Hybrid Electric Vehicles

Four year ago when General Motors put its reputation on the line by introducing the GM EV1 electric vehicle it seemed as if vehicles powered by batteries would be the answer to the long-term problem of polluted air. There is more than a little debate over how much of our air pollution is actually caused by moving sources (read cars, trucks and buses), but there is no doubt that a significant percentage arises from these sources, even though the gasoline-powered cars of today put out just a tiny amount of pollutants compared with their predecessors of the 1960s, so the introduction of the EV1 as a car for the general public was a significant step. But, as it turns out, it might have been a misstep.

Recently General Motors announced that it had recalled all of its 1996 model year EV1s because they could catch fire during the lengthy recharge process. Not only was that a big strike against them, but GM also announced that the recalled cars wouldn't be fixed until sometime next year. Though some 1999 EV1s are now scooting around the urban areas of the American Southwest, it is doubtful whether the 1996 models will ever again see the light of day. Luckily for the lessees who drove them, GM let them out of their contracts with no early termination charges.

Despite the GM miscues with the EV1, some argue that the electric vehicle, as a clean-running, non-polluting concept, is still worth pursuing. They may be right. In the real world, however, EVs from the Baker Electric of the early 1900s to the modern GM EV1 to the discontinued Honda EV have never been able to overcome the problem of range. Current electric battery technology seems unable to produce a storage medium that will hold sufficient energy to give the vehicle adequate cruising range, at least at a price we working humans can afford.

What is adequate cruising range? Well, again, debate will ensue, but it is certainly on the high side of the fewer than 100 miles the EV1 offers before it is forced to go through a lengthy re-charging process. The typical gasoline-powered car offers a range of 300 to 400 miles on a tankful of fuel. Further, when you add in the fact that gasoline and diesel-powered vehicles can be refueled in a matter of minutes, for practical purposes they have unlimited range. Certainly putting in a 1,000-mile day in a typical automobile on a cross-country journey is something many of us have done routinely - a feat virtually impossible in a storage-battery electric car.

Just as electric cars seemed about to be discredited again with the EV1's failings and the public's indifference to Ford and Honda electric vehicles, a new breed of electrics has regenerated (sorry) public interest and excitement. Dubbed generically hybrid electric vehicles (HEVs), these vehicles combine many of the best attributes of electric vehicles with those of conventional internal combustion-engine cars.

What is a hybrid car?

As the federal government defines it, a hybrid electric vehicle is a vehicle that has two sources of motive energy. What this usually means is some type of internal combustion engine combined with electric motors getting their power from storage batteries. Unlike in so-called "pure" electric vehicles, the batteries are not charged by an outside source e.g. plugging them into an electric socket in your garage. Instead, their batteries are charged by an in-vehicle charging system. Thus, they are self-contained except for the need to re-fuel their internal combustion engines.

Of course, there are many hybrid system concepts getting currency including some that use fuel cells, gas turbines, diesels, and lean-burn gasoline engines in various combinations with flywheels, batteries, and ultracapacitor storage media. Many, including the Department of Energy (DOE) Hybrid Vehicle Propulsion Program, believe HEVs have several advantages over traditional internal combustion engine (ICE) vehicles.

Among the advantages, many hybrid vehicle concepts have "regenerative braking capability," which means that during deceleration some of the energy that in conventional cars is simply dissipated as heat is used to recharge the storage device - most often a battery but perhaps a flywheel. The internal combustion engine used in the vehicle can be sized to deal with average load, not peak load, since the auxiliary stored power - usually electric battery power used to activate electric motors - is used to deal with peak load such as hill climbing. This has the benefit of allowing the installation of a smaller, lighter and less fuel-thirsty engine.

Largely because they have smaller, less powerful engines, fuel efficiency of a hybrid electric is significantly better than with gasoline-powered vehicles, while emissions are greatly decreased. Using "re-generative" braking also increases overall efficiency.

The use of smaller engines means that HEVs can be equipped with powerplants using alternative fuels. The DOE's Hybrid Vehicle Propulsion Program sees this as an advantage since the HEVs need not be dependent on fossil fuels.

All these benefits are well and good, but they offer no advantages if the buying public turns its collective back as they have with electric vehicles up to now. The beauty of hybrid electric vehicles, in the eyes of manufacturers, is that they will help improve air quality with no appreciable loss in vehicle performance, range or safety. In short, most hybrid electric vehicles will perform as well or better than internal combustion engine-cars of similar size.

The major difference between the "pure" EVs and the HEVs is the use of an engine, most often an internal combustion engine using conventional fuels. By using engines, instead of a motor/storage battery combination, vehicles can achieve long ranges. In fact, fuel economy can be phenomenal, because the engines need only propel the vehicles at cruising speeds on flat ground. In the rarely encountered more challenging situations, the energy storage devices (batteries) in the HEVs provide the additional power for climbing hills and acceleration. Plus, because HEVs use conventional fuels, virtually no change in infrastructure is required for their use. In contrast, "pure" EVs require special charging stations.

According to the DOE's Hybrid Vehicle Propulsion Program, "most experts agree that the car of the future, that has the same versatility as a conventional vehicle, will be an HEV of some kind. The energy density of electric batteries will never equal that of liquid or gaseous fuels, necessitating that these fuels remain a critical part of future vehicles to maintain the driving range and quick refueling found in today's conventional vehicles."

It noted that even fuel cells, which are a promising long-term technology for personal transportation, will most likely be put in an HEV configuration with a high power energy storage/buffer device onboard. Rather than having only one propulsion system choice when buying a future vehicle, it may be possible to select the propulsion system in the same way that one selects a 4-cylinder engine or a V 8.

In the future, you may be able to select a vehicle, and then decide if you want a conventional engine, batteries only, or an energy storage device (batteries, flywheels, ultracapacitors, or some combination) and an propulsion unit (fuel cell, turbine, diesel engine, Stirling engine, or conventional internal combustion engine).

Just what this world needs, more choices.

by Jack Nerad