Previous message was inadvertently sent out too soon- please disregard it. When it comes to workable solutions to the energy crisis, sometimes it can pay to "think small"... And when it comes to "power-assist" for the bicycle, even in the range of 300 watts... the best overall solution may involve a slight amount of carbon release.
After all, the bicyclist will necessarily breath-out some CO2, so it always needs to be considered as a complete picture... but there is a viable option to batteries: surprise, surprise: compressed natural gas (or propane). And as for the emissions, CNG (compressed natural gas) could actually be less polluting, overall, than batteries charged with grid power, given the line-losses and inefficiency. The key would be the direct conversion of heat to electricity in a small fuel cell (SOFC). There was an actual model and prototype of a FC powered bike made by Gore and Aprilla in 2005. It generated lots of good-press and lots of hot-air. But it failed miserably and for good reason! The design was beyond-stupid. The design was way overpowered and way, way overpriced, and used unavailable hydrogen instead of CNG. Three strikes and your out, even if your name is Gore! Here is a table of energy density: Lead-Acid Battery 40 Wh/l 25 Wh/kg NiMH Battery 280 Wh/l 100 Wh/kg Li-Ion Battery 200 Wh/l 150 Wh/kg EEStor Bat-Cap 280 Wh/kg Propane 13,900 Wh/kg CNG 3,100 Wh/l 12,100 Wh/kg As you can see- compared to the best battery, CNG has about a 40:1 advantage in energy density ! Time to revisit this power assisted bike concept, but 1) Forget H2, go with CNG or propane, with home refilling 2) Forget the Gore Fuel-cell, go with a small version of the SOFC 3) Mistubishi has been running SOFC fuel cells in Japan on CNG for the past 15 years. This is not new. Here is what they (Mitsubishi) say: Among fuel cells, SOFCs can employ natural gas, LPG, methanol or coal gas as a power source. When run at 1,000°C, the SOFC can attain a generation efficiency of 65%, surpassing the 50% achieved by LNG compound-power generation at grid power plants (i.e. lower net pollution) There are two types of SOFCs: flat types and cylinder types. In terms of our future electricity business, we are particularly interested in flat-type SOFCs, which will be less costly and allow downsizing. Problem is: Mitsubishi only makes large Cells for grid power or factories. Plus- the SOFC needs to be run hot, but that is where good insulation comes in. OK- maybe the green movement should use the "threat" of Mitsubishi becoming the American Green-Hero in order to entice some big US industrial company, like Boeing ;-) to fund the development of a small (300 watt flat SOFC) for a bicycle, the frame of which bike is made of carbon fiber and capable of holding about 500 grams-equivalent of CNG or propane. This could realistically allow 5-10 million Americans to bicycle commute, if decent financial incentives were attached (why not give away the bikes free to regular commuters?) and get that many polluting vehicles off the road - AND - (perhaps most important of all in the long run) provide fabulous health benefits to the participants. Optimistic, yes, but is this proposal too far out-there to be practical (assuming that the Petro-Mafia is removed from its current high level of influence in politics soon) ? Jones
