Renewable energy-hydrogen systems for remote area power supply (RAPS) constitute an early niche market for sustainable hydrogen energy. The primary objective of this research has been to investigate the possibility of direct coupling of a PV array to a proton exchange membrane (PEM) electrolyser by appropriate matching of the current-voltage characteristics of both the components. The degree to which optimal matching can be achieved by direct coupling has been studied both theoretically and experimentally. A procedure for matching the maximum power point output of a PV array with the PEM electrolyser load to maximise the energy transfer between them has been presented. The key element of the matching strategy proposed is to vary the series-parallel stacking of individual cells in both the PV array and the PEM electrolyser so that the characteristic current (I) -voltage (V) curves of both the components align as closely as possible. This procedure is applied to a case study of direct coupling a PV array comprising 75 W panels (BP275) to a PEM electrolyser bank assembled from 50 W PEM electrolyser stacks (h-tec StaXX7). It was estimated theoretically that the optimal PV-electrolyser combination would yield an energy transfer of over 94% of the theoretical maximum on annual basis. This combination also gave the lowest hydrogen production cost on a lifecycle basis. An experimental test of this theoretical result for direct coupling was conducted over a period of 728 hours, with an effective direct-coupling operational time of about 467 hours (omitting the hours of zero solar radiation). Close agreement between the theoretically predicted and actual energy transfer from the PV array to the electrolyser bank in this trial was found. The difference between theoretical and experimental hydrogen production was less then 1.2%. The overall solar-to-hydrogen energy conversion efficiency was found to be 7.8%. The electrolysers were characterised before and after the direct coupling experiment, and showed a small decline in Faraday efficiency and energy efficiency. But this decline was less than the uncertainties in the measured values, so that no firm conclusions about electrolyser degradation can be drawn at this stage. Another direct-coupling experiment, using a larger scale PV-electrolyser system, that is, a 2.4 kW PV array at RMIT connected to the 'Oreion Alpha 1' stand-alone 2 kW PEM electrolyser developed by the CSIRO Energy Technology, was also successfully conducted for a period of 1519 hours (with 941 hours of effective operational time of the electrolyser). Energy-efficient direct coupling of a PV array and electrolyser as examined in this thesis promises to improve the economic viability of solar-hydrogen systems for remote power supply since the costs of an electronic coupling system employing a maximum power point tracker (MPPT) and dc-to-dc converter (around US$ 700/ kW) are avoided.

III-nitride nanowires (NWs) have been recognized as efficient photoelectrochemical (PEC) devices due to their large surface-to-volume ratio, tunable bandgap, and chemical stability. Doping engineering can help to enhance the PEC performance further. Therefore, addressing the effects of Si and Mg doping on the III-nitride NW photoelectrodes is of great interest. In this study, doping levels of NWs were tuned by the dopant effusion cell temperature of the molecular beam epitaxy (MBE) growth. The successful doping of the III-nitride NWs was confirmed using photoluminescence (PL), Raman spectroscopy, and open circuit potential (OCP) measurements. The ionized dopant concentrations of Si-doped InGaN/GaN NWs were systematically quantified by electrochemical impedance studies (EIS). Due to the three dimensional surfaces of NWs, modified Mott-Schottky formulas were induced to improve the accuracy of ionized dopant concentrations. The highest dopant concentration of Si-doped InGaN NWs can reach 2.1x1018 cm-3 at Tsi = 1120 oC. Accordingly, the estimated band edge potentials of the tested NWs straddled the redox potential of water splitting. The PEC performance of these devices was investigated by linear scan voltammetry (LSV), chronoamperometry tests, and gas evolution measurements. The results were consistent with the quantified dopant concentrations. The current density of n-InGaN NWs doped at TSi = 1120 oC was nine times higher than the undoped NWs. Additionally, the doped NWs exhibited stoichiometric hydrogen and oxygen evolution. By doping Mg into InGaN and GaN segments separately, the p-InGaN/p-GaN NWs demonstrated improved PEC performance, compared with undoped-InGaN/p-GaN and n-InGaN/n-GaN NWs. The p-InGaN/p-GaN NWs exhibited a highly stable current density at ~-9.4 mA/cm2 for over ten hours with steady gas evolution rates (~107 μmol/cm2/hr for H2) at near a stoichiometric ratio (H2: O2~ 1.8:1). This study demonstrated that optimizing the doping level and appropriate band engineering of III-nitride NWs is crucial for enhancing their PEC water splitting performance.

Remote area power supply (RAPS) is a potential early market for renewable energy - hydrogen systems because of the relatively high costs of conventional energy sources in remote regions. Solar-hydrogen RAPS systems commonly employ photovoltaic panels, a Proton Exchange Membrane (PEM) electrolyser, a storage for hydrogen gas, and a PEM fuel cell. Unitised Regenerative Fuel Cells (URFCs) use the same hardware for both electrolyser and fuel cell functions. Since both of these functions are not required simultaneously in a solar hydrogen RAPS system, URFCs based on PEM technology provide a promising opportunity for reducing the cost of the hydrogen subsystem used in renewable-energy hydrogen systems for RAPS. URFCs also have potential applications in the areas of aerospace, submarines, energy storage for central grids, and hydrogen cars. In this thesis, a general theoretical relationship between cell potential and current density of a single-cell PEM URFC operating in both fuel-cell (FC) and electrolyser (E) modes is developed using modified Butler-Volmer equations for both oxygen- and hydrogen-electrodes, and accounting for mass transport losses and saturation behaviour in both modes, membrane resistance to proton current, and membrane and electrode resistances to electron current. This theoretical relationship is used to construct a computer model based on Excel and Visual Basic to generate voltage-current (V-I) polarisation curves in both E and FC modes for URFCs with a range of membrane electrode assembly characteristics. The model is used to investigate the influence on polarisation curves of varying key parameters such charge transfer coefficients, exchange current densities, saturation currents, and membrane conductivity. A method for using the model to obtain best-fit values for electrode characteristics corresponding to an experime ntally-measured polarisation curve of a URFC is presented. The experimental component of the thesis has involved the design and construction of single PEM URFCs with an active area of 5 cm2 with a number of different catalyst types and loadings. V-I curves for all these cells have been measured and the performance of the cells compared. The computer model has then been used to obtain best-fit values for the electrode characteristics for the URFCs with single catalyst materials active in each mode on each electrode for the corresponding experimentally-measured V-I curves. Generally values have been found for exchange current densities, charge transfer coefficients, and saturation current densities that give a close fit between the empirical and theoretically-generated curves. The values found conform well to expectations based on the catalyst loadings, in partial confirmation of the validity of the modelling approach. The model thus promises to be a useful tool in identifying electrodes with materials and structures, together with optimal catalyst types and loadings that will improve URFC performance. Finally the role URFCs can play in developing cost-competitive solar- hydrogen RAPS systems is discussed, and some future directions for future URFC research and development are identified.

Masters diploma The purpose of the masters diploma work is analysis of efficiency of hydrogen power stations. Based on the data collected in the work, current exploration directions in hydrogen energetic and kinds of fuel cells can be reviewed, as well as results of a laboratory tests, performed with laboratory fuel specimens. Hydrogen power station, as a station of the future, is currently in the developing phase. Fuel cell and solar panel battery types and efficiency factors are examined, considering fuel cells and solar panel batteries, as primary supply source, are major components in the power station. The most important thing in operation of the power station is it‘s rate of efficiency. The attempt will be made to determine common efficiency value of such power station. It will be possible to compare received results with those provided in the specified literature.

Thesis (M.S.)--Humboldt State University, 2009. / Includes bibliographical references (leaves 163-167). Also available via Humboldt Digital Scholar.

Doctor of Philosophy / Department of Chemistry / Stefan Bossmann / Tris-homoleptic ruthenium(II)-quaterpyridyl and quaterpyridinium complexes, with +8 and +14 charge were synthesized by utilizing high pressure reaction pathway. These complexes have diameters ranging from 1.82 to 4.55 nm according to the molecular modeling calculations. These ruthenium complexes are highly luminescent and contain long excited state life times. The novel ruthenium(II)-quaterpyridinium complexes exhibit superior reactivity as sensitizer-relay-assemblies (SRA‟s) in sacrificial systems for water and carbon dioxide reductions, while harvesting the ultraviolet- and most of the visible fraction of the incident solar spectrum. Ru(II)-quaterpyridinium complexes and Pd/TiO2 catalysts were successfully used as the catalytic system for the photo catalytic reduction of water and carbon dioxide to hydrogen and methane respectively. Phosphonate-tethered Ru(II)-quaterpyridinium complexes were synthesized from Ru(II)-tris-quaterpyridyl complexes. These complexes form stable adhesive layers on indium tin oxide (ITO) electrodes. A series of differential pulse voltammetry experiments were carried out to measure the ground state and excited state redox potentials of all the Ru(II)quaterpyridinium complexes. The reductive potentials obtained were compared with the reductive potentials of CO2 to CH4 and H2O to H2 reductions. The measurements obtained from the experiments confirmed that it is possible to thermodynamically oxidize water and reduce CO2 by using phosphonate-tethered Ru(II)-quaterpyridinium complexes. These complexes are successfully utilized as prototypes for mycobacterial channel blockers. The Ru(II) complexes show distinct changes in their luminescence spectra when bound to the porin MspA from M. smegmatis, which is a non-pathogenic relative of M. tuberculosis. By using HPLC, we have determined binding constants of the Ru(II)-complexes to MspA in phosphate buffer (0.05 M, pH = 6.8) ranging from 5.2 x 109 M-1 (Ru-C2) to 1.8 x 109 M-1 (Ru-C4). Our findings indicate that channel blocking is a promising treatment strategy for mycobacterial infections. Poly-N-isopropyl-acrylamide/acetic acid copolymers were synthesized and characterized by elemental analysis and gel permeation chromatography. The average composition of the copolymers determined from CHN analysis is in excellent correlation with the feed composition indicating that the radical polymerization process is indeed statistical. Crosslinking of individual polymer chains permitted the generation of ultraflat layers on Mica surfaces by a simple spin-casting procedure, which are able to host the mycobacterial channel protein MspA, while retaining its channel function.

Thesis. (M. Tech. (Dept. Electronic Engineering, Faculty of Engineering and Technology))--Vaal University of Technology, 2011. / There are a number of ways to produce hydrogen using solar energy as the primary source. Water electrolysis, which uses solar electrical energy, is the rapidly available process. Hydrogen can be produced by using solar electric energy from photovoltaic (PV) modules for the electrolysis of water without emitting carbon dioxide or requiring fossil fuels. Solar hydrogen energy systems are considered one of the cleanest hydrogen production technologies, where the hydrogen is obtained from sunlight by directly connecting the photovoltaic modules to the hydrogen generator. This dissertation presents a designed solar photovoltaic electrolyser hydrogen production and storage system for various applications such as in the power generation and telecommunications industries. Various experiments were performed on the designed system to ensure its reliability and conformity with theoretical findings. The purity of the generated hydrogen was determined. The relationship between the amount of solar irradiance reaching the surface of the PV panel, the PV panel surface temperature, the PV panel tilt angle and the maximum power point voltage and current of the PV panel array were also considered. The effect of dust on the panel voltage and current outputs was also determined. Finally, the factors to consider when designing a solar photovoltaic electrolyser hydrogen system (based on this study) were enumerated.

In many developing economies, a high percentage of domestic energy demand is for cooking based on fossil and biomass fuels. Their use has serious health consequences affecting almost 3 billion people. Cleaner cooking systems have been promoted in these countries such as solar cooking and smokeless stoves with varying degrees of success. In parallel, solar electrolytic hydrogen systems have been developed and increasingly used during the last 25 years for electricity, heat and automobile fueling applications. This study has developed and tested experimentally in the laboratory a solar hydrogen plant numerical model suitable for small communities, to generate and store cooking fuel. The numerical model was developed in TRNSYS and consists of PV panels supplying a PEM electrolyser of 63.6% measured stack efficiency and hydrogen storage in metal hydride cylinders for household distribution. The model includes novel components for the operation of the PEM electrolyser, its controls and the metal hydride storage, developed based on data of hydrogen generation, stack temperature and energy use from a purpose constructed small-scale experimental rig. The model was validated by a second set of experiments that confirmed the accurate prediction of hydrogen generation and storage rates under direct power supply from PV panels. Based on the validated model, large-scale case studies for communities of 20 houses were developed. The system was sized to generate enough hydrogen to provide for typical domestic cooking demand for three case-studies; Jamaica, Ghana and Indonesia. The daily cooking demands were calculated to be 2.5kWh/day for Ghana, 1.98kWh/day for Jamaica and 2kWh/day for Indonesia using data mining and a specific quantitative survey for Ghana. The suitability of weather data used in the model was evaluated through Finkelstein Schafer statistics based on composite and recent weather data and by comparing simulation results. A difference of 0.9% indicated that the composite data can be confidently used. Simulations results indicate that a direct connection system to the PV plant rather than using a battery is the optimal design option based on increased efficiency and associated costs. They also show that on average 10tonnes of CO2/year/household can be saved by replacing biomass fuel with hydrogen. The potential of total savings in the three case-study countries is shown in the form of novel solar hydrogen potential maps. The results of this study are a contribution towards better understanding the use of hydrogen systems and enhancing their role in renewable energy policy.