Energy conversion and storage via photoelectrochemical methods

Photoelectro analytical chemistry provides an elegant technique by which to explore, amongst others, various industrial and environmental applications. To this end, four areas of photoelectroanalytical chemistry are investigated in order to develop industrially - and environmentally - relevant galvanic and photogalvanic cells, together with exploring the electro-generation of an industrially important molecule and diffusion factors they may affect this generation.The first study is investigated a long-range charge transfer, using tert-butylferrocene (tBuFc) as model hydrophobic system. It is found that the apparent one-dimensional diffusion coefficient depends on the tBuFc loading. It is suggested that an efficient relay mechanism for electron transfer is through the partitioning of the oxidised form between the two subphases, with inter-pseudophase reaction.However, the second study investigated the normal lyotropic liquid crystals (in the lamellar or hexagonal phases) as a route to afford a structured, three-dimensional, quasi-biphasic framework within which electron transfer cascades may take place using cyclic voltammetry. It is shown that these can take place through reagent partitioning between the hydrophobic and hydrophilic subphases, and it is illustrated how the structure and its orientation, the nature of the ionic doping of the framework, and the hydrophobicity of the redox analyte may give rise to changes in the observed voltammetric waveshape.For the case of an artitifical mimic of the first few stages of Photosystem I, it is demonstrated that photo-induced electron transfer is likewise affected by the orientation, and develop a system of photon efficiency of ~0.1%.Thirdly, a novel attempt at power production was attempted with the construction and optimisation of a photogalvanic cell system. A literature review was conducted and a system proposed utilizing 10-methylphenothiazine (NMP) as a light harvester and zinc as a sacrificial electrode with tetrabutylammonium chloride (TBAP) as a supporting electrolyte and chloroform as a mediator. The study aimed to create a cell that could be produced using industrial run-off or other waste water supplies.A series of cells was produced with varying concentrations of both zinc and NMP solutions and the power conversions studied by producing a voltage-current plot for each system. A system that exhibited 9.02% conversion efficiency keep, future studies were conducted to show whether the zinc species effected the power conversion or if silver would act in a similar way.A mechanism was proposed for the power production process and so studies using 2, 4-Dichlorophenol (DCP) rather than chloroform we conducted; it was believed that the dissociation step for DCP was step wise rather than concerted. Lower power production was seen in these cells as predicted by the reaction mechanism. Tris - (4-bromophenyl) - amine (TBA), an alternative light harvester to NMP, was used to see if altering the active chemical agent resulted in efficiency change.Finally , A photogalvanic cell that employs 2,4-dichlorophenol as a fuel source, an N-substituted phenothiazine as light harvester, and sacrificial zinc anode is presented, and shown to afford a ca. 4% light-to-electrical power conversion efficiency in violet light

Biofuels & atmospheric chemistry: what can a global model tell us about our future decisions?

Biomass energy is the oldest form of energy harnessed by humans. Currently, processed biofuels, which are derived from biomass, are being pursued as a possi- ble route to decarbonize the transport sector—a particularly difficult task for both technological and sociological reasons. In this thesis I explore the impacts that large scale biofuel use could have on atmospheric chemistry. I review the current state of biofuels politically and technologically, focusing on ethanol and biodiesel. I discuss the salient features of tropospheric chemistry and in particular the oxidation of isoprene, an important biogenic volatile organic compound. I examine the impact that including isoprene oxidation has in a new chemistry-climate computer model, UKCA; the response of ozone turns out to depend on local chemical conditions. To evaluate the global model, I use data from the OP3 field campaign in Malaysia and compare it with output from the model chemical mechanism. The mechanism is able to reproduce NOx and ozone measurements well, though is more sensitive to representations of physical rather than chemical processes. I also perform a simple sensitivity study which examines crop changes in the region of Southeast Asia. In the final two chapters, I turn to two distinct phases of the biofuel life cycle. I characterize a potential future atmosphere through an ozone attribution study, then examine the impact of future cropland expansion (phase I of a biofuel life cycle) on tropospheric chemistry. I find that land use change has a large impact on ozone, and that it is more acute than another perturbation (CO2 suppression) to isoprene emissions. I then move to phase III of the life cycle—combustion—and look at the sensitivity of the model chemistry to surface transport emissions from biofuels as a replacement for conventional fuels. I find that biodiesel reduces surface ozone, while ethanol increases it, and that the response has both a linear and nonlinear component

Planet Earth 2011

The failure of the UN climate change summit in Copenhagen in December 2009 to effectively reach a global agreement on emission reduction targets, led many within the developing world to view this as a reversal of the Kyoto Protocol and an attempt by the developed nations to shirk out of their responsibility for climate change. The issue of global warming has been at the top of the political agenda for a number of years and has become even more pressing with the rapid industrialization taking place in China and India. This book looks at the effects of climate change throughout different regions of the world and discusses to what extent cleantech and environmental initiatives such as the destruction of fluorinated greenhouse gases, biofuels, and the role of plant breeding and biotechnology. The book concludes with an insight into the socio-religious impact that global warming has, citing Christianity and Islam

Progress in biofuel production from gasification

Biofuels from biomass gasification are reviewed here, and demonstrated to be an attractive option. Recent progress in gasification techniques and key generation pathways for biofuels production, process design and integration and socio-environmental impacts of biofuel generation are discussed, with the goal of investigating gasification-to-biofuels’ credentials as a sustainable and eco-friendly technology. The synthesis of important biofuels such as bio-methanol, bio-ethanol and higher alcohols, bio-dimethyl ether, Fischer Tropsch fuels, bio-methane, bio-hydrogen and algae-based fuels is reviewed, together with recent technologies, catalysts and reactors. Significant thermodynamic studies for each biofuel are also examined. Syngas cleaning is demonstrated to be a critical issue for biofuel production, and innovative pathways such as those employed by Choren Industrietechnik, Germany, and BioMCN, the Netherlands, are shown to allow efficient methanol generation. The conversion of syngas to FT transportation fuels such as gasoline and diesel over Co or Fe catalysts is reviewed and demonstrated to be a promising option for the future of biofuels. Bio-methane has emerged as a lucrative alternative for conventional transportation fuel with all the advantages of natural gas including a dense distribution, trade and supply network. Routes to produce H2 are discussed, though critical issues such as storage, expensive production routes with low efficiencies remain. Algae-based fuels are in the research and development stage, but are shown to have immense potential to become commercially important because of their capability to fix large amounts of CO2, to rapidly grow in many environments and versatile end uses. However, suitable process configurations resulting in optimal plant designs are crucial, so detailed process integration is a powerful tool to optimize current and develop new processes. LCA and ethical issues are also discussed in brief. It is clear that the use of food crops, as opposed to food wastes represents an area fraught with challenges, which must be resolved on a case by case basis

A Comprehensive Study Of Esterification Of Free Fatty Acid To Biodiesel In a Simulated Moving Bed System

Simulated Moving Bed (SMB) systems are used for separations that are difficult using traditional separation techniques. Due to the advantage of adsorption-based chromatographic separation, SMB has shown promising application in petrochemical and sugar industries, and of late, for chiral drug separations. In recent years, the concept of integration of reaction and in-situ separation in a single unit has achieved considerable attention. The simulated moving bed reactor (SMBR) couples both these unit operations bringing down the operation costs while improving the process performance, particularly for products that require mild operating conditions. However, its application has been limited due to complexity of the SMBR process. Hence, to successfully implement a reaction in SMB, a detailed understanding of the design and operating conditions of the SMBR corresponding to that particular reaction process is necessary. Biodiesel has emerged has a viable alternative to petroleum-based diesel as a renewable energy source in recent years. Biodiesel can be produced by esterification of free fatty acids (present in large amounts in waste oil) with alcohol. The reaction is equilibrium-limited, and hence, to achieve high purity, additional purification steps increases the production cost. Therefore, combining reaction and separation in SMBR to produce high purity biodiesel is quite promising in terms of bringing down the production cost. In this work, the reversible esterification reaction of oleic acid with methanol catalyzed by Amberlyst 15 resin to form methyl oleate (biodiesel) in SMBR has been investigated both theoretically and experimentally. First, the adsorption and kinetic constants were determined for the biodiesel synthesis reaction by performing experiments in a single column packed with Amberlyst 15, which acts as both adsorbent and catalyst. Thereafter, a rigorous model was used to describe the dynamic behaviour of multi-column SMBR followed by experimental verification of the mathematical model. Sensitivity analysis is done to determine robustness of the model. Finally, a few simple multi-objective optimization problems were solved that included both existing and design-stage SMBRs using non-dominated sorting genetic algorithm (NSGA). Pareto-optimal solutions were obtained in both cases, and moreover, it was found that the performance of the SMBR could be improved significantly under optimal operating conditions

Experimental study of the chemical degradation of biogenic volatile organic compounds by atmospheric OH radicals

Approximately 1000 Tg of carbon is annually emitted by biogenic sources. In the atmosphere, these compounds are oxidized and thereby secondary air pollutants are formed such as secondary organic aerosol (SOA) and ozone, thus contribution to air quality and climate change. At daytime, biogenic volatile organic compounds (BVOCs) are mainly degraded by photolytically produced hydroxyl (OH) radicals. In the presence of nitric oxide (NO), OH initiated reactions proceed through radical chain reactions that involve organic peroxy radicals (RO2). In field studies conducted in forested environments, which were characterized by large BVOC emissions and low NO concentrations, measured OH concentrations were largely underestimated by model calculations using state-of-the-art chemical models, thus underestimating the oxidative capacity of the atmosphere. In the degradation scheme of isoprene, the BVOC with the globally highest emission rate, new chemical pathways for OH regeneration that involve unimolecular reactions of RO2 have been discovered. However, few studies exist, which investigate radical regeneration in the photooxidation of other abundant hydrocarbons and monoterpenes. This thesis aims for investigating potential new pathways for radical regeneration in the the photooxidation of three selected BVOCs that were abundant in previous field campaigns: 2-methyl-3-butene-2-ol (MBO), alpha-pinene, and the oxidation production of alpha-pinene, pinonaldehyde. In total, five experiments, which were conducted in 2012 and 2014 in the atmospheric simulation chamber SAPHIR (Simulation of Atmospheric PHotochemistry In a large Reaction chamber), are analyzed. A comprehensive set of instruments provided concentration measurements of OH and hydroperoxy (HO2) radicals, OH reactivity, injected BVOCs, formed oxidation products, NOx (= NO + NO2), and measurements of physical parameters (radiation, temperature, and pressure). In contrast to previous studies, all experiments were performed at ambient reactant concentrations and low NO mixing ratios (< 220 pptv, parts per trillion by volume) to simulate conditions that are typical in forested regions. In the analysis of this work, measured concentration time series of radicals and organic compounds are compared to zero-dimensional box model calculations that are derived from the recent version of the Master Chemical Mechanism (MCM). The MCM is a widely used state-of-the-art atmospheric chemical mechanism. In the MBO experiment, the model is capable to reproduce observed radical concentrations and measured product distributions. In contrast, the MCM significantly underestimates measured OH and HO2 concentrations in the photooxidation of alpha-pinene and pinonaldehyde. However, the model can reproduce observed OH concentrations when modeled HO2 concentrations are constrained to measurements. This shows that the current alpha-pinene and pinonaldehyde degradation mechanisms lack HO2 sources. In addition, measurements of the oxidation product pinonaldehyde suggest that the yields of RO2 radicals formed in the initial attack of OH on α-pinene are different than previously assumed. For each analyzed BVOC, sensitivity model studies were performed with modification of the MCM mechanism based on available theoretical studies that provide additional reaction pathways of RO2 radicals, different branching ratios, and unimolecular reactions. Additional sensitivity runs were done to explain the missing HO2 source. In the pinonaldehyde experiments, the MCM strongly underestimates the pinonaldehyde degradation. This could be partly explained by the parameterization of the pinonladehyde photolysis rate in the MCM. In order to explain the observed pinonaldehyde consumption, the photolysis rate needs to be a factor of 3 higher than the values calculated with the parameterization in the MCM. This is consistent with calculations of the photolysis rate using the measured solar actinic flux spectrum, a published absorption spectrum, and adjusting the effective quantum yield to a value of 0.9. At low NO concentrations, the reaction of RO2 with HO2 gains in importance in the competition with RO2 reactions with NO. Recent studies showed that the reaction of acetylperoxy radicals (CH3C(O)O2) with HO2 does not only terminate the radical reaction chain but can regenerate OH radicals and therefore can contribute to missing radical regenration in remote regions. The CH3C(O)O2 detection in previous laboratory studies was mainly done in the ultraviolet (UV). In this spectral area, the absorption spectra of different peroxy radicals overlap. This could lead to systematic errors in the determination of concentrations and reaction rate constants if not properly accounted for. In this thesis, the near infrared spectrum and absorption cross sections of CH3C(O)O2 were measured by cavity ring-down spectroscopy (CRDS). The newly measured absorption cross sections were used to convert CH3C(O)O2 absorbance into absolute concentrations. Measured CH3C(O)O2 concentration time series were used to validate the absorption cross section by redetermining the second-order reaction rate of the CH3C(O)O2 self-reaction. The newly measured absorption cross sections will help to achieve more accurate measurements of CH3C(O)O2 concentration in future laboratory experiments to better quantify the fraction of regenerated radicals. The results presented in this thesis, help to discover new radical regeneration pathways and improve the understanding of model-measurement discrepancies, which have been observed in previous field experiments. However, future studies are needed that provide additional measurements of oxidation products and reaction intermediates to further resolve reaction pathways

Models, Simulations, and the Reduction of Complexity

Modern science is a model-building activity. But how are models contructed? How are they related to theories and data? How do they explain complex scientific phenomena, and which role do computer simulations play? To address these questions which are highly relevant to scientists as well as to philosophers of science, 8 leading natural, engineering and social scientists reflect upon their modeling work, and 8 philosophers provide a commentary

Rheology and Processing of Polymers

This book covers the latest developments in the field of rheology and polymer processing, highlighting cutting-edge research focusing on the processing of advanced polymers and their composites. It demonstrates that the field of rheology and polymer processing is still gaining increased attention. Presented within are cutting-edge research results and the latest developments in the field of polymer science and engineering, innovations in the processing and characterization of biopolymers and polymer-based products, polymer physics, composites, modeling and simulations, and rheology

Energy, Science and Technology 2015. The energy conference for scientists and researchers. Book of Abstracts, EST, Energy Science Technology, International Conference & Exhibition, 20-22 May 2015, Karlsruhe, Germany

We are pleased to present you this Book of Abstracts, which contains the submitted contributions to the "Energy, Science and Technology Conference & Exhibition EST 2015". The EST 2015 took place from May, 20th until May, 22nd 2015 in Karlsruhe, Germany, and brought together many different stakeholders, who do research or work in the broad field of "Energy". Renewable energies have to present a relevant share in a sustainable energy system and energy efficiency has to guarantee that conventional as well as renewable energy sources are transformed and used in a reasonable way. The adaption of existing infrastructure and the establishment of new systems, storages and grids are necessary to face the challenges of a changing energy sector. Those three main topics have been the fundament of the EST 2015, which served as a platform for national and international attendees to discuss and interconnect the various disciplines within energy research and energy business. We thank the authors, who summarised their high-quality and important results and experiences within one-paged abstracts and made the conference and this book possible. The abstracts of this book have been peer-reviewed by an international Scientific Programme Committee and are ordered by type of presentation (oral or poster) and topics. You can navigate by using either the table of contents (page 3) or the conference programme (starting page 4 for oral presentations and page 21 for posters respectively)