Electronics and Semiconductors

The potential of wireless EV charging

11 August 2023
The technology could enable in-road charging. Source: Drexel University

When it comes to charging our electronic gadgets, wireless charging has been a game-changer. Now, it's also making major inroads in the area of electric vehicles (EVs). Almost all current EVs are charged by electric cables; charging EVs requires the physical connection of wires, whether at home or on the road. These may produce sparking while plugging in or disconnecting, which severely restricts the usage of EVs in particular settings, such as at fueling stations and airports. By doing away with the need for cables and other mechanical attachments for recharging batteries, wireless charging technology presents an attractive alternative for powering EVs. Several automakers, including Tesla, BMW and Nissan, have already begun work on cable-free, wirelessly charged EVs.

How can power be transferred wirelessly?

Nicola Tesla is credited with creating the first wireless equipment, a wireless lightning lamp, in the late 19th century. Tesla's light bulb was powered by AC potentials at high frequencies between two closely spaced metal plates. This opened up new possibilities for wireless charging. But this technology progressed slowly because of unresolved technical issues pertaining to low transfer efficiencies and low power densities as distances increased.

After two centuries of development, 'strongly coupled' coils allow for wireless charging at distances greater than 2 m. The two most common kinds of wireless power transfer are inductive power transfer (IPT) and capacitive power transfer (CPT). CPT is realized by electric field interaction between coupled capacitors in the highly coupled regime, and IPT is realized via magnetic resonance coupling of the transmitting and receiving coils. The accessible area of such devices is what determines their coupling capacitance. As a result, CPT may only be used for low-power purposes with air gaps as small as 10-4 m to 10-3 m. IPT output power is far larger than that of CPT, which might go over 10 kW, and it can be utilized for wide air gaps of several meters or more.

Types of wireless charging systems in EVs

There are three main types of wireless charging systems for electric vehicles:

• Stationary,

• Semi- or quasi-dynamic, and

• Dynamic.

Similar to modern plug-in chargers, stationary systems offer "park and charge" and other convenient features. The conductive charging technology is replaced with a receiving pad on the vehicle and a charging pad in the street. Providing short-term charging in a constantly changing environment, quasi-dynamic devices can be put at bus stops, taxi stands and traffic signals. Vehicles equipped with dynamic wireless power transfer technology can be recharged even while in motion. Therefore, it recharges the battery and extends the driving range, reducing the dreaded "range anxiety." It has been stated that a new EV’s battery demand can be cut by as much as 20%, reducing initial investment. That's why wireless power transfer is so tempting for EVs; it can boost EV adoption.

Issues of public health and safety

Particularly at higher power levels, the usage of time-varying currents and voltages for wireless EV charging raises several safety and health problems. However, because of their widespread application, these dangers are well understood and may be mitigated. Electrical shock, fire and exposure to electromagnetic fields are all examples. As a result, the public's impression of health and safety in wireless power transfer is a larger problem than any actual problems with the system. The International Commission on Non-Ionizing Radiation Protection has recommended a guideline for field restrictions to reduce the effects of magnetic and electric fields on workers and the general public.

Costs of wireless power transfer

Because stationary wireless chargers require charging pads and inverters to provide high-frequency coupling between transmitting and receiving coils, they are more costly than traditional conductive chargers. Also, dynamic wireless charging is still a relatively new technology, and its economic viability has not been well explored. Currently, the massive onboard battery packs make EVs more expensive than conventional internal combustion engine vehicles. When employing stationary wireless charging, a traditional plug-in charging pad is used in place of a wall outlet.

[Learn more about wireless charging technologies and suppliers at GlobalSpec]

Wireless charging standards

Successful commercialization of high voltage and high-power wireless power transfer for EV charging necessitates standardization as wireless charging becomes a frontrunner in the market. The test infrastructure, wireless charging specifications, electromagnetic restrictions and interoperability goals are all part of the standardization process. For example, the whole system for wirelessly charging the battery or equipment in an EV using the standard supply of 1,000 V AC or 1,500 V DC is outlined in the IEC-61980-1 standard. Similarly, SAE J2954 is a wireless power transmission standard for recharging EVs produced by the Society of Automotive Engineers. It specifies what must be included in both the infrastructure for recharging automobiles wirelessly at fixed locations and in the vehicles themselves.

Conclusion

In conclusion, the advent of wireless charging for EVs is a major step forward for the industry of electric transportation. Wireless charging systems are more efficient since they do not require the use of wires or connectors; instead, they rely on electromagnetic fields. Wireless charging systems are guaranteed compatibility, safety, and efficient power transmission by standards like SAE J2954 and IEC 61980. For charging stations and vehicles to work together seamlessly, these guidelines provide the technical parameters, power levels, and communication protocols that must be followed.

To contact the author of this article, email GlobalSpecEditors@globalspec.com


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