Alternative Fuel Autos: Technology
How Alternative Fuel Autos Work
Alternative fuel autos of all kinds are a reality today. Whether it’s achieving greater fuel economy or reducing America’s reliance on oil as a primary fuel source, automakers remain committed to populating America’s roadways with innovative vehicle technologies. In 2006, 1.5 million alternative fuel autos were purchased in the US. Below is a brief description of how these vehicles run on alternative fuels.
Biodiesel
Biodiesel is a blend of conventional diesel fuel and blendstocks made from fatty substances such as soybean oil and waste cooking oil. Most diesel vehicles can use biodiesel fuel at up to 5 percent concentrations (B5) without modifying the vehicle’s fuel system and powertrain, and some diesels are modified to use higher concentrations, such as 20 or 100 percent (B20 or B100). One important benefit of biodiesel is that it adds needed lubricity to diesel fuel. All diesel engines, especially advanced common rail diesel engines, operate at extremely high pressures and require good lubricity in the fuel to prevent wear. It is also critical that any biodiesel fuel meet certain specifications to ensure that it will work properly in today’s sophisticated engines. All vehicles require good quality fuel to minimize emissions and optimize performance.
Compressed Natural Gas
Fueling a vehicle with Compressed Natural Gas (CNG), which is a high-pressure gas rather than a liquid, requires that the engine be modified to change how the fuel is injected into the cylinders. Natural gas vehicles also require about four times the fuel tank volume to provide the same driving range as gasoline vehicles.
Clean Diesel
Compared to their gasoline counterparts, the new generation of clean diesel vehicles offer much greater fuel economy while delivering better performance. Around the world, consumers are favoring advanced diesel technology. Clean diesel powers 40 percent of Europe’s new light duty motor vehicles. Today’s diesel vehicles run more cleanly, thanks to new high-pressure fuel injection, combustion and exhaust after-treatment technologies. And the auto industry is working now to introduce technologies that will allow diesel automobiles to meet the Environmental Protection Agency’s latest stringent emissions regulations. A key factor in determining the success of these aftertreatment technologies was the EPA’s 2001 decision to require dramatic sulfur reductions in diesel fuel. This decision was critical for the sale of clean diesel vehicles in the U.S. Clean diesel vehicles are more fuel-efficient than gasoline-powered vehicles, especially in both highway and stop-and-go city driving. On average, clean diesel vehicles achieve 20-40 percent better fuel economy than their gasoline-powered counterparts.
Ethanol
All of the vehicles on the road today can use a blend of up to 10 percent ethanol with gasoline without voiding the warranty the manufacturer provides to consumers. There are also about 5 million vehicles on the road today that have been built to use up to 85 percent ethanol + 15 percent gasoline (known as E-85). These vehicles are referred to as flexible fuel vehicles (FFVs) because they can run on any blend of gasoline and ethanol between 0-85 percent ethanol. Some gasoline is required in ethanol blends to help facilitate cold-temperature starts. To make a vehicle ethanol-capable, manufacturers install a computerized optical sensor or other technology that detects how much ethanol is in the fuel mixture. The sensor then recalibrates the engine depending on the percentage of ethanol in the fuel. Because ethanol is more corrosive than gasoline, manufacturers need to use special materials for the gas line, gas tank, pumps, and injectors.
Hybrid-Electric
Hybrid-electric vehicles refer to powertrains that use a battery-powered electric motor, a gasoline internal combustion engine, and a concept known as regenerative braking to power the vehicle. To optimize performance, emissions, and fuel efficiency, a computer is used to manage the energy from these three systems. The computer senses the driving mode and the battery state of charge and then directs energy from either the battery system or the gasoline engine to the most appropriate drive train component, an electric motor or an engine drive shaft. Regenerative braking systems, which recover energy that is otherwise wasted, allow hybrids to be especially fuel-efficient in stop-and-go city driving. Utilizing these hybrid technologies, fuel economy can be improved by up to 25 percent over conventional automobiles.
Hybrid-Electric Ethanol
This technology marries two petroleum saving technologies – hybrid-electric power and flexible-fuel capability. A hybrid-electric E-85 would be capable of operating on blends of fuel containing up to 85 percent ethanol.
Hydrogen
The concept of using hydrogen in internal combustion engines (ICEs) offers several advantages: near-zero net emissions, maintaining the utility and flexibility of today’s automobile and helping to promote a hydrogen fueling infrastructure. Hydrogen-fueled vehicles emit only water vapor when burned. Hydrogen ICEs are capable of running on either liquid hydrogen or gasoline. With dual fuel capacity, hydrogen ICEs can be switched to gasoline operation should it become necessary, eliminating any restrictions that might be imposed by range or hydrogen availability. These vehicles also use today’s fuel cell technology to power the vehicle’s electrical system. This source provides more power than a conventional battery, allowing, for example, the air conditioning or heating system to be operated with the engine off.
Fuel Cells
Fuel cells use hydrogen to produce continuous electric currents. They employ a process that chemically combines hydrogen and oxygen to produce electricity and water. Because each fuel cell produces less than one volt, they must be stacked in a row to produce enough voltage to meet your driving needs. Electricity is produced when hydrogen is fed into one end of the fuel cell. There it meets a platinum anode that strips an electron from each hydrogen atom, producing an electric current and a stream of hydrogen ions. The electric current flows to the electric motor, supplying it with power. At the other end of the fuel cell, a platinum cathode brings together the stream of hydrogen ions coming from the platinum anode, the electric current returning from the electric motor, and oxygen. These three react to produce water.
Propane
Propane, like natural gas, requires that the engine be modified to change how the fuel is injected into the cylinder. Because it is a high-pressure gas, a vehicle’s fuel handling system and engine must be modified to take in a compressed gas fuel as opposed to a liquid fuel.
