It’s not new to think of a hybrid automobile, one that can use both an electric and conventional engine to propel it. Hybrid automobiles have been around for more than 100 years, even though the internal combustion engine wasn’t yet invented.
These cars were built to overcome the limitations of existing electric vehicles as well the difficulty of starting the engines. (A procedure that often resulted in broken arms) The early hybrid vehicles and the purely electrified cars that dominated early 20th-century automobile manufacturing eventually gave place to more cars with an internal combustion engine. This was due to the wide availability of gasoline and its relatively low cost.
Due to this, the hybrid concept was not revived until the 1970s. In that decade, gas prices increased by three times. The increased cost highlighted an inherent problem with using internal combustion engine in cars: inefficiency. Inefficiency is a result of the fact that it used to be standard practice to keep the engine going even when the car stops. The idea was to avoid having to restart it. The engine of cars is just left running, which uses fuel to do virtually nothing. The engine is normally throttled. It restricts how much air it can take in. This reduces power and efficiency, as well as reducing the vehicle’s speed. Further, the engine can even consume fuel by slowing the vehicle after it has been running at speed.
For ships and aircraft, these inefficiencies don’t cause much concern as they rarely idle or operate at an inefficient speed. The majority of automobiles run at very low power levels. The city’s average speed is only 19 miles an hour. This means that a car needs around 9 kilowatts to achieve the same power level as 12 horsepower. But, the driving public wants cars that accelerate quickly. That’s equivalent to around 150 kilowatts or about 200 horsepower. Therefore, most cars run with their engines cranked back so they only draw a fraction their power. A highway drive, which requires 12 kilowatts of power (or approximately 16 horsepower for a sedan medium-sized) can give you better fuel economy. However, highway speeds are still far less efficient than if the engines were not throttled so hard.
Space-Age Quest
The inefficiency inherent to the engines that drive cars and trucks has been well known. After gasoline prices and availability became a problem three decades ago automobile engineers began to seek out better alternatives. The hybrid car concept proved very attractive.
After working for more than a ten years in industry, I was a young professor at University of Wisconsin in 1970. Since I had extensive knowledge in aerospace technology, it was natural for my to seek out ways to increase the efficiency of the automobile’s fuel consumption. I set myself the goal of creating a car capable of getting 100 miles per gallon with performance equal or better to the conventional car. This is a little faster than the national speed limit of 55 miles an hour, which was set in 1974. However, I was afraid that my goals would be mocked by the funding agencies.
I explored the possibility of achieving my goals with a hybrid that utilized the technology available at the time. But the batteries I had at the time, whether they were nickel-cadmium (or lead-acid), were too heavy to produce power or store the energy needed for the desired power-leveling effect. The concept of an automobile that had two energy sources on board was conceptually sound. However, it was difficult to envision the average American grandmother operating a vehicle with more control than a steering, accelerator and brake pedal. How could the driver manage the two different power sources? Another difficult issue was having enough power available for any maneuver the driver wanted. This could include passing trucks on a steep grade or driving the vehicle quickly to highway speed up an on-ramp.
You can satisfy this requirement by keeping the engine size the same as it would be in a normal car. The hybrid vehicle can still use its engine to power the needed power. Another way is to use a large, high-energy battery pack to provide sufficient energy for the longest anticipated maneuver. This will allow the designer to reduce both the engine’s weight and the engine. My students, along with me, began exploring these options by creating and building prototype vehicles in contests hosted by the U.S. Department of Transportation. From our first work, it became clear what the challenges were in engineering hybrid cars.
One of the key missing pieces was an efficient and lightweight energy storage device that could instantly generate high levels of power. Another gap was a computer capable of managing multiple sources simultaneously. It would have the ability to deliver power to the wheels, as well as slow the car down to turn the kinetic energies of motion into electricity. This will allow the battery to be recharged later. Another important element was a transmission that could effectively handle multiple powerplants.
My research, as well as that of many of the automotive engineering colleagues I knew, quickly moved to technical solutions to these challenges. Our first efforts were directed towards developing a storage method for energy that was not in an electrical battery. The DOE became aware of energy-storage flying wheels and launched a program that would allow them to make mobile flywheels with enough energy to travel 100 miles. Scientific Americanpublished rough calculations showing that it was possible for a flywheel of this type to be made. There were, however a few technical problems that were not addressed in the article. It ignored the fact that a vehicle device could safely transport an immense amount of kinetic and spinning energy.
This approach seemed to be a winner because it was made of composite material. If it failed, it would instantly become a bunch randomly arranged fibers. All the energy would then be lost as heat. Because of the law governing conservation of momentum, other more dangerous failure modes are more likely. Safety precautions were therefore necessary. This simple fact was ignored by many of the top researchers in industry and government laboratories. After some disastrous accidents, a lot of money was spent, the DOE Program was canceled at end of ’70s. In the meantime, I had created two flywheel powered cars and demonstrated that such vehicles could achieve 50 % better fuel economy. The hybrid flywheel would get around 35 mpg, but that would still be a significant improvement on my original goal of 100 mpg.
These flywheels weren’t as energy efficient as they could have because of their large size and weight. My colleagues and I designed the hybrid car’s flywheel system. It weighed in at 500 pounds. Modern electrochemical batteries can store 20 to 30 times more energy. These hybrid cars had engines that could not be reduced in size because the flywheels did not have enough energy to allow for long maneuvers. It was impossible to balance the extra weight of the flywheel by using a lighter engine.
California Air Resources Board, an authority charged with cleaning California’s overcast skies, realized that it was possible to make zero-emission cars powered solely by electricity from its power grid. This would shift emissions away from tailpipes and into central power plants that could better control pollutants. The key was a reliable electrochemical lithium battery. Ovonic Battery Company and other battery makers discovered that the metalhydride battery could store enough power to make an electric vehicle feasible. This was the reason why many companies began researching the topic.
Al Gore, the then vice-president of the Partnership for a New Generation of Vehicles led a government and industry effort that gave the program additional momentum. California’s plans for electric cars were too ambitious. The program managers decided to make a gasoline-burning vehicle three times more efficient than a conventional car. To achieve such mileage, a hybrid was the only option. That would require one or more electrochemical cells. Electrochemical cells were also developed in response to the possibility of auto makers building such cars in larger quantities.
In 1995, batteries technology had reached a point that was suitable for hybrid cars. Designers were then required to reduce overall costs to a level that was competitive. Toyota and Honda introduced the first hybrid cars in the market in late 1990s. These vehicles demonstrated that there was a way to significantly improve fuel economy without having to pay a high price. Every car company has realized that more people will pay more for better fuel economy, and this should help to drive down costs. The hybrid powertrain is a new standard in automotive technology.