نشریه انرژی ایران
سال چهاردهم شماره 4 (پیاپی 53، زمستان 1390)

Financial derivatives do not represent ownership rights in any asset but, rather, derive their value from the value of some other underlying commodity or other asset. They are claimed to be efficient and effective tools for hedging against risk exposure. In many countries, use of derivatives in electricity industry has come about with electricity price deregulation. In electricity market, risk of price fluctuations threatens electricity consumers and producers. While, varying prices encouraged consumers to find ways to reduce their costs, and producers looked for ways to stabilize cash flow, derivative contracts were introduced to transfer price risk, to those who are able to bear it. Price risk management in electricity industry is relatively a new phenomen. However, electricity derivative contracts have grown rapidly. In this article, we will introduce various kinds of financial derivatives (such as Forwards, Futures, Options, and Multiple-Trigger Derivatives), commodity characteristics of electricity and price risk management methods with derivatives in the electricity industry.

Life cycle assessment (LCA) is an effective tool for decision-making, which could assess and analysis the environmental impacts. Also, appropriate approaches with less environmental impacts could be indicated by LCA. There are some procedures and plans in order to strengthening LCA, which could quantify the environmental impacts of a product or process in the whole of life cycle. One of these strengthening methods is EPS (Environmental Priority Strategies). Environmental impacts could be calculated and compared for different emissions, resources and energy use by EPS system. In order to comparing environmental impacts of resource use, transportation and raw material use, environmental impacts should be quantified. The unit for comparing environmental impact in EPS system is ELU (Environmental Load Unit). In this paper, environmental impacts of air pollutants in life cycle of a combined cycle power plant have been quantified by EPS. The results show that the most important environmental impact based on ELU are respectively CO2, CH4, PM, NOx and SO2.

Lack of technical and economic efficiency of energy consumption and waste nearly a third of all energy and environmental problems arising thereafter, consumption management, increase efficiency and make energy efficiency more than ever necessary. In order to use and feasibility of improving energy efficiency and management programs in Iran and other countries in efforts to resolve the problems, in this paper has three separate sections, to be paid part of the main issues in this regard. In the first part of this paper to examine strategies for reducing energy consumption, it is necessary to accurately complete, the types of strategies are identified and explained. Initially the strategy or strategies, and more defined because the developmental nature of the issue optimization of energy consumption, classification strategies in this regard are presented. On this basis, in the first part conclusion contents, context and methods of assessment strategies to optimize the energy consumption as a model presentation for specified countries and Iran are also being offered. The second part, the strategies optimization of energy consumption sample countries and Iran are paid. Presentation and analysis of these strategies individually to any country due to the massive contents, is outside the scope of this article, but in such conditions, Total of energy consumption optimization strategies as conclusion by (the study of a country) is given and finally, in third part of this paper, the strategies is recommended to reduce energy consumption in Iran.

In this paper, based on geographic specifications and climatic conditions, the required natural gas and hot water of a typical 8-units residential building located in Tehran city, has been taken into consideration and analyzed in two scenarios considering the national and international prices of natural gas and electricity. In scenario A, utilization of a forced circulation solar water heating system for supplying the required hot water based on national prices for electricity and natural gas and in scenario B, utilization of the same system considering international prices for electricity and natural gas were investigated through using RETScreen software. The results show that in scenarios A and B, the share of solar water heating system in supplying the required hot water is 53%. The amount of natural gas saving would be 4,777 m3/yr. The total investment costs and green house gases (GHGs) emission reduction would be US$ 7,898 and 6.4 tCO2/yr respectively. In scenario A, annual external costs diminution would be US$ 123 tCO2 and normal payback period would be 16.9 yr. In scenario B, annual external costs diminution and normal payback period would be US$ 101 tCO2 and 6.3 yr respectively. Thus using the solar water heating systems with considering the international prices of electricity and natural gas is economically feasible.

Hybrid system are power production systems, in which a thermal engine like a gas turbine is combined with a non thermal engine like a fuel cell. As such systems have higher efficiencies and lower contaminants than a gas turbine alone, they will play a great role on advanced power production system in near future. With using thermal energy of Solid oxide fuel cell in a gas turbine cycle can be achieved a hybrid system with high performance. In this paper, we investigate the thermodynamic performance of gas turbine combined system with oxide fuel cell with hydrogen-fueled internal improvement in design point and prediction power and efficiency system in off design point in order to find corresponding operating point on the characteristics of each component when the engine is running at a steady state speed or in equilibrium as it is frequently termed. All components of the hybrid system has been modeled separately, with the help of thermodynamic relations.

In this paper, derating factor of induction motors that are subjected to regular fluctuations (flicker) has been calculated. Voltage flicker is one of the most important phenomena in power systems study. The phenomenon may cause additional losses and decrease the efficiency of the induction motors. Due to huge amount of induction motors in the different industries, it is important to study the effect of voltage fluctuation on the induction motors behavior. The paper applies electrical, mechanical and thermal models of induction motors to estimate additional losses, temperature rise and derating factor.

The main objective of this study was to design a solar fluidized bed dryer for agricultural products, and to investigate its performance with regard to solar radiation rate. The agricultural products were dried using solar radiation instead of fossil fuels, with highest quality and at very short time; this is due to high heat transfer rate of this dryer. The agricultural materials used for drying were corn kernels, where mean corn size, bed porosity; bulk and net density were obtained experimentally. On the basis of initial and secondary moisture content of the corn kernels, three flat plate solar collectors of 5.4 m2 with 1.66 kW of thermal power and a spiral air blower with 0.146 m3/s were used. Drying experiments were carried out in a bed height of 1 cm and air velocity of 3.5 m/s using two types of distributer screens, of 2 and 4 mm mesh size, at before noon, noon and after noon, in order to obtain the dryer performance. Results showed that the drying kinetics of corn kernels is affected by using various distributer screen mesh at different experimental time.