Thermochemical heat storage materials offer high-energy storage densities and clean means of long-term solar energy storage. The aim of the study is to assess the potential heat storage efficiency of salt hydrates, based on sufficient hydration/dehydration performance, water sorption and cyclicability. MgSO4•7H2O, ZnSO4•7H2O and FeSO4•7H2O were evaluate based on preselected criteria. The main highlights of the dehydration result show that higher enthalpy was obtained for MgSO4 and ZnSO4, shows 2256 J g-1 and 1731 J g-1 enthalpy, respectively. During hydration process, six water molecules were absorbing by MgSO4 and ZnSO4 after pre-dehydrated temperature 150 °C and 120 °C, respectively. The cycle stability of MgSO4 and ZnSO4 showed better performance which give rise 1210 g-1 and 1155 J g-1 enthalpy, respectively. It was expected that FeSO4 would show higher cyclicability due to their higher enthalpy (1400 J g-1) in the first round; however, overhydration does not permit it to released larger energy. The impact of relative humidity on water sorption performance and rate of hydration were reported which showed that MgSO4 and ZnSO4 can uptake maximum water under 85 and 75 % relative humidity. Ongoing studies and the booming progress of ZnSO4•7H2O illustrate that likewise MgSO4•7H2O, it is also the potential candidate and can be use in thermochemical heat storage devices. To bring zinc sulfate heptahydrate into market, more detail studies in fields of evaluation of advanced materials and development of efficient and compact prototypes are still required.
ZnSO4·7H2O is modified by impregnation method with zeolite matrices (13X-zeolite and LTA-zeolite) to improve its hydration performance. Water sorption ability of composites was carried out in a constant temperature & humidity environment. Composite of ZnSO4/13X-zeolite showed highest water sorption (0.26 g/g) at 75% relative humidity under 45 °C air temperature, which is double than pure ZnSO4·7H2O. This is due to larger surface area (491 m2 g-1) and pore volume (0.31 cm3). Based on the results, the hydration behavior of MZ9 reveals an ideal thermochemical heat storage candidate for thermal storage devices.
Table of Contents
1. Introduction
2. Material and methods
2.1. Materials
2.1.1 Composites preparation
2.2. Methods
2.2.1 Dehydration studies
2.2.2 Hydration studies
2.2.3 X-ray diffraction
2.2.4 Surface morphological and pore size
3. Result and discussion
3.1. Dehydration analysis of salts
3.2. Dehydration of MgSO4-ZnSO4 composite
3.3. Hydration of TCMs under four different temperature zone
3.4. Hydration heat of materials at various temperatures
3.5. Hydration performance of salt hydrates at relative humidity and temperature
3.6. Water Sorption performance of composites
3.7. Effect of humidity and temperature on absorption mass and rate
3.8. Structural properties of composite materials
3.8.1. Brunauer–Emmett–Teller (BET) characterization
3.8.2. X-ray diffraction (XRD)
3.9. SEM and EDX analysis of 13X pure and composites pellets
3.10. Effect of humidity and temperature on absorption performance of salt-salt composites
4. Conclusion
Research Objectives and Key Themes
This study aims to assess the potential heat storage efficiency of sulfate-based inorganic hydrous salts and their composite materials for long-term thermal energy storage, focusing on hydration/dehydration performance, water sorption capacity, and cyclic stability. The research investigates the optimal composition of salt hydrates and their modification via zeolite matrices to overcome existing technical drawbacks such as low water sorption and slow reaction rates.
- Evaluation of MgSO4, ZnSO4, and FeSO4 as thermochemical heat storage materials.
- Development of zeolite-based composites to enhance hydration performance and surface characteristics.
- Impact analysis of relative humidity and air temperature on water sorption and adsorption rates.
- Investigation of the structural properties of composite materials through XRD, SEM, and EDX analysis.
Excerpt from the Book
3.1 Dehydration analysis of salts
The dehydration results reported at every dehydration step for three different salt hydrates are commented in this section and independently presented in Fig. 5, 6 and 7 for magnesium sulfate, zinc sulfate, and iron(II) sulfate, respectively. The dehydration result was obtained using TGA–DSC at a ramp rate of 1 °C min-1, under rich N2 flow. The salt hydration state at the beginning of dehydration is deduce from the experimental mass loss. The calculated enthalpy of reaction (obtained from the formation enthalpies), the corresponding measured values, and the related energy density (that takes into account the density of the material) were also reported.
Summary of Chapters
1. Introduction: Discusses the need for thermal energy storage solutions to address the intermittency of renewable energy sources like solar power.
2. Material and methods: Details the experimental setup, preparation of salt/zeolite composites, and the diagnostic techniques used for material characterization.
3. Result and discussion: Presents the experimental findings regarding dehydration phases, cyclic performance, and the influence of environmental factors on water sorption.
4. Conclusion: Summarizes the study’s findings, highlighting the superior performance of specific composite ratios for domestic long-term heat storage.
Keywords
Salt hydrate, composites, zeolite, reusability, water sorption, thermochemical energy storage, dehydration, hydration, enthalpy, solar energy, cyclic stability, ZnSO4, MgSO4, adsorption, thermal storage.
Frequently Asked Questions
What is the primary focus of this research?
The research focuses on evaluating sulfate-based salt hydrates and their composites as candidate materials for thermochemical energy storage (TCES), aiming to improve heat storage density and cyclic stability.
What are the central thematic areas?
The themes include the material characterization of salt hydrates, the synthesis of zeolite-salt composites, and the analysis of how environmental conditions affect hydration performance.
What is the main goal or research question?
The goal is to determine the potential heat storage efficiency of various salt hydrates and to develop optimized composites that exhibit high hydration enthalpy and robust water sorption properties.
Which scientific methods were employed?
The study utilizes TGA-DSC for dehydration/hydration analysis, XRD for structural/crystallinity assessment, and SEM/EDX for morphological and elemental composition analysis.
What is covered in the main body of the work?
The work covers individual salt analysis, composite synthesis, hydration performance under varying temperature and humidity zones, and detailed characterization of physical and chemical properties.
How would you describe the work with key terms?
The work is defined by terms such as thermochemical energy storage, salt hydrates, composites, zeolite, water sorption, and cyclic stability.
Why is the ZnSO4/13X zeolite composite considered a significant advancement?
It is significant because it doubles the water sorption capacity of pure zinc sulfate heptahydrate due to its larger surface area and pore volume, allowing for more efficient heat storage.
What conclusion does the author reach regarding environmental humidity?
The author concludes that while increasing relative humidity up to 75% enhances hydration rate and water sorption, exceeding 85% RH can lead to the formation of aqueous solutions, which is detrimental to the material's performance.
- Arbeit zitieren
- Ata Ur Rehman (Autor:in), 2020, Thermochemical Heat Storage Materials and their Solar Space Heating Application, München, GRIN Verlag, https://www.hausarbeiten.de/document/584060
