Published on October 21st, 2007 | by Stephanie Evans0
Gas-Electric Hybrids Reach the Mainstream
Cars have always been a status symbol for those who drive them. Now that the hybrid is available to more than just celebrities, gas-electric hybrid cars have become the new status symbol for the green consumer. But watch out for deceptive marketing and assumptions about intrinsic environmental friendliness—not all “hybrids” are the same shade of green.
A Hybrid is a Hybrid—or Not?
A rising wave of concern about the climate crisis and steeper prices at the pumps have shifted consumer focus to greener cars, such as hybrids. Automakers have taken notice, and many major manufacturers are hopping onto the hybrid bandwagon. Step 1: License some technology from companies ahead of the curve and graft it onto your own. Step 2: Slap a hybrid badge on the side. Step 3: Smile smugly as you watch your sales take off.
Hold your horses, partner—is it really as simple as 1–2–3? What makes a hybrid a hybrid, anyway?
A hybrid-electric vehicle (HEV) is so-called because it is powered by both electricity (through an electric motor and batteries) and by another form of power (such as gasoline or diesel). The most mature and popular combination uses the gas-powered internal combustion engine, although diesel-electric hybrids are being introduced into public transit bus fleets.
The Five Steps to Hybridization
According to the Union of Concerned Scientists at Hybridcenter.org, there are five technology steps to hybridization:
- Idle-off: This feature is the ability to turn off the gas engine when the vehicle is stopped, so fuel isn’t wasted and emissions aren’t generated while you’re waiting at the stoplight. While all hybrids have this capability, not all vehicles have it are hybrids. Idle-off capability can be accomplished without the large, fully functional electric motor in hybrids.
- Regenerative braking: This feature is the ability to capture the kinetic energy of a braking car by turning the electric motor into a generator. In a conventional car, the kinetic energy is lost when the brakes turn it into waste heat. In a hybrid, the kinetic energy charges the batteries, which power the electric motor. Some manufacturers may claim to use regenerative braking, but this doesn’t count if this implementation can’t recover enough energy to affect fuel economy.
- Power assist: In a hybrid, the electric motor complements the gas engine, allowing the vehicle to achieve greater performance for less fuel consumption. As a result of the power assistance, engines for hybrids can be smaller and lighter than those required by their conventional counterparts. However, “muscle hybrids” use the power assistance to enhance performance without downsizing the engine.
- Electric-only drive: This feature enables the electric motor to take the lead instead of playing a supporting role. At low speeds (10–20 mph), the electric motor goes solo and handles all the driving. This feature improves efficiency because it allows the gas engine to operate in its most efficient range. Better yet, electric motors have better acceleration at low speeds than gas engines do (in car-speak, electric motors have great low-end torque).
- Range extension: In the hybrids of today, regenerative braking or the gas engine recharges the battery, and the electric-only drive kicks in only for extremely low speeds. However, the ability for battery recharging by plugging into a grid or clean power source would allow for operation closer to a true electric vehicle. With a larger battery and electric motor, many urban and commuting trips could be satisfied on electric drive alone.
The first three steps make a mild hybrid. The fourth makes a full hybrid, and the last makes a plug-in hybrid. While mild and full hybrids are already on the roads, plug-in hybrids aren’t anywhere near production yet.
As the five steps clearly show, hybrids are about moving from conventional fossil fuel powered vehicles to fully electric vehicles. They’re stepping stones to something higher, better, and greener. While we’re waiting for the electron economy to gain traction, hybrids provide a place in-between for people to get used to electric drive, for engineers to make breakthroughs in battery technology, and for electric motors to become mass-production cheap. Progress takes time, sweat, and money—hybrids give us the time and money to sweat it out.
The technology that goes into today’s hybrid car is the precursor (and in many cases, the same) as the technology that will become tomorrow’s electric transportation pod. So when you buy that hybrid, you’re not just doing a good turn for Mother Nature in the way of low carbon emissions, but also by paving the way for zero emission vehicles someday soon (all the sooner, because of you).
Green is as Green can Be
The five technologies listed are only an approximate guide to the greenness of a vehicle—they’re more like indications of potential greenness than actual environmental performance. The only way to know a hybrid’s true shade of green is to look at its fuel economy and tailpipe emissions.
While every step towards a fully electric vehicle improves the potential for better fuel economy, fuel efficiency isn’t inherent in hybrids. Hybrid systems are necessarily complex, and any of poor mechanical, electrical, or software design can get in the way of true fuel efficiency. In addition, the existence of muscle hybrids clearly shows that fuel economy minded design is a requirement for true gains in fuel efficiency.
However, increasing fuel economy over that of conventional vehicles is kind of like going downhill. Controlling tailpipe emissions, on the other hand, is more like going uphill. While fuel economy and carbon emissions go hand in hand, other air pollutants don’t. These pollutants are primarily formed when the engine first starts up—and in a hybrid, that happens a lot more than it does in a conventional vehicle. Having the idle-off capability in mild hybrids and the electric-only drive feature in full hybrids indicates that the gas engine is shut off more often. This results in higher pollution output every time that the engine restarts and warms up. On the other hand, because downsized engines are smaller and lighter, they heat up faster, reducing that warm-up period. The cooling system can also keep the engine warm between uses, eliminating the warm-up period altogether.
Another problem with tailpipe emissions has to do with the evaporative canister, which stores unburned fuel vapour when the engine is turned off. In a conventional car, when the engine is restarted, the canister is purged and the engine burns the fuel. In hybrids, engines operate for a shorter time and less frequently, so they might not completely purge the canister. When the engine shuts off, the canister might overflow, leaking smog-causing chemicals into the air. A larger canister and a completely sealed fuel system are possible solutions to this problem.
Although there are challenges to low emissions vehicles, some of today’s hybrids already meet stringent emissions requirements (California’s Super Ultra Low Emission Vehicle standards). Stellar environmental performance might not be a given, but it can be achieved. That’s why you should take a hard look at the fuel economy and emissions ratings before you buy anything on four wheels labeled “hybrid.”