Preparation Of Functionalized Form-stable Phase Change Materials And Their Applications In Solar-thermal Conversion And Storage

Solar energy is an inexhaustible source of clean and renewable energy.However,solar energy is also a quintessential time-dependent energy resource with an intermittent and discontinuous attribute,which has undermined its widespread exploitation and commercial applications.Latent heat storage(LHS)technology using organic phase change materials(PCMs)can not only effectively overcome the intermittency and instability of solar energy harvesting,but also effectively convert solar energy into heat energy and store it.Therefore,converting solar energy to thermal energy is an appealing method to mitigate the everincreasing energy shortages and improve the utilization efficiency of solar energy.Nevertheless,the possibility of the liquid leakage and inferior solar-thermal energy conversion have severely restricted the practical applications for most commonly available organic PCMs.Hence,in this work,we constructed a group of novel form-stable phase change materials(FSPCMs)with excellent sealing performance and stable solar-thermal conversion performance which realized the efficient conversion and storage of solar and thermal energy.The 3D porous medium was used as the supporting skeleton and the organic phase change material-paraffin(PW)was utilized as energy-storage units.Meanwhile,materials with the functions of sunlight capture and solar-thermal conversion were introduced.The main work is shown below:1.We successfully constructed a series of FSPCMs with stable shape and excellent solarthermal conversion performance.The PW which utilized as latent heat storage units was mixed with polynorbornene-based bottlebrush polymers(PNb22C)in a certain proportion to obtain a“gel system”,and then the S-Ni foam was introduced into the gel system as the cage and solarthermal conversion platform.The PNb22C solved the problem of paraffin leakage as gelators,and the S-Ni foams give the excellent thermal conductivity and solar-thermal conversion performance.The structure,thermal storage performance,cycle durability and photothermal conversion and storage performance of FSPCMs were measured by X-ray diffraction,Fourier infrared spectroscopy,scanning electron microscopy,differential scanning calorimetry and photothermal conversion tests.The results showed that the novel FSPCMs demonstrated no paraffin leakage,high latent heat storage capacity(172.1 J/g)and ultra-stable thermal cycling durability during the 500 times thermal cycling tests.In addition,the developed FSPCMs could energetically convert solar energy into latent heat storing by paraffin with reversible solarthermal energy storage and release during the 200 cycling tests,providing universal potential opportunities for practical applications in solar energy utilization system,etc.2.To further enhance the solar-thermal energy conversion efficiency and thermal energy storage capacity,we constructed a desirable solar-thermal energy conversion and storage system with stable shape that utilized PW as energy-storage units,the silver/polypyrrolefunctionalized polyurethane(PU)foam as the cage and energy conversion platform to restrain the fluidity of the melting paraffin during phase transition and achieve high thermal energy storage capacity(187.4 J/g)and high solar-thermal conversion efficiency(93.7 %)simultaneously.The synergistic effect of polypyrrole(PPy)as a light absorber and silver with excellent thermal conductivity solves the problem of poor thermal conductivity and solarthermal conversion performance of FSPCMs.Meanwhile,highly stable and reversible solarthermal energy conversion and storage process for the FSPCMs was also demonstrated during the 200 solar heating and natural cooling cycling tests.3.Based on work 2,we constructed a series of novel FSPCMs with solar-thermal conversion properties.The sugar granules were used as the self-sacrificial template and a 3D continuous porous solar capturer sponge derived from PB waste was proposed as supporting skeletons and high-efficiency solar-thermal conversion platform.Meanwhile the octadecylamine-functionalized reduced graphene oxide(ODA-r GO)was added as a light absorber.The prepared FSPCMs were characterized by excellent leak-proof capability and thermal stability with a heat storage capacity as high as 171.5 J/g.The solar-thermal conversion efficiency was about 92 %.More importantly,highly stable and reversible solar-thermal energy conversion and heat storage capacity for the FSPCMs were also demonstrated during the 200solar-thermal energy conversion tests.4.Based on work 1、2 and 3,FSPCMs are vulnerable to damage when suffering from the external stimulus or damage,resulting in the crack formation and a reduction in their lifespan.In order to extend the service life of FSPCMs and reduce their accumulation in the environment,we offered a dynamic hydrogen-bonding strategy to fabricate a novel class of the supramolecular phase change polymers(HOPs)with solar-thermal conversion properties using poly(4-vinylpyridine)(P4VP)as backbone,PPy as a light absorber and stearic acid(SA)as phase change side chain,which enable to self-healing upon the input of external heating or light.Meanwhile,the leakage problem of SA was solved and the self-healing of supramolecular phase change polymer was realized by introducing the dynamic hydrogen bond-driven network structure.The results showed that the HOPs were characterized by excellent shape stability and a high thermal energy storage capacity(111.5 J/g).The solar-thermal conversion efficiency was about 87.8 %.More importantly,highly stable and reversible solar-thermal energy conversion performance for the HOPs were also demonstrated during the 1000 solar-thermal energy conversion tests.On the other hand,the HOPs achieved rapid self-healing upon the input of external heating or light.