1 Introduction
With the rapid development of my country's economy, the country has
introduced a series of policies for energy vehicles such as corresponding
preferential policies, subsidy policies, and trade-in policies for old ones,
which further promotes the increase in private cars. Internationally, energy and
environment have become the most concerning issues in the world. The shortage
and substitution of energy, environmental pollution and protection have jointly
promoted the vigorous development of new environmentally friendly cars.
Electric vehicles are the first environmentally friendly new energy
vehicles developed, including battery electric vehicles, hybrid electric
vehicles and fuel cell electric vehicles. Among them, fuel cell electric
vehicles are environmentally friendly new energy vehicles that will be the
mainstream development in the future, but their technology is still in the
research and development stage and the cost is too high; the power supply of
hybrid electric vehicles mainly comes from generators driven by internal
combustion engines, which can only be used under the energy crisis. It is a
transitional product. This article mainly studies pure battery electric
vehicles.
Battery electric vehicle technology has been basically mature, many
manufacturers are already vigorously producing them, and charging stations are
also being constructed in various places. However, the charging problem of
battery electric vehicles has always been a headache for researchers. According
to existing application results, it takes half an hour to charge a general
battery, and more than 8 hours to fully charge it. Moreover, a fully charged car
can generally only travel more than 100 kilometers. . This obviously makes
battery electric vehicles incomparable with internal combustion engine vehicles.
Therefore, the solution of charging technology will greatly promote the
development of battery electric vehicles.
2 History of wireless charging technology
More than 100 years ago, a Serbian-American electrical engineer and
physicist named Nikola Tesla was already dreaming of a world without wires. In
1891, he invented the Tesla coil, which produced high-frequency wireless
High-voltage current, but the current of this high-voltage current is extremely
small and cannot be applied in actual use. At that time, Tesla used these coils
to conduct a series of experiments, pioneering wireless power transmission.
Tesla once said that wireless charging will be the ultimate way to make the
electric power industry prosperous. In 1901, Tesla began his research in Long
Island, New York. His goal was to make electrical energy travel across the ocean
like radio waves. However, due to the huge investment, this technology was
stillborn.
3 Development status of wireless charging technology
Although the Tesla coil was not implemented at the time, later generations
completely confirmed the feasibility of this solution in theory. After years of
research, scientists believe that wireless power transmission is possible.
Wireless power transmission is a special power supply method that is different
from wired transmission. Currently, it mainly includes three different methods:
electromagnetic induction, electromagnetic resonance and radio waves.
3.1 Electromagnetic induction
This is currently the most common transmission method. The coils at the
transmitting end and the receiving end induce each other to generate current,
thereby realizing power transmission. In 2010, a technology company displayed a
mobile phone wireless charger that used the principle of electromagnetic
induction. The power of this method can reach several hundred watts, but the
distance between the two coils cannot exceed 1 cm, and the coil and circuit of
the end product must be shielded to prevent interference. In addition, the
transmitter must have the ability to intelligently identify the product being
charged. Prevent energy from being transmitted to other devices, causing energy
waste.
3.2 Electromagnetic resonance
Electromagnetic resonance is a method of power transmission currently being
researched. In 2008, Intel engineers used this technology as a basis to make a
60 W light bulb glow 3 feet away from the power source. According to
calculations by relevant scientists, the power of this method can reach several
kilowatts and the distance can reach 3 to 4m. However, due to the large diameter
of the coil required for the current experiment, it is still in the experimental
stage. In addition, the corresponding frequency must be tested. Protection to
prevent electromagnetic waves of the same frequency from interfering and
reducing efficiency.
3.3 Radio waves
Radio waves are another relatively mature wireless charging method. Its
principle is similar to the early use of mineral radios. It uses miniature
high-efficiency receiving circuits to capture radio waves reflected from
obstacles, and then converts them into stable DC voltage. Powercast claimed as
early as 2007 that it could use RF broadcasts to charge consumer electronics
devices smaller than a cellular phone from up to several meters away. However,
the power of this method is low: no more than 100mW; the distance is short: no
more than 10m; the efficiency is low; and the charging time is long.
4. Application of wireless charging in electric vehicles
How is wireless charging applied to electric vehicles? Below, we will
briefly study and analyze charging locations, charging methods, and rechargeable
batteries, and finally propose specific application methods of wireless charging
in electric vehicles.
First, choose the charging location. Wireless charging technology is
related to the distance and status of the charger and the device being charged.
That is to say, the distance between the two cannot be too large, and there is
no relative movement between the two, otherwise power cannot be transmitted
stably and effectively. Therefore, the charging location can only be the place
where the car stays, that is, a garage, a parking lot, an intersection, etc. The
bus charging device can also be set up at a bus stop. Of course, special
charging stations can also be set up in places or beside highways where
conditions permit to facilitate vehicle charging.
Secondly, the choice of charging method. It can be seen from the three
charging methods that the distance required for electromagnetic induction
charging is too small and the efficiency of radio wave charging is too low,
while the distance and efficiency of electromagnetic resonance charging can meet
the needs of battery cars.
Finally, the choice of rechargeable batteries. Electric vehicles will be
charged at any time in the city, so it is necessary to choose batteries that are
pollution-free and have no memory effect for charging.
After comparison and selection, we have a clearer idea of the application
of wireless charging in electric vehicles: On the one hand, in the construction
of roads and construction projects, the power supply unit will pre-install
parking spaces at intersections, public parking lots, units or according to the
planning drawings. Wireless charging chargers should be buried under parking
spaces and garages in the community, and the chargers should be connected to the
power grid or solar panels; on the other hand, car manufacturers should install
wireless charging receiving devices at the bottom of the car and connect them to
the battery, etc. Equipment connection; in addition, relevant national
departments must unify the frequency of transmitting and receiving signals to
make them universal.
5 Issues that should be paid attention to in the application and
development of wireless charging technology
(1) The state should introduce corresponding policies to encourage, support
and regulate the development of wireless charging vehicles and the construction
of charging facilities. The development of an industry or enterprise, especially
an industry or enterprise that benefits the country and the people, cannot be
separated from the support of the state. Wireless charging is a field that has
just started. Its effective development can largely solve a bottleneck in the
development of electric vehicles. However, due to the huge investment in its
research and development, it requires more encouragement and support from the
state to speed up its research and development process. , so that it can be
applied as soon as possible.
(2) No matter what charging method is used and what kind of battery is
used, relevant national and local departments must conduct research on its
frequency, safety, environmental protection, energy saving and other aspects to
avoid waste, adverse effects on human health, and It will cause new pollution to
the environment, and at the same time, publicity must be in place to avoid
people's fear of electromagnetics.
(3) In practice, since the transmitter is placed underground, attention
should be paid to its protection.
(4) In areas with a lot of rain, in addition to the waterproofing of
underground facilities, the waterproofing treatment of the vehicle receiving end
is also an issue that needs to be considered.
6 Conclusion
Wireless charging technology is still in the research and development
stage, but many countries have applied it to charging mobile phones, computers,
Walkmans and other devices. Among them, the United States, South Korea, Japan
and other countries have also begun research on wireless charging cars. As this
technology continues to improve, it will surely promote the development of
battery vehicles, reduce our dependence on oil, protect the environment, and
benefit mankind.
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