نشریه انرژی ایران
سال بیستم شماره 2 (پیاپی 75، تابستان 1396)

In this study, the performance of a solar greenhouse heating system equipped with a linear parabolic concentrator and a dual-purpose flat plate solar collector‏ was investigated using the Artificial Neural Network (ANN) method. The heat required for the greenhouse at night hours was supplied by the heat stored in the storage tank by the solar system during the sunshine time and  an auxiliary heater. A water pump was used to make a forced-flow through the concentrator assembly. While, a natural water flow occurred in the flat plate collector. ANN method was used to predict  the tank temperature and energy consumption from the heat storage tank and by the auxiliary heater. Network inputs were solar radiation intensity, ambient temperature, wind speed, collector surface temperature, greenhouse temperature, flow rate and time. About 80% of total data were used for training, 10% for testing and 10% for validation. The results indicated that the network topology of 7-15-1 with R² and MSE of respectively 0.98 and 0.00017 presented the best results for prediction of energy consumption from the tank. While the most suitable description for variations of energy consumption by the auxiliary heater and from storage tank was given by the network topologies‏ of 7-10-10-1 (with R² of 0.99 and MSE of 0.00014) and 7-5-15-1 (with R² 0.98 of MSE  of 0.00011), respectively.

This paper presents a novel identification technique for estimation of unknown parameters in photovoltaic (PV) systems. A single diode model is considered for the PV system, which consists of five unknown parameters. Using information of standard test condition (STC), three unknown parameters are written as functions of the other two parameters in a reduced model. An objective function and a set of inequality constraints are defined for the reduced model considering limitations of the physical system. It is shown that the non-convex optimization problem of PV systems is converted to a convex constrained optimization one. The constraints are enforced using a modified barrier function that generates an augmented objective function. An adaptive identification technique is utilized to find the optimal values of the augmented cost. Unlike most identification techniques, the proposed algorithm has a precise and unique solution, which is easy to implement. The effectiveness of the proposed approach is confirmed using some simulation and experiments.

In 2010, the global transport sector consumed about 2,200 million tons of oil equivalent. About 96% of this amount came from oil. It shows that more than 60% of the oil consumed globally goes to the transportation sector. Road transport accounts for the bulk of the transportation energy consumption. The light-duty vehicles (LDVs), including light trucks, light commercial vehicles, and minibuses accounted for about 52%. World Energy Council (WEC) has re-examined the future of the transport sector by building Global Transport Scenarios to 2050 “Freeway” and “Tollway.” The “Freeway” scenario envisages a world where pure market forces prevail to create a climate for open global competition. The “Tollway” scenario describes a more regulated world where governments decide to intervene in markets to promote technology solutions and infrastructure development that put common interests at the forefront. In 2050, total fuel demand in all transport modes will increase by 30% (Tollway) to 82% (Freeway) above the 2010 levels. Transport sector fuel mix will still depend heavily on gasoline, diesel, fuel oil and jet fuel.

For decreasing the amount of air pollution and green gas emission and saving fossil fuels resource, one of the ways is extending renewable energy utilization. Hence, this yields to growth and development of Photovoltaic systems. Nowadays due to increasing electrical energy requirements and ability to privately providing required energy, the use of solar energy and its electrical power creativity by means of PV systems expanded. In this study an electricity network independent system designed to provide electricity for a house around Karaj at a certain season of the year. The energy demand for this house is 4320 Watt-hours. For providing this amount of energy, 830 watt photovoltaic array, a 1500-watt inverter, a charge controller with a capacity of 40 amp and 24 volt battery with 600 amp hour capacity is needed. The cost needed for this project estimated about 103700000 Rials. PVsyst software used to calculate system losses and finally environmental impact of system compared with conventional systems.

Climatic conditions have a significant impact on the energy consumption of  buildings. Also check the angle of the solar radiation on buildings and controlling the amount of heat absorbed on building shell during the year have significant impact on building energy efficiency. The aim of this study was to investigate the effect of orientation of the building on the energy consumption and to this meaning, in the first, heat absorption rate was determined by body of building. This study has been done with the aim of analyze the impacting of solar radiation and heat absorption the as an most important factors to energy consumption of building.  In this study, first the temperature and sun radiation angle was determined by climatal softwares and then the amount of getting temperature of body of building in different directions 0-90 degrees and 270 -360 degrees were studied with the using of design Builder software (the software of energy simulation) and according to the annual energy consumption of buildings in different modes, the optimized placement of building was determined in Isfahan. The results showthat  the amount of radiation that reaches to a surface, depends on the intensity of solar radiation and radiation with surface contact angle. As more solar radiation intensity and angle relative to the surface is vertical, the amount of getting energy and thus heat generated on the surface will be more.

The solar arrays  are one of the most promising renewable energy technologies for providing energy needs . in buildings. For installed solar panels on building roofs, knowing the optimal inclination angle is important in order to obtain the maximum annual or seasonal energy. In fact, the changes in slope angle affect the amount of solar radiation that reaches the surface of the panel. In this study,  various models were used to obtain optimal tilt angle and azimuth angle in solar panels installed angle in Mashhad. Using ayzrvtrvpyk isotropic model, the optimal angles for various months, seasons of the year were deterimend. Also,  panels’ optimal slope and azimuth angles in Mashhad were calculated and determined using non-isotropic model. In general, the total annual energy achieved by panels equipped with a single axis  and dual axis sun tracking system  could increase by 16%  and 30%, respectively, compared to what achieved by fixed angle solar panels.

The exterior envelope of buildings play a significant role on the amount of energy consumption in office buildings that are located in warm climates. The present study focuses on the reduction of energy consumption by integrating daylight and artificial lights, and by changing the characteristics of exterior envelope of buildings including window coverage and dimension of buildings. Moreover, the study focuses on the impact of mentioned parameters on the cooling load and lighting in office buildings. For this study, a typical office building located in warm climate is simulated, using the software eQUEST. It is found that by changing the window type (glazing and coverage) and integration of daylight with artificial lights, a significant reduction occurs in the amount of energy consumption. In this article, an office building is simulated with insulated double window transparent that has fins and overhangs with ratio of northern-southern to eastern-western side equal to four.  By using daylight to provide some parts of lightings, a reduction of 45%, 16% and 20% is found on lighting, cooling and total energy consumption, respectively. This energy reduction is compared with a building that uses clear windows with no daylight being used to provide lighting in the office building.