Original Article
nadereh tabrizi; mojtaba moravej
Abstract
This study comprehensively evaluates the technical and economic performance of grid-connected pvsyst in Urmia and Kashan, comparing them with an off-grid system in pvsyst. The results indicate that the grid-connected system in Kashan, benefiting from higher solar irradiation, achieves superior performance ...
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This study comprehensively evaluates the technical and economic performance of grid-connected pvsyst in Urmia and Kashan, comparing them with an off-grid system in pvsyst. The results indicate that the grid-connected system in Kashan, benefiting from higher solar irradiation, achieves superior performance compared to Urmia. High energy consumption by auxiliary equipment, particularly a constant 5 kW nighttime load, was a major challenge for both systems, with a more pronounced impact in Urmia due to lower energy production. Thermal losses and long-term module efficiency degradation also affected performance. Economically, grid-connected systems demonstrate high investment attractiveness, with a payback period of 3 years, an internal rate of return of 71.99%, and a levelized cost of energy (LCOE) of approximately 2,700 IRR/kWh, assuming accurate input data. These systems also offer significant environmental benefits by reducing greenhouse gas emissions. Conversely, the off-grid system faced a 31% energy shortage, compromising its reliability for critical applications, with energy wastage during battery saturation periods indicating suboptimal capacity design. The off-grid system’s LCOE is substantially higher due to high initial battery costs, periodic replacement expenses, and lower efficiency. The analysis confirms that grid-connected systems, when supported by reliable grid infrastructure, provide superior technical and economic performance compared to off-grid systems, which are primarily viable in remote areas without grid access. However, the sustainability and economic viability of grid-connected systems heavily depend on supportive policies and stable regulatory frameworks.
Original Article
Adel Taheri Hajivand; Reza Mehdipour
Abstract
Greenhouse cultivation, with its advantages such as high resource efficiency, year‑round production, reduced dependence on climatic conditions, and significant water savings, plays a crucial role in achieving sustainable agriculture and creating economic value added. Despite these merits, the greenhouse ...
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Greenhouse cultivation, with its advantages such as high resource efficiency, year‑round production, reduced dependence on climatic conditions, and significant water savings, plays a crucial role in achieving sustainable agriculture and creating economic value added. Despite these merits, the greenhouse sector in East Azerbaijan Province faces multiple structural and operational challenges. This study applied a descriptive–survey design using a validated and reliable questionnaire, alongside a hybrid analytical framework combining quantitative (SWOT and QSPM) and qualitative (field observation and expert interviews) methods. The integrated results revealed strong convergence between both approaches, classifying the challenges into seven key dimensions: economic, managerial, marketing and sales, structural, educational, seed and natural resources, and social issues. The SWOT analysis indicated that the mean scores of internal and external factors were 2.11 and 2.21, respectively, suggesting a relatively stable but weak system requiring reinforcement of supportive and managerial structures. Based on the QSPM outcomes, the most attractive development strategy was identified as “enhancing financial and technological infrastructure through public–private partnership (PPP)”, with a total attractiveness score of 6.42. The findings emphasize that overcoming current barriers requires implementing hands‑on training, targeted investment in infrastructure, promotion of advanced technologies, standardization of production and management systems, and provision of financial and credit support schemes. These strategic actions would improve the sustainability of greenhouse cultivation, enhance production quality and quantity, and strengthen the competitive position of the region’s agricultural economy.
Original Article
Mohammad-Ali Behaeen
Abstract
Increasing and improving feed conversion ratio in the livestock industry is achieved by using total mixed rations. Providing adequate and balanced nutrients in the ration to increase production is achieved by mixing feed ingredients. The important point in preparing this type of animal feed, is the homogeneity ...
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Increasing and improving feed conversion ratio in the livestock industry is achieved by using total mixed rations. Providing adequate and balanced nutrients in the ration to increase production is achieved by mixing feed ingredients. The important point in preparing this type of animal feed, is the homogeneity of mixing of the ingredients and the same distribution in each animal. Feeder mixer machines are suitable implement for preparing a total mixed ration in animal husbandry. In order to investigate the homogeneity of the total mixed ration in a feeder mixer machine, the effect of three levels of spiral rotation of 50(R50), 60(R60) and 70(R70) rpm, and the mixing time at three levels of 15(T15), 18(T18) and 21(T21) minutes were compared in a factorial experiment in a completely randomized design with three replications. A mixture of straw, alfalfa, corn silage, sugar beet pulp pellets, livestock concentrate, and water was used to prepare the ration in a feeder mixer machine. The parameters studied included measuring the crushing of mixed ration, measuring and calculating the homogeneity of mixed materials, and examining the flowability of mixed materials (Froude number). The data obtained were analyzed with SAS software and means were compared with Duncan's multiple range test. The results showed that the highest amount of material crushing (the lowest in the geometric mean of material) was obtained at a spiral rotation of 70 rpm and a time of 21 minutes (treatment R70T21) and the lowest amount of forage material crushing was obtained at a spiral rotation of 50 rpm and a time of 15 minutes (treatment R50T15) with a significant difference between them (P<0.05). The highest homogeneity was also achieved in the R70T21 treatment. Considering the widespread use of feeder mixer machine in dairy farms and the time savings in preparing total mixed ration, a treatment should be provided that has a small spiral axis and the time spent using the machine in preparing the total mixed ration is appropriate. Based on the studies conducted, the R50T18 treatment with a standard deviation of 1.39 cm in piece length (Sgm) and a homogeneity of mixed materials of 1.63 g (Sd), is recommended.
Original Article
Koumars Daemi Milani; Babak BEHESHTI; Mohammad Ghahderijani
Abstract
In this study, the non-edible oilseed of the Bassia scoparia plant was introduced as a raw material for biodiesel production and the effect of the resulting biodiesel on the emission of pollutants from a diesel engine was investigated. After purification of Bassia scoparia seeds, oil extraction was performed. ...
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In this study, the non-edible oilseed of the Bassia scoparia plant was introduced as a raw material for biodiesel production and the effect of the resulting biodiesel on the emission of pollutants from a diesel engine was investigated. After purification of Bassia scoparia seeds, oil extraction was performed. In order to investigate the emission of pollutants, an air-cooled single-cylinder engine was used. Emission tests were conducted to determine the effects of engine speed, load, and fuel composition on carbon monoxide, carbon dioxide, unburned hydrocarbons, and NOX using an exhaust gas measurement system. The experiments were conducted at three engine speed levels (1800, 2100 and 2400 rpm), five load levels (0, 25, 50, 75 and 100 percent) and five different biodiesel ratios (B0, B5, B10, B15 and B20). 25 percent load was chosen as a stable and conventional operating condition in the low-load region to allow for the evaluation of the independent effect of engine speed on pollutants. In order to investigate the effect of independent variables on dependent variables, analysis of variance with a completely randomized experimental design was used. The findings of this study showed that engine operation at a constant load of 25 percent and a rotational speed of 2100 rpm, when using a blend containing 15 percent biodiesel, significantly improved the emission indices. Under the same conditions, the highest reduction in carbon monoxide was 17.65% compared to pure diesel. Also, the highest reduction in unburned hydrocarbons was 63.35% and the highest drop in nitrogen oxides was 35% for the same mixing ratio.
