Electric vs Liquid Fuel Drive

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On Sun, May 31, 2009 at 1:09 PM, Rasmus <trkiehl@#######.com> wrote:


yesterday, Biochar Ontario held its monthly board meeting on a farm about 100km west of Toronto. It was a wonderful setting and we were able to hammer out a lot of details relevant to our imminent incorporation as a not-for-profit (mission/vision below).

I am sure you are aware that fuel for machinery is one of the biggest cost items for the small farmer. Rather than use bio-diesel, why not go electric ? Then, biomass pyrolysis can be used for electricity generation. Flexi-pyrolysis units can make biochar, produce heat and electricity. As much as I appreciate your efforts for LifeTrac, a simple electric tractor seems like a good alternative.

Marcin: I agree, but only if you don't mind the approrimate 10-fold cost increase of going from fuel to electric drive, if you assume 4 wheel drive, and if you don't mind the limited driving range, and if you don't mind the extra inefficiency of charging/discharging batteries instead of using the fuel directly. If these are acceptable to the user, then this should be developed. For our present needs, the 10-fold cost over the existing LifeTrac scheme, and limited range, make the electric option not so attractive. Moreover, one needs to use the existing drive train if one does not use dedicated wheel motors, which makes one susceptible to the failure of transmission - which is why we designed the transmission out of LifeTrac to reduce the maintenance costs. As resources increase, we're open to considering electric in the future - but not without opensourcing wheel motors, controllers, and possibly batteries - without which the electric option remains prohibitively expensive. If you disagree with any of my claims, I'm open to your feedback as well.

This applies to tractors on the 40 hp range, though smaller ones (10 hp) are much less in parts - as in the link you sent. But note that the tractor shown has a range of about about 4 kWhrs, which is sufficient to run LifeTrac for less than 10 minutes.

I've driven a converted electric tractor similar to the link. While an exciting show piece, it does not serve our basic needs - unless it were to have a much more sizeable battery - at a costg of $10k for the minimum acceptable range.

There are serious limitations to electric based on price and range, both of which can be addressed by using open source development. We'll get into this later, as it is a much more difficult problem statement than liquid fuel drive like we're pursuing now. Given that we can get 500 gallons of pyrolysis oil per acre here, that is sufficient to run a closed loop cycle on our fuel needs - and given that this is low-hanging fruit - it's a matter of strategy to develop this first.

Rasmus: While biodiesel is not all that difficult to make, having biomass waste as the energy source would reduce the need to grow biodiesel crops and eliminate the need for further processing/glycerol etc. Our ideas yesterday also included a small on-board biomass pyrolysis unit (=wood gas) that powers a small motor+electric generator, reducing the need for a large battery and extensive recharge time.

Marcin: This could be a great plus for the propulsion system. Do you have any leads on such small, on-board units? We'd like to build one as soon as the technical due diligence is developed.

Rasmus' comment on this email, nearly 2 years later: I have studied these issues in some more detail, and now think that the development of some kind of external combustion engine for agriculture is essential. I think that OSE's modern steam engine (in a PowerCube) is very promising. Hydraulic transmission is a natural fit.

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