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Is Wireless The Future For EV Charging?

| Thursday March 24th, 2011 | 2 Comments

From Plugless Power Website

Imagine a future where you drive your electric car to work, park, get out and walk away, and your car automatically starts recharging via a wireless connection. Such technology is being developed by a company called Evatran LLC, whose Plugless Power product should allow you to do just that.

Since Google has installed and is testing this product for its own electric vehicles (EVs), wireless recharging likely has a viable future as part of  the EV power-supply infrastructure. The system works by using inductive power transfer. This in itself is not new technology – Evatran explains it uses the 100 year old principle of electrical induction. In brief, it works like this:  In order to effect wireless charging, you have a transmitter coil and a receiving coil, separated by a distance. An electrical current passed through the transmitter coil produces a magnetic field that induces a voltage in the receiving coil. The voltage created in the receiving coil, in this application, recharges the car battery. Seems an elegant enough solution, but what are the benefits to the consumer?

First of all, the so called proximity charging system is convenient. After a special adapter is fitted to the car (which includes the receiving coil), the driver simply parks over the floor mounted ‘parking block’ (which houses the transmitter coil), and the system automatically starts charging. What you have is a simple hands-free set up which involves no cold, wet, dirty cables. Second, the system is universal, as the car-installed adapter works with any type of electric vehicle. It can adapt to vehicle-specific voltages, which eradicates the problem of non-standard connectors and plugs. Thirdly, the manufacturer claims it’s reliable, and since no electricity is flowing between the car and the floor (only a magnetic field), it’s safe. It’s also probably less prone to damage and vandalism than a cable based system.

Where the system has a downside however is in efficiency. Inductive power transfer suffers energy losses, which in this case would be dependent, in part, upon the distance between the car and the floor mounted parking block. Though Evatran claims that the system is 90% efficient, cable based power supplies that we see in use today, most likely have the efficiency advantage.

The user convenience, however,  is no doubt compelling from a business standpoint, as the mass adoption of EVs will likely depend in large measure on ensuring user interfaces are kept as simple as possible. But with power generation most often from dirty sources in the first place, coupled with the energy loss in transmission, is further energy loss in the last few inches to get to the car a justifiable cost for convenience? A stretched electricity grid probably doesn’t need further inefficiency, but this system nonetheless seems to be another innovation that might perhaps help sell the electric car to a wider audience.


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  • Dexter Goodwin

    It’s hard to believe an article could be written in this day and time that questions EV adoption based on “convenience” to charge, “dirty sources of electricity” and “stretched electric grid”.
    After our country being at war for 9 years and spending a trillion dollars in a country many feel was invaded due to it’s oil reserves; having experienced the pollution of our beautiful Gulf coast from the BP oil spill and now witnessing historic political upheaval in most of the Arab oil producing countries, shouldn’t we be asking what is in the best interest of our countries, long term, national security interest instead?
    Also, it is easier to put filters/scrubbers on the smoke stackes of a few hundred coal fired electric plants than it is to clean the exhaust from 250 registered vehicles. Even Duke Power has stated that if all the famlies in their market were to have an EV in their homes today and went to charge at the same time, it would only increase their power usage by 10%. That being said, shouldn’t we as a country be updating our dated grid system anyway? I much rather see us spending money on upgrading our electric infrastructure than spending money for our battle ships to guard the Suez Canal for oil exports to the US and other countries.

    • Phil Covington

      Yes, I believe we should be updating the infrastructure of the country and believe EV’s are important, should the country be serious about decreasing foreign oil dependence.

      Bit confused by the point you make in your first sentence as to the appropriateness of the article. But as to the particular elements you speak to: a) There is a culture of convenience, I think, in this country and people won’t adopt things that are not convenient b)Dirty sources of electricity do diminish the CO2 emissions benefits EV’s could bring, so why employ charging devices that waste energy? c) Agree grid capacity in total is less of a problem than the problems the clustering effect of EV adoption can put on local infrastructure. But, infrastructure would not support the country’s EV fleet if everyone started driving one tomorrow – without upgrades.