Nexus approach: ZSM-12 derived from industrial waste into microencapsulated in organic wax for solar energy storage system

ABSTRACT

Solar energy storage is gaining scientists interest since it could overcome the key issues affecting the solar energy efficiency. However, the lack of low-cost storage tools still signifies a formidable technological barrier. Zeolite is an answer for such requirements since it could be synthesized via the thermal decomposition of alum sludge waste. The attained ZSM-12, zeolite, was systematically characterized via X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), and Energy Dispersive X-Ray Analysis (EDX). Due to its structure, ZSM-12 is able to store solar energy for matching solar energy availability and demand. A composite of ZSM-12 integrated in paraffin wax in different mass segments subjected into a vertical-type heat exchanger (VHE) and applied as the thermal energy storage material that connected to parabolic trough solar collector (PTC). Water is the heat transfer carrier (HTC) flowing through the solar collector and the VHE in a mass flow rate of 1.83 g/s. The thermal analysis of the PTC is managed and its maximum energy achieved around the solar noon in the summer season. The new composite material displays excellent thermal performance in terms of its chemical stability and durability for melting-solidification cycles. Increasing the ZSM-12 inserted into the system up to 0.6 (wt. %) dispersion is leading to consistently good thermal properties. In addition, experimental charging/discharging data verified a minimum weight loss and simplicity of handling and operation that enhances heat transfer rate. Finally, a numerical optimization is conducted and the overall system efficiency is reached to 93%.

KEYWORDS:

• Solar energy
• ZSM-12
• thermal energy storage
• latent heat
• solar collector

Nomenclature

PCM: Phase change material

HTC: Heat Transfer Carrier

PTC: Parabolic Trough Collector

TES: Thermal Energy Storage

VHE: Vertical heat exchanger

RSM: Response surface methodology

BBD: Box-Behnken design

w: Water

T_ω: Tap water temperature (°C)

T_Ω: Charging temperature (°C)

Tς: Discharging temperature (°C)

T_α: Solar collector surface temperature (°C)

T_θ: Ambient temperature (°C)

T_β: Stored hot water temperature (°C)

T_PCM: PCM temperature (°C)

Tυ: Gained temperature (°C)

${\epsilon }_1$ : Coded T_Ω value

$E_1$ : Natural T_Ω value (°C)

${\epsilon }_2$ : Coded ZSM-12

$E_2$ : Natural ZSM-12 (%)

${\epsilon }_3$ : Coded HTC flow rate

$E_3$ : Natural HTC flow rate (g/s)

Qυ: Useful heat gained from HTC (kJ/min)

$Q_{\mathrm{P}\mathrm{C}\mathrm{M}}:$ Heat gained ZSM-12/Wax (kJ/min)

$\zeta$ : Overall efficiency of heat stored from ZSM-12/Wax (%)

Is,av: Average solar intensity radiation (W/m²)

C_w: Specific heat capacity of water (4.18 kJ/kg K) (Zelzouli et al. 2012)

$C_{\mathrm{P}\mathrm{C}\mathrm{M}}$ : Specific heat capacity of PCM (2.1 kJ/kg K) (Sharma et al. 2009)

$m_{\mathrm{P}\mathrm{C}\mathrm{M}}$ : mass of PCM

L_f: Latent heat of fusion of paraffin wax (190 kJ/kg) (Sharma et al. 2009)

$\dot{w}$ : Mass flow rate of water, HTC, (g/s)

θ: Temperature difference

Data Availability Statement

Data sharing not applicable – no new datasets were generated or analyzed during the current study.

Acknowledgments

The author is most grateful to the Water Treatment Works in Southern Shebin El-Kom City, Menoufia governorate, Egypt for providing the sludge samples used through the current study.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Notes on contributors

Maha A. Tony

Maha A. Tony Professor of Chemical Engineering (Energy and Environment specialist) Menoufia University, Egypt.