慶應義塾大学 - 電気自動車研究室
Electric Vehicles
Exhaust and Energy Efficiency
We believe that electric vehicles are the cars of the future, chiefly because they are far more energy-efficient than conventional internal combustion (gasoline-powered) vehicles.
Plus, using solar cells to generate energy, we can create vehicles that use no fossil fuels at all. Of course such vehicles produce no exhaust gases or noise, either.
Over recent years many people have noticed an increase in unusual new kinds of vehicles, such as hybrid cars, fuel-cell vehicles, and automobiles powered by natural gas. Broadly speaking, however, there are only two types of automobile: internal-combustion and electric.
Internal combustion vehicles obtain their power by exploding fuel inside the engine.
Gasoline and diesel have long been used to fuel such engines. There have also been a few attempts to use compressed natural gas. By adding an electric motor to such vehicles, we can create cars with lower fuel consumption, called parallel hybrids. The hybrid cars appearing on our roads are of this type, and can be termed electrically-assisted gasoline vehicles.
Electric vehicles, on the other hand, run on the power of an electric motor. They can be divided into several types, depending on the sources providing electric power to the motor.
In the narrow sense, the term “electric vehicle” means a vehicle that runs on power stored in batteries that can be repeatedly recharged. Fuel cell vehicles run on fuel cells that combine hydrogen with oxygen to generate power. Other cars have a generator attached to the engine and run on the power it creates. These are called series hybrids.
We believe that cars running on power stored in batteries will win out, because the technology is highly efficient, technologically simple, and has few parts.
Past electric vehicles have not performed well. Moreover, they have been regarded as expensive and thus have not succeeded in the market. When we examined the reasons people accept cars, we realized that they value acceleration, space, and comfort.
Of course, the design also has to be pleasing. We believe that if electric cars surpass gasoline vehicles in terms of these three values, people will happily accept them.
Fortunately, three technologies useful for improving the performance of electric vehicles were invented around the end of the 20th century, and they are already being widely used.
The three technologies are lithium-ion batteries, neodymium magnet motors, and insulated gate bipolar transistor (IGBT) inverters (speed converter).
Years of research have shown that adopting new technologies to change the structure of electric vehicles enables us to drastically improve their performance and to enhance their comfort by greatly expanding the usable space compared to the overall size of the vehicle.
Research has also drawn our attention to the three key values of acceleration, space, and comfort. Electric vehicles are a dramatic solution to environmental problems, but in developing such vehicles we are always conscious that they must surpass gasoline-powered automobiles in terms of these three values if they are to become widely used.