Journal of Selected Topics in Energy

Different Generations Of Solar Cells and Mechanisms of Their Performance

Burhan Azarm

Solar energy is the most important type of modern and renewable energies. If it displace fossil fuels, can bring an end to concerns about finiteness of fuels, environmental pollution caused by the fossil fuels, price fluctuations and energy crisis. Among the energy sources, due to the high potential of solar energies in wide areas of the Iran, it has a great importance to researchers. The base of Photovoltaic technology is to converting sunlight into electricity and nowadays, most of the countries utilize it in the forms of grid-connected and off-grid. In recent years, few technologies are used for manufacturing of solar cells. The results of investigating show that the efficiency of the first generation in comparison to the other technologies are high due to the high quality raw materials which are used in the fabrication. It is expected that the differences between the efficiency of these for technologies will be decreased by the time and other technologies will be replaced by the first generation. In this paper, the structure of different technologies has been studied and the possible methods for improvement of the solar cells efficiency have been introduced.

Numerical Study of The Melting Temperature Effect on The Performance of Phase Change Materials (PCM) to Reduce Buildings Energy Consumption

Behrang Sajadi

In this study, the effect of using phase change materials on the air-conditioning system energy consumption of a typical room in a multi-floor building has been studied using EnergyPlus software. As the melting point of PCMs has an important impact on their effectiveness, as a part of this research, the effect of Iran climatic conditions on the appropriate melting point of the PCM has been investigated in 4 cities: Tabriz as a cold, Tehran as a moderate, Yazd a dry-hot and Bandar-e-Abbas a humid-hot climate. Based on the results, the proper temperature of PCM melting temperature is between 21 to 27°C and the saving varies from 1.6 to 13.2%. The results of this incestigation are useful in getting better understanding of the effect of PCMs on reducing the HVAC system energy consumption and in determining the PCM appropriate specifications.

Study of Glass Performance in Improving Efficiency of Trombe Wall Heating Technology

Seyyed Hossein Hashemi

The Trombe wall heating system known as one of the most important consumption reduction technology that utilizes solar energy is the energy efficiency. In this paper, the effects of temperature on system performance Trembath glass wall temperature of wall heating Trembath according to the intensity of solar radiation is investigated numerically. The results confirmed the increase in efficiency heating system with regard to solar radiation intensity emitted in the study area. With such intensity 466.281 w / m² close to the glass surface temperature (in air duct) up to 14.422 ° C arrives while lower-intensity radiation (394.91 w / m²) in the final heat to about 12.71 ° C goes. Considering the solar radiation, can be expected to increase the flow of thermal energy in the air duct. The effect of improving the efficiency of the underlying performance heating technology Trembath wall. The results of this study, changes in temperature glass, to the the amount of solar radiation intensity in the relationship. When the radiation intensity maximum the amount of 466.81 w / m² is concerned, more secondary radiation is emitted. As a result, the glass has a temperature range between 11.32 to the 12.73 ° C.

Design, Construction and Empirical Investigation of Thermal Performance of A Heat Pipe

Mojtaba Tahani

In this work thermal performance of a cylindrical heat pipe at steady state has been investigated empirically. The used heat pipe, made of copper, has been designed and manufactured by considering effective parameters on heat pipe thermal performance. Then heat pipe has been charged by water as the working fluid. By installing sensors and the other equipment, the test set up has been prepared. After preparing the test set up by changing voltage, various input powers have been inserted into evaporator and the heat pipe surface temperature distribution has been obtained for each case. Then by using the obtained temperature distributions, thermal resistance variations and equivalent thermal conductivity coefficient have been computed. and variation of them versus input power have been plotted. The results show that the thermal resistance has its minimum value at maximum operating limit (maximum passing power) and equivalent thermal conductivity has its maximum value at this point.

Optimization of Energy Cost in Water Supply Systems Using Genetic Algorithms

Rasoul Rajabpour

In this paper, the optimal operation of pumping stations was determined using a genetic algorithm so that the minimum energy cost. The schedule for the operation of the water pump system can be a significant savings in the cost of energy to be achieved. Determine the optimum pump operation schedule an optimization model - simulation-based genetic algorithm was developed. The model integrates GA optimizer and EPANET hydraulic network solver in MATLAB. The proposed model is applied to find the optimal pump operation schedule of Dogonbadan water conveyance system from Kowsar Dam in an ordinary day of the year. The comparison of optimal schedule with ordinary operation strategy shows 26.8 percent reduction in total energy cost. This indicates the high capability of the proposed model.

Experimental Study of Centrifugal Pump Energy Label

Javad Zare

Nowadays, according to increasing energy consumption especially in industry, the need for optimizing energy consumption and determining energy efficiency class of different devices is essential. The main challenge of the present study is developing an energy label instruction for centrifugal pumps. Since the used standard in Iran (ISIRI 7817-2, 1st.edition) only considers the effect of efficiency in energy labeling, a new method is presented to modify this standard. In the proposed method the effect of specific speed on efficiency is considered by choosing one of the constant specific speed curves in η- Q diagram and modifying efficiency for each specific speed. Then, different pumps are tested and labeled by different standards. While the used standard in Iran labels all the pumps in one class, but the new proposed method can label pumps properly as European standards that show the benefit of using the proposed method in centrifugal pumps energy labeling.