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Best of Gasifiers? Reviews, Compare, Expereince  RSS feed

 
Justus Walker
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I am a long time gasifier enthusiast. Enthusiast in the youtube, armchair type. Never done much more than a coffee can gasifier in real life. Now I want to get serious and start producing my own energy using a gasifier. I was wondering if any one had REAL life experience or could comment on the following models that are commercially available. I know that I do not want to build my own, since the techniques of tar cracking and high grade filtration are better handled by professionals, I think.

So here are the models I know of. Please let me know what you all think!!

GEK
The gasifier Experimental Kit is a gasifier company that started up literally six months after I started studying gasifiers. I've watched them grow and have sentimental attachment to them.

http://www.gekgasifier.com/products/product-overview

Victory Gas Works (Woody)

These guys started up soon after GEK and got a kick start after being featured in a PM front page article. I didn't like these guys cause the principle seemed to be really intent on tearing down the GEK as opposed to telling you why his was better. And they are EXPENSIVE. Myabe good machines though, looking for input

http://gasifier.wpengine.com/

Vulcan

Totally new players. Looks simple enough and the price is good when compared with the others. Need input!

http://www.vulcangasifier.com/

LEAF

These guys are new as well but they look really slick and they are priced decently. Again, looking for some real experience and input!!

http://www.leafgenerator.com/

Hope to hear from you all soon!!
 
Marcos Buenijo
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Justus Walker wrote:I am a long time gasifier enthusiast. Enthusiast in the youtube, armchair type. Never done much more than a coffee can gasifier in real life. Now I want to get serious and start producing my own energy using a gasifier. I was wondering if any one had REAL life experience or could comment on the following models that are commercially available. I know that I do not want to build my own, since the techniques of tar cracking and high grade filtration are better handled by professionals, I think.


I suggest the Yahoo wood gas group and driveonwood.com for people with "real world" experience with wood gas engine systems. There are very few people doing this as you likely know, and even fewer who actually rely on it as a primary source of energy (while fascinating, it's not practical in the vast majority of settings). Myself, I've done nothing beyond extensive research and operating updraft units much like yourself. My opinion is that the GEK is the best unit available. However, I like the Vulcan design for it's simplicity and minimal restriction at the reduction (unfortunately, the hopper capacity is low). The Victory units are for people with money to gasify and burn. I bet anyone could build a unit with similar performance as the commercial units, but without fabrication experience and the necessary tools a lasting unit will not likely be had, and certainly not without spending a lot more time and money than required to purchase a good unit. So, I agree that purchasing a unit is the way to go for most people. NOTE: There are also the Garringer units, and there are some very small units in the works at offgridpro.com. Still, I think the GEK unit is the best option, but I recommend the base unit as their power pallets are overkill for residential scale.

There are good arguments against using a gasifier for power generation. The only setting I consider to be practical is a remote setting in a cold climate where suitable biomass fuel is readily available, solar insolation is poor, and where the waste heat from the system is put to full use. Somewhere like the back woods in WA state comes to mind, or Alaska. In the vast majority of settings I see photovoltaics as the superior alternative. However, in my view, if a person is in a remote setting, has plenty of wood, and can make use of the heat, then a wood gas engine system is hard to beat for genuine energy independence. I suggest daily bulk battery charging to a fairly high voltage setpoint with a three phase permanent magnet alternator via a bridge rectifier, Honda engine, and while using heat exchangers on the engine system for heating water. Store the water in insulated tanks, and use a hydronic heating system for space heating. Get a float on the battery once every week or biweekly, and a short equalization monthly. Note that I highly recommend against using the engine to generate AC power directly. I say design the system to operate at a constant output where gas quality and engine efficiency are optimal. Use an inverter for AC power. Load the system to equalize the battery (adding loads will reduce battery net charge rate and allow for moderating voltage at a high battery state of charge for proper equalization - this would have to be monitored by the operator, but it has to be done only monthly). BTW, there are voltage switches that can be configured for shutting down the engine during bulk charging, so bulk charging can be automated more or less.

 
Justus Walker
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Marcoss, Thanks for the reply. I agree with just about everything you say. I'll check out driveonwood.com! Thanks! I live in Siberia and we have a lot of waste wood of all kinds that I could gasify. We also have a very short solar day in the winter and an obvious need for as much heat as we can get from various sources. So, although I don't necessarily think that CHP is a prerequisite to gasification as a viable energy alternative, I will be setting up such a system.

Thanks
 
Marcos Buenijo
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Justus Walker wrote:Marcoss, Thanks for the reply. I agree with just about everything you say. I'll check out driveonwood.com! Thanks! I live in Siberia and we have a lot of waste wood of all kinds that I could gasify. We also have a very short solar day in the winter and an obvious need for as much heat as we can get from various sources. So, although I don't necessarily think that CHP is a prerequisite to gasification as a viable energy alternative, I will be setting up such a system.


Siberia with a lot of wood waste available?... yeah, a wood gas engine system seems ideal. A PV array seems a good idea to save wood and reduce engine run time during the warmer months. Note that PV hardware is a lot more affordable these days than even the recent past, and even Siberia gets good solar insolation for much of the year.


 
Abe Connally
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the Victoria gasifier is the best design I've seen. There are details on the yahoo group and drive on wood.

 
R Scott
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Abe Connally wrote:the Victoria gasifier is the best design I've seen.


That is a good looking design, but what do they make that lower nozzle out of? That one is going to be unobtanium to handle the environment for any length of time.

I have been toying with the idea, but I do not have a good feedstock source--everything is too small or too big--and I would spend more on pelleting or chunking than I could get out of a gasifier.
 
Walt Holton
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I am going to be building a small stationary gasifier this winter to run up to a 25 hp engine, harvesting the waste heat via water coils and jackets, however on a staionary unit I see cooling the gasses before they reach the intake manifold as the biggest chalenge to a small uint. I had an idea which probably would not work too well on mobile units (trucks) but may be a silver bullet on the stationary units, which would cool the gas in a small area and provide perhaps the entire filtering of solids need. My idea is... directly after the gasifier combustion unit, run the hot smoke through a bong (perhaps a 5 gallon bucket). I have two concerns with this strategy- 1) I do not know the dewpoint of the actual gasses which the engine needs to run, and would they perhaps be held in the bong water. 2) Re-condensing the vapor that would be added to the smoke, post bong. I think the second is less of a concern than the first and could be addresed with a small baffled chamber (aluminum would be best), with a drain bung, since the post bong fuel temp would be not too far from ambient air. Has anyone heard of, or had experience with a bong cooler/fliterer on a gasifier?

Walt
 
Abe Connally
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R Scott wrote:
Abe Connally wrote:the Victoria gasifier is the best design I've seen.


That is a good looking design, but what do they make that lower nozzle out of? That one is going to be unobtanium to handle the environment for any length of time.

I have been toying with the idea, but I do not have a good feedstock source--everything is too small or too big--and I would spend more on pelleting or chunking than I could get out of a gasifier.


the latest design had the funnel cast as ceramic, and the nozzle what just a hole through the ceramic.

Several of the earlier designs had metal nozzles and worked well. The advantage to this design is that tar production is virtually none. I think these were mostly used to run ~10hp engines.
 
Abe Connally
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Walt Holton wrote:I am going to be building a small stationary gasifier this winter to run up to a 25 hp engine, harvesting the waste heat via water coils and jackets, however on a staionary unit I see cooling the gasses before they reach the intake manifold as the biggest chalenge to a small uint. I had an idea which probably would not work too well on mobile units (trucks) but may be a silver bullet on the stationary units, which would cool the gas in a small area and provide perhaps the entire filtering of solids need. My idea is... directly after the gasifier combustion unit, run the hot smoke through a bong (perhaps a 5 gallon bucket). I have two concerns with this strategy- 1) I do not know the dewpoint of the actual gasses which the engine needs to run, and would they perhaps be held in the bong water. 2) Re-condensing the vapor that would be added to the smoke, post bong. I think the second is less of a concern than the first and could be addresed with a small baffled chamber (aluminum would be best), with a drain bung, since the post bong fuel temp would be not too far from ambient air. Has anyone heard of, or had experience with a bong cooler/fliterer on a gasifier?

Walt


I think Mother Earth News had an article at one time with a water filter like you are talking about. I think you'll have to run the bong water through a radiator or something, eventually, because it will get pretty hot.
 
Walt Holton
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Thannks Abe, I will look at Mother Earth and see if I can find that article. I was planning on using the bong for as part of the heat exchange cycle (and storage in an old water heater for space heat or aquaculture) because my intent is to have little or no losses of productive energy in the system, besides the friction losses in the engine which if I went totaly bonkers I could probably harvest as well. My two thoughs were to either coil copper pipe in the bong and circulate the water to harvest the energy or do a jacket around the bong (putting a big vessel around a smaller one) and exchanging that water to keep it cool. I think the key will be keeping that bong water as cool as possible to minimalize the vapor.
 
Abe Connally
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Walt Holton wrote:Thannks Abe, I will look at Mother Earth and see if I can find that article. I was planning on using the bong for as part of the heat exchange cycle (and storage in an old water heater for space heat or aquaculture) because my intent is to have little or no losses of productive energy in the system, besides the friction losses in the engine which if I went totaly bonkers I could probably harvest as well. My two thoughs were to either coil copper pipe in the bong and circulate the water to harvest the energy or do a jacket around the bong (putting a big vessel around a smaller one) and exchanging that water to keep it cool. I think the key will be keeping that bong water as cool as possible to minimalize the vapor.


I agree, if you can keep that water relatively cool, it would work well, but I would also use a cyclone and maybe a filter with medium in it, too. You really can't have too much filtering.

Also, the majority of heat will be around the woodgas generator itself. The hearth should be insulated, and if you can, coil some tubes for the air inlets (like the GEK) to help pre-heat your air. But, you'll have a surplus of heat around the unit, so maybe putting it in a basement or under a thermal storage would be a good idea. Of course, you'll also want to have water cooling on your engine, just to capture that heat, too.

The muffler from the engine can be routed through wood storage to help dampen the noise and dry your wood. Some of the charcoal guys route part of the exhaust from the engine back to the woodgas generator as a portion of air intake, because not only is that exhaust hot, but it contains gasses that are combustible (CO and H2).
 
Walt Holton
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Abe, thanks for the ideas. I have been thinking of putting it in a fireproof/ thermal mass room in the the basement the next home I build, but between then (gotta sell the current house first) and now it is time to brain storm, and study, study the physics behind it and observe sucess and failures. of working models. My profession is home construction, and the last number of years I have specialied in high performance construction/desigh/building science, with a balanced approach of energy conservation, occupant comfort, building durability and simplicity, and occupant health.
 
Marcos Buenijo
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Walt Holton wrote:Abe, thanks for the ideas. I have been thinking of putting it in a fireproof/ thermal mass room in the the basement the next home I build, but between then (gotta sell the current house first) and now it is time to brain storm, and study, study the physics behind it and observe sucess and failures. of working models. My profession is home construction, and the last number of years I have specialied in high performance construction/desigh/building science, with a balanced approach of energy conservation, occupant comfort, building durability and simplicity, and occupant health.


Hey Walt. I'm sharing some thoughts on these gasifier engine systems. I've heard a little on using water to filter the fuel gases. I recall there was only limited success in filtering tars. Oil has been shown to be more effective at catching tars. Perhaps there could be an oil "bong" with an external oil filtration and heat exchange system? The best option in my opinion is to seek a traditional solution. Select a design that has low or no tar, then filter the hell out of the gas. The Victoria unit was mentioned, and I looked into that design. I like it a lot, but I don't know where it can be purchased.

I've come to view these wood gasifiers in a particular way that seems to simplify things. I now consider them as charcoal gasifiers that process pyrolysis gases in addition to combustion gases. Charcoal gasification was mentioned briefly in a previous post. Air enters these units and the oxygen reacts with the surface of the charcoal to generate combustion gases (primarily CO2). The CO2 is then reduced in the high temperature carbon environment to form CO (the fuel gas). What little moisture is available (in the air or some water in the charcoal) is likely reduced as well to CO and H2, but CO is the main fuel gas produced here. It was mentioned that engine exhaust gases are sometimes introduced to a charcoal reactor (with the intake air). This is done primarily to moderate the extremely high temperatures in a charcoal gasifier, but it also increases efficiency significantly. After all, it increases the supply of CO2 to the charcoal. Since the reduction of CO2 to CO is endothermic, then it serves to reduce temperatures by converting heat to additional chemical energy in the form of additional CO fuel gas (an elegant solution to temperature control). Note that steam can also be admitted with the intake air to moderate the high temperatures, and this will increase H2 production.

With this in mind, now consider a wood gasifier as a charcoal gasifier. In a downdraft wood gasifier there is charcoal at and below the nozzles, and wood above the nozzles. When the wood gasifier is first started it is the charcoal that is ignited just as in a charcoal gasifier. As the temperature rises, then the wood starts to enter pyrolysis (gets converted to charcoal by releasing water and volatiles/pyrolysis gases/tar vapors). At this point the combustion of charcoal stops and the combustion of pyrolysis gases begins. Very little of the charcoal at this point is consumed in combustion, but is now consumed in the reduction of combustion gases (C + CO2 => 2CO , C + H2O => CO + H2). These reactions are endothermic meaning they consume heat to drop temperature, so it's extremely important to insulate against heat loss at the hearth. An important consideration is that wood contains such a high proportion of volatiles that it's difficult or impossible to combust all the pyrolysis gases generated. Therefore, the hot charcoal has the additional job of cracking tar vapors that are not incinerated at the nozzles. This reaction is also endothermic. So you see that keeping the charcoal at high temperature is a primary goal. If temperatures fall, then the likelihood of introducing tar vapors with fuel gas rises, and the energy density of the gas can fall (lower proportion of fuel gases generated). So, basically the task is simplified to considering a wood gasifier as a charcoal gasifier that generates it's own charcoal from wood real time (in situ), and the task is to keep the charcoal temperature high enough to ensure a quality gas. Other considerations beyond insulation include:

1. Making sure the wood is as dry as practical. Free water is very good at dropping temperatures.
2. Making sure the wood is properly sized to prevent bridging (make sure it flows well - if it gets hung up, then the charcoal can be consumed leading to excessive temperatures and poor gas quality - the wood fuel can then get freed up and fall on the hot charcoal and dump tar vapors through the system). So, wood pieces should not be too large and not irregularly shaped (fines, etc.).
3. Making sure the wood is properly sized to ensure good combustion of tar vapors. If fuel is too small, then the air may not penetrate the fuel bed and react with the available tar vapors. As much of the tar should be burned as possible at the hearth to achieve high temperatures and save charcoal for gas processing.
4. Air preheating. The hot fuel gases can be used to heat the combustion air to high temperature before it enters the nozzles. Since the volumetric flow rate of the fuel gases is higher than that of the air, then the air can be taken up to nearly the same temperature as the fuel gases - so a lot of heat can be regenerated into the system this way. Increasing the air temperature increases the combustion temperature. At first this process will increase the rate of wood pyrolysis. However, a new equilibrium condition will be established where the level of charcoal in the system rises. The result is that charcoal (an excellent insulator) will shield some of the wood from the heat and slow the rate of pyrolysis back down to the previous level. The final result is that more heat is added to the charcoal bed which enhances its gas processing ability. The result is a richer fuel gas and enhanced tar cracking ability. More charcoal is likely participating in combustion here, but the increased temperature adds to the tar cracking ability.

In my opinion, a good wood gasifier will be had by emphasizing these points: sizing wood properly, using very dry wood, sizing and positioning nozzles to penetrate fuel bed with air, super insulation at the hearth, aggressive air preheating, deep charcoal bed, running system within proper turndown ratio. Beyond this is the matter of fuel gas filtration which should be relatively simple with a good gasifier that makes little or no tar.

JMHO, as always.
 
Walt Holton
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Thanks fort the very detailed reply Marcos. It is going to take me a few times through it to get my head all the way around all you said, but even at first read it gives me a lot to think about. If science was presented as this interesting when I was a kid I probably would have paid a bit better attention.
 
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