Dynamic Wireless Charging of Electric Vehicles En Route
By: Leandros A. Maglaras, et all
Electric Vehicles [EVs] have the potential to reduce carbon emissions, local air pollution and the reliance on imported oil . The European commission aims to reduce road transport emissions by 70% by 2050 . Dynamic wireless charging of electric vehicles  could become a preferred method since it would enable power exchange between the vehicle and the grid while the vehicle is moving ubiquitously. Mobile energy disseminators (MED) are a new concept ,  that can facilitate EVs to extend their range in a typical urban scenario. Our proposed method exploits Inter-Vehicle (IVC) communications in order to eco-route electric vehicles taking advantage of the existence of MEDs. Combining modern communications between vehicles and state of the art technologies on energy transfer, vehicles can extend their travel time without the need for large batteries or extremely costly infrastructure.
Energy exchange can be facilitated by inductive power transfer (IPT) between vehicles and/or by installing a roadside infrastructure unit for wireless charging. However, given the vast expanse of road networks, it is impractical to have infrastructure units on every road segment due to prohibitive costs. IPT allows efficient and real-time energy exchange where vehicles can play an active role in the energy exchange procedure. On the other hand, the use of mobile nodes as relay nodes is common in vehicular ad hoc networks (VANETs). In a VANET mobile relay nodes can serve as carriers and disseminators of useful information. Influential spreaders, nodes that can disseminate the information to a large part of the network effectively, are an open issue in ad hoc networks. That is, nodes with predefined or repeating routes that can cover a wide range of a city region can do the work of roadside units while exploiting their mobility in order to provide higher quality-of-service (QoS).
Similar to information dissemination, special nodes, like buses (trucks), can act as energy sources to EVs that need charging, in order to increase travel time. These vehicles, from now on called mobile energy disseminators (MEDs), use electric plug in connection or IPT in order to refill starving EVs. Buses can play the role of MEDs since they follow predefined scheduled routes and their paths cover a major part of a city, while trucks could have the role of energy chargers mainly on highways. Buses can be fully charged when parked, before beginning their scheduled trip, and can be continuously charged along their journey by IPT stations installed at bus stops. Additional technology requirements that these vehicles may need in order to operate as energy sources, is an open issue, but it is rather more feasible in the near future, to have these features installed into large public vehicles than into passenger vehicles due to the additional cost and space requirements. Vehicles that book charging places on the same MED can create clusters and mobile charging stations will play the role of the clusterheads.
The vehicle requiring electric charge will approach the appropriate truck, after a preceding agreement, from the rear or the front end depending on the vehicle construction. The procedure will provide vehicle charging by an electric plug in connection (or process), or by electromagnetic induction with the use of Tesla coils. Immobilized charging can take place at predetermined road points (for example parking areas) in order to avoid traffic obstruction and in this case the method of the plug in electric connection is preferable. A synchronization of the vehicles’ movement will be executed via wireless communication mainly controlled by the truck/bus. From the analysis undertaken, it is apparent that it is preferable, for reasons of safety and better management of the system, that the vehicle needing charge should move ahead or behind the truck creating a cluster or a platoon. There will be a special joint magnetic arrangement concerning the vehicles, as well as a special interlocking arrangement in order for the two vehicles to approach and remain in contact, even while in motion, for as long as the charge transfer takes place. Charge transfer can be achieved with electric plug in connection, or by electromagnetic induction. During the latter transfer, the charge and consequently the power transfer will be accomplished with the use of two detached subsystems of magnetic coupling of high efficiency.
The electromagnetic subsystems will include magnetic coils secondary coils of a transformer, which will have loose coupling using air as the proper medium. This way of coupling (like Tesla coils) has proven to be more efficient than using ferromagnetic materials. The primary coil of the truck will be movable and able to be inserted in the bigger diameter coil of the vehicle, in order to improve the efficiency factor of the power transfer process and to minimize the leaking of magnetic flux. Moreover, the two subsystems will be specially shielded (Faraday cage) in order to protect occupants and bystander vehicles or pedestrians from electromagnetic radiation. The truck/bus will carry high capacity batteries and if needed, the appropriate electric system to convert voltage from DC to AC voltage of high frequency. It will also need to carry a conventional internal combustion engine in addition to the correct electric generator, to be used to produce electric energy in an emergency situation. By using cooperative mechanisms, based on dedicated short-range communication (DSRC) capabilities of vehicles or long term evolution (LTE) technology, vehicles search for the MEDs in range and arrange a charging appointment while moving.
The advantages of the proposed system are a) high efficiency factor (especially when the charge transfer is achieved via an electrical plug in connection) b) very short delay regarding the moving of the vehicles c) significant reduction of environmental pollution and d) coverage of special needs in exceptional climatic conditions or failure conditions. Making use of inductive charging MEDs can act as mobile charging stations, thus improving the overall energy consumption of a fleet of vehicles. This improvement comes with a cost in time and distance traveled, but starving vehicles otherwise would have to stop or make longer re-routes in order to find a stationary station and recharge their batteries. Combining modern communications between vehicles and state of the art technologies on energy transfer, vehicles can extend their travel time without the need for large batteries or extremely costly infrastructure.
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 Leandros A. Maglaras, Jianmin Jiang, Athanasios Maglaras, Frangiskos Topalis, “Mobile Energy Disseminators increase electrical vehicles range in a smart city”, Proceedings of the 5th IET Hybrid and Electric Vehicle Conference (HEVC 2014), London, 5-6 November 2014, DOI:10.1049/cp.2014.0947
 Maglaras, Leandros A., Frangiskos V. Topalis, and Athanasios L. Maglaras. “Cooperative approaches for dymanic wireless charging of Electric Vehicles in a smart city.” Energy Conference (ENERGYCON), 2014 IEEE International. IEEE, 2014.
Leandros Maglaras received the B.Sc. degree from Aristotle University of Thessaloniki, Greece in 1998, M.Sc. in Industrial Production and Management from University of Thessaly in 2004 and M.Sc. and PhD degrees in Electrical & Computer Engineering from University of Volos, in 2008 and 2014 respectively. He is currently a Lecturer in the School of Computer Science and Informatics at the De Montfort University, U.K. During 2014 he was a Research Fellow in the Department of Computer at the University of Surrey, U.K. He has participated in various research programs investigating vehicular and ICT technologies (reduction-project.eu), sustainable development (islepact.eu), cyber security (cockpitci.eu, fastpass-project.eu) and optimization and prediction of the dielectric behavior of air gaps (optithesi.webs.com). His research interests include wireless sensor networks and vehicular ad hoc networks. He is an author of more than 35 papers in scientific magazines and conferences and he is a Senior Member IEEE.
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