Steam Powered Wood Chipper

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Basic concept: a steam engine is directly (mechanically) coupled to a wood chipper. No electricity is generated. The whole purpose is to process wood. A portion of the wood chips is used to power the steam engine. The heat-producing unit relies on pyrolysis rather than combustion of biomass. While this lowers the yield significantly, it generates biochar as a valuable by-product. The char can be sequestered in local soils or be transported via ropeway. Modular design is certainly a possibility, whereby the a steam power cube would be hooked up to a chipper module.

The steam engine can be switched over to hydraulic output, driving hydraulic motors and allowing hydraulic implements to be run, such as:
- pulley of steel ropes that are used to pull large branches and logs to the machine
- chainsaw to cut logs into smaller pieces
- hydraulic log splitter
- electric generator, can power electric chainsaws and lights to work in darkness
- perhaps other GVCS elements such as The Liberator
- superheated steam (with heat recovery) to instantly dry biomass, for more efficient energy use - Spader to sequester biochar in soil

The steam engine's boiler may also generate some superheated steam that is used to quickly dry the wood chips. Heat recovery (to heat more water for the steam engine) can make this very energy efficient. Alternatively, wood may be dried with hot air only.

Conversation with Kevin Chisholm, Biochar Yahoo! Group

Kevin: "While this is a great concept, the drawback is the requirement for a skilled "Boiler Operator". If the Skilled Operator obstacle is overcome, then it is indeed a good system.

Wood can be pyrolysed on site, to generate large volumes of char, with all pyrolysis gases being burned to eliminate smoke and pollution considerations. The steam power can indeed be used to drive a hydraulic pump, for all the uses you outline.

Far better than using superheated steam for drying wood would be a condensing steam engine, or turbine, with an air cooled condenser system. The large amount of condenser heat would provide lots of hot air for wood drying. Also, it would minimize the problem of water supply and treatment for the boiler. It would be very interesting to do an energy balance on the proposed process. In particular, how much energy is necessary for mechanical power and how much heat is required for drying wood."

Rasmus: "Kevin, thanks very much for the input. Having a skilled boiler operator was indeed an absolute must in the old days of the steam engine due to the risk of explosion. Today we can eliminate that with an electronic control, such as an Arduino board ($50) plus pressure sensors, hence "modern" steam engine. Your suggestion of air cooled condenser makes a lot of sense."

Kevin: "OK!! The Arduino could be the basis for a neat control system. However, boiler inspectors are a conservative lot, and it really doesn't matter if it works... what is important is if you can get the inspector to approve your system.

Various Jurisdictions have various laws relating to the conditions under which they can approve a system. In general, they are tied to steaming rate, operating pressure, volume of water under pressure, and control system. You should check with the boiler inspector in your area, and find out beforehand, what hoops he will make you jump through. Best wishes, Kevin"

Larger automotive implementation

A larger implementation (perhaps based around a LifeTrac core) makes ever more sense the more of the above implements are included. Such a larger version would have a larger chipper, boiler and steam engine. It would certainly include a hydraulic log splitter and (electric ?) chainsaw.


Chipper Hammermill Chipper Hammermill