ELECTRIFIED PUBLIC TRANSPORTATION POWERED BY INDUCTIVE CHARGING

The adoption of electric vehicles (EVs) is gaining pace worldwide, bringing the charging infrastructure into focus. Countries and municipalities are seeing the benefits of powering public transportation fleets with electricity since its infrastructure needs have become more feasible, achievable and affordable.

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Fig 1. Wireless charging bus

Fig 1. Wireless charging bus

To date, charging points for EVs have been plug-in solutions, which work but are not very convenient. The next and final step in the evolution of EV charging is wireless charging: there is a worldwide accepted standard, and it is perceived as an enabling technology for autonomous driving.

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THE SMALLER THE BATTERY...

Electrified public transportation such as electric BRT bus routes are currently only feasible with charging on route or many spare buses to allow recharging at end of route. Since the battery on electric buses represent up to 50% of the cost of the bus and its weight is inversely proportional to its passengers’ capacity, a reduction of battery capacity is desirable. However, as battery capacity is reduced, so is the charging power that the battery can safely use.

Dynamic wireless charging presents a futuristic but all-possible vision. With a 70% reduction on battery needs and energy transfer through coils embedded in magnetizable concrete roads, batteries will be charged with a round-the-clock energy flow.

 
Fig 2. brt vehicle

Fig 2. brt vehicle

This presents long term benefits not just to the environment, but also represents additional opportunities through emerging battery technology that can be transferred to other energy applications beyond moving people around in urban areas, such as the reutilization of batteries for a second life as part of a battery storage system.

 

CHARGE WHILE DRIVING

MAGMENT magnetizable concrete materials – either cement- or asphalt-based – is a patented technology displaying the mechanical properties of conventional concretes, thus making it fully compatible with materials currently used in road pavements.

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MAGMENT concretes are equally suitable for both stationary and dynamic, high-efficient wireless charging. The magnetic properties of MAGMENT concrete are due to embedded ferrite particles used as magnetic aggregates. These ferrite particles are obtained, but not limited to, recycled material from the ferrite industry and from the rapidly growing amount of electronic waste.

Fig 3. Magnetic field from transmitter coil to receiver coil enhanced by DM and FF Metamaterials

Fig 3. Magnetic field from transmitter coil to receiver coil enhanced by DM and FF Metamaterials

 

While the coil transmits energy through the MAGMENT concrete plates, the electromagnetic waves can be blocked or bended to enhance the inductive transmission efficiency and/or reach by layers from Diamagnetic (DM) and Field-Focusing (FF) metamaterials, below and on top of the magnetizable concrete, respectively.

BRT SYSTEMS WORLDWIDE

One of the challenges facing the adoption of electric vehicles is changing the perception that they can go a significant distance without needing to be recharged. The BRTData gathers information on Bus Rapid Transit – BRT and bus priority systems in cities around the world. Recent reports calculate that the average distance between stations in the cities in Table 1 is 0.693 Km.

 
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Table 1. Station spacing: Distance between each bus station

Table 1. Station spacing: Distance between each bus station

In an inductive charging system, a net power transfer rate of 120 kW in an average 60 seconds stop in the charging area is provided. If a bus energy consumption is 1.25 kWh/km, buses can ride 1.6 Km with the net power energy provision from the batteries. Table 1 presents the interval between charging stations, meaning the number of bus stop stations between each necessary charge.

In average, every 2.5 bus stop stations amongst these cities, a charging station would be required to fully charge the necessary battery capacity. EVs nowadays function with an approximate 300 kWh battery capacity, that’s a 5 times bigger, heavier and more expensive battery.

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According to the International Commission on Non-Ionizing Radiation Protection (ICNIRP 2010), magnetic field exposure for living objects should be below 27 µT.  The BRT Systems, specially with MAGMENT, comply and measure a very low value compared to EAS and metal detectors.

COST OF OWNERSHIP

The ideal solution for electrified public transportation for as long as possible can only be supplied by charging on the move. Dynamic inductive charging suits this requirement well, is technically feasible and economically viable thanks to cost reductions due to scale and mass production effects balancing out with road work and installation costs.

Recent studies on BRT buses in China estimate that within 1 Km, only 8% of its infrastructure cost represent USD 1.1 millions fully intended to build dynamic inductive charging segments. This cost plus the price of 5 wireless charging vehicles represents approximately the same amount as 5 regular plug-in EVs.

 
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