SiC-MOSFET Composite Boost Converter with22 kW/L Power Density for Electric Vehicle

ApplicationHyeokjin Kim, Hua Chen,

Dragan Maksimovic, Robert EricksonDepartment of Electrical, Computer and Energy Engineering

University of Colorado BoulderBoulder, Colorado, 80309

Zach Cole, Brandon Passmore,Kraig Olejniczak

Wolfspeed, A Cree companyFayetteville, AR, United States

AbstractA SiC-MOSFET composite boost converter for an elec-

tric vehicle power train application exhibits a volumetricpower density of 22 kW/L and gravimetric power densityof 20 kW/kg. The composite converter architecture, whichis composed of partial-power boost, buck, and dual activebridge modules, leads to a 60% reduction in CAFE averagelosses, to a 280% improvement in power density, andto a 76% reduction in magnetics volume compared tothe conventional Si-IGBT boost converter. These gainswere achieved with the help of optimization based on acomprehensive loss model including SiC-MOSFET switch-ing loss and magnetic losses based on the FEM methodsimulated in FEMM. Experimental results for the 22 kW/LSiC-MOSFET composite converter project 97.5% averageefficiency on US06 driving cycle and a CAFE averageefficiency of 97.8% .

I. IntroductionReduction in losses of the power conversion unit (PCU)

in electric vehicle (EV) or hybrid electric vehicle (HEV)powertrains translates directly into increased MPGe (Mile-per-Gallon equivalent) and downsizing of cooling capacity asso-ciated with thermal management. To increase peak efficiencyand achieve high CAFE (corporate average fuel economy) av-erage efficiency, the composite converter architecture has beenintroduced [1]. By utilization of pass-through modes of thecomposite converter and optimization by reallocating siliconsemi-conductor die and magnetics, the composite converterachieved 98.1% CAFE average efficiency. While the compositeconverter achieves CAFE average loss reduction by a factorof three relative to the conventional Si-IGBT boost converter[2], volume reduction in magnetics is challenging owing to thelow switching frequency of the optimum design. One approachassociated with this magnetic volume reduction without lossof efficiency involves wide band-gap devices such as SiC-MOSFET to utilize their superior switching performances [3].In the case of boost converter employed in EV powertrain ap-plication, even though the wide band-gap devices enables the

reduction in magnetics and improvement on peak efficiency,the low efficiency is still observed under the operating pointsrequiring high voltage conversion ratio owing to high magneticloss. Also large volume of capacitors are necessary to meetmaximum voltage requirement and peak RMS capacitor cur-rent. As a result, SiC-MOSFET conventional boost converterexhibits low average efficiencies on EPA standard drivingcycles, relative to the Si-MOSFET composite boost converter,and employs similar volume of capacitors, compared to theconventional Si-IGBT boost converter.

In this paper, 22 kW/L volumetric power density and 97.8%CAFE average efficiency are demonstrated in a SiC-MOSFETcomposite boost converter. The composite boost converterarchitecture achieves improvement in peak efficiency and highaverage efficiencies on EPA standard driving cycles such asUS06, UDDS, or HWFET compared to the conventional boostconverter so that the improvement on CAFE average efficiencyis enabled. Compared to the conventional Si-IGBT boostconverter whose power density is reported as 5.7 kW/L [2], theSiC-MOSFET composite converter achieves a 76% magneticvolume reduction, a 280% power density improvement, anda 60% CAFE average loss reduction. The composite boostconverter architecture exhibits the reduction in the capacitorRMS current rating and voltage rating which directly translatesinto a capacitor volume, compared to the conventional boostconverter. Also the magnetic volume reduction is demonstratedthrough the superior switching capability of SiC-MOSFETdevice. With the SiC-MOSFET switching device and com-posite boost converter, the volume reductions in capacitor andmagnetic are enabled and this achievement is explained inChapter II. To facilitate design optimization, the comprehen-sive loss model including switching loss and magnetic lossis developed and the loss model is explained in Chapter III.With the developed comprehensive loss model, the designof SiC-MOSFET composite boost converter and the designresult are explained in Chapter IV. Based on the design result,the laboratory prototype board of 22 kW/L volumetric powerdensity is fabricated and experimental results are demonstratedin chapter V.

II. Size reduction of passive components

The conventional boost converter employed in EV orHEV powertrain is comprised of capacitors, magnetics, semi-conductor devices, and peripheral circuits such as gate driveror sensor circuitries. The capacitors and magnetics occupysignificant part of boost converter module volume [2] andthe capacitor volume is proportional to the voltage rating andpeak magnitude of capacitor root-mean-square(RMS) current.In the case of conventional boost converter, the magnitudeof capacitor RMS current is proportional to the load powerand voltage conversion ratio of input to output. Based onthe assumption that the rated power can be delivered to theload over the all range of operating point, the magnitude ofcapacitor RMS current is maximized when voltage conversionratio is two while the rated power is delivered to the load [4].The RMS current rating and capacitance per volume versusvoltage rating of Metallized Polypropylene Film Capacitors(Film capacitor) is shown in Fig. 1. As the voltage rating ofcapacitor is higher, the RMS current capability and capacitanceper volume is degraded so that higher voltage rating necessi-tates larger volume of capacitor to meet the requirement ofRMS current rating or capacitance.

300 400 500 600 700 800 900Vrating [V]

0

1

2

3

4

5

6

7

810-4

RMS[A]/Vol[mm3]

C[uF]/Vol[mm3]

Fig. 1. Capacitor RMS current rating per volume and capacitance per volumeas function of voltage rating

The boost converter employed in EV or HEV powertrainis required to operate wide range of power and voltageconversion ratio, however, the rated power is delivered to theload at high motor speed region. Since the motor shaft power isthe function of torque and angular speed but maximum torqueis delivered only at low speed region, the rated power canbe delivered at high speed region. Based on the assumptionthat 250V of battery is employed and the maximum inverterDC bus voltage is 800V, the motor torque, load power andrequired DC bus voltage for the inverter as function of motorspeed resulted from the 30kW rated EV powertrain model [5]

is shown in Fig. 2. The required bus voltage is obtained fromfollowing equation to achieve minimum converter and inverterlosses.

0 2000 4000 6000 8000 10000RPM

0

10

20

30

40

50

60

70

80Torque [Nm]Power [kW]Vbus [10V]

Fig. 2. Motor torque, shaft power, and required inverter DC bus voltage asfunction of motor RPM based on 30kW EV powertrain model

Vbus,re f =

√α(V2

ds + V2qs) (1)

Vds and Vqs are the voltage of d and q stationary axis, andα is the number to achieve minimum converter and inverterlosses while avoid field weakening control. In this case, α istaken to be 3. At the low voltage conversion ratio of boostconverter, the maximum deliverable power is proportional tothe motor RPM. This load condition such as EV powertraincauses the capacitor RMS current magnitude of boost con-verter proportional to the voltage conversion ratio owing tolow peak power at low voltage conversion ratio. With thisload condition, the peak output capacitor RMS current andpeak output power of boost converter versus motor RPM at250 battery voltage is shown in Fig. 3. The peak RMS currentis observed at high voltage conversion ratio of battery to bus.Assuming that a conventional boost converter is designed tomeet the specifications shown in Fig. 2 and 3, the voltagerating of output capacitor must be higher than maximum DCbus voltage, 800V, and capacitor RMS current rating must behigher than peak RMS current, 64A.

With the composite boost converter architecture [1] shownin Fig. 4, the capacitor RMS current and voltage rating isreduced. The composite boost converter architecture consistsof three dissimilar converter modules, buck, boost, and dualactive bridge (DAB) operated as DC transformer (DCX). Sincethe output voltage of boost module employed in compositeboost converter is operated within 400V and the boost mod-ule processes partial system power, voltage rating and peakcapacitor RMS current are reduced. Based on the RMS currentcapability per volume as function of voltage rating shown

300 400 500 600 700 800Vbus [V]

0

10

20

30

40

50

60

70

80

Capacitor RMS current [A]Power [kW]

Fig. 3. Peak RMS current of output capacitor employed in boost converterand load power as function of output voltage based on 30kW EV powertrain

in Fig. 1, the volume reduction in output capacitor of boostmodule is 41%, relative to the output capacitor of conventionalboost converter. Even though the extra capacitors are necessaryfor DAB module input and output, the peak magnitude ofcapacitor RMS current of DAB converter is very small [6]owing to the nature of DAB operation under the voltageconversion ratio of input to output close to the transformerturns ratio. The resulting net capacitor volume of compositeboost converter is reduced by a factor of 1.4, compared to thenet capacitor volume of conventional boost converter.

BuckMbuck(D)

BoostMboost(D)

DCX1:NDCX

+

-VIN

VBUS

Fig. 4. Composite boost converter architecture [1]

However, the magnetic volume of the Si-MOSFET com-posite converter is essentially unchanged, compared to theconventional boost converter owing to the low switchingfrequency that occurs in the optimized design [5]. To reducemagnetic volume employed in half bridge converter, the SiC-MOSFET device can be employed with the high switchingfrequency without loss of efficiency owing to superior switch-

ing performance compared to the Si-MOSFET or Si-IGBTdevice. The efficiency comparison of SiC-MOSFET compos-ite, Si-MOSFET composite, SiC-MOSFET conventional, andSi-IGBT conventional boost converter at 250 Vin, 650 Vbus

versus power is shown in Fig. 5. Compared to the Si-IGBTconventional boost converter, the SiC-MOSFET conventionalboost converter achieves a reduction in losses over a widerange of operating points, particularly at low power and theresulting magnetic volume is reduced by 60%. Nonetheless,

0 0.2 0.4 0.6 0.8 1Power / Prated

90

91

92

93

94

95

96

97

98

99

100

Effi

cien

cy [%

]SiC-MOSFET Composite boostSi-MOSFET Composite boostSiC-MOSFET Conv. boostSi-IGBT Conv. boost

Fig. 5. Efficiency comparison of SiC-MOSFET composite, Si-MOSFETcomposite, SiC-MOSFET conventional, and Si-IGBT conventional boostconverter at 250 Vin, 650 Vbus versus power

the efficiency of the SiC-MOSFET conventional boost con-verter is inferior to the Si-MOSFET composite converter,owing to high magnetics losses at operating points requiringhigh voltage conversion ratio. In this paper, high efficiencyand high power density are demonstrated with SiC-MOSFETcomposite boost converter. Through the composite converterarchitecture and SiC-MOSFET switching device, capacitor andmagnetic volumes are reduced, and high average efficiencieson EPA standard driving cycles are achieved, compared to theconventional boost converter.

III. Comprehensive loss model

In this paper, the SiC-MOSFET composite boost converteris designed to demonstrate not only high power density, butalso high average efficiency on US06 driving cycle. To facil-itate converter module design optimization, a comprehensiveloss model is developed. The model includes semiconductorloss comprised of switching and conduction losses, and mag-netic loss including DC, AC copper winding losses and coreloss.

A. Semiconductor loss

Piecewise linear (PWL) function model [7] is employed forswitching loss calculation. The advantage of PWL switching

loss model is the use of parameters listed in manufacturer’sdatasheet and parameters of gate-driver circuit so that availableswitching devices can be evaluated. The developed PWLswitching loss model is based on following assumptions:• The switching loss is negligible when the switching

device is operated under zero-voltage switching (ZVS).• Parasitic circuit inductance and any ringing during switch-

ing transition are neglected.Based on the PWL switching loss model, instantaneous lossof each switching interval is calculated and average switchingloss over one switching period is estimated. Also, the conduc-tion loss of semiconductor can be expressed

Pconduction = RDS IRMS2 (2)

RDS is the on-state resistance of MOSFET and IRMS is theRMS current flowing through the MOSFET. To verify thesemiconductor loss model, a prototype board configured asboost converter is fabricated using Cree 900V/10mΩ SiC-MOSFET [8] packaged in HT-4000 module [9] which isshown in Fig. 6 . The comparison of measured efficiency

Fig. 6. Photo of Cree HT-4000 SiC-MOSFET full bridge package and USquarter coin

and switching loss model efficiency is shown in Fig. 7 and 8at operating point of 200Vin/209Vout and 300Vin/313Vout with200kHz of switching frequency. Under the voltage conversionratio close to unity, the switching loss dominates the converterloss, while magnetic loss is negligible and conduction loss canbe easily predicted. The developed loss model shows goodagreement with measured data over wide range of power andvoltage.

B. Magnetic loss model

The magnetic loss model consists of DC and AC copperwinding loss, and core loss. Core loss is calculated accordingto the iGSE method [10]. DC copper winding loss is pro-portional to the square of the DC winding current. For theAC winding copper loss, 2D FEM simulation tool, FEMM[11], is employed to estimate the loss resulted from skin,proximity, and fringing effect. The magnetic loss is measured

1 2 3 4 5 6 7 8 9 10Power [kW]

97.2

97.4

97.6

97.8

98

98.2

98.4

98.6

98.8

99

Effi

cien

cy [%

]

Measured efficiencyLoss model

Fig. 7. SiC-MOSFET boost module loss model (red dashed line) andmeasured efficiency (black dots) at 200Vin and 208Vout as function of power

2 4 6 8 10 12 14 16Power [kW]

97.6

97.8

98

98.2

98.4

98.6

98.8

99E

ffici

ency

[%]

Measured efficiencyLoss model

Fig. 8. SiC-MOSFET boost module loss model (red dashed line) andmeasured efficiency (black dots) 300Vin and 313Vout as function of power

with the prototype converter configured as a boost converterunder 240kHz of switching frequency and high voltage con-version ratio with light load. Under this operating condition,the semiconductor is operated under zero-voltage switchingso that the switching loss is negligible and magnetic lossdominates the converter loss. The comparison of measuredefficiency and loss model efficiency is shown in Fig. 9 at fourdifferent operating conditions, 100Vin/146Vout, 150Vin/220Vout,200Vin/294Vout, and 250Vin/368Vout. The magnetic loss modelshows good agreement with measured data.

0 0.5 1 1.5 2 2.5Power [kW]

90

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97

98

99

100E

ffici

ency

[%]

100Vin / 146Vout150Vin / 220Vout200Vin / 294Vout250Vin / 368Vout

Fig. 9. Magnetic loss model and measured efficiency of boost converter at100Vin/146Vout , 150Vin/220Vout , 200Vin/294Vout , 250Vin/368Vout as functionof power. Semiconductor loss is negligible due to ZVS and light load

IV. Design of SiC-MOSFET composite boost converter

Based on the comprehensive loss model discussed in sectionIII, the composite boost converter is designed to demonstratehigh volumetric and gravimetric power density, and high US06average efficiency as well. The specifications of input andoutput of boost converter are listed in Table I.

TABLE ISiC-MOSFET composite boost converter specification

Input voltage 200 - 300VDC bus voltage 800V maximum

With the 900V/10mΩ SiC-MOSFET module consisting oftwo half-bridge circuitries, an optimum parameter set includ-ing switching frequency and magnetics are optimized. Tofacilitate minimum average loss over US06 driving cycle, EVpowertrain simulation model is developed based on the NissanLEAF vehicle. The required motor power and bus voltage areextracted from the simulation result and the resulting densityplot of US06 driving cycle is shown in Fig. 10 on the normal-ized motor power versus required bus voltage plane. Higherfrequency counts of operating points are represented by darkershadings. Unlike the required bus voltage distributed over therange between boost converter input voltage and maximumbus voltage, the load power is distributed over the range ofpower less than 50% of system power. This tendency can beobserved on UDDS or HWFET driving cycles as well [5].Therefore, a boost converter with high efficiency at light loadis able to improve average efficiency on not only US06 driving,but also other EPA standard driving cycles. To optimize aboost converter over US06 driving cycle, all operating points

Fig. 10. US06 driving cycle density plot of operating points [5]

should be taken account. However, this brute force methodtakes prohibitively large amount of computational effort. Toreduce a computational effort without loss of optimizationresult accuracy, the weighted loss method [5] is employed.For the buck and boost modules, interleaving control schemeis employed to reduce magnetic volume and capacitor RMScurrent which directly translates into capacitor volume. Asa result, the capacitor volume is reduced by 17% and themagnetic volume is reduced by 25%, compared to the resultof non-interleaved design. The optimization results are listedin Table II.

TABLE IISiC-MOSFET composite converter magnetics design summary

Buck / Boost moduleSwitching frequency 240 kHzInductance 5.2 µH for Boost, 3.4 µH for BuckInductor core size and material Two ferrite, EILP 43

DCX moduleSwitching frequency 240 kHzTransformer turns ratio 4:6Transformer core size and material Ferrite, EILP 64

For capacitor design, single or multiple capacitors can beconfigured to meet the peak magnitude of RMS current. Tominimize the volume of composite boost converter moduleand also meet the peak capacitor RMS current, an exhaustivesearch script is developed on Matlab to find an optimumset of capacitors. The TDK’s Metallized Polypropylene Filmcapacitors are incorporated into the parameter library andresulting capacitors are listed in Table. III. The optimizeddesign of SiC-MOSFET composite boost converter achievesa peak power of 39kW with a predicted total volume of 1.8liters.

TABLE IIISiC-MOSFET composite converter capacitors design summary

Input 2x 6.8µF / 450VBoost output 3x 3.3µF / 630VDAB input 2x 5.0µF / 450VDAB output 1x 4.7µF / 630V

V. Experimental resultsBased on the converter optimization summarized in Section

IV, the SiC-MOSFET composite boost converter shown in Fig.11 has been fabricated and tested. The prototype board consistsof driver board, power board, SiC-MOSFET module, cold-plate, capacitors, and magnetics. The 3-dimensional explodedview of SiC-MOSFET composite boost converter is shownin Fig. 12. To reduce resistive conductor loss of PCB trace,power board utilizes heavy copper traces, while standardcopper traces are employed on driver board to utilize the smallmonolithic ICs.

Fig. 11. SiC-MOSFET composite boost converter prototype board. Top view(Left), bottom view with US $1 bank bill (Right)

Driver PCB

Power PCB

Cold-plate

Magnetics

Capacitors

SiC-MOSFET module

Fig. 12. 3D drawing of SiC-MOSFET composite boost converter composedof driver board, power board, cold-plate, capacitors, and magnetics

Fig. 13 shows the measured waveforms of DAB primaryand secondary, boost and buck switching node voltages, and

DAB primary and secondary, boost, and buck magnetic currentat 250Vin/650Vbus with 50W. Under this light load condi-tion, switches of DAB primary and secondary achieves ZVSthrough the resonant phenomenon between the output capac-itor of MOSFET and magnetizing inductance of transformerso that the switching loss of DAB is minimized. Also, thebuck module is operated under the pass-through mode. As aresult, the switching loss and magnetic loss of buck moduleare eliminated.

Vsw(dcx/pri)

Vsw(dcx/sec)

Itx(dcx/pri)

Itx(dcx/sec)

Vsw(boost)

IL(boost)

Vsw(buck)

IL(buck)

Fig. 13. DAB primary and secondary switching node voltages and transformerprimary and secondary currents, and boost and buck switching node voltagesand inductor currents at 250Vin/650Vbus with 50W

Also, the measured waveforms including interleaved schemeof boost module at 250Vin/650Vbus with 12kW is shown in Fig.14. Since the DAB is operated under the voltage conversionratio close to the transformer turns ratio, the AC copperwinding loss of magnetic is minimized over wide operatingrange. The operating condition and estimated losses of indi-vidual modules, and resulting efficiencies of composite boostconverter, and conventional Si-IGBT boost converter at theoperating points shown in Fig. 13 and 14 are listed in Table.IV. The comprehensive loss model shows good agreementwith measured data. Compared to the Si-IGBT conventionalboost converter [2], the improvement on efficiency at lightload is demonstrated with composite boost converter. Thishigh efficiency on light load leads substantial improvementon average efficiencies over EPA standard driving cycles.

The comparison of measured efficiency, the loss modelefficiency, and conventional SiC-MOSFET boost converter atthe operating point of 250Vin/650Vbus as function of poweris shown in Fig. 15. Compared to the conventional boost

Vsw(dcx/pri)

Vsw(dcx/sec)

Itx(dcx/pri)

Itx(dcx/sec)

Vsw(boost)

IL(boost)

Vsw(buck)

IL(buck)

Vsw(boost-1)

IL(boost-1)Vsw(boost-2)

IL(boost-2)

Fig. 14. DAB primary and secondary switching node voltages and transformerprimary and secondary currents, boost and buck switching node voltages andinductor currents, and boost module 1 and boost module 2 switching nodevoltages and inductor currents at 250Vin/650Vbus with 12kW

TABLE IVOperating conditions and estimated losses of individual module, and

resulting efficiency of composite boost converter and conventional boost

converter [2]

Operating point 250Vin/650Vbus 250Vin/650Vbus50 W 12 kW

Boost operating condition 250Vin/275Vout/21W 250Vin/275Vout/5kWBoost loss 11W 94WBuck operating condition 250Vin/250Vout/29W 250Vin/250Vout/7kWBuck loss 0W 5WDAB operating condition 250Vin/375Vout/29W 250Vin/375Vout/7kWDCX loss 18W 111W

Net loss 29W 210WEstimated efficiency 63.3% 98.2%Measured efficiency 66.2% 97.3%

Conv. boost op. 250Vin/650Vbus/50W 250Vin/650Vbus/12kWConv. boost loss 337W 463WConv. boost efficiency 12.9% 96.3%

converter, the composite boost converter achieves the im-provement on efficiency under light load and maintains highefficiency over wide range of power.

0 2 4 6 8 10 12Power [kW]

65

70

75

80

85

90

95

100

Effi

cien

cy [%

]

Comprehensive loss modelConventional Si-IGBT boostMeasured effciency

Fig. 15. Comprehensive loss model efficiency, measured efficiency of SiC-MOSFET composite boost converter and Si-IGBT conventional boost con-verter efficiency

The comparison of estimated average EPA standard driv-ing cycles efficiency and CAFE (Corporate Average FuelEconomy) average efficiency and quality factor, Q =

P∫|Pout |/|Ploss|, switching frequency, and magnetic volume

of conventional boost converter with Si-IGBT [2] or SiC-MOSFET, and composite boost converter with Si-MOSFET[5] or SiC-MOSFET are listed in Table. V. For higher qualityfactor, Q, either higher output power can be achieved withoutmodification of cooling capacity, or reduction in cooling ca-pacity associated with manufacturing cost can be enabled with-out degradation of output power. Compared to the conventionalSi-IGBT or SiC-MOSFET boost converter, composite boostconverter including Si-MOSFET or SiC-MOSFET exhibits theimprovement on average efficiencies on EPA standard drivingcycles. Also, the reduction in magnetic volume is demonstratedwith SiC-MOSFET composite boost converter.

VI. Conclusions

This paper is focused on the design of a high powerdensity and high average efficiency on US06 driving cycleSiC-MOSFET composite boost converter. The composite boostconverter achieves 22 kW/L volumetric power density, aswell as 97.5% average efficiency on US06 driving cycle and97.8% CAFE averaged efficiency as well. Relative to theconventional 5.7 kW/L Si-IGBT converter, magnetics volumeis reduced by 76%, power density is improved by 280%, andCAFE average loss is reduced by 60%. Also, CAFE averageloss reduction by a factor of 1.8 is achieved, compared tothe CAFE average loss of SiC-MOSFET conventional boost

TABLE VComparison of switching frequency, US06, CAFE average efficiency, converter quality factor (Q) and magnetic volume

Converter Si-IGBT Si-MOSFET SiC-MOSFET SiC-MOSFETConv. boost [2] Composite boost [1] Conv. boost Composite boost

Switching frequency 10 kHz 20 kHz 240 kHz 240 kHzUS06 average efficiency 93.3% 98.3% 96.8% 97.5%UDDS average efficiency 97.1% 98.2% 97.7% 98.0%

HWFET average efficiency 91.8% 98.0% 94.1% 97.6%CAFE average efficiency 94.7% 98.1% 96.1% 97.8%

CAFE Q factor 17.9 51.6 24.6 44.9Magnetic volume [mL] 343 372 136 82

converter. For the design optimization, a comprehensive lossmodel is developed. The complete comprehensive loss modelis experimentally verified through a prototype SiC-MOSFETboost module and shows good agreement with measure data.To optimize SiC-MOSFET composite boost on US06 drivingcycle, weighted loss method is employed and the resultingconverter leads to a predicted 39 kW peak power and volumeof 1.8 liters. Prototype board is fabricated and experimentalresults shows the improvement on efficiency over wide rangeof power and voltage, relative to the conventional Si-IGBT andSiC-MOSFET boost converter. Furthermore, the reduction inloss at light load is achieved so that improvement on averageefficiencies on EPA standard driving cycles is enabled. Theprototype SiC-MOSFET composite boost converter exhibits22 kW/L of volumetric power density and 20 kW/kg ofgravimetric power density.

Acknowledgement

The information, data, or work presented herein was fundedin part by the Office of Energy Efficiency and RenewableEnergy (EERE), U.S. Department of Energy, under AwardNumber DE-EE0006921.

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