Research Article
Hamid Ghaderi; Mona Asadi; Saeed Shavalpour
Abstract
Switchgrass is known as one of the best second-generation lignocellulosic biomasses for bioethanol production. Designing efficient switchgrass-based bioethanol supply chain (SBSC) is an essential requirement for commercializing the bioethanol production from switchgrass. This paper presents a mixed integer ...
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Switchgrass is known as one of the best second-generation lignocellulosic biomasses for bioethanol production. Designing efficient switchgrass-based bioethanol supply chain (SBSC) is an essential requirement for commercializing the bioethanol production from switchgrass. This paper presents a mixed integer linear programming (MILP) model to design SBSC in which bioethanol demand is under auto-regressive moving average (ARMA) time series models. In this paper, how a SBSC design is affected by ARMA time series structure of bioethanol demand is studied. A case study based on North Dakota state in the United States demonstrates application of the proposed approach in designing the optimal SBSC. Moreover, SBSC optimal design is forecasted for the time horizon of 2013 to 2020 with the bioethanol demand acquired from the ARMA models to provide insights for designing and minimizing total cost of SBSC in the future efficiently. Finally, in order to validate the proposed approach, a reproduction behavior test is done. Also, a comparative analysis based on a SBSCND model from the recent literature is elaborated to show the performance of the proposed approach.
Research Article
Ghazanfar Shahgholian
Abstract
The hydro turbine dynamics have a considerable influence on the dynamic stability of power system. In the study of dynamic stability, the system is modeled by the linear differential equations (small signal analysis). Small signal stability of power systems is needed in all conditions and ...
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The hydro turbine dynamics have a considerable influence on the dynamic stability of power system. In the study of dynamic stability, the system is modeled by the linear differential equations (small signal analysis). Small signal stability of power systems is needed in all conditions and only is dependent on the conditions of power system performance before commotion occurrence. This paper provides an analysis of the small signal stability in a hydropower plant equipped with low head Kaplan turbine connected as single-machine infinite-bus (SMIB) power system. The dynamical behaviors withrepresentative characteristics are identified and studied in details. The model of system is described by state-space equations. The eigenvalues analysis is used to show the effects of change in parameters for damping load angle and speed oscillations through the excitation and governor subsystems. Finally, results of theoretical analyses are verified by time-domain simulations under different system conditions and operating loads.
Research Article
Hassan Ghasemi Mobtaker; Yahya Ajabshirchi; Seyed Faramarz Ranjbar; Mansour Matloobi; Morteza Taki
Abstract
Precise knowledge ofthe amount of global solar radiation plays an important role in designing solar energy systems. In this study, by using 22-year meteorologicaldata, 19 empirical models were tested for prediction of the monthly mean daily global solar radiation in Tabriz. In addition, various ...
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Precise knowledge ofthe amount of global solar radiation plays an important role in designing solar energy systems. In this study, by using 22-year meteorologicaldata, 19 empirical models were tested for prediction of the monthly mean daily global solar radiation in Tabriz. In addition, various Artificial Neural Network (ANN) models were designed for comparison with empirical models. For this purpose, the meteorological data recorded by Iran Meteorological Organization (1992–2013) was used. These data include: monthly mean daily sunshine duration, monthly mean ambient temperature, monthly mean maximum and minimum ambient temperature and monthly mean relative humidity.Theresults showed that the yearly average solar radiation in the region was 16.37 MJ m .Among the empirical models, the best result was acquired for model (19) with correlation coefficient (r) of 0.9663. Results also showed that the ANN model trained with total meteorological data in input layer (ANN5) produces better results in comparison to others. Root Mean Square Error (RMSE) and r for this model were1.0800 MJ m-2 and 0.9714, respectively. Comparison betweenthe model 19 and ANN5, demonstrated that modeling the monthly mean daily global solar radiationthrough the use of the ANNtechnique, yields better estimates. Mean Percentage Errors (MPE) for these models were 7.4754% and 1.0060%, respectively. -2 day-1
Research Article
Mehdi Jamali Ghahderijani; Fathollah Ommi
Abstract
In this paper, a solar based hydrogen production in the city of Tehran, the capital of Iran is simulated and the cost of produced hydrogen is evaluated. Local solar power profile is obtained using TRNSYS software for a typical parking station in Tehran. The generated electricity is used to supply power ...
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In this paper, a solar based hydrogen production in the city of Tehran, the capital of Iran is simulated and the cost of produced hydrogen is evaluated. Local solar power profile is obtained using TRNSYS software for a typical parking station in Tehran. The generated electricity is used to supply power to a Proton Exchange Membrane (PEM) electrolyzer for hydrogen production. Dynamic nature of solar power and necessity of reasonable accuracy for estimating of amount of hydrogen production leads to propose a new 1D dynamic fluid flow model for PEM electrolyzer cell simulation. The hydrogen price in this system is estimated using Equivalent Annual Worth (EAW) analysis. Although it is convenient to select a yearly useful lifetime for electrolyzer as well as solar cells in this paper an hourly lifetime is considered which allows finding the hydrogen cost based on electrolyzer operating time. Also, electrolyzer sizing is done by selecting various number of cells for each stack and alternatives are compared from performance and economic point of view. In this regards 4 cases consist of 2, 3, 4 and 5 electrolyzer cell are compared. Hydrogen price at each case is evaluated and sensitivity analysis is performed. The results represent that the system with higher efficiency is not always an economical choice. As an alternative, the electrolyzer turning off at some conditions is also investigated for possibility of extending lifetime and reducing the hydrogen price. It is found that turning off the electrolyzer under specified minimum current density (2000 A/m2) in all cases reduce the final produced hydrogen price however this price and electrolyzer size is still strongly dependent to the electrolyzer capital cost.
Mohammad Ahmadzadehtalatapeh
Abstract
Air pre-cooling equipment is normally being employed in air-conditioning systems for pre-cooling the ambient outdoor air to enhance the air-conditioning systems performance. In this study, the potential of a passive water-to-air heat pipe based heat exchanger (HPHEX) for air pre-cooling purpose in air-conditioning ...
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Air pre-cooling equipment is normally being employed in air-conditioning systems for pre-cooling the ambient outdoor air to enhance the air-conditioning systems performance. In this study, the potential of a passive water-to-air heat pipe based heat exchanger (HPHEX) for air pre-cooling purpose in air-conditioning systems for the high cooling load demanding regions of Iran was investigated. To this end, effectiveness-NTU approach was employed to determine the thermal performance of the heat exchanger. Water-to-air HPHEX with different numbers of rows namely two, four, and six was studied to determine the heat transfer characteristics of the heat exchanger. The thermal performance of the water-to-air HPHEX was investigated under different operating conditions in terms of evaporator inlet air and condenser inlet water coil face velocities and temperatures. After determining the thermal performance of the water-to-air HPHEX, the air pre-cooling capability of the water-to-air HPHEX was explored hour-by-hour for the required months of the year by using TRNSYS software. Based on the simulations results, the water-to-air HPHEX shows an acceptable thermal performance under the operating conditions. In addition, studies showed that the water-to-air HPHEX has a significant capability for air pre-cooling, which makes it applicable to be implemented in the air-conditioning systems operating in south of Iran.
Research Article
Imologie Simeon; Raji O. A.; Agidi Gbabo; Cynthia Okoro-Shekwaga
Research Article
Afshin Lashkar Ara; rahil hosseini; Hajar Bagheri Tolabi
Abstract
In this paper, a novel approach for the estimation of global solar irradiance is proposed based on a combination of empirical correlation and ant colony optimization. Empirical correlation has been used to estimate monthly average of daily global solar irradiance on a horizontal surface. The Ant Colony ...
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In this paper, a novel approach for the estimation of global solar irradiance is proposed based on a combination of empirical correlation and ant colony optimization. Empirical correlation has been used to estimate monthly average of daily global solar irradiance on a horizontal surface. The Ant Colony Optimization (ACO) algorithm has been applied as a swarm-intelligence technique to tune the coefficients of linear and nonlinear empirical models. . The performance of the models is investigated for the estimation of global solar irradiance at four different climatic regions of Iran based on statistical indicators like coefficient of determination (R2) and root mean square error (RMSE). The results obtained from the proposed model are superior in comparison with the other well established models.
