A Techno-Economic Analysis of Space-Based Solar Power Systems

Space-based solar power (SBSP) promises to provide flexible renewable baseload power. However, no full-system prototype exists due to a perceived lack of economic viability. The goal of this thesis is therefore to determine how different technology approaches can improve key technical metrics of SBSP and consequently the economics. For this purpose, we divide the system into its three main segments and define critical metrics for the performance of each subsystem. Based on these, novel technology approaches from the literature are then evaluated. For the solar satellite, we are able to show that a number of technology options exist that might improve power levels, radiation resistance, and mass-related ratios. These advances would greatly benefit overall system economics, as the space segment constitutes a big lever for enhancing the levelised cost of electricity (LCOE). Furthermore, microwave power beaming efficiencies in line with required levels have been demonstrated but so far lack the scale and distance necessary for SBSP. Ultimately, the global capacity in space lift capabilities appears to be a major bottleneck. Consequently, a reduction in mass of the satellite would not only be a matter of economics but might render any such project even possible in the first place. Keywords: Energy; Solar; Space; Microwaves; Sustainability.Space-based solar power (SBSP) promises to provide flexible renewable baseload power. However, no full-system prototype exists due to a perceived lack of economic viability. The goal of this thesis is therefore to determine how different technology approaches can improve key technical metrics of SBSP and consequently the economics. For this purpose, we divide the system into its three main segments and define critical metrics for the performance of each subsystem. Based on these, novel technology approaches from the literature are then evaluated. For the solar satellite, we are able to show that a number of technology options exist that might improve power levels, radiation resistance, and mass-related ratios. These advances would greatly benefit overall system economics, as the space segment constitutes a big lever for enhancing the levelised cost of electricity (LCOE). Furthermore, microwave power beaming efficiencies in line with required levels have been demonstrated but so far lack the scale and distance necessary for SBSP. Ultimately, the global capacity in space lift capabilities appears to be a major bottleneck. Consequently, a reduction in mass of the satellite would not only be a matter of economics but might render any such project even possible in the first place. Keywords: Energy; Solar; Space; Microwaves; Sustainability

Lower General Position in Cartesian Products

A subset $S$ of vertices of a graph $G$ is in \emph{general position} if no shortest path in $G$ contains three vertices of $S$. The \emph{general position problem} consists of finding the number of vertices in a largest general position set of $G$, whilst the \emph{lower general position problem} asks for a smallest maximal general position set. In this paper we determine the lower general position numbers of several families of Cartesian products. We also show that the existence of small maximal general position sets in a Cartesian product is connected to a special type of general position set in the factors, which we call a \emph{terminal set}, for which adding any vertex $u$ from outside the set creates three vertices in a line with $u$ as an endpoint. We give a constructive proof of the existence of terminal sets for graphs with diameter at most three. We also present conjectures on the existence of terminal sets for all graphs and a lower bound on the lower general position number of a Cartesian product in terms of the lower general position numbers of its factors

Pressureless Sintering of Powder Processed Graded Metal-Ceramic Composites Using a Nanoparticle Sintering Aid and Bulk Molding Technology

The need exists to fabricate graded metal-ceramic composites in bulk manufacturing processes for commercial applications. To address this need, a three-fold approach is employed: (1) control of the evolution of shrinkage strain and mechanical properties through the use of a nanoparticle sintering aid, (2) modeling of shrinkage-induced stresses to determine gradient architectures where cracking does not occur, and (3) fabrication of graded metal-ceramic composites using pressureless sintering and bulk molding technology. A new nanopowder TiO2 sintering aid was introduced to control the evolution of shrinkage and mechanical properties of graded Nickel-Alumina composites. The evolution of shrinkage strain and mechanical properties were then used in a recently developed two-dimensional microthermomechanical finite element analysis to determine the effects on shrinkage-induced stresses and develop gradient architectures where cracking would not occur. Finally, a laboratory-scale processing system based on a commercial bulk molding technology was developed to bulk process geometrically-complex gradient structures

Density Functional Theory for the Investigation of Transition Metal Complexes: Structure, Binding, and Spectroscopy of Metal-Siderophores and the Catalase-Peroxidase Enzyme

Since the development of quantum mechanics in the 1920\u27s and with the introduction of the Schrödinger equation in 1926, various methods to solve the Schrödinger equation have evolved. With advances in these computational methods, we are now able to solve the Schrödinger equation for systems that did not seem possible less than a century ago. Density functional theory (DFT) is a valuable tool for the exploration of the molecular properties of biological systems, and is based upon the theory that the exact energy could be determined from the knowledge of the electron density. The purpose of this dissertation is to explore the use of modern density functional theory methods to compute the structural, spectroscopic and mechanistic properties of biological molecules. In particular, DFT will be use to explore insights into metal-ligand interactions of siderophore-transition metal complexes and to explore the properties of a unique tyrosyl-like radical of the Catalase Peroxidase (KatG) enzyme

Unique composition of the preprotein translocase of the outer mitochondrial membrane from plants

Transport of most nuclear encoded mitochondrial proteins into mitochondria is mediated by heteropolymeric translocases in the membranes of the organelles. The translocase of the outer mitochondrial membrane (TOM) was characterized in fungi, and it was shown that TOM from yeast comprises nine different subunits. This publication is the first report on the preparation of the TOM complex from plant mitochondria. The protein complex from potato was purified by (a) blue native polyacrylamide gel electrophoresis and (b) by immunoaffinity chromatography. On blue native gels, the potato TOM complex runs close to cytochrome c oxidase at 230 kDa and hence only comprises about half of the size of fungal TOM complexes. Analysis of the TOM complex from potato by SDS-polyacrylamide gel electrophoresis allows separation of seven different subunits of 70, 36, 23, 9, 8, 7, and 6 kDa. The 23-kDa protein is identical to the previously characterized potato TOM20 receptor, as shown by in vitro assembly of this protein into the 230kDa complex, by immunoblotting and by direct protein sequencing. Partial amino acid sequence data of the other subunits allowed us to identify sequence similarity between the 36-kDa protein and fungal TOM40. Sequence analysis of cDNAs encoding the 7-kDa protein revealed significant sequence hornology of this protein to TOM7 from yeast. However, potato TOM7 has a N-terminal extension, which is very rich in basic amino acids. Counterparts to the TOM22 and TOM37 proteins from yeast seem to be absent in the potato TOM complex, whereas an additional low molecular mass subunit occurs. Functional implications of these findings are discussed

New insights into the co-evolution of cytochrome c reductase and the mitochondrial processing peptidase

The mitochondrial processing peptidase (MPP) is a heterodimeric enzyme that forms part of the cytochrome c reductase complex from higher plants. Mitochondria from mammals and yeast contain two homologous enzymes: (i) an active MPP within the mitochondrial matrix and (ii) an inactive MPP within the cytochrome c reductase complex. To elucidate the evolution of MPP, the cytochrome c reductase complexes from lower plants were isolated and tested for processing activity. Mitochondria were prepared from the staghorn fern Platycerium bifurcatum, from the horsetail Equisetum arvense, and from the colorless algae Polytomella, and cytochrome c reductase complexes were purified by a micro-isolation procedure based on Blue-native polyacrylamide gel electrophoresis and electroelution. This is the first report on the subunit composition of a respiratory enzyme complex from a fern or a horsetail. The cytochrome c reductase complexes from P. bifurcatum and E. arvense are shown to efficiently process mitochondrial precursor proteins, whereas the enzyme complex from Polytomella lacks proteolytic activity. An evolutionary model is suggested that assumes a correlation between the presence of an active MPP within the cytochrome c reductase complex and the occurrence of chloroplasts

An atomic finite element model for biodegradable polymers. Part 2. A model for change in Young’s modulus due to polymer chain scission

Atomic simulations were undertaken to analyse the effect of polymer chain scission on amorphous poly(lactide) during degradation. Many experimental studies have analysed mechanical properties degradation but relatively few computation studies have been conducted. Such studies are valuable for supporting the design of bioresorbable medical devices. Hence in this paper, an Effective Cavity Theory for the degradation of Young's modulus was developed. Atomic simulations indicated that a volume of reduced-stiffness polymer may exist around chain scissions. In the Effective Cavity Theory, each chain scission is considered to instantiate an effective cavity. Finite Element Analysis simulations were conducted to model the effect of the cavities on Young's modulus. Since polymer crystallinity affects mechanical properties, the effect of increases in crystallinity during degradation on Young's modulus is also considered. To demonstrate the ability of the Effective Cavity Theory, it was fitted to several sets of experimental data for Young's modulus in the literature

Unlocking novel opportunities: How online ideation platforms implicitly guide employees toward better ideas by spurring their desire to innovate

Employees' innovative behaviour becomes increasingly important for organizational success. Companies try to improve their innovation capabilities by supporting and motivating employees to show innovative behaviour. Particularly online ideation platforms become relevant because they create new opportunities for employees to be innovative. This paper investigates how exposure to online ideation platforms' unique capabilities stimulates intrinsic motivation toward innovative behaviour and ultimately the submission of high‐quality ideas. Based on expectancy and channel expansion theories, we derive a framework with four intrinsic motivational forces that online ideation platforms can stimulate. A two‐study approach empirically tests this framework. The first study uses a multilevel regression on a dataset of 1630 employees nested in 136 departments of a leading international science and technology company. The second study analyses how 279 employees of the same company, who submitted 678 ideas on the company's online ideation platform, continue to be motivated by the platform's inherent characteristics and capabilities and submit high‐quality ideas. The results support the core argument that online ideation platforms stimulate certain desires motivating employees to engage in innovative behaviour and ultimately submit high‐quality ideas. The detailed results offer several contributions to innovation management literature and beyond