Resonant Inductive Coupling And Wireless Charging For Electric Cars
The move toward EV (Electric Vehicles) will require more charging stations in place of gas stations. A Tesla Model 3 has an average range of 340 miles (353 miles on performance model, 263 miles standard) from a fully charged battery. This is given that the battery is not used for other charging (laptops, smartphones, etc.), so that is the theoretical range. In reality it would be closer to 295 miles on average, give or take. While the range an EV can travel before recharging is a known issue, the time it takes to charge is another factor that can be a concern.
Charging Time And Location Availability
While increasing the number of charging stations addresses range anxiety, it does not resolve the issue of charging times. You can load up gas much faster than 5 minutes at a gas station, while at a charging station it could take between 15–30 minutes (depends on the battery design specification) to reach a battery’s half level or greater. Charging an EV is much like charging a smartphone, where you have to plug a port to an outlet to recharge the battery. Unfortunately it is not currently (as of mid-2021) faster than 5 minutes.
Tesla has been improving battery capacity and efficiency over time. Other types of battery are being developed to decrease the amount of time for charging, using ultra fast charging techniques. Charging a Tesla Model 3 from a low capacity close to 0%, will take about 11 hours and 45 minutes using 220VAC at home on the average. It is faster at a charging station, at 22 minutes to reach a level over half the battery capacity (followed by trickle charging) or at a supercharging station up to 200 miles of range in about 15 minutes (approximately 60% of the battery capacity).
Another concern is the location and availability of charging stations. At the moment, ChargePoint has the world’s largest EV charging network available in up to 14 countries. They also have the most in the US, with 68,000 charging stations. Motorists can use ChargePoint’s very own smartphone app to locate the nearest charging station. Other apps like PlugShare provide information using a database of reported charging station locations. Tesla also provides locations of their supercharging stations from around the world, via their website.
What if you were in a hurry to go somewhere and cannot wait even 15 minutes to charge an EV? Another problem is that some older EV sizes limit the battery dimensions to support a maximum of only up to 40–60 kWh (Approximately 215 miles estimate) of battery capacity. A full charge at 215 miles will not even make it driving from LA to Las Vegas since a one way trip is over 270 miles. Other factors can also drain the battery, including powering the system’s electronics and plugged in devices. That means it will require an EV battery recharge somewhere close to Baker or Primm to get you to Vegas. Even worse, what if there was no charging station available at the route you are traveling on?
Wireless Charging
One way to allow for travel without needing to stop and recharge the battery, is a concept that the great Nikola Tesla himself developed for the purpose of providing free electricity to the world. This would be done without the use of wires or cables, but thru wireless transmission via electromagnetic induction. This requires a circuit on a device called a transmitter, that emits a signal using a varying magnetic field when an electric current is passed to it. Another circuit connected to a different device called a receiver, can pick up that signal. In this case, the signal can be in the form of energy to provide power.
Tesla showed it could be possible, but companies at that time did not like the idea since it could affect their business if this can provide free electricity. There were also critics with concerns that the wireless energy transfer is hazardous to humans, which could result in fatalities. The system was laid out many decades ago, now being implemented. The concerns have been addressed, and it is possible to transfer energy safely without frying anyone or destroying objects that get in its way.
The concept uses the principle of Resonant Inductive Coupling (RIC) or a form of wireless charging. This is already available on smartphones using the Qi wireless charging standard at a distance of less than 4 cm. With RIC, there is a wireless power transfer from a source to the EV battery but at a grander scale than Qi wireless charging. RIC can extend the distance used in wireless charging , greater than 4 cm. The question here is what type of source are you going to use to continuously charge the battery of an EV. To allow this will require investment in a new infrastructure to be able to support continuous EV wireless charging.
Redefining The Design And Purpose Of Roads And Highways
There is already a form of EV wireless charging which uses an inductive pad to transfer power to a battery. This is stationary however, and not meant for continuous charging for moving vehicles. It applies to EV that are parked, and the charging usually still takes a long time to complete. It borrows from that idea and applies it to the road and highway infrastructure for implementation. The inductive pads used will be more like charging plates that are buried beneath the surface of the roads and highways.
Wide stretches of roads and busy highways can have these charging plates installed. EV can charge up while in traffic, thus motorists do not have to worry about their car’s battery dying on the road. Imagine driving an EV in LA’s traffic jammed freeways. While EVs can still be efficient when idle, there is still a drain on the battery from other connected elements. The use of RIC deployed as charging plates underneath the freeway can help recharge EV battery.
In Tel-Aviv (Israel), Electreon is implementing a wireless electric road system for public transportation. According to their website, it offers:
“600 m long electric road, part of a 2 km route between train station and Tel Aviv University in Israel”
Electreon’s system uses copper coils under the asphalt to provide wireless energy transfer to a vehicle (e.g. bus) battery. The energy is transferred directly to provide power whether the bus is moving or not. Such use cases are being tested, and surely will provide plenty of data for other implementations to follow. Sweden has also used Electreon’s system to test charging an electric truck on a smart road. The results were successful, showing the potential for wireless charging technology.
Autonomous Mobility
Investing in a new type of infrastructure will be not only beneficial to EV, but also for self-driving cars. An integrated system that supports wireless charging and autonomous vehicle navigation can increase both safety and efficiency. Motorists will get to their destination faster with a lower probability of accidents. Safety and efficiency also increases as more cars on the road are EV.
The emergence of self-driving cars brings autonomous vehicles to the forefront. While they are not quite ready yet in 2021, they can complement wireless charging. Since self-driving car companies like Waymo plan to deploy robotaxis that don’t have human drivers, who is going to charge the cars? Full autonomy means the cars can do things without human intervention, and that includes charging. The best way for self-driving cars to accomplish this is through wireless charging.
These autonomous vehicles can charge when parked via a charging pad or on the road via the charging plate network. Some human intervention will still be required, but wireless charging can help considerably in reducing the maintenance required for robotaxis. Self-driving car companies can just invest in building the infrastructure since this will benefit them as well.
The Road Ahead
While it seems like the solution has been found, the only thing left to do is to build the system. It is not going to be that easy to transition because the problem is both a matter of government regulation policies and technical implementation of RIC with infrastructure projects. Governments have to commit to such changes and must prepare a budget. This gets tricky because figuring out the costs of a new never before implemented project can be a trial and error ordeal unlike a tried-and-tested system with an existing track record of success.
There are also drawbacks with inductive charging systems (nothing is perfect in this world). They tend to be inefficient at first, but the use of ultra thin coils, higher frequencies and optimized drive electronics are resolving the issues. The project will require deployment in controlled environments at first before it can be applied on a larger scale. It is not immediately necessary to install charging plates or cables under every street, road or highway. It would probably be most ideal on long stretches of roads and highways between charging stations.
Developers will also need to figure out sources of energy for RIC to deliver to EV. If this requires building more energy power plants, it won’t be good for the environment if the main source of energy comes from fossil fuels. Though that might be the main source initially, renewable sources are the best in the long term. Renewables may have a higher initial cost, but over time it pays for itself.
While wireless charging offers a truly contactless, transparent and faster way to charging a battery, EV will still need charging stations. What wireless charging offers is additional power to EV while they are on the road. Eventually, it will still require a charging station to fully charge a depleted EV battery.
Wireless charging with RIC can be provided for free by the government, or optional service that can be charged by an operator. That is also something that motorists must be aware of since wireless charging may be free only on public roads, but not on certain highways similar to the Toll Roads in California.
