Automotive Fuel Cell Systems

Dr. Alexander Kabza

Zentrum für Sonnenenergie- und Wasserstoff-Forschung (ZSW) Baden-Württemberg

EST, December 10th, 2015

- 1 -

What we are talking about

- 2 -

Toyota

Audi

GM/Opel

Daimler

Honda

Nissan

VW

Hyundai

Source: Public available photos on homepage of different OEMs

FCS key requirements for FCEV application

(Some) key requirements for FCS (and components) in drivetrain application are challenging *: Electric efficiency: 60% for FCS (65% for stack) at 25% rated power

Corresponds to 814mV (based on LHV)! Q/DT = 1.45 kW/K Power density: Stack >2kW/kg and >2.5kW/liter, FCS >650W/kg and liter FCS transient response: 1 sec from 10 to 90% of rated power (most relevant

also for components, especially air compressor) Cold startup time: 30sec from -20°C and 5sec from +20°C ambient temp.

Durability: >5000 hours in Automotive Cycle with < 10% drop in rated power Stack Platinum content: < 0.1 mg/cm², 10g total stack or 0.125 g/kW

Not only the stack but All components shall fulfill this requirements!

- 3 -

* DOE Technical Targets for Automotive Application

Schematic FCS P&ID

- 4 -

Source: GM

Source: Daimler

P&ID example 1: ANL

Source: ANL FCS Analysis, DOE AMR 2014, FC017

- 5 -

P&ID example 2: DOE 2012 Source: DOE AMR 2012, FC018

- 6 -

Schematic FCS ESD

Compressor

Coolant pump

ARP

All other consumers

EMS

ETS

Battery PDU Stack

FCS 90 kW

7.5 kW

1.0 kW

1.0 kW

0.5 kW

80 kW

100 kW (peak)

20 kW

Gross = stack power Net = system power Battery size (kWh) is very depending on hybridization strategy!

- 7 -

FCS Fuel Cell System PDU Power Distribution Unit EMS Energy Management System ARP Anode Recirculation Pump ETS Electric Traction System (motor)

Two examples for important fuel cell system components

What are “important” components? Why are those components “important”?

- 8 -

Compressor and gas-to-gas humidifier

- 9 -

Why compressor and gas-to-gas humidifier as an example?

Big impact of cathode pressure and cathode humidity/dew point on stack performance and system efficiency.

- 10 -

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0 20 40 60 80 100

Cell

volta

ge [V

]

Stack load [%]

300 kPaabs275250225200175150125100

0.50

0.55

0.60

0.65

0.70

0.75

0.80

0.85

45 50 55 60 65 70 75 80

Cell

volta

ge [V

]

DPT.Si.C [°C]

24A 48A 72A 96A

0822_Investigation

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0 0.5 1 1.5

Cell

volta

ge [V

]Current density [A/cm2]

100 125 150175 200 225250 275 300

Important FCS component: Compressor for Air supply

Air supply in System: Turbo charger or screw compressor Objective: Compress ambient air to feed requested Air mass flow into the stack

- 11 -

Source: Lecture Mohrdieck 2011

Dynamic (Idle to 90% full load): 0.8 sec

Gas compression

Gas compression means to increase the pressure of a specific amount of gas from a lower pressure level p1 to a higher pressure level p2, where p2 > p1 and the pressure ratio Π = p2/p1 > 1.0. Gas compression requires a specific amount of energy or power. Gas compression always increases the (gas) temperature from the lower temperature T1 to the higher temperature T2, where T2 > T1.

p

V

p2

p1

V2 V1

2

1

- 12 -

Theory of gas compression (and expansion)

Any adiabatic reversible process is an isentropic process. Isentropic means equal entropy. For an isentropic change of state there are the following equations: For air cp and cv are between 0 and 200°C nearly independent of temperature! The constant values for air are:

κκκ 1

2

1

1

1

2

2

1

−−

=

=

pp

VV

TT

κ

=

2

1

1

2

VV

pp

v

p

cc

=κ

KJ/kg45.1005, =mpc

KJ/kg39.718,, =−= airmpmv Rcc 40.1==v

p

cc

κ

285.01=

−κ

κ

k is the heat capacity ratio or isentropic expansion factor

- 13 -

Isentropic versus polytropic technical work for gas compression

The technical energy/work for gas compression is given by:

𝑤𝑤𝑡𝑡,12 = 𝑐𝑐𝑝𝑝,𝑚𝑚 ∙ 𝑇𝑇2 − 𝑇𝑇1 = 𝑐𝑐𝑝𝑝,𝑚𝑚𝑇𝑇1 ∙ Π𝜅𝜅−1𝜅𝜅 − 1

Isentropic: All supplied work is added to the internal energy of the gas, resulting in increases of temperature and pressure. Polytropic: Rise in temperature in the gas as well as some loss of energy (heat) to the compressor's components. Increased temperature is above adiabatic! (Still fully isolated system). Isentropic compression efficiency is then the ratio of adiabatic temperature rise versus polytropic temperature rise:

isentroppolytrop TT ,2,2 >

1polytropic2,

1isentropic2,isentrop TT

TT−

−=η

- 14 -

0

19

36

65

88

109

127

143

0

20

40

60

80

100

120

140

160

1.0 1.5 2.0 2.5 3.0 3.5 4.0

Isen

trop

ic w

ork

[kJ/

kg]

Pow

er p

er m

ass f

low

[W /

g/s

ec]

Pressure ratio Π [-]

Isentropic work as function of pressure ratio Π

cp = 1005 J/kg K, T = 293 K, 𝜅𝜅−1𝜅𝜅

= 0.285 46.4 W / g/sec = 1 kW / Nm3/min

- 15 -

𝑤𝑤𝑡𝑡,12 = 𝑐𝑐𝑝𝑝,𝑚𝑚 ∙ 𝑇𝑇2 − 𝑇𝑇1 = 𝑐𝑐𝑝𝑝,𝑚𝑚𝑇𝑇1 ∙ Π𝜅𝜅−1𝜅𝜅 − 1

Example calculation for gas compression

The (isentropic) technical energy (work) to compress air from ambient pressure (~100 kPaabs) to 250 kPaabs at 20°C is:

𝑤𝑤𝑡𝑡,12 = 𝑐𝑐𝑝𝑝,𝑚𝑚𝑇𝑇1 ∙ Π𝜅𝜅−1𝜅𝜅 − 1 = 1005

𝐽𝐽𝐾𝐾𝐾𝐾𝐾𝐾

∙ 293𝐾𝐾 ∙ 2.50.285 − 1 = 88𝐾𝐾𝐽𝐽𝐾𝐾𝐾𝐾

An automotive stack requests 100 g/sec air at nominal power. What is the isentropic technical power for compression?

𝑃𝑃𝑡𝑡,𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑡𝑡𝑖𝑖𝑖𝑖𝑝𝑝𝑖𝑖𝑖𝑖 = �̇�𝑚 ∙ 𝑤𝑤𝑡𝑡 = 100𝐾𝐾𝑠𝑠𝑠𝑠𝑐𝑐

∙ 88𝑊𝑊

𝐾𝐾 𝑠𝑠𝑠𝑠𝑐𝑐⁄ = 8.8 𝐾𝐾𝑊𝑊

Air temperature T2 after compression is:

𝑇𝑇2 = 𝑇𝑇1 ∙ Π𝜅𝜅−1𝜅𝜅 = 293𝐾𝐾 ∙ 2.50.285 = 380𝐾𝐾 𝑜𝑜𝑜𝑜 107°𝐶𝐶

- 16 -

(Electric) efficiency of gas compression

The electric efficiency of an electric compressor is defined as: 𝜂𝜂𝑖𝑖𝑒𝑒 = 𝑃𝑃𝑡𝑡,𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑡𝑡𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖

𝑃𝑃𝑖𝑖𝑒𝑒

Example (from previous slide): 𝑃𝑃𝑡𝑡,𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑡𝑡𝑖𝑖𝑖𝑖𝑝𝑝𝑖𝑖𝑖𝑖 = 8.8 𝐾𝐾𝑊𝑊 𝑃𝑃𝑖𝑖𝑒𝑒 = 13 𝐾𝐾𝑊𝑊 𝜂𝜂𝑖𝑖𝑒𝑒 = 8.8 𝑘𝑘𝑘𝑘

13 𝑘𝑘𝑘𝑘= 67.7%

Air in Compressor Air out w

el w

loss

- 17 -

0

50

100

150

200

250

300

350

1.0 1.5 2.0 2.5 3.0 3.5 4.0

Isen

trop

ic w

ork

[kJ/

kg]

Pressure ratio P [-]

OK

η=50%

isentropic η=100%

1.0

1.2

1.4

1.6

1.8

2.0

2.2

2.4

2.6

2.8

0 50 100 150 200 250 300

Π[-]

Air mass flow [kg/h]

1100010000900080007000600050004000300025002000

Rotary screw compressor

www.power-technology.com

1530

60125

200280

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

1.0

1.1

1.2

1.4

1.6

2.0

2.4

2.8

Air

mas

s flo

w [

kg/h

r]

Effi

cien

cy [-

]

Π [-]

0.6-0.7

0.5-0.6

0.4-0.5

0.3-0.4

0.2-0.3

0.1-0.2

0-0.1

Air mass flow is a function of rotation speed and nearly independent of pressure ratio Π.

- 18 -

rmp

Rotary screw compressor performance map

http://www.eaton.com/Eaton/ProductsServices/ProductsbyCategory/Automotive/RootsSuperchargers, (November 28, 2012)

- 19 -

Electric turbo charger – where we are today

http://www.springerprofessional.de/tdi-workshop-bei-audi/5230184.html (July 22, 2014)

- 20 -

electric turbo for Audi TDI ICE manufactured by VALEO in addition to state-of-the-art

exhaust-driven turbocharger 7 kWel input power 48 VDC power supply 250ms to max speed

DOE Technical Target – Air Compressor for 80kW

Relevant information (w/o) expander:

- 21 -

idle 25% full

Flow [g/sec] 4.6 23 92

Pressure [kPaabs] 120 150 250

Comp. eff. [%] 60 65 75

Motor eff. [%] 70 80 90

Input power [kW] 0.2 2 14

Source: DOE Hydrogen and Fuel Cells Program FY 2014 Annual Progress Report Multi-Year Research, Development and Demonstration Plan, Technical Plan — Fuel Cells (Status July 2013)

Air “power” flows in fuel cell stacks

Example: 250 A, 250 cells, λcathode = 1.8, λanode = 1.1, AveCell = 700mV Values are power in kW.

Stack - H2 / - O2

+ H2O

2Hfuel

airairair

nHHVPmhP

⋅=⋅=

70°C/80% 200kPa

12.2 27.2

20°C/50% 101kPa

1.7

80°C/100% 155kPa

10.5

air enthalpy

Humidification & compression

10.5

60°C/100% 155kPa

16.7

?

- 22 -

Gas-to-gas humidifier

Stack - H2 / - O2

+ H2O

Gas-to-gas humidifier

“hot” air in (> 100°C)

from compressor

Stack cathode out: Fully humidified at e.g. 80°C

FCS air exhaust: Fully humidified at e.g. 60°C

Characteristic: Humidity (and heat) exchange capability (at different volume flows).

www.permapure.com

- 23 -

DOE AMR 2012 FC067

Gas humidification versus flow rate

www.permapure.com (November 28, 2012)

- 24 -

Flow rate (Liters per minute)

Dew

Poi

nt [°

C]

- 25 -

Fuel cell vehicles

Vehicle electrification

- 26 -

M M

G

M M M

ICE Vehicle

Parallel Hybrid V

Plug-in Hybrid V

Range Extender V

Battery Electric V

Fuel Cell Vehicle

Motivation: Cars are responsible for around 12% of total EU emissions of carbon dioxide (CO2). The fleet average to be achieved by all new cars is 95g/km by 2020/2021. This represent reductions of 40% respectively compared with the 2007 (158.7g/km). 95g/km equates to approximately 4.1 l/100 km of petrol or 3.6 l/100 km of diesel. http://ec.europa.eu/clima/policies/transport/vehicles/cars/index_en.htm (November 17, 2014)

- 27 -

Electrification of the vehicle

Source. GM Powertrain Strategy - Electrification of the Vehicle

Exhaust enthalpy ICE versus FCS

- 28 -

- 29 -

Fuel cost estimation – Hydrogen versus gasoline

▪ Gasoline ICE vehicle (with taxes) Fuel costs: 1.60 €/liter (inclusive German taxes) Costs per fueling: 80 € (50 liter tank) Driving range: 714 km (with 7 liter/100 km fuel consumption) Fuel costs: 11.2 € / 100 km

▪ Hydrogen FC vehicle (w/o taxes) Fuel costs: 9 €/kg (future cost estimation is ~4 €/kg) w/o tax Costs per fueling: 45 € (5 kg tank) Driving range: 385 km (with 1.3 kg/100 km efficiency) Fuel costs: 11.7 € / 100 km

Vehicle driving power and energy

Driving forces: 𝐹𝐹𝑎𝑎𝑖𝑖𝑖𝑖 𝑑𝑑𝑖𝑖𝑎𝑎𝑑𝑑 = 12⁄ ⋅ 𝐴𝐴 ⋅ 𝜌𝜌 ⋅ 𝑐𝑐𝑤𝑤 ⋅ 𝑣𝑣2

𝐹𝐹𝑖𝑖𝑖𝑖𝑒𝑒𝑒𝑒𝑖𝑖𝑖𝑖𝑑𝑑 = 𝑓𝑓𝑤𝑤𝑤𝑖𝑖𝑖𝑖𝑒𝑒 ⋅ 𝐹𝐹𝑚𝑚, 𝐹𝐹𝑚𝑚 = 𝑚𝑚 ⋅ 𝐾𝐾 𝐹𝐹𝑎𝑎𝑖𝑖𝑖𝑖𝑖𝑖𝑒𝑒𝑖𝑖𝑖𝑖𝑎𝑎𝑡𝑡𝑖𝑖𝑖𝑖𝑖𝑖 = 𝑚𝑚 ⋅ 𝑎𝑎 𝐹𝐹𝑡𝑡𝑖𝑖𝑡𝑡𝑎𝑎𝑒𝑒 = 𝐹𝐹𝑎𝑎𝑖𝑖𝑖𝑖 𝑑𝑑𝑖𝑖𝑎𝑎𝑑𝑑 + 𝐹𝐹𝑖𝑖𝑖𝑖𝑒𝑒𝑒𝑒𝑖𝑖𝑖𝑖𝑑𝑑 + 𝐹𝐹𝑎𝑎𝑖𝑖𝑖𝑖𝑖𝑖𝑒𝑒𝑖𝑖𝑖𝑖𝑎𝑎𝑡𝑡𝑖𝑖𝑖𝑖𝑖𝑖 Driving power 𝑃𝑃 = 𝐹𝐹 ⋅ 𝑣𝑣 [𝑃𝑃] = 𝑊𝑊 (or k𝑊𝑊) Vehicle parameter: m,𝐴𝐴, 𝑐𝑐𝑤𝑤, 𝑓𝑓𝑤𝑤𝑤𝑖𝑖𝑖𝑖𝑒𝑒 Energy E = ∫𝑃𝑃 [𝐸𝐸] = 𝐽𝐽 or kWℎ

- 30 -

Driving power and energy (at constant vehicle speed)

Example: Main vehicle specifications from EUCAR Improved Reference Vehicle (C-Segment) for 2020+

m = 1250 kg,𝐴𝐴 = 2.2 𝑚𝑚2, 𝑐𝑐𝑤𝑤 = 0.24, 𝑓𝑓𝑤𝑤𝑤𝑖𝑖𝑖𝑖𝑒𝑒 = 0.005 Steady state, no dynamics (e.g. acceleration)!

- 31 -

v [km/h] v [m/s] F_air [N] P_rolling [kW] P_air [kW] P_total [kW] Energy/100km[kWh]

Energy/100km[MJ]

30 8,33 22,0 0,51 0,18 0,7 2,3 8,350 13,89 61,2 0,85 0,85 1,7 3,4 12,380 22,22 156,7 1,36 3,48 4,8 6,1 21,8

100 27,78 244,9 1,70 6,80 8,5 8,5 30,6120 33,33 352,6 2,04 11,75 13,8 11,5 41,4160 44,44 626,8 2,73 27,86 30,6 19,1 68,8

0

20

40

60

80

100

0 50 100 150 200 250

Driv

e po

wer

[kW

]

Vehicle speed [km/h]

New European Driving Cycle (NEDC)

- 32 -

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0

20

40

60

80

100

120

0 200 400 600 800 1000 1200

Ener

gy [k

Wh]

Spee

d [k

m/h

] / p

ower

[kW

]

Time [sec]

v [km/h]P_powertrain [kW]Energy [kWh]

Power and energy is vehicle specific!

Vehicle efficiency

For a specific vehicle the efficiency can be calculated.

𝜂𝜂 =(𝑢𝑢𝑠𝑠𝑠𝑠𝑓𝑓𝑢𝑢𝑢𝑢) 𝑠𝑠𝑒𝑒𝑠𝑠𝑜𝑜𝐾𝐾𝑒𝑒 𝑜𝑜𝑢𝑢𝑜𝑜𝑜𝑜𝑢𝑢𝑜𝑜

𝑠𝑠𝑒𝑒𝑠𝑠𝑜𝑜𝐾𝐾𝑒𝑒 𝑖𝑖𝑒𝑒𝑜𝑜𝑢𝑢𝑜𝑜=𝑑𝑑𝑜𝑜𝑖𝑖𝑣𝑣𝑠𝑠 𝑐𝑐𝑒𝑒𝑐𝑐𝑢𝑢𝑠𝑠 𝑠𝑠𝑒𝑒𝑠𝑠𝑜𝑜𝐾𝐾𝑒𝑒 𝑑𝑑𝑠𝑠𝑚𝑚𝑎𝑎𝑒𝑒𝑑𝑑

𝑓𝑓𝑢𝑢𝑠𝑠𝑢𝑢 𝑠𝑠𝑒𝑒𝑠𝑠𝑜𝑜𝐾𝐾𝑒𝑒 𝑖𝑖𝑒𝑒𝑜𝑜𝑢𝑢𝑜𝑜

Drive cycle energy demand: For a specific vehicle and a specific driving cycle the energy demand can be calculated. Fuel energy input: For a specific fuel the energy input can be calculated. For diesel or gasoline this is the fuel consumption With EUCAR Improved Reference vehicle (C-segment) for 2020+ (1) the theoretic drive cycle energy demand based on NEDC is 31.78 MJ / 100km.

- 33 -

(1) m = 1200 kg, fwheel = 0.005, cw = 0.24, A = 2.2 m2

Average vehicle efficiency with NEDC

Drive cycle energy demand at NEDC: 8.828 kWh or 31.78 MJ / 100 km

Gasoline ICE Direct Hydrogen FCV Energy density 9 kWh/liter (50g/kWh) 33 kWh/kg (LHV) Fuel consumption 6 liter / 100 km 1 kg / 100 km Total fuel energy 54 kWh / 100 km 33 kWh / 100 km Total fuel efficiency 8.828/54= 16 % 8.828/33 = 27 %

- 34 -

0%

10%

20%

30%

40%

50%

60%

70%

0 20 40 60 80Ef

ficie

ncy

[%]

FCS net power [kW]Source: Engine Modeling of an ICE Jason Meyer, 2007

Electric motor versus ICE

- 35 -

Source: ika RWTH Aachen University, Prof. Biermann, 1999

Gasoline = 50g/kWh

Compare Fuel Cell Vehicles

- 36 -

https://www.fueleconomy.gov/feg/fcv_sbs.shtml

- 37 -

Fuel cell vehicles today

▪ Many OEMs are working in fuel cell technologies ▪ U.S. DOE

www.fueleconomy.gov energy.gov/public-services/vehicles 2013 Fuel Cell Technologies Market Report

▪ H2 moblity

www.netinform.net/H2/H2Mobility

▪ CEP cleanenergypartnership.de

- 38 -

GM Equinox Fuel Cell GM Equinox / Opel HydroGen4 (2008) Stack: 93kW FCS: 73 kW cont., 94 kW max ETS: 73 kW Max Speed: 160 km/h H2 tank: 70 Mpa, 4.2 kg Battery: Li-Ion, 1.8 kWh Fuel cons.: ~ 1kg / 100 km

http://media.gm.com/media/us/en/gm/news.detail.html/content/Pages/news/us/en/2014/May/0507-fuel-cell.html http://www.netinform.net/h2/H2Mobility/Default.aspx

- 39 -

Daimler B-class f-cell

Daimler B-class F-cell (2013) Stack: 90kW FCS: 100 kW, 290 Nm ETS: 90kW, 280 Nm Max Speed: 170 km/h H2 tank: 70 MPa Battery: Li-Ion, 30 kWpeak, 1.4 kWh Fuel cons.: ~1 kg/100 km (NEDC)

blog.mercedes-benz-passion.com/2013/01/antriebsstrang-kunftiger-f-cell-fahrzeuge/ cleanenergypartnership.de and www.daimler.com

Daimler FCS packaging

- 40 -

Source: https://adacemobility.wordpress.com/2013/01/29/drei-engel-fur-die-brennstoffzelle/

- 41 -

Nissan

Nissan X-Trail FCEV (2006) Stack: 90kW FCS: ETS: 90kW, 280 Nm Max Speed: H2 tank: 70 MPa Battery: Li-Ion Fuel cons.:

Nissan TeRRA SUV concept (2012) Next generation fuel cell stack (> 2.5 kW/liter)

http://www.netinform.net/h2/H2Mobility/Default.aspx http://photos.nissan-global.com

- 42 -

Toyota Mirai

Toyota FCV Mirai (2015) Stack: PEM, 3.1 kW/liter, 114 kW, 370cells FCS: ETS: 113 kW, 335 Nm Max Speed: 180 km/h H2 tank: 70 MPa, 5.7 weight%, ~5 kg Battery: NiMH Fuel cons.: ~1 kg/100 km (JC08 mode)

www.toyota-global.com/innovation/environmental_technology/fuelcell_vehicle/ www.toyota.com/fuelcell/fcv.html

- 43 -

Hyundai ix35 Stack: PEM, 100 kW FCS: ETS: 100kW, 300 Nm Max Speed: 160 km/h H2 tank: 70 MPa, 5.64 kg Battery: Li-Ion, 24kW? Fuel cons.: 0.95 kg/100 km (NEDC)

http://www.hyundai.de/Modelle/Alle-Modelle/ix35-Fuel-Cell.html , Nov 20, 2014 http://www.focus.de/auto/elektroauto/hyundai-ix35-fuel-cell-wasserstoff-suv-fuer-jedermann_id_4339445.html, Dec 12, 2014

- 44 -

Honda Clarity Fuel Cell

Clarity Fuel Cell (2015) Stack: > 3.1 kW/l, > 100kW FCS: ETS: 130 kW Max Speed: H2 tank: 70 MPa Battery: Li-Ion Fuel cons.: 700 km (JC08 mode)

http://www.greencarcongress.com/2015/10/20151027-clarity.htm http://world.honda.com/news/2015/4151028eng.html

- 45 -

Audi A7 Sportback h-tron quattro

Stack: FCS: ETS: 170kW, 540Nm, 2 E-motors Max Speed: 180 km/h H2 tank: 70 MPa, ~5kg Battery: Li-Ion, 8.8 kWh Fuel consumption: ~1 kg/100 km (NEDC)

www.audi-mediaservices.com/publish/ms/content/en/public/pressemitteilungen/2014/11/19/audi_a7_sportback.html, Nov 20, 2014

- 46 -

VW Golf Variant HyMotion

Stack: FCS: 100kW ETS: Max Speed: H2 tank: Battery: Li-Ion Fuel consumption:

www.volkswagenag.com/content/vwcorp/info_center/de/news/2014/11/hymotion.html, Nov 20, 2014

- 47 -

Fuel cell vehicles today

Mercedes Citaro FuelCELL Hybrid (2009) 150 kW (120 kW net power) AFCC PEMFC Li-tec lithium-ion-battery (250 kW) 350 bar

Linde E30 FC Forklift (2010)

Source: www.h2mobility.org

- 48 - - 48 -

Projected automotive FCS costs 1/2

Source: DOE Mass Production Cost Estimation for Direct H2 PEM FCS for Automotive Applications: 2010 Update

$770,35

$153,26$356,91

$70,74

$152,96

$82,11

$225,49

$156,69 Air Loop

Humidifier and Water Recovery Loop

High-Temperature Coolant Loop

Low-Temperature Coolant Loop

Fuel Loop

System Controllers

Sensors

Miscellaneous

429,07

230,78

694,83

242,57

8,16

2,82

301,42

25,54 0,5419,86 5,07 5 5,16 32,06 28,06

Bipolar Plates (Stamped)MembranesCatalyst Ink&Application (NSTF)GDLsM&E Hot PressingM&E Cutting&SlittingMEA Frame/GasketsCoolant Gaskets (LaserWelding)End Gaskets (ScreenPrinting)End PlatesCurrentCollectorsCompression BandsStack HousingStack AssemblyStack Conditioning

In total costs (US$): Stack 2030 23.10/kWgross BOP 1969 24.60/kWnet FCS 3999 49.99/kWnet

2010 system mass production FCS 80 kWnet, Stack 87 kWgross 500,000 units per year BOP

Stack

MEA = 73%!

- 49 - - 49 -

Projected automotive FCS costs 2/2

Source: McKinsey 2010, A portfolio of power-trains for Europe: a fact-based analysis

Platinum price

- 50 -

- €

10 €

20 €

30 €

40 €

50 €

60 €

70 €

80 €

Jan 1992 Jan 1996 Jan 2000 Jan 2004 Jan 2008 Jan 2012

Plat

inum

pric

e [€

US$

/ g]

Date

Pt price [US$ / g]

http://www.platinum.matthey.com/prices/price-charts

- 51 -

alexander.kabza@zsw-bw.de

“Yes, my friends, I believe that water will one day be employed as fuel, that hydrogen and oxygen which constitute it, used singly or together, will furnish an inexhaustible source of heat and light, of an intensity of which coal is not capable.“

Jules Verne The Mysterious Island (1875)

- 52 -

Backup slides …

Automotive Fuel Cell System controls

- 53 -

Temperature and pressure in a FC vehicle stacks

The system (stack) temperature is depending on vehicle speed (cooling capability or radiator as a function of speed and ambient temp.) and required FCS power. Worst case: Uphill with trailer at hot ambient temperature.

Higher cathode air temperature can uptake more water. Therefore stack may dry out due to increased water removal. Dry membrane means low performance!

Air specific humidity (kg/kg) gets lower with increasing pressure.

Option to prevent stack from running dry at hot temperature: Increase cathode pressure!

- 54 -

Theory behind stack temp. and cathode pressure dependency

RH at cathode exhaust is a function of cathode stoichiometry, temperature and pressure:

Air water uptake is a function of temperature and pressure! High temp = high water uptake High pressure = less water uptake

- 55 -

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

60 65 70 75 80 85 90

Spec

ific

hum

idity

Ysa

t [kg

/kg]

Temperature t [°C]

101.3 kPa120 kPa150 kPa200 kPa

RH is 100% (saturation)

Stack- H2 / - O2

+ H2O

70°C/80%200kPa

80°C/100%155kPa

air and water in

air and water out

𝜑𝜑 =𝑜𝑜𝑖𝑖𝑎𝑎𝑡𝑡𝑤𝑖𝑖𝑑𝑑𝑖𝑖 𝑖𝑖𝑜𝑜𝑡𝑡𝑒𝑒𝑖𝑖𝑡𝑡

12 ∙ 𝑜𝑜𝑤𝑤𝑖𝑖(𝑜𝑜) ∙ 1 + 𝜆𝜆𝑖𝑖𝑎𝑎𝑡𝑡𝑤𝑖𝑖𝑑𝑑𝑖𝑖

𝑥𝑥𝑂𝑂2

Cathode exhaust pressure as a function of T, Stoic and inlet RH

Baseline (Cathode inlet): T.Si.CL = 70°C RH.Si.C = 50% Stoic.S.C = 1.5 RH criterion for Cathode outlet: RH.So.C = 100%

Temp. limits at p.So.C: 150 kPaabs 80°C

200 kPaabs 87°C 250 kPaabs 93°C FCS controls: Low temp. = low pressure, high temp. = high pressure - 56 -

Operating temperature versus pressure

An automotive FCS runs normally NOT a constant temperatures. During cold startup: -40°C < T < 0°C During warm-up: 0°C < T < 70°C During normal operation: 70°C < T < 90°C FCS power reduction: T > 90°C At T ≥ 60°C typically pressure is increased and/or cathode air is humidified to ensure proper stack water management (RH-criterion at stack cathode exhaust!).

- 57 -

-40 0 25 100 70

100

200

300

T [°C]

p [kPaabs]

0

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0 20 40 60 80 100

Cell

volta

ge [V

]

Stack load [%]

300 kPaabs275250225200175150125100System

Impact of temp and pressure on system PolCurve

FCS controls: Low el. load = low thermal load = low temperature = low pressure High el. load = high thermal load = high temperature = high pressure

- 58 -

Automotive Fuel Cell System simulation with MATLAB/Simulink

- 59 -

Why do we need FCS simulation results?

Fuel Cell Vehicle simulation can answer questions like:

What stack operating conditions do I get at which stack load point?

What is the effect of FCS efficiency at lower stack cathode pressure?

What is the hydrogen consumption at different driving cycles?

What effect has the compressor efficiency to the overall system efficiency?

What are the stack idle operating conditions?

What impact has the membrane resistance to the FCS peak efficiency?

What impact does the compressor dynamic has on system dynamics? - 60 -

Fuel Cell System simulation

- 61 -

Input Output Simulation

Simulation workflow

- 62 -

0

10

20

30

40

50

60

70

80

0 300 600 900 1200 1500 1800

Stac

k lo

ad [A

]

Time [sec]

0

20

40

60

80

100

0 300 600 900 1200 1500 1800

Spee

d [k

m/h

]

time [sec]

Fuel Cell Stack

Teststand

Standard Driving cycle

Stack load request

Simulation input

Fuel Cell Stack PolCurves LUT with stack cathode outlet pressure (p.So.C) dependency

Fuel Cell Stack operating conditions LUT (Stoic.S.A, Stoic.S.C, Coolant flow rate F.Si.CL) as a function of current density (Idens.S)

Stack coolant inlet temperature (T.Si.CL) is currently fixed e.g. T.Si.CL = 80°C

Vehicle parameter (mass, air drag coefficient, rolling resistance, etc.) Driving cycle (vehicle speed over time) Compressor efficiency LUT (efficiency as a function of Π and F.Cmp.Air)

- 63 -

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0 0.5 1 1.5

Cell

volta

ge [V

]

Current density [A/cm2]

100 125 150175 200 225250 275 300

1.001.15

1.401.802.403.00

00.10.20.30.40.50.60.7

8.33

16.6

7

33.3

3

69.4

4

111.

11

155.

56

0.6-0.7

0.5-0.6

0.4-0.5

0.3-0.4

0.2-0.3

0.1-0.2

0-0.1

Integrated calculators and models

Reactant mass flow calculator: based on stoics and Faraday Stack Power Calculator: calculate electric (P.S.el) and thermal (P.S.therm)

stack power Stack Coolant dT calculator: calculate coolant dT based on coolant flow rate

(F.S.CL) and thermal stack power (P.S.therm) Cathode backpressure calculator: Calculates the stack cathode outlet

pressure (p.So.C) as a function of stack coolant outlet temperature (T.So.CL) cathode stoichiometry (Stoic.Si.C) cathode inlet temperature (T.Si.C), pressure (p.Si.C) and RH (RH.Si.C) Required cathode outlet RH (RH.So.C), e.g. RH.So.C = 100%

Stack cathode dp calculator: stack cathode pressure drop (dp.S.C) is calculated based on one pressure drop measurement Theory: Orifice equation

Compressor: Calculates the isentropic work for air compression based on stack cathode inlet pressure (p.Si.C) and required air mass flow (F.Si.F.req) P.CMP.el = P.CMP.isen * efficiency (LUT)

- 64 -

Simulation output

The following parameters are simulated as a function of drive cycle runtime: Stack voltage (U.S), current (I.S), electric (P.S.el) and thermal (P.S.therm)

power, efficiency Stack outlet temperature (T.So.CL) and dT (dT.S.CL) and stoics (Stoic.S.A and

Stoic.S.C), stack cathode outlet pressure (p.So.C) and pressure drop (dp.S.C) Hydrogen and air mass flow (F.Si.A and F.Si.C) Compressor outlet temperature (T.Cmpo.Air) Fuel Cell System: net power (P.FCS.net), efficiency

- 65 -

Example 1 – Stack PolCurve

- 66 -

0

50

100

150

200

250

300

350

400

450

500

0 20 40 60 80 100 120

I.S [A

] / U

.S [V

]

P.FCS.net [kW]

I.S [A]U.S [V]

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0 0.5 1 1.5

Cell

volta

ge [V

]

Current density [A/cm2]

Example 1 – Power

- 67 -

0

20

40

60

80

100

120

140

160

180

200

0 20 40 60 80 100 120

Pow

er [k

W]

P.FCS.net [kW]

P.S.el [kW]

P.S.therm [kW]

P.CMP.el [kW]

P.CMP.isen [kW]

Example 1 – Temperature

- 68 -

0

10

20

30

40

50

60

70

80

90

100

0 20 40 60 80 100 120

Tem

pera

ture

[°C]

P.FCS.net [kW]

T.Si.CL [°C]T.So.CL [°C]dT.S.CL [K]

Example 1 – Pressure

- 69 -

0

50

100

150

200

250

300

350

400

0 20 40 60 80 100 120

Pres

sure

[kPa

]

P.FCS.net [kW]

p.Si.C [kPa]

dp.S.C [kPa]

p.So.C [kPa]

0%

10%

20%

30%

40%

50%

60%

0 20 40 60 80 100 120

FCS

effic

iync

y [%

]

P.FCS.net [kW]

FCS el eff [%]

Example 1 – FCS efficiency

- 70 -

Source: BMW, 2012

Example FCS efficiency charts

- 71 -

Source: NuCellSys HY-80, 2009

Source: BMW, 2012

Source: Hydrogenics, 2013

0

5

10

15

20

25

30

35

40

45

0

50

100

150

200

250

300

350

400

450

0 200 400 600 800 1000 1200

Vehi

cle

spee

d [m

/sec

]

I.S [A

] / U

.S [V

]

Time [sec]

I.S [A]U.S [V]Vehicle speed

Example 2 – NEDC

- 72 -

One simulation result: Fuel consumption E.g. 0.8 kg H2 / 100km during NEDC

- 73 -

Effect of FCS hybridization with batteries

Hybridization reduces FCS dynamics while the battery supports peak power.

0

10

20

30

40

50

60

70

0

20

40

60

80

100

120

140

0 100 200 300 400 500 600

Pow

er [k

W]

Vehi

cle

spee

d [k

m/h

]

time [sec]

speed [km/h]P_powertrain [kW]Pave _5sec [kW]

With an EV from Munich to Barcelona

From Munich to Barcelona (1,352 km) with an Renault Zoe. Total electric energy consumption: 210 kWh Total “fuel” costs: 51.50 € (3.81 € / 100 km) Average consumption: 15.5 kWh/100km

- 74 -

http://www.mein-elektroauto.com/2013/11/mit-dem-elektroauto-renault-zoe-von-muenchen-nach-barcelona/11921/, Nov 30, 2013