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SPECITICITY OF EXPLOITATION AND MAINTENANCE OF ELECTRIC BUSES IN CTC BELGRADE
Slobodan Mišanović*, project manager, PUC "City Transport Company" Belgrade, Serbia
Željko Milković, director of company, PUC "City Transport Company" Belgrade, Serbia Dušan Savković, tehnical director, PUC "City Transport Company" Belgrade, Serbia Pavle Krstić, head of maintenance depot ''Dorcol'', PUC "City Transport Company" Belgrade, Serbia Slobodan Stević, project manager, PUC "City Transport Company" Belgrade, Serbia Abstract:The introduction of electric buses into the public transport system is one of the strategic measures implemented by "City Transport Company" Belgrade in order to improve ecological and energy performance. The use of this type of drive has certain specificities and advantages in comparison to the diesel‐powered bus. This paper will analyze the specifics of operation and maintenance of buses on electric power on the basis of the two‐year experience in the line of EKO 1 in Belgrade. Keywords: E‐bus, exploitation, maintenance
INTRODUCTION
"City Transport Company" Belgrade, is the bearer of public transport in Belgrade and one of the largest public transport companies in South East Europe. Everyday in the operation are: 609 buses, 150 trams and 94 trolleybuses and 5 bus electrically powered. From 1 st September 2016, introduced a new line of EKO 1 where operate buses exclusively on electric power. In this way, Belgrade is included in the map of cities in Europe and the world that have begun using electric buses as a long‐term strategy for using this concept of drives, which will be the main alternative to diesel‐powered buses. The choice of the electric bus concept came after several years of activity in monitoring the development and application of these buses in many cities in Europe and the world, as well as successful cooperation with many bus manufacturers (Higer, BYD, Solaris, Siemns Rampini ...). Also, "City Transport Company" Belgrade has been active in many EU projects related to electric buses (ZeEUS, Hibryd user forum, Civitas, UITP bus coomitte ...). Specificity of using electrically powered buses can be seen in terms of: lines on which they work, vehicle concept, charging systems, maintenance, safety, exploitation indicators and environmental suitability.
LINE EKO 1 (VUKOV SPOMENIK – BELVIL)
The choice of a new line on which electric buses will operate will come after a detailed analysis of the fulfillment of the following criteria /1/ :
A central city line, so that the environmental impact of the "0" emission is maximized
High line attractiveness from the aspect of passenger requirements
Suitability of the line or terminal from the aspect of providing energy requirements for chargers
Line length, such that at the end of the journey there is a minimum of 20% of the available power in the supercapacitors
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Picture 1. – Route of line EKO 1
The mean length of the EKO 1 line is 8 km. The line is a flat configuration with a slight climb. On the line work 4 buses with an average interval of 20 minutes . The charging time at the terminals is 5‐10 minutes.
CHOICE CONCEPT E‐BUS AND SYSTEM FOR CHARGING
Taking into consideration all the available electric bus concepts and charging systems (slow, fast), which would be the best solution for the EKO 1 line, the team of "City Transport Company" Belgrade has chosen the concept of fast charging at terminals using a pantograph and an electric bus with supercapacitor as a system for storing electricity. The main advantages of these concepts are the following /1/
Opportune charge on Terminus via pantograph
• Acceptable charge time • Ability to connect to the trolleybus and tram contact network (DC), or public distribution electric grid
(AC) • E‐bus can work all day (especially important in summer when air conditioning is used as a large
consumer)
Storage using super capacitors:
• Principle: Electro static • High power • High efficiency 92‐98% • Temperature range: ‐40 +65 ˚C. • Short charge on terminal 5‐10 min • The flexibility of the rapid charging and discharging • Larger lifetime: min 10 years • Suitability of recycling
Picture 2. – Charging phase E‐bus to the terminus
Picture 3. – Position of super capacitors
’’Higer KLQ6’’ electric bus has the characteristic presentation in the following table 1 /2/ :
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Picture 4. – E‐bus Higer KLQ6
Picture 5. – indoor space
Table 1. – Technical Data E‐bus Manufacturer ................................................................................ Higher Type ..................................................................................... Electric KLQ6 Length / width / height …………………………. 12000/2550/3680 mm Curb weight..................................................................................12540 kg Passengers……………………………………………….…....……82+1 Mаx‐speed……………………………………………………….70 km / h Charging the terminus: 660 V DC or 380 V AC, 580 V DC output, 250 A Charging time at the terminus ... ............................................ 5‐8 minutes storage system Electricity ........................................................................ super capacitors Capacity ........................................................................................ 20 kWh Manufacturer ................................................................................... Aowei Type .................................................................... U‐CAP (37DT6‐03210) Traction motors ...................................................................................... 2 Manufacturer ............................................................................. Siemens Type ......................................................................................... 1PV5135 Power ........... 2x90 kW (peak opt.)………....... ... 2x67 kW (nom. Opt.) Torque ....................................................................................2x430 Nm Inverter ..................................................................................... DC / AC Manufacturer ..........................................................................Zhonglian Type ...................................................................... IEVD 130‐60ZO6GA Working range .............................................. 580 V DC / AC 500‐650V Convereter................................................................................ DC / DC Manufacturer ...........................................................................Zhonglian Type ........................................................................................ DY074C Working range ................................................................12‐24‐48 V DC Charging system: Pantograph ........................................................... Aowei 37DT6‐03212 Auxiliary systems: Air conditioning .................................................... Thermoking 81DT6 Pump control ......................................................... KVD HDZXB 1416 Compressor ....................................................................... IEM ER 230 UC‐Cooler ...................................................................... Aowei 37DT6 Traction control .......................................................... Siemens 10DT6 External display ................................................................. Novatronic
Charging the E‐bus is done at the start/end terminals: Vuk's monument and Belvil. There is a charger in the depot "Dorcol". At the location of the Vuk's monument, the charger is connected to the tramway contact network (DC) and at the location Belvil to the public distribution network (AC). A characteristic of the charger are presented in the following table 2.
Table 2. – Technical Data for charger station
Technical data
Input voltage AC 3x380 V (Belvil)
DC 660 V (Vukov spomenik)
Power 150 kW
Output voltage 400‐600 V DC
Maximum current 200‐250 А DC
The height from the ground 4.5‐4.6 m
MAINTENANCE, SAFETY MEASURES
Buses on electric drive as a relatively new concept of buses used in public transport are characterized by certain specifics when maintenance is concerned. Some of these specificities compared to diesel buses are:
‐ Simpler maintenance compared to the diesel bus ‐ Vital parts of the electrical components (inverters, converters, air copresor, pump, supercap ...)
modular type
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Picture 6. – traction inverters
Picture 7. – compressor, steering pump
‐ Lower maintenance costs (compared to a diesel bus about 3 times, E‐bus 3000 Euro/year, Diesel 9000 Euro/year)
‐ Diagnosis of failures or defects are identified in the instrument panel ‐ Short replacement time
In the following Table 3, shows the components and systems on the buses with a diesel‐powered and electric‐powered bus .
Table 3. – components and systems on the buses with a diesel‐powered and electric‐powered bus
It can be concluded that the electrically powered bus has a significantly smaller number of components and systems, which makes it more efficient and cheaper in terms of regular and corrective maintenance. In e‐buses, regular servicing is performed according to the defined check list at every 20 000 km, at the following vehicle positions as shown in table 4.
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Table 4. – Positions at which a regular service is performed every 20 000 km
Operation and maintenance of buses on a purely electrical drive means strict adherence to prescribed security measures and procedures. All components of the high voltage control system must be marked with a warning label and must comply with the electrical current protection according to the ECE R100 /3/
Picture 8. – Sticker high‐voltage locations
Picture 9. – inverter with a warning sticker
Drivers who operating E‐buses must have safety training in the exploitation and filling of E‐buses at the depot and terminus.
Passengers should not be in the E‐bus during filling at the terminal.
E‐buses must be fitted with a system for detection and automatic fire extinguishing and a switch for switching off the voltage from batteries or super capacitors containing a soldering fuse of 325 A.
Batteries or super capacitors are designed or provided with additional equipment ('shock absorbers') to withstand the impact directions in the event of a collision of E‐bus.
Training for maintenance workers with security procedures during preventive and corrective maintenance.
When replacing or repairing components and systems that are under high voltage, the input voltage must be switched off.
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EXPLOITATION INDICATORS ON THE LINE EKO 1
Analyzing the period of operation of buses on electric power from 01/09/2016 to 15/5/2018 we can conclude the following /4/:
Working hours per vehicle on day 16‐18 h
Avearage daily mileage per vehicle 190‐215 km
Exploitation speed: 14.8 km / h
Daily number of passengers transported per vehicle 900‐1200
Reliability of work on the line: 97.5%
The average electricity consumption on the EKO 1 line is about 1.1 kWh / km. (Depending on operating mode, number of passengers, traffic conditions, Impact of the system for heating and air conditioning of the vehicle, Transition period (outdoor temperatures 12 to 24 ˚C), Summer period (outdoor temperatures 25 to 38 ˚C),
Winter period (outdoor temperature ‐11 to 12 ˚C)
Consumption may vary:
In the spring / autumn period, 1.1 kWh/ km
direction "A" 0.88 ‐ 1.02 kWh / km direction "B" 1.15 ‐1.3 kWh/km
In the summer period max 1.5 kWh/km (air conditioning included, external temperature + 38 ˚C)
In the winter period max 2 kWh/km (heating included, at outdoor temperatures of ‐10 ˚C)
Loss of electricity in the charging phase (network, charger, pantograph, super capacitor) about 5%
E‐bus realized recovery of electricity in the braking phase of about 25‐30% compared to the energy consumed to drive.
Realized mileage per vehicle a given period is presented in table 5.
Table 5. – Mileage per vehicle
In the period 14.8‐6.10.2017, E‐buses were not in operation because of the works in Roswelt street.
ECOLOGICAL EFFECTS ON THE LINE EKO 1
One of the main reasons for introducing E.buseva the line EKO 1 are the environmental effects compared to diesel buses. This relates primarily to:
smaller level of noise, compared to a diesel bus lower by 13 d (A) /5/
"O" emission of harmful gases. Comparison of the emissions of harmful gases of one E.bus and diesel buses on the line ECO 1 for annual mileage 60 000 km, consumption 44 L/100 km, present in table 6.
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Table 6. – Comparison of the emissions of harmful gases of one E.bus and diesel buses on the line ECO 1
Pollutant E‐bus
Emissions of diesel buses (Euro 3)
Emissions of diesel buses (Euro 4)
Emissions of diesel buses (Euro 5‐EEV)
Emissions of diesel buses (Euro 6)
(kg/year) (kg/year) (kg/year) (kg/year) (kg/year)
CO 0 206 147 147 147
CxHy 0 64.7 45.2 24.3 12.75
NOx 0 490.4 342.1 195.7 39.2
PM 10 0 9.8 1.96 1.95 0.95
Better CO2 emissions, WtW (Well‐to‐Wheel) at E.bus compared to a diesel bus. It is very important here to calculate the standard emission factor (SEF) CO2 expressed in tonnes of CO2 emitted and produced MWh of electricity, which depends on the method of electricity generation (hydro power plants, thermal power plants, nuclear power, wind generators). Standard emission factor includes only the emission that occurs directly or indirectly due to electricity production within local authority while LCA (“life cycle assessment) emission takes under consideration all emissions of the supply chain (exploitation, transport, processing etc.) /6/.
This factor may have a different value. Figure 10 shows the values of this factor in the countries of Europe.
Picture 10. – Standard CO2 emission factors and LCA emission factors of the European countries
We see that countries such as Sweden, France, Austria, Lithuania have a very low value of this factor since electricity is produced from hydro power plants and nuclear plants. In contrast, countries such as Estonia, Poland, Greece, and Romania based on coal‐based electricity production have a very high emission factor. In Serbia, 70% of electricity is produced from coal and 30% from hydro potential, which gives LCA factor 774 t / MWh (774 g / kWh). On the example of the EKO 1 line for a diesel bus with a consumption of 44 L / 100km CO2 emissions, WtW (Well‐to‐Wheel) can be calculated as:
CO2 W t W = mco2 ∙ 1.2
m co2 =mf ∙ g c ∙ 44/12
m co2 ‐ mass of carbon dioxide generated by burning fuel (830 g/L) mf ‐ the mass of fuel burned (830 g/L) g c ‐ (0.85 kg C / kg fuel) ratio of the amount of carbon in the fuel 44 ‐ molar mass of carbon dioxide CO2 12 ‐ molar mass of carbon C
1.2 ‐ emission factor CO2 during the production and transport of diesel fuel
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Emissions, CO2 WtW (Well‐to‐Wheel) for an electric bus can be calculated:
CO2 W t W = LCA ∙ Ce‐bus ∙
1.05 LCA ‐ “life cycle assessment (774 g/kWh) Ce‐bus ‐ E.bus consumption ( kWh/km) 1,05 ‐ loss factor of electricity during charging
Table 7, shows the values of CO2 emissions for E.bus and diesel bus on the line EKO 1 in Belgrade.
Table 7. – CO2 emissions for E.bus and diesel bus on the line ECO 1 in Belgrade
Type of bus Consumption Emission of CO2 (g/km) E‐bus 1.10 (kWh/km) 893.9 (g/km) Diesel 0,44 (L/ Km) 1365 (g/km)
Conclusion is that the emission of CO2 in E.busa about 34.5% lower in comparison with the diesel bus. Similar results came in a survey carried in some European cities/5/, as presented in Figure 11. According to this study, CO2 emissions for diesel buses amounted to about 1350 g/km while E‐bus had a emissions of about 1050 g/km.
Picture 11. – CO2 emissions from buses of different propulsion systems
CONSLUSION Buses on electric drive are constantly rising in many cities and this trend will continue in the future as the main alternative to diesel buses drive. The main advantages of the electric bus concept are simpler and cheaper maintenance, high energy efficiency, zero emission of pollution and more favorable carbon dioxide emissions compared to conventional buses. The introduction of electric‐powered buses in Belgrade is a good example of practice that enables a realistic analysis of the effects of E‐bus operation to make a long‐term strategy of introducing this concept of drive in the public transport system of Belgrade.
REFERENCES
/1/ Mišanović S., Tica S.,Milković Ž.,Krstić P.,Milovanović B., Ecology and energy aspects of exploitation fully electrical buses on the new line in public transportation Belgarde, International Congress Motor Vehicles & Motors 2016, Kragujevac, 6‐7 October 2016, pp.33‐40, ISBN 978‐86‐6335‐037‐3
/2/ ‘’Higer’’ Electric bus – Tehnička dokumentacija, 2016. godina
/3/ Mišanović S.,Taranović D.,Pešić R., Specifičnosti pogona i bezbednosnih mera upotrebe autobusa na električni pogon, Stručni skup: Tehnički pregled vozila Republike Srpske 2016. Zbornik radova, pp.83‐100, ISBN 978‐99976‐673‐1‐1
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/4/ JKP GSP ''Beograd'': Izveštaj o eksploatacionim pokazateljima rada E‐busa HIGER A6L , 2018.godina
/5/ Urban buses: Alternative powertrains for Europe, A factbased analysis of the role of diesel hybrid, hydrogen fuel cell, trolley and electric powertrains, november 2012
/6/ Tomić,M.,Jovanović,Z.,Mišanović,S.,Živanović,Z.,Masončić,Z.,(2018) SOME ENERGETIC AND ECOLOGICAL ASPECTS OF DIFFERENT CITY BUS DRIVE SYSTEMS, Thermal Science, DOI REFERENCE:https//doi.org/10.2298/TSCI171027310T
