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The use of solar energy to heat water is the more critical application of solar energy. Researchers are trying to develop different methods to improve the efficiency of solar water heaters to meet the increasing demand for hot water due to global population growth. To reduce the cost and increase the efficiency of solar heaters, the solar collector and the storage tank are combined into one part, and this system is called solar storage collector. It can be defined as geometric shapes filled with water, painted black, and placed under the influence of sunlight to gain the largest amount of solar energy. This article presents the various designs of solar storage collector. This review showed that design variables and design shape significantly affect the efficiency of the solar heating system. Climate and operational factors also have a strong influence on the performance of solar heating. Furthermore, scientists and researchers have also used nanotechnology, solar cells, and mirrors to improve other stored solar collectors' performance. Finally, recently published articles indicate an increase in interest in improving the efficiency of solar storage collector by creating new designs that enhance the economic and practical viability.

Hybrid solar collector (PV/T) is designed to produce electricity, hot water, or hot air at the same time as they operate solar cells and solar heaters in one system. This system is designed to increase the electrical efficiency of solar cells by absorbing heat from these cells. The fuzzy logic (FL) is a tool usually used to optimize the operation of the systems. In this paper, the FL is to monitor and correct the mainsystem parameters to remain optimization efficiency at a better level. Three affected variables were studied: Effect of reflective mirrors, the effect of the glass cover, and the effect of the lower reflector angle on the performance of the PV / T hybrid solar system. These three parameters are traveled to be inputs for the FL, and the PV temperature in addition to system efficiency is the output for it. The effect of solar radiation was found to have a great effect on the efficiency of the hybrid solar collector. The thermal efficiency was 82% for the given value of the PV and mirrors, while the efficiency down to 50 for another angle. By using the artificial intelligent the system behavior depends on its output, which called feedback close loop control, at a real-time process that optimizes the system efficiency and its output.

ABSTRACTIn this article, an idea has been presented that utilizes the heat produced from the petroleum gas burning accompanying the process of oil extraction to enhance the solar chimney performance. The simulation software tool ANSYS Fluent 2020R1 was used to know the possibility of exploiting this waste energy of gas and combining it with a solar chimney. Seven gas channel configurations were tested on the solar chimney to determine which can produce the most electricity. The simulation results showed that this idea could be exploited to produce higher electric energy, and the efficiency of the solar chimney was increased so that the electric energy production process continues for 24 hours instead of production during the sunshine period only. Different designs were considered for the channels inside the solar collector. Case1 and Case2 were meant for validation purposes only. Good agreement was achieved with the previous research with a maximum error of 2%. The results showed that the circular design of the two-ring burner was the best choice which gave the optimum electric power from the system of about 121.1 kW. It was noted that the circular design of the two-ring burner achieved the highest thermal efficiency, which amounted to 0.523%.

One of the disadvantages of solar systems is their low efficiency due to weather conditions such as dust and clouds that reduce their performance. Therefore, this article examines the impact of cloudy weather on the performance of the PV/solar chimney to demonstrate the performance of these solar systems under overcast weather conditions. The PV/solar chimney system was designed and built, and two days in December were chosen for testing: 27 December with clear weather without clouds and 28 December with cloudy weather.The results showed that cloudy weather has a clear effect on the performance of the PV/solar chimney where the intensity of solar radiation is low. Clouds act as a barrier preventing access to sunlight, as the electrical power generated on a clear weather day reached 341.92 W, while on a cloudy weather day, 187.88 Watts at noon. The kinetic energy on a clear weather day reached 17.212 mW, while on a cloudy weather day, it reached 9.47 mW at noon. The electrical efficiency on a clear weather day reached 15.96 %. In contrast, on a cloudy weather day, it reached 13.2 % when the test started at 9 a.m., after which the efficiency decreased with the increase in the intensity of solar radiation to become 13.574 % in clear weather while 12.12 % in cloudy weather at noon, and the thermal efficiency on a clear weather day reached 56.06 %. In contrast, on a cloudy weather day, 42 % at noon. The total efficiency in clear weather reached 69.65 %, while on a clear weather day cloudy by 54.12 % at noon.

This study introduces and evaluates a novel design of an integrated solar collector, termed the Rhombus storage solar collector. This novel design consists of a cube whose upper side is split in two directions at 45° as an inclined angle to form the absorber surface of 0.52 m2 absorbent area and a total storage volume of 210 L. The major reasons for using this type of collector are their high efficiency and their ability to replace the traditional tanks used in Iraqi houses and developing countries. This innovative design has low costs and high efficiency because it reduces losses by removing connecting pipes. In addition, it is easy to manufacture and is made up of materials that are widely available on the market. This study is based on the maximum useful efficiency curve (MUE), and due to its large thermal mass, it cannot achieve steady-state conditions. This system is evaluated experimentally under various load conditions. The first case is the no-load condition, the second case is the intermittent condition where 50 L of hot water is withdrawn at 2 p.m., and the third case is the continuous load condition of 0.5 L/min. The system demonstrated excellent performance, particularly in low ambient temperatures. The system also showed promising efficiency levels across different load conditions.

The world is currently suffering from the careless usage of fossil fuels, which is primarily responsible for global warming and pollution. As a result, researchers have looked into alternate techniques to alleviate this issue and limit the dependence on fossil fuels. Renewable energy, particularly solar energy, offers a promising and sustainable future for energy markets. Over time, researchers have discovered various novel techniques to harness solar energy, including solar water heaters (SWHs), which are made up of absorber surfaces, pipelines, storage, and other mechanical components such as pumps. Recently, there has been a significant increase in interest in SWH as a means to save expenses and enhance thermal efficiency by canceling the connecting pipes. Pipe cancellation was the result of merging the absorber and storage into a single unit. This cancellation led to the creation of a new type of solar collector called integrated collector storage (ICS). These collectors are geometric shapes filled with water and painted black to optimize solar radiation absorption. This article examines the approaches for improving storage solar collectors, specifically integrated solar water heaters (ISWHs). The study focuses on structural design improvements, PV cells, evacuated pipelines, and phase change materials (PCMs). Furthermore, the study examines the performance of ICSSWH. These improvements demonstrated that the integrated solar heater provides good and promising efficiency at a reasonable cost, in addition to meeting the desired goal of lowering polluting emissions.

The performance of solar panels is significantly affected by high temperatures, leading to various cooling methods being employed to enhance their efficiency. This study utilizes comprehensive computational fluid dynamics (CFD) simulations with Ansys Fluent 2023 R1 software to evaluate the effectiveness of cooling photovoltaic (PV) panels using ground source energy in Kirkuk city, northern Iraq (35° 28′ N - E. 44.39). A 3-D model was employed to analyze the thermal behavior of the PV panel over 10 h (8:00 a.m. to 5:00 p.m.). The simulation demonstrates that the proposed cooling method achieved an impressive temperature reduction of approximately 28 % compared to conventional cooling methods. Moreover, the PV panel with ground-source cooling consistently outperformed the PV-only setup, showing a noteworthy improvement of approximately 6.5 % in power output, reaching a maximum of around 88 W. Examination of velocity and temperature distribution contours revealed that ambient air drawn in as hot air gradually dissipated its heat to the surrounding soil and bricks as it traversed through underground pipes, resulting in a significant reduction in temperature. This cooling process effectively enhanced the overall performance of the PV panel.

The provision of electricity and hot water is among the most significant human requirements at present. A photovoltaic/Trombe wall (PV/TW) system concurrently provides warm water, hot air, and electrical power for domestic usage. To optimize the amount of incident solar radiation, reflective mirrors were put on each side of the front face of the PV/TW system. The current article aims to determine the optimal angle for these mirrors that improve the thermal and electrical efficiency of the system.The findings indicated the utilization of DC fans, reflecting mirrors and water flowing across a heat exchanger improves thermal and electrical performance. The best angle for the impact of reflective mirrors to enhance electrical efficiency is the angle (30°) when using water cooling, which led to a decrease in the temperature of the photovoltaic panel and thus raised the electrical efficiency to reach (13.86 %). Also, the results confirmed that the system’s thermal efficiency that uses two cooling fluids is the highest relative to the other cases, and the system’s thermal efficiency that contains mirrors at 30° was higher than the other two angles. Finally, the addition of reflective mirrors is a favorable option for obtaining higher energy compared to the system without mirrors.

Renewable energy, especially solar energy, is one of the more essential sources that provide part of the world's energy needs. Therefore, combining photovoltaic panels and a Trombe wall is one of the more comprehensive research topics. This system is called PVTWS.In this study, the performance of the PVTWS was investigated under Iraqi weather conditions by building an experimental model and studying the effect of cooling methods, reflective mirrors and phase change material. The finding demonstrated showed that the utilization of DC fans and a heat exchanger to cool the solar panel led to a decrease in its temperature and a reduction in energy loss, which increases the efficiency and wattage of the panel. In addition, the use of the phase change material helped cool the solar panel as a result of absorbing heat. It also works to improve the heating of the building during the afternoon, as it works to release heat into the space in which it is located. The use of reflective mirrors helped to increase solar radiation, which led to an increase in electrical energy. The highest electrical and thermal efficiency was recorded when using these different configurations together (10.42% and 78.59%), respectively.

In recent years, researchers have been interested in renewable energy as an alternative to non-renewable energy and its importance, especially solar energy. Solar chimney power plants are one of the proposed systems for energy production based on the sun. One of the most important disadvantages of the solar chimney power plant is the low efficiency of these systems. And previous research indicated the need for many studies to increase their performance. This study focused on reviewing the articles examining the performance of the main components of solar chimney power plants and the most important approaches to improve the performance of the system using various methods, including integrating the system with thermal storage materials and phase changes materials (PCMs) as well as integrating it with other technologies and in addition, integrating the solar chimney power plant with an external heat source and the engineering treatments for tower chimney design to improve the efficiency of the solar chimney power plant.

Renewable energy sources, especially solar energy, can meet part of the global energy needs, especially for domestic uses at present. The combination of Trombe walls and solar cells is currently one of the most extensive research topics and this system is named a Photovoltaic/Trombe wall (PV/TW). A PV/Trombe wall system can simultaneously generate electricity, heat water, and heat homes. The current article discusses studies that have been conducted on this system in several countries over the past few decades. The current review covers the effect of operational parameters including a DC fan that can assist in cooling the solar cells and raising the interior temperature, air gap thickness, and thermal insulation effect. The use of double glazing reduces the temperature of photovoltaic cells and enhances the efficiency of the system. The efficiency of the PV/TW can be improved using porous media, binary fluids, nano-fluids, and phase change materials.

The current article examined the effect of adding nano silica and polystyrene granules on the compressive strength and thermal conductivity of concrete. Nano silica and polystyrene granules were added in proportions (1%, 2%, 3%) to the concrete mixture, and the compressive strength and thermal conductivity of the concrete mixtures were examined. The results showed when silica nanoparticles were added, the compressive strength increased, however when polystyrene granules were added, the compressive strength decreased. The thermal conductivity of concrete by adding nano silica and polystyrene granules ranged within (0.43–0.45) W/m. oC. The best percentage of silica nanoparticles (SiO2) and polystyrene granules can be added to concrete to obtain the maximum compressive strength values, which amounted to (3%) and (0.8%), respectively.

A numerical study is achieved on a new shape of temperature saver solar collector using an artificial neural network. The storage collector is a triangle face and a right triangle pyramid for the volumetric shape. It is obtained by cutting a cube from one upper corner at 45°, down to the opposite hypotenuse of the base of the cube. The numerical study was carried out using the computational fluid dynamics code (ANSYS-Fluent) software with natural convection phenomenon in the pyramid enclosure. Elman backpropagation network is used for his ability to find the nearest solution with the smallest error rate. The network consists of three layers, each of different corresponding weights. The results show that the temperature and velocity distributions throughout the operating period were obtained. The influence of introducing an internal partition inside the triangular storage collector was investigated. Also the optimum geometry and location for this partition were obtained. The enhancement was best at y = 0.25 m, whereas the height of triangular collector was 0.5 m. The hourly system performance was evaluated for all test conditions. The performance of the NN to train a model for this work was 0.000207, while the error of the calculation was 1×10-2 as average.

Hydroplaning is one the most dangerous phenomena which effect on the safety of driving cars on wet roads, then, the critical speed of slipping cars is an important parameter in the hydroplaning ,and depends on the properties of the following three parameters: tires, water layer and road surface. The road texture is the main property of road specifications which affect directly on the critical speed of the vehicle. In the present work, the properties of road roughness and influence of surface texture on critical speed of vehicle are studied with variation of the following parameters: thickness and dynamic viscosity of water on the road surface and the vehicle load. The results showed that increasing the road surface roughness and the vehicle load both has a appositive influence on the critical speed (increase)of the vehicle, while increasing the dynamic viscosity and thickness of the water layer on the road surface has a negative influence on the critical speed (decrease) of the vehicle. DOI: http://dx.doi.org/10.25130/tjes.24.2017.24

The last stage endured on obvious erosion especially the front and the end of the blade. The erosion caused the appearance some cracks in this place. These remarks coincided with the theoretic al results, which were acquired according to the condition of the turbine of station which showed that the droplet, which collided with the blade ends, caused high pressure on the surface of the blade and caused the occurrence of the corrosion. The danger of the erosion unavoidable due to its relationship with tae station efficiency and the only to avoid that is the use of the blade made of erosion resistance ingots.

This article introduces a new design of solar storage collectors integrated with a PV panel for domestic applications. Two identical practical models were built to test the performance of the collectors by analyzing and comparing them with the classical storage solar collector. In the first model, the solar cells were mounted on the tank’s front inclined surface to act as a black absorber surface, while in the second model, the absorbent plate was metallic and dyed in a pale black color.A number of experiments have been conducted on both models to validate and assess their performance. For the no-load conditions, the maximum storage temperature was about 77 °C and 81 °C for the new and conventional models respectively. For the load conditions, the mean storage temperature recorded the maximum value of 77 °C and 74 °C for the new model and conventional models respectively. Electrical efficiency increased as a result of removing warm water from the model. The highest electrical efficiency recorded for the new system was 15% at 9 a.m., with a water flow rate of 0.085 liters/min. On the other hand, the thermal efficiency of the new system is lower than the traditional system. The highest thermal efficiency recorded for the new system was 69% at 10 a.m., with a water flow rate of 0.085 liters/min. At the same time, the highest thermal efficiency for the conventional system was 88% at 11 a.m., with a water flow rate of 0.085 liters/min. It was also found that increasing the mass flow of the fluid drawn from the collector increases the thermal efficiency of the old and new designs.

The Photovoltaic/Trombe wall system (PV/TW) is a design that generates electricity and provides hot air and warm water for domestic uses simultaneously; this system aims to optimize the electrical efficiency of the PV panel by removing the heat from them. The current article includes a study of the impact of utilizing reflective mirrors on the performance of PV/Trombe wall. Reflective mirrors were used to increase the quantity of solar energy reflected on the solar cells. Fans were also utilized to lower the heat of the PV panel and optimization comfort conditions.The results showed that using reflecting mirrors and DC fans led to the optimization of electrical and thermic efficiency. The maximum thermal efficiency value recorded was 74.4% when using reflective mirrors only without fans. In contrast, the highest electrical efficiency in the case of using DC fans without reflective mirrors was 13.9% at noon. These results are in convention with those of prior studies.

The current article studies the effect of dusty weather conditions on the performance of PV/Trombe wall Photovoltaic. Two experimental models were built to study the impact of climatic changes and operating conditions on the PV/Trombe wall, one with DC fans and the other without DC fans. The operating conditions for dusty and non-dusty days were tested to show their impact on system efficiency. In the case of the model using DC fans on a clear day, the electrical and thermic efficiency of the model reached 10.2% and 17.6%, respectively. While in the case of the model without DC fans and on a clear day, the electrical and thermic efficiency of the model reached 8.4% and 40.1%, respectively. In the case of the model using DC fans on a dusty day, the electrical and thermic efficiency of the model reached 6.6% and 11.9%, respectively. While in the case of the model without DC fans and on a dusty day, the electrical and thermic efficiency of the model reached 3.5% and 34.1%, respectively. Dusty weather conditions reduce the electrical efficiency of the PV/TW system; the average daily electrical efficiency increase was 2.4% under clear weather conditions compared to dusty weather conditions. Also, the dusty weather conditions lead to an apparent decrease in the temperatures of the solar panel and air in the room. The decrease was 12% compared to a clear day.

This article aims to propose and study a new system design for renewable energy called photovoltaic/ solar pond. This new system involves cooling the arrays of the photovoltaic/thermal collectors, which are installed beside the salinity gradient solar pond with a heat exchanger that is installed behind each solar cell. Thermal energy gained by the photovoltaic/thermal collectors was stored in the heat storage zone using a heat exchanger system. An experimental assessment was performed to examine the thermal performance of the mini PV/solar pond. The experiments were carried out for five months, starting from September 2019 and ending in January 2020, in Kirkuk, Iraq. During this period, temperature, salinity, and power generation were recorded in real-time. The experimental results confirmed that the maximum total efficiency value of the system was 37.67% which was recorded in September. Besides, the highest value of the daily thermal efficiency was 30% for September, while the ultimate value of the daily electrical efficiency was 9.357% as recorded in December. The current result agrees well with other experimental studies in the same field.