Electric Drive Technologies
Dedicated Battery Electric Vehicle (BEV)
BEVs use a rechargeable battery for fuel, replacing gasoline, diesel or other types of combustible fuels. These vehicles utilize electric motors to propel the vehicle.
Refueling an electric vehicle consists of connecting the vehicle to an electrical outlet or charging device. Recharging time varies, depending on the battery type, capacity and the voltage/current output of the charger. Additionally, electric vehicles are much more energy efficient then Internal Combustion Engine (ICE) vehicles.
Hybrid Electric Vehicles (HEV)
An HEV is an electric vehicle that uses an onboard internal combustion engine linked to a motor/generator to drive the vehicle and/or recharge the batteries. There are currently many different hybrid-electric system designs utilizing different fuels or engines. These design options are grouped in three categories: series (range-extending HEVs), parallel (power assist HEVs), and dual-mode HEVs.
The main sources of energy used in the most common HEVs today are gasoline and batteries. A battery contains no moving parts.
The only energy wasted is a very small amount of heat during the course of a discharge cycle. As previously mentioned, hybrid electric vehicles utilize two different energy sources. For those vehicles currently available commercially, batteries are the secondary energy supplier for the vehicle and an engine that burns gasoline, diesel fuel, or alternative fuels such as methanol, ethanol or compressed natural gas provides the primary power. The cleanest, most fuel efficient HEV design is one in which there is a significant all-electric range (20 miles or more) and where the vehicle is plugged in to recharge the batteries at the end of the day. The ultimate goal of the hybrid electric vehicle is to provide the equivalent power, range, cost and safety of a conventional vehicle while reducing fuel costs and harmful emissions. At present an HEV is able to operate nearly twice as efficiently as traditional internal combustion vehicles.
Another version of the HEV is the Plug-in Hybrid Vehcile (PDF, 185 KB) (PHEV). A PHEV is a conventional hbrid car with a larger, more powerful battery and a standard electric plug. It looks and feels just like a traditional car, but the battery can be charged by plugging it into any standard outlet. PG&E currently has a PHEV that demonstrates successful implementation of a converted 2006 standard Toyota Prius to a PHEV.
Fuel Cell Vehicles (FCV)
A fuel cell vehicle is essentially an electric vehicle that has a fuel cell providing the electric energy needed to run instead of batteries. The fuel cell vehicle carries a supply of hydrogen that the fuel cell converts to electricity. A fuel cell is an electrochemical device in which the energy of a chemical reaction is converted directly into electricity. Electricity is formed by combining hydrogen fuel with oxygen from air, without combustion of any form. Water and heat are the only by-products when hydrogen is used as the fuel source.
Although hydrogen is considered the primary fuel source for fuel cells, the process of fuel reforming allows for the extraction of hydrogen from other fuels including methanol, natural gas, petroleum, or renewable sources. Unlike a battery, a fuel cell does not run down or require recharging; it operates as long as a fuel is supplied.
