CoordenaÃÃo de AperfeÃoamento de Pessoal de NÃvel Superior / A solar desalination system basically has two components: the heating unit (solar collectors) and the desalination unit (tower). Among its main advantages, this device does not need electrical power to operate, since it is driven by thermosiphon. In its operation, brackish water is heated and it evaporates. The evaporated vapor rises and hits the coller walls of the above tray, where it condensates and drains through a specially designed geometry, structure to be finally by in a set of gutter. The already demineralized water flows through a main channel where it is stored in a container, outside the desalination tower. The resulting water from this process is pure and free from contamination, either microorganisms or salt. This study analyzes the performance of a desalination system with a desalination tower and a set of three solar collectors. The heat transfer medium between the collector and the tower was thermal oil flow, Lubrax Utile OT-100. The experimental results demonstrate the operation of this type of desalinator, since ideal conditions for its correct functioning was only achieved after the installation of a positive displacement pump, which that promoted the oil circulation. Thermocouples installed in the stages of tower registered the temperature increase throughout the day. Peaks of 77 ÂC were measured in the storage tank of the tower. The mean values of production per day were 25 liters of desalinated water with an average conductivity always less than 10 μS / cm Â, representing a salt removal efficiency greater than 99%. In performance calculation, the best result was obtained when the pumping system was combined with the use of a solar reflector, achieving GOR value of 2.85. / Um dessalinizador solar possui basicamente duas unidades: a unidade de aquecimento (coletora) e a unidade de dessalinizaÃÃo (torre). Apresenta entre suas principais vantagens o fato de nÃo precisar de energia elÃtrica para seu funcionamento, pois à acionada por termossifÃo. A operaÃÃo se dà pelo aquecimento da Ãgua salobra atà que esta comece a evaporar. O vapor, ao subir e encontrar com uma superfÃcie com temperatura inferior, condensa e escorre atravÃs de estruturas em uma geometria especialmente projetada para este fim e sà entÃo à coletada por um sistema de calhas. A Ãgua jà desmineralizada segue por uma calha principal onde escorre e à armazenada em um recipiente, jà fora da torre de dessalinizaÃÃo. A Ãgua resultante desse processo à praticamente pura e isenta de contaminaÃÃo, tanto por microrganismos como por sais e outros contaminantes. O presente trabalho analisa o desempenho do dessalinizador composto por uma torre de dessalinizaÃÃo e um conjunto composto por trÃs coletores solares acionados por Ãleo tÃrmico Lubrax Utile OT-100. Os resultados experimentais comprovam o funcionamento desse tipo de dessalinizador, visto que condiÃÃes ideais para seu correto funcionamento sà foram atingidas graÃas à instalaÃÃo de uma bomba de deslocamento positivo que promoveu a circulaÃÃo do Ãleo. Termopares instalados nos estÃgios da torre registraram o aumento de temperatura ao longo do dia. Picos de 77ÂC foram medidos no tanque de armazenamento da torre. Valores mÃdios de produÃÃo por dia sÃo de 25 litros de Ãgua, com uma condutividade mÃdia sempre inferior a 10 μS/cmÂ, o que representa uma eficiÃncia na remoÃÃo de sais superior a 99%. No cÃlculo de desempenho, o melhor resultado foi obtido quando o sistema de bombeamento foi combinado com o uso de um refletor solar, obtendo o valor do GOR (RazÃo de ganho de saÃda) de 2,85.

The ability to predict the future behavior of solar activity has become of extreme importance due to its effect on the near-Earth environment. Predictions of both the amplitude and timing of the next solar cycle will assist in estimating the various consequences of Space Weather. Several prediction techniques have been applied and have achieved varying degrees of success in the domain of solar activity prediction. These techniques include, for example, neural networks and geomagnetic precursor methods. In this thesis, various neural network based models were developed and the model considered to be optimum was used to estimate the shape and timing of solar cycle 24. Given the recent success of the geomagnetic precusrsor methods, geomagnetic activity as measured by the aa index is considered among the main inputs to the neural network model. The neural network model developed is also provided with the time input parameters defining the year and the month of a particular solar cycle, in order to characterise the temporal behaviour of sunspot number as observed during the last 10 solar cycles. The structure of input-output patterns to the neural network is constructed in such a way that the network learns the relationship between the aa index values of a particular cycle, and the sunspot number values of the following cycle. Assuming January 2008 as the minimum preceding solar cycle 24, the shape and amplitude of solar cycle 24 is estimated in terms of monthly mean and smoothed monthly sunspot number. This new prediction model estimates an average solar cycle 24, with the maximum occurring around June 2012 [± 11 months], with a smoothed monthly maximum sunspot number of 121 ± 9.

[pt] O presente trabalho descreve o desenvolvimento de um gerador termoelétrico cujos termoelementos são obtidos a partir de um composto de dissiliceto de ferro (FeSi2). A originalidade do trabalho reside na simplificação do processo de obtenção do termoelemento e na utilização de matérias-primas com grau de pureza industrial, em contraposição aos processos usuais que utilizam materiais de custo elevado, com alto grau da pureza e sofisticados processos de fabricação. O composto é obtido pelo processo de fusão num forno de indução à vácuo. A forma geométrica do termoelemento é assegurada pelo processo de sinterização. Um processo de recozimento garante a formação da fase Beta, assegurando a existência das propriedades termoelétricas. O coeficiente de Seebeck mostrou-se dependente do tempo de recozimento. Para os materiais desenvolvidos, o termoelemento tipo P apresentou um coeficiente de Seebeck de 250 MV/K e o material tipo N, um coeficiente de 75 MV/K, valores estes que qualificam o material para construção de geradores termoelétricos. Estima-se que o custo de fabricação do material desenvolvido reduziu de oito para dois dólares o custo de fabricação de materiais termoelétricos por watt de eletricidade gerado. Experiências preliminares utilizando a técnica de serigrafia para fabricação de termoelementos parecem confirmar a possibilidade de uma redução ainda maior do custo de fabricação. / [en] This work describes the development of a thermoelectric generator whose thermoelements are made of a new thermoelectric material, FeSi2, an iron disilicide alloy. The originality of this work relies on the simplicity of the process by which the termoelements are obtained and also on the possibility to use a raw material with industrial purity grade, as opposed to conventional techniques which use costly materials, with a high degree of purity, and sofisticated process of fabrication. The alloy is obtained by a process of fusion in a vacuum induction type furnace. The geometric shape of the thermoelement is obtained by a process of sinterization. An annealing process garantees the formation of the Beta phase, thus assuring the existence of thermoelectric propertyes. The Seebeck coefficient proved to be dependent on the time duration of the annealing. As for the material developed, the P Type material presented an average Seebeck coefficient of 250 MV/K and the N type material, a coefficient of 75 MV/K, these figures qualify the materials for construction of thermoelectric generators. It is estimated that the manufacturing cost of the material developed reduced the cost of thermoelectric materials per watt of electricity generated from eight to two dollars. Preliminary experiments using the silk-scream technique in manufacturing of thermoelements seems to promise an even greater reducting in the manufacturing costs.

With the objectives of designing a solar cooling system with cold storage unit for the Iraqi climate, solar energy resources were assessed and methods were proposed to enhance harvesting the solar energy in the Iraqi climate. Where the results showed that adopting monthly average optimal tilt angles led to an increase in the amount of useful solar energy gained nearly 9%. A methodology of multi objective optimisation of solar absorption cooling system was then developed and demonstrated by applying it in a domestic application in Baghdad. Maximising the system performance in exergy, economic and environment were the objectives of the project. A decision-making tool was then implemented to select the most suitable design. The optimal proposed system has exergy efficiency of 56%, total cost rate of 4.19US$/hr, annual CO2 emission of 32199kg and payback period of 18.7years. After analysing the optimal configuration of the system, a cold thermal energy storage unit with the solar absorption cooling system was suggested in order to store the cold energy produced by the system at times when the solar energy is available (at daytime) and use (discharge) it at times when there is no solar energy available (at night). Next, a new control strategy was developed and applied in the system to make it more cost effective. Five scenarios were considered to manage the quantity of charging of the cold storage tank according to the splitting rate of the mass of the supplied chilled water by the chiller to the cold storage tank and the building. Finally, the chosen optimal system that uses an efficient controlled cold thermal energy storage, has exergy efficiency of 69.4%, total cost rate of 4.25US$/hr and total avoided annual CO2 emissions of 33.9% less than system without cold storage tank. Additionally, without any government incentive, the payback was recorded 9.3years, which was 50% less than the system without cold storage tank.

The continuous escalation of intermittent energy added to the grid and forecasts of peaking power demand increments are rising the effort spent for evaluating the economic feasibility of energy storages. The aim of this research is the techno-economic analysis of Compressed Air Energy Storage (CAES) systems, capable of storing large quantities of off-peak electric energy in the form of high-pressure air, as an ―energy stock‖ which allows the production of high-profit on-peak electricity when required by the grid. Several studies of both conventional and innovative adiabatic concepts are carried out in order to identify and improve the parameters that mostly affect the plant performances. Technical models, that consider the effect of time, are developed to evaluate the parameters that reduce the electric energy spent for compressing the air and that maximize the electric energy produced. In the conventional plant, particular attention is put on the understanding of the effects of air storage pressure range, recuperator, reheating and Turbine Inlet Temperature. For the adiabatic instead, a thorough analysis of the challenging Thermal Energy Storage (TES) is performed for understanding the advantages and drawbacks of this novel efficient concept of CAES. In a further step the economic analyses are aimed at evaluating the different configurations proposed in the technical investigation and the effects that variations of generation train and storage characteristics have on the profitability. After an analysis of the TES impact on the profits, a final comparison is carried out against two existing technologies: Pumped Hydro Energy Storage and gas turbine. The results of these studies confirm, from a technical and economic point of view, the reasons of the growing interest toward CAES as a feasible solution to manage the intermittent energy production. In particular they underline the conventional CAES as promising technology to undertake.

M.Ing. / A dissertation presented on the basic solar design principles such as sun-earth geometry, energy wavelengths, optics, incidence angles, parabolic collector configurations and design, materials for solar applications, efficiencies, etc to be considered in Solar Concentrating Collector design. These principles were applied in the design and fabrication of a prototype solar collector. The solar collector was tested to verify and correct mathematical models that were generated from existing literature; as well as for optimization work.

Master of Science / Department of Mechanical and Nuclear Engineering / Hitesh Bindra / Storing excess thermal energy in a storage media that can later be extracted during peak-load times is one of the better economical options for nuclear power in future. Thermal energy storage integration with light water-cooled and advanced nuclear power plants is analyzed to assess technical feasibility of different storage media options. Various choices are considered in this study; molten salts, synthetic heat transfer fluids, and packed beds of solid rocks or ceramics. In-depth quantitative assessment of these integration possibilities are then analyzed using exergy analysis and energy density models. The exergy efficiency of thermal energy storage systems is quantified based on second law thermodynamics. The packed bed of solid rocks is identified as one of the only options which can be integrated with upcoming small modular reactors. Directly storing thermal energy from saturated steam into packed bed of rocks is a very complex physical process due to phase transformation, two phase flow in irregular geometries and percolating irregular condensate flow. In order to examine the integrated physical aspects of this process, the energy transport during direct steam injection and condensation in the dry cold randomly packed bed of spherical alumina particles was experimentally and theoretically studied. This experimental setup ensures controlled condensation process without introducing significant changes in the thermal state or material characteristics of heat sink. Steam fronts at different flow rates were introduced in a cylindrical packed bed and thermal response of the media was observed. The governing heat transfer modes in the media are completely dependent upon the rate of steam injection into the system. A distinct differentiation between the effects of heat conduction and advection in the bed were observed with slower steam injection rates. A phenomenological semi-analytical model is developed for predicting quantitative thermal behavior of the packed bed and understanding physics. The semi-analytical model results are compared with the experimental data for the validation purposes. The steam condensation process in packed beds is very stable under all circumstances and there is no effect of flow fluctuations on thermal stratification in packed beds. With these experimental and analytical studies, it can be concluded that packed beds have potential for thermal storage applications with steam as heat transfer fluid. The stable stratification and condensation process in packed beds led to design of a novel passive safety heat removal system for advanced boiling water reactors.

Concentrating solar power (CSP) plant is a promising technology that exploits direct normal irradiation (DNI) from the sun to be converted into thermal energy in the solar field. One of the advantages of CSP technology is the possibility to store thermal energy in thermal energy storage (TES) for later production of electricity. The integration of thermal storage allows the CSP plant to be a dispatchable system which is defined as having a capability to schedule its operation using an innovative dispatch planning tool. Considering weather forecast and electricity price profile in the market, dispatch planning tool uses an optimization algorithm. It aims to shift the schedule of electricity delivery to the hours with high electricity price. These hours are usually reflected by the high demand periods. The implementation of dispatch optimizer can benefit the CSP plants economically from the received financial revenues. This study proposes an optimization of dispatch planning strategies for the parabolic trough CSP plant under two dispatch approaches: solar driven and storage driven. The performed simulation improves the generation of electricity which reflects to the increase of financial revenue from the electricity sale in both solar and storage driven approaches. Moreover, the optimization also proves to reduce the amount of dumped thermal energy from the solar field.

No description available.

Content: The aim of this desk study is to compare consumption of thermal energy in temperate vs. (sub)tropical climate for two representative processes: float heating (bating and dyeing) and chamber drying, with the view of contributing towards overall assessment of thermal energy consumption for tanneries operating under rather different conditions. The energy consumption is calculated for 1 t of wet salted hides and assuming that 1000 kg of wet salted weight corresponds to 1100 kg of pelt weight containing 838 kg of water and 262 kg of collagen subsequently segregated into grain leather and usable splits. Float rates (200% on pelt/shaved weight), average inlet water temperatures (15 oC vs. 25 oC), process float temperatures for bating (35 oC) and dyeing (60 o C) have been defined. Similarly, for computation of thermal energy for chamber drying, identical initial (45 %) and target leather humidity (20 %) are set and average respective fresh air temperature (15 oC vs. 30 oC) and fresh air relative humidity (50% vs. 70%) estimated and operating conditions such as exhaust air temperature and relative humidity defined. Based on such parameters and assumptions, specific ratios for thermal energy consumption for float heating (bating & dyeing) and for chamber drying have been calculated and comparisons made; the results might not quite coincide with common perceptions. The energy needs computed are net amounts, i.e. regardless of the source and without taking into account any losses and disregarding energy consumption for ambient heating and/or cooling. Thus, the total energy needs are much higher. The ratios computed for grain leather are valid for split leather as well. However, if the solar energy is used to support water heating, the conditions in the tropic zone are substantially more favourable, due to higher insolation and higher efficiency factor (i.e. difference of the final vs. inlet water temperature). Take-Away: Based on such parameters and assumptions, specific ratios for thermal energy consumption for float heating (bating & dyeing) and for chamber drying have been calculated and comparisons made; the results might not quite coincide with common perceptions. However, if the solar energy is used to support water heating, the conditions in the tropic zone are substantially more favourable, due to higher insolation and higher efficiency factor (i.e. difference of the final vs. inlet water temperature).