سال:1394 | دوره: | شماره: |تعداد مقالات:10

Renewable energy is an inevitable choice to meet the demands of energy resource. In the 21st century, one of the serious problems facings us is the energy resources that restrict the social progress and sustainable development. Environmental pollution and fossil energy resources shortage force people to explore and use new energy resources. The aim of this paper is to study the effect of blade installation angle on power coefficient of a five-blade resistance type vertical axis wind turbine using CFD simulations. The computation is conducted for the turbine with the blade diameter of 0.76–0.86 m and the turbine radius R=2 m. The results show that the maximum value of power efficiency of 28.48% can be obtained when the installation angle is 19o for the five-blade resistance type vertical axis wind turbine with the blade diameter of 0.78 m and the turbine radius R=2 m.

Routing of high-voltage electric transmission lines for the connection of renewable energy-distributed generation plants is a critical issue from an environmental point of view. A standard methodology that accounts for multiple perspectives, influence factors and is able to mediate between weighted constraints can be a useful tool for the regulating bodies that are involved in approval processes. The methodology can be an effective support to increase reliability, save consumers’ money and mitigate the unavoidable impacts of the lines on the population living nearby. In this paper we investigate the suitability of a procedure employed by Terna, the Italian high-voltage transmission system operator, to identify the corridors where to route new overhead transmission lines with the lowest environmental impact. The methodology is based on the subdivision of all the relevant constraints dictated by environmental issues and territory legislations in four main classes. A real case study concerning the design and connection of a wind farm placed near Collarmele, in the center of Italy, shows the effectiveness of the proposed methodology.

It is known that both acids and salts have a positive catalytic effect on the dehydration of pentoses to form furfural, a potentially attractive platform chemical. In this study the effects of the combined usage of an organic acid, instead of stronger mineral acids, and a saline catalyst is investigated. In order to assess these effects, the kinetics of pentose dehydration to furfural are studied using oxalic acid as the primary catalyst and NaCl or seawater as the secondary saline catalyst. The interactions between these two types of catalysts are complex and are, therefore, also assessed thermodynamically. The addition of salts lowers the activity coefficient of the hydronium ions, but simultaneously favours the dissociation of the organic acid. It turned out that these two effects are of similar magnitude, resulting in a fairly constant hydronium ion activity. Because nonetheless higher furfural yields are obtained using the salts as a secondary catalyst, it is concluded that the salts influence the pentose dehydration mechanism directly. The final furfural yields obtained using oxalic acid as the primary catalyst were only slightly lower than those for similar experiments using HCl. The most distinctive difference between the two acids is the lower reaction rate (and thus longer reaction times) when using oxalic acid. Finally, it was observed that if no acidic catalyst is used, the salts tend to catalyse a loss reaction, which is suppressed when an acid is present.

The objective of this study was to develop a simple and cost-effective method to produce biofertilizer using agro-wastes. There were five types of agro-wastes being used in this study. They were wastes from watermelon, papaya, pineapple, citrus orange, and banana. Solidstate fermentation method was used to produce biofertilizer, which was then applied into vegetable plantation.Physical property tests were done on the plant samples of 5 weeks of age in order to determine the effectiveness of the biofertilizer. The results of the experiment showed that the plant samples treated with biofertilizer from watermelon, papaya, and banana wastes had promising physical characteristics. Other tests such as analyses of pH values and potassium content in the biofertilizers were also done in this research. It was found that watermelon biofertilizer had the highest pH value (5.15). The banana biofertilizer had the highest content of potassium with a content of 3.932 g K/L.

In the chemical and pharmaceutical industry, molecular organic chemistry is undergoing a green revolution in order to avoid waste by developing a cleaner and safer chemistry. This change is subject to the new European regulation REACH. One of the major goals of organic synthesis is to design molecules with high added value by developing synthetic methods highly selective, economical and environmentally friendly. To satisfy the societal expectation new activation methods must be developed in order to shorten the synthesis, to respect the principle of atom economy and to substitute pollutants or toxic organic solvents. In this context, our group focuses its research on the synthesis of biologically active molecules, developing new environmentally friendly synthetic strategies and more energy-efficient alternatives such as microwaves, ultrasound, photochemistry or biotransformation. We present here how various activation methods used for the preparation of several high-value compounds can dramatically enhance yields and selectivity. First, we describe microwave-assisted syntheses of precursors of [11C] PIB, a tracer used in PET imaging and amides intermediates of natural products. We describe also the selective reduction of nitro compounds using ultrasound activation and a facile pathway to obtain b3-chiral amino-acids by biotransformation using purified nitrilases. Finally the results concerning the alkylation of a-aldehydes, using visible light and dyes as catalysts without transition metal are discussed. Some general considerations concerning the activation methods and their impact on the environment and the energy saving are given.

The sustainable use of renewables will represent a key challenge in the near future, and relative energy management operations will play a crucial role in energy efficiency and savings for future generations. The operation and maintenance of energy systems are a very high valuable activity to prevent energy losses, and a correct monitoring can detect in advance equipment degradation guaranteeing good performance over time. Present research strives to find out possibility of unmanned aerial vehicle (UAV) use in monitoring applications for energy production sites and to investigate effects of this novel method on energy management procedures. Furthermore, investigation about novel approaches in cooperative inspection of real photovoltaic (PV) plants was carried out by light UAVs and utilize the global positioning system to find out the optimum route mapping during the solar PV modules monitoring. The purpose of this work is to propose a reliable, fast and cost effective method for PV plant planning and monitoring by means of UAS technology.

Ground-source heat pumps are a reliable technology and may represent an efficient and cost-effective option for space heating and cooling, when the investment for ground heat exchangers is reasonable. New advanced ground exchangers have been recently proposed, showing high performances also in shallow ground; their shape has not yet been investigated in literature. In the present study, an analytical solution based on the line source method is applied for sizing a novel shape. This so-called flat-panel shape is assumed to be an equivalent slinky-coil having the same heat transfer surface per unit of trench length. As overall benchmarks, two other configurations of straight pipes disposed vertically and horizontally have been sized; all devices are supposed to work in a four lined geothermal field. The building heating requirement has been evaluated assuming a simplified lumped system and three different climate zones, defined by 2.000, 2.500 and 3.000 degree days. Then, a 2D finite-element model has been implemented to solve the transient heat conduction problem in the ground. The results of the analytical formulation and numerical simulations have been compared in terms of average temperature at the wall surface of the heat exchanger. The design minimum temperature considered by the analytical method in sizing the two straight pipe configurations and the flat-panel is accurately reproduced by the numerical model. Therefore, the slinky-coil equivalent approach followed in the analytical method for sizing the flat-panel seems to be a reliable and suitable approximation.

The use of concentrating solar collectors which are used in solar thermal power plant and concentrated photovoltaic systems implies that these systems only work with the direct normal irradiance (DNI). Unfortunately, DNI ground-based measurements are rarely available at the location of interest, this lack of DNI data contrasts with the availability of global and diffuse horizontal irradiance data (GHI, DHI). Nowadays, several spatial databases that estimate DNI have been developed; however, these databases present uncertainty and provide different values of DNI. In this present study, a proposed methodology for estimating the hourly, monthly mean daily, monthly and annual direct normal irradiance DNI in the presence or absence of measured global and diffuse horizontal irradiances. When applying the proposed method for calculation of DNI for three Algerian ground stations (Algiers, Ghardaia, and Tamanrasset), we obtained better performances than those of the five spatial databases’ data, especially for the monthly values. The methodology seems to give a very appropriate way for management and exploitation of DNI resources for the design and analysis of concentrating photovoltaic and thermal systems; and can be applicable to other worldwide locations using empirical equations with new correlation coefficients for estimating direct normal irradiance.

In order to accomplish the objective of studying and optimizing the flow channel geometries and dimensions for high-temperature proton-exchange-membrane (PEM) fuel cells (with operating temperatures above 120oC), a mathematical model has been developed in this work. As the major step of the modeling, the average concentrations of gas species in bulk flows as well as in the layers of electrodes are calculated through mass transfer analysis in one-dimensional direction normal to the membrane-electrodes layers. Therefore, the concentration and activation polarizations are simulated with much less computational work compared to a three-dimensional numerical model. The ohmic loss is taken into consideration through analysis of a representative network circuit simulating the electron and proton conduction in the elements of electrodes and electrolyte, respectively. The simulated results for high-temperature PEM fuel cells were compared with experimental results from literature. The results from the simulation and experimental tests showed good agreement, which validated the mathematical model.As the model requires less computational work, it was used to analyze a large number of cases with different gas flow channel dimensions and operating conditions, and optimization to the dimensions of channels and ribs was accomplished.

Urban areas usually experience higher temperatures when compared to their rural surroundings. Several studies underlined that specific urban conditions are strictly connected with the Urban heat island (UHI) phenomenon, which consists in the environmental overheating related to anthropic activities. As a matter of fact, urban areas, characterized by massive constructions that reduce local vegetation coverage, are subject to the absorption of a great amount of solar radiation (short wave) which is only partially released into the atmosphere by radiation in the thermal infrared (long wave). On the contrary, green areas and rural environments in general show a reduced UHI effect, that is lower air temperatures, due to evapo-transpiration fluxes. Several studies demonstrate that urban microclimate affects buildings’ energy consumption and calculations based on typical meteorological year could misestimate their actual energy consumption. In this study, two different sets of meteorological data are used for the calculation of the heating and cooling energy needs of an existing university building. The building is modeled using TRNSYS v.17 software. The first set of data was collected by a weather station located in the city center of Modena, while the second set of data was collected by another station, located in the surrounding area of the city, near to the studied building. The influence of the different meteorological situations described by the two weather stations areanalyzed and assumed to be representative of the UHI effect. Furthermore, the effects of UHI mitigation strategies on the building energy needs are evaluated and discussed.