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[en] Distillation of water is energy intensive, and the use of solar energy for this purpose has been quite well developed and applied in many places. The performance of a simple basin greenhouse-type solar still coupled to a flat plate collector is experimentally investigated. The Saharan sites of Algeria enjoys bright sunshine and dry weather during most part of year. The objective of the work is to improve the performances of a simple single basin solar still, we test the distillation system in winter, under desert climatic conditions, to improve the quality and increase the quantity of distilled water, by using a solar collector for increasing the brine temperature, enhancing the evaporation process of a simple solar still and improving distillate collection process. Experiments have been conducted in Adrar, Algerian desert town (27 degree 18' N, latitude, 0 degree 17' W longitude). The daily still productivity in winter period varies from 4.5 l/m2/day to 5.3 l/m2/day with variation of water level from 1.5 cm to 3.5 cm. (Author)
[en] The main objective of the present work is the study of a plan solar still with greenhouse effect. We have especially worked on the determination of operating characteristics, production, internal and global efficiencies. The proposed work is purely experimental and is part within the framework of improving the profitability of a solar still with greenhouse effect. During this period of experimentation, different parameters have been mainly a series of measurements: solar flux, the temperatures of different parts of the plant (internal pane of glass, internal air, water in the tank,...) and the daily production. The obtained results have allowed us to see the temperature influence of the water in the tank on the daily production and the use of jute (porous matter) to facilitate the evaporation and increasing the amount of distillated water and to conclude on the effectiveness of the undertaken initiative.
[fr]L'objectif essentiel de ce present travail est l'etude d'un distillateur plan a effet de serre. Nous avons particulierement travaille a la determination des caracteristiques de fonctionnement, de production, des efficacites globale et interne. Le travail propose est purement experimental et entre dans le cadre de l'amelioration de la rentabilite d'un distillateur solaire a effet de serre. Au cours de cette periode d'experimentation, differents parametres ont fait l'objet d'une campagne de mesures, principalement : flux solaire, temperatures des differents parties de l'installation (face interne de la vitre, l'air interne, eau du bac,..) et la production journaliere. Les resultas obtenus nous ont permis de voir l'influence de la temperature de l'eau du bac sur la production journaliere ainsi que l'utilisation du jute (materiau poreux) facilitant l'evaporation et augmentant la quantite de distillat et de conclure sur l'efficacite de l'initiative entreprise.
[en] The performance of a single slope solar still using different operational parameters was studied experimentally. The increase in still productivity ranged from 22% to 51% when enhancers such as asphalt liner and sprinkler have been applied to the still. Also the ambient conditions were found to have direct effect on the productivity of the still. Increases are higher at night than in the day. due to the differences in temperature between the cover and water. The study also showed that the daily production of still can be increased by reducing the depth of the water in the basin. Distilled water can be used for drinking (some treatment required), and for industrial proposes (water jackets, batteries, chemical solutions).(Author)
[en] A methodology that gives the thermodynamic limits to the gross and the net environmental thermal impacts of the solar synthesis of a fuel is proposed. This methodology is based on the concept of gross environmental thermal equivalent of a fuel, which is defined as the minimum amount of heat interchanged with the environment needed to reversibly synthesize one mole of the pure fuel, at environmental temperature and pressure, from reactants and with the other products contained in the environment, when this one and the Sun are the only energy sources. The net environmental thermal equivalent of a fuel takes into account that the solar energy used to synthesize the fuel does not heat the environment. Thermodynamic algorithms depends only on Sun radiation equivalent temperature, thermal equations of state of environment and pure fuel, and standard equilibrium constant of formation for each compound taking part in the chemical reaction. Numerical and graphical results are given for the synthesis of graphite, carbon monoxide, methane, ethane, propane, methanol, ethanol, and dihydrogen, all of them synthesized from atmospheric carbon dioxide and water vapour. These algorithms do not depend on any particular technology, and can be considered as an objective reference for selecting reactions, sites, and operational strategies for synthesizing solar fuels. Results and conclusions of this paper can also provide a basis for ecological fiscal taxes of the use of fossil fuels. The results of applying this methodology give an objective criterium to valorize economically thermal and chemical replenishment cost of the environment, related with cost of solar technologies. (author)
[en] Highlights: • The effect of basin depth (height of the walls of a basin) was investigated. • Basin depth can affect the amount of distillate yield up to 26%. • The effect of water depth in constant water surface-cover distance (WCD) was studied. • Water production was 15% more dependent to water depth than previous researches. • Four single basin solar stills were tested simultaneously in various seasons. - Abstract: The effects of water depth in solar stills were studied in many earlier works. It was revealed that in the previous experimental works, the water surface-cover distance (WCD) was altered with the change of the water depth. However, in this research, the effects of water depth and WCD were investigated separately, and effects of water depth on the performance of solar stills with the same WCD were examined for the first time. In this way at first, some experiments were conducted in the summer and winter seasons using the stills with the same water depths, but different basin depths (i.e. different WCDs). It was found that WCD can affect the amount of distillate yield up to 26%. Thus, it was concluded that to study the effect of water depth accurately, different stills should be employed at the same time (to keep WCD constant). In the second step, some experiments were conducted using four stills in the summer, fall and winter seasons to examine the effects of water depth, while the WCD was constant. In addition, the stills with different water depths were modeled analytically and their performance was investigated. Moreover, an empirical relationship was obtained between the distillate yield and the water depth. By comparing the results of this empirical relation with previous studies, it was revealed that the past researches reported a lower dependency (in the average 15%) of the distillate yield on the water depth, since in their experimental works, WCD was changed along with the water depth.
[en] The effect of wind speed V on the daily productivity Pd of some active and passive solar stills is studied by computer simulation. Numerical calculations have been carried out on typical summer and winter days in Tanta in order to correlate Pd with V for different masses of basin water mw for the passive stills and various thicknesses dw or mass flow rates mw of the flowing brine for the active stills. It is found that for the active and multi-effect passive stills, Pd increases with the increase of V up to a typical velocity Vt beyond which the increase in Pd becomes insignificant. However, for all the investigated single effect passive stills, there is a critical mass (depth) of basin water beyond which Pd increases as V increases until Vt. For basin water masses less than the critical mass, Pd is found to decrease with increasing V until Vt. After Vt, the change in Pd is unimportant in a similar behavior to that obtained for the active and multi-effect passive stills. The critical mass (depth) of basin water for the investigated single effect passive stills is found to be 45 kg (4.5 cm). Moreover, the typical velocity Vt is independent on the still shape and the mode of operation (active or passive) but it shows some seasonal dependence. For the investigated stills, Vt is found to be 10 and 8 m/s on typical summer and winter days, respectively. Comparisons with the results reported in the previous studies about the effect of wind speed on productivity have been carried out
[en] This report quantifies greenhouse gas (GHG) emissions from the industrial sector and identifies opportunities for non-GHG-emitting thermal energy sources to replace the most significant GHG-emitting U.S. industries based on targeted, process-level analysis of industrial heat requirements. The intent is to provide a basis for projecting opportunities for clean energy use. This provides a prospectus for small modular nuclear reactors (including nuclear-renewable hybrid energy systems), solar industrial process heat, and geothermal energy. This report provides a complement to analysis of process-efficiency improvement by considering how clean energy delivery and use by industry could reduce GHG emissions.
[en] A double slope floating cum tilted-wick solar still has been fabricated and transient theory of floating cum tilted-wick type solar still has been proposed. Analytical expressions have been derived for the different temperatures components of the proposed system. For elocution of the analytical results, numerical calculations have been carried out using the meteorological parameters for a typical summer day in Coimbatore. Analytical expression results are found to be in the close agreement with the experimental results. (authors)