Hybrid cars combine two technologies, usually a battery and a gasoline or diesel engine. With a large battery, the engine doesn’t have to produce as much power, and doesn’t have to be built to operate over a large range of power requirements, from driving at a constant 30 mph to merging into freeway traffic. The battery assist allows the engine to operate more often in its most efficient range.
Plug-in hybrids use an even larger battery. If they are charged up at night, they can go short distances (20 miles or more) during the day with battery power alone. On average, cars are expected to get about 100 miles to the gallon with a charging cost of $1/gallon.
There are several obstacles to plug-in hybrid cars. The car costs much more, and batteries need to be replaced and disposed of. New coal power plants will spew pollution and greenhouse gases. Batteries are polluting under the best of conditions.
There are advantages as well. Utilities would be able to use more base load power plants (running 24/7) and less of the more expensive peak load plants (not true where hydroelectric power is used for baseload). Oil use would drop dramatically if all vehicles are plug-in hybrids, bringing down both the price of oil and the amount of money going to oil powers.
From National Renewable Energy Laboratory
Standard hybrid electric vehicles contain a small- to medium-sized battery pack and electric motor. These devices help the engine operate more efficiently and enable normally wasted braking energy to be recaptured. While hybridization helps improve the fuel efficiency of hybrid vehicles, all of the energy used still comes from the fuel tank. Even the energy stored in the battery was once fuel.
In contrast, plug-in hybrid electric vehicles have the ability to recharge their batteries with electricity from the utility grid. They typically have larger battery packs and will use the stored electric energy instead of gasoline whenever possible. Under some conditions, a plug-in hybrid may even operate on electric power only. When needed, the engine and liquid fuel will be used to extend driving range and enhance performance. An onboard computer decides when to use which fuel.
Hence its name, a plug-in hybrid features a plug, which can be plugged into a standard 110-volt outlet for recharging the batteries.
