I am excited to dig into the amazing world of alternitive sustainable heat and power production. I am fascinated with all the potential that woodgas holds.
I live in a verry cold climate (Canada) and have unlimited access to wood from our pastures (mostly white poplar). I currently literally live in my dads comercial Agricultural manufacturing shop with welding and CNC plasma, Laith, powder coating equipment, etc.
I am interested in designing a simple and reliable generator for a future off grid homestead. I would have use for heat and power. Simple low maintenance and bullet proof is my goal. I would like to buld and operate my own sawmil on said future homestead and as an off grid sustainable employment.
I would really love to know if anyone has done a serious comparison of steam vs woodgas systems as far as simplicity and reliability. Especially comparing heat and power produced.
Again, I would have unlimited access to trees for fuel. Remember if my system has excess heat this is not necessarily a downside as I could simply heat more outbuildings, have pamperd livestock, etc.
Thank you for all your input I’m quite new to all this. My one advantage is that I am a verry serious DIYer and have access to many tools.
Brett, Welcome to DOW. You will find lots of reading and research done on gasifiers on the forum here and in the LIbrary on here. Lot of guys on the forum will help you with your questions. Your available feedstock of wood and it’s characteristics as well as the engine displacement you need to run will frame your gasifier requirement. I am in a hardwood area and can’t offer suggestions your white poplar which is more like aspen. Several guys on here are familiar with aspen and popple. Soft woods have different burning and ash considerations. There ae a few Canadian members on here that should reach out to you also.
Welcome Brett! I have done a ton of research on steam vs woodgas. Steam was my first love. Unfortunately as Don hinted it’s just not very practical.
Thermal efficiency is your main issue. The latent heat of boiling water means that you spend an enormous amount of energy getting the water to become steam, beyond what it takes to simply heat it. That latent heat is only released during condensation, which must happen AFTER you are done using it in the engine. You can reclaim some with heat exchangers but not much. Overall your efficiency will be down around 3-5%. Of course if you have a use for the waste heat it’s not nearly as bad. So this will only make sense as a CHP system (combined heat & power).
All that assumes you are capable of building and maintaining two very different machines - a steam engine (expander) and a steam boiler. Engines are simple enough, if you have a full machine shop at your disposal, although depending on the design you can lose or gain efficiency here. The real bear is a good efficient and SAFE boiler. If you simply heat hundreds of gallons of water like an old steam locomotive (water tube boiler) you have built a bomb that you are praying will not ever go off. If you try for a monotube boiler, you have less danger but more complexity and difficulty in controlling it. Solid fuels like wood are not good for monotubes, because they can’t be switched on and off quickly. Even if nothing explodes, you are at high risk for extreme scalding and burns from superheated steam.
After thinking through all that, a wood gasifier is pretty attractive. Upwards of 30% thermal efficiency, no explosive potential, 4-stroke engines which are commonly available, cheap solid fuel burned in a controlled on/off fashion. It’s the best of all worlds, in my opinion.
The only real danger here is CO poisoning, we make large amounts of it and you should be very careful not to breathe the gas. I also recommend avoiding fumes from diesel, gasoline, kerosene, and superheated steam… the point is any energy/fuel source has danger. This one is very manageable with some basic precautions.
Always glad to see any interest in any kind of alt energy. As you know this is DriveonWood but also power on wood. Many of us just run generators on wood gas and no vehicles. You will not be able to convert your wood fuel to steam and run a vehicle. And there is no real advantage to converting your wood to gas and then using it to heat water to produce steam. However there is something so attractive about steam power that it cannot be totally ignored. Here is a video of a steam car. If you look on youtube Jay leno has several videos about his various steam cars and they are all pretty amazing. Look at the craftsman ship and and style of all the components on this White steam car from 1909. 40HP but up to 800 ft pds of torque. That kind of force is mind boggling. However for your stated purposes, a style of your choice wood gasifier will be your only viable option for self sufficient power. Only way to get enough rpm to produce generated electrical power would be with a turbine and even with your well equipped shop you aren’t likely to make one of those. You may have looked around the site enough to see that stationary power gasifiers can be very simple or quite complex depending on your fuel source and how much time and effort you want to put in to keeping one operating. None of them are truly walk away as far as I know other than MattR’s commercially produced units. Dave in Australia gets hours of run time from his system and no one else that I can recall has commented much about how long they can run between checking on the operation. I, for instance, normally only run my system when I am working at other things in the vicinity. I feel the need to listen to the engine and know how it is performing. Of course I have not done this long enough to be real confident about what is going on. Also unlike off-gridders I am mostly experimenting with emergency grid down occasions and future no grid conditions. Still you will find your niche as all of us do and we will be glad to help and learn from your efforts in return.
I have similar goals to what you describe and have built high efficiency steam expanders with monotube boilers and gasifiers too.
Good advice being given here and great summaries.
The short answer is gasification is the way to go:) And because you say you want, “Simple low maintenance and bullet proof is my goal.”, and you have abundant fuel, I would say you want charcoal gasfication.
I’ll repeat what others have said about 'Why Not Steam?";
**no off the shelf expanders available
**no off the shelf mono tube boilers (and you do want monotube for safety)
**no off the shelf stoker burners for biomass (you need a stoker for long run times)
**The Rankine cycle is inherently inefficient compared to Otto because of latent heat AND because of Carnot and steam’s low peak temperature
With enough time and money, steam could be done with both safety and moderate efficiency, but it doesn’t compare to the ease and economy of gasification.
With a little prep work, you could literally buy and assemble a working charcoal system in a long weekend; from charcoal making to a running generator.
There are gaps in the trees to electrons chain but they are not terribly difficult to overcome (charcoal grinders for example).
There are some very experienced wood gassers around here that have a lot more experience than me, but my crude (and always changing) charcoal system has these numbers:
**10 hour unattended reliable run time
**33 gallons of char consumed (1.33 lbs/gallon) in that 10 hours
**40 gallons of hot water produced from the liquid cooled nozzle
**500 gallons of charcoal in a day using the flame cap method
**500 gallons an hour through my 12 inch grinder
**a very dirty operator:)
What is missing for an ideal solution:
**charcoal making stoker furnace to heat dwellings and water that also captures charcoal
**engine optimized for char gas (high compression, slow speed)
**various material handling, dust control, fire safety, and convenience mods
If fuel is abundant and your electrical needs are modest, I think a char gas system can be reasonably practical.
Using the poor quality charcoal I make and the very inefficient engine I run, 1000 gallons of char (which occupies a little more than a 4x4x8 box) would give you 300kwh electric, a lot of domestic hot water, a great deal of space heat if you could capture it, and a lot of room for improvement.
As a benchmark, 300kwh is the annual consumption of a modest refrigerator.
Oh, and I’d guess the all up cost of my ‘system’ is less than $4k.
Edit: another example for reference;
A friend lives in a small house with wife and child. They have wood heat and use propane for cooking and hot water. He works from home on the computer a few days a week. They have normal kitchen appliances. They use 260kwh a month for months that they don’t run the AC.
Hi Chuck. I am impressed with your numbers. I will have to try your flame cap retort. I cannot make nearly that quantity of char per day. The forty gallons of hot water from your nozzle is also appealing. Even without a large battery bank, anyone should be able to live well on your electrical output. It is good to see data. I have a water heating, space heating, charcoal producing heater I built for my greenhouse that promises to be very efficient. I am hoping it will heat a 600 gallon built in concrete water tank in the GH. I keep losing water out of the tank and haven’t located the source yet so I haven’t been able to fully test the heater out. Things keep coming up that always seem more pressing. I’ll have to get back on that and post some video.
I too want to do something similar. I would encourage you to look at the thrive offline page here on the forum. I have been impressed with Matt’s work and I have talked with Gary Gilmore about his simple gasifier.
There are tons of builders around here with a lot more experience than me so be sure to investigate broadly:)
The 10kwh per batch run is my best result from the 55 gallon drum setup. The run time and power produced are directly proportional to the quality of the charcoal. I make the worlds worst charcoal (on purpose) and use the worlds worst generator (for now, on purpose), in order to establish worst case scenarios since one of my use cases is ‘zombie apocalypse’ prepper thinking.
When I make flame cap charcoal from wet old junk picked up out of the mud I get 1lb per gallon (1/2 inch grind) and the run times are about 8.5 hours using 33 gallons of charcoal with a 1kw load.
When I make flame cap charcoal from better sources, I get 1.3lbs per gallon (1/2 inch grind) and can get 10 hour run times, same 33 gallons and 1kw load.
I haven’t tried it yet, but you can safely assume that quality retort made charcoal would yield better results.
The generator is a Chinese 196cc Honda clone, 3600 rpm. No mods of any kind other than plumbing in the char gas. (unless you count an electric drill starter setup)
Not that I recommend such a generator!! Truly worst case…
Here is a nugget of wisdom from @SteveUnruh to consider;
“Looking back at the last 7 years I see the most relevant factor to whether a person will join the one in a million who woodgas for usable engine power isn’t their skill as a welder fabricator,
their ability to do the maths,
follow along the thermal-chemical process
It really is predictable by their ability to Source, then Process, and then Maintain a wood fuel pile that will diminish at, at least a 200 pounds a day used-up rate.” http://forum.driveonwood.com/t/are-you-a-one-in-a-million/488/16?u=chuckw
It’s easy to get seduced by the novelty and possibilities of biomass to power (and most of us around here continue to be), but the gritty, dusty, sweaty, reality will weed out the casual observers:)
Wrap your head around at least 200 pounds of fuel a day of gathered, chunked and stored dried wood. Nobody is going to get the 24-7 power they are so accustomed to and take for granted now. As Chuck says, “gritty, dusty, sweaty, reality.” A whole new mind set has to be nurtured. My view is that you may be able to run a power plant six to eight hours a day. Even that seems daunting to me but MattR runs his fab shop at least that long so it must be doable. During those hours you do your major work and with some kind of battery bank you should be able to keep a fridge and lights going for the rest of the time but what happens if you are down with the flu for a few days to a week and can’t process that fuel? The food in your fridge and freezer will spoil. If you are using the system for waste heat your pipes may freeze in the winter. I don’t think the average person knows how much work it is when they try and separate themselves from the system. Worth it? You bet.
This is why I would pair a chargas generator with solar and batteries. The amount of wood you need to process for a 300-500 kwhr month household is insane, and that’s low for most homes in the US which average 800+ kwhrs.
In the winter when solar power is low you cogen heat and electricity with the chargas. In the summer, no generator except on a second or more rainy day.
The solar and batteries cost a lot more though, at least $5k for 10khrs of battery and panels to charge them.
Good description Tom.
Fuel processing, storage, and handling seems key for long term viability. Grappling with those realities will really put things in perspective.
So much of this is without definition, ‘how high is up’?
I suspect you would define your lifestyle by your available fuel. If you could make and store a thousand gallons of charcoal in a day (a month’s supply at 300kwh, worst case), I think a threshold of convenience would be crossed for me.
@abreaks, I think you are right about layering your power sources. Solar and a battery bank are a no brainer and work well together with biomass. Solar is strong when fire season starts up… (starts humming “If I were a rich man…”)
It can be hard to think clearly about all the variables with gasification, and even harder to discuss it, as nobody has identical circumstances or goals.