Markus Padourek

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since Jun 08, 2020
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Recent posts by Markus Padourek

That looks very interesting indeed. I just found another company that is working on an energy solution that is making use of a sterling engine: https://www.azelio.com/
3 weeks ago
Interesting, I just found https://www.blauer-engel.de/en/products/construction-heating/stoves-for-wood - a voluntary german label where particle concentration has to be max 15mg/m3 and additional a particle count  concentration of 5.000.000/cm³ can not be exceeded. It seems currently certified models achieve this by making use of a filter. I wonder if RMHs could be designed to achieve this level without a filter, but I also wonder, given the writing from the dutch agency and some dansih and swedish studies I read about, if there would even be any health benefits of achieving a particle concentration of 15mg/m3 rather than 20mg/m3.
3 weeks ago
Just posted this in another thread and thought it is very relevant. There is a RMH from the netherlands that got certified in the EU and is showing some details: https://www.yocoon.com/hoog-rendement/

The important paragraph (translated), which comes from a report from a dutch government agency:

"In addition to the quantity in an absolute sense, the composition and toxicity of the emitted dust also differs. With good combustion, the dust emission can be limited to approximately 20-50 mg / m3. The composition of the emitted dust then mainly consists of the inorganic components present in the biomass (salts), the toxicity of which is not significant. In contrast, poor combustion not only drastically increases the amount of dust, but also the content of organic condensable tars and soot. These are often toxic or carcinogenic components, which are of great importance for public health."

And this particular RMH has been categorized as <20mg/m3 dust emission. Reading this, I would be very curios to see what would happen if that whole area would switch over to RMHs and using them correctly.
3 weeks ago
Found another seller of stirling ovens and this one looks actually very interesting: https://www.microgen-engine.com/
3 weeks ago

Peter van den Berg wrote:

Markus Padourek wrote:Thanks for the information Peter, that does indeed help a lot. The idea would be to have well-insulated houses, and at list for our house designed with passiv solar principle, but not to passive house standards. And how long is each run for you on average?


Duration of a single run is something between 45 minutes and 1 hour, depending on fuel species.

Markus Padourek wrote:I did not know there was a difference between smoke and vapor plume (I am still relatively new to this topic) - what exactly is vapor plume?


Vapor is moist air, lots of water in the exhaust gases. On a chemical level, result of complete combustion is heat, CO² and water. One kilogram of absolutely dry wood will produce 0.5 liter of water. In the exhaust gases this water is in gaseous form so it won't condensate in the chimney as long as the exhaust temperature is above 45 ºC.

Markus Padourek wrote:Is this purely because the hot air meets with the cold air?


Yes, the steam condensates in the cold air as droplets which immediately spreads out and makes clouds of visible "steam" (*fog*) until it spreads out enough to evaporate again. Often the visable plume begins some distance above the chimney exit, 30 cm (1 ft) is no exception.

Markus Padourek wrote:And apart from the different smell this is clear visually because it is purley white fumes, rather than the typical dark ones, right?


Yes, the smell of wet charcoal is from 9-methyl ketone in very small quantities, real complete combustion is very, very close then. Real smoke moves much slower and tend to drift away without disappearing.

Markus Padourek wrote:Also I would be curios, which batchrockets results do you know of? I only know of https://www.uzume.fr/


There's one Dutch guy who used the technology to build his own heater but refuses to recognize my work. He had his heater tested, one page of the report is here:



Another guy, from Belgium this time, implemented his own heater much later, his result page is here:



Thank you for that detailed information, I also just had a look at yocoon (https://www.yocoon.com/hoog-rendement/) and this will be super-useful data to show. Especially this paragraph:

"In addition to the quantity in an absolute sense, the composition and toxicity of the emitted dust also differs. With good combustion, the dust emission can be limited to approximately 20-50 mg / m3. The composition of the emitted dust then mainly consists of the inorganic components present in the biomass (salts), the toxicity of which is not significant. In contrast, poor combustion not only drastically increases the amount of dust, but also the content of organic condensable tars and soot. These are often toxic or carcinogenic components, which are of great importance for public health"

Which comes from a report linked from a government agency from the netherlands.

Great, so I can show, that as long as properly dry biomass is used and the fire is started correctly, there will be only very little smoke for about 5 minutes and then for the rest of the burn there will be no smoke, just vapor plume (i.e. steam) and the resulting particle emission has an insignificant impact on our health.
3 weeks ago
I was also just thinking about this possibility over TEGs and I have found a german shop: https://www.stirlingshop.de - here you can buy as set:  where they say that will produce on average 200w when there is sun in central europe. They also have the individual building sets: https://www.stirlingshop.de/epages/61267352.sf/de_DE/?ObjectPath=/Shops/61267352/Products/%22Motor/Generator-Einheit_Bausatz_Modellbau%22 and https://www.stirlingshop.de/epages/61267352.sf/de_DE/?ObjectPath=/Shops/61267352/Products/GT03_Acryl_Bauteilesatz. I would be very curios to see how much energy this could produce and how this would work out efficiency wise compared to a TEG.

Even found one specifically looking at combining woodstoves with stirling engines: http://www.kufner-stirling.de/

Another one here: https://www.oekofen.com/en-gb/myenergy365/ though that looks more commercial and is only in combination with a pellet heater.
4 weeks ago

Peter van den Berg wrote:

Markus Padourek wrote: - How long does one generally need to run a RMH for a day in a northern climate for a small house (30-60m2)? 1-2h? And would it be possible to reduce that with passive solar, that on sunny days one might not even need to heat?


It greatly depends on the level of insulation, but in our passive house in the Netherlands we use a 150 mm batchrocket system with a weight of two metric tons. Our house is larger, but the heater is run one charge of 3 to 6 kg soft wood species in the evening while it isn't freezing. The load is tailored to the weather forecast, more sun during the day means a smaller load. During frost periods we run it twice a day, during breakfast and diner. We had a cold spell in February with lots of sun during the day, one evening charge being enough. I have to admit the house sports a lot of glazing facing south, this helps a lot!

Markus Padourek wrote: - If one burns correctly, how much smoke is there visible over the duration of a whole run? I assume there will be some smoke at the start-up and maybe the end? Are there some videos that could be shown?


In a mass heater the core won't cool down completely between burns. We emploi the top-down lighting method, which emits a very little bit of smoke for about 5 minutes during startup. There's lots of water vapor visible during most of the burn of course, exit temperature at the top of the chimney is estimated between 80 and 100 ºC most of the time. This vapor plume dissolves in the air within a couple of meters and is transparent most of the time. It's appearance is much alike the vapor from a condensing natural gas boiler.
No smoke at all at the end of the burn, definitely.
There's a very old video, illustrating what is visable in frosty weather. At the time I could stand there, my head in the plume and frantically sniffing, only to detect a very faint smell of wet charcoal. Mind you, it happened to be a large fire that was raging in my workshop at the time.

Markus Padourek wrote: - How long is the "start-up" phase of a well-built and well-lit batch-box or dsr RMH? Some people were specifically worried about that phase, knowing it is the most polluting one and arguing that one central stove, distributing the heat to all houses, would be more efficient and reduce the pollution from the start-up phase (which I don't think I agree with, if we also consider line-loss and other possibilities we now loose, like cooking, etc).


Starting up time of a warm-but-not-hot batch box rocket is about 5 minutes, 10 minutes tops.

Markus Padourek wrote:Edit: I have also not found resources that go into details about the exact particles that come out of a RMH exhaust and how they compare to other woodstoves (mostly interested here in how dangerous they are for humans), but given that there are RMH here in the EU that have been certified and are far surpassing the current 2020 regulation as well as the upcoming 2022 regulation, I hope that this will provide enough security for people on that front.


Personally, I've seen the results of two tested batchrockets. First and foremost, those things emits very little smoke to begin with, the dangerous particles are organic, i.e. soot. The particles that remain are anorganic, the residue that can't be burned because these are the minerals that are taken up from the soil by the trees. The limit of dust concentration in the 2022 EU rules is 40 mg/m³ if I remember correctly, both the two rockets did 20 mg/m³. Both were bell constructions, which means gas velocity nearly stalls while entering the bell, so most of the dust is settling at the floor of the bell. The first time I checked my heater I stuck my hand through the cleaning hatch and I couldn't feel a thing. I tried again and waved a bit with my fingers, there was some resistance then. Very fine dust, not what one would call ashes from wood burning.

Suffice to say, batchrocket don't sport an ash drawer because there's no need to, anorganic ash particles are a very very small percentage of the wood's makeup.
I hope this helps.



Thanks for the information Peter, that does indeed help a lot. The idea would be to have well-insulated houses, and at list for our house designed with passiv solar principle, but not to passive house standards. And how long is each run for you on average?

I did not know there was a difference between smoke and vapor plume (I am still relatively new to this topic) - what exactly is vapor plume? Is this purely because the hot air meets with the cold air? And apart from the different smell this is clear visually because it is purley white fumes, rather than the typical dark ones, right?

Also I would be curios, which batchrockets results do you know of? I only know of https://www.uzume.fr/
4 weeks ago

Skandi Rogers wrote:Those two sites talk about masonry stoves which are indeed common and I doubt that type would be any issue to get certified. I just remember a discussion here that was talking about issues connecting a rocket to a normal chimney, which would then cause an issue here. The solid residue printed on the bags of pellets varies between 3% and 4.5% ish. we notice a change in the ash if anything is slightly off with the furnace. wiki states somewhere between 0.5 and 1.4% as being unburned at over 750C (1380F)



Yes, I guess they can build it within the masonry stoves rules, which I have heard is also the case for some states in the US, but they do talk specifically about rocket stoves on their pages: https://fornyetenergi.dk/raketovne/ and http://oekobyg.dk/?page_id=60

But yeah, I don't know that much about these details yet, my plan was to get help from one of these two companies to figure out how it best makes sense to build one in our house.
4 weeks ago

Skandi Rogers wrote:I would say before you bother with all that find out how to connect one to a standard chimney, you have to have it swept and inspected either once or twice a year (it's twice in my present house, was once in the previous) that is a legal requirement and cannot be avoided once bbr has the heating type down. he even has to inspect the second chimney that is not in use and hasn't been for several years.

There's a few threads lying around here on RMH heater smoke and as far as I can see nothing has been actually checked on particle size.
You could try the money angle as well, a central pellet furnace will cost a fortune to run (but produce no visible smoke), straw while it is cheap requires a tractor and really smokes a lot. ground heat would work but is expensive to install and it appears it has a limited lifespan, air/air heatpumps are probably the most obvious solution.

If you figure out how to get one properly allowed can you make a thread on how to do it? it could be very useful for others.



Hmm, good to know about the chimney inspection, I should have already guessed that it can not be that easy to be off-grid here in denmark and be independent of costly services (and the monetary economy) for most things.

But what do you mean, if I figure out how to get one properly? I know at least two people here in denmark who have a rocket mass heater installed, I have not talked to them about details, but I assumed that it was not that difficult.

I know of two danish comapnies selling RMHs: https://fornyetenergi.dk/ and https://oekobyg.dk/

I think the central pellet furnace is not really anything the majority is interested in, I think it was more for the sake of argument. Yeah, ground heat and air/air heatpumps both have come up and I assume some people will probably go for the latter (if there are not a group of people who will get ground heat together) - but my aim is really to have an as much as possible electricity free house (certainly for all basic appliances like heating), in fact the plan is to not even have electric wiring installed. But yeah will be interesting where we will get to over the coming months. We are already in talks with the "kommune" (district) about some of these topics (off grid in general, but I don't think heating so far) and up until now they have responded positive to our ideas.
4 weeks ago
And interesting study indeed, but unfortunately no mention of wooden roofs from what I can see. I have ordered the book "Essential rainwater harvesting" and there they briefly talk about wooden shingle roofs, saying that usually they are not used and cedar shakes can be poisonous but that well managed wooden roofs can deliver high quality water. Unfortunately I could not see any further information on that so far, but let's see if I can find any references resources once I have the book.

I could also find some studies that seem to talk about wooden roofs for rainwater catchment, but they are unfortunately either paid for or not in english:
- https://www.researchgate.net/publication/221746231_Quality_of_roof-harvested_rainwater_-_Comparison_of_different_roofing_materials
- https://www.researchgate.net/publication/349906397_Roof_runoff_contamination_a_review_on_pollutant_nature_material_leaching_and_deposition
- https://www.researchgate.net/publication/263363138_The_Effect_of_Roofing_Materials_for_Using_Harvested_Rainwater

But looking at the latest two, it is possible to look at the graphs and from what I can tell they seem to suggest that wooden roofs are fine, as long as mosses are being kept off it.

Also just found this document which seems to collect some different studies that also look at wooden shingle roofs: https://repository.lib.ncsu.edu/bitstream/handle/1840.4/8170/1_NC-WRRI-425.pdf?sequence=2&isAllowed=y - I have not looked at it in detail but at a first glance it does seem that wooden shingles might not, by itself, produce the highest quality water but still within range for drinking quality if mantained correctly.
4 weeks ago