March 11, 2016

Is wireless electric vehicle charging worth the cost?

Yanbo Ge

Yanbo Ge

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Earlier this week, the U.S. Department of Energy highlighted recent collaborative efforts between two national labs and Hyundai to develop and demonstrate wireless EV charging technologies. This is just one of many ongoing efforts in the U.S. and around the world to develop this technology, which is expected to make EVs more convenient than they are today. For example, Clemson University’s International Center for Automotive Research (CU-ICAR) in collaboration with the International Transportation Innovation Center (ITIC) recently developed a wireless power transfer technology for parked electric vehicles (EVs) and launched their first test on Toyota vehicle models. The results showed a power transfer rate of 6.9 kilowatts with efficiency greater than 85%. This is just a first attempt to explore wireless charging. The team now has moved on to the testing of dynamic wireless charging, as in charging moving electric vehicles, a technology that has been previously demonstrated elsewhere.

Even though plug-in vehicles (PEVs) have a relatively short history in the market, wireless charging efforts have been underway for some time. Evatran began the development of Plugless – an inductive charging system for charging Electric Vehicles without plugging in since 2010 and began selling the Plugless L2 Wireless charging system (a 3.3kw charging system) to the public in 2014. Several major automakers in US have brought wireless systems to market within the recent couple of years: BMW, Chevrolet, Nissan, Cadillac, and more are considering this option. Recently more effort has been put into increasing the charging rate. UK is planning to start a test program on the dynamic wireless charging for Electric Vehicles that will last for 18 months – this will be a workaround of the limitation of EV range since the EVs will be charged while used on road.

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Wireless charging has several advantages over conventional plug-in charging method. The most important one is the convenience it brings for EV owners. Even though plugging in at home at the end of the travel day is simpler than going to a gas station to refuel, wireless charging not only removes steps inside the garages, it also enables charge while in use, which is difficult, though not impossible, for conductively charged EVs. The technology of wireless charging appears to be developing at a fairly rapid rate and the widespread use is expected by the optimisms. The report of “Wireless Charging Systems for Electric Vehicles” provided by Navigant Research indicated that by 2022 annual sales of wireless charging systems for EVs will surpass 300,000.

Despite of its convenience, wireless charging system has certain drawbacks like its higher cost and energy loss during transmission. Right now a Plugless L2 wireless charger is about $1500 (this depends on the model). Compared to the regular level 2 charger (about $500) it is a lot more expensive. Plugless reported that the energy efficiency of L2 is about 12% less than corded L2 30amp 240V charging systems. Assuming one drives 2015 Nissan Leaf (energy consumption rate 30 KWh/100mi) for 12000 miles per year, the electricity consumption will increase by 432 KWh each year. In other words, wireless EV charging for one EV would waste as much electricity each year as an average U.S. home consumes in two weeks. The accumulative energy loss of 300,000 wireless charging systems predicted by the Navigant Report would be pretty significant: 129,600,000 KWh. It remained unseen whether the wireless charging technology will represent the future of EV charging industry and whether it is beneficial for the EV adoptions. One more question that is remained to be answered is the distribution of the cost of the wireless charging facility and the electricity.


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