This paper experimentally examines the performance of solar air heater (SAH) having a newly designed tubular absorber  comprising adjacent parallel tubes called tubular SAH (T SAH) via energy, exergy, and enviroeconomic  standpoints. A comparative performance assessment between T SAH and flat plate solar air heater  (F SAH) at diverse air mass flow rates (MFRs) of 0.075, 0.05, and 0.025 kg/s is performed. Experiments
 for both heaters are tested using two flow pass arrangements of single-pass (SP) and double pass (DP). The  results reveal that maximum enhancement in thermal and exergy efficiencies of 133 % and 330  %, respectively is obtained when using SP T SAH against SP F SAH at air MFR of 0.025 kg/s. It is found that when  there is  an increase in air MFR, there is a significant increment in thermal efficiency, whereas there  is a reduction in exergy efficiency. Despite the performance in the case of T SAH is more effective
than F SAH, the enhancement in the case of DP F SAH due to using DP flow configuration is greater than that  of DP T SAH. Finally, the results indicate that the carbon credit earned regarding the amount CO2 mitigated  for SP F SAH and SP T SAH at MFR of 0.075 kg/s is estimated at 391.6 $/year and 561.9 $/year, respectively.

The performance of solar air heater of having a new design tubular absorber of adjacent parallel tubes called tubular is investigated experimentally via energy, exergy, energy payback time, exergoeconomic, and enviroeconomic approaches. Moreover, the impact of utilizing porous material on the tubular heat performance is analyzed and compared to flat plate air heater at air mass flow rates; 0.075, 0.05, and 0.025 kg/s for single and
double passes. Results indicate that the tubular heater has higher net energy gain, output air temperature, energy and exergy efficiencies, and smaller energy loss compared to the flat heater. Using porous material and double pass increases the output air temperature of tubular air heater by 3.4 ◦C and flat one by 17.7  C at 0.025 kg/s. Moreover, utilizing porous material with the tubular heater at 0.075 kg/s enhances the energy efficiency by 3.5% and 8.9% and exergy efficiency by 8.2% and 0.9% for single and double pass, respectively. Air pumping power of the tubular heater is greater than flat but its value is very small to influence the tubular net useful energy. Finally, the tubular air heater is more effective compared to flat based on energy payback time, energy cost, exergoeconomic,
and enviroeconomic parameters.
  

An assessment of hybrid solar desalination system consists of solar panel integrated with single slope solar distiller improved by salty water preheating and porous material via productivity, energy, exergy, exergoeconomic and exergoenvironmental is performed under metrological conditions of Alexandria, Egypt. Water preheating is performed by passing it over the solar panel front surface before it enters the still basin, which is also used as solar panel cooler. The panel integration is performed by installing it directly over the still back wall. Solar panel power is used to heat up further the salty water. Moreover,
the impact of utilizing black steel wool fibers in the still basin on the system performance is studied. Results illustrate that preheating 40%, 50%, and 60% of the salty water rises solar desalination system freshwater yield by 10.4%, 15.5%, and 20.9%, energy efficiency by 8.2%, 13% and 20% and exergy efficiency by 26.86%, 33.51%, and 60.64%, respectively. Using black steel wool fibers increases conventional solar still and solar desalination system production without and with 60% preheating by 17.8%, 13.7%, and
11.8%, energy efficiency by 13.58%, 9.73%, and 13.5% and exergy efficiency by 16.51%, 10.27%, and 32.45%, respectively. Solar desalination system with black steel wool fibers and 60% of water preheating achieves the highest performance based on freshwater yield, cost, energy payback time, exergoeconomic, exergoenvironmental and exergoenviroeconomic parameters. With these positive results and the available
solar energy in Egypt, the current system can be a promising nation strategy in saline water desalination and power production.

In this study, the performance of solar still incorporated with thermal energy storage (TES) unit of phase change material (PCM) is evaluated based on energy and exergy methodologies. Energy payback time for solar still with and without PCM is quantified and compared. Furthermore, the performance of both configurations is also evaluated from exergoeconomic and exergoenvironmental points of view. Experiments for solar still with and without PCM are conducted in summer and winter seasons subjected to the weather conditions of Alexandria, Egypt. The findings showed that the addition of a PCM storage unit to solar still system increased the annual energy and exergy savings by 10% and 3%, respectively. The results indicated that the incorporation of PCM in solar still was found ineffective compared to traditional still based on energy payback time. Based on the exergy approach, the integration of PCM in the solar still system is not effective where the conventional still (without PCM) achieved more than 400% more CO2 mitigations compared to PCM-based solar still system. Also, the exergoeconomic and exergoenvironmental parameters of the modified system were very poor related to those of traditional still. Therefore, for PCM-based solar stills systems to become competitive from global energy and environmental approaches, attempts should be performed by industrialists and engineers to find storage materials with low embodied energy and with low cost in conjunction with its evaluation from energy and exergy outputs to get a complete picture about the effectiveness of the system. In this case, the potential
of thermal energy storage techniques for low-temperature solar-powered desalination systems will be thermodynamically, economically, and environmentally effective.

An experimental study is presented on the energy and exergy assessment of integrating reflectors with an evacuated tube solar collector-heat pipe (ETSC-HP) system on its thermal energy storage. The impact of using upper, lower, and upper and lower (two) reflectors on the thermal energy storage, input energy, and energy losses, reflectors’ effectiveness, and energy and exergy efficiencies is assessed. A complete thermal model that evaluates the thermal performance of the collector-heat pipe system and selects the reflectors title angles is presented. The findings show that using reflectors with ETSC-HP rises its input energy, storage energy, energy and exergy efficiencies, and reflected and radiation losses but it reduces the convection losses. Using upper, lower and the two reflectors raises the input energy to the collector by about 15.3%, 22.5%, and 37%, respectively, and the output daily storage energy by 14%, 22.1%, and 35.7%, respectively compared with the system without reflectors. The daily thermal efficiency of the ETSC-HP system with upper, lower and the two reflectors is 63.8%, 71.67% and 76.25% compared with 60.57% of the collector without reflectors. Using reflectors with the ETSC-
HP raises the system thermal performance curve efficiency by about 16% relative to the collector without reflectors. Moreover, using two reflectors increases the average daily exergy efficiency by about 25.3%. Using reflectors with ETSC-HP proves its ability to raise the energy storage from the collector system compared to previous works. 

In this study, an assessment based on energy, exergy, economic, and environmental approaches on a double-pass (DP) solar air heater (SAH) having pin finned absorber at different air mass ratios up and down the absorber is investigated experimentally.
Four air mass ratios are considered: (i) all the air mass flow passes up the absorber and returns to pass down the absorber (DP), (ii) 2/3 of the airflow passes up the absorber and returns to mix with the remainder of air to pass down the absorber (2/3 DP), (iii) the
same as (ii) but 1/3 of the air passes up the absorber (1/3 DP), and (iv) all the air mass passes only down the absorber (single pass, SP). For all mass ratios, the performance of pin finned SAH (P_SAH) is compared with that of flat SAH (F_SAH). The results
indicated that the air temperature rise and energy and exergy efficiencies of P_SAH are highly greater than those of F_SAH. The highest average thermal efficiency of F_SAH is 56.7% obtained at DP flow condition, whereas the highest value of P_SAH is 65.21% obtained at 2/3 DP with an increase of 17.6% compared with F_SAH. Also, P_SAH has higher average exergy efficiency of about 34.7% compared to F_SAH. Furthermore, P_SAH achieves energy payback time (EPBT) lower than that of F_SAH, while P_SAH has higher embodied energy. The findings indicated that F_SAH at SP airflow pattern
has the maximum energy cost (0.0427 $/kWh), whereas P_SAH at 2/3 DP airflow pattern achieves the minimum energy cost (0.037 $/kWh). Finally, the proposed P_SAH system appears to be more viable from exergoeconomic and enviroeconomic approaches compared to F_SAH.

This paper introduces an experimental study for concentrating solar cell performance cooled by using flat heat pipe. The cell represents the heat pipe evaporator and the heat pipe condenser is cooled by using a rectangular finned heat sink. This study is investigated at various heat pipe condenser and adiabatic regions lengths and concentration ratios of the radiation intensity incident on the cell, and for forced and free convection airflow cooling through the finned heat sink. The required radiation energy supplied to the cell is provided by solar simulator. The findings illustrate that cell efficiency and output power increase with increasing the heat pipe condenser and decrease its adiabatic regions’ lengths. However, cell efficiency reduces with rising the incident radiation intensity. The heat pipe temperature increases with radiation intensity, but its maximum temperature difference does not change greatly with variation solar intensity. Cooling the cell by heat pipe increases its output power by 24.3% compared to free convection without utilizing heat pipe at incident energy 500 W/m². Using forced convection with double condenser length increases the cell output power by about 9.1% compared to one heat sink for free convection at falling radiation intensity 3000 W.m^-2. 

Renewable energy applications play a major role in covering the energy demand for building cooling and ventilation. In this paper, an experimental investigation is performed on cooling and ventilation of a building room locating in New Borge Alarb city, Alexandria, Egypt by new combination of solar chimney and geothermal air tube heat exchanger system. PV panel is installed by new technique at the chimney back to produce power
and its performance is compared to an identical PV outside the room. The study is performed for the chimney and PVs facing south of an angle with the horizontal 30° and 45° and for natural and forced airflow inside the geothermal tube. The geothermal tube and chimney ventilation systems are compared with the natural ventilation system of the solar chimney and window. The results indicate that the proposed systems prove their ability to cool the room temperature up to 3.5 °C and change daily its air 42 times. Minimum ventilated air occurs at natural geothermal tube-chimney system of angle 30°. The ratio of the total daily ventilated air by natural geothermal tube-chimney to that by chimney-window is about 56.3% and 65% at 30° and 45°, respectively and for heat released is 55.6% and 64%, respectively. Maximum daily heat released from the room is achieved at chimney inclination angle 45° for natural geothermal tube-chimney-PV system. Maximum PV output power inside the chimney represents 70% of the maximum PV output power outside the chimney which is 120 W/m at chimney inclination angle 30°.

In this study, the performance of single slope solar still combined with enhanced condenser and integrated

with
 parabolic trough solar collector (PTC), is assessed based on productivity, energy, exergy,
exergoeconomic,  and enviroeconomic methodologies. Experiments are conducted using various saline water media  inside a  basin exposed to the hot weather conditions of Sohag city in Upper Egypt. Several solar  still configurations are tested: conventional solar still (CSS), modified solar still (MSS) using aluminum heat sink  as enhanced condenser (HSC), modified solar still incorporated with PTC (MSS + PTC), modified  solar still comprising sand as a porous media inside the basin (MSS + SD), and modified solar
still comprising  sand inside  the basin and incorporated with PTC (MSS + SD + PTC). The experimental findings  revealed that the MSS + SD + PTC achieved the highest freshwater productivity of 4.65 L/m in winter and  9.75 L/m2 in summer, leading to an improvement of around 113 % in winter and 146 % in summer  compared with the CSS system. The highest increase in energy and exergy output per year is obtained
 in the case of MSS + SD + PTC at 139 % and 245 %, respectively. Incorporation of PTC into the MSS  system for all studied water media is found promising in terms of energy payback time, cost, and freshwater yield  compared with MSS without PTC. The exergoeconomic and environmental parameters of  the active systems are found more effective compared with those of the passive systems.

Three-dimensional study of convection-radiation heat transfer of a discrete heat source (chip) inside an enclosure cooled by rectangular finned heat sink is studied. Conduction heat transfer through the enclosure walls and radiation exchange between these walls are considered. Convection heat transfer on the outer surfaces of the enclosure to the ambient is considered. A complete three-dimensional mathematical model of the physical system is presented and solved numerically by using finite difference method and programmed inside MATLAB software and validated by using an experimental work. Results show good agreement between the numerical and experimental results in case of considering radiation. The impact of the enclosure aspect ratio and chip power on
its cooling and heat transfer and fluid flow inside the enclosure is investigated. The results indicate that in an enclosed electronic device, the impact of the radiation is important in the thermal analysis when the natural convection cooling is presented. At chip heat flux of 5 kW/m2 , neglecting radiation impact rises chip temperature by about 20%. The minimum chip temperature is obtained at an aspect ratio of 1.25. Increasing the chip heat flux
and aspect ratio reduces the airflow eddies inside the enclosure. At chip heat flux of 1.25 and 5 kW/m , radiation Nusselt number represents about 17.8 and 19.7% of the total Nusselt number, respectively.