Engineering PhD School Leonardo Da Vinci Course in Land Vehicles and Transportation Systems. Research Activities Report Year

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1 Engineering PhD School Leonardo Da Vinci Course in Land Vehicles and Transportation Systems Research Activities Report Year PhD student: Giovanni Lutzemberger PhD subject: Hybrid propulsion systems and evaluation of the environmental impact Tutor: Prof. M. Ceraolo Research activities In the Research was mainly focused on these different topics: Collaboration to experimental tests on hybrid hydrogen propulsion systems 1. Design of the mechanical components of the electric motor installed on a small two seat aircraft, fed by an hydrogen propulsion system and a Li-ion battery (ENFICA Project). 2. Experimental tests of the hybrid hydrogen propulsion system (FC-Stack, battery, electric motor, electronic converters) of a small two seat aircraft (ENFICA Project). 3. Design of the hybrid hydrogen propulsion system of a small urban vehicle (Filiera H 2 Project). 4. Integration of the hybrid hydrogen propulsion system into a small urban vehicle (Filiera H 2 Project). 5. Experimental tests of the Fuel Cell System (Filiera H 2 Project). 6. Experimental tests of power-oriented lithium batteries and super-capacitors. 7. Participation to the ATA Formula EHI (Electric and Hybrid Italy) competition. Modelling and simulation activity 8. Sizing of the propulsion system of electric and hybrid buses through object oriented modelling (Industria PBI project). Analysis of the environmental impact 9. Collaboration to the evaluation of a methodology of global environmental impact of different vehicle technologies. Formula ATA competition 10. Thesis and training activity supervision: sizing and realisation of the electrical system of the Formula ATA car. Publications International conferences SAE-NA Workshop - Two wheel vehicles. Research and development perspective. Napoli, 4-5/12/2008 M. Ceraolo, G. Lutzemberger: Experiences on Hybrid and Hydrogen Two-wheel vehicle prototyping. SAE-NA - 9 th International Conference on Engines & Vehicles. Capri, 13-18/09/2009 M. Ceraolo, S. Barsali, G. Lutzemberger, M. Marracci: Comparison of SC and high-power batteries for use in hybrid vehicles. D. Poli, A. di Donato, G. Lutzemberger: Experiences in modeling and simulation of hydrogen fuel-cell based propulsion systems. SPEEDAM 2010, International Symposium on Power Electronics, Electrical Drives, Automation and Motion. Pisa, 14-16/6/2010 M. Ceraolo, G. Lutzemberger, N. Doveri: Experiences of realisation and test of a fuel-cell based vehicle. 1

2 IEEE VPPC 2010, Vehicle Power and Propulsion Conference. Lille, 1-3/9/2010 M. Ceraolo, G. Lutzemberger, M. Marracci: High power Lithium batteries usage in hybrid vehicles. T. Huria, G. Lutzemberger, G. Pede, G. Sanna: Systematic development of series-hybrid bus through modelling. National conferences BEST (Batteries & Electric Storage Technology Conference & Expo) - Conferenza sull immagazzinamento dell elettricità - 26/11/2009, Milano. M. Ceraolo, G. Lutzemberger, M. Marracci: Un confronto fra batterie al Litio di alta potenza e supercondensatori come sistemi di accumulo esclusivi di veicoli ibridi. Congresso ANAE 21 - Seminario Interattivo Azionamenti Elettrici. Bressanone, 22-23/3/2010 M. Ceraolo, M. Cellini, G. Lutzemberger, F. Papini, L. Sani: Il Progetto Filiera Idrogeno: sviluppo di un mini-van ibrido serie a celle a combustibile. M. Ceraolo, G. Lutzemberger, V. Musolino, E. Tironi: A comparison of supercapacitors and high-power lithium batteries. Italian Reviews ATA Ingegneria dell Autoveicolo, Vol. 65 (Novembre-Dicembre 2010) M. Ceraolo, G. Lutzemberger, F. Papini, L. Sani: Il progetto filiera idrogeno: sviluppo di un minivan ibrido-serie a celle a combustibile. Technical reports ENFICA Project WP 3: Energy system preliminary definition for transportation aircraft M. Ceraolo, L. Sani, L. Pollini, G. Lutzemberger, R. Mati: Proposed design options for the fuel cell propulsion. Technical report. WP 8: Propulsion system production for two-seat aircraft M. Ceraolo, L. Sani, L. Pollini, G. Lutzemberger, R. Mati: Realisation or procurement of motor and electronic inverter. Technical report. M. Ceraolo, L. Sani, L. Pollini, G. Lutzemberger, R. Mati: Procurement of the batteries and of the DC/DC converter. Technical report. Filiera H 2 Project WP 5: Linea idrogeno per sistemi a celle a combustibile L. Sani, G. Lutzemberger, A. di Donato: Dimensionamento preliminare del sistema di generazione elettrica a celle a combustibile. M. Ceraolo, G. Lutzemberger: Confronto tra un veicolo ibrido a idrogeno e un veicolo elettrico a batteria. P. Pelacchi, G. Lutzemberger: Relazione tecnica per l acquisto del banco a rulli. Industria 2015 PBI Project M. Ceraolo, G. Lutzemberger: Verifica del dimensionamento preliminare di un autobus ibrido a idrogeno. M. Ceraolo, G. Lutzemberger: Dimensionamento preliminare piattaforma autobus ibridi. M. Ceraolo, G. Lutzemberger: Dimensionamento degli accumulatori. Conferences and Meetings ENFICA Project, 2 nd Intermediate Technical Meeting, 14/1/2008, Torino. ENFICA Project, 5 th Technical Meeting, 3-4/3/2008, Torino. ENFICA Project, 3 rd Intermediate Technical Meeting, 12-14/5/2008, Loughborough. ENFICA Project, 6 th Technical Meeting, 3-4/7/2008, Loughborough. 2

3 ENFICA Project, 4 th Intermediate Technical Meeting, 16-17/12/2008, Pisa. ATA, Università di Pisa - Il motore diesel ad alte prestazioni: Ricerca e sviluppo tecnologico, 11/06/2009, Pisa. ATA - 3 rd International Conference: Hybrid, electric and fuel-cell propulsion systems, 17/06/2009, Torino. ATA - 11 th International Conference: Architectures for eco-vehicles: weight reduction, alternative fuels and propulsions, 24-25/09/2009, Firenze. ATA - Workshop: Collaborazione Università-Industria: Le eccellenze nascoste - L ambiente come opportunità di business, 8/10/2009, ENEA Centro Ricerche Casaccia (Roma). ATA, Università di Pisa - Il motore alternativo alimentato ad idrogeno, 20/11/2009, Pisa. GreenCityEnergy Forum Internazionale sulle nuove energie per lo sviluppo competitivo e sostenibile della città, 1-3/7/2010, Pisa. International Conference on Harmonics and Quality of Power (ICHQP) - Tutorial Harmonics in the Changing Power System, 26/09/2010, Bergamo. Gerard Ledwich (Chair in Power Engineering School of Engineering Systems Queensland University of Technology - Australia) Challenges facing energy delivery 22/10/2010, Pisa. LMS Delivering Transformative Solutions to the Global Automtive Industry 28/10/2010, Centro Ricerche Fiat, Orbassano (Torino). Attended courses English Course, C1 Level, Centro Linguistico Interdipartimentale (CLI). Scientific English course, Writing and Presenting Scientific Articles in English, A. Wallwork. Teaching activity Collaboration to the examination commission, for the learning course Sistemi Elettrici di Bordo. Some modest teaching activity about hybrid and electric vehicles, into the learning course Sistemi Elettrici di Bordo. 1. Design of the mechanical components of the electric motor installed on a small two seat aircraft, fed by an hydrogen propulsion system and a Li-ion battery (ENFICA Project) The main objective of the project is the integration of an hydrogen electrical propulsion system into a small two seat aircraft, instead of the internal combustion engine. The electrical drive train is a series-hybrid system: the energy sources are a Fuel Cell stack system and a Li-ion battery pack. The electric motor chosen for this application is a frameless motor. It means that motor case and motor shaft need to be defined separately, according with requirements such as lightness, integration into the layout of the aircraft, strength. Different solutions have been analyzed. In the final solution, reported in figures, the motor case is directly linked to the converter case. Both of them are realised in aluminium alloy. The converter case contains on its internal surfaces the electronic boards (inverter DC/AC and chopper DC/DC), for the control of the electric motor. This can be considered an excellent solution in terms of layout integration and cooling. The motor case is connected to the aircraft chassis through three constraints: one on top, and two on lateral sides. The shaft, realised in steel, is linked to the rotor through two thin covers, realised in steel too. Next step was related to the Finite Elements analysis for each component, to verify properties of stiffness and strength, and to the sizing of bearings, threads and splined profile. After discussion with the mechanical supplier, all drawings have been slightly modified to simplify manufacturing process. 3

4 Fig. 1: External view and section of the final assembly 2. Experimental tests of the hybrid hydrogen propulsion system (FC-Stack, battery, electric motor, electronic converters) of a small two seat aircraft (ENFICA Project) The electric propulsion system has been extensively tested through laboratory tests. The general scheme is the same of the Filiera H 2 Project, of the series-hybrid type, and reported in Fig. 3. In the first part, each subsystem has been tested separately by the others. After that, the electric machine fed by the Fuel Cell System and by Li-battery has been mechanically connected to an electric drive, working as braking load. During the tests, simulating take-off phase, flight at cruise speed and possible failures, all the parameters of each sub-system have been monitored. At the end of the tests, all the components have been installed on-board the plane. Fig. 2: Propulsion system during laboratory tests, and mounted on-board the plane 3. Design of the hybrid hydrogen propulsion system of a small urban vehicle (Filiera H 2 Project) The main objective of the activity is the design of the hybrid hydrogen propulsion system that will be installed on a small commercial urban vehicle, indentified in the Piaggio Porter. The electrical drive train is a series-hybrid system (Fig. 3): all the needed traction power is first converted into electricity, and the sum of energy between the two power sources, in this case the Fuel Cell System (FCS) and the lithium battery pack (RESS), is made in terms of electric quantities in an electric node, commonly a DC bus. 4

5 Fig. 3: General scheme of the drive-train According to the given performance requirements, the maximum constant speed at horizontal drive identifies the operating point to sizing the Primary Converter, because the FCS feeds the Electric Drive without using the Rechargeable Energy Storage System. The RESS has been sized considering the power surplus needed with respect to the one generated by the FCS during acceleration phases and drive in urban cycle. Fig. 4 shows the simulated main drive train power fluxes (for the meaning of the quantities, see Fig. 3), when the vehicle is performing the New European Drive Cycle (NEDC). From these plots it is possible to infer that hybridisation leads to Fuel Cell System downsizing, so the presence of the RESS reduces considerably the FCS cost, weight and size power (kw) RESS ED FCS time (s) Fig. 4: Main power fluxes of the drive-train, NEDC cycle Through a software realised in Matlab-Simulink environment, it is possible to simulate all the drive-train and finalise the sizing of the different components, reported in table below. Tab. 1: General sizing Fuel Cell System Rechargeable Energy Storage System Masses Number of cells 144 Number of cells 42 Frame [kg] 750 Nominal voltage [V] 83 Nominal voltage [V] 155 Electric Drive [kg] 122 Nominal current [A] 160 Nominal 31 Generation 151 capacitance [Ah] System [kg] Active area [cm²] 210 Nominal energy [kwh] 4,8 Load [kg] 550 Mass [kg] 60 Mass [kg] 44 Total [kg] Integration of the hybrid hydrogen propulsion system into a small urban vehicle (Filiera H 2 Project) The main requirement of the Project is the realisation of a vehicle flexible and usable as the conventional version. Indeed, in addition to the sizing of the different components, several layout 5

6 studies have been carried on. Finally, all the components have been disposed without influence passenger and luggage compartments of the standard Piaggio Porter. Furthermore, the weight distribution has been optimised to improve stability of the vehicle. In particular, the FCS is positioned under the driver seat: a co-design activity with the manufacturer has been defined, to dispose all the auxiliaries under the stack module, to have a compact and regular shape for easy installation on existing vehicle frame. The battery pack and electronic converters are disposed on the sides of the vehicle frame. H 2 cylinders are disposed with transversal orientation: they allow to store 1,1 kg of hydrogen at 35 MPa; the initial range specification cannot be fulfilled with this tank, but with the possible future use of 70 MPa (not yet implemented because of limitation of the Italian law) it will be by large overcome. Fig. 5 shows the first schematic layout supposed for the vehicle. Fig. 5: Schematic layout Since the first schematic proposal, starting from the CAD model of the Piaggio Porter, in collaboration with the company that works on the integration on-board, final disposition of all the components has been defined. To realise the effective placement of the drive train components, the company designed and built the required mechanical supports. Converters Electric machine Fuel Cell System H 2 tank Battery H 2 tank Fig. 6: Layout by EDI Progetti 6. Experimental tests of power-oriented lithium batteries and super-capacitors Experimental tests of high power batteries and super-capacitors are carried on into the DSEA laboratories, in which are located the following hardware components: Power unit, to control the charge current, PC connected through GPIB interface. Electronic load, to control the discharge current, PC connected through GPIB interface. Electric control panel, to control all the different phases inside the cycle, PC connected through LPT interface. DAQ electronic board, to acquire voltage and current, PC connected through GPIB interface. 6

7 HP multimeters, for the measure of voltage, current and temperature, PC connected trough GPIB interface. The devices under test are reported in figure below. Fig. 7: Devices under test: Li-ion power battery (29,6 V; 7,2 Ah) and super-capacitor (15 V, 20 F) First of all, the following stress types have been considered: a full charge cycling cycle, in which the battery or the supercapacitor is fully charged and fully discharged. This cycle gives information about the device capability, for measuring specific power and efficiencies, but it is not significant of actual hybrid vehicle battery stresses. Under this stress conditions, voltage, current and temperature of the two different devices have been measured. Some results are reported in Fig. 8. It s clearly shown that high specific power (about 10kW/kg) for super-capacitors can be guaranteed only for extremely short discharge times, in the order of fractions of second. Energy density (Wh/kg) Supercapacitor Li ion battery 360 s 36 s 3,6 s Power density (W/kg) Fig. 8: Specific energy vs specific power for the two devices After that, repeated partial charge cycle in which charge/discharge cycles are such that they can be repeated many times, without overcoming the battery over-temperature limits. This cycle implies shallow discharges and is more significant of actual battery operation onboard hybrid vehicles: it is constituted by constant-charge, constant-discharge and rest phases, with predefine constraints. For each current amplitude and durations, the battery temperature was measured. This way the maximum charge/discharge current compatible with limits of voltage and thermal conditions is evaluated. A sample result related to a current of 6C n is reported in Fig. 9. Although is clear from the in figure that the evolution of the refrigerating chamber temperature influences the battery case temperature, the difference becomes indeed constant after few charge-discharge cycles. The maximum case over-temperature registered, for charge-discharge current of 8C n and duration of 60 s, was about 7 C. 7

8 50 [A] 25 Current (A) [ C] [s] 1800 temperatures ( C) Battery case ambient [s] 1800 Fig. 9: Battery current and temperatures during repeated partial charge Next step of the activity is constituted by the reproduction of driving cycle simulating battery cycle: the discharge profile has been defined to accommodate the needs of a vehicle performing a NEDC cycle while using a battery that during accelerations is required to deliver currents of nearly six times the nominal capacitance. Instead, the charge profile has been defined to accommodate charging needs of the same vehicle under the same cycle, but current has been cut to the six times capacitance limit. This stress cycle allows to recover in the battery nearly all electric energy coming from the vehicle electric drive, while recovering vehicle kinetic energy. Furthermore, this cycle looks not particularly stressful for the battery: experimental results show that the temperature rises very slowly. 50 [A] Current (A) t (s) 1200 (f ile nedc.mat; x-v ar t) i temperatures ( C) Battery case t [s] (s) 1200 (f ile 6C sy mm mult mat; x v ar x) T batt Tamb 8 Room Fig. 10: Current profile vs time during experimental tests based on road cycle Finally, experimental evaluation of cycle life was carried on: in the cycle life tests the battery has been subjected to many (reduced-power) NEDC cycles, with periodic check of battery capacity. After each NEDC cycle, a no-operation phase of 600 s is imposed, to verify the open circuit voltage and update to the previous state the quantity of charge inside the device. After 136 NEDC cycles, corresponding to about 1400 km, a complete charge-discharge cycle is imposed, to verify the effective capacity of the device under stress. After about 1000 cycles, equivalent to km, the reduction in terms of capacity is about 1,8% of the initial measured value, nearly of 10,8 Ah. It means, linearly extrapolating data, that the end of life for the device under stress could be estimated to be around NEDC cycles or 10 5 km.

9 8. Sizing of the propulsion system of electric and hybrid buses through object-oriented modelling (Industria PBI Project) The main objective of the activity is the sizing of a complete line of series-hybrid and electric city buses for the Italian manufacturer Breda Menarini Bus (BMB), involved in the Project Industria As for the fuel-cell based Piaggio Porter of the Filiera H 2 Project, the series hybrid propulsion architecture, commonly chosen for hybridising buses, is adopted. The series-hybrid buses models have been defined through a more recent modelling technique, also known as object-oriented modelling: this is a relatively new modelling methodology based on object orientation and equations, characterised by: No need to define inputs and outputs at the model building stage. Ability of handling of large, complex multi-engineering models. Faster modelling by graphical model composition. The software employed in this activity is 3DS Dymola, that stands for Dynamic Modelling Laboratory: it allows model description by Modelica modelling language, which allows users to create their own models and model libraries, or modify the ready made model libraries to better match their simulation needs. All subsystems have been modelled weighting the accuracy and complexity for the purpose considered: Fig. 11 depicts the simulation scheme in Dymola, related to the hybrid versions. Fig. 11: Series-Hybrid bus model in Dymola After defining the models, it has been finalised the energy management strategy for the hybrid versions, to share the power needed from propulsion between the two different sources on-board: the primary converter works at slowly variable points, to maintain the ICE at maximum efficiency, while the RESS (Rechargeable Energy Storage System) manages the ripple component of the needed useful power, with the addition of extended charge or discharge phases when ICE ON-OFF strategy is considered. The ON-OFF strategy can be applied in two different ways: Programmed mode: at bus stops, or in ZEV mode, to avoid noise pollution and pollutant emissions. Non programmed mode: during traffic congestions, to avoid poor efficiency zones for the primary converter. According to the performance specification considered (max speed, drive with gradient, drive as Zero Emission Vehicle mode ), the final sizing is reported in Tab. 2. 9

10 Tab. 2: Sizing of the considered hybrid buses Bus Models Vivacity M Avancity L Avancity S Length 9 metres 12 metres 18 metres Weight (full load) 13,95 tonnes 17,96 tonnes 26,67 tonnes Weight (partial load) 11,3 tonnes 14,3 tonnes 21,1 tonnes Auxiliaries 6 kw 9 kw 12 kw ICE max power 48 kw 61 kw 84 kw ICE efficient power 36 kw 48 kw 69 kw RESS Energy 31,1 kwh 38,9 kwh 51,8 kwh ED power 2 x 60 kw 2 x 90 kw 4 x 60 kw After the sizing of the different components, an extended analysis related to the fuel consumption has been carried on: the difference between the conventional and the hybrid version is clearly put in evidence, with a reduction of about 24%. Furthermore, the effects of the ON-OFF strategy have been considered, during normal driving condition or in presence of traffic congestion. Tab. 3 summarises some of the results obtained. Tab. 3: Fuel consumption Bus 12 metres version ICE ON ON-OFF bus stops HEV (full load) 0,579 L/km 0,567 L/km HEV (full load) traffic congestion 0,634 L/km 0,624 L/km Conventional (full load) 0,759 L/km - Conventional (full load) - 0,839 L/km traffic congestion 10. Thesis and training activity supervision: sizing and realisation of the electrical system of the Formula SAE car The objective of the activity is the realisation of the electrical system of the Formula SAE car, visible in Fig. 12: in addition to the electrical loads of the motor (fan, ECU unit, starter, fuel pump...), in the first year the electrical system was equipped with two chopper DC/DC converter, to increase the voltage of the two voice coil actuators of the electric gearbox. More conventional solutions have been adopted, in the following years. The sizing of the components has been defined with reference to the endurance race, the most difficult test in Formula SAE competition. Fig. 12: Formula SAE car 10