the original article is here
4 Reasons for Wood Gas
- Abundant Biomass
- Wood Is Carbon-Neutral
- Biochar to Enrich Your Garden
- Energy Independence
Modern trucks with multi-port fuel-injected engines convert better to wood gas.
see video here.
It cuts on an ascending bevel so that every revolution of the drum slices off a roughly 2-inch chunk. Keith and his wife, Lisa, lay out the chunks on tarps so they will dry in the sun. After the chunks are dry, Keith stores them in old feed sacks, several of which are easy to keep in a truck bed. The chunker is powered by a thrifty two-cylinder diesel engine. One hour of work can cut and spread up to 2,000 pounds of wood chunks suitable for driving (after drying).
16 pounds of dried wood to take the wood gasification truck as far as 1 gallon of gasoline would (21 miles in conservative driving). So one hour of work with Wayne’s chunker produces the equivalent energy value of 125 gallons of gasoline (a value of $437.50 if gasoline costs $3.50 a gallon) that Wayne can use to travel 2,625 miles. In Bransby’s 2010 tests, the Dakota achieved 21 mpg on gasoline and 29 “mpg” on wood gas.
Like any typical wood gasification system, Keith’s setup has three basic components: a gasifier, a radiator and a filter.
The wood gasifier consists of upper and lower chambers in the form of drums connected in the middle by a heavy spacer. The upper drum is a lidded hopper where the wood chunks are held. There is an internal air inlet manifold that introduces oxygen a few inches from a restriction, which causes a high temperature (about 2,700 degrees) to be created in a small environment. This is where the gasification takes place.
The hot gases go from the gasifier to a heat exchanger, where the gaseous fuel is cooled with fresh air. The incoming air piped to the gasifier’s inlet never comes in contact with the exiting fuel gases.
Next, the gases go to a radiator, or cooler, which Keith has skillfully camouflaged as a bed rack. There are two inlets and two outlets, so each side of the rack has cooling capacity. Here, the gas temperatures drop below the dew point, and the condensation drains into small tanks.
The third component, the filter, is simply a clamped-lid barrel filled with hay. This removes most of the particulate matter contamination in the wood gas.
After being cooled and filtered, the wood gas is pulled through two branches of PVC piping to the engine compartment. Homemade “slingshot” filters separate any remaining moisture and particulate matter from the incoming gas stream.
The cooled, clean wood gas is directed to fittings Keith has installed in the engine’s air cleaner housing. Two inlets are dedicated to fuel gas and two to fresh air, which is drawn in through separate canister filters. Each of the four inlets includes a butterfly valve that Keith adjusts manually with controls on the dash.
Operation of the vehicle
In preparation to start the Dakota, Keith flipped the switches on a pair of small in-line bilge blowers and opened the gasifier lid to reveal remnants of cold char in the tank, which he ignited with a propane torch.
“With a poker rod I make a little void that goes down to the center of the hearth,” Keith says. “I’ve got those blower switches fixed to where I can either blow or suck the air through to get the wood going.”
After pouring a sack (about 12.5 pounds) of dried wood chunks into the chamber, he sealed the lid and started the truck on gasoline. We drove about a quarter of a mile on gasoline, then he switched over to wood gas with the touch of a lever.
“On this truck, I’ve got a sensor and gauge that monitor the exhaust gas, telling me if it’s too rich, too lean or just right,” Keith says. “I’ve also got vacuum and temperature gauges — sort of like a doctor’s stethoscope and blood pressure monitor — that let me keep an eye on what’s going on. Since wood gas is slow-burning, it helps to advance the timing a bit. The older Ford does that with a cable, but the newer models are smart enough to automatically adjust to the fuel.” Keith says the vehicle performs slightly better on crisp days, when humidity is lower. Keith sized the Dakota’s wood gasifier to allow 50 to 75 miles on one fill.
- Choose a truck with ample room under the hood, as well as around the engine and chassis.
- Electronic fuel-injected engines have streamlined air intakes, which convert better than carbureted engines.
- Multi-port fuel injection is preferable over throttle-body injection. Generally, trucks built after the mid-1980s use fuel injection.
- Large-displacement engines have more power and give better results on wood gas.
- High compression improves performance with wood gas: It burns slowly and has great antiknock qualities. Wood gas supports a compression ratio of up to 16:1.
- It is possible to convert diesel engines to use wood gas, if given the correct compression ratio. But the injector pump has to furnish the ignition with at least 5 percent diesel.
- Ignition timing should be advanced because of the slower-burning gas. Modern engines with electronic ignition will automatically advance the timing.
- It takes about 200 to 300 hours to convert a truck to wood gas. Keith’s record-setting Dodge Dakota took 250 hours of work.
- The cost of materials to convert is about $500. Many components can be found free.
- Tools needed: basic mechanic’s tools, a sheet metal nibbler, a metal-cutting reciprocal saw, a power hacksaw, a drill press, a cutting torch, small wire-feed welder, a solid workbench, and a sturdy vise.
- The gasifier should be built to match the size of the engine and its airflow volume.
- The size of the wood chunks affects engine performance. Smaller chunks react faster and give better performance, but the fuel is consumed faster.
- Hardwood has greater energy density, and thus delivers more range per fill, than softwood.
- Ongoing maintenance: flushing the cooler and draining the condensation traps every 2,000 miles. Ash residue should be removed every 1,200 miles and the filter medium changed once a year.
- Moisture content of the wood chunks should be less than 25 percent.