cost modeling of battery electric vehicle and hybrid electric vehicle based on major parts cost

7/28/2019 Cost Modeling of Battery Electric Vehicle and Hybrid Electric Vehicle based on Major Parts Cost

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11 OUTLINE OF ELECTRIC VEHICLERecently in the world, m any projects are developing

EV because environment on earth are recognized as themost important problem. Namely, the EV offers one ofthe most promising solutions for improving air qualitywhile reducing the reliance on fossil fuels to powervehicles. The use of EVs remains limited, however,because their driving performance has been too poor andcost has been too high. In order for an EV to he acceptedin society, the EV design should take advantage ofattributes which could only be incorporated into EVs,such as lower maintenance, and quieter and easier driving.With this broad definition in mind, electric vehicles mayinclude battery electric vehicles(BEV), hybrid electricvehicle(HEV) and fie1 cell electric vehicle(FCEV).In this paper, BEV and HEV are discussed. The mainsystem composition of the BEV and HEV are shownFig.1. As main components of the EV, a battery isinstalled within the bottom of the body, and a driving

(b ) hybrid clcctric vehicle(HEV)Fig. I.Main system composition of the EV

motor, an inverter, an automatic speed change gear and acompressor for an air-conditioner are installed within ahood(bonet).

111 COST ODELINGEconomic evalualion is a useful tool to determine

the relative merit of system proposals with differentcharacteristics. The results of the evaluation help the userto choose the alternative that.is most profitable for thebusiness. We used cost reduction sttucture that isconsisted of five major subsystem in case ofE V ~ [ 7 1 ~ [ 9 1 , [ ~ ~ 1 , [ ~ 3 1 .

1)battery2)driving motor (in case of HEV , motor and

control system)3)inverter and controller (in case ofH EV , engine

and transmission)4)body Game5)other related s ystem

Also, to alleviate the problem of price variation with time,we choose to express the various cost not in dollars orother official monetary units, but in an arbitary unit whichis the cost of one ampere-hour of nickel-metalhydridewi-MH) battery. These cost reduction structureare dealt with seperately as follows:A . Battery

It can be seen that the critical battery of EV is theNI-MH. Therefore, in this study, the Ni-MH batteries areselected for EV applications. Because the spec ific energyand specific power of electrochemical batteries aregenerally significantly lower than those of gasoline, alarge number of batteries are required to assure a desiredlevel of power performance. However, mounting a largenumber of batteries on the vehicle suffers from severaldisadvantages ; he reduction of interier and luggagespaces, the decrease in vehicle performances. Thus, thedevelopment of battery technology has been accelerated,in which a set of criteria including the specific energy,specific power, energy efficiency, charging rate, cycle life,operating environment, cost, safety and recycling m ust beconsidered.In this study, the relative cost of nickel-metal hydride(Ni-MH) battery is 1.7[pu]. The cost of the battery isbased on the energy capacity of battery.

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C. Inverter and Controller

where CB = total cost of battery [pu]EB =energy capacity of battery [Ah]UB =unit cost of battery per Ah [p d Ah ]

B. Driving Motor and Control SystemIn the past decades, DC variable-speed drive systems

were commonly used for industrial drive and EVapplications. Especially, the main component systems ofEV drivetrain are its electric motor. Motors generallyused for driving the EV are brush DC motor, ACinduction motor and Permanent Magnet SynchronousMotor(PMSM) etc. The brush DC motor has a largeelectromagnetic wave noise due to its composition ofbrushes and a commutator, the necessity of maintenanceof brush due to its structure depending on mechanicalcontacting, and the limits to speed. For these drawbacks,the brush DC motor has disadvantage in reducing the sizeand weight of the EV driving system.Also, the AC induction motor and the PMSM have nomechanically contacted parts, and therefore more suitablefor the EV driving system than the brush DC motor. Inthis paper, the author applied the PMSM into the EVdriving system. The cost of the motor is proportional tothe electric power requirement of the motor, Pb,[W],

Where CM = otal cost of motor [pu]P M=electric power requirement of motor[W]Un= nit cost of motor per W[puiW]CcC = cost of control system [pu] (in case of

HEV).The motor power is estimated from

where PL= load [VA]nr = motor efficiency ["h].Gene rally, the motor's efficiency is abo ut 90[%],assuming a middle motor.

The selection of power devices for BEV propulsionis generally based on the requirements of the voltagerating, current rating, switching frequency, power loss,and dynamic characteristic. A high-powerbipolar-junction transistorized inverter has the advantagesover its thyristorized counterpart in the aspects ofcommutation problems, switching frequency, andefficiency. Morever, it also has the advantages over itspower MOSFET-based counterpart in the aspects ofpower handling capabilities, conduction resistance, andcost. Although a new power device, namely the insulatedgate bipolar transistor (IGBT's), has been repeated to ha vethe advantages of both power bipolar-junction transistors(BIT's) and power MOSFET's, the BIT's are still the mostmature technology and are the power device mostcommonly used in motor drive applications.A s a main circuit element, an powrr-TR module is used.

On the other hand, the major function of thecontroller is to control the three-phase PWM inverter,hence the operation of the induction motor, in acc ordancewith the control strategy. With the adoption of recentlyavariable 16-bit embedded microcontroller. the hardw arecount and size of the controller cm be greatly reduced.Microprocessors are usually used to recognize themilestone of the development of microelectronics. In caseof BEV, the cost of the inverter and controller arecalculated by the eq.(4).

wh ere C C= total cost of inverter and controller [pu]C w =subtotal cost of inverter [pu]CCoN=subtotal cost of controller [pu].

The three-phase PWM inverter consists of powertransistor, recovery diode and base driving circuit, et al.The cost of the three-phase PWM inverters are based onthe power ratings according to the number of variousdevices.D. Engine an d Transmission

In case of HEV, the cost of the engine andtransmission are calculated by the eq.(5).

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where CET=total cost of engine and transmission [pu]C E N=subtotal cost of engine [pu]CTw=subtotal cost of transmission [pu].

E. Bo & FrameThe body frame of the vehicle consists of various

components. In this study, we assumed the cost o f a bodyframe is constant like conventional use. Therefore, in caseof BE V, the cost of body frame is about 67.21puI. Also, incase of HEV, the cost of body frame is ahout 63.6[pu].These costs are based on discussions with conventionalusers. Supp ort components were not included in the costestimate.F. Other Related System

Because EVs do not have an alternator, manyauxiliary systems must depend on EV batteries to supplythe necessary power. Air-conditioning, power steering,lamps and radios are just some of the accessories of anEV which have to rely on power converters to providepower from batteries. Other related system of vehicleconsists of conventional system like air-conditioner,steering system, braking system, lighting system, powertransfer system, wheel system, et al, and technical systemfor the EV like battery capacity meter, battery level meter,diagonosis system for electric circuits, et al. Therefore,we assumed the cost of the other related system shown ineq . (6). Especially, it assumes that the cost of aconventional system is constant.

CO =cost of braking system [pu]Cc- =cost of lighting system [pu]Ccr=cost of power transfer system [pu]Cc6 =c os t of wheel system [pu].

Also, the cost of the technical system, CT, is estimatedfrom

where CT I=cost of battery capacity meter [pu]CTI=cost of battery level meter [pu]CT 3 co st of various diagonosis system Lpu].m.ODAY'SOSTESTIMATION RESULTS

The estim ated cost using the basic cost assumptionsdescribld above and below, is given in Table I. Laborcosts for assembly are not included. The results arereferred to as "Today's costs", no credit is taken for futureprice reductions due to the benefits of mass production,technology improvements, or competitions.

T A B L E ICOST ESTIMATION Of EV IN CASE OF B EV AN D HE V

v.POTENTIAL COST REDUCTIO N ESTIMATIONwhere CR=total cost of other related system [pu]

Cc =subtotal cost of conventional system [pu]Cr =subtotal cost of technical system for EV bu].

The cost of the conventional system, Cc. is estimated fromcc=c c , +cc z +cc3 +CC? + c c j +CC6 (7)

where C cl =cost of air-conditioner [pu]Cc z=cost of steering system [pu]

We estimated the potential for cost reduction in EVas a function of time. The assumptions and results aresummarized in this section.A. Learning Curv e AnaLvsis

It assumed that the system cost is reduced byS[%](in case of HEV, 6[%]) for each doublin g in totalEVs produced (referred to as a 95[%] (in case of HEV,94[%]) learning curve). Consequently, this leads to the

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following generalized relationship[ 141.

End (IYear

c,=C,.p" (9)

EV per Year1 Tom1EVs Built I CurveFwIwBE V HEV BEY HEV BE V HE V

where C,= cost of total EV producedC I=cost of the first EVp=total EV producedn' =In 0.95 / In 2 (in case o f HE V, In 0.94 / In2)

therefore, in case of BEV, C,= CI.p-0.074 (10-1)in case of HEV, C,= C,.p".089 (10-2)

In order to determine the learning curve savings, weassumed a production schedule shown in Table 11. In caseof BEV, the learning curve analysis was applied to thedriving motor and inverter & controller (in case of HEV,the motor & control system and engine & transmission)as discussed below. Since today's body frame is fairlymature technology and its capability is not expected toimprove greatly in the future, these costs was not appliedto a learning cu rve reduction model. It is assumed that thecost of the battery, driving motor and inverter &controller (in case of HEV, the motor & control systemand engine & transmission), and other related systemcould be reduced by technology development, massproduction and competition.

TABLEIAN D LEARNINGCURVE ACTORASSUMED PRODUCTION SCHEDULES

The greater energy capability of battery is the larger costreduction of battery. Therefore, it assumed thattechnologies of battery can be improved to give 2[%] byyear 1 ,5[% ] by year 2, IO[%] by year 3, 15[%] by year 4.20[%] by year 5 , 2S[%] by year 6. 32[%] by year 7,41[%] by year 8 , 50[%] by year 9 and 60[%] by year IO .

It assumed that technologies of other related system ofBEV can he im proved to give 2[%] by year I , j[S/.] byyea r 2, 8["/,] by yea r 3, I2[% ] by yea r 4, 16[%] by yea r 5 ,20[%] by year 6. 25[% ] by year 7, 30[%] by yea r 8 ,35[%] by year 9 and 40[%] by year 10. Also, it.assumedthat technologies of other related system of HEV can beimproved to give 3[%] by year I , 7[%] by year 2, I [% ]by year 3, 17[%] by year 4. 23[%] by year 5 , 30[%] byyear 6. 38[%] by year 7,46[%] by year 8, 54[%] by year9 and 62[%] by year IO . Lastly, we assumed that the costsof driving motor and inverter & controller (in case ofHEV, the motor & control system and engine &transmission) could be reduced by 95[%] (in case of HEV,94[%]) for the first commercial system. We assumed thatthis can be achieved for the smaller systems with EV asthe market and technology develop. For years 2- 10, thelearning curve factors from Table 2 are applied to theyear one cost.B. Estimation of Cost by Depreciation

A dollar available today is worth more than the sam edollar available tomorrow, or next year, or ten years fromnow. If a cost of 100[$]/year for the next ten years isdiscounted at 2[%], it will have a present value of898.2[$] as seen below:The cost for the first year is lOO[S]. This amount ismultiplied by the discount factor of 0.980 to yield apresent value of 98.0[S].The discount facto r is calculated by eq.(I ):

Discount Factor = I /(I+(D / IO0 ))" (I)where D =discount rate in [%]

n =number of years.The discount factor is calculated for the remaining yearsin the above exam ple, and the. discounted, values aretotaled to obtain a net present value of 898.2[$] for thesequence of c ost during the ten years.In case of considering cost depreciation in this study, thetotal cost of system were more reduced by depreciation.We assumed that discoun t rate of cost is 2[x].C. Summary of Cost Reduction

Table 111summarized the result of the cost reduction

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analysis for the cases considered. For our BEVassumptions, the overall cost is reduced by 86.5[%] byyear 3,79.7[%] by year 5 an d 56.6[%] by year IO withoutcost by depreciation. In case of BEV, there are asignificant reduction in the battery, inverter & controllerdue to technical improvements in the design.

TABLE11ESTIMATEDCOSTFO REV WITH COSTBY DEPRECIATION

to demonstrate its benefits. Clearly the detailed costmodel of EV is more complicated than in our cost modelexamples. Also, cost reduction methods have beenapplied to common system decisions faced in industry.Investment guidelines justify the purchase of optimumsystems for new installations. The guidelines are generalin nature, and may be applied to any type or size system.The economic tools are also applicable for commercialapplications.

I I Estimated Cost [DUI I

, IYear 101 70.0 I 12.7 I 16.4 I 67.2 I 108.4 I 275

VI. CONCLUSIONThis paper ha s received the five subsystem (BEV :

battery, driving motor, inverter and controller, bodyframe and other related system, HEV : battery, motor &control system, engine & transmission, body frame andother related system) of EV and evaluated various relativecost of the main components systems by proposed criteria.Today's BEV system is dominated by the cost of otherrelated system, with a second major cost componentbeing the battery. Also, Today's HEV system isdominated by the cost of other related system, with asecond major cost component being the engine &transmission. Technology improvements and costreductions caused by mass productions and competitionare expected nver the next ten years. We project that areduction to a half of today's cost could be possible withaggressive market and technology development. Also,operating costs should be also decreased with automaticsystem using microprocessor.The cost model of this paper was applied to an actual EV

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[I31 S. M. Schocnung, t ai, "Small Technology and Cost RcductionEstimatcs", I E EE Trans. on Energy Conversion, vol. 9, no. 2.pp.231-237, 1994.

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cost modeling of battery electric vehicle and hybrid electric vehicle based on major parts cost

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