This study experimentally investigates the performance of solar still coupled with a parabolic trough solar collector (PTSC) at different cooling rates based on energy, exergy, exergoeconomic, and enviroeconomic standpoints. Different solar still systems are considered; conventional solar still (CSS), solar still with heat sink condenser (MSS)
and coupled with PTSC (MSS + PTSC), MSS having an umbrella and coupled with PTSC (MSS + PTSC + U), MSS with PTSC and condenser forced air cooling (MSS + PTSC + FA), and MSS + PTSC with condenser forced water cooling (MSS + PTSC + FW). Experiments are conducted under hot climate conditions of Sohag city, Egypt.
Results indicated that the freshwater yield of all studied systems in ascending order is as follow; CSS + PTSC, MSS + PTSC +U, MSS +PTSC, MSS +PTSC +FA, and MSS + PTSC +FW in summer with value of 7.74, 8.02, 8.68, 9.11, and 9.45 kg/m 2
, respectively. The maximum exergy efficiency of 1.34% in summer is achieved in case
of MSS + PTSC + FW system. The economic analysis shows that distilled water cost is minimum for MSS + PTSC + FW (~0.02 $/L), while it is maximum for MSS + PTSC + U (~0.022 $/L). It can be concluded that high freshwater production and less distilled water cost are making the enhanced solar desalination system feasible and competitive. Minimum exergy efficiency occurs in case of CSS +PTC with a value of 1.197% and MSS
has higher average daily exergy efficiency. MSS + PTSC achieves the best performance-based exergoeconomic approach. MSS + PTSC + FW is by far the best system in cutting down CO2 emissions.

A novel fractional model based on the Riemann Liouville fractional derivative to simulate the thermal performance of conventional solar still and show the effect of using hybrid nanofluid on the desalination system is presented. The results of the fractional model are compared with the results obtained from the classical model, then compared to real experimental data under various climate conditions of Upper Egypt. The theoretical results reveal a perfect agreement between the proposed fractional model and the experimental data of the still with a percentage of error reached 1.486% in summer and 3.243% in winter compared to an error percentage of 24.1 % and 20.08%,  in case of applying the classical. Moreover, the performance of the modified solar still after adding hybrid nanoparticles is also compared with the conventional solar still. The model is implemented using a hybrid nanofluid of alumina and copper oxide (Al₂O₃-CuO) with a concentration of 0.025% for each nanoparticle. The results show that using hybrid nanofluid raises the still daily productivity to 5.5239 kg/m².day in summer and 3.1079 kg/m².day in winter of an enhancement in the still output yield of 27.2% and 21.7% compared with still without nanoparticles. The average energy efficiency of the still in summer is also increased to 49.54% and 23.212% in summer and winter, respectively, with an augmentation of 12.6% and 11.85% in hot and cold climate conditions, respectively. In addition, the average exergy efficiency is raised by 22.5% in summer and 13.4% in winter by using hybrid nano.

This paper presents three-dimensional study on the enhancement of waste heat recovery from vertical chimney via  thermoelectric generators (TEG) by using heat spreader. The physical model composes of aligned  TEGs mounted on the chimney wall where each TEG is cooled at its cold side by rectangular finned  heat  sink. The  spreaders are installed on the generators’ cold sides between the generators and the  heat sinks’ bases. The studied model represents three of the TEGs installed on the chimney wall. Three dimensional model is  presented for the physical model coupling the governing equations of thermal, fluid flow  and electrical models and is solved by using ANSYS software. Results indicate that using spreader increases  total  output  generators  power by 17% and 42% at spreader length 40 and 140 mm, respectively and  pitch 140 mm. The increase of the TEGs power is about 17% and 21% due to using spreader length
of 40  and 80 mm, respectively at 80 mm pitch. Using heat spreader with maximum length of 140 mm, increases  the conversion efficiency of the lower, middle generator and upper TEGs by 22.2%, 18.8%, and 19.7%,  respectively, while the overall efficiency of the system rises by 20.4%. Using spreader with 140 mm reduces  the used generators and heat sinks numbers to approximately the half.

A study is presented on the enhancement of solar still (SS) performance by using chimney exhaust gases (EGs) passing through chimney channels under the still basin. The impact of the exhaust gas temperature on the SS temperature, productivity, efficiency,
and freshwater yield cost is considered. The SS performance with the chimney is compared with that of conventional solar still. The study is performed under the hot and cold climate conditions of Upper Egypt. A complete transient mathematical model of
the physical model including the solar still regions temperatures, yield, and heat transfer between the SS and the EGs is constructed. This model is solved by using Runge-Kutta method of fourth-order and programmed inside MATLAB software and validated using an experimental setup. The results show that the SS saline water temperature and freshwater yield rise with rising EGs temperatures. Furthermore, the impact of using EGs on the SS performance in winter is superior to that in summer, and also during the daytime is higher than that of night. Using chimney EGs at 75 °C and 125 °C enhances the daily freshwater yield of the SS by more than three times and about six times in winter, respectively, and about two and half times and more than three times in summer, respectively. Using EGs at 125 °C achieves a maximum solar still efficiency of 29.5% in winter and 49.5% in summer with an increase of 41% and 55.7%, respectively, and reduces its yield cost by 63.6% compared to conventional SS.

An experimental investigation is executed on the enhancement of hybrid solar desalination system composed of integrated solar panel with solar still by utilizing porous material and saline water preheating. The saline water preheating is performed by passing it over the solar panel front surface before entering the still which is also used
as solar panel cooler. The solar panel integration is performed by installing it directly over the solar still. Solar panel output power transferred directly to the salty water to raise still freshwater production. The enhancement of the desalination system by utilizing black steel wool fibers as porous material in the basin of solar still is studied. The study is performed under the meteorological conditions of Borg Al-Arab city, Alexandria, Egypt. The findings reveal that preheating 40%, 50%, and 60% of the salty water rises the freshwater yield of the solar desalination system (Conventional solar still integrated with solar panel) by 10.4%, 15.5%, and 20.9%, and its energy efficiency by 8.2%, 13% and 20%, respectively. Using black steel wool fibers increases the production of
conventional still, solar desalination system, and solar desalination system with 60% preheating by 17.8%, 13.7%, and 11.8%, and its energy efficiency by 13.58%, 9.73%, and 13.5% respectively compared with solar still without porous material. Solar desalination system with black steel wool fibers at 60% preheating achieves maximum yield and average daily efficiency of 3.534 kg/m2 day and 38.07%, respectively with an increase
51.4% and 38%, respectively in comparison with conventional solar still.

The performance of single slope solar still with an enhanced condenser at different saline water mediums in the basin is studied and assessed based on productivity, energy, exergy, economic, and enviroeconomic methodologies. Six solar still configurations are
considered: conventional solar still (CSS); modified solar still (MSS) which is a still with heat sink condenser; MSS having an umbrella (MSS + U); MSS with forced-air cooling (MSS + FA); MSS with forced-water cooling (MSS + FW); and finally, MSS with forced water cooling and contains sand in the basin (MSS + FW + SD). Experiments are conducted under hot and cold climate conditions of Sohag city, Egypt. The results indicate that the MSS + FW + SD has a maximum daily yield of 5.37 kg/m2 in summer and 2.74 kg/m2 in winter with an increase of 36% in summer and 26% in winter compared with CSS. It was found that the maximum increase of the energy and exergy efficiency compared with CSS is achieved in the case of MSS + FW + SD of 39% and 33%, respectively. Furthermore, the maximum and minimum cost of freshwater is achieved in cases of MSS + U and MSS + FW + SD, respectively. Finally, among all studied systems, MSS + FW + SD achieves the best performance based on the exergoeconomic approach.

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 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.  

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.