USING SOLAR ENERGY CONTINUOUSLY THROUGH DAY AND NIGHT FOR METHANE REFORMING – AN EXPERIMENTAL...

USING SOLAR ENERGY CONTINUOUSLY THROUGH DAY AND NIGHT FOR METHANE REFORMING – AN

EXPERIMENTAL DEMONSTRATION

J. L. Lapp, M. Lange, M. Roeb, C. Sattler

ECCE10 – 1701 01.10.2015

0

10

20

30

40

50

60

70

200 300 400 500 600 700 800 900

Temperature in °C

Mo

le-%

CH4

CO2CO

H2

H2O

Background on Methane Reforming

• Primary source of industrial hydrogen• Feedstock is typically natural gas

• Other possible feedstocks: biogas, refinery gas, coke oven gas

• Heat input needed at 700-900 C• Products (syngas) useful for synthesis of

other fuels (Fischer-Tropsch)• Catalyst required for kinetic reasons

04 2 2 298CH H O 3H CO 206 kj/molKH

04 2 2 298CH CO 2H 2CO 247 kj/molKH

Steam Reforming:

Dry Reforming:

2 ECCE10-1701 01 October 2015 Lapp et al.

Traditional Methane Reforming


800 °C30%

800 °C


Solar Methane Reforming


800 °C30%

42% increased output


Why use solar energy to produce chemical fuels?

1)Long term storage

2)Easy to transport

3)Compatible with current infrastructure

4)Uses in transportation


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Solar Methane Reforming Background

Directly irradiated Indirectly heated

Source: R. Tamme, 2002, SOLASYS – Final Report

+ High efficiency– High cost– Technically challenging

+ Consists of existing / simplerprocess units

Technically easy? Efficiency potential unknown

Concept first proposed in 1982 by Chubb of U.S. Naval Research Laboratory

ECCE10-1701 01 October 2015 Lapp et al.

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Indirect Experimental Studies

ASTERIX (CIEMAT/DLR, 1991)170 kW, 68-93% Conversion

DCORE (CSIRO, 2009) 200 kWSCORE (CSIRO, 1999) 25 kW

WIS, 2003, 480 kW

Sodium Vapor HTF (WIS/SNL 1983)20 kW


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Direct Experimental Studies

INHA-DISH1, 20105 kW 60% conversion

DIAPR (porcupine), WIS, 201085% conversion

Particle concept, WIS, 2009

SOLBIOPOLYSY, 2008, 250 kW, landfill gas


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CAESAR – SNL/DLR 1987 – 100kW

Solar Power (kW)

Receiver Efficiency (%)

Chemical Efficiency (%)

Methane Conversion (%)

Radially Uniform Absorber74.8 21.7 20.8 60.078.7 43.8 28.5 51.686.3 39.7 25.2 48.888.8 44.0 29.0 45.6105.7 79.3 50.7 45.9115.7 85.6 54.4 39.1Radially Non-Uniform Absorber64.1 67.3 46.3 66.072.1 65.9 44.9 68.576.9 62.7 43.6 69.597.3 68.7 45.3 52.4


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SOLASYS: DLR/WIS/Ormat, 220 kW, >90% conversion

Source: R. Tamme, 2002, SOLASYS – Final Report

4.9 bar 7.5 barMeasured CH4 Conversion 72.0% 70.5%Calculated CH4 Conversion 73.2% 65.0%


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SOLREF: DLR/WIS – 400 kW, 950 °C, 15 bar

Included novel catalytic system suitable for biogas, landfill gas, and high CO2 natural gas

94.6% Conversion


ECCE10-1701 01 October 2015 Lapp et al. 12

Theoretical Efficiency Analysis

650 700 750 800 850 900 950 1000

0.0

0.2

0.4

0.6

Eff

icie

ncy

Hot Air Temperature in °C

Overall Receiver-Reactor Process

-0.4

-0.2

0.0

0.2

Sha

re o

f el

ectr

icit

y pr

oduc

tion

650 700 750 800 850 900 950 1000

0.0

0.2

0.4

0.6E

ffic

ienc

y


Overall Receiver Process

-0.4

-0.2

0.0

0.2

Sha

re o

f el

ectr

icit

y pr

oduc

tion

Indirect Direct

650 700 750 800 850 900 950 1000

0.12

0.16

0.20

0.24

0.28

0.32

OVCR OVR TCR CVR

Pro

cess

Eff

icie

ncy


• Energy balance (flow sheet) analysis

• Directly and indirectly heated receiver concepts (separate models)

• Annual efficiency calculated with hourly irradiation data

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Direct and Indirect Concepts

Directly Irradiated Catalyst Indirectly Heated with Air HTF

Technical Difficulties Window, Catalyst-Absorber Low Heat Transfer Rate

Dynamic Behavior Fast Slow

Heat Losses Moderate High

Heat Storage Difficult Easy

Hybridization (burners) Difficult Easy

Coupling with CSP Plant Difficult Easy


Reactor: SiSiC - honeycomb structure with catalyst coating (Rh)

Contisol Project

CO + H2 Hot air

Cold air CH4 + steam + CO2


Contisol Project

Thermal StorageDaytime

Thermal StorageNighttime

Hot air to storage

Hot air from storage


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Modeling Results

Concept 3D Computational DomainApplied Heat Flux

Reactants side Air side

Daytime Operation

Nighttime Operation

Reactants side Air side


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Experimental Setup


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Experimental Setup (simplified to thermal testing)


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Experimental PreparationPorous Silicon Carbide Monolith

Infiltrated (dense)Monolith

TC’s Mounted“Canning” Mounted

Channels Closed

Monolith Sealed and Mounted


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ExperimentsGas coolers ReactorAir Preheater Radiation Shield

Reactant Preheater

Pressure Sensors


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Experiments


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ExperimentalResults

06:00:00 09:00:00 12:00:00 15:00:00 18:00:000

200

400

600

800

1000

Time

Tem

pera

ture

(°C

)

Absorber FrontAbsorber Middle

Absorber Back

Side Inlet

Side Outlet

Straight InletStraight Outlet

06:00:00 09:00:00 12:00:00 15:00:00 18:00:00-400

-200

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200

400

600

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1000

Time

T

(°C

)

Side Stream

Straight Stream

06:00:00 09:00:00 12:00:00 15:00:00 18:00:000

100

200

300

400

Time

Flo

w R

ate

(l/m

in)

Straight Inlet

Side InletStraight Outlet

Side Outlet


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Experimental Investigation• Used statistical design of experiments procedure (using Origin software)• Identified key variables

• Gas flow rate (x2)• Gas inlet temperature (x2)• Monolith front temperature

• Even with 3 values of each variable, 243 runs needed to fully describe system (full factorial)

• Optimally distributed input parameter set over 23 runs• Regression and co-variance analysis used to determine impact on efficiency of

each varible• Performance prediction of receiver fit by statistical model with R2 > 0.99

𝑇 𝑓𝑟𝑜𝑛𝑡


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Experimental Investigation Results (all CI 95%)ECCE10-1701 01 October 2015 Lapp et al.

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Experimental Investigation Results (all CI 95%)

• Flow rates are less important at high monolith temperatures (re-radiation dominates)

• Flow rates are more important to the efficiency than inlet temperatures


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Leakage Problem


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Future Advancements• 3-D printing of Inconel monolith

Test Sample, DLR, 17.09.2015


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Future Advancements• 3-D printing of Inconel monolith• Acid etching of surface required

Test Sample, DLR, 17.09.2015

Before Etching

AfterEtching


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Conclusions

• 41% upgrade of useful fuel energy with solar energy• Indirect and direct concepts• High conversion demonstrated, flexibility has not• New concept (CONTISOL) has been modeled• Thermal experiments begun• Major challenge is leakage• Will address in next steps

Thermal Storage


USING SOLAR ENERGY CONTINUOUSLY THROUGH DAY AND NIGHT FOR METHANE REFORMING – AN EXPERIMENTAL...

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