Product Selection Changes
(The following is taken from Section III of http://openfarmtech.org/OSE_Proposal.doc)
(Update as of 5.19.09 - Since the above proposal was published at the beginning of 2008, there have been several changes in the product choice for reasons of impact and robustness. These are summarized on this page.
- Electric motors have been replaced by hydraulic motors as the vehicle driver of choice, simply because 4 wheel drive systems using simple wheel motor configuration can be attained at a cost of about $1500 for hydraulics, and about $20,000 for electric drive using low-speed hub motors, power controller, and ancillary electronics. Since battery storage does not address long-distance driving needs - and hybrid vehicles require a power engine anyway - we reduced the complexity and cost at least a factor of 10 by going to hydraulics. Note that hydraulic drive is applicable to heavy equipment and cars - as a quick internet search will reveal. Since we are interested in a sufficient set, hydraulics are sufficient for all drive purposes, and have the advantage of high torque and low to high speed ranges.
- At the same time, electric motors are still relevant to electrical power generators, but they are not in the 40 key technology set.
- Fuel alcohol was replaced by pyrolysis oil. Pyrolysis oil yields are first, about 5 times higher than fuel alcohol yields per given area, and second, unless one goes to wood alcohol, sugar or starch crop is much more valuable as food for humans or animals. The other reason for pyrolysis oil is that cellulose is readily available in the form of trees or grass crop, as opposed to sugar/starch crop, which needs to undergo intensive cultivation for immediate yields - in the case where a Global Village building needs immediate access to liquid fuels. Pyrolysis oil is compatible, in its crude state, with external combustion engines.
- Aluminum smelting from clay was replaced by steel melting from scrap, due to the much simpler technology and ready access to industrial metal scrap.
- Wood gas compressor has been replaced by pyrolysis oil for liquid fuel purposes, and it was replaced by pyrolysis gas from combined heat/power gasifiers as a cooking gas source.
- Boundary layer turbine - longevity issues and 2-3 fold lower efficiency compared to steam engines make the solar turbine highly inapplicable to the global village construction set.