International Conference on Technical Sciences (ICST2019) 04 – 06 March 2019

Future of Common and Sustainable Transportation in Aiman NOUH Electrical & Electronic Engineering Department Faculty of Engineering / Omar Al-Mukhtar University Al-Bayda, Libya [email protected]

Abstract—The Transport sector in Libya heavily transport. Its sustainability is evident from its low levels depends on conventional vehicles, those that work with of atmospheric emissions compared to automotive, internal combustion engine. These vehicles burn the fuel maritime and air transport. It employs an electric traction and then inject a significant amount of pollutants into the with low energy consumption. It guarantees a air which negatively affect its quality. In an effort to comfortably and quickly moving large volumes of people promote public awareness, this paper firstly reviews and goods over short and long distances. Urban rail alternative fuel vehicles as a logic step towards sustainable, consumes of 0.12 kWh average per passenger-km, and efficient and environment friendly transportation. They realizes a factor of seven times more energy efficient than minimize fossil fuel dependency and reduce CO2 emissions a vehicle travel in cities [5]. We can say that the rail is that are responsible for the global warming. These already considered as the greenest form of mass transport. alternatives are the common transportation (railroads and bus networks) and the unconventional vehicles (battery High fuel economy and environmental friendly electric vehicle (BEV), fuel cell vehicle (FCV) and hybrid solutions, in the last decade, have seen a large growing electric vehicle (HEV)). Secondly, an implementation of leading to various configuration of vehicles. Electric battery-fuel cell vehicle system will be realized within vehicles and plug-in hybrid electric vehicles become now Matlab/Simulink software. Finally, the obtained results will a reality and they are available on marketing [6]. be exposed and discussed. This paper will firstly present the actual status of Keywords—global warming, transport sector in Libya, common transportation in Libya. Secondly, it will report railroad, metro, BEV, FCV, HEV the architectures of friendly environment vehicle. Finally, an example of battery-fuel cell electric vehicle will have 1. INTRODUCTION implemented and simulated using Matlab/Simulink Nowadays, the awareness towards economic and software. environmental issues related to fuel combustion in automobiles must be increased. Transportation is a 2. RAIL TRANSPORT IN LIBYA primary source of energy consumption and pollutant emissions worldwide [1]. It is one of the highest The construction of a national railway has been a goal of the Libyan government since the closure of the old consumers of fossil fuels and the largest contributor of greenhouse gas emissions [2]. The climate is beginning to railway in 1965. Since 1998, the Libyan government has been planning for a 3170 km. The network is to stretch transform, proven by the frequent storms, the increased of flooding in coastal areas, and droughts in arid sections of along the length of Libya's Mediterranean coast from to , extending from the western city of Ras the world due to the increasing of the average surface temperature. There are holes in the ozone layer of the Jdeir (at the Libyan Tunisian border) to Imsaid in the west (at the Libyan Egyptian border) with a total coastal length atmosphere and smog levels are ever increasing, leading to decreased air quality [3]. In response to these concerns of 2178 km. The network would extend southwards to a length of 992 km. Table 1. contains the network over environmental degradation, several government agencies, laboratories and the major automotive specifications [7]. manufacturers proposed a progressive increasing number The efficient completion of the Libyan rail network is of automobiles to be Zero Emission Vehicles (ZEVs) paramount and can be an important factor for economic [3,4]. Hence, Libya should adapt alternative sustainable growth and development of the country. It will link technologies in transportation sector leading to more production sites to regional and international markets, irrational use of resources. So, the consumption of oil will promote the national and cross-border integration of be decreasing which causes a rising of national regions, facilitate access to the labour market, education economical revenue and less carbon dioxide emissions in and health services, and alleviate the heavy traffic on the the air. roads. Public or common transportation, including bus services, is one of the important development priorities. Rail transport is the most environmental form of various ICTS24632019-EC5041 202

TABLE 1. LIBYAN RAILROADS SPECIFICATIONS Both, the railways and the Metro network, is Total length 3170 still until today suspended projects with a non-mentioned N°. of stations 75 percentage of realization due to several factors as the N°. of trains 244 inconvenient planning, bad management, corruption and N°. of vehicles 8654 the unawareness among local people and decision makers 250 km/h (coastal line) Speed in authority toward these projects. 160 km/h (southern line)

In addition to the national railway project, the 3. UNCONVENTIONAL VEHICLES government has also planned for the building of the In recent decades, the oil consumption of the Tripoli Metro. Its network was proposed to be consisting transportation sector has grown at a higher rate than any of three lines A (green), B (red), and C (blue) crossing the other sector. This increase has mainly come from new city from east to west and from north to south with good demands for personal-use vehicles powered by coverage of the inner parts of the city, with a total of conventional internal combustion engines (ICEs). Pure transportation length of 99.5 km, and a total of 72 electric or hybrid vehicles emerge as a solution for stations, the total length of the network including service problems associated with ICE vehicles [6]. HEV is sections will be 106 km. The Metro network is planned to defined as a vehicle that uses two or more on-board provide convenient connections to Tripoli International energy sources to power it. These sources of power could Airport and to the planned Railway station. They plan to be an ICE, fuel cells, ultracapacitors, battery, flywheel, build a system of park and ride facilities at suitable etc. Hybrid vehicles have proven to save energy and locations along the Metro lines. Fig. 1, shows the reduce pollution by combining an electric motor and an schematic representation of Tripoli Metro Network, while ICE in such a way that the most desirable characteristics Fig. 2, shows the layout of the Network [7,8]. of each can be utilized.

3.1 Battery Electric Vehicle An EV is a configuration that runs only on electrical input. There is no ICE on-board and this model uses a plug-in connection to charge the high-power battery [6]. A reasonably sized electric motor is used to provide propulsion power to the car. Fig. 3, shows the drivetrain of the pure electric vehicle.

Fig. 1. Schematic representation of Tripoli Metro network.

Fig. 3. Pure electric vehicle.

3.2 Fuel Cell Vehicle Fuel cell vehicles (FCV) are propelled by an electric motor. They are comprised of a high-power battery, an additional on board power generation unit the fuel cell as illustrated in Fig. 4. Fuel cells create electric power through a chemical process using hydrogen fuel and Fig. 2. Planned layout of Tripoli Metro network. oxygen from the air [9-17]. Hydrogen required for this kind of vehicle can be obtained from on-board high- At present, public transportation is carried out by a pressure hydrogen tanks or from hydrocarbon fuels limited capacity bus network. The Libyan Railroads through the process of electrolysis. Execution and Management Board (LREMB) should accelerate the planning of railway stations to connect cities, also a Metro network as a backbone of common transportation in the cities. This alternative can be considered as grid connected systems. So, the consumption of fuel and emissions will be reduced.

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4. IN-WHEEL BATTERY FUEL CELL VEHICLE For the wheel direct drive, especially with in-wheel motors, the Permanent Magnet Synchronous (PMS) motor is the reasonably, if not only possible solution, due to its relatively low mass which contribute to reduction of unsprang mass and to better drive comfort [1,4,18]. The Permanent Magnet Synchronous Machine block operates in either generator or motor mode. The mode of operation Fig. 4. Fuel cell vehicle. is dictated by the sign of the mechanical torque (positive 3.3 Hybrid Electric Vhicle for motor mode, negative for generator mode). The electrical and mechanical parts of the machine are each HEVs can be classified into three categories: (a) series represented by a second-order state-space model. The hybrid vehicles, (b) parallel hybrid vehicles, and (c) sinusoidal model assumes that the flux established by the Series-Parallel hybrid electric vehicle as shows in Fig. 5. permanent magnets in the stator is sinusoidal, which In a series hybrid vehicle, the engine drives a generator, implies that the electromotive forces are sinusoidal [19]. which in turn powers an electric motor. In a parallel hybrid vehicle, the engine and the electric motor are The PMSM equations are expressed in the rotor coupled to drive the vehicle. A series hybrid vehicle reference frame (qd frame). typically offers lower fuel consumption in a city driving 푑 1 푅 퐿푞 푖푑 = 푣푑 − 푖푑 + 푝휔푟푖푞  cycle by making the ICE consistently operate at the 푑푡 퐿푑 퐿푑 퐿푑 highest efficiency point during frequent stops/starts. A 푑 1 푅 퐿푑 휆푝휔푟 푖푞 = 푣푞 − 푖푞 − 푝휔푟푖푑 −  parallel hybrid vehicle can have lower fuel consumption 푑푡 퐿푞 퐿푞 퐿푞 퐿푞 in the highway driving cycle, in which the ICE is at the 푇푒 = 1.5푝[휆푖푞 + (퐿푑 − 퐿푞)푖푑푖푞]  highest efficient point while the vehicle is running at Where, L , L are d and q axis inductances, R is constant speed [6]. d q resistance of stator windings, id, iq are d and q axis currents, vd, vq are d and q axis voltages, ωr is angular velocity of rotor, λ is amplitude of the flux induced by the permanent magnets of the rotor in the stator phases, p is number of pole pairs, Te is Electromagnetic torque. The mechanical equations are:

푑 휔 = 1 (푇 − 푇 − 퐹휔 − 푇 )  푑푡 푟 퐽 푒 푓 푟 푚 푑휃 = 휔  푑푡 푟 Fig. 5. Hybrid electric vehicles Where, J is combined inertia of rotor and load, F is The use of this alternative in Libya is still negligible combined viscous friction of rotor and load, θ is rotor because that the degradation of air quality due to the ICE angular position, Tm is shaft mechanical torque, Tf is shaft vehicles has no significant impact among the Libyans. In static friction torque. addition, the price of fuels in an oil producer country is The FCV power train is of the series type and is usually lower. Also, the cost of this technology is higher propelled by two electric motors powered by a fuel cell than the cost of conventional vehicles. So, the public and a battery [20,21]. In the present study it is assumed awareness towards these technologies must be major that each of rear wheel is individually driven by three objective for Libyan authorities. phase PMSM. The PMSM is supplied by the association Table 2 shows a comparison between the ICE PEM fuel cell and battery through a DC/AC as shown in vehicles, common transportation and the unconventional Fig. 6. The Power of electrical motor is controlled by vehicles. splitting the power demand as a function of the available power of the battery and the fuel cell. This power is TABLE 2. COMPARISON BETWEEN CONVENTIONAL & ALTERNATIVE controlled by the DC/DC buck converter.

Conventional Common Unconventional ICEVs Train/Metro BEV/FCV/HEV Not Connect to Grid-Connected Connected Connected recharge batteries Air quality Very bad Good Good Emissions Nothing Low High Savings Fuel Little Little Dependant Dependency dependency dependency Technology Low High High Cost Consumer High Little Little Familiarization Health Risks High Little Little Fig. 6. Drive system mode. Urbanization Not Urban Urban Urban ICTS24632019-EC5041 204

 Another vehicle dynamics model is adopted,

5. ELECTRIC VEHICLE DYNAMICS  A turn is applied to the vehicle, The wheels have to produce a linear motion from a The overall model of simulated system is shown in Fig. 7. rotational motion. The traction forces can be calculated It consists of two in-wheel PMSMs that propel the car. from the torque of machine, while the wheel rotation is Each PMSM fed by the fuel cell and the battery. Their computed from the vehicle velocity [18]. models are implemented in the in-wheel motor blocks. 1 퐹푙푒푓푡 = 푇푒푚_푙푒푓푡 The energy management block has the objective to 푅푤ℎ푒푒푙 { 1  manage the energy transferred between sources and loads 휔푙푒푓푡 = 푉푣푒ℎ_푙푒푓푡 푅푤ℎ푒푒푙 when electric machines act as motors to move the vehicle,

where Rwheel is the wheel radius. and also when they operate like generators to charge the battery. This last block determines the reference signals Both traction forces (left & right) are coupled to for the electric motor drives, the fuel cell system and the produce the total traction force (Ftot). The chassis of the DC/DC converter in order to distribute accurately the vehicle can be modelled by a mechanical coupling device, power from the two electrical sources. which can be viewed as a series connection (common kinetic variable).

푉푣푒ℎ_푙푒푓푡 = 푉푣푒ℎ { 푉푣푒ℎ_푟𝑖푔ℎ푡 = 푉푣푒ℎ  퐹푡표푡 = 퐹푙푒푓푡 + 퐹푟𝑖푔ℎ푡

The vehicle velocity (Vveh) is obtained with the classical dynamics relationship that is coupling the traction and resistive forces (Ftot, Fres).

푀 푑 푉 = 퐹 − 퐹  푑푡 푣푒ℎ 푡표푡 푟푒푠 Fig. 7. Simulated system. where (M) is the mass of the vehicle. The chassis is an These signals are calculated using the position of the accumulation element with the velocity as state variable. accelerator, which is between (-100% and 100%), and the measured FCV speed. A negative accelerator position The environment of the vehicle is considered as a represents a positive brake position. The accelerator mechanical source. It yields a resistive force (Fres) to the position has the shape presented in Fig. 8. motion from the vehicle velocity. The dynamics of vehicle are implemented in in-wheel, 2 퐹푟푒푠 = 퐹푟표푙푙 + 퐶푎푒푟표푉푣푒ℎ    distribution, chassis and environment blocks. where (Froll) is the rolling force and (Caero) is the We also consider that the vehicle makes a turn of aerodynamic coefficient. interval (2.5s) starting from the instant (8 s). To do this, The coupling between the vehicle dynamics and the we differentiate wheel speeds during the turn (Fig. 9). electrical motorization is given by the relationship:

(퐽푤 + 퐽푚)휔̇푖 = 푇푒푚_𝑖 − 푇푟푒푠_𝑖 

(Tem_i, Tres_i) are the electromagnetic and resistant torques for the machine (i), (Jw, Jm) are respectively the wheel and motor inertia.

6. PERFORMING THE SIMULATION Fig. 8. Accelerator pedal position. To understand the dynamic behavior of global model of battery PEM fuel cell electric vehicle driven by in- wheel motors, the Matlab/Simulink software (R2012a) is used. Based on fuel cell and battery models that are embedded into the Sim Power Systems library of MATLAB as a controlled voltage source [22-29], we modified a demonstration of a fuel cell vehicle power train realized by Sim Power Systems and Sim Drive line [21]. Changes are made to the demonstration including:  Two in-wheel PMSMs are considered, Fig. 9. Instruction to vehicle at the turn. ICTS24632019-EC5041 205

At t = 6 s, the fuel cell power is equal to its reference power signal determined by the energy management 7. SIMULATION RESULTS AND DISCUSSION block, from this moment the battery is no more needed. It The variation of vehicle velocity with respect to can be seen that the battery power becomes zero as simulation time is given in Fig. 10. Accordance to pedal illustrated in Fig. 12. position, it is clearly seen that the car accelerates during At t = 12 s, the accelerator pedal is pushed to 85%. Instant three periods in which the supplying of PMSMs alters at which the battery helps the fuel cell by providing an between the two electrical sources. In the last period we extra power of 5 kW. impose a braking to the car. Referring to Fig. 8, Fig. 12, and Fig.16, when reaching The FCV velocity starts from 0 km/h to about 22.7 km/h instant t = 15 s, the accelerator pedal is fixed at -70% in through 15 s, and finally decreases to 10.8 km/h at 20 s. order to impose a regenerative braking. At which batteries This result is obtained by maintaining the accelerator SOC become lower. Therefore, they need to be recharged. pedal constant at (70%) for the first 4 s; and reduce it to The fuel cells share their power between the batteries and (25%) for the next 8 s by releasing the pedal; then the motors. It can be observed that the battery power increase it to 85% by pushing the pedal again for 3 s; and becomes negative. It means that the battery receives some finally, it sets to (-70%) for imposing gradually brake power from the fuel cell and recharges. The motors act as until the end of the simulation. generators driven by wheels of the vehicle. The kinetic energy of the FCV is transformed in electrical energy which is stored in the batteries.

Fig. 10. Vehicle velocity. It is clearly seen that the PMSMs speeds have the same Fig. 12. Battery power. behavior like the vehicle velocity. On the Fig. 11, we see a difference in the speed of motors. Where the speed of motor on the left side and the right side diverge as the right wheels slow down and the left wheels speed up to traverse the turn.

Fig. 13. Fuel cell power.

Fig. 11. Rotor speeds of PMSMs

At t = 0 s, the FCV is at idle position. When the driver pushes the accelerator pedal to 70%, the batteries provide power to motors waiting the fuel cells start. That is clearly seen in Fig. 12. and Fig. 13. Here, the battery power increases while its voltage decreases due to the large Fig. 14. Battery voltage. amount of current drawn by the vehicle as illustrated in Fig. 14. At t = 1.19 s, the fuel cell begins to provide insufficient power due to its large time constant. So, the battery continues to provide the electrical power to the motors. At t = 4 s, the accelerator pedal is released and maintained at 25%. The fuel cell cannot decrease its power instantaneously; therefore, the battery absorbs the fuel cell power in order to maintain the required torque as shown in Fig. 12, Fig. 13, Fig. 14, and Fig. 15. Fig. 15. Fuel cell voltage.

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[6] Mehrdad Ehsani, Yimin Gao, Sebastien E. Gay and Ali Emadi. Modern Electric, Hybrid Electric, and Fuel Cell Vehicles: Fundamentals, Theory, and Design. CRC Press LLC, 2005. [7] O. Alhusain, Gy. Engedy, A. Milady, L. Paulini, G. Soos, "Planning Tripoli Metro Network by the Use of Remote Sensing Imagery", International Archives of the Photogrammetry, Remote Sensing and Information Sciences, Australia, September 2012. [8] https://www.clydeco.com/insight/article/libyan-railway-projects [9] Abou El-Maaty Metwally Metwally Aly Adb El-Aal, ''Modelling Fig. 16. State-Of-Charge of battery and Simulation of a Photovoltaic Fuel Cell Hybrid System", Ph.D. Thesis, Faculty of Engineering, University of Kassel, April 15, 2005. 8. CONCLUSION [10] A. Kirubakaran, Shailendra Jain, R. K. 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