Keith, Better late than never? I don't know that I answered a question you asked, when we were finishing our conversation about Harold Bate:
Keith Addison wrote: > If Bate's regulator won't work, then what will? How would one run a modern > car on biogas (scrubbed I suppose)? Would propane conversion kits work, like > these maybe? > > Propane Conversion Kits > <http://poweredbypropane.net/products-pricing-order-online/propane-conversion-kits-3.html> > > Diesel Injection Kits > <http://poweredbypropane.net/products-pricing-order-online/diesel-injection-kits.html> > There may be more reasons (I'm not sure), but I can think of at least two reasons that propane conversion equipment would not work, or would not work well. The more minor of these derives from the fact that propane (C3H8) is much easier to compress or liquefy than natural gas or methane (CH4). (As you know, what one wants for use in a mobile engine is the pure or nearly pure methane that results after biogas has been scrubbed of its CO2. Natural gas often has a higher BTU rating per cu. ft. as compared with methane, because it generally has a few percent of ethane [C2H6], propane and butane [C4H10] in it, with the remainder [~90%] being methane.) When any of these gases exit a tank under pressure, travel down a pipe and are injected into a carburetor, at some point they expand, and according to Boyle's law (or actually, Charles's law), the more they expand, the greater the temperature drop. As such, a gas under greater pressure would expand more, and would cool off to a greater degree. As I said, I'm not sure (I haven't tried it, and it would depend on the design of the system), but I suspect that because methane would generally be under far more pressure than propane, propane equipment, handling methane, might freeze under heavy use, or in cold weather. The second reason is that the energy density of propane is rather different than that of methane, and it requires a different amount of air to combust. As such any equipment which is designed to inject propane would have been designed under assumptions that might not work well with methane. What one would want, therefore, when powering a car from well-scrubbed biogas is either LNG (liquefied natural gas) or CNG (compressed natural gas) conversion equipment. Such equipment would be designed to insure that enough heat could be extracted from the air, exhaust or radiator water to expand the gas, and it would be designed to provide the proper range of mixtures necessary to properly combust methane. Based on what I see on the 'net, CNG conversion kits run from $700 up, and a complete conversion where one drives the vehicle in and then picks it up-- the "no scraped knuckles, no grease on the pants" option-- could be up to $3,800. It is harder to find LNG conversion kits, and it would be more difficult and rather more expensive both in dollars and calories to liquefy methane, as we have previously discussed, but the advantage is that one can store almost twice the volume of fuel in any given volume of tank. The energy density of CNG is about 25% of diesel, whereas the energy density of LNG is about 40% of diesel. With a higher mileage car used for shorter trips, it would make little sense to use LNG (i.e. L/B/G, in this context), but with heavy vehicles used for more extensive trips, it may be a sensible choice. There really would be little point, of course, in using biogas to power a vehicle unless one has a lot-- a lot-- of biogas, and sufficient funds to be thinking about payback periods of a few years or more. d. -- David William House "The Complete Biogas Handbook" |www.completebiogas.com| "Make no search for water. But find thirst, And water from the very ground will burst." (Rumi, a Persian mystic poet, quoted in /Delight of Hearts/, p. 77) -------------- next part -------------- An HTML attachment was scrubbed... URL: /pipermail/attachments/20081124/ec84fb18/attachment.html _______________________________________________ Biofuel mailing list Biofuel@sustainablelists.org http://sustainablelists.org/mailman/listinfo/sustainablelorgbiofuel Biofuel at Journey to Forever: http://journeytoforever.org/biofuel.html Search the combined Biofuel and Biofuels-biz list archives (70,000 messages): http://www.mail-archive.com/biofuel@sustainablelists.org/
