Simulation Model of PV Module Built from Point-Focusing Fresnel Radiation Concentrators and Three-Junction High-Performance Cells

The silicon photovoltaic modules that dominate the market today are constantly being modified, but at the same time, the search for new, more efficient design solutions is underway. The study examined a less popular photovoltaic module built from point-focusing Fresnel radiation concentrators and high-efficiency three-junction cells. The advantage of this type of module is its high overall efficiency, exceeding 30%. The disadvantage is that they require biaxial precision tracking mechanisms because even a small deviation of the direction of direct solar radiation from the perpendicular to the module’s surface causes a large and abrupt drop in efficiency. This type of photovoltaic module structure is often also marked with the symbol C3PV. A mathematical model and simulation calculations were carried out in the Matlab/Simulink package for the C3PV module—the CX-75/200 model based on the “Solar Cell” component. The concentration of direct solar radiation was taken into account. For the module under consideration, experimental and simulation results show the necessity of accurate positioning concerning the direction of solar radiation—deviation of the radiation angle by about 5° causes a very high power loss (by about 92%).

Thermodynamics performance optimization of a hybrid solar gas turbine power plant in Colombia

A thermodynamic model is presented for evaluation of a solar hybrid gas-turbine power plant. The model uses variable ambient temperature and estimates direct solar radiation at different day times. The plant is evaluated in Barranquilla, Colombia, with a solar concentration system and a combustion chamber that burns natural gas. The hybrid system enables to maintain almost constant the power output throughout day. The model allows optimizing the different plant parameters and evaluating maximum performance point. This work presents pressure ratio ranges where the maximum values of overall efficiency, power output, thermal engine efficiency and fuel conversion rate are found. The study is based on the environmental conditions of Barranquilla, Colombia. The results obtained shows that optimum pressure ratio range for power output and overall efficiency is between 6.4 and 8.3, when direct solar radiation its maximum at noon. This thermodynamic analysis is necessary to design new generations of solar thermal power plants.

About the causes of pine drying in the Belarusian Polesje

Тhe results of identifying the causes of mass drying of pine trees in the Belarusian Polesje are presented. The object of the study is its modern generations on the former depleted sandy arable land and in natural conditions of growth. It is revealed that in the conditions of groundwater reduction after drainage reclamation in modern climatic conditions, the increase in the inflow of direct solar radiation in the 21st century was the limiting factor for the suppression of the stem productivity of pine, which led to the death of the stand.

Studying the Changes in Solar Radiation and Their Influence on Temperature Trend in Iraq for a Whole Century

Most studies indicated that the values ​​of atmospheric variables have changed from their general rates due to pollution or global warming etc. Hence, the research indicates the changes of direct solar radiation values ​​over a whole century i.e. from 1900 to 2000 depending on registered data for four cities, namely (Mosul - Baghdad - Rutba - Basra. Moreover, attemptsto correlate the direct solar radiation with the temperature values have been ​​recorded over that period. The results showed that there is a decreasing pattern of radiation quantities over time throughout the study period, where the value of direct radiation over the city of Baghdad 5550 w/m2 was recorded in the year 1900, but this ratio decreased clearly to approximately 5400 w/m2 in the year 2000, which is perhaps due to the increase of general pollution rates in the atmosphere. The results also showed that the city of Rutba recorded the highest annual rate of radiation quantities, and Baghdad with Mosul recorded the lowest radiation ratios compared to the rest of the cities, in addition to that there was a large convergence of radiation ratios between them to some extent. The results showed that there is a sharp drop in radiation ratios, specifically in the years1980and 1990. As for the extent of the relationship for solar radiation with temperature levels throughout the study period, it was found that there is an inverse relationship between them, and this confirms that the cause of high temperatures is not because of increased solar radiation, but it may rather due to other reasons such as increased greenhouse gases.

A Novel Fast Predicting Technique for the Absorptivity of Surface Coating

The most common technique for a surface to have the desired thermo-physical properties or to reflect the desired optical properties is the surface coating. It is used in a wide application area from under the seas to the depths of space. In order for a surface coating to be used, it must have well-defined thermo-physical properties. These properties could be properties that are directly dependent on the material such as heat capacity, heat transfer coefficient and thermal expansion coefficient, as well as material and surface-dependent properties such as absorptivity, reflectivity and transmissivity. Absorptivity is a very important parameter for thermal management of electronics operating under direct solar radiation. Optical methods used to measure the absorptivity are expensive and time consuming methods. In this study, obtaining the absorptivity value of a surface coating with a fast and inexpensive method is investigated. The method consists of two stages; experiment and conduction-based finite element simulation. An aluminum plate with the surface coating to be measured and an aluminum plate with well-known thermo-physical properties without any surface coating are tested in the same environment condition (wind, solar radiation etc.). In the experiment, the time-dependent temperature measurement is taken on both plates separately. Also direct solar radiation and wind speed measurement from the environment are taken. Using these measurements, the FE model is validated and the experiment condition is simulated. The absorptivity of the surface coating is obtained with the iterative solutions made as a result of the analysis test verification studies. The iterative results are presented comparatively with the maximum percent error between simulation and experiment. Consequently, unlike the known methods, the material absorptivity could be measured with a very simple, time efficient and cheap method.

An Evaluation of Annual Luminous Exposure from Daylight in a Museum Room with a Translucent Ceiling

The current study investigates the issue of computer-aided daylight evaluation in a museum room with a dropped translucent ceiling. In this type of room, daylight is admitted through classic windows located in the facade and then distributed in the plenum, which is located above the exhibition space and transmitted through the translucent ceiling into the museum room. This illumination method enables guiding daylight deep into the room, excluding the impact of direct solar radiation. The presented study is based on data obtained through computer-aided daylight simulation by DeLuminæ (DL-Light, ver. 11.0.9) software using the Radiance software for all calculations and real weather data for Wroclaw, Poland. A museum room of 12 × 12 m with three different heights of the plenums was simulated to establish an optimal relation of the width to height plenum ratio. Next, the annual exposure in K lx·h/year was calculated, as sensitive works of art may be subjected to damage caused by light exposure. To further reduce illumination, the simulation of an automatic shading system in the form of horizontal louvers was performed. The system was activated when certain illumination values were detected by the sensor on the building’s roof.