Induktive Energieübertragung für die Elektromobilität

 Wirkungsgrad in Abhängigkeit vom Abstand zwischen Primär- und Sekundärspule bei unterschiedlicher Permeabilität der Primärspule

Wirkungsgrad in Abhängigkeit vom Abstand zwischen Primär- und Sekundärspule bei unterschiedlicher Permeabilität der Primärspule

 

Zur beschleunigten Akzeptanz der Elektromobilität sind leistungsfähige Technologien zur Wiederaufladung elektrischer Energiespeicher (Akkumulatoren) notwendig. Hierbei sind Bedienungsfreundlichkeit, übertragbare Leistung, Wirkungsgrad, elektromagnetische Verträglichkeit und Gesundheitsrisiko wichtige Gesichtspunkte.

Magnetizable Concretes For Wireless Charging

GREEN MAGNETIZABLE COMPOSITE FOR WIRELESS ELECTRIC VEHICLE CHARGING

INTRODUCTION

Worldwide the adoption of electric vehicles (EVs) is gaining pace, bringing the charging infrastructure into focus. Sofar charge points for EVs have been plug-in devices, which work but are not very convenient. More recently fast charging plug-in devices have been introduced, which reduce the charging time, but still compare unfavourably with the refuelling experience with ICE
(internal combustion engine) cars. A far more convenient method is to charge the EV’s batteries with Wireless (inductive) Power Transfer. Charging without a cord means that EVs can charge their batteries anywhere anytime, not only when they are stationary but also when they are in motion. In the rapidly approaching world of Autonomous (selfdriving) Vehicles and Transport as a
Service (TaaS) wireless battery charging will become essential.

APPLICATIONS

Wireless charging of EVs is a rapidly evolving emerging technology. In a nutshell this is how it works: 

  1. An electric current from the grid is fed through the transmitter coil, which is on the ground or integrated in the pavement

  2. The current in the transmitter coil generates a magnetic field

  3. The magnetic field induces current in the receiving coil, which is tuned to the same frequency.

 
 Figure 1. Schematic of Wireless Charging System*  ** Courtesy of VOX MAGAZINE. www.vox.com

Figure 1. Schematic of Wireless Charging System*

** Courtesy of VOX MAGAZINE. www.vox.com

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 Figure 2. EV charge in motion

Figure 2. EV charge in motion

A handful of companies already offer commercial solutions for stationary wireless charging, while the vehicle is parked. Although this is a recent development, charge rates and efficiencies already rival plug-in fast chargers.

However, wireless charging holds its greatest promise in dynamic charging, while the vehicle is in motion.
In order to do wireless charging of EVs at high efficiency a focused magnetic field is required between transmitter and receiver, which necessitates a high permeability of the primary coil substrate.
The conventional approach is to do this with ceramic ferrite components. Due to the size of the primary coil (up to a square meter or more) and the fact that ferrite is brittle, this is an expensive and impractical solution to put into road pavements. Because of their costs Plastoferrites are not an option either. They also suffer from lower permeability and would not be dimensionally stable at high temperatures. All other soft magnetic materials (metal powder or amorphous metals) do not come into consideration due to high costs and limitations with respect to the size of the components.

MAGNETIC SUBSTRATE THAT BEHAVES LIKE THE ROAD

 
 Figure 4. Magment substrate with embedded coil

Figure 4. Magment substrate with embedded coil

 

A new material has been developed, which is a magnetizable composite called MAGMENT. This patented material has the mechanical properties of concrete, thus making it durable and compatible with materials currently used in road pavements. This overcomes one of the biggest hurdles for the adoption of pavement-based charging pads and dynamic charging systems. Magment makes the charging unit as robust as the pavement whilst also protecting the road’s structural performance.

 Figure 5. Transmitter-pickup coil distance for different electrical vehicles

Figure 5. Transmitter-pickup coil distance for different electrical vehicles

Magment’s magnetic properties are similar to ceramic ferrite. Although the permeability (μ) of MAGMENT is lower than of ceramic ferrite, tests have demonstrated that virtually the same power transfer efficiency can be achieved for the same geometry. However, with MAGMENT novel substrate shapes are feasible that boost the power transfer efficiency even further.

MAGMENT: ENVIRONMENTALLY FRIENDLY AND EASY TO USE

The magnetic properties of MAGMENT are generated by ferrite particles used as magnetic filler in a cement matrix. These ferrite particles are obtained from recycled material from the ferrite industry and from the rapidly growing mount of electronic waste.


Just like normal concrete MAGMENT can be supplied in pre-cast panels or cast in situ. There is no need to apply pressure or heat during the production process. This makes the application of MAGMENT fully compatible with conventional road construction practices.

 Figure 6. Wireless charging at the bus stop**  ** Courtesy of VOX MAGAZINE. www.vox.com

Figure 6. Wireless charging at the bus stop**

** Courtesy of VOX MAGAZINE. www.vox.com

 

VERSATILITY


Magment is equally suitable for both stationary and dynamic wireless charging. The load bearing properties of MAGMENT make it not only suitable for wireless charging of passenger cars, but also of busses, vans and lorries.

Due to its lower density (reduced weight) the Magment material is also attractive to use in the wireless power receiver on board of vehicles.

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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