Folder: C:\Users\LRESE\Parallel\ Remark:

[#] Type[1.06] Dynamic[1.08] Dynamic[1.18] Dynamic[1.20] Dynamic

Range450/5.0(K/min)/750750/5.0(K/min)/450450/10.0(K/min)/750750/10.0(K/min)/450

Acq.Rate30.0030.0040.0040.00

STC1111

P11111

P20000

Corr.------------

Instrument:File:Project:Identity:Date/Time:Laboratory:

NETZSCH DSC 404 C190319_parallel-... .sdcPCM-TESparallel_T-DSC-119.03.2019 15:32:26LMM-LRESE

Operator:Sample:Reference:Material:Corr./Temp.Cal:Sens.File:

Selmar190319, 0.057 mgEmpty,0.000 mgAlSi12 / Cal_Ar6_50mlmin_Al2O3cruc_5Kmin_Oct2014.tdcSCal_Ar50mlmin_Al2O3pan_10Kmin_Sept2017_Svyat.edc

Sample Car./TC:Mode/Type of Meas.:Segments:Crucible:Atmosphere:M.Range:

DSC(/TG) HIGH RG 4 / SDSC / Sample20DSC/TG pan Al2O3Argon/50 / ---/---500 µV

user 2019-04-24 12:19 Main 190319_parallel-T-DSC-1.ngb

500 550 600 650 700 750Temperature /°C

-2000

-1000

0

1000

2000

DSC /(mW/mg)

Onset: 578.4 °COnset: 573.3 °C

Area: -281608 J/g

Area: -278128 J/g

End: 630.0 °C

End: 562.4 °C

Area: 7833 J/g

Area: 278149 J/g

Area: -3769 J/g

Area: 281657 J/gArea: 6170 J/g

End: 630.2 °C

End: 566.9 °C

Onset: 578.8 °COnset: 574.3 °C

[1.06][1.08][1.18][1.20]

­ exo

Thermo-analytical Characterization of Heat Storage Tank TubesFarida Amr Fawzy Hamed1, Samantha Loaiza Álvarez1, Earvin Tio1

1École Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland

Conclusions

References[1] Sharma et al., Ren. and Sus. Energy Rev 2009.[2] Leitner et al., Met. and Mat. Trans. A 2012.[3] Höhne G. et al., Springer 2011.[4] Hydrate Web Web.

Acknowledgements[5] The Engineering ToolBox Web.[6] AZO Materials Web.[7] Wei, et al., Solar Energy 2016.[8] Sun et al., Energy Conv. and Man. 2007.

LABORATORY FOR RENEWABLE ENERGY SCIENCE AND ENGINEERING

Motivation• Aluminum-12 Silicon alloy (Al12Si) is used in

this experiment because of its eutectic property. This property makes the phase transition regime narrow, which allows the material to be a good candidate to be a phase change material. This is because eutectic materials can store 5 to 14 times more heat per unit volume than non-eutectic materials [1].

• Thermal energy storage (TES) is useful for storing energy available from waste heat generated from other renewable energy sources. The stored heat can then be converted to other forms of energy at a later point.

Phase Change Material (PCM)• A substance with a high latent

heat of fusion which, when melted or solidified at a certain temperature, is capable of storing and releasing large amounts of energy

• Only the phase change between liquid and solid states is consider because other types of transitions (i.e. liquid-gas or solid-gas) experience a very high change in volume which is impractical in the case of heat storage

Overall, the metal alloy Al12Si was found to not be a suitable PCM for heat storage applications. This is mainly due to the decrease in the material’s latent heat of fusion over cycles. This means that over time and use of the heat storage application, the alloy will lose its ability to retain energy and become increasingly less efficient.

Prof. Sophia Haussener (EPFL-LRESE)Selmar Binder, PhD(c)Dr. Clemens Suter, PhD

Data Processing• Fit a unimodal spline on the

data points• Fit a line to the points

considered as baseline• Find the tangent to the curve

on the appropriate side of the peak (depending on heaOng or cooling cycle)

• Fit a line to this side• Define the onset temperature

as the intersec;on of the two lines [4]

• The enthalpy can be found by calculaOng the area under the curve (the integral)

• This was calculated by the evalua;on so>ware of the DSC machine

Melting temperature (oC)

Solidification temperature (oC)

Latent heat of fusion (kJ/kg)

Pure Al (from literature)

660.30 660.30 321.00

Al12Si (from literature) 576.00 576.00 441.00

Pure Al (measured) 665.84 665.29 435.00

Al12Si (measured) 578.95 578.69 587.15

Al12Si (top-cycled 100 times-measured)

571.77 572.53 281.61

Al12Si (center-cycled 100 times-measured)

575.71 578.23 235.50

Al12Si (bottom-cycled 100 times-measured)

573.99 578.86 353.25

ResultsData extracted from the DSC curves for each sample and from literature [5], [6], [7]

Observations1. Melting temperature is higher than the

solidification temperature2. Melting temperature of pure aluminum is

higher than the melting temperature of the aluminum alloy Al12Si

3. Cycling slightly decreases the melting temperature of the material

4. The latent heat of fusion decreases after 100 cycles [8]

5. The measured melting temperatures of the reference pure aluminum and the aluminum alloy are 0.84% and 0.51% higher respectively than their literature values

Limits1. The small number of samples that were considered (only one sample was used) 2. The small number of cycles considered, the average value of the measured sample was

calculated using only two cycles. 3. PCMs have very high melOng points and low thermal conducOvity, thus mistakes in sample

preparaOon (geometry and weight) affect the results

Enthalpy curve of pure aluminum [2]

6. Onset temperatures are not dependent on heating rate

7. Higher heating rates result in higher peaks and end melting temperatures due to the thermal reaction constraints of the material and its geometry

8. The area under the curve (i.e. latent heat of fusion) remains the same, regardless of heating rate

Differential Scanning Calorimetry (DSC)

A thermal analysis technique that measures the energy absorbed or emitted by a sample and a reference as a function of temperature [3].

• Where the temperature is increased/decreased linearly and the reference sample has a defined heat capacity across the range of scanned temperatures.

• Where the temperature range and the heating rate are defined based on the chemical (e.g. melting point) and physical properties (e.g. weight) of the sample.

Units in millimeters (mm)

Magnified polished metallographic cross-secOon

Sample Preparation

The single PCM tube sample was cut into three subsecOons, with a smaller porOon separated from each subsecOon. The magnified image on the le^ is of the smaller porOon of the top subsecOon.