PROGRESS IN HIGH-TEMPERATURE ELECTROLYSIS FOR HYDROGEN PRODUCTION · PDF file · 2005-10-31PROGRESS IN HIGH-TEMPERATURE ELECTROLYSIS FOR HYDROGEN PRODUCTION Third Information Exchange

PROGRESS IN HIGH-TEMPERATURE ELECTROLYSIS FOR HYDROGEN

PRODUCTION

Third Information Exchange Meetingon the Nuclear Production of Hydrogen

Oarai, JapanOctober 6, 2005

J. Stephen HerringJames E. O’Brien, Carl M. Stoots, Grant L. Hawkes, Paul Lessing, William Windes, Daniel Wendt, Michael McKellar, Manohar Sohal (INL) and Joseph Hartvigsen (Ceramatec)

Herring NEA 3rd IEM 6Oct05 2

High temperature electrolysis using nuclear electricity and heat

• Advantages– Builds on existing Solid Oxide Fuel Cell

technology– Lower operating temperatures than

thermochemical cycles– Less corrosive operating conditions

• Disadvantages– May have lower efficiencies than

thermochemical cycles– Cells are relatively small (100 mm x 100 mm)


Theoretical Efficiency of High Temperature Electrolysis

35%

40%

45%

50%

55%

500 600 700 800 900Reactor Outlet Temperature (C)

Effic

ienc

y

Electrical generation eff.Hydrogen production eff.

P=1 atm

0

2

4

6

8

10

12

14

16

0

0.5

1

1.5

2

2.5

3

3.5

0 200 400 600 800 1000

Ener

gy D

eman

d pe

r uni

t mas

s of s

team

kWh/m3H2

T (C)

liquid steam

ΔHR, Total Energy Demand

ΔGR, Electrical Energy Demand

TΔSR, Heat Demand

MJ/kg H2O

Energy Input to Electrolyser


High Temperature Electrolysis Plant


Porous Anode, Strontium-doped Lanthanum Manganite

Gastight Electrolyte, Yttria-Stabilized Zirconia

Porous Cathode, Nickel-Zirconia cermet

2 H20 + 4 e- → 2 H2 + 2 O=

2 O= → O2 + 4 e-

2 O=

↓

H2O↓ ↑

H2

O2↓

4 e-→

0.10 mm 0.01 mm

0.05 mm 1.500 mm

0.05 mm 0.05 mm

90 v/o H2O + 10 v/o H2 10 v/o H2O + 90 v/o H2

Typical thicknessesElectrolyte- Cathode-supported supported

Interconnection

H2O + H2 →

← Ο2

1 – 2.5 mm

Next Nickel-Zirconia Cermet CathodeH2O↓

↑H2


Schematic of Stack Testing Apparatus

N2

H2 + Ar + H2O

Air + O2

H2

Air

H2O + Ar + H2

P

TTdp

Tdp

TA

V+-

Humidifier

Furnace

3-way valve

Humidifier bypass

Stack

T

T

T

T

CoolingWater

Condenser

H2 Exhaust

PowerSupply


Stack Internal Components


Metal Interconnect Details

Separator Plate, Ferritic SS, alloy 441, ~ 460 μm thickness

Air Side• Rare Earth Element Surface Treatment• Formation of low-growth-rate conductive oxide scale• Perovskite Coating (screen printing or plasma sprayed)

yields low and stable electronic resistance in air• Ferritic SS Flow Field (also surface treated)

Steam/hydrogen side• Ni metal coating on separator plate (spall

resistant)• Nickel flow field

Edge Rails• Ferritic SS, 1.02 mm

thickness• Brazed in place


22-cell stack used in July-August 2005 test


Hydrogen Production at 800° C

0

500

1000

1500

2000

0 0.05 0.1 0.15 0.2

based on stack currentbased on dewpoint measurements

H2 P

rodu

ctio

n R

ate,

sccm

current density, A/cm2

H2 Production R

ate, NL/hr

90

30

60

120

sccm N2 = 4027sccm H2 = 412T

f = 800 C

The stack continued producing102 normal liters per hour for 197 hours


22-cell stack performance, July-August 2005

0

5

10

15

20

25

30

35

0

20

40

60

80

100

120

140

0 50 100 150 200

Stac

k V

olta

ge o

r Cur

rent

Hydrogen Production R

ate, NL/hr

elapsed time, hr

H2 Production Rate

Stack Current

Stack Voltage


Overall hydrogen production efficiencies as a function of power-production thermal efficiency and electrolyzer per-cell operating voltage

0.25

0.3

0.35

0.4

0.45

0.5

0.55

0.6

0.65

0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5

ηT

Vop

0.30

0.35

0.40

0.45

ηP = 0.50

Eo

Te = 800 C

Vtn


operating voltage, V

current density, A/cm2he

atflu

x,W

/cm

2

-1.4-1.2-1-0.8-0.6-0.4

-0.3-0.2-0.100.10.20.30.4

-0.2

0

0.2

0.4

reactionohmicnet

thermal neutralvoltage

open-cellpotential

electrolysisfuel cell

Energy Budgets in fuel-cell and electrolysis modes

Stack ASR = 1.25, T = 927 C, yH2,i = 0.1, yH2,o = 0.95

FhV R

tn 2Δ−=

(1.291 V at 1200 K)


Stack and furnace temperatures during sweep

780

785

790

795

800

805

810

815

820

18 20 22 24 26 28 30 32 34

TfurnaceTair inletTinternal1Tinternal2Tinternal3Tinternal4Tinternal5

T (C)

Stack Voltage


FLUENT Single-Cell SOEC Model


Top view, showing 42 x 42 element grid

Details of 3D numerical mesh

Closeup of corner, showing vertical element stacking


FLUENT Single-Cell SOEC Model DetailsSeparator plates (Ferritic SS)• half thickness (symmetry boundary); k = 27 W/m K, σ = 8.50 x 105 Ω-1m-1

Flow Fields

• High-porosity anisotropic porous media; ε = 0.87, K1 = 2 x 10-4 m2; K2 = 2 x 10-5 m2

• Nickel metal properties (steam/hydrogen side): k = 72.0 W/m K, σ = 2.20 x 106 Ω-1m-1

• Ferritic SS properties

Steam/hydrogen electrode (Ni-YSZ cermet)

• isotropic porous media, 25 µm thickness, K = 10-13 m2, ε = 0.37, tortuosity Lt = 3.0, k= 13.1 W/m K, σ = 1.129 x 105 Ω-1m-1

YSZ electrolyte

• 2-D planar element in the FLUENT SOEC module• Ionic conductivity: ρ(T) = 3.685 x 10-4 + 2.838 x 10-5exp(10300/T(K))

Air electrode (LSM)

• isotropic porous media, 25 µm thickness, K = 10-13 m2, ε = 0.37, tortuosity Lt = 3.0, thermal conductivity k = 9.6 W/m K, and electrical conductivity σ = 7.045 x 103 Ω-1m-1


0.8

0.9

1

1.1

1.2

1.3

0.00 0.05 0.10 0.15 0.20 0.25

FLUENTExperimental

Per-

Cel

l Ope

ratin

g V

olta

ge (V

)

Current Density (A/cm2)

Voltage-current characteristics of actual electrolysis stack and FLUENT model

Electrode exchange current densities and several gap electrical contact resistances were determined empirically by comparing

FLUENT predictions with stack performance data


CFD Contour Plots

H2/H2O

Air


near thermal minimum near thermal neutral above thermal neutral

Electrolyte/insulator temperature contours0.156 A/cm2; 1.164 V 0.2344 A/cm2; 1.306 V 0.4688 A/cm2; 1.640 V

1091

1100

1104.5

1105.5 1197

1139

Electrolyte current density contours

-1404

-1878

-2097

-2734

-3892

-5158


near thermal minimum near thermal neutral above thermal neutral

Nernst Potential contours

0.156 A/cm2; 1.164 V 0.2344 A/cm2; 1.306 V 0.4688 A/cm2; 1.640 V0.910

0.847

0.932

Hydrogen mole fraction contours0.212

0.0757

0.278

0.0757

0.478

0.0759

0.8380.847

0.986

⎥⎥

⎦

⎤

⎢⎢

⎣

⎡⎟⎟⎠

⎞⎜⎜⎝

⎛⎟⎟⎠

⎞⎜⎜⎝

⎛−=

− 2/1

2/122

2lnstdOH

OHo P

Pyy

yjFRTEE


Internal Stack Components

Corroded post-test edge rail

Technical Issue: corrosion of metallic interconnect during test contributed to performance degradation and stack failure.


Inevitable Comparison:Liquid hydrocarbons are very good fuels for transportation

• Liquid over range of ambient temperatures• Pumpable: gas pump: 20 liters/min = 11 MWth

• Energy dense: 34 MJth/liter at 0.1 MPa– H2 gas: 9.9 MJth/liter at 80 MPa,– H2 120 MJth/kg, gasoline: 40 MJth/kg

• Storable: little loss, small explosion hazard• Transportable by pipeline: 0.91 m oil pipeline: 70 GWth

Hydrogen will be used primarily to enhance gasoline, diesel and jet fuel production until the on-board storageproblem can be solved.


Conclusions• Experimental results from a 22-cell stack, 64 cm2,

fabricated by Ceramatec, – Hydrogen production rates in excess of 100 NL/hr were maintained with a

22-cell solid-oxide electrolysis stack for over 196 hours over the time period from July 26 to August 3, 2005.

– The stack endurance test was terminated due to instrumentation failure (an uninterruptible power supply failed), not due to any problem with the stack itself.

– Stack performance as measured by the per-cell ASR was good, although a lower value of ASR would be desirable.

• Carbon-based liquid fuels will be dominant for decades.• Hydrogen from nuclear energy will first be used to

upgrade and synthesize feedstocks.

Documents

PROGRESS IN HIGH-TEMPERATURE ELECTROLYSIS FOR HYDROGEN PRODUCTION · PDF file · 2005-10-31PROGRESS IN HIGH-TEMPERATURE ELECTROLYSIS FOR HYDROGEN PRODUCTION Third Information Exchange