The Advantages of the Promising Electric Energy Sourcesover the Conventional Ones in Electric Vehicle Application

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Abstract

This article describes the issues which concern autonomous sources of electric energy, in particular, contemporary electric vehicle batteries. The article reports on the requirements for the energy accumulators and for the charging devices along with the analysis on the advantages and drawbacks of the existing electric vehicle batteries and dedicated charging devices produced by the leading manufacturers on the world market (the developments by Теsla and others). The recommendations on the application of the advanced technologies in the industry are given. The promising technologies are considered as those intending to prolong the vehicle drive without long charging.

The Advantages of the Promising Electric Energy Sources over the Conventional Ones in Electric Vehicle Application

The development history of the transporting vehicles and the alternative power supply systems indicates the necessity of employing the advanced electric energy sources of various types within them.

Currently, the most popular and influential players on the automotive market, namely Mercedes-Benz, BMW, Audi, Porsche, Volvo, Nissan, Hyundai and others, are widely engaged in electric vehicle production. One of the leaders who develops and produces electric cars and electric charging stations for them is Tesla Inc, while Nissan’s Leaf is the most frequently manufactured electric car model.

For end consumers, the significant issue is long-time failure-free performance of an electric power source without additional charging during its operation. Chemical sources of power supply are actually capable of ensuring only a short distance for one-charge electric car running [1].

Therefore, car manufacturers are actively working at developing new techniques which can provide longer distance running without additional charging for a long time [1] and those ones which are capable to reduce the charging time of the electric car battery.

Currently, it is feasible to charge the electric car by three ways:

1. Via residential building electrical networks with the standard voltage of 220 V as any other domestic appliances: it takes 8-12 hours to complete charging for Nissan Leaf and up to 30 hours for Tesla;
2. Via three-phase 380 V socket, a conventional outlet at filling stations and parking areas: complete charging within 4-8 hours;
3. Via fast-charger: powering up 80 % of the electric vehicle battery in the range from 30 min to 60 min.

Let us consider the capabilities of the contemporary charging solutions for electric vehicles (EV) and compare their speeds of charging against Tesla Model S, the contemporary offer in the greatest demand.

The conventional charging of Mobile Connector, a typical supplement to the EV, allows full battery in approximately 29 hours. Provided that an adapter, a connector and an enhanced AC network are applied, charging could be completed in 9 hours. The application of the devices of high capacity and special boosters permits charging in 4 – 5 hours. V1 and V2 Superchargers, the fast charging station for EVs, at the limited capacity of 120 kW rates could perform the charging within 1.5 hours. The other level of V3 Supercharger operating at the doubled capacity (250 kW) is capable of performing this job within from 50 – 60 minutes.

The latest V2G technology is designed as the bi-directional energy management system which allows, for instance, powering EV battery 100 % full in the morning hours and feeding back the fraction of the accumulated energy in the afternoon and in the evening when there are peak hours of energy use by both households and industries. The energy is not only consumed while charging, but also the part of it could be delivered back into the power grid acting as the balancing device in the electrical network. 

The latest models of Tesla electric cars are compatible with the above-mentioned technology. One can enable this bi-directional energy management system by choosing the dedicated function in the control system of Tesla electric car. Along with Tesla, Honda installs V2G charger and develops the dedicated charging infrastructure. Tens of V2Gs are being operated now worldwide. The USA has taken interest in these developments and V2G charging stations are soon expected to be built there. 

In the earlier publications, we proposed the solution of the wireless inductive charging which employs the electromagnetic induction at both EV rest and its motion. The researches and developers from Toshiba came to the similar solution in creating the system based on the energy transfer by means of the magnetic field and wireless charger relying on magnetic resonance, namely the resonance connection method between receiver and transmitter. The pilot system already exists and shows the efficiency of 95 %, it is capable of delivering 10-12 kW to the distance of 0.3 meter, which is sufficient for EV charging. This technology has passed the probation period by 2020 in Japan and served for electric busses in Tokyo airport. The resonant wireless charging enables simplifying concerning the accuracy of arrangement for the receiver and the transmitter antennas as compared to the ones operating via electromagnetic induction. 

Swiss ABB has launched the production of the most powerful and fast EV charger, called Terra High Power DC. Its maximal capacity is within the range of 350 – 450 kW, that is 3 times higher than the value for Tesla V1/V2 charging stations and nearly 1 – 1.5 times higher than that of V3 Superchargers.

Recently, the super powerful charger has been introduced by the developers from the subsidiary from Geely. Their Viridi E-mobility Technology (VREMT) permits accumulating the battery store for 300-km travel in 5 minutes. This charger has passed through the experiments and is ready for mass production. Its capacity is 600 kW, that is 150 kW higher than the analog by the Swedish-Swiss concern ABB. However, the amount of EVs compatible with this charger is not large: currently it is only Zeekr 001, which has obtained its new accumulators from CATL (their mass production is planned to be launched in 2023). In China, XPeng charging stations are feasible to charge the EV batteries as much as required for 400 – 450 km drive and perform it within 15 minutes while for GAC electric cars, the charging time is within 5 – 10 minutes to fill 80 % of the batteries. 

We cannot help mentioning the system introduced by Elon Musk several years ago. It was an automated battery-swapping for the electric car. Removing one battery and exchanging it into the fully charged one was planned to be carried out within 1.5 minutes, but this idea was not implemented on full-scale. However, the project was not abandoned but supported by Tesla Inc. They patented the mobile battery swapping rig for EVs, but this operation required the work of the technicians for changing out the battery packs and it took around 15 minutes. In brief, the rig was operated as given: the electric car was lifted to allow the technicians the access to the bottom of the car with the battery in it for performing the required operations of assisting the battery-swapping [2]. The point is that spending 15 minutes on changing out electric car battery is not reasonable since there are different power supply systems available. 

The advantages of the stations for electric car battery swapping are in their autonomous work and in the opportunity to operate at rather low capacities of the power supply lines. Moreover, it is quite possible to have their non-stationary or mobile versions with respect to the number of electric car requesting the battery swapping. 

The USA and Korean researchers call attention to the problem of battery ageing at fast charging and their work is being concentrated on determining the safe mode of charging time decrease. Their results are leading to the conclusion that superfast charging is quite possible without considerable damages on electric car batteries. Idaho National Laboratory claims that it is feasible to charge 80 % of the electric car battery in 10 – 20 minutes, but this technology is to be available as early as in 5 – 7 years, according to The Washington Post. Nowadays, the charging time to power up the battery up to 100 % of its capacity takes days while 80 % of the electric car battery could be charged in within 30 – 60 minutes with the fast charging mode.

Further, the electric energy is drastically cheaper than petrol, but even the former costs money. In many countries, the nets of charging stations grant their services for free, but there are no many of such stations. Filling the electric car battery full demands lots of electric energy to be consumed. There are also the other drawbacks of EV battery application and of the charging stations for them. Let us mention them as follows:

1. The number of the charging stations is small. 
2. The infrastructure for the electric car charger is being at the initial state of its development. 
3. The electric car travelling distance is limited within the range of 200 – 700 km (ranging from the cheapest models to the most expensive ones). An illustrative example is Tesla since even its first models permitted one-charge drive of 250 km distance while the latest one – up to 700 km. The latest frontiers in EVs field are ranged as follows: BMW – up to 360 km, Audi – up to 370 km, Hyundai – up to 300 km, Jaguar – up to 470 km, etc. 
4. The full charge for the battery is approximately within 10 hours (the special devices should be applied in this case). 
5. The heavier EV is (the load weight plus passengers), the more energy it consumes for driving.
6. There is no noticeable diversity among the models and brands of the electric cars and therefore no such a diversity among the electric energy sources and chargers for them. 

The car manufacturers are actively working on the development of new technologies for prolonging the car drive without long charging. One of such technologies is the application of supercapacitors in assembly instead of the batteries. Compared with the conventional capacitors, the supercapacitors show the advantage in terms of the volume, but are left behind with this parameter if compared with the contemporary batteries. However, the supercapacitor is advantageous over the battery which employs the chemical reaction since the former is more dependable, simpler and undergoes minor wearing. The supercapacitor can tolerate hundred thousand of charge-discharge cycles and its calculated service life is more than 15 – 20 years. Thus, the service life of the supercapacitors is tens of times longer than that of the electric car battery.

By joining several supercapacitors together, one can obtain the volume to equal that of the electric car battery, but the weight of this assembly will be 3 – 4 times higher than that of the battery, which is not acceptable for the contemporary means of transport. 

One of the latest concepts in EV development sphere is combining two different types of electric energy accumulators – graphene or other supercapacitor plus battery [3]. 

We have studied the contemporary experience of the Ukrainian and foreign EV manufacturers and producers of supercapacitors. The complex research has been performed and resulted in the solution to apply the supercapacitor for fast charging followed by the employment of the charge-discharge system incorporated into the inverter for withdrawing the charge to the EV battery while EV is driving in its travel. This engineering solution has been patented with the Ukrainian patent [4]. The electric vehicle with the proposed power supply system is to contain the battery, control system, on-board computer while its traction DC electric motors are to be connected to the supercapacitor pack via the balancing voltage invertors and are to be controlled by the EV control system. The application of the reported system allows the decrease in the electric energy losses, the longer electric car running, the reduction in the charging time for the electric power sources. We continue the developments in the reported direction. The research has been conducted and the document collection has been prepared for submitting the claim for the new patent. 

Authors:

Fedorets S. G., chief designer, Ukrainian Research and Scientific Institute of Machine-Building Technologies, Dniper, Ukraine 

Fedorov S. I., senior lecturer, Department of Electrical Engineering, Dnipro University of Technology, Dniper, Ukraine.

Bozhok I. N., chief engineer, Ukrainian Research and Scientific Institute of Machine-Building Technologies, Dniper, Ukraine

Mazan N. N., chief engineer, Ukrainian Research and Scientific Institute of Machine-Building Technologies, Dniper, Ukraine 

References:

1. Fedorets S.G., Fedorov S.I., Bozhok I.M., Mazan N.M. The Developments of Electric Power Supply Sources for Electric Cars  “Granite of science”/ Scientific and popular journal № 4 2023 (published 03.04.2023.)
2. Рогоза М.А., Бородай В.А., Нестерова Е.Ю., Кошеленко Е.В., Федоров С.И. “Скоростное обслуживание тяговых аккумуляторов современных транспортных средств. Проблемы использования информационных технологий в образовании, науке и промышленности”: XVII междунар.конф. (24 ноября 2022, г. Днепр): сб. науч. пр/ред.кол.: А.А.Азюковский и др.: М-во образования и науки Украины, Нац. Техн. Ун-т «Днепровская полтехника». Днепр: НТУ «ДП», 2022 № 7.С.57-58.
3. Слипченко М.И., Письменецкий В.А., Гуртовой М.Ю.Исследование режимов работы АКБ и суперконденсатора в системе энергообеспечения электромобиля. Восточно-Европейский журнал передовых технологий.2012, 4/8 (5), с. 31-35.