"Automakers need to get serious about shifting their technology to greater fuel-efficiency, consumers need to get serious about buying hybrid cars, and Washington needs to get serious about working together to find a real solution to our energy crisis"

- Barack Obama in a speech to the Governor's Ethanol Coalition, Feb. 28, 2006

Fast forward to 2008. There's a growing consensus among Americans that our "addiction" to oil is the root cause of many of our economic and security problems. Buying hybrid cars will be part of the solution.

We find that most websites dedicated to hybrid cars fall into one of two categories. Either they are too heavy on technical details or they are light on details and heavy on advertising.

We are dedicated to bringing unbiased information to consumers about buying hybrid cars.

We'll describe the engineering in plain English. We will track the latest news about hybrid cars and discuss the latest developments.

Hybrid car sales, led by the Toyota Prius, increased 38% to a record 350,289 vehicles in 2007. Nissan Motor Co. is pumping billions into environmental initiatives. Looking ahead, Nissan continues development work to commercialize hydrogen fuel cells for automotive use. This is another company to watch.

Barack Obama's current Energy Plan for America calls for the production of 1,000,000 plug-in hybrid cars by 2015. Hybrids are coming.

Cost will continue to be a key factor for consumers. Various tax credits are used to calculate the cost of hybrid cars. We'll be watching for news from the IRS about the latest tax rules. Visit the IRS website for up-to-date information on available tax credits: Alternative Motor Vehicle Credit

The gasoline-electric hybrid car is just what it sounds like -- a cross between a gasoline-powered car and an electric car. Let's start with a few diagrams to explain the differences between a gasoline-powered car and a typical electric car.

A gas-powered car has a fuel tank, which supplies gasoline to the engine. The engine then turns a transmission, which turns the wheels.

An electric car, on the other hand, has a set of batteries that provides electricity to an electric motor. The motor turns a transmission, and the transmission turns the wheels.

The hybrid is a compromise. It attempts to significantly increase the mileage and reduce the emissions of a gas-powered car while overcoming the shortcomings of an electric car.

To be useful to you or me, a car must meet certain minimum requirements. The car should be able to:

A gasoline car meets these requirements but produces a relatively large amount of pollution and generally gets poor gas mileage. An electric car, however, produces almost no pollution, but it can only go 50 to 100 miles (80 to 161 km) between charges. And the problem has been that the electric car is very slow and inconvenient to recharge.

A gasoline-electric car combines these two setups into one system that leverages both gas power and electric power.

Gasoline-electric Hybrid Structure

You can combine the two power sources found in a hybrid car in different ways. One way, known as a parallel hybrid, has a fuel tank that supplies gasoline to the engine and a set of batteries that supplies power to the electric motor. Both the engine and the electric motor can turn the transmission at the same time, and the transmission then turns the wheels.

The animation below shows a typical parallel hybrid. You'll notice that the fuel tank and gas engine connect to the transmission. The batteries and electric motor also connect to the transmission independently. As a result, in a parallel hybrid, both the electric motor and the gas engine can provide propulsion power.

By contrast, in a series hybrid (below), the gasoline engine turns a generator, and the generator can either charge the batteries or power an electric motor that drives the transmission. Thus, the gasoline engine never directly powers the vehicle.

Take a look at the diagram of the series hybrid, starting with the fuel tank, and you'll see that all of the components form a line that eventually connects with the transmission.

The structure of a hybrid car harnesses two sources of power to increase efficiency and provide the kind of performance most of us are looking for in a vehicle. In the next section, we'll see how it accomplishes this.

The Power Split Device

The power split device is the heart of the Toyota Prius. This is a clever gearbox that hooks the gasoline engine, generator and electric motor together. It allows the car to operate like a parallel hybrid -- the electric motor can power the car by itself, the gas engine can power the car by itself or they can power the car together. The power split device also allows the car to operate like a series hybrid -- the gasoline engine can operate independently of the vehicle speed, charging the batteries or providing power to the wheels as needed. It also acts as a continuously variable transmission (CVT), eliminating the need for a manual or automatic transmission. Finally, because the power split device allows the generator to start the engine, the car does not need a starter.

The power split device is a planetary gear set (below). The electric motor is connected to the ring gear of the gear set. It is also directly connected to the differential, which drives the wheels. So, whatever speed the electric motor and ring gear spin at determines the speed of the car.

Planetary gear box

The generator is connected to the sun gear of the gear set, and the engine is connected to the planet carrier. The speed of the ring gear depends on all three components, so they all have to work together at all times to control the output speed.

When you accelerate, initially the electric motor and batteries provide all of the power. The ring gear of the power split device is connected to the electric motor, so it starts to spin with the motor. The planet carrier, which is connected to the engine, is stationary because the engine is not running. Since the ring gear is spinning, the planets have to spin, which causes the sun gear and generator to spin. As the car accelerates, the generator spins at whatever speed it needs to in order for the engine to remain off. You can see all of this below:

Watch the Prius' power split device
as the car accelerates from 0 to 30 mph.

Once you reach about 40 mph (64 kph), the gasoline engine will turn on. The generator suddenly changes speed, causing the planet carrier to turn and start the engine. Once the engine is running, it settles into a constant speed while the generator varies its speed to match the output speed with the electric motor. If you are really accelerating hard, the motor will draw extra power from the batteries. Once you are up to freeway speed, the car will move under a combination of gas and electric power, with all of the electricity coming from the generator.

Like the Insight, the Prius never needs to be recharged; the onboard generator automatically maintains the proper level of charge in the batteries.

Both the Honda and the Toyota have long warranties on their hybrid components. The Insight has an eight-year/80,000-mile warranty on most of the powertrain, including batteries, and the Prius has an eight-year/100,000-mile warranty on the battery and hybrid systems. The motors and batteries in these cars typically don't require any maintenance over the life of the vehicle (however, if you do have to replace the batteries after the warranty expires, it will likely cost you several thousand dollars). The engine doesn't require any more maintenance than the one in any other car, and because both hybrids have regenerative braking, the brake pads may even last a little longer than those in most cars.

Achieving hybrid power is certainly more complex than using straight gasoline power or straight electric power. In the next section, we'll examine why hybrid technology is so desirable, both for consumers and for car makers.

The most common references to hybrids are to the type that can be described as hybrid-electric vehicles (HEV).

Any vehicle that combines two or more sources of power that can directly or indirectly provide propulsion power is a hybrid. Most hybrid cars on the road right now are gasoline-electric hybrids,

The Benefits of a Hybrid Car

You might wonder why anyone would build such a complicated machine when most people are perfectly happy with their gasoline-powered cars. The reason is twofold: to reduce tailpipe emissions and to improve mileage. These goals are actually tightly interwoven.

Let's take the example of the California emissions standards, which dictate how much of each type of pollution a car is allowed to emit in California. The amount is usually specified in grams per mile (g/mi). For example, the low emissions vehicle (LEV) standard allows 3.4 g/mi of carbon monoxide. The key thing here is that the amount of pollution allowed does not depend on the mileage your car gets. But a car that burns twice as much gas to go a mile will generate approximately twice as much pollution. That pollution will have to be removed by the emissions control equipment on the car. So decreasing the fuel consumption of the car is one of the surest ways to decrease emissions.

Carbon dioxide (CO2) is another type of pollution a car produces. The U.S. government does not regulate it, but scientists suspect that it contributes to global warming. Since it is not regulated, a car has no devices for removing CO2 from the exhaust. A car that burns twice as much gas adds twice as much CO2 to the atmosphere.

Auto makers in the United States have another strong incentive to improve mileage. They are required by law to meet Corporate Average Fuel Economy (CAFE) standards. The current standards require that the average mileage of all the new cars sold by an auto maker should be 27.5 mpg (8.55 liters per 100 km). This means that if an auto maker sells one hybrid car that gets 60 mpg (3.92 liters per 100 km), it can then sell four big, expensive luxury cars that only get 20 mpg (11.76 liters per 100 km).

You can actually take steps to drive your car in ways that increase its gas mileage. In the next section, we'll look at some tips for increasing the efficiency of your hybrid (or just gas-powered) car

Because of their promise of improved fuel economy and reduced tailpipe emissions, vehicles employing hybrid drivetrain technology have drawn the attention of both the media and automotive consumers. There is no question that the technology works, typically providing fuel economy gains of 25-40 percent when compared to similar vehicles with conventional drivetrains.

Looking for ways to further improve fuel-economy, manufacturers are exploring enhancements to the basic hybrid concept. One promising avenue is the plug-in hybrid car. In simplest terms, plug-in hybrid cars incorporate traditional hybrid technology but benefit additionally from plug-in charging.

While several manufacturers claim to be working on the technology, General Motors' Saturn division has promised to introduce a plug-in hybrid version of its Vue SUV by 2009.

More likely, fuel consumption would decrease dramatically in routine commuting, though the reduced cost of gasoline is offset to some extent by increased electricity usage.

Pure Plug-in Concepts:
The Chevrolet Volt Concept and Ford Edge with HySeries Drive

While Vue will be able to run on its gas engine after the battery's power is exhausted, Volt Concept's motor will soley get its power from the electric battery. This concept car is most notable for what it doesn't have than for what it does. Not a hybrid in the conventional sense, the Volt's gasoline engine never powers the vehicle's wheels. Instead, in the event that the car's plug-in charge is depleted, a small gasoline engine is used to power a generator that supplies back-up electricity. As the gasoline engine never provides power directly to the drive wheels, Volt does not require a conventional transmission.

Relatively light and compact, Volt's three-cylinder engine weighs less than a long-range battery pack might, and consumes less space. The gas backup provides an added dimension of range as well as flexibility, providing immediate power when time for a full battery charge may not be available.

Though displayed only with the gasoline engine at the 2007 North American International Auto Show in Detroit, Chevrolet says that Volt's backup power could also be provided by a diesel engine or a hydrogen fuel cell.

While the stylized two-seat Volt is not a likely candidate for production, its gas-assisted electric drivetrain may someday find its way into Chevrolet's lineup.
While more conventional in appearance, the Ford Edge with HySeries Drive Concept showcases technology very similar to Volt. Introduced at the 2007 Washington Auto Show, the Edge HySeries features electric drive with power coming from either a plug-in charged battery, or a hydrogen fuel cell.

Unlike the Volt Concept, which uses another power source to supplement the plug-in charge, Edge HySeries uses plug-in charging as a backup for the fuel cell.

Fuel cells, like the one in HySeries, create electricity-using hydrogen as fuel. Because hydrogen-filling facilities are scarce, the plug-in electric backup power source adds a much-needed dimension of range and safety.

While Volt is purely a concept vehicle, the Edge HySeries is completely functional, though a similar regular-production vehicle is unlikely in the near future.

These concepts from Chevrolet and Ford look down the road at another generation, one working toward the end goal of fossil-fuel independence. In time, they may be able to bridge the gap between gasoline and electric powered cars; making the goal of an automotive landscape virtually independent of fossil fuels a reality.

The Benefits of Plug-In Hybrid Cars

So, what are the benefits of plug-in hybrid cars? Plug-in hybrid drivetrains may seem like a complicated solution to a simple problem, but in reality they address the two fundamental issues that have prevented pure electric vehicles from becoming economically viable: range and weight.

Though battery technology has improved dramatically in recent years, the potential range of a pure electric vehicle is still below the roughly 300-miles of travel a typical consumer expects from a tank of gas.

According to Saturn, with a pure-electric range of up to 40 miles, the Vue plug-in hybrid will accommodate the 80 percent of consumers who live within a 20-mile radius of where they work. For these drivers, the gasoline engine would only be used to provide extra power for acceleration, passing, and merging.

Because the drivetrain is engineered for maximum efficiency in daily short-range driving, a plug-in hybrid is not saddled with what Saturn estimates is 400-600 pounds of additional battery capacity.

Given that it should be possible to always drive a plug-in hybrid vehicle within the range of its plug-in battery capacity, and gently enough to avoid requiring power assistance from the engine, it is theoretically possible to never consume gasoline.

Expanding further on plug-in hybrid technology are two vehicles still in the concept stage. The Chevrolet Volt, which was introduced at the 2007 Detroit Auto Show, and the Ford Edge with HySeries Drive, also introduced in 2007, combine elements of plug-in charging with other potentially fuel-conserving technologies.

The following article will explain exactly how plug-in hybrid cars work. It also will examine some of the benefits of plug-in hybrid cars.

Plug-in Hybrid Cars Explained

In summary, current hybrid vehicles have a gasoline engine that is assisted by an electric motor, which helps it save gas. A typical hybrid vehicle conserves fuel a few different ways. It recaptures energy lost through braking and decelerating. This recaptured energy is stored in a battery pack as electricity. As demand warrants, the stored electricity is used to power an electric motor that assists the vehicle's gasoline engine--usually during acceleration.

Many hybrid vehicles conserve additional fuel by incorporating a shut-off system that shuts down the engine during stops. In these cars and trucks the electric motor alone may propel the vehicle for short distances.

Hybrid vehicles available today are closed systems, and do not require plug-in charging. A plug-in hybrid vehicle expands on the hybrid concept by allowing for the battery pack to be even further recharged through plug-in charging. According to Saturn, the Vue plug-in hybrid will use a conventional electric cord that can be plugged into any 110-volt household wall outlet.

While a conventional hybrid vehicle may travel short distances in pure-electric mode, plug-in hybrids are designed to travel extended distances with little or no assistance from the gasoline engine. Even before the charge is depleted, the gasoline engine may be called on to provide additional power for recharging the battery, accelerating, passing, and merging.

While operating on the additional plug-in charge, a plug-in hybrid more-or-less works the opposite of a conventional hybrid, with the electric motor acting as the primary power source, and the gasoline engine providing supplemental motivation. In the case of the Vue, once the initial charge is depleted, it would operate just as conventional hybrid does, using the gas engine. The Chevrolet Volt Concept is designed to use only its electric motor, using gasoline only to aid in battery recharging, not driving.

To keep vehicle weight inline with a conventional hybrid, plug-in hybrids would have little or no additional battery capacity. As such, the distance a plug-in hybrid will travel in pure-electric mode will be relatively modest. Saturn has suggested distances as great 40 miles, and as low as 20; GM estimates that the Volt Concept could travel an average of 40 miles per charge.