Our look at alternative-fuel vehicles on the road continues. Although many petroleum substitutes make sense for personal vehicles in theory
and in the lab
, things are different for drivers on the road
. Here we focus on real-world cases for Biodeisel, Hydrogen and Electricity.
Ed. Note: This is Part II of our article Alternative-Fuel Vehicles on the Road: A 'Real-World' Guide. Part I focuses on the cases for and against Ethanol/E85, Methanol/M85 and Compressed Natural Gas (CNG) as potential petroleum substitutes.
Vegetable oils, rendered chicken fat and used fry oil are common sources for biodiesl, which are fuels for diesel engines made from sources other than petroleum. Diesels rely solely on high compression in the cylinder
to raise the temperature of the air enough to ignite the fuel. As such, diesels are tolerant of varying-quality fuels, and the high compression results in high efficiency. Diesels extract more energy from each gallon than gasoline engines, and less energy is lost as heat leaving the exhaust pipe than with a gasoline engine.
Modern diesel engines can run on 100 percent biodiesel with little degradation in performance compared to petrodiesel because the BTU content of both fuels is similar [...] In addition, biodiesel burns cleaner than petrodiesel, with reduced emissions. Unlike petrodiesel, biodiesel molecules are oxygen-bearing, and partially support their own combustion.
The DOE reports that pure biodiesel reduces CO emissions by more than 75 percent over petroleum diesel. A blend of biodiesel and petrodiesel (20:80 percent), sold as B20, reduces CO2 emissions by around 15 percent.
But pure biodiesel, B100, costs roughly a dollar more per gallon than petrodiesel. And in low temperatures, higher-concentration blends turn into waxy solids and do not flow, so special fuel additives/warmers
Overall, biodiesel has a viable future as a major fuel for transportation. According to the National Biodiesel Board, biodiesel production tripled from about 25 million gal. in 2004 to more than 75 million gal. in 2005. While the trend is solidly upward, obstacles to mainstream acceptance include a higher price than petrodiesel and the need to heat storage tanks in colder climates to prevent the fuel from gelling.
Hydrogen is the most abundant element on Earth. Because pure hydrogen can be made by electrolysis passing electricity through water oxygen is liberated, thus allowing for other industrial purposes. Most hydrogen currently is made from petroleum. Though hydrogen can fuel a modified internal-combustion engine, most see it as a way to power fuel cells to move cars electrically. The only byproduct of a hydrogen fuel cell is water.
However, most energy and industry experts agree that hydrogen fuel cell vehicles won't be widely available until 2020, as the industry still needs to develop a manufacturing and distribution system. And producing hydrogen remains expensive and energy consuming. PM notes that it takes about 17 kwh of electricity, which costs about $1.70, to make 100 cu. ft. of hydrogen which would power a fuel cell vehicle for about 20 miles.
Although hydrogen has the highest energy-to-weight ratio of possible energy sources, it's necessary to expend a tremendous amount of energy to compress sufficient hydrogen into an expensive, 5000-plus-psi storage tank in a vehicle," says PM. (Another option is freezing.)
Hydrogen's potential as a gasoline replacement is good. But it requires more time. While carmakers are deeply engaged in hydrogen fuel cell research, and some continue to work on hydrogen-fueled, internal-combustion engines, the barrier lies in finding a cost- and energy-effective way to produce hydrogen.
Electricity from a power source, typically a rechargeable battery pack, can energize a large electric motor to propel a car. When slowing or stopping, the braking energy reverses the power flow, turning the electric motor into a generator to help recharge the battery pack. Normally, however, the batteries must be recharged for several hours at a stationary charging station.
Vehicles that operate only on electricity require no warm-up, run almost silently and have "excellent performance up to the limit of their range," the PM report says. Further, at the average price of 10 cents per kwh, the per-mile cost comes to about 2 cents.
The electric car as well as a hybrid when it's running on electricity produces no tailpipe emissions. Even when emissions created by power plants are factored in, electric vehicles emit less than 10 percent of the pollution of an internal-combustion car.
Yet pure electric cars still have limited range, typically no more than 100 to 120 miles. And electrics suffer from slow charging, which, in effect, reduces their usability. When connected to a dedicated, high-capacity recharger, some can be recharged in less than an hour, but otherwise such cars are essentially not drivable while they sit overnight for charging.
The outlook of electric cars is mixed. While interest in plug-in hybrids grows, the long-term future of pure electrics depends on breakthroughs in longer-lasting, cheaper batteries and drastically lower production costs for the vehicles themselves. And then there's the environmental cost. Only 2.3 percent of the nation's electricity comes from renewable resources. In fact, about half is generated in coal
Clearly, our vehicles' energy future is anything but simple.
How far can you drive on a bushel of corn?
by Mike Allen
Popular Mechanics, May 2006
Mixed Signals & Federal Funding for Alternative Energy Research
Alternative Energy Blog, March 9, 2006
President Pushes Alternative Fuel Development
by Jim VandeHei
The Washington Post, April 23, 2006
Farm economy revs up ethanol-fueled engines
Reuters (via CNET), May 9, 2006
"Hybrids? I Got a Million of 'Em."
Hybrid Cars Get "Green-Tuned"
He Said, She Said: Hybrids vs. Fuel Cells
Official Fact Sheet: President Bush's Four-Part Plan to Confront High Gasoline Prices
White House press release, April 25, 2006