Alternative Fuels For Motorcycles
Alternative Fuels for Motorcycles
A rundown of the options
What if the European Union had passed the recently proposed stringent carbon-dioxide emissions standard for motorcycles? What if the peak-oil Cassandras are correct and gasoline becomes more valuable than 20-year-old Scotch? Don’t worry, motorcycles will still exist, and still be capable of ever-increasing performance, but powered by something other than pure gasoline. Here’s a look at the most likely paths toward changing how we ride.
Electric
As discussed in the "Electric Motorcycles" feature, battery-powered bikes have already begun to evolve into higher-performance machines, if currently short-ranged. But electric energy from the grid still has to come from somewhere. So far, hydroelectric, wind farms and thermal solar are the most promising renewable energy options, with coal, natural gas and nuclear making up the bulk of current U.S. electricity production. If we built nuclear breeder reactors, such as the canceled-in-1994 Integral Fast Reactor, there is sufficient uranium already in current U.S. inventories—much of it unusable in other reactor designs—to match total annual U.S. energy consumption (petroleum, natural gas, coal, hydroelectric, everything) for the next 400 years! Nuclear fusion is another possibility, but it suffers from a weird corollary of Zeno’s Paradox in which commercial implementation is always 20 years from the current year, with the new start date updated each January 1st.
Biofuels
The most obvious of these is ethanol, already used in gasohol throughout the U.S. and a mainstay of the transportation system in Brazil, where it is produced from sugar cane. Motorcycles would need to have fuel systems suitable for high-alcohol fuels such as E85 or E100; use in older machines would be problematic, as many of their fuelsystem components are incompatible. With one-third less energy per gallon, ethanol gives both less range for a given fuel-tank size and requires substantial rejetting or ECU reprogramming in existing machines. Plus, current ethanol production from corn is a) uneconomical without a government subsidy: b) raises food prices; and c) uses almost as much or more petroleum in its production as it replaces. Much research is focused on more-efficient ethanol production from plant waste (corn stalks, etc.) and may bring more cost-effective ethanol production in the next decades.
Methanol is currently produced from natural gas and is a very attractive fuel if the infrastructure were there to support it. Directinjection spark-ignition engines burning methanol can meet emissions regulations with turbocharging and 14:1 compression ratios, and do so with more power than any gasoline engine and overall energy efficiency rivaling diesels. Methanol can also be produced from biomass, but as with ethanol, economic production to compete with $3-agallon gasoline has yet to be achieved.
Synthetic fuels
Synthetic gasoline can be produced from coal—a technology developed by Hitler’s Germany and perfected in South Africa when a worldwide ban on exports to that country was enforced during the apartheid era. It generates substantially higher carbon-dioxide emissions than would burning the coal in electric power plants for electric vehicles, but it will power current vehicles.
Improving gasoline efficiency in new motorcycles
Motorcycle fuel consumption could likely be halved, with motorcycles capable of 60plus mpg becoming common. This involves following the path of the auto industry and pursuing every possible efficiency increase with internal-combustion engines. For highperformance vehicles, direct injection of a tiny amount of supplemental methanol during high-load conditions can prevent detonation, allowing substantially higher compression and the improved power and efficiency it brings; but it would require a small on-board methanol tank, perhaps a half-gallon or so. Variable valve-timing can improve low-load operation, and smaller, turbocharged engines can be more efficient during cruise while still hitting big peak power numbers. Wider gearbox ranges with more gears would allow more-efficient highway cruising. Better aero dynamics and lighter vehicle weight always improve efficiency. If peak power weren't the highest goal, relatively long-stroke engines turning at lower rpm can be more efficient for touring bikes and cruisers.
Other Alternatives
Compressed Natural Gas (CNG), a gas mixture consisting of mostly methane, is already commonly used to power low-emis sions internal-combustion engines in urban fleets such as taxis and city buses, and you can buy a few CNG-powered cars directly from manufacturers.
One CNG drawback for motorcycles is that the compressed gas is less energy-dense than gasoline; and to achieve equal range, the capacity of the 3600-psi-capable CNG tank (which for structural reasons almost certainly must be round or cylindrical with round ends) would have to be three times greater than a gasoline tank. But natural gas is readily avail able in the U.S.; and thanks to new extraction methods, the available gas is equal to a 100year supply at current usage rates. Another gaseous fuel frequently discussed for the future is hydrogen, whose only ex haust by-products are heated air and a little water vapor. Hydrogen requires a direct-in jection system and the tailoring of an engine for its extremely fast burn characteristics. it also is a difficult fuel to store; the volume of a hydrogen tank filled to 5000 psi has to be four times larger than an equivalentrange gasoline tank-unless you want to deal with liquid hydrogen at -423 degrees F. And for hydrogen to be a low-carbon fuel, it has to be made by low-carbon energy, either renewable or nuclear. Finally, there is essentially no current hydrogen distribution network for vehicle use, and the energy lost in compressing and transporting it would be significant -Steve Anderson
