The overwhelming growth in energy consumption in Iran is to the extent that in the coming years, it will turn Iran from an energy-exporting country into an energy-importing country. The use of renewable energy is essential to address this threat. In this research, the energy and economic analysis of solar energy-based cogeneration system for a building in Saveh City has been studied. The main purpose of this study is to determine the optimal size of photovoltaic cell and solar water heater by considering environmental parameters and fuel saving. In this regard, the amount of solar radiation intensity and the required loads of the building under study were determined. Then, using the SAM and TSOL relationships and software, results such as the supply of electric and thermal loads of six panels of 327 W and 3.2 m2, respectively, are needed. This system will save more than 75% energy.

Purpose The important factors, which should be considered in the design of a hybrid system of photovoltaic and wind energy are discussed in this study. The current load demand for electricity, as well as the load profile of solar radiation and wind power of the specified region chosen in Iran, is the basis of design and optimization in this study. Hybrid optimization model for electric renewable (HOMER) software was used to simulate and optimize hybrid energy system technically and economically. Design/methodology/approach HOMER software was used to simulate and optimize hybrid energy system technically and economically. Findings The maximum radiation intensity for the study area is 7.95 kwh/m2/day for July and the maximum wind speed for the study area is 11.02 m/s for January. Originality/value This research is the result of the original studies.

Summary The short‐cırcuıt capacity design of a transformer is one of the most significant and challenging criteria. Electromagnetic forces in transformer winding regions are produced by interaction between the leakage flux and current density. Under short circuit condition when currents increase to 20 times, windings are exposed to very high electromagnetic force. This paper is focused on the reduction of leakage flux and electromagnetic force under fault condition of distribution transformer. This article is composed of two parts. First, Finite Element Methods (FEM) that improved in Ansoft‐Maxwell has been used to investigate the leakage flux and electromagnetic forces of three‐phase, three leg, 10/0.4‐kV, 1000‐kVA distribution transformer. Then, to optimal design of transformer under single phase to ground short circuit condition two auxiliary winding was chosen as an active shielding to reduce the radial and axial leakage flux. According to Lenz's law this windings produce a magnetic flux that is the apposite of the leakage flux from an iron‐core system. Results indicate that the proposed auxiliary winding remarkably decreased the leakage flux and electromagnetic force in the winding regions. It should be noted that the resultant of main flux is not affected by auxiliary winding. Copyright © 2015 John Wiley & Sons, Ltd.

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