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Fast-charging

A remark: The terminology and abbreviations used are concisely summed up at the end of the article

In this article, we will try to resolve what technologies are suitable for fast-charging and we will discuss them from the economic perspective. We will skip segment of passenger cars, long-distance buses and lorries for which there is a focus on the long driving range between two charging stations without a stop. An excellent example for fast-charging is the segment of city buses with regular stops, revolutions at the terminal station and breaks of the drivers given by the public transport schedule. These breaks may be utilized for charging. Therefore, there is the option of the use of fast-charging and its economic advantages. But let’s start from the very beginning.

Technology

Thanks to the development in the area of batteries (energetic storages), there are alternatives to the operation of electric cars. Fast-charging is one of the options. Within a short period of time, you are able to charge the battery with high performance without any extreme heating of the battery system and thus decreasing its cyclic and calendar lifespan.

LTO Battery is currently the most suitable for fast charging (the best ones have the life span of 25 – 39 thousand cycles with 80% DOD). This is high-power technology (HP). Fast-charging can be also performed with currently most widespread technology of NMC or LFP batteries. These technologies are called high-energy (HE). A disadvantage is that there must be a huge capacity of battery in the car from which only minor part is used (e.g. 30 % from 400 kWh) so that it is not overheated so much and its lifespan is maintained. For NMC and LFP technologies we speak about 2 – 5 thousand cycles with 80% DOD which is at least five times lower lifespan than in case of LTO batteries.

City Buses

Fast-charging is currently the most widespread in the operation of city buses. This option has been rooted here thanks to the possibility of using the charging infrastructure and the need of only shorter driving ranges needed for a single charging (comparing to the option of depo charging with high-energy batteries). It is the principle of operational buses where traction batteries of the bus are charged with the high performance (200 – 800 kW) on their track, on the stops or only terminal stations. This principle is called opportunity-charging (note: It is actually in as fast-charging in different words). This principle enables the following:

•    Permanent operation of the car – 24/7 (it cannot be charged for hours),

•    Multiple increase of lifespan of the battery,

•    Effective recuperation,

•    Operation of HP battery with the temperature below zero without any additional heaters,

•    Less requirements for the charging infrastructure at depo since the cars are gradually charged on the way,

•    Decrease of the overall costs in the ownership of TCO and operational costs when all aspects are set up properly.

Of course, you may object that there are higher requirements for the charging infrastructure and reserved performance from the electricity network. The selection of the principle of functioning of electrical buses in the city traffic should be in the early phases accompanied by the analysis with careful calculations. Cities with the established tram and trolleybus traffic will have it easier. The reason behind is that nn the routes, there is an access to sufficient wattage from the network.

A practical example of calculation of the size of battery may be, for instance, a 40km route across the city and back. With the winter consumption of 1.6 kWh/km we may easily calculate 64 kWh for a distance route. Since we do not want to use the battery till it’s fully empty (meaning 100 % DOD or 0 % SOC), we increase the capacity to 80 kWh. With this capacity of the battery, a fast-charger will be sufficient for us only at one terminal station. With the performance of 560 kW, it is charged within 7 minutes and the bus may nicely start another route. Infrastructure at the route may vary. It can be easily counted that with additional fast-chargers on the route, with higher or smaller battery capacities, we may reach any values and optimize operation of the city transport.

There have been a lot of implementations and inspirations across Europe recently. For instance, MZK in the town Zielena Gora in Poland has declared 60 % electrified fleet.

Electro bus Ekova Electron 12

Partial Trolleybuses and Trams

Trolleybuses and trams are rather interesting vehicles. Why should they have a battery if they are all the time charged by the trolley? The main reason is cities that expand. Mainly for trolleybuses we may easily reach prolongation of lines to more distant parts of the cities, suburban areas as well as villages with the battery without the need to build trolleys. In case of trams, it may be in particular the impossibility to locate trolley to the monument protected areas or the insufficient performance of the network. Once the vehicle gets back under the trolley, battery starts charging again.

Another reason is effective recuperation of energy while breaking and thus decrease of the operational costs spent on the energy consumption. Earlier, super-capacities were utilized for recuperation; they are, however, pushed out by LTO batteries due to their sufficient performance and higher capacity.

It is a very good solution for cities with already established infrastructure. Partial trolleybuses may be seen in numerous Czech cities, such as Pardubice, Pilsen, Brno, Zlin, Teplice, Hradec Kralove, Ceske Budejovice, Prague, Marianske Lazne, Ostrava, Opava, Usti nad Labem.

Port Facilities (Vehicles and Travelling Cranes)

Another filed with the current electrification are the container tranship points. The company Kalmar is worth mentioning in this matter since it got an award by PEMA association for innovative and cutting-the-edge development in the industry. With its fast-charging system called Kalmar FastCharge™ it amazed the jury among 21 participating companies. In the option FastCharge™ Kalmar offers AGV (automated guided vehicles), Shuttle carriers and Straddle carriers. Charging of vehicles is performed during their downtimes. Comparing to diesel vehicles, electrification offers:

•    Decrease of emissions to zero, better atmosphere for drivers in the cabin,

•    Decrease of noise production, vibrations and heat,

•    Better control of the vehicle for drivers meaning the following

    o    smoother acceleration,

    o    higher performance,

•    removal of long downtimes for exchange of spare batteries.

Since charging can be conducted on the route of the vehicle as a natural part of the operational process, you gain benefit from faster turns and risen productivity whereas availability of the machine is up to 90 % of the time.

Comparing to diesel vehicles and cranes, apart from decreasing of local emissions operational costs also significantly decrease (in average by half)!

Port facilities – container handler

Port facilities – AGV

Other Fields

Experience has already shown that electrification has also economic advantages apart from improvement of local environment in the area of fast-charging. We may also mention other fields for which this way of electrification has undoubtedly economic meaning. These are, in particular, the areas where vehicles and machines move within a determined area and may be charged more often which utilizes downtimes (e.g. within 8 minutes once per 3 hours).

There is a big potential for the following fields:

•    Aviation facilities – in general GSE (Ground Support Equipment). Namely, for instance, plane shunters (pushback, taxibot, towbarless tractor), conveyor belts, escalators);

•    Construction machines – diggers, cranes;

•    Port ships – ferry, tugboats;

•    Warehouse facilities– e.g. AGV, forklifts.

Finally, there is a summary of advantages gained by fast-charging:

•    High performance via a small battery capacity (often without the use of air-conditioning),

•    Increase of lifespan of the battery (similar to the lifespan of the vehicle itself),

•    Decrease of total cost of ownership (TCO),

•    Increase of vehicle productivity – charging on the route, operation 24/7.

Pushback

Conclusion

In general, we may say that development of electrification across various fields is driven by high-energy batteries (lead batteries, NMC, LFP). For many vehicle operators, the main priority was as long driving range as possible. Moreover, with the first attempts, electrification of batteries was not developed sufficiently for fast-charging (LTO). Thanks to the technological progress, we may currently say that in the aforementioned areas, fast-charging batteries are advantageous both from the operational and the economical perspective. Therefore, substantial development is expected in this area.

It will be interesting to observe which another area will become the cutting-the-edge area and will be electrified via fast-charge technologies. There is no doubt we will have to wait for it for a long time.

Terminology:

High-energy, NMC (lithium-magnesium-cobalt), LFP (lithium-iron-phosphate)

High-power, LTO (lithium-titanate)

Forms of electrification:

    Fast-charging

    Opportunity charging

    Depot-charging

City buses, partial trolleybuses, facility port, aviation facilities, AGV (Automated guided vehicle), port ships

DOD depth of discharge

SOC state of charge

PEMA Port equipment manufacturers association

TCO total cost of ownership

Resources:

https://www.pema.org/kalmar-wins-the-2019-pema-innovation-award/

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