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Due to the short distance between the sources of production and consumption, microgrids (MGs) have received considerable attention because these systems involve fewer losses and waste less energy. And another advantage of MGs is that renewable energy sources can be widely used because these resources are not fully available and can provide a part of the required power. The purpose of this research is to model the MG considering the production sources of microturbines, gas turbines and internal combustion engines. Renewable energies such as wind turbines (WTs) and photovoltaic (PV) cells have been used to provide part of the required power and, because of the lack of access to renewable energy sources at all times, energy reserves such as batteries and fuel cells (FCs) have been considered. The power of the microturbine, gas turbine, internal combustion engine, FC and battery in this system is 162, 150, 90, 100 and 225 kW, respectively. After modelling the studied system, optimization was done using the imperialist competitive algorithm to minimize production costs and provide maximum thermal and electrical loads. The maximum production power for PVs is equal to 0.6860 MWh and at this time this value for WTs is equal to 0.3812 MWh, in which case the excess electricity produced will be sold to the grid. [ABSTRACT FROM AUTHOR]

In this study, based on the energy balance for different components of a double-layered vacuum-tube solar collector with a U-tube, the thermal performance of the collector unit is investigated separately using an analytical and quasi-dynamic method. The model used in this study determines the temperature distribution in longitudinal and radial directions. In this research, the effects of physical parameters and heat transfer including the size of the collector, thermal-loss coefficient, absorption coefficient, mass flow and thermal resistance of the air layer under different climate conditions have been evaluated on the performance of the vacuum-tube collector. The results showed that by increasing the diameter of the tube with constant length, the annual thermal efficiency of the collector increased. Also, in a fixed-diameter tube, with increasing tube length, the annual efficiency increases, but this increase is meagre for lengths of >1.5 m. The optimal mass flow rate for maximum efficiency has been obtained for cities with different climates. According to the results, the optimal flow for different climates has different values that can be optimized as a relationship between the average solar radiation annually as a symbol of temperature and flow. [ABSTRACT FROM AUTHOR]

Using combined cooling, heat and power systems can be an appropriate substitute for preventing emissions of pollutants and excessive consumption of fossil fuels. Utilizing renewable energy in these systems as a source of power generation can be an appropriate substitute for fossil-fuel-based systems. Therefore, in this paper, cogeneration cooling, heat and power systems based on gas-fired internal combustion engines with a solar-thermal system with evacuated tube collectors have been modelled and thermo-economic analysis has been done to compare fossil-fuel-based systems. The required rate of heat to supply the hot water is 50 kW. In the studied system, the internal combustion engine produces electrical energy. Then, the solar-thermal system with evacuated tube collectors and the gas-burning generator provide the thermal energy required by the studied building and the primary stimulus of the absorption chiller for cooling. In this study, two different scenarios are conducted in states considering simultaneous production systems and regardless of this environmental and thermo-economic analysis system. The results showed that the efficiency of the studied system was 60% in summer and 56% in winter. [ABSTRACT FROM AUTHOR]

Today, the use of alternative fuels that have plant origin has attracted the attention of most countries because these fuels emit less pollution. In this research, bioethanol production has been evaluated considering solar energy sources. In the present study, the possibility of developing net-zero energy concepts in a bioethanol production plant as one of the most consumed energy industries in the field of bio-systems of the country from a technical and economic perspective was investigated. The purpose of this research is to model the bioethanol production plant with the aim of achieving zero net energy using a photovoltaic system. In addition, technical and economic analyses have been used in different approaches for a more detailed investigation. According to the modeling done, in the zero net energy approach, the results showed that the maximum production of electrical energy by the photovoltaic cell is 76.6 GWh/y. For this approach, the return on investment is 10.7 years. The area required to install photovoltaic modules in this approach is very large and equal to 88 334 m2. [ABSTRACT FROM AUTHOR]

The use of solar energy is highly welcomed due to its availability everywhere. Among the types of solar energy technologies, the use of this type of energy to produce heat from different aspects is much more common, so in this research we have tried to examine different aspects of producing thermal energy from solar energy to supply the heat required by the pool. For this purpose, numerical modelling of the solar pool has been done by considering the heat-transfer characteristics and validation has been done to ensure the obtained results. In this paper, according to the physical realities facing solar systems in two scenarios, an analysis with shadow and without shadow has been done. One of the important results is that as the surface of the pool increases, the amount of heat absorption by the pool fluid will increase, but the effect of the shadow will decrease. [ABSTRACT FROM AUTHOR]