DOE Advanced Vehicles Information

DOE Advanced Vehicles List

Examples of Advanced Technology Vehicles and Specific Technologies

Vehicle Types

• Hybrid-Electric vehicles commonly employ an internal combustion engine with an electric motor and additional batteries. The combustion engine is often configured to both recharge the batteries and provide additional power at higher speeds and during acceleration. By using the internal combustion engine to recharge the batteries, these hybrid vehicles do not need to be plugged-in to an existing electricity source to recharge the batteries. Regenerative braking systems also recharge the batteries. These systems engage a generator when the brakes are applied, converting some of the kinetic energy back into electrical energy while slowing the vehicle down.
• Plug-in Hybrid vehicles operate similar to regular hybrid electric vehicles, but can be connected to an external power supply for recharging. Plug-in technology is paired with larger batteries to provide a greater range using only electric power. There are two common types of Plug-in vehicles, Battery Electric Vehicles only use batteries for travel, and have no internal combustion engine. Plug-in Hybrid Electric Vehicles combine an onboard internal combustion engine with batteries and electric motor to improve fuel economy.
• Fuel Cell vehicles use a fuel cell in place of an internal combustion engine to produce electricity which is used to power an electric motor. A fuel cell is an electrochemical conversion device, meaning it uses chemical reactions to produce electricity, much like a battery. A battery has a finite amount of chemicals stored inside whereas a fuel cell is constantly fed chemicals allowing prolonged use and "refueling". Although a fuel cell can be designed to operate on many different fuels, hydrogen is the most commonly cited fuel source for fuel cells. A hydrogen fuel cell uses hydrogen and oxygen to produce electricity, generating water (H₂O) as a byproduct.
• Hydraulic-hybrid vehicles use a hydraulic system and pump to improve efficiency. Much like regenerative braking is used to recover electricity to slow the vehicle, a hydraulic hybrid compresses nitrogen gas to slow the vehicle. This compressed gas is then allowed to expand to assist with acceleration. Hydraulic systems are most effective for frequently stopping vehicles, and especially for larger vehicles such as delivery trucks.
  

Specific Technologies Examples

• Turbo Charging utilizes the exhaust gases on a combustion engine to compress the air being delivered to the engine, increasing the power output of the engine. This allows a smaller, more fuel efficient engine to produce the same amount of power as a larger engine.
• Cylinder Deactivation uses electronic controls to deactivate (cut fuel supply) to some of the cylinders on an internal combustion engine when they are not necessary, such as when traveling at a constant speed on a highway. By restricting fuel supply, an increase in fuel economy is realized.
• Variable Valve Lift and Timing employs mechanical and electrical components to vary the time between the fuel delivery, ignition, and exhaust to increase the fuel economy. This works by allowing more complete combustion to occur, wasting less fuel.
• Low-Leak Air Conditioning uses improved sealing mechanisms to reduce the fugitive emissions from the air conditioning system. Improved air conditioning system efficiency can reduce the power demand on the engine, improving mileage.
• Continuously Variable Transmissions replace the traditional geared transmission with a variable belt and pulley system. By providing an infinite range of ‘gears’, a continuously variable transmission allows the engine to always operate at its most efficient speed.
• Direct Fuel Injection delivers fuel directly to the combustion chamber rather than upstream of the cylinder intake valve. This provides improved control over fuel delivery, allowing improved fuel utilization and ultimately, fuel economy.
• Electrification of parasitic loads is gaining popularity as a means of improving fuel economy. Parasitic loads are anything driven by the engine that takes power away from propulsion. These commonly include the power steering pump and the compressor for the air conditioning. An electric power steering system replaces the hydraulically assisted power steering mechanism with electrically powered ones. Although still indirectly powered by the engine through the electrical system, electric power steering can be more efficient and does not place a continuous load on the engine like hydraulically assisted power steering.

For additional information, call Tim Shepherd at (410)537-3270 or email tim.shepherd@maryland.gov.​