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Spruce Stove burns one long log, a bit at a time

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November 20, 2013

The Spruce Stove in use, prior to being closed around the log

The Spruce Stove in use, prior to being closed around the log

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I speak from experience when I say that it's actually fun to go into the woods, saw up fallen trees, then bring the wood home to burn over the winter. What isn't so much fun is subsequently sawing the logs into stove-length pieces. With the Spruce Stove, however, you don't have to – you just continuously feed one long log in as it burns, sort of like feeding a pencil into a pencil sharpener.

The stove was created by Dutch designers Roel de Boer and Michiel Martens.

Users start by placing a log (a section of tree trunk, really) on the adjustable-height support stand, then pushing it into the cylindrical stove – presumably a small fire has already been started in there, using kindling. Once the business end of the log is in, a steel diaphragm is closed around it. From there, users just periodically push the log in a little farther, as the end of it burns away.

The stove itself features fireproof concrete bricks on the inside, to absorb and radiate heat. It also has steel fins on the outside, to increase its heat-radiating surface area.

Users periodically push the log in a little farther, as the end of it burns away

Looking at it, though, one does have to wonder how safe it is. If left unattended, wouldn't the burning section of the log extend out through the diaphragm? Not according to Martens. "What many people think is that the fire will pop out of the stove, but it doesn't," he says. "The draft of the fire sucks the flames inwards."

It also seems likely that, in many homes, bringing those long logs into the house could be rather difficult. That said, though, the stove wasn't designed purely for convenience. "I always look for boundaries of expectation, you think you see what it is but there is always a strange angle in material use, shaping, flexibility or just the whole concept," says Martens. "It is a stove for people who are not afraid of a little adventure, it is a playful stove and you need to play with it to get the touch."

If you're not afraid of a little adventure, you can buy a Spruce Stove of your own. Martens and de Boer are about to start a very limited-edition production run (just 10 units), with each stove priced at €4,500 (about US$6,050).

Source: Spruce Stove

About the Author
Ben Coxworth An experienced freelance writer, videographer and television producer, Ben's interest in all forms of innovation is particularly fanatical when it comes to human-powered transportation, film-making gear, environmentally-friendly technologies and anything that's designed to go underwater. He lives in Edmonton, Alberta, where he spends a lot of time going over the handlebars of his mountain bike, hanging out in off-leash parks, and wishing the Pacific Ocean wasn't so far away.   All articles by Ben Coxworth
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26 Comments

Clever idea! Now add a themo-electric power supply (already proven successful in camping cooker/stoves) to run a motor drive pushing the log in for all night running - some trimming of branch stubs might be needed though. Would make a real talking-point for a semi-enclosed outdoor living area as well.

The Skud
20th November, 2013 @ 05:00 pm PST

Just had another thought - can you imagine how teed-off the missus would be if you had only left a short log on the rollers when you went out to nightwork? I cannot see 60 pounds of woman shifting 150 pounds (depending on speciea of tree) of log to keep the heater going!

The Skud
20th November, 2013 @ 05:06 pm PST

$6,000 for the stove and a couple of hundred thousand (or better) for a new house large enough to absorb a tree laying on its side.

Sounds like an economical solution to home heating to me.

Rt1583
20th November, 2013 @ 06:18 pm PST

OK, so they have updated the old open fire used in the great houses and inns of yesteryear.

I remember seeing that type of fire in operation in a country pub in Norfolk (UK) back in the 50s. In fact it remained in operation during the winters until the building was demolished because of road widening in the 80s.

ivan4
20th November, 2013 @ 07:11 pm PST

why does it take the most clever, creative people to see the obvious?

At the price, however, it should have an auto-feed, auto-empty and auto-dispose. Then put it through a wall and add an automatic outside log hopper that releases one at a time and...

DonGateley
20th November, 2013 @ 10:39 pm PST

What about turning the stove and log vertically for an auto-feed? I know this would cause other burning-out-of-the-stove issues, but these guys seem pretty clever :-)

Would also be good to burn old telephone poles...

Otherwise for a couple hundred $$, you can buy yourself a chainsaw. Just saying.

Forest Fab
21st November, 2013 @ 12:20 am PST

Experience has taught me that two or more chunks of firewood always burns better than one. The gasses they give off during combustion feed off each other. Also, i have already used the concept of aluminum "heat sinks" on the stove pipe to increase the heat dissipation before it goes out the chimney. Put a fan on it and the efficiency doubles.

It just isn't practical to have a long log in your space to burn, and the price is ridiculous. As far as atmosphere goes, there ain't none. Fail.

owlbeyou
21st November, 2013 @ 03:31 am PST

@Forest Fab,

If the telephone poles in your country are treated as ours are in the UK, you wouldn't want to burn them in or too near your house, as they are coated in creosote.

Re- this stove design. If one has gone to the trouble of getting logs that are straight enough to feed into this machine, why not invent a machine instead that will feed logs into a saw, so that you then have convenient sized log pieces for a conventional wood burner.

However, should straight logs that could be used for timber or construction be burned at all? Surely it would be better to use wood that is not suitable for such purposes?

bergamot69
21st November, 2013 @ 04:23 am PST

Maybe if you built it into the external wall so you feed the log in through the wall using an auto feed system.

Slowburn
21st November, 2013 @ 05:03 am PST

I think I see the problem:

_________

Dutch {{{{"designers"}}}}} Roel de Boer and Michiel Martens.

^^^^^^^^^^^^

Dave B13
21st November, 2013 @ 08:32 am PST

Ivan4 you are 100% correct!

Not only was the idea of burning an entire log used back in the '50s...

It was used by the Romans 2000 years ago.

Research: Roman Fort, Saalburg Germany.

Ecclesiastes 1:9

What has been will be again,

what has been done will be done again;

there is nothing new under the sun.

PeteKK
21st November, 2013 @ 08:40 am PST

Why not have the stove travel along the timber? Easy to install a track system with controls to set the desired heat output and, therefore, the speed with which the stove consumes whatever variety of tree. A set of rollers mounted on, but external to, the stove would take the place of most of the middle support stands; one of which could travel with the stove as it neared the end of the log. The shutters would automatically open and then close again around the new and presumably different-diameter section. The tricky bit would be to ensure no catching of branch stubs on the rollers. Something like that might be worth $6,000.

Mirmillion
21st November, 2013 @ 09:25 am PST

Although fantastic, this is really nothing new, possibly going back to the 6th to 7th century. It's the same process that was used for the Yule log. Which we now fashion into a cake and eat at Christmas.

The Yule log was a whole tree or a large tree trunk. The end of the trunk was laid on the hearth and lit with a brand from the previous year's yule fire as the rest of the tree stuck out of the hearth into the room. The tree trunk was pushed into the hearth as it burned, which it did continuously for 12 days from Christmas Eve to Epiphany.

Fessler Forge
21st November, 2013 @ 09:32 am PST

Cutting and splitting logs is not purely for masochism but to foster speedy seasoning. How long does it take to season the bulk of log here proposed?

tomtoys
21st November, 2013 @ 10:47 am PST

This is interesting.

I would like to see how this compares with something like a rocket stove or the like in terms efficiency and output.

An autofeed would certainly help as would using the shorter 8 foot standard. Heavy equipment would still be needed to handle the logs but it should be easier and safer than giant logs. Perhaps the loader could be modified to handle several of these logs to reduce the number of trips needed to reload the thing.

You really wouldn't need a bigger house for this just an outbuilding. Already there are outdoor wood-burning furnaces that are designed to provide heat. A modified form of that system with a shed roof to keep the logs on the feeder dry. Perhaps a small power plant could be added or this system works well enough it could serve as the burner for a dedicated small scale plant. That might be feasible since a while back I saw 40kw units that ran on wood gas.

Thane36425
21st November, 2013 @ 11:07 am PST

Does the stove include a fire-suppression system and an extinguisher?

If the log is heavier than the stove, could the raw end tip the stove as it burns weight off? Would a hollow log vent through the unburned end and fill the room with gasses?

This can't be legal under any codes.

lowboy
21st November, 2013 @ 11:14 am PST

Slowburn: Yes. And the "auto feed system" could be gravity, i.e., a 45 degree loading chute.

There is no need to pay $6000. A large rocket stove would work fine. No fan needed. Also, a hybrid gasifer-rocket stove.

Don Duncan
21st November, 2013 @ 11:15 am PST

A down draft rocket stove dose a similar job also good for burning bamboo so it dose not explode .

Stephen Lockett
21st November, 2013 @ 12:53 pm PST

Yes, for those blessed with space, the outdoor furnace concept would fit this idea much better (example: see something like http://www.centralboiler.com/e-classic.html). But I don't see how auto-feed could work, looks like it depends on the diaphragm to make a tight enough seal, and that's just not going to work with an irregular log surface, you'd have to have had someone plane down your fuel into a completely smooth cylinder.

Mats Wichmann
21st November, 2013 @ 12:55 pm PST

They should make these pie-in-the-sky designers actually live with whatever they come up with ... This idea should also apply to car designers, who can design a motor and engine bay so you can only actually work change a spark plug with the motor taken out and on a workbench. Had a Honda years ago that had a little hatch in the firewall so you could reach the rear screws and then the bolts of the cover and the head so change a head gasket.

The Skud
21st November, 2013 @ 04:29 pm PST

I like this idea. It has to be better than splitting wood.

Layne Nelson
21st November, 2013 @ 05:25 pm PST

You have to make it so the log feed automatically. So you put in one long every week and you can leave it unattended. My wood furnace with goo heavy wood inside requires me to fill it every 8 to 10 hours 26X26 in logs. It as a 850cfm blower on it that I have hooked up with the oil furnace blower and it really keeps the house warm and snug. Keep the mess in the cellar instead of the fireplace / wood stove upstairs in the house. I love it.

Paul Bahre
22nd November, 2013 @ 11:22 pm PST

Although it's good to keep on developing new technologies, I don't see the point really. We can all complain at having to work too hard to make a living but what happened to good old exercise? Thinning out the woodland, cutting the length and splitting logs never hurt anyone. Cant wait to get moving on my patch..................better than being a couch potato

bf_308
23rd November, 2013 @ 08:42 am PST

Pellet stove-same concept, less cost, more useful.

ADVENTUREMUFFIN
25th November, 2013 @ 01:39 pm PST

Wow, that looks pretty nice! It is really fun to use that kind of stove and exciting to carry the tree and put it there. Though, I wonder how many hours would that part of the wood can give that warmth to a certain home and then you need to again adjust the wood.

Alice Ross
26th November, 2013 @ 04:23 pm PST

Yeah my condo would be perfect for that.

noteugene
13th December, 2013 @ 11:01 pm PST
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