In this paper, an experimental investigation is performed on the impact of condensation rate of solar still condenser at different thermal energy storage materials on the performance of single slope passive solar still. The condensation rate is changed by installing different designs of the still condenser: (i) glass plate condenser, GC, (ii) corrugated aluminum sheet heat sink condenser, CHS, (iii) aluminum heat sink condenser having vertical rectangular fins at its outer surfaces RHS, (iv) aluminum heat sink condenser having pin fins at its outer surface, PHS, (v) aluminum heat sink condenser having pin fins at its outer and inner surfaces, DPHS. Two different thermal energy storage materials inside the still basin are used; sand and black wool fibers (BWF) plus pure saline water which yield different evaporation rates of the saline water. The findings show that increasing the heat transfer rate (HTR) by the condenser increases the still yield to a limit and then decreases this yield at higher rates. Moreover, increasing the evaporation rate by using thermal energy storage material reduces the negative impact of high condensation rate. The still yield of GC is the minimum while the still yield in case of PHS has the maximum production. Solar still with PHS condenser achieves maximum yield increments of 54%, 63%, 76% in case of saline water only, sand, and BWF medium in the basin, respectively compared to the case of GC condenser with saline water only (conventional still) in the basin. The conventional still has the minimum efficiency of 23.3% and the still with PHS condenser and BWF achieves the maximum still efficiencies of 40.7%. Moreover, enhancement of HTR through using of DPHS condenser reduces the still efficiency to 29.2%, 34.3%, and 37.5% in case of pure saline water, sand, and BWF, respectively. Using PHS condenser with BWF in the still basin reduces the freshwater yield cost by about 21% compared to conventional still.

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.

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.

An assessment of a flat plate double pass (DP) solar air heater (SAH) having V-corrugated absorber (C_SAH) and corrugated-perforated absorber (CP_SAH) via energy, exergy, economic and environmental approaches (4E) is presented experimentally. The study is performed at four different levels of air mass flow ratios inside the flat plate solar air heater with two levels of absorber plates i.e. C_SAH and CP_SAH. C_SAH and CP_SAH performance is compared with flat SAH (F_SAH) performance. The results show that F_SAH achieves the lowest daily energy efficiency values of 52.5%, 55.86%, 54.77%, and 56.7% while CP_SAH achieves the highest of 67.67%, 69.7%,71.85%, and 70.8% at SP, 1/3 DP, 2/3 DP, and DP conditions, respectively. Moreover, C_SAH and the CP_SAH achieve maximum daily efficiency of 70.58% and 71.85% at 2/3 DP condition. CP_SAH achieves average daily exergy efficiency of 0.78%, 0.89%, 0.97%, and 0.92% with percentage increments of 47%, 55%, 76%, and 54% compared to F_SAH at same previous conditions, respectively. F_SAH at SP condition achieves the maximum energy cost of 0.0427 $/kWh while CP_SAH at 2/3 DP condition achieves the minimum energy cost of 0.0324 $/kWh. The proposed CP_SAH at 2/3 DP condition is the most suitable from the studied cases.

An assessment of using different passive condenser designs of the solar distiller based on productivity, exergy, energy, energyeconomic, exergyeconomic, enviroeconomic is investigated experimentally. Five different condenser designs are considered; (i) glass plate condenser, GC (CSS), (ii) corrugated aluminum sheet heat sink condenser, CHS, (iii) aluminum heat sink condenser having vertical rectangular fins at its outer surfaces, RHS, (iv) aluminum heat sink condenser having pin fins at its outer surface, PHS, and (v) aluminum heat sink condenser having pin fins at its outer and inner surfaces, DPHS. The findings show that augmenting the rate of condensation by varying the condenser design increases the still yield to a limit and then decreases this yield at a higher condensation rate. CSS has the smallest freshwater yield and still with PHS has the maximum production with an increment of 54 % comparing with GC condenser. The maximum increase of the daily average energy and exergy efficiencies of the still is about 55.3 % and 73.1 %, respectively in case of PHS condenser compared with CSS. Still with DPHS condenser has the maximum production cost while the still with PHS or CHS condenser has the minimum. Distiller with PHS condenser is the best system in achieving CO₂ reduction benefits of 1.82 tons CO₂/year.

An experimental study on the performance of double pass Solar Air Heater (SAH) having a new designed absorber is performed. The new SAH absorber is constructed from conductive aluminum tubes adjacent to each other and installed in the same direction of the air flowing inside the SAH. The new SAH performance (called Tubular Solar Air Heater (TSAH)) is studied at various mass flow rates of air inside the SAH. Moreover, it is compared with the performance of Flat plate Solar Air Heater (FSAH) having the same dimensions and materials of the TSAH except the absorber design. Findings indicate that the TSAH has higher outlet air temperature, efficiency and net energy gain and lower top heat loss compared to FSAH. TSAH achieves maximum air temperature rise more than 6 °C compared to FSAH at 0.025 kg/s. TSAH efficiency is greater than FSAH efficiency by about 19.4%, 21%, and 40.3%, at inlet air flow rate of 0.075 kg/s, 0.05 kg/s and 0.025 kg/s, respectively. The outlet air temperature and top thermal energy loss of the TSAH decrease with increasing the air mass flow rate, while its efficiency, energy output, and pressure drop increase. Moreover, TSAH efficiency in case of double air pass is greater than single air pass. Despite the TSAH pressure drop is greater than FSAH pressure drop, but its value is very small to impact the TSAH net thermal energy gain. The designed TSAH performance is found greater than the performance of FSAH and previous designs of published SAHs.

In this work, experimental work is presented on the performance of a hybrid solar distiller comprising solar still (SS) combined with parabolic trough solar collector (PTSC) using direct heating of salty water by the collector. In this technique, the salty water supplied to the SS is heated by passing it directly through the parabolic receiver without using heat transfer mediums that reduce the system efficiency. The study is carried out at different salty water depths inside the SS basin under hot climate conditions of Upper Egypt. The system performance is compared with a previous system using oil as a heat transfer medium between PTSC and still (indirect heating). The advantages of this technique are its ability to reduce initial salty water depth in the basin and avoid using the pumping system and heat exchanger compared to the direct heating. The performance of the proposed system is evaluated based on productivity, energy payback time (EPBT), exergy, enviroeconomic, and exergoeconomic methodologies. Findings illustrate that the present system rises the energy efficiency by about 12%, 27.5%, and 46% and the system exergy efficiency by about 14%, 30%, and 49% at salty water depth 15 mm, 10 mm, and 5 mm in the basin compared with the indirect heating system. Moreover, using this technique of salty water heating reduces the production cost of freshwater by about 71% compared with the direct heating system. The exergoeconomic and enviroeconomic parameters of the direct heating mechanism are more effective compared with those of the indirect heating mechanism.

This work proposes an innovative statistical model by utilizing the response surface methodology (RSM) method to analyze a batch solar behaviour still. This investigation’s main goal is to study the impact of the input factors (solar radiation, ambient temperature, water depth, and thickness of insulation) most influencing water productivity. The polynomial regression model derived from a numerical balance energy model to predict the solar’s productivity still is established. The quadratic model is checked by a coefficient of determination (R2). An excellent fitting is attained between the forecasted results derived from the statistical model and the numerical simulation derived from the heat balance model. The results reveal that the importance of the influence in the order of impact on the amount of distilled water is water depth, solar radiation, ambient
temperature, and thickness of insulation. A simple polynomial statistical model is stated in this investigation to determine and maximize the amount of distilled water from solar still based on the four considered input factors. 

In this paper, an experimental investigation is performed on the impact of condensation rate of solar still condenser at different thermal energy storage materials on the performance of single slope passive solar still. The condensation rate is changed by installing different designs of the still condenser: (i) glass plate condenser, GC, (ii) corrugated aluminum sheet heat sink condenser, CHS, (iii) aluminum heat sink condenser having vertical rectangular fins at its outer surfaces RHS, (iv) aluminum heat sink condenser having pin fins at its outer surface, PHS, (v) aluminum heat sink condenser having pin fins at its outer and inner surfaces, DPHS. Two different thermal energy storage materials inside the still basin are used; sand and black wool fibers (BWF) plus pure saline water which yield different evaporation rates of the saline water. The findings show that increasing the heat transfer rate (HTR) by the condenser increases the still yield to a limit and then decreases this yield at higher rates. Moreover, increasing the evaporation rate by using thermal energy storage material reduces the negative
impact of high condensation rate. The still yield of GC is the minimum while the still yield in case of PHS has the maximum production. Solar still with PHS condenser achieves maximum yield increments of 54%, 63%, 76% in case of saline water only, sand, and BWF medium in the basin, respectively compared to the case of GC condenser
with saline water only (conventional still) in the basin. The conventional still has the minimum efficiency of 23.3% and the still with PHS condenser and BWF achieves the maximum still efficiencies of 40.7%. Moreover, enhancement of HTR through using of DPHS condenser reduces the still efficiency to 29.2%, 34.3%, and 37.5%
in case of pure saline water, sand, and BWF, respectively. Using PHS condenser with BWF in the still basin reduces the freshwater yield cost by about 21% compared to
conventional still

The influence of thermal energy storage (TEGS) of coupling new hybrid system of two phase change materials (PCMs) with air conditioning (A/C) unit on its cooling and heating performance in summer and winter, respectively is investigated. PCM RT 10 HC (PCM10HC) of 10-12 C phase change temperature and PCM type SP
24E (PCM24E) of about 24-25 ◦C phase change temperature suitable for working on winter and summer climate conditions, respectively are integrated as a hybrid system and coupled with the condenser/evaporator of the A/C unit. The performance of the A/C unit of this hybrid system is compared with the unit performance using only PCM24E system in summer and PCM10HC system in winter. The study is studied at two configurations of the
hybrid PCMs system. The studied physical systems are modeled by a complete mathematical model that is numerically solved by utilizing ANSYS-Fluent software. The solution numerically is validated by using an experimental setup which shows the high accuracy of the numerical solution. The findings based on the stated design conditions of Egypt demonstrate that the time of complete charging and discharging procedures is nearly the same for hybrid and single PCMs systems. The maximum increase of the A/C unit COP is about 88% for the hybrid system in summer while it is nearly 22% in winter. The percentage increase of the saving power for the single system, the hybrid system is about 6.85%, and 6.5%, respectively in summer and 3.9% and 2.8% in winter,
respectively compared to A/C without PCM units. Increasing the distance between the PCMs’ plates impacts negatively on the exit air temperature from PCMs plates and the saving power. The results demonstrate that the hybrid system has nearly the same merits on the A/C working as the single systems plus it can work during the hot and cold climate conditions.