Modeling Fabrication And Optimization Of Optically Transparent Thermally Insulating Silica Aerogels For Solar Thermal Applications
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High Temperature Annealing for Structural Optimization of Silica Aerogels in Solar Thermal Applications
| Author | : Elise Strobach |
| Publisher | : |
| Total Pages | : 60 |
| Release | : 2017 |
| Genre | : |
| ISBN | : |
Optically transparent, thermally insulating monolithic silica aerogel, with its high solar transmittance and low thermal conductivity, is well-suited for solar thermal applications, particularly concentrated solar power systems. The properties of silica aerogel are directly determined by the structure of the highly porous, interconnected silica network. By using high temperature annealing to control this structure post-synthesis, we were able to optimize the material to increase solar transmittance using an easy and scalable method. The changes caused by annealing were investigated with respect to both temperature and time to relate the structural change to the optical and thermal performance change. The temperature dependent study samples were annealed for 1 hour at various temperatures ranging from 400-1000 °C. The time-dependent studies used samples made from two silica aerogel chemistries and were annealed at two temperatures (400 °C and 600 °C). In general, lower temperatures and times have less overall change (slower change rates) than higher temperature or longer time annealing. Both annealing studies indicate optical performance has an optimum with respect to annealing time, and additional temperature or time negatively affects optical properties due to appreciable structural change. After the temperature annealing studies were used to understand general trends, the time dependent studies were used to maximize the properties of aerogel for CSP applications. The samples showed an increase in solar spectral transmittance of over 3% while the effective thermal conductivity was shown to increase by as much as 40%, indicating a need to optimize the annealing time for maximum performance. The properties of the characterized aerogels were used to demonstrate aerogel annealing optimization in a concentrated solar power receiver model operating at 400 °C. The model predicted a 1% receiver efficiency increase for an operating temperature of 400 °C by annealing for 24 hours, representing a significant gain in overall system efficiency.
Translucent Silica Aerogel
| Author | : Cinzia Buratti |
| Publisher | : |
| Total Pages | : 0 |
| Release | : 2019 |
| Genre | : Aerogels |
| ISBN | : 9781536153293 |
Silica translucent aerogels are unique materials able to improve the thermal insulation performance of buildings without compromising daylight transmission. The aim of the book is to give a general overview on state of the art research on translucent aerogels and their applications in buildings and to provide a data set about thermal and physical properties, useful in buildings' energy performance simulation and design.Silica aerogels are nanostructured solid materials made of approximately 96% air and 4% silica. They show a thermal conductivity in the 0.012-0.020 W/mK range and excellent optical properties, especially visible transmission. They come in granular and monolithic form. Granular aerogels are relatively easy to produce and less expensive than monolithic panes, but show worse optical and thermal performance. Monolithic aerogels enable vision through the material, but their fabrication process is not developed at an industrial scale.The book collects the contributions of experts in the field of translucent aerogels from all over the world. The contents of the eight chapters are detailed as follows:Chapter 1 is the contribution from Union College, Schenectady (USA). The chapter reviews the chemical approaches to silica wet gels preparation, the drying methods used to yield monoliths, and the challenges and limitations associated with its production.Chapter 2 is a contribution from EMPA, Dübendorf (Switzerland). It is a review of current state of the art research on silica aerogel granulate production, including raw materials selection, hydrophobization strategies, and drying methodologies. Chapter 3 is a contribution from Takenaka Corporation, Tokyo (Japan). The main techniques for the optical properties evaluation are described and data are provided. An original application of translucent aerogels in buildings and future research topics are also proposed.Chapter 4 is a contribution from Recep Tayyip Erdogan University, Rize and Ataturk University, Erzurum (Turkey). A review of the thermal properties of aerogels is provided, highlighting their better performance when compared to conventional and superinsulation materials.Chapter 5 is a contribution from the University of Perugia, Perugia (Italy). The acoustic properties of both granular and monolithic systems are investigated. For example, the influence of granule size and layer thickness that is deepened for granular aerogels is discussed, while for the monolithic form, the little data that is currently available is reported on. Chapter 6 is a contribution from the University of Tuscia, Viterbo (Italy) and Buro Happold Ltd, London (UK). It is focused on Life Cycle Assessment of silica aerogel, showing the research challenges in understanding its environmental impact, lower than the one of conventional thermal insulating glazing systems.Chapter 7 is a contribution from the University of Lyon and INSA-Lyon, Lyon (France). An overview of measurement methods and modeling tools available in literature is provided and a summary of the main mechanical properties of both monolithic and granular aerogels is reported on.Chapter 8 is a contribution from the Norwegian University of Science and Technology, Trondheim and SINTEF, Trondheim (Norway). Authors present their experimental investigations on various aerogel systems in different building envelopes (new aerogel glass material, aerogel-incorporated concrete, and so forth).
Radiative Transport in Transparent Aerogels for Solar Thermal Energy Applications
| Author | : Lin Zhao (Ph. D.) |
| Publisher | : |
| Total Pages | : 119 |
| Release | : 2019 |
| Genre | : |
| ISBN | : |
Solar-thermal energy conversion systems hold great promise to meet our diverse energy demand by a renewable source. Converting sunlight into thermal energy requires solar radiation to be absorbed and transformed into heat effectively while minimizing system thermal loss to the ambient environment. Traditional solar-thermal systems utilize high optical concentration and vacuum enclosure to reduce the impact of heat loss. However, the cost of sophisticated optical and thermal components limits their market adoption to date. In this thesis, we explored the development of transparent aerogels for enhancing solar-thermal energy conversion. We established and validated a modeling framework to understand the fundamental light transport within an aerogel sample and yield helpful guidance for material development. We performed synthesis recipe optimization through a systematic parametric study and discovered a facile procedure to fabricate low-scattering aerogel samples with >95% solar transmittance. We then incorporated the developed aerogel in solar-thermal collectors and tested the performance. Under unconcentrated sunlight, stagnation temperature beyond 265 °C can be reached and saturated steam above 120 °C can be generated without vacuum enclosures or selective surfaces. The improvements enabled by the low-scattering aerogels promote a new pathway of solar energy utilization for domestic, industrial, and power generation applications..
Sol-Gel Science
| Author | : C. Jeffrey Brinker |
| Publisher | : Academic Press |
| Total Pages | : 925 |
| Release | : 2013-10-22 |
| Genre | : Technology & Engineering |
| ISBN | : 0080571034 |
Sol-Gel Science: The Physics and Chemistry of Sol-Gel Processing presents the physical and chemical principles of the sol-gel process. The book emphasizes the science behind sol-gel processing with a chapter devoted to applications. The first chapter introduces basic terminology, provides a brief historical sketch, and identifies some excellent texts for background reading. Chapters 2 and 3 discuss the mechanisms of hydrolysis and condensation for nonsilicate and silicate systems. Chapter 4 deals with stabilization and gelation of sols. Chapter 5 reviews theories of gelation and examines the predicted and observed changes in the properties of a sol in the vicinity of the gel point. Chapter 6 describes the changes in structure and properties that occur during aging of a gel in its pore liquor (or some other liquid). The discussion of drying is divided into two parts, with the theory concentrated in Chapter 7 and the phenomenology in Chapter 8. The structure of dried gels is explored in Chapter 9. Chapter 10 shows the possibility of using the gel as a substrate for chemical reactions or of modifying the bulk composition of the resulting ceramic by performing a surface reaction (such as nitridation) on the gel. Chapter 11 reviews the theory and practice of sintering, describing the mechanisms that govern densification of amorphous and crystalline materials, and showing the advantages of avoiding crystallization before sintering is complete. The properties of gel-derived and conventional ceramics are discussed in Chapter 12. The preparation of films is such an important aspect of sol-gel technology that the fundamentals of film formation are treated at length in Chapter 13. Films and other applications are briefly reviewed in Chapter 14. Materials scientists and researchers in the field of sol-gel processing will find the book invaluable.
Mechanical Characterization and Processing of Flexible and Transparent Ambiently-Dried Aerogels
| Author | : Ali Dashti |
| Publisher | : |
| Total Pages | : 0 |
| Release | : 2022 |
| Genre | : |
| ISBN | : |
This PhD thesis focuses on the mechanical properties and the process to synthesis novel multiscale and multifunctional mesoporous silica monoliths that are both optically transparent (not translucent) and thermally insulating to reduce energy losses through windows in commercial and residential buildings. Silica aerogels have attractive thermal insulating properties. However, conventional supercritically-dried silica aerogels are translucent due to their wide pore size distribution featuring nanopores larger than 30-40 nm resulting in a slightly blue haze. Furthermore, they are too fragile and stiff to sustain the window manufacturing process. Recent efforts have demonstrated the synthesis of ambiently-dried mesoporous silica monoliths - using sol-gel chemistry or preformed nanoparticles - with large porosity (> 70%), narrow and small pore size distribution (
Aerogels Handbook
| Author | : Michel Andre Aegerter |
| Publisher | : Springer Science & Business Media |
| Total Pages | : 929 |
| Release | : 2011-06-10 |
| Genre | : Technology & Engineering |
| ISBN | : 1441975896 |
Aerogels are the lightest solids known. Up to 1000 times lighter than glass and with a density as low as only four times that of air, they show very high thermal, electrical and acoustic insulation values and hold many entries in Guinness World Records. Originally based on silica, R&D efforts have extended this class of materials to non-silicate inorganic oxides, natural and synthetic organic polymers, carbon, metal and ceramic materials, etc. Composite systems involving polymer-crosslinked aerogels and interpenetrating hybrid networks have been developed and exhibit remarkable mechanical strength and flexibility. Even more exotic aerogels based on clays, chalcogenides, phosphides, quantum dots, and biopolymers such as chitosan are opening new applications for the construction, transportation, energy, defense and healthcare industries. Applications in electronics, chemistry, mechanics, engineering, energy production and storage, sensors, medicine, nanotechnology, military and aerospace, oil and gas recovery, thermal insulation and household uses are being developed with an estimated annual market growth rate of around 70% until 2015. The Aerogels Handbook summarizes state-of-the-art developments and processing of inorganic, organic, and composite aerogels, including the most important methods of synthesis, characterization as well as their typical applications and their possible market impact. Readers will find an exhaustive overview of all aerogel materials known today, their fabrication, upscaling aspects, physical and chemical properties, and most recent advances towards applications and commercial products, some of which are commercially available today. Key Features: •Edited and written by recognized worldwide leaders in the field •Appeals to a broad audience of materials scientists, chemists, and engineers in academic research and industrial R&D •Covers inorganic, organic, and composite aerogels •Describes military, aerospace, building industry, household, environmental, energy, and biomedical applications among others
Polarized Light in Liquid Crystals and Polymers
| Author | : Toralf Scharf |
| Publisher | : John Wiley & Sons |
| Total Pages | : 480 |
| Release | : 2007-01-02 |
| Genre | : Science |
| ISBN | : 0470074361 |
Polarized Light in Liquid Crystals and Polymers deals with the linear optics of birefringent materials, such as liquid crystals and polymers, and surveys light propagation in such media with special attention to applications. It is unique in treating light propagation in micro- and nanostructured birefringent optical elements, such as lenses and gratings composed of birefringent materials, as well as the spatial varying anisotropic structures often found in miniaturized liquid crystal devices.
Sol-Gel Optics
| Author | : Lisa C. Klein |
| Publisher | : Springer Science & Business Media |
| Total Pages | : 589 |
| Release | : 2013-11-27 |
| Genre | : Technology & Engineering |
| ISBN | : 1461527503 |
Sol--Gel--Optics encompasses numerous schemes for fabricating optical materials from gels -- materials such as bulk optics, optical waveguides, doped oxides for laser and nonlinear optics, gradient refractive index (GRIN) optics, chemical sensors, environmental sensors, and `smart' windows. Sol--Gel--Optics: Processing and Applications provides in-depth coverage of the synthesis and fabrication of these materials and discusses the optics related to microporous, amorphous, crystalline and composite materials. The reader will also find in this book detailed descriptions of new developments in silica optics, bulk optics, waveguides and thin films. Various applications to sensor and device technology are highlighted. For researchers and students looking for novel optical materials, processing methods or device ideas, Sol--Gel--Optics: Processing and Applications surveys a wide array of promising new avenues for further investigation and for innovative applications. (This book is the first in a new subseries entitled `Electronic Materials: Science and Technology).
