fashion) With the briquette set up things change quite a bit as additional dynamics come into play. In the prototype I modified the layout of the feed/combustion chamber in several ways; I'm not gonna try to explain too much as it will be to hard to visualize without a sketchup. One example worth mentioning though, was the recessing of the tunnel floor (comparative to the tunnel ceiling) and cutting of that 1st brick that creates the bottom entry to the tunnel (the first brick of the tunnel floor) at an angle (you can barely see it in the video, it appears as a ramp) to improve the aerodynamic "funneling" of the briquette flame/draft into the tunnel to prevent eddies from forming in the feed chamber and creating smoke backs. stovol; You are askin questions I do not know the answers to as of yet (that is altitude/o2 etc) Peter; nogmaal harstikke bedankt. I see there are some more posts you have made recently that I still have to catch up on. I hope it is alright if I were to make further inquiries concerning your test results. If Mr. Crispin pays the forum a visit, your information and input would be very helpful.
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Post by ringoism on Dec 12, 2011 4:27:37 GMT -8
Eric here, formerly posting re: the feasibility of an all-metal rocket (heating section):
I live in the Western Himalayas (around 7,500ft) and appreciate your efforts (all the more now that our first seasonal snow has me constantly yearning for improved heat sources).
For whomever asked, yes, there are all sorts of home-developed presses / dies / molds for making briquettes, I researched quite a lot of it online a couple months back. Not difficult at all. A guy we know here had made an extremely simple one here several years ago which worked. Better designs are there on u-tube. The best I saw claimed to be able to produce a couple hundred per hour, and with my experience in production machine design, I'd say that a few small changes in details could've improved upon that considerably. If anyone's interested let me know and I'll post the links.
Actually I hadn't complicated my posts by dwelling upon it much, but I had pretty much the same multi-fuel conceptual idea in mind, except in a more compact and portable all-metal design. I was actually going to feed the "holey" briquettes (had in mind around the same dimensions) vertically through the same feed tube that I'd otherwise run my wood in, the latter would be burned with a smaller-diameter insert in order to keep my "system size" (around 3-4") more consistent. I never thought of running them both at the same time, which is pretty interesting.
A third fuel source for my proposed system (I've got it drawn out / dimensioned on paper, waiting for my fabricator to get freed up) would be sawdust, in which case I wouldn't be using the feed tube for fuel at all, it would merely be an air inlet, since my sawdust "magazine" would instead take the place of my insulated riser within the barrel - you can find barrel-based sawdust burners (even commercially available) in a few places on u-tube and elsewhere which would give you the idea - basically the sawdust itself acts as the insulation / heat riser, and is packed tight around a pipe which is then removed, leaving all exposed sawdust surfaces on the ID, where the fire burns from. They are supposed to be very clean burning, and one nice thing about them is that assuming your magazine (& barrel) is big enough, you can load it once and run it all day at a nice, steady, moderate rate with no further fuel inputs. They're apparently used in Kashmir a lot, and a few people around here (a little further east) have tried them and still use them, including one of the better local restaurants.
Being that I live in a touristy area where there are a lot of buses / taxis being continually serviced, I also thought of a fourth fuel, that being waste motor oil. It has worked very well in my experience when soaked into either the sawdust or briquettes, but it can be burned alone, too. I think it can be bought for around 15-25cents (US) per liter here. Mother Earth News had developed a waste-oil stove way back which was supposed to be quite clean-burning, and their design was particularly improved by a certain private party later, which comes up readily in searches. He had posted quite a lot of his plans / tests / development online, but more recently decided to commercialize his intellectual property - so it costs you $40+ now for his expertise. Anyway, his can be found somewhere or the other online, and there's probably a lot of other stuff out there, too.
Well, we'll see if I ever do get my four-fuel system up and running - if so, it should be interesting - and I wouldn't expect to ever lack a source of fuel. I like what you've done and hope it can be more widely applied.
Regards, -Eric
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Post by ringoism on Dec 12, 2011 4:37:51 GMT -8
P.S. I'd be interested in seeing your method for forming the briquettes - they must be pretty dense if you're getting 45 minutes out of them. Looks good.
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Post by droggema on Dec 12, 2011 18:09:07 GMT -8
hey Eric, I am attaching a photo I took from when I made the briquette mold and press -sorry I don't have anything better/more detailed on hand. The mold was made from a 9 inch long piece of 6" diameter pvc pipe (schedule 40 or stronger) and a 1 3/4" ID (-the OD, and thus hollow briquette core will be just shy of 2 inches) pvc pipe which needs to be 2 inches or so longer(11"). You will also need a plunger and 2 washers that fill the space/fit snugly between the big and small diameter pipe. I had mine routercut from acrylics at a plastics shop (TAP plastics) then you drill a bunch, and I do mean a BUNCH of holes in both tubes 1/8 or 3/16" on 1/2" centers. Marking where to drill with a sharpie and jig makes it relatively quick, tidy and easy. I made a press with modified dimensions to accommodate bigger briquettes from these plans; home.fuse.net/engineering/biomass/Easy_BioPress_Micro_Compound_Lever_Biomass_Briquette_Press.pdfvideo; (I made the compound lever press) www.youtube.com/user/LeeHiteVideo#p/u/6/Mt0QQe6EetwFor briquettes as big as the ones I was making, I do not think this is the optimal type of press and i think it may be preferable make a car jack press, more like this; www.youtube.com/watch?v=5kkW9XiBPq4&feature=mfu_in_order&list=UL-the reason is that briquettes this big seem to need some extra time of high and static pressure to expel the necessary amount of water and to get the desired density. The fulgorastove/ sawdust bukhari configuration is an idea I have toyed with in my own mind, and although I have not actually tried it out, I have concluded it it may not be very compatible with the RMH design .(Both in terms of combustion efficiency, practical operation, and complex relation of "riser/downer dynamics) On a total aside; I know you have your reasons, and completely valid ones, but perhaps it could be beneficial to reexamine some of the parameters you have given yourself with this project; both in terms of materials to be used (all metal) and system sizing. I am looking forward to getting updates on your project, and I very much appreciate your postings. -daniel
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Post by droggema on Dec 12, 2011 18:13:00 GMT -8
press
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Post by droggema on Dec 12, 2011 18:13:59 GMT -8
press
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Post by droggema on Dec 12, 2011 18:15:54 GMT -8
cast briquette chamber
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Post by droggema on Jan 8, 2015 6:22:08 GMT -8
Hey there, This is Daniel writing; I originally started this thread a couple of years ago but for various reasons I never got any further with the experiments. I think there are quite a few new members on the forum (- as well as many new ideas/projects by the old timers) since this tread was first posted, and I am curious if any of you have fiddled around with similar stuff? The closest I've seen posted here or on other forums has been various pellet setups- which is of course a more relevant fuel for most of us. Anyways, the experiment is described in the Vimeo video link given in the first post of this thread. Happy New Year to you all, Daniel
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Post by Donkey on Jan 8, 2015 22:08:19 GMT -8
Hello Daniel, Long time! Welcome back. As far as I know, the ones you've made (or inspired to have made) are the only of their kind that I've seen. Now that some time has passed, I would be curious to know how you feel about your experiments. How did they operate in the field? What were your biggest headaches and what really worked?
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Post by droggema on Jan 9, 2015 17:33:27 GMT -8
Hey Donkey, Many of the headaches that popped up had to do with the briquettes themselves (with wich I had no prior experience), particularly getting them to fully dry during winter in the pacific NW. Even bake-drying them in an oven took forever as the water used to soak the mix probably swells deep into the lignin/cellulose material. The briquettes also seemed rather hydrophillic, perhaps due to all the paper pulp. With a relative humidity in the 90s this did pose a problem in terms of providing the vivid burn-profile I hoped the briquettes would add to this configuration. During the peak of the burn cycle the setup worked quite nicely, but the briquettes took a bit longer to ignite than I expected. The end phase of the briquette burn-down seemed fraught with problems associated with a lack of ability to control/maintain the focused, invigorating air currants that are necessary to have embers remain vivid, release heat, break down/reduce in volume; all of which are essential to maintain a healthy self maintaining burn-cycle. Some of these latter problems also seem to be present in conventional j-tube setups due to lack of mechanisms to control/focus the air flow directly through the remaining fuelbed and lazy, air(-flow) deprived ember bed. [-no door with air-focusing holes, and no grate or aerated V/sloped bottom] this can be problematic with dense or not perfectly dry fuel wood.
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Post by functional on Jan 13, 2015 12:08:49 GMT -8
Hey there, This is Daniel writing; I originally started this thread a couple of years ago but for various reasons I never got any further with the experiments. I think there are quite a few new members on the forum (- as well as many new ideas/projects by the old timers) since this tread was first posted, and I am curious if any of you have fiddled around wspreading ilar stuff? The closest I've seen posted here or on other forums has been various pellet setups- which is of course a more relevant fuel for most of us. Anyways, the experiment is described in the Vimeo video link given in the first post of this thread. Happy New Year to you all, Daniel Thanks for breathing some life back into this old thread. I found it interesting. The post by Eric aka: ringoism, about the sawdust barrel shape burner had me thinking of a backpackable disposable rocket stove. When your finished your camping trip, no need to pack it up, its gone. POOF! I'm also interested in "pellet" feeders, even if there's a mixture. I've seen a couple of rocket based ones on the web and read about the "dung" based rocket stove and collectively I see potential for recouping poop power. Even in developed countries, there are farmers with extra material that could either generate extra income, or save money and help reduce the environmental impact from methane release by burning the stuff instead of spreading bs. Keith.
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