In Malawi 2.5 % of the forest disappears each year. The use of firewood and charcoal, deriving from forest resources, accounts for about 99 % of the household energy demand in Malawi and is a cause to the deforestation. The Government of Malawi recently launched a programme called Promotion of Alternative Energy Sources Programme (PAESP) with the aim to reduce the use of firewood and charcoal. One of the fuels included in the programme is the biomass briquette. The aim with this study is to evaluate the viability of biomass briquettes as a sustainable alternative energy source to firewood and charcoal for households in Malawi. Research for the study was carried out during three months in Malawi. Visits were made to a number of briquette production sites to study the manufacturing methods and to collect briquette samples. The briquettes were tested using various methods and then compared with results for firewood and charcoal. At the moment various production methods are used in Malawi, with a high difference in technical complexity and cost. Machines produced from wood using very basic mechanics can apply similar pressure as more advanced metal pressers. They also seem to be better suited than those made of metal, in terms of price and availability. The majority of the briquette producers in Malawi use waste paper as base material. Although the paper briquettes are good, other raw materials will be needed if the production is supposed to be significantly increased. The briquettes burn well using the most common stoves in Malawi, including the commonly used charcoal stove. While firewood is cheaper to use than other available fuels, the briquettes seem to be able to compete with the fuel costs for charcoal.

With increasing concerns about the harmful effects of conventional liquid fossil fuel emissions, natural gas has become a very attractive alternative fuel to power prime movers and stationary energy conversion devices. This research studies the injection and ignition numerically for natural gas (mainly methane) as a fuel applied to diesel engine. Natural gas injector and glow plug ignition enhancement are two of the most technical difficulties for direct injection natural gas engine design. This thesis models the natural gas injector, and studies the characteristics of the internal flow in the injector and natural gas jet in the combustion chamber during the injection process. The poppet valve model and pintle valve model are the first reported models to simulate the natural gas injector to improve the traditional velocity and pressure boundary conditions. This thesis also successfully models the glow plug assisted natural gas ignition and combustion processes by developing a glow plug discretized model and a novel virtual gas sub-layer model. Glow plug discretized model can describe the transient heat transfer, and adequately represents the thin layers of heat penetration and the local temperature difference due to the cold gas jet impingement. The virtual gas sub-layer model considers complicated physical processes, such as chemical reaction, heat conduction, and mass diffusion within the virtual sub-layers without significantly increasing computational time and load. KIVA-3V CFD code was chosen to simulate the fluid flow. Since the KIVA-3V is designed specifically for engine research application with conventional liquid fuels, many modifications have been implemented to facilitate this research.

<p>Intermittent energy resources, including wind and solar power, continue to be rapidly added to the generation fleet domestically and abroad. The variable power of these resources introduces new levels of stochasticity into electric interconnections that must be continuously balanced in order to maintain system reliability. Energy storage systems (ESSs) offer one potential option to compensate for the intermittency of renewables. ESSs for long-term storage (1-hour or greater), aside from a few pumped hydroelectric installations, are not presently in widespread use in the U.S. The deployment of ESSs would be most likely driven by either the potential for a strong internal rate of return (IRR) on investment and through significant benefits to system reliability that independent system operators (ISOs) could incentivize.</p><p>To assess the potential of ESSs three objectives are addressed. (1) Evaluate the economic viability of energy storage for price arbitrage in real-time energy markets and determine system cost improvements for ESSs to become attractive investments. (2) Estimate the reliability impact of energy storage systems on the large-scale integration of intermittent generation. (3) Analyze the economic, environmental, and reliability tradeoffs associated with using energy storage in conjunction with stochastic generation.</p><p>First, using real-time energy market price data from seven markets across the U.S. and the physical parameters of fourteen ESS technologies, the maximum potential IRR of each technology from price arbitrage was evaluated in each market, along with the optimal ESS system size. Additionally, the reductions in capital cost needed to achieve a 10% IRR were estimated for each ESS. The results indicate that the profit-maximizing size of an ESS is primarily determined by its technological characteristics (round-trip charge/discharge efficiency and self-discharge) and not market price volatility, which instead increases IRR. This analysis demonstrates that few ESS technologies are likely to be implemented by investors alone.</p><p>Next, the effects of ESSs on system reliability are quantified. Using historic data for wind, solar, and conventional generation, a correlation-preserving, copula-transform model was implemented in conjunction with Markov chain Monte Carlo framework for estimating system reliability indices. Systems with significant wind and solar penetration (25% or greater), even with added energy storage capacity, resulted in considerable decreases in generation adequacy.</p><p>Lastly, rather than analyzing the reliability and costs in isolation of one another, system reliability, cost, and emissions were analyzed in 3-space to quantify and visualize the system tradeoffs. The modeling results implied that ESSs perform similarly to natural gas combined cycle (NGCC) systems with respect to generation adequacy and system cost, with the primary difference being that the generation adequacy improvements are less for ESSs than that of NGCC systems and the increase in LCOE is greater for ESSs than NGCC systems.</p><p>Although ESSs do not appear to offer greater benefits than NGCC systems for managing energy on time intervals of 1-hour or more, we conclude that future research into short-term power balancing applications of ESSs, in particular for frequency regulation, is necessary to understand the full potential of ESSs in modern electric interconnections.</p> / Dissertation

With increasing concerns about the harmful effects of conventional liquid fossil fuel emissions, natural gas has become a very attractive alternative fuel to power prime movers and stationary energy conversion devices. This research studies the injection and ignition numerically for natural gas (mainly methane) as a fuel applied to diesel engine. Natural gas injector and glow plug ignition enhancement are two of the most technical difficulties for direct injection natural gas engine design. This thesis models the natural gas injector, and studies the characteristics of the internal flow in the injector and natural gas jet in the combustion chamber during the injection process. The poppet valve model and pintle valve model are the first reported models to simulate the natural gas injector to improve the traditional velocity and pressure boundary conditions. This thesis also successfully models the glow plug assisted natural gas ignition and combustion processes by developing a glow plug discretized model and a novel virtual gas sub-layer model. Glow plug discretized model can describe the transient heat transfer, and adequately represents the thin layers of heat penetration and the local temperature difference due to the cold gas jet impingement. The virtual gas sub-layer model considers complicated physical processes, such as chemical reaction, heat conduction, and mass diffusion within the virtual sub-layers without significantly increasing computational time and load. KIVA-3V CFD code was chosen to simulate the fluid flow. Since the KIVA-3V is designed specifically for engine research application with conventional liquid fuels, many modifications have been implemented to facilitate this research.

This dissertation mainly addresses the synthesis of well-ordered mesoporous titania thin films by dip coating with PEO-PPO-PEO triblock copolymer surfactant template P123. Because P123 is composed of poly(ethylene oxide) [PEO] and poly(propylene oxide) [PPO] blocks, concentrations of ingredients are adjusted to tune the films’ wall thickness, pore size and mesophase. Structural changes are consistent with partitioning of species among PEO blocks, PPO blocks, and the PEO/PPO interface. Titanates localize near PEO and increase wall thickness (by 5 nm to 7 nm). Depending on aging temperature, PPG either swells the PPO cores (when it is hydrophobic) or introduces large (>200 nm) voids (when it is hydrophilic but phase separates during heating). 1-butanol localizes at the PEO/PPO interface to favor a 3D hexagonal mesostructure. In another approach, anodizing Ti foils yields vertically aligned titania nanotubes arrays with exceptional stabilities as anodes in lithium ion batteries; they maintain capacities of 130-230 mAhg-1 over 200 cycles. No microstructural changes are induced by battery cycling and good electrical contact is maintained. A diffusion induced stress model suggests that thin-walled nanotubes arrays should be stable under testing conditions, and that ordered hexagonal columnar pore arrays should have both high charge/discharge rates and low stress development.

There are many sources of free energy available in the form of heat that is often simply wasted for want of an effective way to convert it into useful energy such as electricity. The aim of this research project is to design and build a low temperature differential Stirling engine capable of generating electric power from heat sources such as waste hot water or geothermal springs. The engine that has been developed is a research prototype model of a new type of design featuring a rotating displacer which is actuated by a pair of stepper motors. The rotating displacer design enables the use of readily available and comparatively cheap and robust steam pipe as the housing for the engine, and it also avoids problems associated with sealing and heat exchange that would be present in a large engine of a more traditional configuration. Owing to the fact that this engine is a research prototype, it has the ability to have some of its critical operating parameters such as phase angle and stroke length adjusted to investigate the effects on performance. When the next phase of development takes place most of these parameters will be fixed at the optimum values which will make manufacture cheaper and easier. Unfortunately, construction of the prototype engine has not been completed at the time of writing so no power producing results have been achieved; however thorough results are presented on the operation of the control system for the stepper motors which actuate the displacer. Additionally, after a thorough history and background of Stirling engines was researched, the understanding gained of how these engines work has enabled a design process to take place which has hopefully led to a successful design. Analysis of various aspects of the engine have been carried out and results look promising for the engine to produce around 500 Watts of electrical power output whilst running on hot water up to around 90°C.

The concern over depleting fossil fuel resources and increasing greenhouse gas emissions has prompted the research into alternative and renewable energy resources. Bioethanol is seen as a potential alternative to petroleum fuels and is mainly produced from sugar and starch containing crops such as sugar cane and maize. In South Africa the use of maize for ethanol production has been prohibited due to food security concerns; therefore, alternative feedstocks need to be investigated. Tropical sugar beet, a new variety of sugar beet, is a potential alternative as it is able to grow in tropical and subtropical climates using much less water than sugar cane. The main objective of this study was to determine the potential of using tropical sugar beet for ethanol production. The study focused on the effects of dilution ratio, pH, yeast concentration and the addition of a nitrogen supplement on the ethanol yield. The maximum ethanol yield of 0.47 g.g–1 which is a conversion efficiency of 92% and a glycerol yield of 0.08 g.g–1 was obtained when no additional water was added to the juice. The best dilution ratio was found to be 1:4 which gave a maximum ethanol yield of 0.48 g.g–1 which is a conversion efficiency of 94% and a glycerol yield of 0.07 g.g–1. An ethanol yield of 0.48 g.g–1 which is a conversion efficiency of 94% was achieved at a yeast concentration of 5 g.L–1 after four hours of fermentation. Nitrogen supplements such as urea, peptone, yeast extract and ammonium sulphate were added during fermentation. The addition of a nitrogen supplement to fermentation had a positive effect on the ethanol yield. The maximum ethanol yield of 0.47 g.g–1 which is a conversion efficiency of 92% was achieved when urea was added to the fermentation. The addition of a nitrogen supplement also decreased the amount of glycerol formed from 0.15 g.g –1 to 0.08 g.g–1. Ammonium sulphate was chosen as the preferred nitrogen source as it is a simple component that can enter the cell directly. A maximum ethanol yield of 0.45 g.g–1 which is a conversion efficiency of 88%, was achieved when 750 mg N.L–1 ammonium sulphate was added. Adjusting the pH prior to fermentation had no real effect on the ethanol yield. The maximum ethanol yield of 0.45 g.g–1 was achieved at all the pH values investigated. Therefore the natural pH of the juice, or pH values between 4 and 5.5, could be used. Adjusting the pH was done to merely reduce the risk of contamination. The optimal fermentation parameters were found to be pH 4, yeast concentration 5 g.L–1 and a ammonium sulphate concentration of 750 mg N.L–1. At these conditions, a maximum ethanol of 0.45 g.g–1 was achieved. These results show that tropical sugar beet with a sugar content of approximately 21.8% (w.w–1) is a good feedstock for ethanol production in South Africa. / Thesis (M.Sc. Engineering Sciences (Chemical Engineering))--North-West University, Potchefstroom Campus, 2011.

In this research project, adsorption is considered in conjunction with the reverse water gas shift reaction in order to convert CO2 to CO for synthetic fuel production. If the CO2 for this process can be captured from high emitting industries it can be a very good alternative for reduced fossil fuel consumption and GHG emission mitigation. CO as an active gas could be used in Fischer-Tropsch process to produce conventional fuels. Literature review and process simulation were carried out in order to determine the best operating conditions for reverse water gas shift (RWGS) reaction. Increasing CO2 conversion to CO requires CO2/CO separation downstream of the reactor and recycling unreacted CO2 and H2 back into the reactor. Adsorption as a viable and cost effective process for gas separation was chosen for the CO2/CO separation. This was started by a series of adsorbent screening experiments to select the best adsorbent for the application. Screening study was performed by comparing pure gas isotherms for CO2 and CO at different temperatures and pressures. Then experimental isotherm data were modeled by the Temperature-Dependent Toth isotherm model which provided satisfactory fits for these isotherms. Henry law’s constant, isosteric heat of adsorption and binary mixture prediction were determined as well as selectivity for each adsorbent. Finally, the expected working capacity was calculated in order to find the best candidate in terms of adsorption and desorption. Zeolite NaY was selected as the best candidate for CO2/CO separation in adsorption process for this project. In the last step breakthrough experiments were performed to evaluate operating condition and adsorption capacity for real multi component mixture of CO2, CO, H2 in both cases of saturated with water and dry gas basis. In multi components experiments zeolite NaY has shown very good performance to separate CO2/CO at low adsorption pressure and ambient temperature. Also desorption experiment was carried out in order to evaluate the working capacity of the adsorbent for using in industrial scale and eventually temperature swing adsorption (TSA) process worked very well for the regeneration step. Integrated adsorption system downstream of RWGS reactor can enhance the conversion of CO2 to CO in this process significantly resulting to provide synthetic gas for synthetic fuel production as well as GHG emission mitigation.

The concern over depleting fossil fuel resources and increasing greenhouse gas emissions has prompted the research into alternative and renewable energy resources. Bioethanol is seen as a potential alternative to petroleum fuels and is mainly produced from sugar and starch containing crops such as sugar cane and maize. In South Africa the use of maize for ethanol production has been prohibited due to food security concerns; therefore, alternative feedstocks need to be investigated. Tropical sugar beet, a new variety of sugar beet, is a potential alternative as it is able to grow in tropical and subtropical climates using much less water than sugar cane. The main objective of this study was to determine the potential of using tropical sugar beet for ethanol production. The study focused on the effects of dilution ratio, pH, yeast concentration and the addition of a nitrogen supplement on the ethanol yield. The maximum ethanol yield of 0.47 g.g–1 which is a conversion efficiency of 92% and a glycerol yield of 0.08 g.g–1 was obtained when no additional water was added to the juice. The best dilution ratio was found to be 1:4 which gave a maximum ethanol yield of 0.48 g.g–1 which is a conversion efficiency of 94% and a glycerol yield of 0.07 g.g–1. An ethanol yield of 0.48 g.g–1 which is a conversion efficiency of 94% was achieved at a yeast concentration of 5 g.L–1 after four hours of fermentation. Nitrogen supplements such as urea, peptone, yeast extract and ammonium sulphate were added during fermentation. The addition of a nitrogen supplement to fermentation had a positive effect on the ethanol yield. The maximum ethanol yield of 0.47 g.g–1 which is a conversion efficiency of 92% was achieved when urea was added to the fermentation. The addition of a nitrogen supplement also decreased the amount of glycerol formed from 0.15 g.g –1 to 0.08 g.g–1. Ammonium sulphate was chosen as the preferred nitrogen source as it is a simple component that can enter the cell directly. A maximum ethanol yield of 0.45 g.g–1 which is a conversion efficiency of 88%, was achieved when 750 mg N.L–1 ammonium sulphate was added. Adjusting the pH prior to fermentation had no real effect on the ethanol yield. The maximum ethanol yield of 0.45 g.g–1 was achieved at all the pH values investigated. Therefore the natural pH of the juice, or pH values between 4 and 5.5, could be used. Adjusting the pH was done to merely reduce the risk of contamination. The optimal fermentation parameters were found to be pH 4, yeast concentration 5 g.L–1 and a ammonium sulphate concentration of 750 mg N.L–1. At these conditions, a maximum ethanol of 0.45 g.g–1 was achieved. These results show that tropical sugar beet with a sugar content of approximately 21.8% (w.w–1) is a good feedstock for ethanol production in South Africa. / Thesis (M.Sc. Engineering Sciences (Chemical Engineering))--North-West University, Potchefstroom Campus, 2011.

Immobilization of photosynthetic cultures has been used to generate biofuels and high value compounds through direct conversion of CO2 and water using sunlight. Compared with suspended cultures, immobilized bacteria can achieve much higher densities resulting in greater areal productivity. Limitations exist however, on the density that can be reached without compromising access to light and other nutrients. In this thesis an optofluidic approach to overcoming the challenge of light delivery to high density cultures of cyanobacteria is described and proof of concept experiments presented. This approach uses optical waveguides to deliver light to cells through bacterial interaction with the evanescent field and is tailored to meet each cell's need for light and nutrients. Experiments presented here demonstrate biofilm proliferation in the presence of evanescent fields. Illumination of surfaces by surface plasmon enhanced evanescent fields is also shown to be an effective and potentially useful technique to grow biofilms within optofluidic architectures.