Journal of Solar Energy Research
Volume:2 Issue: 1, Winter 2017

Ancient wind catchers of Yazd city as net zero energy building components request the detailed numerical and experimental studies to renovate and reuse in old part of the city and for developing the new design strategies in future. In this ingenious natural ventilation strategy no other energy sources are required except wind and sun. In this research, the effect of both wind and sun on the flow and thermal behaviour of the solar-wind catchers of Yazd city - a city with very high solar radiation - in Iran, are investigated numerically and experimentally. This paper represents a systematic evaluation of isothermal 3D CFD modelling for predicting mean air velocity distributions over and through the wind catcher at three reference wind directions of 330°, 90° and 150°, using Open source CFD package (OpenFOAM). The evaluation is based on a grid-sensitivity analysis and on validation with full scaled long term measurement data set. The validated CFD simulation results show that steady RANS with Standard k−ɛ model, in spite of its limitations, can accurately predict the flow behaviour of wind catchers at wind direction of 90° with the average deviations of 19%, which is considered a good agreement against the long term experimental results. Moreover, the thermal behaviour of wind catcher during a summer day is discussed. The study reveals that the solar wind catchers of Yazd city, is quite effective in lowering air temperature and enhancing air circulation through the buildings. The result of this study will be useful for designing solar-wind catchers under hot and dry climate conditions.

The aim of this paper is to introduce a design and build of a small low cost CSP system with simplicity in construction as a means of power generator for remote areas and residential buildings. Advantages of the designed device are: There are no curvatures, instead of that some flat mirrors are installed in a rectangular Aluminum frame. In order to reach higher efficiency, a cavity receiver and a two axial sun detector system is used. Also a modified turbocharger is playing role as an expander. By making required number of the collector panels parallel (or series) the requested output power or mass flow rate can be achieved. The results show that the maximum temperature of empty cavity receiver (without working fluid) is around 710 degrees Centigrade. Hence, the effectiveness of the receiver is about 92% by calculations. For 6.2 m2 collector panel, output is 1 KW and the cost is estimated to be roughly around $1350. Also there is another output which provides hot water for heating purposes.

Solar pond is an artificially constructed pool by which the solar energy is collected and stored in a cost-benefit approach compared to conventional solar energy collection methods. Salt gradient solar pond, capable of providing a considerable quantity of hot water, has received wide currency in both research and industrial fields. Heat absorbed in the salt gradient solar pond can be extracted in different ways for various thermal applications, ranging from domestic to industrial uses. Thermal efficiency as a key criterion for evaluation of the performance of the pond, is directly influenced by the method applied to extraction of the heat. Investigation of the performance of a solar pond requires a comprehensive thermodynamic study through energy and exergy analyses based on the first and second laws of thermodynamics. Such observations have been aimed at achieving higher efficiency and effectiveness of the system. The present article presents thermodynamic analysis for performance investigation of salt gradient solar ponds in all three zones including theoretical and experimental results.

In this paper, a control approach for enhancing the characteristics of a microgrid system is presented. This microgrid includes a PV system in its DC link beside a DC/DC convertor as the interface for connecting to the system inverter. Due to this, the dynamics of the PV system is also considered. The capability of this control system in maintaining the significant feature of system signals under non-linear load or load variation is also investigated. The secondary controller in this system is designed to not only restore the system voltage and frequency but also preserve the value of active and reactive power before and after its operation. The simulation results show the capability of this control system in maintaining the system performance.

Forecasting PV power generated by photovoltaic panels (PV) in cloudy conditions is of great importance. The aim of this paper is to forecast the produced power by PV using LOLIBEE (Local Linear Bee Model), MLP-ABC (Multi-layer perceptron - Artificial Bee Colony) and MLP algorithms. Experimental data (ambient temperature, solar radiation, speed of wind and relative humidity) are collected at a five-minutes interval from Tehran University’s PV laboratory from September 22nd, 2012 to January 14th, 2013. Upon validation of data gathered from the lab, 10665 data which are equivalent to 35 days are used in the analysis. The output power of PV was forecasted by constructing three models for different parts of a day using LOLIBEE, MLP-ABC and MLP algorithms (three models for each algorithm), which resulted in better precision by LOLIBEE with about 95% and 1.9 in terms of R2 (Co-relation Co-efficient) and MBE (Mean bias error) respectively.  The accuracy gained by our proposed model for dividing the day into three durations is also increased by about 1.5 percentage in comparison with the model which is covering the whole day.

Solar energy is rapidly gaining attention in different industries, especially agricultural industries. Application of this clean energy in drying industry resulted in many investigations in academia. Dryers with energy storage can reduce thermal fluctuations of solar irradiations and also enhance drying efficiency of agricultural products. In this study, paraffin phase change material has been used as energy storage and the performance of a solar tray dryer with indirect forced convection has been investigated. The mathematical model of the energy balance for the process has been derived. The effect of parameters namely inlet air velocity and collector surface area on the final moisture content of samples and air outlet temperature have been studied. Air inlet temperature has been tested at two levels of 1 and 3m/s using a collector surface area of 2m2 with and without energy storage. The integration of energy storage enhances the efficiency by 37% and reduces the outlet moisture content. Lower inlet air velocity and larger collector surface area results in lower final moisture content of samples. On the other hand, for higher ambient temperature even higher inlet air velocity can result in lower moisture content of products. Comparison of experimental data with simulation results shows correlation coefficient of 96.27.

The sun position during building heating and cooling annual period has a major influence on the energy efficiency performance and must be adequately taken into consideration in the design process. Recently, in big cities the design and construction of energy efficient buildings has become a priority. This goal can be accomplished if natural resources such as solar radiation are wisely exploited. The real challenge, is to find clever compromises between urban and building design. For example, one of the major issues that causes trouble for people living in residential districts is insufficient solar gain and natural lighting of building interiors. Shadings caused by neighborhoods induces improper lighting condition and high energy consumption. These shadings can be caused by buildings, placed in opposite side of alley, although the design is performed in accordance with urban regulations. Shading could have positive effect on building's energy efficiency in summer, while its impact is disastrous in winter. Sun path drawings show that the shading effect of opposite side buildings is not considerable in summer, due to high solar altitude angles in Iran's central cities. In this study, after defining buildings typology, construction materials and window to wall ratios in Isfahan City, simulations are conducted with the aid of Energy Plus software, to investigate the influence of different parameters, such as opposite building's height on energy performance (annual heating and cooling loads). Daysim software was also used to compare daylight factor in sample model. The results show that urban codes, where the solar latitude during the heating and cooling period is not taken into consideration, should be optimized in regard to width of alleys and buildings' heights. As a result, modification of related urban codes must be proposed and setback lines should be optimized to reach more efficient and lively habitats.

Even though human beings feel cheerful and happy when living and working under artificial light, but science have proved that feeling healthy, happiness and well-being is dependent on daylighting conditions in the working & living. One of the major reasons behind it refers to spreading of diseases like bone diseases, rickets, heart failure disease, cancer and stress. Nowadays, inappropriate utilization of daylighting in buildings’ interior spaces resulted encountering sick syndrome for building users. However, the quality of any architectural space designed is measured by the healthy factor of those buildings, that is to say what extend the space adapts daylight in its design process. Presently, there are many softwares available for architects which could be used to analyse building adaptation with daylighting strategies affect the healthy issues outcomes in the built environment. The research finding indicates that daylight has a great impact in human health, psychology, productivity and well- being.