Smart window photovoltaic concentrator for energy generation and solar control

Central to the global mission on reducing societies carbon footprint is the commitment of governments and international institutions to set energy reduction targets. In this regard, buildings are responsible for large energy loads. Due to the necessity to create thermal and visual comfort, vast energy is consumed to satisfy internal cooling, heating, and lighting loads. The two main strategies to reduce buildings energy consumption are renewable energy technologies and energy efficient building planning. Building Integrated PV systems (BIPV) are devices capable to generate electricity while replacing building materials and reduce electricity costs, protect the building from weather acting as a building envelope and offering aesthetically pleasing features to the building. Windows play key role in the building energy consumption allowing for sunlight and heat to enter the building. Some commercial technologies offer solar control functions using reversible photochromic, thermochromic or electrochromic mechanisms. However, only few offer an automated system able to respond to dynamic changes of the environment while producing onsite energy. The research presented in this thesis covers the details of the design and development of a novel lightweight solar concentrator for “smart window” applications. The smart window design was conceived to automatically control the solar radiation entering buildings and generate clean electricity at the same time, thus compensating artificial lighting, cooling, and heating loads. To achieve the dual functionality of the smart window two novel thermotropic membranes were developed and characterised using two gelling agents and 3 polymers. Transmittance levels of 95% in clear state and 40% when in light scattering state were achieved. A ray tracing model was validated against experimental indoor tests with 8% deviation. Indoor tests comparing between 2% wt. HPC & 1.5 % wt. GGF and 6% wt. HPC & 1.5 % wt. GGF membranes reported efficiency values of 3.7% and 5.1% and MPP values of 0.018W and 0.024W, respectively. Outdoor tests showed that the automated solar control function allows sunlight to pass through the smart window during the morning and the evening hours but block the sun when irradiation levels surpass 600 W/m2. The study concludes, however, that in order to produce a more efficient device the membrane reflectivity of the smart window should be close to 90%

Smart window photovoltaic concentrator for energy generation and solar control

Central to the global mission on reducing societies carbon footprint is the commitment of governments and international institutions to set energy reduction targets. In this regard, buildings are responsible for large energy loads. Due to the necessity to create thermal and visual comfort, vast energy is consumed to satisfy internal cooling, heating, and lighting loads. The two main strategies to reduce buildings energy consumption are renewable energy technologies and energy efficient building planning. Building Integrated PV systems (BIPV) are devices capable to generate electricity while replacing building materials and reduce electricity costs, protect the building from weather acting as a building envelope and offering aesthetically pleasing features to the building. Windows play key role in the building energy consumption allowing for sunlight and heat to enter the building. Some commercial technologies offer solar control functions using reversible photochromic, thermochromic or electrochromic mechanisms. However, only few offer an automated system able to respond to dynamic changes of the environment while producing onsite energy. The research presented in this thesis covers the details of the design and development of a novel lightweight solar concentrator for “smart window” applications. The smart window design was conceived to automatically control the solar radiation entering buildings and generate clean electricity at the same time, thus compensating artificial lighting, cooling, and heating loads. To achieve the dual functionality of the smart window two novel thermotropic membranes were developed and characterised using two gelling agents and 3 polymers. Transmittance levels of 95% in clear state and 40% when in light scattering state were achieved. A ray tracing model was validated against experimental indoor tests with 8% deviation. Indoor tests comparing between 2% wt. HPC & 1.5 % wt. GGF and 6% wt. HPC & 1.5 % wt. GGF membranes reported efficiency values of 3.7% and 5.1% and MPP values of 0.018W and 0.024W, respectively. Outdoor tests showed that the automated solar control function allows sunlight to pass through the smart window during the morning and the evening hours but block the sun when irradiation levels surpass 600 W/m2. The study concludes, however, that in order to produce a more efficient device the membrane reflectivity of the smart window should be close to 90%

Diffusion of tin from TEC-8 conductive glass into mesoporous titanium dioxide in dye sensitized solar cells

The photoanode of a dye sensitized solar cell is typically a mesoporous titanium dioxide thin film adhered to a conductive glass plate. In the case of TEC-8 glass, an approximately 500 nm film of tin oxide provides the conductivity of this substrate. During the calcining step of photoanode fabrication, tin diffuses into the titanium dioxide layer. Scanning Electron Microscopy and Electron Dispersion Microscopy are used to analyze quantitatively the diffusion of tin through the photoanode. At temperatures (400 to 600 °C) and times (30 to 90 min) typically employed in the calcinations of titanium dioxide layers for dye sensitized solar cells, tin is observed to diffuse through several micrometers of the photoanode. The transport of tin is reasonably described using Fick\u27s Law of Diffusion through a semi-infinite medium with a fixed tin concentration at the interface. Numerical modeling allows for extraction of mass transport parameters that will be important in assessing the degree to which tin diffusion influences the performance of dye sensitized solar cells

Titanium Dioxide

This book presents a comprehensive overview of titanium dioxide, including recent advances and applications. It focuses on the compound’s uses in environmental remediation, photocatalytic materials, rechargeable lithium-ion batteries, thin films, energy storage, semiconductors, and much more. This volume is a useful resource for researchers, scientists, engineers, and students

SPATIAL TRANSFORMATION PATTERN DUE TO COMMERCIAL ACTIVITY IN KAMPONG HOUSE

ABSTRACT Kampung houses are houses in kampung area of the city. Kampung House oftenly transformed into others use as urban dynamics. One of the transfomation is related to the commercial activities addition by the house owner. It make house with full private space become into mixused house with more public spaces or completely changed into full public commercial building. This study investigate the spatial transformation pattern of the kampung houses due to their commercial activities addition. Site observations, interviews and questionnaires were performed to study the spatial transformation. This study found that in kampung houses, the spatial transformation pattern was depend on type of commercial activities and owner perceptions, and there are several steps of the spatial transformation related the commercial activity addition. Keywords: spatial transformation pattern; commercial activity; owner perception, kampung house; adaptabilit

NIR sensitive organic dyes for tandem solar cells and transparent photodiodes

Due to advantages such as mechanical flexibility, light weight and the prospect to use low-cost roll-to-roll manufacturing processes, organic semiconductors have been widely investi-gated in many application areas as alternatives for their inorganic counterpart. In organic sem-iconductors, the rather weak Van der Waals interactions holding together the molecular build-ing blocks result in narrow absorption bands which endow organic electronics with important advantages for the development of smart functionalities. Transparent organic electronics (TOEs), for example, incorporate devices through which visible light is transmitted. Among other semiconducting devices, it is actually possible to construct sensors and photovoltaic de-vices that solely use ultraviolet (UV) and near infrared (NIR) light to produce electrical energy or signal. TOEs have been proposed for easy integration with other electronic devices. Among the different molecular materials, cyanine dyes stand out by sharp, intense absorption bands exhibiting the highest molar extinction coefficients. The absorption peak can be easily shifted into the NIR wavelength region by increasing the length of the conjugated polymethine chain. For example, NIR light absorbing heptamethine cyanine dyes (Cy7) are promising candidates as transparent and colorless photoactive film materials. In this thesis work, highly efficient TOE devices such as transparent solar cells and transparent photodetectors using NIR absorbing cyanine dyes as photosensitive materials have been successfully fabricated. To optimize these multilayer devices, various cyanine dyes were in-vestigated, device architecture and interfaces were engineered. Optical simulations of the stacked thin film structures allowed understanding and tuning device performance. Moreover, organic solar cells which are transparent in the visible range have been integrated into tandem and triple junction solar cells. Low bandgap materials that absorb NIR light were combined with cyanine cells which absorb visible light, thereby more sunlight could be harvested and power conversion efficiency was dramatically enhanced in such tandem solar cells. The photo-stability investigation of cyanine solar cells showed that cyanine dyes were photostable when illuminated in the absence of oxygen and water vapor. We found that the initial degradation of cyanine dye devices during operation was due to the photo-polymerization of the widely used electron acceptor material fullerene C60 and photo-chromism of the hole extraction interfacial layer molybdenum oxide (MoO3)

DEVELOPMENT AND EVALUATION OF CARBON-BASED QUANTUM DOTS FOR CARBON DIOXIDE PHOTOCONVERSION

World energy consumption has increasingly grown over the past several decades.Because of its potential in photochemical energy conversion, photocatalysis has been the subject of much recent research. Recently, carbon or graphene-based quantum dots have attracted growing attention in solar energy conversion applications, because of its unique optoelectronic properties, broad-band optical absorption, bright fluorescence emissions, favorable photoinduced electron transfer properties, reliable chemical inertness and stability, cost-effectiveness, and non-toxicity. While nanosized wide band gap semiconductor-based systems were largely at the center of attention in such studies, carbon-based quantum dots have recently emerged as a new class of semiconductor like photoactive materials, due to some of its excellent optical figures of merit suited for light harvesting applications. In this dissertation, we have demonstrated the possibility of using quantum-sized carbon particles as chromophores for photosensitized energy conversion and visible-light photocatalysts for carbon dioxide conversion to organic acids as well as results supporting photoinduced redox properties in carbon nanodots. Metal- and semiconductor-doped carbon nanodots in various configurations have been developed for their utility in photocatalytic conversion of carbon dioxide. Our results demonstrate that nanoscale carbon dots represent a promising new alternative platform for light-driven energy conversion applications, competitive to conventional nanoscale semiconductor-based photocatalytic systems

Transient spectroscopic studies of photocatalysts for CO2 and proton reduction

In this thesis, optical and electrochemical techniques are used to study the factors controlling catalytic function in solar-to-fuel conversion systems. Chapter 3, the first results chapter, considers a system for CO2 reduction based on a Re photocatalyst anchored to TiO2. This chapter reports evidence that the immobilisation of the photocatalyst via covalent bonds improves the stability of one of the key reaction intermediates resulting in higher catalytic yields. This chapter also provides insight into the nature and timescale of the steps in the mechanism of CO2 reduction. Chapter 4 considers a proton reduction system based on a Ru absorber, a Ni electrocatalyst and a sacrificial electron donor. This chapter discusses the mechanism behind the strong pH dependence in this system. The results show that whereas the electron transfer between the dye anions and the electrocatalyst is pH independent, the generation of dye anions and the catalytic function of the electrocatalyts have opposite pH-dependencies. Chapter 5 considers a photocathode for proton reduction based on a Cu2O/Al:ZnO buried p-n junction with protection and catalyst layers. The results presented show that the buried junction controls charge separation and the photocurrent onset. Furthermore, the catalyst layer is found to slow down charge recombination and help achieve high reduction yields. This chapter also discuses the mechanism of proton reduction and how the nature of the rate-limiting step has an impact in the recombination kinetics. Chapter 6 discusses the use of transient absorption spectroscopy to study high refractive index materials with high quality interfaces. This chapter investigates light interference effects in TiO2, Cu2O and a CH3NH3PbI3 perovskite device. The results show that interference effects in these materials can dominate their transient spectra, hindering its interpretation. However, it is found that this spectroscopy can also be used to extract information about the changes of the refractive index.Open Acces

Thermal, electrical and mechanical properties of three-dimensional functional materials

Colloidal assembly is a dynamic phenomenon where the particulates dispersed in fluids, with the size over tens of nms to several μms, form into specific spatial organization resulting from the variations in the surroundings. The general hard sphere colloids with charged surfaces can be self-assembled into the periodic arrays during the drying process of the fluids. These static periodic arrays, namely, colloidal crystals do not possess any dynamic functionalities, but serve as a sacrificial template for the fabrication of various classes of 3D functional materials. On the other hand, some colloids themselves have their own dynamic functionalities, so that they can be directed-assembled in response to external triggering forces. These particles serve as an active element that offers dynamic changes in the properties of the material systems. The inorganic 3D functional meso/nanostructures were developed for the potential uses in thermal management applications using the self-assembled colloidal crystals as the template. Especially, the Fe3O4 was epitaxially grown through the complex 3D colloidal templates, after which the single crystal Fe3O4 3D porous structures were obtained. These materials have the multiple nanosized 3D interfaces to deter the phonon transport, and at the same time consist of the single crystals to enhance the electron transport. Through various kinds of analysis tools, we thoroughly characterized the materials, particularly focusing on the crystallinity, the density, the thermal conductivity, and the electrical conductivity. The epitaxial Fe3O4 nanoporous structures including the pores with 40 nm in diameter were identified to be thermally insulating and electrically conductive at the same time. The dynamically reconfigurable colloidal assembly in the viscoelastic fluids was investigated with the ultimate goals of the energy harvesting. As the first step, two different methods of integrating the colloids into the viscoelastic media were developed. The PNIPAM colloids, which intrinsically possess the thermo-responsive functionality, were synthesized by two kinds of polymerization routes, and then incorporated into the fibrin networks hydrogels using the method developed. The PNIPAM microgels/fibrin networks hydrogel composites demonstrated the reversibly switchable mechanical property, which is multifold jump in the storage modulus due to the strain-stiffening of fibrin networks, in response to the external temperature changes