Getting Power to Your Electric Vehicle
By: Morgan Davis
Most of us recognize that the process of getting gasoline from the oil well to your car's fuel tank is complicated, but few recognize that the process of getting electricity to your home or workplace is complicated also. Electricity can come from many different sources and locations. As the driver of a plug-in electric vehicle (PEV) it is important for you to understand where the electricity you use to charge your vehicle comes from, what it means to refuel your vehicle from electricity, and to maximize the many benefits of electric drive.
From the provider's perspective, the electricity you receive to refuel your vehicle is converted into usable electricity from some sort of generation (hydro, coal, nuclear, wind, solar, natural gas, etc.). After the electric energy has been created, it travels as current to a switchyard, and then along transmission lines to a power plant, which is generally controlled by your utility. When the utility receives a signal that your home requires electricity, the electricity flows along more transmission lines until it reaches a substation, a facility with equipment to switch, transform or control electric power. Eventually, a transformer changes the voltage of the electricity so that your home can handle it. There, a charger delivers the electricity to your vehicle's battery.
Current is the flow of electricity within a circuit. The electricity that comes from your household outlets is alternating current, or AC. A second type of current is direct current, or DC. Most PEVs today charge with AC, which is converted to DC onboard the vehicle. However future chargers and fast chargers may charge with DC.
Charging Your Vehicle
The designated power level that you use to charge your vehicle, and the subsequent demand that the utility company must supply, can vary. The power that most household appliances use, such as a lamp or a computer, is about 1.44 kilowatt (kW). This power level is designated Level 1 for most PEV chargers. A second type of home charging, denoted Level 2, is rated at 3.33 kW or 6.6 kW— a power level used by a typical domestic electric clothes dryer. The higher the power a charger can handle, the faster the vehicle will refuel its battery. Also, the higher the power, the more electricity you use from the utility as the vehicle charges. If you are billed for electricity on a time-of-use basis, then how much electricity in kilowatt hours (kWh) you use, and when you use it, will determine how much you pay.
The PEV uses power from the grid to recharge its battery. Similar to a cell phone, a PEV needs to recharge. If it is a plug-in hybrid electric vehicle (PHEV), like the Chevrolet Volt, it also has the ability to refuel with gasoline. However, if it is a battery electric vehicle (BEV), like the Nissan Leaf, it must be plugged in to be driven when it runs out of charge.
Project Engineer / Scientist