Wood, the Alternative Energy for the Rest of Us, by Bill S.

Wednesday, May 27, 2009

Solar and wind electric generation systems are affordable and efficient, but there are a many areas of the U.S. where wind systems are not feasible, and few localized areas where solar systems are not feasible. A diesel powered generator with a large underground tank is reliable, but under adverse conditions the tank could run dry. Fortunately there are two systems capable of generating electric power with wood, a fuel readily available in most parts of the country.

Gasification is a process of burning wood or other solid biomass in a specialized combustion vessel (basically an upside-down wood stove) that generates hydrogen and carbon monoxide (CO) gases as by-products of the high temperature combustion. The exhaust gases can then be used to fuel an internal combustion engine. Gasifiers were used across Europe during WWII to power tractors, trucks and buses when gasoline was not available. The return of gasoline after the war caused gasification to drop off the radar. A group of American pioneers have revived the technology and made great strides in bringing this lost technology back to the market.

All Power Labs in California sells do-it-yourself kits and complete gasifier systems, known as gasifier experimenter's kits (GEKs). GEKs have been used to power cars and generators, it is potentially a complete solution. GEKs are operating around the world. GEKs is an open source project, that is, the plans are free and users are encouraged to experiment and share their knowledge. The design and operation of the gasifier requires wood blocks/chips, pellets or similar sized fuel. Split firewood is not an option when operating on a small scale.

The other option is small scale steam. Steam engines powered the industrial revolution and were in use well after the advent of petroleum products and the electrical grid. Mike Brown in Missouri manufactures a range of small scale steam engines, from 1-to-20 horsepower.

Operating a steam engine requires specialized knowledge and skills, steam is dangerous in inexperienced hands. Mike Brown has a package of instructional materials for sale and will insist you do your homework before purchasing of one of his engines.

Steam engines require a boiler to generate the steam to drive the engine. Boilers can be made from copper tubing and junkyard scrap for a few hundred dollars providing there is a metal worker in the neighborhood; plans and a how-to video are available from Mike Brown. ASME-certified boilers are available in limited quantities.

Both systems will generate electricity when gasoline, diesel and propane fuels are unavailable, the sun isn't shining and the wind isn't blowing . These systems are best suited for short term backup power or as a supplement to a solar/wind system. Neither system is “off the shelf” ready, they both require back yard engineering skills and American ingenuity Both systems require a stock of wood or other solid fuel to operate for any extended time. They both require tending and maintenance. Relying on steam or gasification for a year-round supply of electricity for a retreat is unrealistic in most cases . Note however that life in the future may become very unrealistic.

But will these systems power a retreat? If you had a 3 hp steam system the answer is yes. I did some rough calculations; in which I could be off by ±25%. I am assuming a battery bank for storage. A 3 hp system steaming for 6 hours per day for a month would generate approximately 400 KW. For comparison, 400 KW is less than one half of what the average American household uses in a month, but far more than most solar or wind systems will generate. We get by on less than 400 KW per month and the retreat is all electric, including hot water, range and refrigerator and I run many power tools in the shop. 400 KW is a huge amount of electricity in terms of the creature comforts it can provide. Under emergency conditions 100 KW/month would drive a well pump, laptop, lights, radios and cell phone chargers.[JWR Adds: Don't forget that when drawing DC power from a battery bank, that inversion to AC with a modern inverter is about 80% efficient in typical use, and they can be about 90% efficiency under optimal conditions. To understand the concepts of kilowatts and kilowatt hours (KWh), see Wikipedia.)

If oak were used for fuel it would take 13 cords of firewood per year (that is a lot of wood). At $225 per cord it would cost approximately $3,000 per year plus many hours of manual labor. This is not what the modern American considers convenience, but under lock-down conditions you may be the only one within 100 miles that is powered up after a week. Under emergency conditions you will be at home with enough time on your hands to stoke the fire every hour. I have not done a similar analysis of the gasifier. A gasifier is a very efficient use of biomass, I would expect you can achieve much the same results as a steam system. GEK users will be happy to share what they know.

Gasifier
Pros: Technically within the range of the do-it-yourselfer. Will power many internal combustion engines. Will burn chipped/blocked wood and forest scrap, walnut shells and more. Waste heat from the gasifier and IC engine can be used to heat water (which can be used to heat a home). The exhaust gas from the IC engine is water vapor and there is no smoke, the smoke has been converted to a combustible gas.
Cons: Requires small, consistent-sized fuel such as dry wood chips. Generates carbon monoxide (CO), a deadly gas although this gas can be used to fuel an outdoor stove. Cannot be installed within a living space (same with steam). Limited supply, however plans are free and a gasifier can be built with scrap steel and junkyard parts by any welder/metal worker.
Cost: Approximately $1,000-3,000 (not including engine, generator or storage batteries).

Steam Engine
Pros: The most reliable and simple of backup systems. Quiet. Steam can be used for multiple purposes including space and water heating and making bio-fuels, including alcohol. Can be powered with both solid and liquid fuels.
Cons: Requires a good bit of self-study. Potentially hazardous. Limited source of supply for engines and boilers although both should last a lifetime and be worth their weight in silver should it come to that.
Cost: Approximately $7,000 for 3 hp engine and boiler (not including generator or storage batteries), the greater part of the cost for a manufactured boiler.
Steam engines are precision machines available in limited quantities. Cost aside, it could be months before you take delivery, but remember patience is a virtue. If time and money is of the essence then the GEK is the best bet; a team of garage mechanics could have a GEK up and running in a week. GEKs can be manufactured from plans without royalties, potentially a great business opportunity.


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