Nicely customized! I'll have to track down a copy of you book. Re the cleaning access and soot: if you are getting truly clean combustion, there should be very little in the way of unburned combustibles to condense and collect. Not that the cleaning access issue should be overlooked, but you may want to investigate some form of metered pre-heated secondary air injection to more completely combust the volatiles (I should note here that I'm unfamiliar with the inner workings of the Esse). 3-7 cleanings per heating season sounds like about 2-6 too many, at least for my liking. See the old Richard Hill stick wood boiler design for something that burned very cleanly without sooting up the fire tubes, even when burning ridiculously wet wood, though it required both forced and induced draft to get there. Ideally, by the time the combustion gases reach your water tubes, the only gases present would be N2, CO2 and H2O, though that's likely going to be a hard goal to achieve with the cook stove. What about adding a baffle plate to split the firebox into an upper and lower burn chamber, and injecting the secondary air above the baffle? I think you'd want a sliding blast gate at the rear, so you can open it to let the stack gases rise straight up (following the current path seen in the video) until the stack draws well, then slide the gate shut so that the primary combustion gases are forced to take the long path toward the firebox door and around the end of the baffle, then double back through the upper chamber (where the secondary air is being fed in). Depending on how the baffle plate was supported, the entire plate could probably slide fore and aft to shift whether the draft opening was at the front or rear. Insulate the upper chamber as well as you can on the side walls and top, so as to keep temperatures up. Might be difficult to integrate with the "dogbone" cook top thing, however if you can get the temps up, any soot from the initial stages of the burn should get burned off the water tubes (and the bottom of the cooktop!) if there's much excess secondary air at all. Once you're down to a nice coal bed, the gases could be allowed to pass straight through once again, if desired, and the secondary air feed restricted or shut off completely. Just a thought.

Hmmm. After looking up the "Installation and Operating Instructions for the ESSE Cookstove" PDF, it appears that the draft opening leaving the firebox is located near the _front_ of the burn chamber. woodstoves.net/documents/cookstoves/US_Esse_Ironheart_Cookstove_Instructions.pdf So, flip my "front" and "back" baffle plate shifting directions in the above. I'd wrongly assumed that the opening was at the rear of the firebox. The ESSE does have some form of "secondary air," but it sounds from the manual as if it's intended to be equally as much an "air wash" to keep the door glass soot free as it is to improve combustion efficiency (see the "Notes on Woodburning" section for the best description). Despite studying the cutaway drawing in Figure 3 and the IPL at the end of the manual, it's not clear to me just how the secondary air is fed to the combustion chamber. I may be a bit obtuse... Ideally, all of the off-gassed heavier volatiles driven off by the heat of primary combustion would first be drafted through the hot coal bed, then fed preheated secondary air in a well-insulated secondary burn chamber (that's effectively what rocket stoves and their ilk do very simply, as do the more complicated "downdrafter" designs). But, that could be difficult to retrofit into the existing ESSE cookstove design without some aggressive modification, hence my suggestion above of adding the baffle plate and air feed as a quick-n-dirty half-measure. If a baffle and secondary air feed helps with the excessive build-up, maybe some of the "extra" space above the existing sloped firebox baffle visible in Figure 3 could be re-purposed to form a better secondary burn chamber. From the amount of build-up you are seeing, I'd guess there is still quite a bit of efficiency to be gained from your ESSE. As I'm sure you know (likely better than I), upping the efficiency implies a smaller woodlot, and less time, space and effort needed to lay in a season's store of wood. And, in really cold weather, it may also be capable of throwing more heat (being careful not to warp anything, of course).

For those interested, the Richard Hill Stick Wood Furnace DOE report I referenced in passing above, including both construction and operating analysis details, can be found here: stoves.bioenergylists.org/stovesdoc/Hill/stick_wood_furnace.pdf A report on the analysis of the stack gases done independently by researchers at Virginia Tech can be found here: stoves.bioenergylists.org/stovesdoc/Hill/airtight_woodstove.pdf This batch-fired design would be very amenable to burning coppice, prunings, etc., though as presented it does require a source of electrical power to run the forced and induced draft fans. I'm sure the fans could alternatively be set up to run off: low pressure steam generated by the furnace itself; a Stirling cycle engine; or possibly a thermoelectric pile; if one were averse to using mains power or a battery bank. Also, though show as a boiler, the combustion gases could be run into a "bell" masonry mass similar to the newer Russian mass heater designs, fed under a cook top or to a bake oven, etc.

I'll look into this -in theory of course you are correct, have yet to see anything work the way you're describing in practice though. @@kevinolson1102

Indeed more efficiency could be gained i am sure - there's not much secondary combustion in the ease as far as i can tell. @@kevinolson1102

I'd doubt it - but there's a ton of variables in that equation!

Generally it's hard to get more than 1/4 of the stove/furnaces BTU's out in water.

No, it has no catalyst, nor would you want a stove with one. Once had an old Heartwood with a catalyst, what a nightmare.

You want to put pressure relief valves in the system at any high points. They work well. But apparently RMH's don't heat much water up well - too short of run times.

Ben Falk Dear Ben. What do you mean whith short runs? Are 10 meters stainless pipe coil in a very big maonry bell to little? Also, what are the main things to be aware of when making a thermo syphon? Does one need to be aware of flow rates, is the system airtight? What are min and max pipe length and pipe hight?

That sounds like a ton... by short runs i mean short burn times.

Ben Falk aah.. Lol. Yes, a BatchRocketMassHeater runs about 50 minutes, but the mass stays very hot for many hours. Was thinking to bring the heat to the 1st floor water radiant heaters via therno syphon to also have some heat there. For water we are on mediterranean solar.

Thanks - yeah that can be a big problem. This is all stainless steel and brass.

Yeah - but that's a some real metal work - it's cast iron - weighs about 50 lbs - and has specific heat concentrating baffles in it - it would cost maybe 500-1000 bucks or more to make as nicely - but a heavy steel plate could work. Other problem i didn't mention which is as bad as the non flush surface is that it's not rectangular. It's a silly shape (well for a reason for cooking on top) but rectangular like on the stanley allows replacing easily with a maple sap evaporating catering pan and other things.

Ha. For srsly. Kind of funny when it began playing after i made it the next day.

Ben Falk haha. Good for a chuckle, I'm sure. Timely video, we're going to try tapping a few of our trees as well and see what we can get. Sub nano scale though. Haha