Approximately 35% of the population of the Navajo Nation does not have direct access to the electric grid and public water supply. Tribal members haul their potable and livestock water from public water systems that are located great distances from their homes. The Navajo Nation Solar Desalination Research Pilot Demonstration Project is designed to provide residents affordable livestock water. The same technology can later be adopted to provide potable water. The project has deployed an off-grid, prototype water purification unit at a demonstration site north of Leupp, AZ utilizing membrane distillation (MD) technology. A second prototype for the same purposes utilizing nanofiltration (NF) membrane technology has been designed, built, and operated at The University of Arizona. Through experimentation I confirmed information provided the manufacturer of the NF membrane, calculated the production rate to be 636 gallons per day, and calculated the cost of desalinated water to be $0.003 per gallon. Both systems use solar energy to desalinate brackish ground water and the second prototype will later be deployed at the same site for side-by-side comparison. A critical part of the project is the development of technology transfer methods that will help the community take ownership of the project. To accomplish this goal I have written a comprehensive manual that will be given to the Navajo Department of Water Resources. The demonstration site will act as an applied research site for investigation, demonstration, and training related to sustainable water and energy systems designed to address the needs of remote, rural communities in arid and semi-arid regions. The aim is to inform a regional plan for Southwestern Navajo Nation Chapters to address chronic water and energy shortages, demonstrate renewable energy application for water treatment of brackish ground water, evaluate trade-offs in energy and water supplies, and foster community development. The research and demonstration site has been developed by an interdisciplinary and collaborative effort between the Bureau of Reclamation, Apex Applied Technology, Inc., and The University of Arizona.

A prototype solar desalination system (SODESAL) with a parabolic-trough solar concentrator (PTSC) and evacuated tube was designed and analyzed to determine the solar thermal capabilities for small-scale distillation and energy generation. A proof-of-concept study verified that distillation is possible with the system as designed, however a rupture occurred in the copper heat-pipe heat exchanger due to overheating. The internal temperatures of an aluminum heat transfer fin were measured inside an evacuated tube typically used in solar water heater systems to understand the lateral heat distribution and identify possible causes of the rupture. Solar radiation was measured for both the summer and winter solstices to understand the relationship between incident solar radiation and the potential freshwater yield of the system. The lateral heat distribution of the AHTF is dependent upon the PTSC’s solar incident angle. A consistent lateral heat distribution occurred across the AHTF approximately 40 mins after solar noon. The temperature difference between each end of the AHTF can exceed over 225 °C leading up to and following solar noon when the PTSC was set at a static slope. The SODESAL system’s future applications, system improvements and additional research are also discussed along with the capability of small-scale CSP systems.

Water is a vital element of agriculture. Almost 75% of the world's water resources are used for farm irrigation. Using greenhouses in agriculture provides a good environment for plant growth and reduces water consumption. Desalination to obtain freshwater from seawater or brackish water has been used in the arid costal regions and areas that have encountered water shortages. Solar desalination systems integrated into greenhouses have been considered for fresh water production to satisfy their water demand. Two main types of greenhouse integrated desalination systems are used, namely, solar stills and greenhouse-integrated humidification-dehumidification type solar systems. The main objective of this project is to carry out a thermodynamic analysis and a comparison of solar stills and humidification-dehumidification type desalination units. The basic principles, components, types, advantages and disadvantages of solar stills and humidification-dehumidification type greenhouse integrated desalination systems were investigated in detail. A conventional single basin type solar still that includes a basin and a symmetrical tilted condensing cover (greenhouse roof), and a humidification- dehumidification desalination unit that consists of two evaporators and one condenser were selected for detailed analysis. In order to carry out the thermal analysis, some important data such as plant transpiration and evaporation, solar radiation and indoor conditions of the greenhouse were determined. The thermal analysis was based on tomato production. Typical year ambient air temperature, relative humidity, and wind velocity values were taken from TRNSYS 16 for Adelaide conditions. In order to provide a good environment for the tomato crops, the internal conditions of the greenhouse were selected in the range 15-29oC temperature and 60-80% relative humidity. Detailed mathematical thermal models of both conventional solar stills and the new humidification-dehumidification type systems were simulated and the fresh water production of both systems was evaluated by means of MATLAB 7.8. The results were compared with previous experimental results. The results demonstrated that even if the whole roof area is used, the required fresh water supply cannot be produced in the months of May, June and July by the simple solar still system, whereas adequate amounts of fresh water can be produced throughout the year by means of humidification-dehumidification type system. On the other hand, the annual water production of the simple solar still system and humidification-dehumidification type system were determined as 308.5 and 260 m3/year respectively. The thesis also considers the option of water storage for providing water requirement of the greenhouse plants. The parameters that affect the fresh water requirement of the both systems were also considered and their impact evaluated. The effects of the desalination system on the internal environment of the greenhouse were also considered. It was revealed from the results that the use of the solar still system during the period from April to October causes unsuitable greenhouse conditions for the greenhouse crops whilst appropriate conditions for the greenhouse crops were achieved throughout the year in the case of the humidification-dehumidification type system. On these and other grounds, the humidification-dehumidification type system was found more suitable for the given greenhouse and climatic conditions. / Thesis (MEng(MechanicalEngineering)--University of South Australia, 2010

An experimental characterisation of a pre-commercial spiral wound permeate gap membrane distillation module was carried out to test its performance at different operating conditions for the purpose of seawater desalination. The experimental setup consisted of a flat plate solar collector field indirectly coupled to the permeate gap membrane distillation module via an inertia tank. The operating parameters varied were the condenser inlet temperature (from 20 °C to 30 °C), evaporator inlet temperature (from 60 °C to 80 °C) and seawater feed flow rate (from 200 l/h to 400 l/h). Within this operational boundary, it was found that the maximum permeate/distillate flux was 4.135 l/(h∙m2) which equates to a distillate production/flow rate of close to 21.3 l/h. The maximum potential distillate production rate is expected to be significantly higher than this value though as the maximum manufacturer specified feed flow rate is 700 l/h and the maximum evaporator inlet temperature is rated at 90 °C. Both these parameters are positively related to the distillate production rate. The minimum specific thermal energy consumption was found to be 180 kWh/m3. A mathematical model of the overall system was developed, and experimentally validated, to mathematically describe the coupling of the membrane distillation module with a solar collector field. The effectiveness of internal heat recovery of the membrane distillation module was found to be an accurate and simple tool to evaluate the thermal energy demand of the distillation process at a given set of operation parameters. The mathematical model was used to further investigate the experimental findings and provide insights into the operational dynamics of the membrane distillation module. It was also used to determine some external conditions required for steady state operation, at a given distillation operating point, such as the minimum solar irradiation required for operation and the auxiliary cooling required in the solar collector loop for maintaining steady state conditions. Finally, general guidelines are provided toward better operational practices to improve the coupling of a solar thermal collector unit/field with a membrane distillation system using a storage tank or inertia tank.

CoordenaÃÃo de AperfeiÃoamento de NÃvel Superior / This work presents two new prototypes of a circular desalinator operation in a solar cooker for indirect heating. The first prototype, called Type A, produces desalinated water from brackish water deposited in the pan solar cooker. In the second prototype, the Type B, the brackish water pan is used only as a means of transfering heat to the first tray tower desalination. These prototypes were fabricated and tested in LESGN (Solar Energy Laboratory and Natural Gas). Its structure consists of stainless steel plates, trays with circular and inclined downwards (with circular trays to facilitate the flow of condensed water) and "pipes" (that harvest desalinated water and take out the stages and side rails, harvesting the water that condenses the side walls). The desalting tower was formed by a set of trays to facilitate the handling and operation. The experiments were conducted between 7.00am and 5.00pm and the maximum number of stages was three. Experiments with 2 and 3 stages confirmed the heat recovery process, in other words, the repeated use of the heat stored in the desalinated water in a lower stage by stage above. The experimental results showed that the maximum production were daily for the Type A, 4.72 L with 3 stages, and the desalinator Type B 3.50 L also with 3 stages. It was found that the efficiency of desalination type A was greater than that of Type B, which explains why Type B has a further resistance to heat transfer. On the other hand, Type B prototype allows continued operation of the desalination tower, not requiring the dismantling after each emptying process of the water in the pan / Este trabalho apresenta dois novos protÃtipos de um dessalinizador circular para operaÃÃo em um fogÃo solar de aquecimento indireto. O primeiro protÃtipo, denominado Tipo A, produz Ãgua dessalinizada a partir da Ãgua salobra depositada na panela do fogÃo solar. No segundo protÃtipo, o Tipo B, a Ãgua salobra da panela à usada apenas como meio de transferÃncia de calor para a primeira bandeja da torre de dessalinizaÃÃo. Estes protÃtipos foram fabricados e testados no LESGN (LaboratÃrio de Energia Solar e GÃs Natural). Sua estrutura à formada por chapas de aÃo inoxidÃvel com bandejas circulares e inclinadas para baixo, com bandejas circulares para facilitar o escoamento da Ãgua condensada, âcachimbosâ, que colhem a Ãgua dessalinizada e levam para fora dos estÃgios e calhas laterais, que colhem a Ãgua que condensa pelas paredes laterais. A torre de dessalinizaÃÃo foi formada por um conjunto de bandejas para facilitar o manuseio e operaÃÃo. Os experimentos foram realizados entre 7 e 17 hs e o nÃmero mÃximo de estÃgios foi trÃs. Os experimentos com 2 e 3 estÃgios confirmaram o processo de recuperaÃÃo de calor, ou seja, a utilizaÃÃo repetida do calor armazenado na Ãgua dessalinizada em um estÃgio inferior pelo estÃgio superior. Os resultados experimentais mostraram que as mÃximas produÃÃes diÃrias foram, para o Tipo A, de 4,72 L com 3 estÃgios, e para o dessalinizador Tipo B, 3,50 L com 3 estÃgios. Verificou-se que a eficiÃncia do dessalinizador Tipo A era superior ao do Tipo B, o que se explica por o Tipo B ter uma resistÃncia a transferÃncia de calor a mais. Por outro lado, o protÃtipo Tipo B permite uma operaÃÃo continuada da torre de dessalinizaÃÃo, nÃo sendo necessÃrio a sua desmontagem apÃs cada esvaziamento da Ãgua na panela.

Seawater desalination plays an important role when fighting the freshwater scarcity that many places around the world are currently facing. The increasing need for desalinated water is followed by a high energy demand. It is therefore essential that an expansion of desalination capacity is accompanied by a parallel use of renewable energy sources in this process. This thesis presents a techno-economic study on a reverse osmosis (RO) desalination plant, with a nominal power consumption of 15 MW, that is powered by a concentrated solar power (CSP) plant combined with a photovoltaic (PV) power plant, in Kuwait. The main aim of this thesis was to find which system designs would give the lowest global warming potential and levelized cost of the desalinated water. In addition, it has been investigated how electricity price and emission allowance cost could make a solar power plant competitive to the grid. For this purpose, some components in the whole system were simulated using System Advisor Model and Engineering Equation Solver. With the results obtained from the simulations, a dynamic model of the whole system was developed in MATLAB, Simulink where simulations were done for a typical meteorological year in Shagaya, Kuwait. Both on-grid and off-grid systems were considered.   In the on-grid case, the lowest cost of water was obtained with only PV (ca 0.65 USD/m3) and this could reduce carbon emissions by 30 % compared to only using the grid. Combining CSP and PV could reduce the carbon emissions by 85 % but with a 35 % increase in water cost. It was found that an electricity price of 0.1 USD/kWh or an emission allowance cost of 70 USD/tCO2-eq would make a CSP + PV plant competitive to the grid. These results indicate that the choice of which system is best for powering an on-grid RO plant depends on how the environmental and economic factors are prioritised. In the case of the off-grid system, both the lowest cost of water (ca 0.9 USD/m3) and the highest capacity factor were obtained with a CSP + PV plant with 16 h of storage, a solar multiple of 3 and a PV capacity of 28 MW.

As the world population grows, a persistent pressure on natural resources remains. Resource requirements have extensively expanded due to industrialization. Several technological advancements continually aim to alleviate these resource shortages by targeting existing shortcomings in effective and efficient material design. Practical, high-performing, and economical materials are needed in several key application areas, including energy storage, energy harvesting, electronics, catalysis, and water purification. Further development into high-performing and economical materials remain imperative. Innovators must seek to develop technologies that overcome fundamental limitations by designing materials and devices which address resource challenges. Carbon serves as a versatile material for a wide range of applications including purification, separation, and energy storage owing to excellent electrical, physical, and mechanical properties. One-dimensional (1D) carbon fiber in particular is renowned for excellent strength with high surface-to-volume ratio and is widely commercially available. Although an exceptional candidate to address current energy and environmental needs, carbon fibers require further investigation to be used to their full potential. Emerging strategies for carbon fiber design rely on developing facile synthetic routes for controlled carbon structures. The scientific community has shown extensive interest in porous carbon fabrication owing to the excellent performance enhancement in separation, filtration, energy storage, energy conversion, and several other applications. This dissertation both reviews and contributes to the recent works of porous carbon and their applications in energy and environmental sciences. The background section shows recent development in porous carbon and the processing methods under investigation and current synthetic methods for designing porous carbon fibers (PCF). Later sections focus on original research. A controlled radical polymerization method, reversible addition-fragmentation chain transfer (RAFT), enabled a synthetic design for a block copolymer precursor, poly(methyl methacrylate) (PMMA) and polyacrylonitrile (PAN). The block copolymer (PMMA-b-PAN) possesses a unique microphase separation when electrospun and develop narrowly disperse mesopores upon carbonization. The PMMA and PAN domains self-assemble in a kinetically trapped disordered network whereby PMMA decomposes and PAN cross-links into PCF. The initial investigation highlights the block copolymer molecular weight and compositional design control for tuning the physical and electrochemical properties of PCF. Based on this study, mesopore (2 – 50 nm) size can be tuned between 10 – 25 nm while maintaining large surface areas, and the PAN-derived micropores (< 2 nm). The mesopores and micropores both contribute to the development of the unique hierarchical porous carbon structure which brings unprecedented architectural control. The pore control greatly contributes to the carbon field as the nano-scale architecture significantly influences performance and functionality. The next section uses PCF to clean water sources that are often tainted with undesirable ions such as salts and pollutants. Deionization or electrosorption is an electrochemical method for water purification via ion removal. I employed the PCFs as an electrode for deionization because of their high surface area and tunable pore size. Important for deionization, the adsorption isotherms and kinetics highlight the capacity and speed for purification of water. I studied PCF capacitive filtration on charged organic salts. Because PCF have both micropores and mesopores, they were able to adsorb ions at masses exceeding their own weight. The PFC adsorption efficiency was attributed to the diffusion kinetics within the hierarchical porous system and the double layer capacitance development on the PCF surface. In addition, based on the mechanism of adsorption, the PCFs showed high stability and reusability for future adsorption/desorption applications. The PCF performance as an electrosorption material highlights the rational design for efficient electrodes by hierarchical interconnected porosity. Another application of PFCs is updating evaporative desalination methods for water purification. Currently distillation is not widely used as a source of potable water owing to the high cost and energy requirement. Solar desalination could serve as a low-cost method for desalination; however, the evaporation enthalpy of water severely limits practical implementation. Here I apply the pore design of PCF as a method for water nano-confinement. Confinement effects reduce water density and lowers evaporation enthalpy. Desalination in PCF were studied in pores < 2 nm to 22 nm. The PCF pore size of ~ 10 nm was found to be the peak efficiency and resulted in a ~ 46% reduction in enthalpy. Interestingly, the PCF nano-confinement also contributed to the understanding in competing desorption energy for evaporation in micropores. The pore design in PCF also shows confinement effects that can be implemented in other environmental applications. Lastly, the block copolymer microphase morphology was explored in a vapor induced phase separation system. The resulting PCF properties showed a direct influence from the phase separation caused by nonsolvent. At low nonsolvent vapor, a disordered microphase separation occurred, however upon application of nonsolvent vapor, the polymer chains reorganized. The reorganization initially improved mechanical properties by developing more long-range ordered graphic chains in the PAN-derived carbon. However, at higher nonsolvent vapor concentrations, the fibers experienced polymer precipitation which resulted in bead and clump formation in the fiber mats. The beads and clumps lowered both mechanical properties and electrochemical performance. The vapor induced phase separation showed a method for enhancing mechanical properties without compromising electrochemical performance in flexible carbon fibers. / Doctor of Philosophy / Nanomaterials possess mechanical, physical, and electrical properties to address important growing demands for precious resources such as clean water and energy. Many advancements in nanomaterials focus on improving fine-tune architectures which facilitate efficiency in composites, filtration systems, catalytic systems, energy storage devices, and electronics. Carbon material has remained a valuable candidate in these fields owing to its abundancy economical cost, and excellent properties. Several carbon forms provide unique characteristics including 0D dots, 1D fibers, 2D sheets, and 3D monoliths. Of these, 1D fibers possess excellent strength, resiliency, and conductivity and have been commercially employed in modern automotive, airplanes, membranes, and conductors. However, traditional carbon fiber fabrication does not match the growing needs in performance. Therefore, in this dissertation I explore the design and processing of carbon fibers for controlled architectures. These designs were then systematically studied in filtration systems, solar desalination, and flexible electronics. Block copolymers provide a new way to combine polymers for drastically new materials and effects. Firstly, I conducted a comprehensive study on the synthesis and composition of this block copolymer which laid the foundation for future carbon fiber design. The polymer consists of two chains – one chain to develop carbon structures upon heating; the second which decomposes into pores upon heating. Therefore, with these two chains, a highly porous carbon fiber can be created. The reaction I studied could mostly be controlled with time to change the length of each chain. Ultimately, the pore size and surface area depend on the relative lengths of each chain. Future studies, including ones in this work, could therefore tune pore size and surface area for many applications. Carbon fibers with graphitic structure are inherently conductive and thereby attract charged molecules in a solution. Diffusion and capacity serve as major factors in these types of systems. With the aforementioned control of the carbon fibers a diffusion study was conducted with charged pollution ions. Owing to the conductive nature, a voltage supply was attached to the fibers, which would adsorb ions electrostatically, termed "electrosorption". The electrosorption performance within the carbon fibers elucidated the interconnected porous structure and how ions orientate themselves along the surface of the fibers. In addition, with the development of ion orientation along the surface of the fibers, a greater than 1:1 ratio of carbon weight to ion weight adsorbed developed owing to the diffusion and ion stacking capabilities. Additionally, the study provides deeper investigation into movement of ions within confined nano-porous material. The ever-growing need for renewable resources such as fresh water has pressured development into more efficient material. Solar desalination has attractive qualities which makes it a focus for micro-scale studies. One of the major limitations lies in the high energy input change liquid water into vapor. At 100 °C for boiling, desalination lacks sufficient efficiency for large-scale applications in evaporation. However, by utilizing nano-scale material, the fundamental properties of water can be altered. The carbon fibers were then created with various nano-pore sizes which revealed nano-confinement effects when subject to solar heating. With the shrinking of pore sizes, the density of water also decreased. A lower density means less energy was required to convert water from a liquid to a vapor state. The carbon fibers helped reveal real applications into confinement effects on water based on pore size. Apart from just desalination, this means future environmental application can utilize this knowledge for more effective and smart designs. The carbon fibers outstanding electrical and mechanical properties have spurred research and development since the mid-1900s. Since then, carbon fiber technologies have grown from facile and efficient productions means, to high end, high performance smart design. The work presented here furthers two major components: first, the high-performance design of porous carbon fiber; second, the fundamental principles in nano-material properties and their applications. By first constructing a design of polymer synthesis and then subsequent studies, development of nano-porous carbon energy progresses knowledge on smart and efficient designs. These materials provide a platform for future energy and environmental sciences.

Maintaining a constant supply of clean drinking water is among the most pressing global challenges in our time. About one-third of the population is affected by the water scarcity and it can only get worse with climate change, rapid industrialization, and the population growth. Even though nearly 70 percent of the planet is covered by water, the consumable freshwater content is only 2.5 percent of it. Unfortunately, the accessible portion of it is only 1 percent. Even so, most of the freshwater bodies are choked with pollution. Considering the vast availability of saline water on the planet and the increasing wastewater generation, seawater desalination, and wastewater treatment and recycling seem to have the potential to address current water-related issues. Therefore, it is necessary to find efficient techniques for seawater desalination and wastewater treatment. The use of nanostructured materials for these applications is becoming a popular approach due to the unique chemical and physical properties they possess compared to bulk materials Solar energy is the cleanest and most abundant renewable natural resource available. Materials for solar photothermal energy conversion are highly sought after for their cost savings, clean environment, and broad utility in providing water heating and/or steam for many applications including domestic water heating and solar-driven desalination. Extensive research efforts have been made to develop efficient solar absorbers with characteristics such as low weight, low thermal conductivity, broad solar absorption and porosity to be able to float on water to provide more efficient and cost-effective solar steam generation systems. Metal NPs have been proposed to take advantage of the high efficiency of the photothermal energy conversion associated with surface plasmon resonance absorption. Nanostructured carbon-based materials such as graphene oxide, carbon nanotubes, carbonized biomass are also in use due to their excellent photothermal energy conversion ability over the range of the visible and near infra-red region of the electromagnetic spectrum. In this dissertation, five projects based on the utility of nanostructured materials for desalination, photocatalysis and water treatment will be discussed. The first three projects involve the fabrication and design of plasmonic and carbon-based photothermal materials for applications in solar steam generation, water desalination, and wastewater treatment. In the fourth project, a unique shape of ZnO nanostructure was synthesized for photodegradation of organic dyes in industrial wastewater. The final project demonstrates the shape-controlled synthesis of iron carbide nanostructures and composite materials of aminated graphene oxide for the removal of Cr(VI) from wastewater.

In this thesis, experimental and numerical studies have been carried out to investigate the performance of a solar desalination system working on humidification-dehumidification principle under the climatological conditions of Ankara, Turkey. The desalination unit was configured mainly by a double-pass flat plate solar air heater with two glass covers, pad humidifier, storage tank and dehumidifying exchanger. The system used in this work is based on the idea of closed water and open air cycles. A computer simulation program based on the mathematical model was developed by means of MATLAB software to study the effect of different environmental, design, and operational parameters on the desalination system productivity. In this simulation program, the fourth order Runge-Kutta method was used to solve the energy balance equations simultaneously and numerically. In order to compare the obtained theoretical results with experimental ones and validate of the developed mathematical model of the system, an experimental study has been carried out. For that, an experimental set-up was designed, constructed and tested at the solar house of the Mechanical Engineering Department of METU. In addition, the existing solar desalination system was integrated with an evacuated tubular solar water heater unit (closed water circulation) and performance of the system has been studied experimentally.

Desalination is one of the proposed methods to meet the ever increasing water demands. It can be subdivided into two broad categories, thermal based desalination and electricity based desalination. Multi-effect Distillation (MED), Multi-Stage Flashing (MSF), Membrane Distillation (MD) fall under former and Reverse Osmosis (RO), Electro-Dialysis (ED) fall under later. MD offers an attractive solution for seawater as well as brackish water distillation. It shows highly pure yields, theoretically 100% pure. The overall construction of a MD unit is way simpler than any other desalination systems. MD is a thermally driven diffusion process where desalination takes places in the form of water vapor transport across the membrane. It has low second law efficiency due to parasitic heat losses. The objective of the first part of the investigation is to thoroughly analyze a Direct Contact Membrane Distillation (DCMD) system from the view point of yield and exergy. The insights from exergy analysis are used in a design study, which is used for performance optimization. The first part concludes with a design procedure and design windows for large scale DCMD construction. In the second part of the investigation, focus is moved to waveguide solar energy collector. The idea behind an ideal waveguide is to reduce the complexity of modeling solar energy collection. The mathematical model provided in this analysis can be extended to a family of non-imaging optics in solar energy and serves as a benchmarking analysis tool. A waveguide is suitable for low temperature operations due to limitations on maximum continuous temperature of operation. Thus, it becomes an ideal solution for DCMD applications. A levelized cost analysis is presented for a waveguide powered DCMD plant of a 30,000 capacity. A combination of waveguide and DCMD shows levelized cost of water at $1.80/m³, which is found to be lower than previously reported solar desalination water costs. / Master of Science