Our Philosophy

Festina lente
-make haste...slowly

Saturday, December 14, 2013

Say Hello To My Little Dragon - Rocket Mass Heater in a Wall Tent

This is the combustion unit in all its temporary glory - standard fire brick J-tube built on a thick 16"X 24" landscape paver base (3 of them laid side-by-side to make a 4' x 2' platform) raised up to create an air space on old clay bricks salvaged from our house in Macon, wide side vertical (~4"), one under each paver joint, both sides, all set on a rigid reflective insulation panel in contact with the wood floor (the thin white strip at the bottom).  For those unfamiliar with rocket mass heaters (RMH) the flue is INSIDE the steel barrel; in this case they call it a heat riser, and ours is an 8" x 8" square clay flue pipe surrounded by a sheet metal jacket with perlite infill between the two for insulation, capped with a little mud to hold the perlite in.  The internal heat riser creates a heat pump that actively moves combustion gases through the unit.  As the gases fall down the perimeter of the barrel, they give up a substantial portion of their heat via radiation to the room before collecting in the bottom of the barrel and exiting through the horizontal flue, actively pumped to the exterior.  The galvalum can closer to you in the photo is the jacket for the feed tube, similarly insulated with perlite, with a tight-fitting lid to kill the fire when we're done with a burn.  The whole shootin' match is enshrouded in concrete we poured into a form (we were in a bit of a hurry or we would have cobbed it - more on that in another post).  The combustion unit weighs approximately half a ton, is supported by extra reinforcement under the tent deck, and cost roughly $200.  She's not going to win any beauty contests, but when you feel the heat it produces on next to no wood, an undeniable fondness for her begins to creep in.

Wet, wet, wettest year I've ever lived through, and abandoned for most of 4 months, there was (and still is) plenty of rehab to do on the old tent and deck floor.  On the left side you can see the mildew and floor wear we're dealing with; to the right where we're headed.  We're painting over the mildewed canvas with an oil-based primer to lock out the fungal unpleasantness (any better ideas?), and you can see where I've sanded and oiled the pine floor.
Not without its own shortcomings, one of the major advantages of a RMH in a tent is that a vertical flue jack through the tent roof isn't necessary, since the flue can exit the tent horizontally.  This nasty mess was caused by leaves and moisture falling in around the flue pipe and getting stuck between the canvas and poly rain fly.  Like any good composting process, it's completely digested the canvas at the pressure point against the internal framework.  Without a vertical flue stack this weakness is never introduced and the integrity of the rain fly remains uncompromised.   This mess has since been stitched, painted, and fully covered from above.

Turn around, view to the south during renovation.  The floor is done now and the painting getting there.  We will also be adding more of the 4' x 8' rigid reflective insulating panels, like we used under the combustion unit, around the walls to help hold heat in, and probably painting over them to match the wall.  Since this photo a screen door has been stripped down, fitted with 4 mil clear plastic sheeting for "panes," and hung in place of the old zippered flaps on a 2x6 frame anchored to the deck.  Makes coming and going so much easier; I wish we'd done that at the beginning.  The RMH combustion unit is built roughly on the old wear shadow spot (lower right of the photo) where the box stove lived last winter. 

This is where the real magic of a RMH comes into play.  With an active heat pumping action and a horizontal flue, we can run a long length of flue pipe through a thermal mass to absorb the remaining heat and store it to dissipate into the room over time.  Unwilling to cart 2 tons of our sandy, clayey, gravely subsoil in by bucket to fill this bench until the trouble-shooting is complete, this is about all you get for now.  There is about a quarter ton of thermal mass under the children's bed to help hold a little extra heat and the flue pipe in place now, and we will be doing our side under the bed soon since it will remain in that form once we build the wood cabin on this platform in the spring.  We're filling the bench only up to near the top of the flue pipe with the subsoil and then topping it off with pea gravel for better heat movement up through the mass and into the bed, and a cleaner finish.  The near section will change forms in the next phase, so we may not be filling it at all.  This bench is 16' long, and the back 10' will be our bedroom in the cabin; the front 6', plus the bend and the combustion unit will, once approved by the county, be cobbed into a permanent couch the shape of a dragon, complete with scales made from old favorite broken pottery we've been carting around with us, emerging from the fairy tale section of the floor-to-ceiling bookcase that will become the wall between the living and sleeping areas.  Safety-wise, the floor of this mass bench is raised up on a 2x6 riser to create an air space underneath, though closed off to keep any wandering mice out.  Once you get around the 90 degree elbow, the flue pipe isn't very hot, so I'm not worried about the mass bench causing any problems with the wood floor, especially with the air space separating the two.  More reinforcement is being added underneath the mass bench as it gains weight.  More details in the future.

Did I mention the trouble-shooting?  RMHs are not for laissez faire fire tenders.  They require attention, and at least a rudimentary knowledge of fire physics and fluid dynamics.  And it helps if you're a bit of a pyro, too.  The 90-degree elbow in this shot has been replaced by an 8-8-8 T-section and cap to provide cleaning access to both the short stretch from the combustion unit and to run my 20' flue brush through the long length of the mass bench and out the far end.  Apparently these dragons like to have their intestines cleaned regularly.  At the far end, the outdoor bit, I replaced the original 90-degree elbow there with a T-section and cap as well.  Besides flue brush access, when the weather is wonky I can go out and light a primer fire in the T-section under the outdoor vertical stack, or slip a battery-powered fan in, to help encourage the draw to move in the right direction until the combustion unit warms up.  Smoke-back into the tent, bad; smoke out the far end vertical flue, good.  Once the system is hot it rockets beautifully and cleanly, with only an occasional tiny belch that usually gets sucked back down the feed tube.  The exit gases move so slowly and are at such a cool temperature when they exit that you can lick the flue pipe (if you really want to) - it's hardly ever above 100 degrees F, even when the rocket is roaring.

So this is the idea for this particular design.  Beds ride on top of thermal mass bench to help keep sweeties warm at night.  Even without the thermal mass in the bench the extra warmth is noticeable.  I built simple plywood platforms, left over from our bath house project, to hold the beds up level with the bench, and, since there's no box spring, give us a bunch of storage space underneath.

Now the kids' bed is added, although I think that's a big pink bunny benefitting from the design, and not Ella.  Theirs is the warmest spot, near the combustion unit, which doles out a considerable amount of heat through the night, too.

You don't burn this kind of stove through the night, though.  You burn it hot and fast, for a few hours before bed, and in the case of a tent, when you wake up in the morning.  Then you cap the feed tube, kill the fire, and bask in the stove's warmth between burns.  This is one of the shortcomings of a RMH in a tent: there's not much insulation in the shell of the structure to hold onto the heat you produce.  We actually use a propane space heater during the night so we can get some good sleep, not be up all night tending a wood stove, but we certainly benefit from the slow-release warmth of a system like this under and around our beds.  And we really built it for the future cabin, when it will function more like it's supposed to.  Most RMH users claim to only burn once a day, for 2-3 hours before bed, and get plenty of heat through the night and the next day from that one burn, sometimes burning only every other day! The savings in firewood (money or processing time) is immense.  Even in a tent, with almost no insulation, we never burn more than 2 cubic feet of firewood a day, and generally less than one.  Last winter we burned ~600 cubic feet in our box stove (our stove season is about 5 months).  Yes, there is a little propane cost to be considered, but only so long as our house is a tent.  The fuel you see in the photo above is kiln-dry hardwood off-cuts I get for free by the trunk-load from a local cabinet shop.
Hard to see through the lunch break, but I've borrowed a trick from Ernie and Erica Wisner's playbook for our stove.  When buying the steel drum for our heat exchanger I got one with a removable lid and lid clamp, so I could open it from the top for inspection and cleaning.  A little stove insulating cord in the lip of the lid keeps it air tight.  Here you see Ella demonstrating the proper use of the stove once it's been shut down after a burn.  The little black and silver fan at the back of the stove top, driven only by a heat differential between its solid base resting on the stove and cooler aerial radiator, is a must-have for tent dwelling.  They are a a bit pricey, but so worth it.  We got ours from Lehman's.

I can't really explain the sense of self-satisfaction I got, and continue to get, from building an inexpensive wood stove from scratch that actually works and keeps my family warm.  I didn't come to the project with any particular skill in this department, and no more experience than one (long) winter with ANY sort of wood stove.  Rocket mass heaters burn very little wood - generally less than a quarter of what a typical box stove burns, and some claim as little as a tenth.  The fuel feeds into the unit vertically, (the fire rocketing sideways through the burn chamber and up the heat riser) and has to be processed down to fairly slim pieces (mine doesn't want to burn anything larger than 3" across, and even that seems to be a chore), but overall the labor input seems very minor compared to the endless splitting of heavy, chunky wood of last winter.  And the fuel requirements lend themselves very well to a coppicing woodlot scheme, which produces thin round fuel every few years on rotation, and which I'm currently developing on our land.  The stove does look a bit like a burn barrel in your living room, but can be dressed up in any number of ways.  Like I mentioned above, we plan to do a cob dragon sculpture around ours, which should hide a lot of the industrial look, but you could stack brick or stone around the parts you don't like for sure.  Just keep in mind that you're adding thermal mass, for long term heat storage and release, and covering the quick radiant warmth you get from a lot of exposed steel.  It wouldn't work very well in a tent in other words.  But coupled with a well-insulated house, or a thermally-massive house, like adobe or cob, I can see a stove like this being a major boon to the owner-builder's comfort and work load.  Weird and quirky, yes, but inexpensive and efficient, too, and utterly fantastic.

Special thanks to Andrew for his help with the materials gathering, layout, and pointers.
Tripp out.

Sunday, December 1, 2013

Local > Organic

It takes a while sometimes to become confident enough in our own capacity for broad systems thinking to feel comfortable making such generalizations, but the more time I spend thinking about these two increasingly popular labels the more confident I feel making them.  A simple food chain perspective can be an illuminating place to begin our thought experiment, and it has become an increasingly common mental pattern for me over the last five years.  

One of the more common tropes in sustainability thinking seems to have otherwise heavy energy users dissecting specific topics or products or activities for ways to make themselves feel better about their day-to-day energy use.  To use the current dichotomy under discussion as an example, the thinking often seems to be that "eating organic is good for the planet, period."  The fact that the organic asparagus in question came from Chile, out of season, seems to be a secondary matter.  Not so fast, I say.  In food chain terms, you've got a relatively high-energy market crop to begin with: cutting asparagus is something that generally has to be done by hand, or by very specialized machinery, and the resulting product has to be handled very carefully between field and market.  All of this would be fine if it were being done in a family garden in the back yard, served up fresh on a lunch salad, or grilled for dinner.  But then we wouldn't be eating asparagus in November, and it wouldn't have been shipped thousands of miles in the process.  Here, "organic" simply becomes a way to soothe our conscience about putting richy imperialist tidbits on American tables whenever and wherever we feel like it.  It doesn't require any sacrifice, no discipline, no behavioral innovation.  Even if the production process on the far end was organic, enriching the soil in which it was grown year after year, all that good work is undone in a long-range shipping and distribution system, with all the fossil fuel burned to make it viable.  We have to consider the NET impact of such a food chain, not just the cultural practices that originally produced the food.  Simply eating organic doesn't ameliorate the greater damages wrought by a high-energy long-range supply network.

Another looming example of systems thinking gone awry is the current "Obamacare" debate.  Health care in the United States has its share of problems, to be sure, but a lack of centralized management wasn't one of them.  In essence, we've taken a system already in need of a major overhaul, in need of major behavioral innovation, and added a new level of organization to the top of its food chain.  Any ecologist worth his salt, as well as plenty of non-ecologists, will know that adding another link to the top of a food chain drastically increases the energy contained in that food chain.  I would hesitate to say that it doubles it, but with the increasing metabolic losses that are inherent in all food chains as one moves up the ladder, coupled with a whole new predator at the top feasting on the former, slightly less metabolically-inefficient, top predator, it's significant.

To illustrate this idea, consider a simple oceanic food chain composed of an autotrophic phytoplankton forming the base of the pyramid, eaten by pelagic krill, krill that are in turn eaten by small schooling fish, and those small fish finally eaten by a tuna.  Totally inventing numbers to save time and simply demonstrate a well-known universal pattern, let's say that the phytoplankton are completely (100%) efficient, turning sunlight and dissolved gases, combined with free minerals in the ocean water, into carbohydrates and cellular structure.  No net metabolic losses there, but this is the only producer in the food chain.  Climb up one level to the krill that eat the phytoplankton and we begin to lose metabolic efficiency; let's say the krill convert phytoplankton to more krill at a 67% efficiency.  That is, for every three pounds of phytoplankton consumed, two pounds of krill are made and maintained.  Still pretty good, but then up one more level to the schooling fish dining on the krill, and let's say our conversion efficiency drops to 50%.  That is, for every two pounds of krill consumed we get one pound of the small fish.  Keep in mind that the krill already lost 33% of the original energy represented by the phytoplankton via their metabolic processes, and now the small fish have lost 50% of that already-reduced amount.  Now we come to the tuna.  They bust up the schooling fish violently, spending a fair amount of the energy they acquired from their last meal in the process, chasing down the little fish, and maintaining a warm body in the process.  Yes, tuna are practically warm-blooded, and that carries a considerable metabolic cost of its own.  Let's assume the tuna convert the schooling fish to more tuna at a 33% efficiency.  That is, in order to make and maintain a pound of tuna, three pounds of the small fish must be consumed.  Now remember that the small fish had already used up 50% of the energy represented in the krill they ate to make and maintain themselves, and that those krill had already used up 33% of the energy represented in the phytoplankton to make and maintain themselves.

This is getting fairly pricey in terms of system energy.  A little quick math shows that we're already down to only about 11% of the original energy represented in the phytoplankton remaining in the tuna stocks.  I.E. in just three consumer stages 89% of our original energy base has been lost to metabolic maintenance of the food chain, and it gets a lot worse every time we go up a level.  For the purposes of our healthcare discussion, let's assume that this is analogous to the U.S. healthcare food chain prior to the enactment of Obamacare: fraught with the inefficiencies inherent to and unavoidable in a multi-level food chain, but more or less sustainable within the current resource environment.  And now let's add another top predator to the food chain above the tuna.  Let's say the small school of tuna just got hammered by a pair of mammoth blue marlin, and that these marlin convert tuna to more marlin at a 25% efficiency.  That is, every pound of marlin requires 4 pounds of tuna to make and maintain it, which reduces our system output from 11% to less than 3% .  This is in essence what centralized management of our healthcare system introduces to its own food chain.  Increasing metabolic loss is inherent in all food chains as you move up the pyramid, and fewer and fewer individuals on any given level can be supported by the levels below. 

Which would all be fine if we were living in a system with an increasing energy base!  That, however, is not our reality.  And it requires a gargantuan suspension of disbelief to protest that fact.  For all practical purposes, we've been living on piles of free energy - provided by half a billion years of ancient sunlight and the incomprehensible power of geologic processes - to make and maintain the extremely long and energetic global food chains that bring us Chilean asparagus in November, and increase our population exponentially.  A finite planet with finite resources and a growing population simply doesn't lend itself to lengthening food chains that require significant increases in embodied energy to create and maintain.  Quite the opposite actually.  There's no need to dissect and analyze the minutiae of the Obamacare plan's ins and outs.  Like incorporating 22 federal agencies under the banner of the Department of Homeland Security in late 2002, Obamacare simply adds another even-higher-energy level of organization, complete with its increasing and unavoidable metabolic losses of operation, to an already overstretched healthcare food chain.  It can't happen; not that it shouldn't happen, it just can't.  From a systems perspective, the only way to make this work is to either shred a whole bunch of other federal agencies (or the federal government itself) in the process, or to magically strike it rich again in the energy lottery.  A quick and honest look at EROEIs across our potential energy resource spectrum is all it takes to send the latter packing.  The former is inevitable in time, but I doubt there are many people drawing a paycheck from the agencies in question who will be amenable to the idea.  Especially when all they're getting out of the deal is more expensive healthcare.  There simply isn't enough free energy in the system to support another trophic level riding atop the healthcare pyramid.

No, the landscape before us is a bit more terrainy than that.  A future largely organized around steadily decreasing access to energy, and increasing price volatility, will be one where resilience becomes more strongly emphasized than efficiency.  The perceived efficiencies of large centralized organization will slowly give way to local, dispersed resilience strategies with local management.  Like an airplane pilot who refuses to remove the redundant spark plugs from his plane's engine in order to reduce weight and save fuel, it just won't seem like a good idea anymore.  As John Michael Greer is quick point out, we over-build bridges for very good reasons.  Producing a growing share of our food in our own back yards, less commuting to work, more farmers markets and fewer supermarkets, more bicycles and fewer cars, more garage workshops, more garden medicine, more village breweries, these are the things that inevitably happen as food chains lose their energy support.  And they foster a resilience over efficiency paradigm.  Once "organic" became standardized it became exploitable within the current high-energy long-range food chain.  Organic sells, and it sells big these days, but where organic once meant buying veggies from your neighbor at the farm stand, it now means looking for the little green and white USDA Organic stamp.  An expensive stamp, a stamp which, more than anything else, means another trophic level piled up on top of the already teetering long-range food supply chain, with its inherent and unavoidabe metabolic losses.  Like DHS and Obamacare, that's not where we need to be looking for our answers.  It's part of an imperial system based on cheap abundant energy that becomes less a part of our reality by the day.

By contrast, when you buy local you are consciously choosing to cut out the middle man, maybe radically cutting out the middle man, shortening the food chain involved by choice, reducing or eliminating level after level of system metabolic loss and expense, which ultimately creates a healthier, less expensive, more resilient overall system.  We've seen how simply cutting the top level off the food chain can have a monumental impact on the whole system's embodied energy.  3% > 11% > 33.5% > 67% > 100%, as you cut each top trophic level off of our example food chain.  Properly considered, an "organic" but long-range supply chain can have a far more deleterious impact on system fitness than a short, not-quite-organic direct sale from the producer.  If we can get it local AND organic, that's a win-win for sure, but if faced with a local OR organic decision, don't be too quick to jump on the organic bandwagon...

In this light, "local" is actually more organic than "organic" that traveled a long way to involve itself in your decision making process.  Organic means "of, related to, or derived from living matter."  If the food chain in which you choose to participate is local, or is shorter than the next option, that means it uses less energy top to bottom, and it will have less impact on the whole living biosphere.  It therefore promotes living matter, promotes life.  And honestly, I don't think it gets any more organic than that.

Just my .02
Tripp out.