Fri11282014

On The Road

Hybrids & electrics are miles apart: Most alternative-fuel vehicles are suited for short drives

Photo Photo Courtesy Of TeslaThe four-door Tesla Model S, scheduled for introduction next year, is expected to have a range of 300 miles.

With the government’s goal of getting new models to average 35 mpg by 2016, the major automobile manufacturers are striving to improve their products. No longer is this just a matter of image – if the companies are going to meet this goal, every practical innovation has to be moving off the drawing boards and onto the highways.

That’s why the brands with hybrid, and even electric, logos on their deck lids are proliferating. But are they all equally desirable, or even equally practical? Let’s go down the lengthy list of possibilities, starting with the least radical first.

The biggest vehicles – full-size luxury cars and sport-utility vehicles – have come in for their fair share of criticism for their thirsty characteristics. With these vehicles, such as the BMW 7-Series hybrid, Mercedes-Benz S400 and ML 350 BlueHybrids, and GMC Yukon Hybrid, we’re seeing a “mild” version of hybridization.

In these mild hybrids, the electric motor is an integral part of the powertrain. When the car is slowing down, the momentum of the gasoline engine spins the electric motor, which generates electricity that is stored in the battery and at the same time puts a drag on the crankshaft to help slow the car.

When the car accelerates beyond the capability of the gasoline engine by itself to provide the desired power, the electric motor is engaged to add torque to the driveshaft. The electric motor can be used to start some of these cars quickly, so when they are stopped at a light, the gasoline engine can be shut off completely, then started again when the drivers take their feet off the brake.

The use of the electric motor in conjunction with the gasoline engine in these ways means that the vehicle doesn’t need as powerful an engine as would otherwise be required. In most cases, a V-6 can do the work of a V-8, but when the extra power isn’t needed, the smaller engine delivers better fuel efficiency than would the larger engine. And obviously, there is a benefit for fuel efficiency and smog reduction with the stop-start feature.

One way of telling this type of hybrid from the more complete hybrid is that it is not possible for these vehicles to be powered only by the electric motor.

A more complete version, called a “full hybrid,” is what we see in the popular Toyota Prius; the Lexus LS, RX and GX; and the Ford Escape. In these hybrids, the electric motor and gasoline engine are on separate driveshafts that can individually or together power the car through a differential. In addition to capturing energy normally lost while braking and increasing available power for acceleration, as is done with the mild hybrids, the full hybrid can be propelled solely by electric power for short distances up to 20 or 25 miles at speeds generally below 30 mph, which substantially increases fuel efficiency while at the same time reducing pollution, especially in urban settings.

By the fall, we’ll see several of the auto manufacturers take these full hybrids a step further with the introduction of “plug-in hybrids.” In these cars, such as the plug-in Prius, the addition of a larger battery pack and a charging plug enables an owner to charge the batteries while the car is parked overnight. For owners who drive solely in a low-speed urban setting and drive fewer than 50 miles on a normal day, they may be able to do most of their driving without ever starting the gasoline engine.

We’ve also just recently seen the gradual introduction of the affordable Chevrolet Volt, one of the first commercially viable vehicles known to the alternative fuel techies as “series hybrids” or “extended-range electrics.” By the fall, rumors are that the Fisker Karma, a much pricier sporty series hybrid, will be on sale on El Camino Real in Palo Alto in the old Carlsen Volvo dealership.

Surprisingly, this technology may be among the oldest in the group, since Austrian automotive engineer Ferdinand Porsche displayed an extended-range electric car at the Paris Auto Show in the first decade of the 20th century.The same technology is used in all diesel locomotives.

These vehicles are driven solely by the electric motor, which is powered from batteries charged by an onboard gasoline motor with its own generator. The electric motors powering the wheels also contribute to the battery charge when the vehicle is slowing down. Of course, the batteries can also be charged when the vehicle is parked overnight.

Vehicles like the Volt are ideal for a family that commutes during the week within the 80-100-mile range of the batteries but still appreciates being able to take a longer side trip if business or weekend activities require it. The Volt has a combined range of 350 miles or more with full batteries and full fuel tank.

Los Altos residents are among those most familiar with the concept of a “full-electric” vehicle, because we’ve seen Teslas around town for several years. These vehicles are powered solely from their electric motors and onboard battery packs, and were joined in the market this spring by the Nissan Leaf and Mitsubishi Innovative Electric Vehicle. In these cars, batteries are charged while the vehicle is parked and typically can go 50-75 miles between charges. They are excellent for commuting, or use around town, but they aren’t practical for longer trips, because they take four to eight hours to be recharged after each 75-mile trip.

Where is all this innovation likely to lead us? Given that it would take more than 10 years for any alternative-fuel vehicle to replace a significant portion of the present vehicle fleet, we can be sure that none of these innovations represents a near-term answer either to our problems of petroleum fuel dependence or vehicle emissions.

However, it seems likely that more vehicles sold within the next five years will be hybrid-powered, and the near-term fuel efficiency goals will be met by the types of hybrids – mild, full and plug-in – we’re seeing taking an increased share of new-car sales already. After that, probably the next growth will come from extended-range hybrids like the Volt, because they use present technology and have few limitations beyond the time it takes to recharge their batteries.

Beyond that, perhaps after 2020, the advantages of hydrogen fuel cells may justify the changes in infrastructure they’ll require. Your crystal ball is at least as good as ours when we look that far in the future.

 

Longtime Los Altos residents Gary and Genie Anderson are co-owners of Enthusiast Publications LLC, which edits several car club magazines and contributes articles and columns to automotive magazines and online services.

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