High-Temperature Heat Storage Material-Systems: Design ...–Ongoing development of 3D simulation tool - Phase change process - Coupled heat transfer and fluid flow Al12Si in steel,

Haussener – SCCER | October, 2016 1/28

High-Temperature Heat Storage Material-Systems:

Design, Stability, and Performance

aDavid Perraudin, aSelmar Binder, Ehsan Rezaia,b,

Alberto Ortonab, Sophia Haussenera

aLaboratory of Renewable Energy Sciences (LRESE),

Institute of Mechanical Engineering, EPFL

bDepartment for Innovative Technologies, ICIMSI,

Scuola universitaria professionale della Svizzera italiana (SUPSI)


• Swiss energy mix by energy usage1

820

32

9280

68

Raumwärme Warmwasser Prozesswärme

Treib/Brennstoffe, Fern/Solar/Umweltwärme Elektrizität

Prozesswärme; 12,9

Warmwasser; 6,1

Raumwärme; 28,9

Antriebe, Prozesse; 9,8

I&K, Unterhaltung; 1,3

Klima, Lüftung & Haustechnik; 2,6

Beleuchtung; 3,5sonstige; 2,6

Mobilität …

1Swiss Federal Office of Energy, Analyse des schweizerischen Energie-verbrauchs nach Verwendungszwecken, October 2015

~50% of final energy used for heating services

How?

What sectors?

~7% recycled or renewable

Motivation - Statistics

66 72

6

28 23

2

6 5

92

Raumwärme Warmwasser Prozesswärme

Haushalt Dienstleistung Industrie


• Temperature level of industrial process heat1

Motivation - Statistics

1ECOHEATCOOL, The European Heat Market, 2006


• Use of high-temperature heat in industry:

– Cement processing

– Steel processing and casting:

Source: civildigital.com

Source: ushamartin.com

Pre-calcination (850°C)

Clinkerization/kiln (850 – 1500°C)

Coke production (1200°C)

Blast furnace (1150 - 1400°C)

Casting (1400°C)

Motivation - Application


• Other applications for high-temperature heat storage:

– Electricity storage via advanced adiabatic compressed air storage

(storage temperature range 500-600 C)

– Electricity storage via concentrated solar power

(temperature range > 350 C)

Electrical

motor

Generator

Compressed

Air storage

TES

Off-Peak

Electricity

Reservoir

Heliostat fieldCold storage tankTower with receiverHot storage tankSteam generatorTurbineElectric generatorElectrical transformer

Source: Torresol

Motivation - Application


• Heat storage options

– Latent

– Sensible

– Thermochemical

– Combinations thereof

System Design – Material Choices

0

0,5

1

1,5

2

0 0,5 1 1,5 2

Δh*ρ

[J/c

m3]

c*ΔT*ρ [J/cm3]

Cu

Al

Sn

Pb

Al12Si

NaCl

Na2CO3

NaNO3ΔT=200K

NaClNa2CO3

NaNO2

stone / gravel

0,1

1

10

100

1000

0 0,5 1 1,5 2

p/e

[$

/kW

h]

Δh*ρ or cp*ΔT*ρ [J/cm3]

Cu

Al

Sn

Pb

Al12Si

NaCl

Na2CO3

NaNO3Energy density:

Cost:

(commodity)

→ Al12Si and some salts promising


• Aluminum processing:

Incorporation of high-temperature heat storage

in collaboration with SCCER-EIP: Wallerand, Prof. Marechal, EPFL

100.000

150.000

200.000

250.000

300.000

350.000

400.000

450.000

85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100

Annual OPEX

(USD)

Storage efficiency (%/h)

Reference OPEX

LHS

SHS with 650℃ LHS unit

SHS with 555℃ LHS unit

Plant size 270’000 t/y

Energy requirements: 4’503 MJ/t

Between 77% and 83% of

heat recovered → significant

reduction in input energy

requirements


Discharging:

encapsulation encapsulation

coatings coatings

• Latent heat storage: Need for encapsulation for mechanical stability

Charging:

• Metals rather than salts: Thermal conductivity, segregation, subcooling

• Problems with PCM-encapsulation for high-temperature heat storage

– Chemical stability: interface reactions, oxidation

– Mechanical stability: cyclic dis/charge conditions

– Design of system for advanced heat transfer

Challenges


• Interface characterization - System: Al12Si in steel (316L)

Exposure tests:

t1 = 8 min

time

5 d 32 d 103 d

@ 700 °C

cut

Imaging & measure

1 d

21.3 mm

Al-12.5Si

316

L

Intermetallic

after 30 days

Insight into our research – Interface degradation


• Interface characterization - System: Al12Si in steel (316L)

Exposure tests:



xx

from Yeremenko

from Torres

this study

from Amara

from Tanaka

from1

Insight into our research – Diffusion model

1Pasche, G. Interaction between liquid aluminium and solid iron . Al-rich intermetallic formation PAR. 2013, 6044.2Yan et al. Review: Durability of materials in molten aluminum alloys. J. Mater. Sci. 2001, 36, 285–295.

Cr, Ni, Si, Mn participate in the formation of intermetallic phase and slow the diffusion process2

x x

873

• K700 °C,0.5inch = 4.19*10-7 m/s0.5

• K600 °C,0.5inch = 4.05*10-7 m/s0.5

• QA,0.5inch = 2.3 kJ/mol• K0,0.5inch = 5.561*10-7 m/s0.5


• +1.26 mm Intermet.

• -0.22 mm steel• -24 vol-% PCM• Stoichiometry: 3.5

• +2.1 mm Intermet.• -0.44 mm steel• -28 vol-% PCM• Stoichiometry: 2.9700 °C, ¾ inch OD

600 °C, ½ inch OD

Insight into our research – Intermetallic evolution

700 °C, ½ inch 600 °C, ½ inch 700 °C, ¾ inch

Longest sample [days] 118 96 113

Loss PCM [vol-%] 30 24 28

Loss container wall thickness [mm] .39 .22 .44

Evolution intermetallic [mm] 1.70 1.26 2.10

• Stoichiometry: 1.9• vs. 𝐴𝑙0.62𝐹𝑒0.2𝑆𝑖0.1𝐶𝑟0.08 from SEM-EDX • vs. 5:2 from theory

700 °C, ½ inch OD

• +1.70 mm Intermet.• -0.39 mm steel• -30 vol-% PCMIn

terf

ace

po

siti

on

[m

m]

→ Reduction of PCM mass and mechanical stability

→ Strategies: change material combination or introduce diffusion barrier


• Interface characterization - System: Al in Fe

Exposure tests using neutron scattering (ISIS, Harwell):

Little to no reaction below Tm(Al) = 660°C

Reaction controlled regime in the first 20 miniron aluminide


in collaboration with Prof. Pulman, Uuniversity of Edinburgh


• Interface stabilization - System: Al12Si in steel (316L)

Stabilization of interface by diffusion barrier

Exposure tests (700 C):

Affect of layer thickness / interface on heat transfer?

t1=8 d 15 d 48 d

Cross-section:

• Al-12.5Si

• Boron nitride (BN)

• 316L steel

Assembly

Spray painting

67 d 96 d

Al-12.5Si

316L

after 30 days

Insight into our research – Interface stabilization


Insight into our research – Cyclic testing

15 cm

20

cm

T1 T2T3

15

cm

16x1mm

→ In-situ, non-destructive PCM unit performance and

stability characterization under cyclic loading

• Cycling testing / accelerated aging: tests with defined dis/charging profiles

• Cycling:

Cycle:

• An cycle was chosen to feature:

1. Homeostasis for 1 h@600 °C




• 81 cycles of 8 h duration each were recorded: 27 days of recorded data.

• 5 h above Tm x 81 cycles → 17 days


Insight into our research – Cyclic testing

Selma Binder, LRESEJuly 2015

Evaluation of thermophysical properties

10 / 15

Reduction in stabilization

duration not due to interface

reaction!

threshold

ts,onsetts,end

Reduction in stabilization

plateau of 19 %

over 81 cycles (eq. 17

days@600 °C)

• Cycling testing / accelerated aging: tests with defined dis/charging profiles


Insight into our research – Mitigation approach

At-% Fe: 2.5 (EDX)

At-% Al: 2.5 (EDX)

Al-12.8wt%Si

316L

2

1

Al-12.5Si

316L

Intermetallic

Result:• No intermetallic formation(up to 95 days or 162 charging cycles)• PCM is easily removed (recycling!)

Unprotected ePCM:

BN-Protected ePCM:

50 μm

Result:• Up to 2 mm of intermetallic layer

within 4 month Loss of 30 % PCM/capacity

• Stabilization approach successful

After 100 days at 700°C


• A processing for large-scale storage:

– Scalable process developed (based on dip-coating)

– Tube size: 32 mm inner-diameter

• Tests in large-scale tunnel at high temperature and pressure (up to 33 bars)

Heat storage capacity: 10’000 kWhth

Insight into our research – Scaled processing

pressure plug heat storage unit pressure plug compressor


• Material and component characterization by experimental-numerical

approach:

– Model development (1D cylindrical):

• Enthalpy method was used

• Melting range assumed

Insight into our research – Characterization

0

100

200

300

400

500

0

200

400

600

800

1000

1000 3000 5000

Dis

cha

rge

rate

[W

/m]

Dis

cha

rge

tim

e [s

]Heat transfer coefficient

[W/m2/s]

Bad interface:

Slower discharge


Insight into our research – Modeling

• Simulation of stored capacity per unit length:

• Simulation predicts loss in maximum capacity and output stabilization time

due to intermetallic layer

Perraudin et al., Chimica, 2015


• Enhance heat transfer by adapting architecture

– Enhance convection → high specific surface:

Porous structures: fins for enhanced heat transfer / directly filled

– Ongoing development of 3D

simulation tool

- Phase change process

- Coupled heat transfer and

fluid flow Al12Si in steel, diameter 21.3mm, wall thickness 2mm,

Laminar flow of air at 10m/s and 1000K, after 16 seconds

3.60%

3.58%

Haussener et al., JHT, 2010Suter et al., IJHMT, 2014

Insight into our research – Model-based design


Insight into our research – Foams

• Ceramic foams as encapsulation or heat transfer-enhancing fins

• Made with template method:

– Random structures:

– Regular lattices (3D printed template):


• Thermo-mechanics of SiSiC foams

Experimental assessment:

- Two different environments:

- Thermally shocked in porous burner

(group A)

- Oxidized in electric furnace with

stagnant air (group B)


Mechanical tests after exposure:

Rezaei et al., Ceramics International, 42:16255-16261, 2016

Microstructural and

compositional changes

due to oxidation and

exudation of silicon


• Thermo-mechanical analysis: Model development (ongoing)

Mechanically critical are small struts (continuum model not applicable)


°C

MPa


• Thermo-mechanical analysis: Model development and validation

Preliminary results using transport properties for the porous medium from

detailed pore-level simulations.

Solid (left) and fluid (right) phase temperatures in the center line of the porous medium for different pore nominal diameters.



• Test rig for model validation

Test rig designed and assembled to

accomplish high temperatures

measurements of heat exchange

capabilities of the tubular porous

materials.

- Temperatures (up to 1600°C)

- Pressure, mass flow sensors

- A set of thermocouples and a

pyrometer to measure

temperature in different parts.



Conclusions

• High temperature heat storage exciting field with

different challenges (performance, stability)

• Metals and alloys promising PCM, potentially

cost competitive (combined with sensible)

• Interface characterization and stabilization

central for long-term performance and cost

requirements

• Design of novel systems utilizing porous

architectures

• Thermo-mechanics challenge for such structures

0,1

1

10

100

1000

0 0,5 1 1,5 2

p/e

[$/k

Wh]

Δh*ρ or cp*ΔT*ρ [J/cm3]

Cu

Al

Sn

Pb

Al12Si


Acknowledgement

[email protected]

http://lrese.epfl.ch

Ludger Weber, EPFL

Andreas Mortensen, EPFL

Sophia Wallerand, EPFL

Francois Marechal, EPFL

Andreas Haselbacher, ETHZ

Maurizio Barbato, SUPSI

Colin Pulman, UoE

National Research Program "EnergyTurnaround" (NRP 70) of the SwissNational Science Foundation (SNSF)under Grant #153780 (www.nrp70.ch)

http://www.nrp70.ch/

Documents

High-Temperature Heat Storage Material-Systems: Design ...–Ongoing development of 3D simulation tool - Phase change process - Coupled heat transfer and fluid flow Al12Si in steel,