Analysis of Fuel Cell Systems

Rangan BanerjeeEnergy Systems Engineering

IIT Bombay

Lecture in CEP Course on ‘Fuel Cell’ at IIT 14th November 2007

Overview of Talk

Energy Crisis – Motivation for fuel cells

Criteria

Listing of Pathways

Vehicles

Energy chain - Primary Energy Analysis

Cost Analysis

Renewable Hydrogen

Energy CrisisPresent energy systems – fossil fuel based (~80%)Finite fossil fuel reserves (Oil-Gas ~ 50 years, coal ~100 years)Adverse local, regional and global environmental impacts Global warming (Greenhouse gas problem)

Carbon Dioxide Concentrations

Carbon Dioxide Concentrations

Hydrogen EnergyCan hydrogen energy mitigate the energy problem?How does the hydrogen energy system compare with existing energy conversion routes?Is this a sustainable solution?A- Vehicle – 4 wheeler passenger car B-Distributed Power Generation

Hydrogen pathways

Photo chemical

Solar Energy Nuclear Energy Bio-Energy

Electricity

Wind

Thermal

ElectrolysisThermo chemical

Fossil-Fuel

Photo biological

Hydrogen

Gasification Fermentation

Cracking + Shift Reaction

Fuel Cell

ENERGY FLOW DIAGRAMPRIMARY ENERGY

ENERGY CONVERSION FACILITY

SECONDARY ENERGY

TRANSMISSION & DISTRN. SYSTEM

FINAL ENERGY

ENERGY UTILISATION EQUIPMENT & SYSTEMS

USEFUL ENERGY

END USE ACTIVITIES

(ENERGY SERVICES)

COAL, OIL, SOLAR, GASPOWER PLANT, REFINERIESREFINED OIL, ELECTRICITY

RAILWAYS, TRUCKS, PIPELINESWHAT CONSUMERS BUY DELIVERED ENERGYAUTOMOBILE, LAMP, MOTOR, STOVEMOTIVE POWER RADIANT ENERGYDISTANCE TRAVELLED, ILLUMINATION,COOKED FOOD etc..

Source : Energy After Rio: UNDP Publication.

CriteriaPrimary Energy Analysis – primary energy/

unit output (kJ/kWh , kJ/km )

Emissions - Local, Global

Cost - Initial Cost, Operating Cost,

Annualised Life Cycle Cost

Sustainability (Renewable?)

Primary Energy Analysis

Compare options based on primary energy input

MotivationFossil fuel scarcity, adverse environmental effects (local and global)Indian transport sector

22% of total commercial energy Share in total pollutant load; 70% in New Delhi, 52% in Bombay

Need for alternative transport fuels.Indian government’s emphasis on biodiesel, hydrogen ..

Fuel chains

Refinery

Vehicle (Utilization)

Filling stations (Petrol storage and delivery)

Crude oil production centre

Intercontinental crude oil transport

Petrol transport (via Rail/Truck)

Primary energy source

Vehicle (On-board storage and utilization)

Hydrogen production centre (Production and compression)

Filling stations (Hydrogen storage and delivery)

Pipeline transport

Hydrogen fuel chainFossil fuel chain

Base case Fossil fuel based fuel chainSmall-size passenger car (Maruti 800) manufactured by Maruti Udyog Limited

Petrol fuelled, 37 bhp (27 kW) IC engine

50% share in Indian passenger vehicle-market

560,000 units sold 2005-6

Vehicle ApplicationWeight (excl engine

+tank) 550 kgPassengers (max)

350 kgMarutiCR 0.01CD 0.42m2 front area100 km travel /day

Tank Engine

Petrol 40 kg 60 kg

CNG 140 kg 60 kg

FC 130 kg 15 M +15 FC kg

B1) PETROL ENGINE

SHAFT WORK

OIL MINING/REFINING

IC ENGINE

TRANSMISSION

TRANSPORT OF PETROL

η OM 95 %

η TP 97%

η PE 30 %

CRUDE OIL

η TRANS 70 %

B2) GAS ENGINE

SHAFT WORK

EXTRACTION

COMPRESSION

CNG ENGINE

NATURAL GAS TRANSPORT

η OM 95 %

η TD 97%

η C 90%

NATURAL GAS

η GE 40%

TRANSMISSION η TR70%

FUEL CELL (NG)η E 95 %

η GT 97 %

η FC 40 %

η REF 85 %

η PC 95 %SHAFT WORK

NATURAL GAS

EXTRACTION

NATURAL GAS TRANSPORT

HYDROGEN

STEAM REFORMING

ELECTRICITY

PEM FUEL CELL

POWER CONDITIONING

MOTOR

TRANSMISSION

ηm 90%

ηTR 91%

Vehicle Comparison

A1 Overall efficiency 19.4%3.31 kg of crude /100 km of travel

A2 Overall efficiency 23.2%3.0 kg of Natural gas/ 100 km of

travelFuel cell Overall efficiency 24.3%2.82 kg of Natural gas/ 100 km of travel

Vehicle Carbon Emissions

A1 – Crude oil (86% Carbon) 2.84 kg Carbon/100 km of travelA2- Natural gas (75% Carbon)2.25 kg Carbon/ 100 km of travel

Fuel cell ( 18 kg of Carbon / 1 GJ of Hydrogen energy – SMR)

FC 2.11 kg Carbon/100 km of travel

Hydrogen fuel chain – different routes

Hydrogen Production

Storage

Utilization

Steam methane reforming (SMR), Coal gasification, Water electrolysis, Renewable hydrogen (Photovoltaic-electrolysis, Wind power-electrolysis, Biomass gasification, Biological methods)

Compressed hydrogen storage, Metal hydrides, Liquid hydrogen storage, Complex chemical hydrides

Fuel cells (PEMFC), IC engine

Transmission Pipeline transport, transport via truck and rail

Comparison criteriaNon-renewable energy consumption per km travel (MJ/km)Greenhouse gas emissions per km travel (g CO2-eq/km)Cost per km travel (Rs./km)

Annualised life cycle costing (ALCC) methodExisting Indian prices.If technology is not available commercially in India, international prices are used

Resource constraints

Methodology

Life cycle assessment (LCA) All material and energy inputs to the process are identifiedTotal input energy required to extract, produce, and deliver a given energy output or end use

Energy use and corresponding emissions during fabrication of PV, electrolyzer, wind machine etc. are also taken into account.

Methodology contd..

Inventory (process energy and material) to produce one unit of output

Classification of total primary energy into non-renewable and renewable energy

Non-renewable energy useGHG emissions

Total primary energy required to produce required process energy and materials

Cost of different equipment and material required, discount rate, life of the equipment

Life cycle cost

Materials and other resources such as water, land etc required to produce 1 kg of hydrogen

Resource constraint

Amount of material and other resources required to meet the current demand

Process flow chartsSizing of different equipment required

Total GHG emissions in producing process energy and materials (using emission factors)

Resource constraint

Resource constraint

Material supply constraint

Area

Material constraint

Other constraint

Annual requirement/Reserve

Area required/Available land area

Annual requirement/Reserve

No constraint

Technical constraint, water for biomass based systems etc.

Source: Manish S, Indu R Pillai, and Rangan Banerjee, "Sustainability analysis of renewables for climate change mitigation," Energy for Sustainable Development, vol. 10, no. 4, pp. 25-36, 2006.

Energy analysisPower required at wheels

Transmission and IC engine efficiency

Fuel requirement from fuel tank

Input (Drive cycle,Vehicle weight,Front area, Air density, Cd, Cr)

IC engine vehicle

Power required at wheels

Transmission, Fuel cell and Electric motor efficiency

Fuel requirement from fuel tank

Input (Drive cycle,Vehicle weight,Front area, Air density, Cd, Cr)

Fuel cell vehicleSource: Manish S and Rangan Banerjee, "Techno-economic assessment of fuel cell vehicles for India," 16th World hydrogen energy conference, Lyon (France), 2006.

Indian urban drive cycle

Indian urban drive cycle :-

Low average speed (23.4 km/h) and rapid accelerations (1.73 to -2.1 m/s2)

European urban drive cycle :-

Average speed (62.4 km/h) and accelerations from 0.83 to -1.4 m/s2

0

2

4

6

8

10

12

14

16

18

20

0 500 1000 1500 2000 2500 3000

Time (s)

Spee

d (m

/s)

Avg. speed - EUDC

Avg. speed IUDC

Power required at wheelsThree forces acts on the vehicle (Assumption:-vehicle is running on a straight road with a zero gradient). These are

Aerodynamic drag {FDrag(t)} = 0.5ρAv(t)2Cd

Frictional resistance {FFriction(t)} = mgCr

Inertial force {FInertia(t)} = mf {f=dv(t)/dt}FTotal(t)=FDrag(t)+FFriction(t)+FInertia(t)PWheel(t)=FTotal(t)×v(t)

Data used for base case vehicleParameterParameter ValueValueAir density (kg/m3) 1.2

Coefficient of drag resistance 0.4

Coefficient of rolling resistance 0.01

Cargo weight (kg) 250

Frontal area (m2) 2

Transmission efficiency 0.7

Transmission weight (kg) 114

IC engine weight (kg) 90

Fuel tank weight (kg) 40

Fuel capacity (kg) 24

Vehicle body weight (kg) 406

Total weight (kg) 900

Result for base case vehicleParameterParameter ValueValueDriving range (km) 434

Cost (Rs/km) 2.8 (0.34)

Non-renewable energy use during operation (MJ/km) 2.6

GHG emissions (g/km) 180

Driving range of hydrogen vehicles should be at least half (~217 kms) for their public acceptance.

•Average daily travel Indian urban <100 kms.

•Vehicle to run for 2-3 days.

Hydrogen fuel chain – Options considered

Hydrogen fuel chain

Production

Steam methane reforming (SMR)

PV-electrolysis (PV)

Wind-electrolysis (WE)

Biomass gasification (BG)

Transmission

Pipeline transport

(PL)

Storage

Compressed hydrogen (C)

Liquid hydrogen (L)

Metal hydride (M)

Utilization

PEM fuel cell

(FC)

IC engine

(IC)

Hydrogen production – Steam Methane Reforming (SMR)

Feedstock - Natural Gas SMR: CH4 + 2H2O 4H2 + CO2

Life of plant 20 yearsExisting NG price Rs 8/Nm3, Price of Hydrogen Rs 48/ kg 4.3 Rs/Nm3 or 400 Rs/GJ

Variation of Hydrogen price with NG price

0

5

10

15

20

25

30

35

40

45

0 5 10 15 20

Natural Gas Price (Rs/Nm3)

Hyd

roge

n pr

ice

(Rs/

Nm

3)

PV-Electrolyzer System

• HYSOLAR (Saudi Arabia) 350 kW Alkaline electrolyser 65 m3/h peak (German-Saudi) ~5.8 kg/hr

PV arrayMPPT and DC-DC converter

Water

Oxygen

PEM Electrolyzer

Hydrogen

PV-Hydrogen

100 kg hydrogen/ dayElectrolyzer efficiency 70%Annual capacity factor 20%Module area 8800 m2

1300 kWp PV, 1200 kW electrolyzer

Wind-ElectrolyzerUtsira Plant

10 Nm3/h (~0.9kg/h)

48 kW electrolyzer

Two wind turbines 600 kW (peak) each

Source: Norsk Hydro

WECSAC-DC converter

Water

Oxygen

PEM Electrolyzer

Hydrogen

Wind-Electrolyzer

100 kg hydrogen/ dayElectrolyzer efficiency 70%Annual capacity factor 30%880 kW (peak), 784 kW electrolyzer

Biomass gasifier-reformer

Many configurations possible – atmospheric, pressurised, air blown, oxygen blown

No large scale systems

Hydrogen

SyngasBiomass

Air

Steam

Gasifier Gas cleaning

Methane steam reforming

Water gas shift reaction

Pressure swing adsorption

Comparison of hydrogen production methods

Indicator Unit SMR PV-electrolysis

WECS-electrol.

BiomassGasification

Non-renewable energy use

MJ/kg 182 67.5 12.4 67.7

GHG emission kg/kg 12.8 3.75 0.98 5.4

Life cycle cost* Rs/kg 48 1220 400 44.7

*At 10% discount rate Average load factors; PV-0.2, WECS-0.3, Biomass gasification-0.65

Hydrogen transmissionCan be transported as a compressed gas, a cryogenic liquid (and organic liquid) or as a solid metal hydride.Via pipeline, trucks, rail etc.Compressed hydrogen via pipeline

US, Canada and EuropeTypical operating pressures 1-2 MPaFlow rates 300-8900 kg/h

Hydrogen transmission-contd..

210 km long 0.25 m diameter pipeline in operation in Germany since 1939 carrying 8900 kg/h at 2 MPaThe longest pipeline (400 km, from Northern France to Belgium) owned by Air Liquide.In US, total 720 km pipeline along Gulf coast and Great lakes.

Results for transmission process

For 1 million kg/day, transmission distance 100 km, supply pressure 10 bar

Parameter Value Unit

Optimum pipe diameter 1 m

Transmission cost 6.93 (0.85UAH/kg) Rs/kg

GHG emissions 0.99 kg/kg

02468

101214161820

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6

Pipe dia (m)

Tran

smis

sion

cos

t (R

s/kg

)

Transmission cost vs. pipe diameter

Hydrogen on-board storage and utilization

Demo hydrogen vehicles : Daimler-Benz, Honda, Toyota, Ford, BMW, General Motors, Daimler-Chrysler, MazdaOn-board storage: compressed gas, liquid hydrogen, metal hydride, organic liquidEnergy conversion device: internal combustion engine, fuel cell

Vehicles with compressed hydrogen storage

Name of thevehicle/Company

Energy conversiondevice

Net poweroutput

Storage system Range ofVehicle(km)

NEBUS (bus)(Daimler-Benz)

Fuel cells10 stacks of 25kW

190 kW 150 litre cylindersat 300 bar

250

Zebus (bus)(Ballard powersystems)

Fuel cells 205 kW Compressedhydrogen

360

FCX (Car)(Honda)

Fuel Cells 100 kW 171 litre at 350bar

570

FCHV-4 (car)(Toyota)

PEM fuel cell+ Battery

80 kW 350 bar 250

Model U(Ford motor co.)

Internal combustionEngine

113 kW@4500rpm

7 kg @690 bar ---

NECAR 2(Daimler Benz)

Fuel cell 50 kW Compressed gas ---

Vehicles with liquid hydrogen storage

Name of thevehicle/Company

Energyconversiondevice

Net poweroutput

Storagesystem

Range ofVehicle(km)

BMW 750-hl(BMW Corporation)

Hybrid, 12 cylindercombustion engine

--- 140 liters, cryostorage at -2530C

400

Hydrogen 3(General motors)

Fuel cell 60 kW 4.6 kg LiquidHydrogen at -253oC

400

Necar4(Daimler Chrysler)

Fuel cell 70 kW --- 450

Vehicles with organic liquid storage

Name of thevehicle/Company

Energyconversion device

Net poweroutput

Storage system

NECAR 5(Daimler Chrysler)

Fuel cell 75 kW Methanol(On board reformer)

FC5(Ford Motor company)

Fuel cell 65kW --do--

Mazda Premacy(Ford Motor company)

Fuel cell 65kW --do--

FCX-V2(Honda Motor company)

Fuel cell 60kW --do--

Vehicles with metal hydride storage system

Name of thevehicle/Company

Energyconversion device

Net poweroutput

Storagesystem

HRX2(Mazda MotorCorporation)

Wankel RotoryEngine

65kW TiFe

FCX-V1(Honda Motorcompany)

Fuel cell 60kW LaNi5

On-board storage + utilizationOption

On-board storage

Energy conversion device

Compressed H2

Fuel cell 21.03 17.8 0.24 0.83

Liquid H2 Fuel cell 21.06 17.8 0.24 0.80

Metal hydride Fuel cell 21.92 26.9 0.36 0.88

Compressed H2

IC engine 1.23 0* 0* 2.47

Liquid H2 IC engine 1.35 0* 0* 2.32

Metal hydride IC engine 4.17 32 0.42 2.74

Cost (Rs/km)

GHGg/km

Non-renewable energy use (MJ/km)

H2 use MJ/km

*Energy use and emissions in base case vehicle manufacturing neglected

Results for hydrogen storage (at filling stations)

Parameter Compressed hydrogen

Liquid hydrogen

Metal hydride

Unit

Delivery and storage cost

8.75 42.6 33.7 Rs/kg

GHG emissions 1.24 7.2 0.28 kg/kg

Non-renewable energy use

12.72 74 3.84 MJ/kg

PV-PL-C-FC

Cost break-up

1.2

19.95.8

2.6

0.0

0.1

8.6

VehicleFuel cellPhotovoltaicElectrolyzerTransmissionStorage

Specific fuel consumption- 6.9 g/kmCost- 29.6 Rs/km GHG emissions- 59.1 g/km BASE CASE

Rs 2.6/km

GHG 180g/km

PV-PL-C-IC

Cost break-up

1.217.3

7.9

0.1

0.2

25.5VehiclePhotovoltaicElectrolyzerTransmissionStorage

Specific fuel consumption-20.6 g/kmCost- 26.7 Rs/kmGHG emissions- 123.2 g/km

BASE CASE

Rs 2.6/km

GHG 180g/km

WE-PL-C-IC

Cost break-up

1.2

2.9

5.2

0.1

0.2

8.5VehicleWECSElectrolyzerTransmissionStorage

Specific fuel consumption- 20.6 g/kmCost- 9.7 Rs/kmGHG emissions- 66.1 g/km

BASE CASE

Rs 2.6/km

GHG 180g/km

SMR-PL-C-IC/SMR-PL-C-FCSMR-PL-C-IC

Specific fuel consumption- 20.6 g/kmCost- 2.5 Rs/kmGHG - 310 g/km

BASE CASE

Rs 2.6/km

GHG 180g/kmSMR-PL-C-FCSpecific fuel consumption- 6.9 g/km

Cost- 21.5 Rs/km

GHG - 122 g/km

BG-PL-C-IC Specific fuel consumption- 20.6 g/kmGHG emissions- 158 g/kmCost

CASE 1 Biomass freely available2.5 Rs/km

CASE 2 Biomass commercially grownDepends on land price4.7 Rs/km

BASE CASE

Rs 2.6/km

GHG 180g/km

Cost break-up

1.2

0.9

2.3

0.1

0.2

3.5 VehicleProductionLand costTransmissionStorage

Cost break-up

1.20.9

0.1

0.2

1.2

VehicleProductionTransmissionStorage

Case 1 Biomass freely available

Case 2 Biomass grown commercially

Hydrogen fuel chain BG-PL-C-IC

BiomassPipeline transport

Production and compression• Hydrogen 2 million kg per day• Area for biomass growth3800 km2 (380000 ha)• Power required 124 MW (for delivery at 10 bar)• Biomass gasifier rating 2000 MWe

H2-IC engine Vehicle

Compressed Hydrogenstorage and delivery

• Storage tank autonomyperiod half day• Storage capacity 1 million kg• Volume of storage 40 million liters @ 200 bar (40000 m3, sphere of 21.2 meter radius,)• Compressor power required143 MW (for hydrogencompression from 10 to 200 bar)

Filling stations

On-board compressedhydrogen storage with IC engine

• Hydrogen use: 2.47 MJ/km• 4.47 kg storage capacity for 217 km range• Storage tank

o Weight ~220 kgo Water capacity @ 200 bar 180 liters

• 2 million kg H2 per day for 1 million vehicles (100 km daily travel)

Biomass gasification

Conclusions (Vehicles)

Renewable hydrogen based fuel chains viable based on GHG emission and non-renewable energy use criteriaCost (Rs/km) higher (for photovoltaics, electrolyzer and fuel-cell based system) than existing petrol based fuel chain.IC engine vehicles lower cost but higher energy consumption than fuel cell vehicles.Hydrogen fuel chain based on SMR process (with compressed hydrogen storage and IC engine) is economically viable. However this fuel chain has higher GHG emissions.

ConclusionsRenewable hydrogen based fuel chains viable based on GHG emission and non-renewable energy use criteriaCost (Rs/km) higher (for photovoltaics, electrolyzer and fuel-cell based system) than the existing petrol based fuel chain.IC engine vehicles have lower cost but higher energy consumption than the fuel cell vehicles.Hydrogen fuel chain based on SMR process (with compressed hydrogen storage and IC engine) is economically viable. However this fuel chain has higher GHG emissions.

B1)DIESEL ENGINE

ELECTRICITY

OIL MINING/REFINING

DIESEL ENGINE

GENERATOR

TRANSPORT OF DIESEL

η OM 95 %

η TD 97%

η DE 40 %

CRUDE OIL

η GEN 95 %

B2) GAS ENGINE

ELECTRICITY

EXTRACTION

GAS ENGINE

GENERATOR

NATURAL GAS TRANSPORT

η OM 95 %

η TD 97%

η DE 42 %

NATURAL GAS

η GEN 95 %

FUEL CELL (NG)NATURAL GAS

EXTRACTION

NATURAL GAS TRANSPORT

HYDROGEN

STEAM REFORMING

ELECTRICITY

PEM FUEL CELL

η R 95 %

η GT 97 %

η FC 40 % (50%)

POWER CONDITIONING

η REF 85 %

η PC 95 %

Distributed Generation

B1 Overall efficiency 35%0.246 kg of crude /kWh of electricity

B2 Overall efficiency 37%0.25 kg of Natural gas/kWh of

electricityFuel cell Overall efficiency 30% 0.307 kg

of Natural gas/kWh of electricity (37% like A2 FC eff 50%)

Carbon Emissions

B1 – Crude oil (86% Carbon) 0.211 kg Carbon/kWhB2- Natural gas (75% Carbon)0.187 kg Carbon/kWh

Fuel cell ( 18 kg of Carbon / 1 GJ of Hydrogen energy – SMR)

FC eff 0.4 - 0.171 kg Carbon/kWh0.5- 0.136 kg Carbon/kWh

Discount RateCompare investment today with expected future benefitsDiscount rate represents how money today is worth more than in the futureNo theoretically correct valueLower bound – bank interest rate

Annualised Life Cycle CostAnnualised Life Cycle Costs (ALCC) -annual cost of owning and operating equipmentALCC = C0 CRF(d,n) + AC f + AC O&M CRF (d,n) =[ d(1+d)n]/[(1+d)n-1]discount rate d, Life n years, C0 Capital Cost,AC f , AC O&M , annual cost - fuel and O&M CRF – Capital recovery factor

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