Introduction: Charcoal Powered Generator - Gasifier
Ask any farmer, survival expert, Boy Scout, hippie or prepper and they will tell you the awesome uses for charcoal. From improving your garden to filtering water and field medicine. But did you know with a few scrap parts you can run an unmodified internal combustion engine?
I've been interested in alternative energy for a long time. I wanted to find an inexpensive, scalable option that could work in virtually any inhabited part of the world. People are smart and creative. I knew there must be something out there. After lots of searching I found a very cool theory. It was not on a fancy tech blog or news conference. I found my answer in a grainy video on YouTube. An older man wearing dirty bibbed overalls who introduced himself as "Gary from Pennsylvania" He had a new take on a very old idea: Charcoal Gasification. I found this both brilliant and fascinating because I had been considering building a wood gasifier for years.
Following a rough outline of what I could see on his video I was able to build a functioning proof of concept using mostly junk parts: A metal 5 gallon bucket with lid, random valves and pipe fittings and a piece of PEX. Obviously my first try was raw and intended for rapid prototyping - but it worked, it was cheap and it was fast. I successfully ran an unmodified internal combustion generator engine purely on the gas produced by burning charcoal.
This has the potential for many benefits on the modern homestead, those to start freeing themselves from petroleum dependance, powering the remote cabin in the woods, pumping water to life sustaining crops, or mowing your lawn if gas ever hits $5 a gallon. However, for me one of the most exciting aspects of this project is the potential to increase the quality of life of the disenfranchised, the forgotten people of war torn countries, those living in poverty in a far away villages. Those who are a world apart removed from my aggravation when "my seat" is taken at the local coffee shop. Away from my First World Problems. I have friends who go to the far corners of the world to teach indigenous peoples new low impact, high yield environmentally friendly framing techniques. I want another carbon neutral tool for them to use.
I've included a video here to show you my raw unedited first run. The audio and video quality are not great - but you can share my "hey cool it works" moment.
Step 1: Wood Gasification As Fuel Is Old Technology
The science and history:
Caution I'm not a physicist but I play one on the internet.
Wood gas, syngas, gasification, producer gas. All words that describe the same idea. Turning some sort of organic biomass in to a harnessable useable fuel source.
The general idea: Biomass, if burned in an oxygen low (controlled) environment will produce (mainly) hydrogen, carbon monoxide, carbon dioxide, tars and bio crude. Laymen's terms: If you burn wood the right way you get flammable smoke! That gives a new meaning to the term smoke bomb...
The roots of gasification run deep into the history of industrial man. The flammable vapors were piped into homes and street lamps in the late 1800's before being replaced by Natural Gas. Wood gas generators were strapped to literally thousands of vehicles and machines across Europe during World War II when petroleum based fuels were in extreme demand. Rumors have it that North Korea still uses wood gas as fuel.
One could write a doctoral thesis explaining exactly what is going on. So I'll leave the heavy lifting to the experts. Check out some of this research:
Research, Research, UN Research, Research with fun pictures, Vintage Research, 130 pages of light reading
Step 2: Wood Gasification Vs Charcoal Gasification
There are a lot of wood or bio-mass gasifiers plans out there. They span the range from backyard hack jobs to shiny massive industrial commercial units. Even FEMA has plans for you to build your own. This is probably my favorite DIY FEMA build - his video is worth watching.
For me wood gasifiers have a few inherent issues to overcome.
- DIY wood gasifiers are complicated to build for the average joe and includes a good amount of welding.
- Commercially available units are awesome but expensive - and not available world wide.
- Wood gasification produces bio-crude - that if not cycloned, removed, and filtered properly it can enter your engine.
Bio-crude, quite literally a heavy oil or tar, is made by a process called thermal depolymerization. "Under pressure and heat, long chain polymers of hydrogen, oxygen, and carbon decompose into short-chain petroleum hydrocarbons" Burn bio-mass properly and you get oil that can be refined into gasoline just like the crude oil found in the ground. Some people find very creative uses for bio-crude or tar. (There is much talk about algae based bio-crude - keep your eyes out for that!)
Bio-crude is cool unless you are piping it into your engine's carburetor. Then it will just reduce the life of your engine.
The process of making charcoal however has already removed those long chain polymers. So, when you run your gasifier on charcoal - you just produce vapor and no tar. Charcoal is extremely easy to make using two 35 or 55 gallon barrels - but I cheated and prototyped with a bag of store purchased "all natural lump charcoal".
Step 3: Proof of Concept From Scraps
I started my gasification journey with a bucket, a paint can, house project scraps and a tool box full of free 2nd hand pipe fittings.
For this style build you will need a few things.
- metal container with locking lid that has a gasket
- Filter canister and filter medium. I used a paint can and some foam rubber I found.
- Scrap metal plates - I used 16ga
- Pipe fittings - the majority of mine were 3/4 inch black steel pipe. Beware of galvanized.
- Intake piping - I used pex initially. This was a bad idea.
- Exhaust gas recirculation piping. Check out Walker 40000 flexible exhaust pipe. It has a 1 inch ID which fits nicely over a 3/4 inch black steel pipe. In stock at most O'Reilly Auto Parts. Sold by the foot.
- Ball valves. You will need at least one. Two if you use the exhaust gas recirculation. Three if you want a flare off. Four if you want to use a fan motor to start the charcoal fire.
- High temp RTV. I found a full calk gun tube at O'Reilly Auto Parts for $2 more than the 3oz size.
- nuts and bolts
- Welder or JB Weld epoxy
- Pipe wrenches
- Step bit or really huge drill bit
- Outdoor work space
- Carbon monoxide detector
Step 4: Generator
My father dropped off his low hour RV generator for fuel system repairs. He was a convenient victim to my mad scientist experiment. This is a 1985 Onan 3.0 with just under 300 hours. It has spent its life tucked up under a very cool Toyota based motorhome. It sprung a fuel pump leak. After I resolved his issues it was just calling to me. It was the perfect candidate for a gasification upgrade. The biggest task was leaving the generator so that it would run on gasoline or charcoal gasification.
I rigged up a metal outlet cover as a threaded mounting bracket for my adapter. Basically you need to figure out how to get T fitting on your carb. One side goes to the carb, one to the fresh air intake ball valve and one to the gasification reactor.
The exhaust was also fitted with a T and a ball valve. One side of the exhaust went to the atmosphere while the other side would be plumbed back to the fresh air intake of the reactor. This would provide a path for some of the unburned carbon monoxide to find its way back into the reactor while also acting as a fan to the flame. Smarter people than me say this is a helpful feature. I've seen these gasifiers run both ways. I think I had a flaw in my return line design.
Step 5: Reactor
The reactor was easy to build. I will say that my air inlet pipe was too low. Please put yours at least 2 inches up from the bottom of the bucket.
These are the steps I made up to build the reactor.
- Cut 3 equal sized pieces of 16 ga metal. One for the exhaust side, two for the inlet side.
- Bend the two inlet pieces of metal to the general curve of the bucket. One will go on the outside and one inside for support.
- Vice both inlet pieces of metal and drill holes in each corner. Clamping each hole with a bolt before moving to the next.
- Drill holes and bolt both to the bucket. One inside, one outside.
- Drill a pilot hole for the air inlet pipe through both plates and the bucket.
- Use a setpper bit drill a hole just large enough for your inlet pipe. Check fit often. Drill through both plates and bucket.
- Place inlet pipe into bucket so that it fits more than 1/3 but less than 1/2 way into the bucket. I used a screw on stainless fitting on the end of my pipe. It was cut to length and the stainless stands up to the heat better than black iron pipe. Weld inlet pipe into place. (*edit - not stainless. See the fail photos at the end!*)
- Remove both plates.
- Put a generous amount of high temp RTV between the outside plate and the bucket. I also put RTV around the weld for good measure.
- Bolt both plates to bucket.
- Weld 3/4 inch fitting on to the 3rd piece of (unbent) metal.
- Drill out hole on underside with stepper bit.
- Drill a hole in each corner
- Place on bucket lid and drill outside corner holes - securing with a bolt after each hole is made.
- Drill center hole out after top plate is bolted to the bucket lid.
- Remove bolts and plate noting the orientation to ensure proper fit. I made an x with a sharpie on the plate and the lid.
- Put a generous amount of high temp RTV on the underside of the top plate. Bolt to bucket lid.
Let the RTV cure for 24 hours.
Step 6: Filter
Charcoal gasifiers are considered updraft gasifiers. Meaning the air is brought in form the bottom of the reactor, burned and the escaping gases are vented through the media (unburned charcoal) and out the top of the reactor. Charcoal is also extremely dusty. Dust particles can hitch a ride on the outbound gases and find its way into your engine. The dust can be stopped with a simple filter.
In this case I used a paint can, two bulk head unions (that I found in that box of parts) and some packing foam I found at work that was getting tossed.
I cut holes in the top and bottom of the paint can for the unions. I added RTV for good measure even though it had a hefty gasket.
The foam was cut into circles and smushed in to the paint can.
Step 7: Charcol
Charcoal needs to be all natural "lump". Hard wood is preferred but softwood will work - it will just burn out faster. You can't use the pressed, chemically treated "ez" light.
You can buy a bag for testing purposes, but I would highly recommend making your own if you want to do this for more than just an experiment.
Charcoal pieces should be more than 1/8 inch but smaller than 3/4 inch. As I understand it this will maximize your air flow while providing carbon dioxide scrubbing goodness.
Step 8: First Run - Smoke Em' If You Got Em'
I really had no idea what to expect. My 30 year old generator was only started once in the past 15 years. It was cold and raining but I was very impatient. I had to know if this thing worked.
I took a lit propane torch and placed it on the tip of the air inlet on the reactor and let it sit there. I closed the fresh air intake ball valve and hit the electric starter on the generator.
The suction of the engine pulled the flame of the torch into the reactor lighting the charcoal. Shortly I had a very hot fire burning which produced a good amount of gas. I sprayed the air intake with a hit of starter fluid to help the process along. Did I mention it was cold and raining?
I continued to crank the engine while adjusting the ball valve on the carb fresh air intake. I finally found the right mixture to allow the engine to run by itself. I was successfully able to run a reciprocating saw off my outlet. After about 15 min I shut it down because I had too many leaks.
Gary says he gets about 30 min from 1 gal of charcoal on a 5 hp engine. I have no clue what horsepower this engine was but I burned very little in my first 15 min run (or subsequent runs).
On that note - please be careful. These gases are dangerous in under the right conditions. Carbon monoxide poisoning can kill you if you are exposed long enough. Carbon monoxide (CO) will attach it self to the oxygen molecules in your blood which leads to poor oxygen absorption resulting in organ failure. Failure to operate a device like this in a poorly ventilated area could bring permanent personal injury or death.
Step 9: 2.0 Revisions
Version 1.0 was a complete off the wall proof of concept that worked - but it leaked.
Version 2.0 saw a few upgrades.
Carb adapter plate. I tapped a 3/16 piece of flat steel with a 3/4 inch pipe thread and two bolt holes. Utilizing the paper gasket I already cut this stopped all the leaks at the carb from plate flex. I attached the other bracket for good measure to keep the weight of the iron pipe from pulling down on the carb.
I also removed the pex pipe. That was a bad idea. It melted at the bucket and I did not have any pex clamps on it. In an effort to save a few bucks I just removed the exhaust gas return line and put it on the intake side. I was very fortunate the 1 inch inside diameter pipe fits very tightly over a 3/4 inch black iron pipe. If you turn it one the flexible line loosens enough to slip over the pipe fitting - a gentle twist the other way and it locks down like a Chinese finger trap. Exhaust style u bolt clamps would be recommended.
No more leaks!
Step 10: Pop a Cap
Combustion needs three things: Air, Fuel, Ignition. (A special thank you Mr. McNeese in my 1st year of high school auto shop class- see I was not completely tuned out!)
A charcoal gasifer has plenty of heat (ignition) and fuel (charcoal) so the only way to put it out is to remove the air from the environment. This is easily done with metal caps or valves.
I caped and left a very hot reactor over night and the next morning it was cool to the touch and not smoking.
Step 11: Opportunities for Improvement
Compression and storage
All results are data and not all of our hypothesis are correct. I theorized I could compress it, store it in a propane tank and burn it on an outdoor burner. (Think grill, turkey fryer, stove or eventually Coleman lantern). I successfully compressed the gas I produced but I was not able to light it in said stove. I think that if would light in my engine - it would light by itself. I blame my cheap leaking Harbor Freight 12v compressor. I'm not sure it had the ability to draw the volume needed to stoke the fire properly. I would very much like to try this with a larger compressor and see how it does.
Materials and design
This fire was HOT! I though I had a piece of stainless that I cut to length for my fresh air intake. It was actually some sort of cheap shiny chrome looking metal. It melted into large blobs in the bottom of my bucket. Cool - but not working as intended. I would also move my intake pipe up 2 inches from the bottom of the bucket to allow for a larger reaction zone and ash bed.
This is my dad's generator. He is coming by tomorrow and I'll have to return it. If I continue to pursue this further I would like to build a rapid prototyping lab. I have a 1971 John Deere Kohler motor with electric start and a bad carb sitting in my workshop. I think mounting this on a cart with a battery would be advantageous. I would like to find a more universal platform that would allow for the utilization of different implements other than just a generator. Belt driven water pump, hydraulic pump, fan, alternator etc.
Charcoal production and refinement
I don't have a charcoal production and processing set up at my house. I can see a real potential for me to utilize a charcoal gasifier. I already burn wood for heat so I have it on my property. I just need a few barrels and a way to properly screen charcoal sizes. Gary Gilmore from PA has a few videos on his awesome setup.
Third Prize in the
MAKE ENERGY: A US-Mexico Innovation Challenge
First Prize in the
Burn It! Contest
Participated in the
Explore Science Contest