POLITECNICO DI TORINOCORSO DI LAUREA MAGISTRALE IN

INGEGNERIA ENERGETICA E NUCLEARE

Techno-economic assessment of a power-to-gas system through dynamic modelling

Francesco MangiaProf. Pierluigi LeoneProf. P. V. AravindDott. Andrea LanziniIng. Giulia Botta

30/03/2016 Francesco Mangia 2

The role of power-to-gas

Strategy steps:

1. surplus energy from a wind farm operating in the DAM

2. electrolysis of H2O and/or CO2to produce H2 and/or CO

3. production of SNG

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System configurations

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Steam electrolysis cell

Operating condition:

Tin,cath= 850°C

p = 30 bar

Vcell = 1.35 V → exothermic regime

UF = 70 %

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Co-electrolysis cell

Features:

same operating condition of the steam electrolysis case

spontaneous WGS and methanation reactions (Xu-Froment kinetics)

Aspen Plus™ steady-state validation

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Pulse current test – Co-electrolysis mode

0

2000

4000

6000

8000

10000

0 30 60 90

curr

en

t [A

]

time [s]

Pulse current

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 30 60 90

mo

lar

frac

tio

n [

-]

time [s]

Outlet cathode stream

H2

CH4

CO

CO2

H2O

fixed inlet mass flow rates

Inlet molar fractions : 0.1 H2 ; 0.037 CH4 ; 0.013 CO ; 0.16 CO2 ; 0.69 H2O

UF = 70 %

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Methanation reactor

Features:

Isothermal fluidized bed reactor

T = 400°C

p = 30 bar

feed gas module ≅ 3

Kopyscinski kinetics

Aspen Plus™ steady-state validation

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Pulse input test

SOEC in co-electrolysis mode + methanator

Feed gas module ≅ 3 when the current is applied to the SOEC

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 30 60 90

mo

lar

frac

tio

n [

-]

time [s]

Outlet cathode stream

H2

CH4

CO

CO2

H2O

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0 30 60 90

mo

lar

frac

tio

n [

-]

time [s]

Outlet reactor stream

H2

CH4

CO

CO2

H2O

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Surplus wind energy

1000 cells

Stack voltage = 135 V

0

4000

8000

12000

16000

0 372 744 1116 1488 1860 2232 2604 2976

curr

en

t [A

]

time [h]

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Sizing of the system

operating range = -50% ÷ +25% nominal current

UF = 70 % = constant

variable mass streams , ≅ constant molar compositions

Nominal stack

power [kWel]

Substack current [A]

I min I nom I max

340 125.0 250.0 312.5

770 285.7 571.4 714.3

1450 535.7 1071.4 1339.3

2800 1035.7 2071.4 2589.3

6450 2392.9 4785.7 5982.1

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Techno – economic assessmentPRESENT SCENARIO TARGET SCENARIO

Total stack cost [€/kWel] 1000 500

CO2 cost [€/ton] 89.37 4.06

GRID INJECTION TRANSPORT USE

SNG base price [c€/Nm3] 26.28 ÷ 29.98 27.89

Subsidy 25.04 ÷ 26.10 c€/Nm3 1 CIC = 10 Gcal SNG = 500 €

OTHER COSTS

Methanation unit [M€/(kg/s)] 18

H2 cost [€/kg] 3.23

Ni catalyst cost [€/kg] 22

Grid electricity [c€/kWh] 12.30

Imbalance compensation [c€/kWh] VARIABLE

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NPV analysis

0 1

Nk

kk

CFNPV

i

Results:

Yearly net cash flow < 0 → NPV < 0 ∀ SIZE, CASE and SCENARIO

NPV ∝ - 106 €

bigger systems become less competitive

target scenario and transport case are the most attractive solutions

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Advantages of co-electrolysis configuration

lower reactor feed stream → lower investment

higher yield of dried SNG → higher revenues

32.373.7

138.3

267.9

621.1

40.692.3

173.8

336.5

780.2

0

200

400

600

800

340 770 1450 2800 6450

No

min

al S

NG

pro

du

ctio

n [

Sm3/h

]

SOEC size [kWel]

steam electrolysis case co-electrolysis case

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Incentive analysis – steam electrolysis

7.68

6.81 6.68 6.81

7.91

6.57

5.68 5.51 5.60

6.51

0

2

4

6

8

340 770 1450 2800 6450

mu

ltip

lyin

g fa

cto

r gr

id in

cen

tive

Soec size [kWel]

present scenario target scenario

1997.6

1746.8 1698.8 1717.91803.8

1724.0

1467.7 1410.3 1418.01489.8

0

700

1400

2100

340 770 1450 2800 6450

CIC

val

ue

[€]

Soec size [kWel]

present scenario target scenario

0

0 6%1

Nk

kk

CFIRR

IRR

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Incentive analysis – co-electrolysis

5.74

5.08 4.95 5.04

5.85

4.88

4.20 4.04 4.09

4.76

0

2

4

6

340 770 1450 2800 6450

mu

ltip

lyin

g fa

cto

r gr

id in

cen

tive

Soec size [kWel]

present scenario target scenario

1514.6

1316.01269.8 1281.3

1344.71300.5

1096.81043.8 1046.1

1098.2

0

400

800

1200

1600

340 770 1450 2800 6450

CIC

val

ue

[€

]Soec size [kWel]

present scenario target scenario

0

0 6%1

Nk

kk

CFIRR

IRR

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Discussion of the resultsNominal stack

power [kWel]

Investment

& operating cost

production

& revenues

%En grid %En wind production

factor

% FOM land

cost

340 + + 47.7 52.3 0.28 +++ +++

770 51.4 48.6 0.22

1450 ++ ++ 56.7 43.3 0.17 ++ ++

2800 64.7 35.3 0.10

6450 +++ +++ 77.6 22.4 0.03 + +

Small system → negative impact of FOM and land cost

Big system → low production factor and %En wind

medium size is the most favorable solution

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Ad hoc subsidizing system → economic attractive solution

Co-electrolysis case and transport utilization

Preparation of a scientific paper in collaboration with TUDelft

Techno-economic assessment of a power-to-gas system through dynamic modelling

Giulia Botta, Francesco Mangia, Pierluigi Leone, P.V. Aravind

Applied Energy

Conclusions and future work

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THANKS FOR YOUR ATTENTION!