The incorporation of active piezoelectric elements and fluidic components into micro-electromechanical systems (MEMS) is of great interest for the development of sensors, actuators, and integrated systems used in microfluidics. Low temperature cofired ceramics (LTCC), widely used as electronic packaging materials, offer the possibility of manufacturing highly integrated microfluidic systems with complex 3-D features and various co-firable functional materials in a multilayer module. It would be desirable to integrate high performance lead zirconate titanate (PZT) based ceramics into LTCC-based MEMS using modern thick film and 3-D packaging technologies. The challenges for fabricating functional LTCC/PZT devices are: 1) formulating piezoelectric compositions which have similar sintering conditions to LTCC materials; 2) reducing elemental inter-diffusion between the LTCC package and PZT materials in co-firing process; and 3) developing active piezoelectric layers with desirable electric properties. The goal of present work was to develop low temperature fired PZT-based materials and compatible processing methods which enable integration of piezoelectric elements with LTCC materials and production of high performance integrated multilayer devices for microfluidics. First, the low temperature sintering behavior of piezoelectric ceramics in the solid solution of Pb(Zr0.53,Ti0.47)O3-Sr(K0.25, Nb0.75)O3 (PZT-SKN) with sintering aids has been investigated. 1 wt% LiBiO2 + 1 wt% CuO fluxed PZT-SKN ceramics sintered at 900oC for 1 h exhibited desirable piezoelectric and dielectric properties with a reduction of sintering temperature by 350oC. Next, the fluxed PZT-SKN tapes were successfully laminated and co-fired with LTCC materials to build the hybrid multilayer structures. HL2000/PZT-SKN multilayer ceramics co-fired at 900oC for 0.5 h exhibited the optimal properties with high field d33 piezoelectric coefficient of 356 pm/V. A potential application of the developed LTCC/PZT-SKN multilayer ceramics as a microbalance was demonstrated. The final research focus was the fabrication of an HL2000/PZT-SKN multilayer piezoelectric micropump and the characterization of pumping performance. The measured maximum flow rate and backpressure were 450 μl/min and 1.4 kPa respectively. Use of different microchannel geometries has been studied to improve the pumping performance. It is believed that the high performance multilayer piezoelectric devices implemented in this work will enable the development of highly integrated LTCC-based microfluidic systems for many future applications.

Low temperature co-fired ceramic (LTCC) electronic packaging materials are applied for their electrical and mechanical properties, high reliability, chemical stability and ease of fabrication. Three dimensional features can also be prepared allowing integration of microfluidic channels and cavities inside LTCC modules. Mechanical, optical, electrical, microfluidic functions have been realized in single LTCC modules. For these reasons LTCC is attractive for biomedical microfluidics and Lab-on-a-Chip systems. However, commercial LTCC systems, optimized for microelectrics applications, have unknown cytocompatibility, and are not compatible with common surface functionalization chemistries. The first goal of this work is to develop biocompatible LTCC materials for biomedical applications. In the current work, two different biocompatible LTCC substrate materials are conceived, formulated and evaluated. Both materials are based from well-known and widely utilized biocompatible materials. The biocompatibilities of the developed LTCC materials for in-vitro applications are studied by cytotoxicity assays, including culturing endothelial cells (EC) both in LTCC leachate and directly on the LTCC substrates. The results demonstrate the developed LTCC materials are biocompatible for in-vitro biological applications involving EC. The second goal of this work is to develop functional capabilities in LTCC microfluidic systems suitable for in-vitro and biomedical applications. One proposed application is the evaluation of oxygen tension and oxidative stress in perfusion cell culture and bioreactors. A Clark-type oxygen sensor is successfully integrated with LTCC technique in this work. In the current work, a solid state proton conductive electrolyte is used to integrate an oxygen sensor into the LTCC. The measurement of oxygen concentration in Clark-type oxygen sensor is based on the electrochemical reaction between working electrode and counter electrode. Cyclic voltammetry and chronoamperometry are measured to determine the electrochemical properties of oxygen reduction in the LTCC based oxygen sensor. The reduction current showed a linear relationship with oxygen concentration. In addition, LTCC sensor exhibits rapid response and sensitivity in the physiological range 1─9 mg/L. The fabricated devices have the capabilities to regulate oxygen supply and determination of local dissolved oxygen concentration in the proposed applications including perfusion cell culture and biological assays.

Thesis (M.S.)--Ohio University, November, 2008. / Title from PDF t.p. Includes bibliographical references.

Thesis (Ph.D.)--University of Wyoming, 2009. / Title from PDF title page (viewed on May 21, 2010). Includes bibliographical references (p. 50-63).

The work presented in this thesis was carried out with a particular view of enhancing the of coal fired fluidised bed hot gas generator (HGG) at the Cantley factory of British Sugar. It covers combustion of coal and biomass and their blends also called co-firing in a fluidised bed combustor. Particularly it focuses on the effect of introduction of moisture as part of fuel or injection of water into the bed on the reduction of excess air to get a stable bed temperature. Although this thesis is focused on increasing the throughput of the HGG, the study has a broad application and can be beneficial in utilising relatively cheap, poor quality, unprepared biomass materials. The results of this study can be helpful in devising systems to deal with wastes from different industries in co-combustion with a fuel of higher calorific value such as coal. Thus the study will have dual impact on the industry; addressing waste management issues on one hand and producing useful energy on the other. This may contribute towards meeting the targets of Kyoto Protocol by reducing emissions of carbon dioxide (COi) as biomass is thought to be COa neutral. The fluidised bed at Cantley is used to dry animal feed and has a design capacity of 40 MW but due to limitations of flow of fluidising gases caused by high flow resistance through sparge pipes, the combustor is running under capacity. Consequently, some of the animal feed has to be dried by using expensive oil fired drier. In any combustion system excess air is used to control combustion temperature. In fluidised bed combustion excess air is used to control bed temperature. If the bed is cooled by other means the requirement of excess air can be reduced. This is the basic idea behind this study which is aimed at enhancing the capacity of the HGG by cooling the bed and thus reducing excess air requirements. The excess air thus spared can be used to combust more coal in the bed and thus will reduce dependence on oil fired dryer and will have financial benefits for British Sugar. Different fuels including wood pellets, wood chips and sugar industry by-products such as vinasse, raffinate and pressed pulp were fired/cofired with Thoresby coal in a fluidised bed test rig installed at the University of Glamorgan. The blends of wood chips and pressed pulp with coal are co-fired at different moisture contents. The tests were conducted at different thermal inputs at a wide range of excess air levels. Most of the work is focusedon the combustion of blends of coal and pressed pulp in different proportions. It was found that the maximum proportion of the pressed pulp in the blend with coal which could be burned successfully in the fluidised bed is 50%. During combustion of different coal-pulp and coal-wood chips blends it was found that excess air requirement is reduced by around 20% in comparison to coal only firing, over the range of the operating conditions tested. Because of the presence of potassium in pressed pulp, which could cause agglomeration during combustion in fluidised beds, longer term tests were carried out with 50/50 blend of coal and pulp. No signs of agglomeration were observed when the rig was fired for 8 days for almost 7 hours a day. However, Scanning Electron Microscopy (SEM) analyses of bed samples taken at the end of every day have shown the accumulation of potassium in the bed up to 1%. For comparison purposes tests were also carried out by co-firing coal with raffiante and vinasse and then it was observed that the bed defluidised relatively quickly, within 40 minutes of co-firing. Post experiment SEM analysis confirmed the accumulation of potassium in the bed which was found to be around 8% for raffinate and around 10% for the vinasse experiment. It was found that the pulp is difficult to deal with and particularly its feeding into the fluidised bed could be a potential problem. Therefore, injection of water into the bed, a relatively cheaper and adaptable option, was also investigated. It was found that emissions of carbon monoxide due to incomplete combustion or water gas shift reaction would not be a problem as long as the bed temperature is controlled above 800 °C. It was found that the injection of water at a rate of 4.5 1/h into the bed fired at 17 kW reduced the air flow requirement by around 7.5 m3/h which corresponds to a reduction of almost 20% which agrees with the finding with coal-pulp blends co-firing. This excess air can be used to burn around 5 kW equivalent of more coal and thus result in an increase in the thermal capacity by around 30%. Therefore, it may be possible to enhance the thermal capacity of the HGG at Cantley by 30% by injecting water into the bed or by co-firing coal and pulp.

M.Ing. / This dissertation deals with the implementation of a Reliability Basis Optimisation Process for Eskom’s fossil fired Power Stations. This study comes about as a result of the situation that Eskom currently finds itself in. Eskom currently has a generating capacity of 41 000MW. It supplies 95% of South Africa’s power requirements and 45% of Africa’s power requirements. With the unprecedented economical growth that South Africa has experienced in the last five years, coupled with the economic recession of 2008/2009, Eskom has found itself in a precarious position in terms of power delivery. Eskom’s request for a 45% tariff increase in its Multi Price Determination (MYPD2) application to NERSA was turned down and a figure of 25% was awarded. Eskom’s current reserve margin is currently lies as less than 10%. With the funding restrains it now becomes difficult to replace machinery as it fails. The focus now shifts of carrying out effective maintenance. Eskom established the Asset Management Department with a view to ensure that the right maintenance was carried out. Within the Asset Management Department the Reliability Basis Optimisation (RBO) Process was established. The aim of the RBO stream is to improve the reliability and availability of the fossil fired Power Station. This dissertation looks at how the RBO process was developed and rolled out to the Power Stations. It also gives a brief overview of the Asset Management Improvement process to which the RBO process is the backbone.

M.Sc. / This project considers the feasibility of using heated cooling water from coal-fired power stations within Eskom for the culturing of C/arias gariepinus (Sharptooth catfish) and Oreochromis mossambicus (Mozambique tilapia). The work includes: an overview of world wide trends in power plant thermal effluent aquaculture, the identification of suitable power stations for aquaculture, long term monitoring of the physical and chemical characteristics of the cooling water at selected power stations, including the effects of the cooling water on the growth response, food conversion, condition factor, survival rate and suitability for human consumption of the aforementioned fish species reared in the cooling water at Matla and Kriel Power Stations.

M.Ing. / Water gives life. It waters the fields of farmers; it nurtures the crops and stock of rural communities; it provides recreation for our children, our friends, our families; it supports our power generation, our mines, our industry, and the plants and animals that make up ecosystems. Water is the key to development and a good quality of life in South Africa. South Africa's water belongs to its people. It is the task of the South African Government to care for this water, to seek its fair distribution, and to facilitate its wise use for, amongst other things, social and economical development. Issues such as water resource management, use, protection, water services, etc., are presently governed by a number of policies, acts and regulations. All South Africans has a responsibility regarding the management of the country's resources. The supply of water to its entire people makes it extremely important to optimise the use of this scarce source. Access to water and water availability remains a key factor in ensuring the sustainability of development in Southern Africa. The coal fired power industry is a major user of natural resources; coal for fuel and water for steam generation as well as the cooling systems. It is estimated that 1.5% of the water abstracted in South Africa is used for power generation. The power industry receives its water mainly as abstraction from surface impoundments in the form of rivers and dams. Eskom, as a strategic user of water, is mindful of the importance of water to its business, as well as the development of the country. In addition to the interests of the government as the shareholder, Eskom recognises the legitimate interests, as stakeholders, of specific government departments, employees, consumers, suppliers, investors and lenders of capital, rating agencies, the media, policy and regulatory bodies, trade unions, non-governmental groups and local communities in its affairs. Eskom needs to ensure, through an effective water management strategy, that water is used wisely and effectively and that Eskom's impact on local water resources (surface and underground) is minimised. Eskom therefore has to manage water resources in a manner that will sustain the ecological integrity, support social development and ensure economic growth. Eskom has undertaken to benchmark the power generation industry, in co-operation with the DW AF, in a project aimed at developing the principles of water conservation and water demand management. In order to effectively manage water quality and quantity at Eskom's power stations, and to show Eskom's commitment with regard to water conservation and use, Eskom has compiled its own water and environmental policies.

Online monitoring supports plant reliability and performance management by providing real time information about the condition of equipment. However, the intricate geometries and harsh operating environment of coal fired power plant boilers inhibit the ability to do online measurements of all process related variables. A low-cost alternative lies in the possibility of using knowledge about boiler operation to extract information about its condition from standard online process measurements. This approach is evaluated with the aim of enhancing online condition monitoring of a boiler’s convective pass heat exchanger network by respectively using a soft sensor and a data-driven method. The soft sensor approach is based on a one-dimensional thermofluid process model which takes measurements as inputs and calculates unmeasured variables as outputs. The model is calibrated based on design information. The data-driven method is one developed specifically in this study to identify unique fault signatures in measurement data to detect and quantify changes in unmeasured variables. The fault signatures are initially constructed using the calibrated one-dimensional thermofluid process model. The benefits and limitations of these methods are compared at the hand of a case study boiler. The case study boiler has five convective heat exchanger stages, each composed of four separate legs. The data-driven method estimates the average conduction thermal resistance of individual heat exchanger legs and the flue gas temperature at the inlet to the convective pass. In addition to this, the soft sensor estimates the average fluid variables for individual legs throughout the convective pass and therefore provides information better suited for condition prognosis. The methods are tested using real plant measurements recorded during a period which contained load changes and on-load heat exchanger cleaning events. The cleaning event provides some basis for validating the results because the qualitative changes of some unmeasured monitored variables expected during this event are known. The relative changes detected by both methods are closely correlated. The data-driven method is computationally less expensive and easily implementable across different software platforms once the fault signatures have been obtained. Fault signatures are easily trainable once the model has been developed. The soft sensors require the continuous use of the modelling software and will therefore be subject to licencing constraints. Both methods offer the possibility to enhance the monitoring resolution of modern boilers without the need to install any additional measurements. Implementation of these monitoring frameworks can provide a simple and low-cost contribution to optimized boiler performance and reliability management.

Hospitals are one of the most energy consuming centers in which thermal energy is utilized for different medical equipments and others. Sterilizers, laundry and kitchens are the main thermal energy utilizing equipments. In addition, large amount of hot water is utilized mainly for showering and dish washing. The main sources of this thermal energy are fossil fuel for oil fired boilers and solar irradiation for solar thermal steam generation system. This project aims in analyzing the Technical performance of parabolic trough steam generation and oil fired boiler steam generation system for Black lion general specialized hospital which is located in Addis Ababa and to perform economic assessment on both systems so as to make comparison test. The result from technical feasibility study shows the parabolic trough can meet the steam demand of the hospital at the required time, more than 8hour per day, as the hospital currently require steam for different activities during the day time for 8hour per day. During cloudy day the conventional back up steam generation system will meet the daily demand for few days of the year. The economic assessment result shows that although the initial investment of concentrated solar steam generation is high as compared to convention steam generation system, the reverse is observed in operation and maintenance cost, resulting solar thermal steam generation break even (payback) to occur early, after 7 year the system let to operate over the conventional oil fired steam generation. In addition the levelized cost of energy for concentrated solar steam generation is found to be 58% higher than conventional steam generation.   Hence, the result shows that parabolic trough is found to be more economical for steam generation than oil fired boiler. If solar thermal steam generation (parabolic through) is implemented, the fuel consumption and operational cost of the boiler can be reduced appreciably.