Plug-in Hybrid Electric Vehicles
How Hybrid Vehicles Work
Hybrid vehicles (HEVs) work through a combination of an internal combustion engine, a bank of batteries, and an electric motor. This combination varies from “mild hybrids,” which simply reduce the engine size and boost acceleration with an electric motor—to a set up wherein the engine runs only to produce electricity, that then runs an electric motor. Currently, most HEVs are somewhere between the two extremes—the vehicle can be driven either with the engine (almost exclusively), the electric motor solely, or both the engine and electric motor simultaneously providing power.
Conventional Vehicles (CVs) generally have larger engines than HEVs. However, the trend is to keep HEVs similar to CVs in both look and feel while improving fuel economy—this is best seen in the Honda Accord. The Honda Accord HEV actually outperforms its CV counterpart, yet maintains a significant fuel economy advantage. Below is a chart of currently available vehicles and their engine sizes—this information was gathered from the manufacturers’ websites.
PHEV is an abbreviation for Plug-in Hybrid Electric Vehicle. These vehicles, like other Hybrid Electric Vehicles (HEVs) have an onboard internal combustion engine that charges batteries or otherwise provides electricity to an electric motor. This electric motor either assists the internal combustion engine (in parallel HEVs) or is the sole mechanical link to the wheels (in series HEVs). What makes a PHEV different from a HEV is its ability to charge the batteries by plugging the vehicle in. This feature has the advantage of allowing the vehicle to run for some distance without running the internal combustion engine at all—thus reducing the use of petroleum. Below is a schematic of how a typical PHEV might work.
The difference between a PHEV and HEV is that—a PHEV has all the abilities of a HEV but also can charge its batteries by plugging in to grid-provided electricity. The primary advantage of this—is the effective increase in fuel efficiency.
A BEV (battery electric vehicle) must be plugged in to obtain energy to drive the vehicle and has a range limited by the battery pack. A PHEV may either run off the battery or off the engine, and so, the PHEV does not “have to” be plugged in and the range is unlimited per periodic refilling of the gasoline/fuel tank.
No. Unlike electric vehicles (EVs) that have to be plugged in to charge periodically, if a PHEV is not plugged in it will function just as a HEV would. In fact, some HEVs have the ability to provide electricity—for example, at a construction site or in case of a blackout—anytime when electricity is otherwise unavailable. Because PHEVs have all the HEV technology included in their design, PHEVs could certainly be used for this purpose as well.
Certainly, this depends on the manufacturer of the vehicle. There is no reason a vehicle could not “just be plugged in.” However, for convenience many manufacturers may decide to equip the vehicle in such a way that it automatically “docks” when you park it in its normal (usually overnight) spot. If this were the case you may not have actually do anything except park it for the vehicle to charge.
A “parallel HEV” maintains a mechanical linkage between the internal combustion engine and the wheels, the electric motor supports the engine (which is still the primary method of propulsion). Thus, the internal combustion engine and the electric motor run “in parallel.” If a vehicle runs only as a parallel HEV, the engine must run all of the time. Below is a schematic for a parallel HEV.
A “series HEV” completely severs the mechanical link between the engine and the wheels. Rather, the engine serves only to produce electricity that either is used directly to power the electric motor or charges the batteries when the use of all the electrical production capacity of the engine is not needed to power the motor directly. Below is a schematic for a series HEV.
Some vehicles, such as the Ford Escape Hybrid, combine these ideas. For limited distances and under 25 mph, the Escape can run without the engine running. However, for extended distances and when going over 25 mph the engine provides power directly and must run.
This term is relatively imprecise—but it usually describes a vehicle that still uses an internal combustion engine as the primary method of propelling a vehicle and includes some technology that provides a significant enhancement in fuel economy (over a conventional vehicle). One example of this is the Chevy Silverado.
Regenerative braking is simply a method of recovering energy while a vehicle is slowing down—energy that would otherwise be converted to waste heat (friction between the brake pad and rotor). In passenger vehicles, this energy is converted to electricity to recharge batteries. This is possible because the electric motor becomes a generator when run in reverse. Similar technology has been used for many years on the diesel-electric locomotives.
Most people drive relatively short distances on a daily basis. By running a car off grid electricity you can double, triple, and beyond—the effective gas-mileage of a vehicle. I would also refer you to our advantages page (link).
Many people have criticized vehicles that are plugged in because “they are using electricity produced by coal.” The implication being, we are just shifting pollution from the tailpipe to the power plant. This relies on a critical misunderstanding of PHEVs though. Due to principle called “peak-load shifting” PHEVs, if charged at night, will actually encourage more efficient electricity production. I encourage you to explore this topic further by looking at our Advantages Website or the websites listed here.