近年來，再生能源被視為取代石化燃料的替代能源，而其中太陽熱能儲存系統由於其能源可分配性、無毒性以及取之不盡的特性被視為十分有潛力有未來展望的能源技術。而為了要彌補在熱儲存系統中融熔鹽工作流體熱儲存能力的不足，經過研究發現參雜粒子加入工作流體中這個方法可以有效地增加工作流體的儲熱能力。有著高潛熱的核與高度保護性的殼形成的封裝相變化材料能夠有效的添加至工作流體中因此成為了近年來一大熱門研究主題。

在此研究中，我們不僅成功地將非晶型碳包覆在錫微米粒子上，並成功的利用不同的冷卻速率形成了蛋黃-殼結構，蛋黃殼結構為一種特殊的核殼結構，它具有一層空隙形成在殼與核的中間，這層空隙能夠作為在相變化時相變化材料體積膨脹的緩衝層。同時藉由材料特性分析我們可以確認構造以及其厚度。除此之外，我們還藉由循環測試來證明相變化材料在加熱與冷卻的循環中保持穩定的結構。在實驗與理論值上我們研究了殼層變化、成核能障與加熱速率對於相變化與熱遲滯溫度的影響，實驗結果與理論值有著相近的趨勢。另外我們引進了合金來降低熔點溫度尋求更低的熱遲滯溫度，有著更低的工作溫度與熱遲滯溫度，我們能有更廣闊的儲熱應用。此外就由添加不同重量比例的核殼相變化材料至工作流體，儲熱容量的提升與黏度的關係也被深入探討，也額外結合了殼的吸收光轉熱能力來證明材料確實有潛力應用於太陽能熱系統中。

Renewable energy has been considered as the solution of alternative energy source of fossil fuels, and solar thermal energy storage is one of the promising technique due to its dispatchable, non-toxic and unexhausted characterization. In order to increase the thermal storage ability of molten salt working in thermal storage system, dispersion of particles into molten salt have been suggested as an effective method. Encapsulated PCMs have high latent heat core and protective shell so that it became hot topic.

In this study, we not only use Sn as core material and carbon as protective shell but synthesize yolk shell structure, which is structure composed of core@void @shell. This structure could act as a buffer space to the volume expansion during phase transition. From the SEM and FIB, we could confirm the structure and thickness. Besides, DSC cycling test verified the stability of Sn/a-C particles. We also check the experimental and predicted thermal hysteresis by changing shell thickness, ramping rate and nucleation effect. Moreover, we successfully synthesize the Sn/Bi alloy with melting point at 142oC and keep 122oC crystallization peak meanwhile. With lowering thermal hysteresis, we could have wide application in thermal storage. The heat capacity enhancement in molten salt and viscosity were also measured by doping different weight percent particles into it. At last, the solar-driven thermal effect of shell was carried out to comfirm this particles have deep potential on solar thermal applications.

摘要 I
Abstract II
致謝 III
Contents IV
List of Figure VI
Table List IX
Chapter 1 Introduction 1
1.1 Overview of Renewable Energy 1
1.2 Importance of Thermal Energy Utilization 4
1.3 Solar Energy & Solar Thermal Energy 6
1.4 Introduction to Solar Thermal Power Plants 11
1.5 Molten Salt 16
1.6 Phase Change Materials 18
1.7 Solar-Driven thermal Effect 24
Chapter 2 Experimental Procedures 26
2.1 Chemicals 26
2.2 Synthesis of Sn/ Carbon micro particles 27
2.2.1 Synthesis of Sn/ amorphous Carbon (a-C) micro particles 27
2.2.2 Synthesis of Sn/a-C/r-GO micro particles 29
2.3 Synthesis of SnBi/a-C core-shell microparticles 30
2.3.1 Synthesis of SnBi alloy particles 30
2.3.2 Carbon coating of SnBi microparticles 31
2.4 Analytical Characterization Equipment 32
2.4.1 Scanning Electron Microscope (SEM) 32
2.4.2 X-Ray Diffraction (XRD) 33
2.4.3 Focused Ion Beam (FIB) 34
2.4.4 Energy Dispersive Spectrometer (EDX) 36
2.4.5 Differential Scanning Calorimeter (DSC) 38
2.4.6 Viscometer 40
2.4.7 Raman Spectroscopy 42
Chapter 3 Result and Discussions 43
3.1 Motivation 43
3.2. Coating Quality of Core-shell Microparticles 45
3.2.1 Morphology and Cross Section analysis 45
3.2.2 Element analysis of Sn/a-C microparticles 49
3.2.3 Effect of pH value on Dopamine Polymerization 51
3.3 Thickness control of Sn/a-C microparticles 52
3.4 Thermal stability test 56
3.5 Thermal Hysteresis Performance 59
3.6 Use Alloy to Decrease Melting Temperature 66
3.7 Thermal application 70
Chapter 4 Summary & Conclusions 73
Reference 74

[1] F. Ruzzenenti and A. A. Papandreou, "On the effects of fossil fuel prices on the transition towards a low carbon energy system," 2015.
[2] U. S. E. I. Administration. (2017). U.S. energy consumption rose slightly in 2016 despite a significant decline in coal use.
[3] I. R. E. Agency. (2018). Global Renewable Generation Continues its Strong Growth, New IRENA Capacity Data Shows.
[4] LLNL. (2017). Energy Flow Charts 2017.
[5] H. Jouhara et al., "Waste heat recovery technologies and applications," 2018.
[6] H. Teng, G. Regner, and C. Cowland, "Waste heat recovery of heavy-duty diesel engines by organic Rankine cycle part I: hybrid energy system of diesel and Rankine engines," SAE Technical Paper0148-7191, 2007.
[7] S. D. Burch, T. F. Potter, M. A. Keyser, M. J. Brady, and K. F. J. S. t. Michaels, "Reducing cold-start emissions by catalytic converter thermal management," pp. 348-353, 1995.
[8] S. D. Burch, M. A. Keyser, C. P. Colucci, T. F. Potter, D. K. Benson, and J. P. Biel, "Applications and benefits of catalytic converter thermal management," SAE technical paper0148-7191, 1996.
[9] Wiki. (2018). Solar energy.
[10] O. Morton, "A new day dawning?: Silicon Valley sunrise," Nature, vol. 443, p. 19, 09/06/online 2006.
[11] P. M. Salunke, H. B. Kulkarni, A. M. Waghchavare, and S. S. Kurle, "Solar Energy and its Applications-Need, Overview and Future Scope."
[12] S. F. P. H. Lt. (2018). Smart-Flo Ltd Solar Thermal.
[13] IECEC. How Solar Panels Work and What They Cost.
[14] M. A. Green, Y. Hishikawa, E. D. Dunlop, D. H. Levi, J. Hohl-Ebinger, and A. W. J. P. i. P. Ho-Baillie, "Solar cell efficiency tables (version 52)," vol. 26, no. 7, 2018.
[15] C. W. Forsberg, P. F. Peterson, and H. Zhao, "High-Temperature Liquid-Fluoride-Salt Closed-Brayton-Cycle Solar Power Towers," Journal of Solar Energy Engineering, vol. 129, no. 2, pp. 141-146, 2006.
[16] G. Brinkman et al., "Grid modeling for the SunShot vision study," vol. 303, pp. 275-3000, 2012.
[17] Z. Ma, M. Mehos, G. Glatzmaier, and B. J. E. P. Sakadjian, "Development of a concentrating solar power system using fluidized-bed technology for thermal energy conversion and solid particles for thermal energy storage," vol. 69, no. NREL/JA-5500-62799, 2015.
[18] M. Romero, A. J. E. Steinfeld, and E. Science, "Concentrating solar thermal power and thermochemical fuels," vol. 5, no. 11, pp. 9234-9245, 2012.
[19] J. Frenzel, "Concentrated Solar Thermal Power plants: The future of power supply in Europe," MSc. Thesis, Ritsumeikan Asia Pacific University, 2011.
[20] J. I. Burgaleta, S. Arias, and D. J. S. Ramirez, Granada, Spain, "Gemasolar, the first tower thermosolar commercial plant with molten salt storage," pp. 20-23, 2011.
[21] H. Zhang, J. Baeyens, J. Degrève, G. J. R. Cacères, and s. e. reviews, "Concentrated solar power plants: Review and design methodology," vol. 22, pp. 466-481, 2013.
[22] O. Behar, A. Khellaf, K. J. R. Mohammedi, and s. e. reviews, "A review of studies on central receiver solar thermal power plants," vol. 23, pp. 12-39, 2013.
[23] Y. Tian and C.-Y. J. A. e. Zhao, "A review of solar collectors and thermal energy storage in solar thermal applications," vol. 104, pp. 538-553, 2013.
[24] SolarPACES. (2017). CSP Projects Around the World-SolarPACES.
[25] Z. Yang and S. V. J. S. e. Garimella, "Thermal analysis of solar thermal energy storage in a molten-salt thermocline," vol. 84, no. 6, pp. 974-985, 2010.
[26] C. W. Forsberg, P. F. Peterson, and P. S. J. N. T. Pickard, "Molten-salt-cooled advanced high-temperature reactor for production of hydrogen and electricity," vol. 144, no. 3, pp. 289-302, 2003.
[27] D. E. Holcomb, G. F. Flanagan, G. T. Mays, W. D. Pointer, K. R. Robb, and G. L. J. O. T.-. Yoder Jr, ORNL, Oak Ridge, TN, "Fluoride salt-cooled high-temperature reactor technology development and demonstration roadmap," 2013.
[28] M. M. J. R. Kenisarin and S. e. reviews, "High-temperature phase change materials for thermal energy storage," vol. 14, no. 3, pp. 955-970, 2010.
[29] D. Kearney et al., "Overview on use of a Molten Salt HTF in a Trough Solar Field," in NREL Parabolic Trough Thermal Energy Storage Workshop, 2003.
[30] A. G.-F. Nuria Navarrete, Rosa Mondragon, Leonor Hernandez, Luis Cabedo, Eloisa Cordoncillo & J. Enrique Julia, "Nanofluid based on selfnanoencapsulated metal/metal alloys phase change materials with tuneable crystallisation temperature," Sci Rep, 2017.
[31] C. Amaral, R. Vicente, P. Marques, A. J. R. Barros-Timmons, and S. E. Reviews, "Phase change materials and carbon nanostructures for thermal energy storage: A literature review," vol. 79, pp. 1212-1228, 2017.
[32] C.-C. Lai, S.-M. Lin, Y.-D. Chu, C.-C. Chang, Y.-L. Chueh, and M.-C. J. N. E. Lu, "Tunable endothermic plateau for enhancing thermal energy storage obtained using binary metal alloy particles," vol. 25, pp. 218-224, 2016.
[33] C.-C. Lai, W.-C. Chang, W.-L. Hu, Z. M. Wang, M.-C. Lu, and Y.-L. J. N. Chueh, "A solar-thermal energy harvesting scheme: enhanced heat capacity of molten HITEC salt mixed with Sn/SiO x core–shell nanoparticles," vol. 6, no. 9, pp. 4555-4559, 2014.
[34] S. Cingarapu, D. Singh, E. V. Timofeeva, and M. R. J. R. E. Moravek, "Use of encapsulated zinc particles in a eutectic chloride salt to enhance thermal energy storage capacity for concentrated solar power," vol. 80, pp. 508-516, 2015.
[35] M. H. M. Isa, X. Zhao, and H. J. S. Yoshino, "Preliminary study of passive cooling strategy using a combination of PCM and copper foam to increase thermal heat storage in building facade," vol. 2, no. 8, pp. 2365-2381, 2010.
[36] W. Su, J. Darkwa, G. J. R. Kokogiannakis, and S. E. Reviews, "Review of solid–liquid phase change materials and their encapsulation technologies," vol. 48, pp. 373-391, 2015.
[37] L. F. Cabeza, A. Castell, C. d. Barreneche, A. De Gracia, A. J. R. Fernández, and S. E. Reviews, "Materials used as PCM in thermal energy storage in buildings: a review," vol. 15, no. 3, pp. 1675-1695, 2011.
[38] Y. Hong et al., "Enhancing Heat Capacity of Colloidal Suspension Using Nanoscale Encapsulated Phase-Change Materials for Heat Transfer," (in English), Acs Applied Materials & Interfaces, vol. 2, no. 6, pp. 1685-1691, Jun 2010.
[39] S. Cingarapu, D. Singh, E. V. Timofeeva, and M. R. Moravek, "Nanofluids with encapsulated tin nanoparticles for advanced heat transfer and thermal energy storage," (in English), International Journal of Energy Research, vol. 38, no. 1, pp. 51-59, Jan 2014.
[40] T. Nomura, C. Zhu, N. Sheng, G. Saito, and T. Akiyama, "Microencapsulation of metal-based phase change material for high-temperature thermal energy storage," Sci Rep, vol. 5, p. 9117, Mar 13 2015.
[41] T. Nomura et al., "Microencapsulated phase change materials with high heat capacity and high cyclic durability for high-temperature thermal energy storage and transportation," (in English), Applied Energy, vol. 188, pp. 9-18, Feb 15 2017.
[42] J. Y. T Nomura, N Sheng, H Sakai, Y Hasegawa, "Microencapsulation of eutectic and hyper-eutectic Al-Si alloy as phase change materials for high-temperature thermal energy storage," 2018.
[43] T. H. Hsu, C. H. Chung, F. J. Chung, C. C. Chang, M. C. Lu, and Y. L. Chueh, "Thermal hysteresis in phase-change materials: Encapsulated metal alloy core-shell microparticles," (in English), Nano Energy, vol. 51, pp. 563-570, Sep 2018.
[44] H. J. TD Dao, "Novel stearic acid/graphene core–shell composite microcapsule as a phase change material exhibiting high shape stability and performance," Solar Energy Materials and Solar Cells
vol. 137, 2015.
[45] H. J. TD Dao, "A Pickering emulsion route to a stearic acid/graphene core–shell composite phase change material," Carbon, vol. 99, pp. 49-57, 2016.
[46] J. Wang et al., "High-Performance Photothermal Conversion of Narrow-Bandgap Ti2 O3 Nanoparticles," Adv Mater, vol. 29, no. 3, Jan 2017.
[47] K. J. Yuan, H. C. Wang, J. Liu, X. M. Fang, and Z. G. Zhang, "Novel slurry containing graphene oxide-grafted microencapsulated phase change material with enhanced thermo-physical properties and photo-thermal performance," (in English), Solar Energy Materials and Solar Cells, vol. 143, pp. 29-37, Dec 2015.
[48] Y. F. Chen, Q. Zhang, X. Y. Wen, H. B. Yin, and J. Liu, "A novel CNT encapsulated phase change material with enhanced thermal conductivity and photo-thermal conversion performance," (in English), Solar Energy Materials and Solar Cells, vol. 184, pp. 82-90, Sep 2018.
[49] Y. X. J Zeng, H Duan, "Tin-silica-silver composite nanoparticles for medium-to-high temperature volumetric absorption solar collectors," vol. 157, pp. 930-936, 2016.
[50] J. X. J. Z. C. A. Wang, "Carbon encapsulated Fe3O4 nanospheres with high electrochemical performance as anode materials for Li‐ion battery," Journal of Applied Ceramic Technology vol. 14, pp. 938-947, 2017.
[51] X. Yu, H. Fan, Y. Liu, Z. Shi, and Z. Jin, "Characterization of carbonized polydopamine nanoparticles suggests ordered supramolecular structure of polydopamine," Langmuir, vol. 30, no. 19, pp. 5497-505, May 20 2014.
[52] 冯. 刘. 赵. 陈建峰, "多巴胺改性BaTiO3对BaTiO3/PVDF复合材料击穿场强的影响," 2015.
[53] C. M. Lin et al., "Bio-inspired fabrication of core@shell structured TATB/polydopamine microparticles via in situ polymerization with tunable mechanical properties," (in English), Polymer Testing, vol. 68, pp. 126-134, Jul 2018.
[54] X. M. Kang, W. H. Cai, S. Zhang, and S. X. Cui, "Revealing the formation mechanism of insoluble polydopamine by using a simplified model system," (in English), Polymer Chemistry, vol. 8, no. 5, pp. 860-864, Feb 7 2017.
[55] Y. Z. Chen et al., "Low Temperature Growth of Graphene on Glass by Carbon-Enclosed Chemical Vapor Deposition Process and Its Application as Transparent Electrode," (in English), Chemistry of Materials, vol. 27, no. 5, pp. 1646-1655, Mar 10 2015.
[56] M. A. C.-L. A. J. Salazar-Pérez, R. A. Morales-Luckie, V. Sánchez-Mendieta, F. Ureña-Núñez, J. Arenas-Alatorre, "Structural evolution of Bi2O3 prepared by thermal oxidation of bismuth nano-particles " 2005.
[57] M. Sezen, "Focused Ion Beams (FIB)—Novel Methodologies and Recent Applications for Multidisciplinary Sciences," 2016.
[58] M. Klimenkov, R. Lindau, and A. Moslang, "New insights into the structure of ODS particles in the ODS-Eurofer alloy," (in English), Journal of Nuclear Materials, vol. 386-88, pp. 553-556, Apr 30 2009.
[59] J. Goldstein, et al, "Scanning electron microscopy and X-ray microanalysis. A text for biologists, material scientists and geologists," 1983.
[60] J. O'neill Michael, "Differential microcalorimeter," Google Patents., 1966.
[61] W. Steinmann, et al, "Thermal analysis of phase transitions and crystallization in polymeric fibers,": INTECH Open Access Publisher, 2013

[62] L. C. Thomas, "Use Of Quasi-isothermal Mode for Improved Understanding of Structure Change," 2005.
[63] C. Sherman, "More Solutions to Sticky Problems. Brookfield Viscometer Guide. Brookfield Engineering Laboratories," Inc.. Stoughton, Boston, MA., USA, pp. 1-7, 1994.
[64] K. Li et al., "A yolk/shell strategy for designing hybrid phase change materials for heat management in catalytic reactions," Journal of Materials Chemistry A, vol. 5, no. 46, pp. 24232-24246, 2017.