Thermal energy storage enhancement of dispersing

nanoparticles in a phase change material

Afrah Awad*1,2, Prof. Dongsheng Wen1

1 School of Chemical and process Engineering, University of Leeds, Leeds, UK. 2 School of Mechanical Engineering, University of Leeds, Leeds, UK, and sponsored by The Higher

Committee for Education Development in Iraq (HCED).

* Corresponding email: mnata@leeds.ac.uk

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Solar energy Concentrated solar

thermal power plants types

Solar thermal energy storage system

Dispersing nanoparticles in the storage medium

Results of sensible and latent heat enhancement

of nanosalt Conclusion

Outline:

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In 2014, CO2 emissions grew by about 0.5% (Petroleum,

2015, p.3)

Global warming

Due to that, green energy has become essential in tackling these problems (Tsoutsos et al., 2005; Yun and Lee, 2015).

(AP, 2015)

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4

(Lasfargues, 2014)

Concentrated solar thermal power plants types

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(nrel, 2016) SolarReserve’s Crescent Dunes CSP Project, near Tonopah, Nevada, has an

electricity generating capacity of 110 megawatts. (credit: SolarReserve)

(nrel, 2016) These dish/Stirling units are being tested at Sandia National Laboratories in

Albuquerque, New Mexico. Credit: Stirling Energy Systems

(nrel, 2016) These receivers and mirrors are part of Ausra's Kimberlina solar

thermal power plant, a linear Fresnel reflector system located near Bakersfield, California. Credit: Ausra

(nrel, 2016) Project Name: Solar Electric Generating Station III (SEGS III)

Country: United States Solar-Field Outlet Temp: 349°C

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Parabolic trough plant

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Storage system is missing ?!

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(Lasfargues, 2014)

The classifications of the storage system

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1. Thermocline storage system

(Lasfargues, 2014)

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2. Direct tank

(Lasfargues, 2014) 11

(Lasfargues, 2014)

3. In-direct tank

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4. DSG

(Feldhoff, F. 2012) 112 bar & 500 C

78 bar & 294.144 C 13

DSG without storage TSE-1, Thailand 5 MWe 34 bar, 340 °C Technology by Solarlite

(Feldhoff, F. 2012)

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The material used in storage system need to have the following requirements: 1. Stability, repeated thermal cycling.

2. Compatibility with other materials.

3. Safe, non-flammable and nontoxic.

4. High cp & K (Mehling and Cabeza, 2008).

5. Economically.

Nanoparticles added to enhance the PCM properties

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CRITERIA OF CHOOSING NANOPARTICLES RECIPE

Nanoparticles shape and size.

Mechanical and thermal

properties.

Which property, we are looking for. Cost Availability

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CuO nanoparticles with average diameter <50 nm and MWCNT with [O.D. × I.D. × L (10

nm × 4.5 nm × 4 μm)] purchased from Sigma Aldrich Company. Salt type is NaNO3

(FISHER, Loughborough, UK) with 98% purity.

Material used for this experiment

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Device used during the preparation of samples

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Balance during the preparation of the sample

Balance accuracy

Samples’ weighting Samples’ mixing

Probe sonicate Hot plate

Water evaporation

PREPARATION OF NANOSALT

Mixing distilled water + nanoparticles

Sonication

Add salt to mixture

Sonication

Evaporation

Distilled water of 25 ml, Second sonication was after 24 hours

Evaporation- hot plate- 150 ˚C

Each prepared sample have weight of NaNO3 salt of 198 mg

with the concentrations of the nanoparticles as 0.5 and 1 wt.

%.

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DSC- Mettler Toledo

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Ultra-microbalance Mettler Toledo Max. 2.1 g and precision of 0.1 µg

TEM device

TEM device has been used to check the size of nanoparticles purchased and below are the results got:

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CuO nanoparticles MWCNT

Specific heat capacity measurement using DSC with standard error less than 0.01

Specific heat capacity of solid phase of NaNO3 without and with 0.5 wt.% and 1 wt. % of CuO and

MWCNT.

Specific heat capacity of liquid phase of NaNO3 without and with 0.5 wt.% and 1 wt. % of CuO and

MWCNT.

Mettler Toledo DSC (DSC1, Mettler Toledo, Leicester, UK)

The heating method used is modelled at a rate of 150 ˚C for 10 min then ramped from 150 ˚C to 450 ˚C at a rate of 10 ˚C/min then maintained isothermally for 10 min at 450 C finally cooled down from 450 ˚C to 150 ˚C at -40 ˚C/min

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150 165 180 195 210 225 240 255 2701.0

1.5

2.0

2.5

3.0

NaNO3

NaNO3+ 0.5 wt.% CuONaNO3+ 1 wt.% CuO NaNO3+ 0.5 wt.% MWCNT NaNO3+ 1 wt.% MWCNT

Spec

ific

heat

cap

acity

, J/(g

. 0 C)

Temperature, 0C

330 345 360 375 390 405 420 4351.0

1.5

2.0

2.5

3.0 NaNO3

NaNO3+ 0.5 wt.% CuO NaNO3+ 1 wt.% CuO NaNO3+ 0.5 wt.% MWCNT NaNO3+ 1 wt.% MWCNT

Spec

ific

heat

cap

acity

, J/ (

g. 0 C

)Temperature, 0C

0.5 wt.% CuO-NaNO3 salt NaNO3 salt

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1 wt.% CuO-NaNO3 salt

0.5 wt.% MWCNT-NaNO3 salt 1 wt.% MWCNT-NaNO3 salt

Checking the repeatability of the samples by running each one for 3 times

Latent heat and onset temperature of nanosalt

Latent heat measured in good agreement with the literature (Tamme et al., 2003).

Material Latent heat

(kJ/kg)

Onset

temperature (oC) ΔTonset Total TES capacity

(kJ/kg)

% increases in Total

TES capacity

Pure salt (NaNO3) 173.78 304.68 0 495.31 -

Salt + 0.5 wt % CuO 188.93 303.3 1.38 529.16 6.83%

Salt + 1 wt % CuO 182.61 302.09 2.59 504.14 1.78%

Salt + 0.5 wt % MWCNT 167.21 295.65 9.03 475.21 -4.06%

Salt + 1 wt % MWCNT 165.18 291.82 12.86 504.64 1.88%

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Highest increases in latent heat by 8.72%

Scanning Electron Microscopy (SEM) results

SEM of 0.5 wt. % CuO - NaNO3

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SEM of NaNO3 SEM of 1 wt. % CuO - NaNO3 SEM of 1 wt. % CuO - NaNO3

SEM of 0.5 wt. % MWCNT - NaNO3 SEM of 0.5 wt. % MWCNT - NaNO3 SEM of 1 wt. % MWCNT - NaNO3 SEM of 1 wt. % MWCNT - NaNO3

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Agglomerations of nanoparticles in nanosalt with 0.5 wt.% CuO

CONCLUSIONS

Based on the sensible heat and latent heat investigations, the nanoparticles

addition have power to increase the storage heat.

For both sensible and latent heat improvements, CuO nanoparticles show lower

concentration is better in contrast to MWCNT case.

Latent heat of 0.5 wt.% CuO-salt increases by 11.5% higher than 0.5 wt.%

MWCNT-salt.

Latent heat of 1 wt.% CuO-salt increases by 10.6% higher than 1 wt.% MWCNT-

salt.

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