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Since electric vehicles have overwhelmingly higher energy
efficiency than gasoline vehicles,their widespread use is desired
for an ecological and clean automobile society.
The following three points are well known as major factors
hindering the spread of current electric vehicles.
1: short range 2: long charging time 3:high vehicle price
Since it is necessary to install a large-capacity battery to extend the cruising range, the charging time will be longer.
In addition, vehicles become heavier, which reduces energy efficiency.
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It is a vicious circle that a large-capacity battery is required to drive a heavy vehicle.
Some sort of breakthrough technological innovation is essential to break out of this vicious cycle and build an energy-saving and clean society
in which electric vehicles are the mainstream means of transportation.
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As a breakthrough in solving the problem of electric vehicles,
Toyohashi University of Technology has been researching the possibility of "Electrified Road Electric Vehicles (EVER)".
The EVER system is an ideal electric vehicle that does not have
a large-capacity battery and runs like a streetcar by collecting energy from the road infrastructure.
In other words, it is a paradigm shift from“charging while the vehicle is stationary”to“charging while driving”.
Construction of road infrastructure is necessary, but it does not mean electrification of all roads throughout the country.
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At least the highways and major arterial roads should be electrified.
This way, for example, you can drive from your home to the entrance
to a highway on a small battery, and on the highway you can run on energy from the road surface.
By doing this, electric vehicles will be affordable for ordinary households,
and they will be a means of transportation that can reach long distances without charging on the way.
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In-motion charging is a technology that continuously delivers energy from the road to a moving electric vehicle.
We focused on the fact that car tires are always in contact with
the road surface. But what is it?
Almost all tires commonly used in automobiles today have a steel belt embedded near the tread surface.
Using the fact that this steel belt is a conductor, this makes it
work as if it were a pantograph.
This is the innovative wireless power transfer system "V-WPT:
Via-Wheel Power Transfer".
On the infrastructure side, electrodes will be laid under the road instead of overhead wires.
The electrode can be a conductive flat plate or a sheet in which thin wires are woven into a mesh, so it can be expected
that maintenance during road construction and repair will be easy.
The tire is always in contact with the road surface, but the tread surface is made of rubber,
so the normal 50/60Hz current does not flow at all.
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Therefore, we devised a mechanism that converts the electric current
into high-frequency,energy of several MHz or higher and supplies
it to the tires.
High-frequency energy has the property of flowing through materials
that are not electrically conductive. This is called "displacement current".
Does this idea have practical power transfer efficiency?
We built an experimental system to test it.
There is no special ingenuity in the tire material, and the commercially
available radial tires for passenger cars are used as they are.
I connected a 60W incandescent bulb between the left and
right axles to show the energy transfer.
As a result, energy from the high-frequency power source was transferred
through the tires to the wheels, causing the incandescent bulbs to glow brightly.
According to the measurement result, 80% of high frequency transmission efficiency is achieved.
This is an epoch-making first step that opens up a new path for electric vehicles.
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