Journal of Renewable Energy and Environment
Volume:4 Issue: 1, Winter 2017

One of the subjects in solar water heater design is considering distribution of hot water consumption during the day. For example, each of the household, commercial, office, school, and industrial consumptions have a particular distribution of hot water consumption named pattern in this article. In solar computation principles, the effect of longitude, latitude, and altitude on collector angle has been clearly presented. However, the effect of consumption pattern especially on the collector orientation has been rarely investigated. The aim of the current study is to survey the effect of various consumption patterns on the collector’s orientation and tilt angle and so calculation of related energy saving. So, five common patterns including office building, commercial building, afternoon and morning shift high school and a 15-unit apartment have been studied and optimal surface azimuth angle and tilt angle determined. It has been observed that 11 to 14 % energy saving can be archived by selecting the optimal angles with respect to hot water consumption pattern in comparison to a state that collectors are orientated for maximum reception of solar energy. Also effect of solar fraction, storage volume and amount of hot water consumption are studied and discussed.

Thermal modelling and optimal design of a solar absorption cooling system are presented, and hourly analysis is performed over the period of a year. Three design parameters are considered, then the Real Parameter Genetic Algorithm (RPGA) is applied to obtain the minimum total annual cost. The optimization results show that the solar cooling optimum configuration needs 1630 square meter collectors, a storage tank with a 15000L capacity as well as an absorption chiller with 300kW capacity. The hourly analysis shows that the space temperature fluctuates on average every 62 minutes during June and decreases to 51 minutes in September. In addition, the optimum number of collectors increases 26.67% given a 50% increment in electricity price while it decreases 20% given a 50% decrement in electricity price. Finally a sensitivity analysis on RPGA parameters is performed and results are reported.

The most common controller in wind turbine is the blade pitch angle control in order to get the desired power. Controlling the pitch angle in wind turbines has a direct impact on the dynamic performance of the machine and fluct­uat­io­ns in the power systems. Due to constant changes in wind speed, the wind turbines are of nonlinear and multivariate system. The design of a controller that can adapt itself with the system, at any given time, is of crucial importance. To limit the aerodynamic power gained from the wind turbine in the high wind speed areas, different methods has are applied on pitch angle. In this paper an extensive literature review on pitch angle control technique in wind turbine has been highlighted. Classical and adaptive controllers, structure control, robust control and intelligent control are among the con­trol methods adopted in this study. In comparison of the controllers, although adaptive and robust controllers, with less sensitivity to changes in environmental conditions, outperform the classic controller, the intelligent controller system pre­sents the best performance of the wind turbines through estimating the system variables and appropriate adaptation to cha­nges at the operating point.

This paper describes the effect of temperature on the electrical parameters of polysilicon solar cells, which are fabricated using the phosphorous spin-on diffusion technique. The current–voltage characteristics of polycrystalline silicon solar cells were measured in the dark at various temperatures. A diode equivalent model was used to obtain saturation currents, which were measured for the different temperature levels .The experimental results showed that the saturation currents increased rapidly from 0.00003 to 0.0005A on increasing the temperature from 27 to 70 ˚C. The changes in the open circuit voltage and the short circuit current were found to be linear with the temperature variations: about 3 mV/˚C reduction in the open circuit voltage was observed with the temperature increase. The measurements of the short circuit current revealed that the dependency of the current on the temperature variations was very small. The short circuit current increased from 17.8 to 18.4 mA on increasing the temperature from 27 to 107 ˚C. The measurements of output powers versus load resistance were obtained at different temperature levels. The results showed that the output power dropped 30% with temperature rise from 27 to 107˚C.

Nowadays, proton exchange membrane fuel cells (PEMFCs) have emerged as promising power supply systems for stationary, vehicular, and portable applications. Traditionally, these devices were based on perfluoro-sulfonic acid membrane electrolytes, given the commercial name Nafion. Nafion is currently the most commercially utilized electrolyte membranes for polymer electrolyte fuel cells, with high chemical stability, proton conductivity and strong mechanical properties. While these polymer electrolytes have satisfactory properties for fuel cell applications, they limit commercial use due to significant high costs as well as reduced performance at high temperatures and low humidity. A promising alternative to obtaining high-performance proton-conducting polymer electrolyte membranes are through the use of hydrocarbon polymers. Various studies in the open literature confirmed that Sulfonated poly ether ether ketone (SPEEK) is a promising PEM because of its low-cost, low fuel cross over, and good mechanical and thermal stabilities. Nevertheless, depending on the variation of the sulfonation degree (DS), the mechanical properties of SPEEK membranes could deteriorate progressively (at higher DS). To solve this key issue, SPEEK has been used as a major component in the synthesis of hybrid/blend membranes. The introduced inorganic particles to the polymer membranes might be silica, zirconia, titania, heteropolyacids, carbon nanotubes, and so on. Increased proton conductivity, water retention at high temperatures, chemical, and mechanical properties are mentioned as some advantage of incorporating inorganic material into hybrid membranes. Indeed, the addition of an inorganic material into SPEEK matrix could improve the physicochemical properties of the resulted composite membrane such as proton conductivity, hydrophilicity, thermal, mechanical and chemical stability. High mechanical and thermal stability, electrical and magnetic activities are provided by inorganic segments, while the organic segments provide flexibility, multi-functional reactivity, and facilitate machining at low temperature. SPEEK blends have a good potential to alter Nafion at high-temperature operating conditions. In this paper, we focus on the recent advances in the development of novel SPEEK-based hybrid membranes that work well under elevated temperature and/or low relative humidity.

Renewable systems influence the process of supplying domestic electricity needs. Since uncontrolled use of fossil fuels is accompanied by global warming and environmental hazards, in addition to the danger of their depletion, and because most of the energy derived from these fuels is utilized in buildings, it will be useful to replace the current energy generation system by utilizing renewable energy sources. Although other researchers have dealt with issues such as solar energy (active and passive), wind turbines, and other methods for supplying domestic energy needs, studies on hybrid systems that include biomass have attracted significantly less interest. Therefore, considering the historical background and the potential of biomass in Iran, this article assesses the potential of using a hybrid solar cell/wind turbine/biomass system for supplying electricity needs of a residential building in each of the four Iranian climates. The question of which system based on renewable energies would be the most cost effective in each Iranian climate has not yet been studied. Results indicate that, based on cost-effectiveness, the ideal options are utilization of solar cells in the cold, warm and dry, and warm and humid climates, and use of systems based on biomass in the moderate and humid climates.