Energy efficiency strategy in public electric transport – an implemented practical case of a trollleybus operator in Gdynia

Marta Woronowicz, Mikołaj Bartłomiejczyk (PKT GDYNIA)

THE CITY OF GDYNIA AND ITS PUBLIC TRANSPORT FACTS OVERVIEW • One of the three cities (together with Gdansk and Sopot) forming 1 million inhabitants Tricity agglomeration on the Baltic Sea coast in the north of Poland • 250.000 inhabitants • Length of public roads: ca. 400 km • Length of public transport routes: ca. 250 km • Motorization rate: 500 cars/ 1000 inhabitants • Transport modes market share: 56%/43% individual transport and public transport; only ca. 1% covered by cycling

GDYNIA: Very good quality of public transport services managed by Gdynia Public Transport Authority – 2013 UITP AWARD for excellent public transport organization • 4 municipal public transport operators ( 2 bus, 1 long distance bus and 1 trolleybus operator) and 3 private bus operators

77% of all Gdynia inhabitants live within a 5 min. walk from a bus/trolleybus stop - districts very well connected by PT

2014 EU REGIOSTARS AWARD for Gdynia trolleybus transport

GDYNIA TROLLEYBUS TRANSPORT FACTS • 12 day trolleybus lines • 93 trolleybuses (75 trolleys in daily operation) • 90 km of trolleybus traction • mileage of over 5 milion vehicle km a year • 385 employees, incl. 250 drivers • only 3 trolleybus cities in Poland (Gdynia, Lublin, Tychy) – 15 in the past

ELECTRIC vs DIESEL PT MARKET SHARE Trolleybus transport covers ca. 30% of

the whole public transport in Gdynia and neighbouring spa resort city Sopot (which

does not have poblic transport of iits own), mainly in central areas of both

cities.

Regular off traction courses by trolley battery hybrids - an innovation introduced by CIVITAS DYN@MO and ELIPTIC project Line 21 – a line extended by 2 km to a Gdynia landmark street Skwer Kościuszki - runs from May 2015 - DYN@MO Line 29 – a line extended by 4 km to Fikakowo densely populated housing estate - runs from December 2016-ELIPTIC Automatic lowering and raising of

current collectors due to special devices – docking stations placed on

the overhead grid

Origins of trolley battery hybrids in Gdynia • In 2008 - PKT‘s preparation to the fleet modernization co-financed

by EU funds Basic requirement – auxiliary drive allowing for autonomous operation in trolleybuses

Diesel drive

long distatance flexibility popular solution

Battery

promising technology zero emission easy maintenance („all electric“)

Decision makers

Battery drives currently used in Gdynia trolleys Ni-Cd battery capacity: 6-16 kWh range: 3-5 km no of vehicles: 41 Li-Ion battery capacity: 27 i 69 kWh range: ok.15 i 30 km no of vehicles: 3 + 3 LiFePO4 battery capacity: 40 kWh range: ok. 20 km no of vehicles: 1

Optimised braking energy recovery in the trolleybus network due to: ► implementation of a „dual power supply system” in the trolleybus grid ► installation of an energy storage supercapacitor on one of the substations ► ongoing procurement of the state-of-the art trolleybuses and gradually heading to 100% energy recuperation system equipped fleet

Energy efficiency strategy and solutions introduced

Optimised braking energy recovery in trolleybus network - use cases implemented

Trolleybus network is supplied by 10 traction substations Substations power: 13,6 MVA Network voltage: 600 V Substation in Sopot One of the substations (Wielkopolska) is equipped with braking energy supercapacitor – a storage device which captures and stores unused braking energy and saves ca. 12% of energy on this network section

Wielkopolska Substation - location of a supercapacitor energy bank This substation was predisposed for supercapacitor installation due to the hilly terrain of the power supply area – there are more occurrences of trolleybuses braking and giving recuperative energy back to the traction network. Supercapacitor ‘catches’ this energy and stores it for later use by other trolleybuses.

Results – recuperation of energy in 2017 in vehicles before and after SC installation

Supercapacitor technical data General data

Nominal input voltage 600 V DC

Max. input current 500 A

Max. input power 400 kW/20 s.

Data of SC bank

The range of voltage during operation

187 - 375 V

Max. current 1000 A

Capacitance 104.15 F

Energy capacitance 1.56 kWh

Number of modules 15: 5 branches x 3 modules

The range of voltage during operation

187 - 375 V

Optimised braking energy recovery in trolleybus network – use cases implemented

Power is centrally managed from 24 h Substations Control Centre placed in one of the substations (Redłowo)

Further optimization of the network introduced within ELIPTIC project: Smart grid in practice – implementation of bidirectional (dual) energy supply in two spots of Gdynia trolleybus network

Optimised braking energy recovery in trolleybus network

Billateral supply – increasing energy recuperation by optimizing energy balance in the network

An improved way of recuperated energy flow by balancing it and levelling off voltage drops - currently on 2 places of the network: bilateral supply links 2 pairs of substations: Sopot & Sopot I and Grabówek & Dworzec

Smart grid in practice – implementation of bidirectional energy supply in Gdynia trolleybus system - results

Unilateral supply Bilateral supply Sopot – Sopot I

Recovery effectiveness 2,5% 10% Transmission losses 4,6% 3,2%

Voltage drops <550 V 0,23% 0% Voltage drops <500 V 0,01% 0%

Dworzec - Grabówek Recovery effectiveness 19% 22%

Transmission losses 11,2% 7,1% Voltage drops <550 V 0,93% 0,01% Voltage drops <500 V 0,38% 0,09%

Smart grid in practice – implementation of bilateral energy supply in Gdynia trolleybus system

Improved spread of voltage

Sopot – Sopot I

Grabówek - Dworzec

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Main findings: • Bilateral supply system and supercaps on substations bring positive energy management and savings results • Reduction of energy consumption (2 – 5 % - dual power supply and ca. 12 % - supercapacitors) • Reduction of voltage drops – balancing the grid • Plans for extending these solutions to further spots on the network ● Gradual phase out of trolleys without energy recuperation systems and replacing them with state-of-the art. vehicles with best available battery cells (by the end of 2020 ca. 100% of vehicles with regenerative braking and 65% of trolley hybrids)

Traffic congestion – problem for stationary charging

Stationary charging: losing time for charging

Traffic congestion: → arrival delay → not enough time to charge in stationary charging

IMC: → better time usage → better flexiblity

Why In Motion Charging is the best solution for us?

Time is money! Delay arrival

→ not enought time to fully charge

IMC – no problem with delays!

IMC: way of reducing of battery capacitance

Why IMC?

ebus

IMC

Energy balance of In Motion Charging

Energy consumption

Charging power

Length of off-wire distance

Discharging efficiency

Time of ride in wire mode

Charging efficiency

How much infrastructure do we need?

Minimal covering rate by overhead wires

How much infrastructure do we need?

Energy consumption in short and all day period scale

Energy consumption in short scale: → minimall battery capacitance Energy consumption in long scale: → charging power

Distance covered

Vehicle equipment - facts

Bigger battery capacity → greater costs

Charging power: bigger power → faster charging → less infrastructure… …but charging power is limited by:

Infrastructruce (OHL, supply system): 50 – 500 kW Current collectors: 250 – 300 kW, but it could be better

Requirements for vehicles

Charging DC/DC converter – the main limitation (150 kW?)

Issue of charging power Charging power according max short time

energy consumption

Lower charging power – not enough time

to fully charge

Charging power according max all day

energy consumption

Lower charging power – deeper discharge

Requirements for vehicles

Tips for future:

Improvement of DC/DC power converter – now 150 kW,

future: ? Impovement of current collectors: now 600 A, future 1000 A ? Ideal for eBRT

Perspectives

PLANS FOR THE NEAR FUTURE -photovoltaic power plant on the roof of the depot (5000 m2, 500 kW, 5% of solar power in the traction network) -new Solaris fleet coming this year - 30 trolley battery hybrids (16 of 18M and 14 of 12M) -6 in-motion charged e-buses to be purchased in 2019 -exchange of Ni-Cd batteries in 21 trolleys - further line extensions already approved by Public Transport Authority

Tips for future: mini inverter station:

Tips for future: PV system + double supply – smart grid

Thank you for your attention!

Marta Woronowicz Mikołaj Bartłomiejczyk PKT Gdynia Emails: m.woronowicz@ pktgdynia.pl mikolaj.bartlomiejczyk@ pg.edu.pl