Experimental analysis and exergy efficiency of a conventional solar still with Fresnel lens and energy storage material

This study focuses on the experimental investigation and exergy analysis of a modified solar still (MSS) with convex lenses on glass cover to collect the solar radiation at the focus on surface water. A comparative analysis of the performance and yield of the MSS with convex lenses and the conventional single slope SS were carried out for the same climatic condition of Tanta (Egypt). Similarly, the effect of modification in the SS using convex lenses, with or without black stones, on the freshwater yield is experimentally investigated. The results indicated that the lenses focus the solar radiation to the water placed in the basin and increase the water‐glass temperature difference (T _w – T _g). The yield of freshwater from the MSS with the convex lenses is comparatively higher than that of the conventional SS (26.64%). In addition to convex lenses in the inner cover surface, freshwater yield improved by 35.55% by adding blue stones as energy material inside the basin under constant water mass of 30 kg. The maximum exergy efficiency of the SS with lenses and blue stones was 11.7%, while the SS with lenses alone was 4%. The quality of freshwater produced after desalination was well within the World Health Organization standards. The total dissolved solids and pH after desalination were 22 mg/L and 8.08, respectively.     

Experimental and economic analysis of energy storage-based single-slope solar still with hollow-finned absorber basin

The paucity of drinking water is an alarming glitch across the globe. The conversion of available seawater into drinking water by utilizing renewable energy is the best way to surmount this challenge. Desalination through solar still is one of the notable, monetary, and viable processes among various desalination approaches. The current research aims to augment the potable water yield of single-slope solar still by using a hollow-finned absorber basin inserted into paraffin wax—phase change material (PCM). The effect of hollow-finned absorber basin on the yield of solar still is investigated separately, with and without PCM, and compared with the results of conventional solar still (CSS). In the first set of experiments, the CSS and solar still with a hollow-finned absorber basin without PCM (SSHF) are investigated. In the second set of experiments, the CSS and solar still with a hollow-finned absorber basin inserted into PCM (SSHFP) are investigated. The experimental results reported that the CSS is having almost the same yield on the 2 days of testing. The yield of SSHF and SSHFP is increased by 15.7% and 52.4%, respectively, when compared with CSS. The results of the economic analysis proved that the payback period and cost per liter of freshwater produced from SSHFP are comparatively better than SSHF and CSS.     

Performance study of the inverted absorber solar still with water depth and total dissolved solid

In this communication, an experimental study of inverted absorber solar still (IASS) and single slope solar still (SS) at different water depth and total dissolved solid (TDS) is presented. Experiments are conducted for the climatic condition of Muscat, Oman. A thermal model is also developed for the IASS and validated with experimental results. A fair agreement is found for the daytime operation of the IASS. It is observed that higher water temperature can be achieved by using the IASS in comparison to the SS. The daily yield obtained from the IASS are 6.302, 5.576 and 4.299 kg/m²-day at water depths (d_w) 0.01, 0.02 and 0.03 m respectively. At same respective water depths, the daily yield obtained from the SS are 2.152, 1.931, 0.826 kg/m²-day respectively lower than that of the IASS. It is observed that for climatic condition of Muscat, Oman, the optimum water depth for the IASS is 0.03 m above which the addition of reflector under the basin does not affect its performance much more in comparison to that of the SS for sea water. The feed saline water and yielded distilled water are also compared for different TDS values, pH, and electrical conductance. On the basis of economic analysis of IASS, it is found that the annualized cost of distilled water in Indian rupees for Muscat climatic condition is Rs. 0.74, 0.66 and 0.62 (conversion factors: $ 1 = Rs. 50 and 1 OMR = Rs. 120) for the life time of 15, 20 and 25 years respectively.     

Experimental investigation on the effect of MgO and TiO2 nanoparticles in stepped solar still

This work aims at augmenting the amount of potable water using MgO and TiO₂ in stepped solar still. Experiments were carried out for the climatic conditions of Chennai, India, with two different concentrations of nanofluids inside a stepped basin under three different cases. Results show that there is an improvement in yield of fresh water from stepped solar still by 33.18% and 41.05% using 0.1% and 0.2% volume concentration of TiO₂ nanofluid, respectively, whereas the freshwater yield from stepped still with MgO nanofluids improved by 51.7% and 61.89%. Furthermore, the economic analysis revealed that the cost of potable water from the modified solar still reduced from 0.029 to 0.016 $/kg. Similarly, the useful annual energy, yearly cost per kilogram, and annual cost per kilowatt hour are significantly profitable with the use of MgO nanofluid in the stepped basin and found as 512.46 kWh, 0.025 $/kg, and 0.026 $/kWh, respectively. It is also found that the cost of potable water from the modified still significantly increases as the amount of fresh water produced is decreased with increased fabrication cost of the solar still.     

A comparative study of 3E (energy,exergy, and economy) analysis of various solar stills

In this paper, an experimental study of the conventional solar still (CSS), the conventional solar still with glass cooling (CSSGC), the conventional solar still with basin heating (CSSBH), and the conventional solar still with glass cooling and basin heating (CSSGCBH) was carried out on the basis of the distilled water production, the energy efficiency (EnE), the exergy efficiency (ExE), and economic analysis. The CSSGC and CSSBH contain Peltier modules for cooling the glass and heating the basin. The evaporative heat transfer coefficient for all the experimental stills was calculated. The values of daily distilled water production from the CSSGCBH, CSSBH, CSSGC, and CSS were 4.56, 3.79, 2.49, and 1.89 kg/m², respectively. The daily distilled yield of the CSSBH and CSSGCBH were increased by 58.55% and 50.13%, respectively, as compared with the CSS. Moreover, the daily EnE and ExE of the CSSGCBH were 27.03% and 3.5%, respectively, whereas the EnE and ExE of the CSS were 10.88% and 1.3%, respectively. Furthermore, the cost of distilled water production was found to be 0.26, 0.35, 0.53, and 0.64 $/day for the CSS, CSSGC, CSSBH, and CSSGCBH, respectively, if the selling price of the distilled water was Rs10.     

Numerical and experimental investigation of parabolic trough collector with focal evacuated tube and different working fluids integrated with single slope solar still

This study deals with the design and fabrication of parabolic trough solar collectors (PTCs) used to increase the yield of a single slope solar still. The designed parabolic trough solar collector is investigated numerically using Ansys Fluent 18.2. The proposed solar still is coupled with a parabolic trough solar collector with an evacuated tube receiver in its focal axis using different working fluids. The working fluids are water (case 1), oil (case 2), and nano-oil (CuO/mineral oil 3% vol; case 3). In the case when the working fluid is not water, then a heat exchanger serpentine should be used in the solar still basin. The PTC has a rim angle of 82° and an aperture width of 0.9 m and length of 2.8 m. An assessment of the performance for the studied systems was accomplished under the weather conditions of Ismailia, Egypt, during summer months, June, July, and August 2019. The outcomes of closed-loop working fluids different flow rates are investigated. The experimental results of the accumulated freshwater productivities record 2.955, 3.475, 4.29, and 5.04 L m⁻² d⁻¹ for the traditional solar still and the modified cases 1 to 3 solar stills, respectively. The modified solar still in case 3 has the highest daily accumulated freshwater productivity with a percentage increase of 71.2% than the traditional solar still. The maximum daily efficiency is 46% and 26.9% for the traditional and modified (case 3) solar stills, respectively. The cost of 1 L of fresh water is 0.057 and 0.062 $/L for the traditional and the modified (case 3) solar stills, respectively.     

Effect of metal oxide nanofluids on the performance of passive solar still single slope for two different absorbent plates

This study aims to improve the performances of a solar still single slope using metal oxide nanofluid (Al₂O₃–water, Cu₂O–water, and TiO₂–water). The numerical study was carried out for the climatic conditions of Agadir, Morocco, with different concentrations of nanofluids inside a basin equipped with an absorber plate with two different absorptivities. The numerical study is based on thermal balance equations applied on different solar system components and solved using the Runge Kutta method. The numerical model is validated by comparing our results with the literature available data. A comparison study of the effect of these nanofluids on solar still productivity is done. The results show that the productivity of the solar still using nanoparticles Cu₂O, TiO₂, and Al₂O₃ are 7.38, 7.1, and 7.064 kg m⁻² day⁻¹, respectively. It is obtained that the maximum efficiency of the solar still is found to be 55.27% by using cuprous oxide nanoparticles. Furthermore, an enhancement in solar still productivity of 6.36%, 19.54%, and 33.25% is obtained by dispersing 1%, 3%, and 5% volume fraction of Cu₂O nanoparticles in pure water, respectively compared to the conventional solar. Moreover, the impact of the absorptivity of the absorber plate on the solar still effectiveness is investigated. Two types of coatings are considered to change the absorber plate absorptivity. The results indicate that the efficiencies of the solar system are 58.81% and 51.77% using an absorber plate with 0.95 and 0.85 of absorptivity, respectively.     

A tubular solar still integrated with a heat pipe

The aim of this work is to explore the thermal performance of a tracked tubular solar still (TSS) with a parabolic trough concentrator in Baghdad (33.27° N, 44.37° E) in September 2022. The present tubular still is distinguished by its hexagonal glass cover. The effect of integrating the TSS with a heat pipe, the still tilt angle (10°, 15°), and the depth of saline water inside the still partitions on the productivity of freshwater are investigated. The results showed that using heat pipe enhances the freshwater productivity by 25%–40% and the efficiency by 25%. For the still integrated with heat pipe, as the water depth is increased from 5.5 to 6.5 cm the productivity of freshwater is increased by 16% and 20% for tilt angles 10° and 15°, respectively.     

Experimental investigation on the effect of photovoltaic panel partially and fully submerged in water

This study presents an experimental analysis of improving the thermal, electrical efficiency, and yield of a conventional solar still (CSS). The photovoltaic (PV) efficiency decreases with increase in water depth inside the basin while the still efficiency is higher in the case of fully submerged condition. The maximum water production was about 8 kg/m ²/day with PV under fully submerged condition; and during off‐shine hours the still efficiency was higher when compared with the partially submerged condition. Similarly, with a decrease in water temperature the panel efficiency is increases. The maximum hourly water production with and without the PV was found to be 1.3 and 0.45 kg/m ², respectively. The main outcome of this study is that this mechanism can be used in isolated locations where there is a scarcity of current and distilled water.     

An investigation of the parameters involved in simple solar still with inclined yute

Desalination of water has been one of the most important technological work undertaken in many countries, in particular Middle East. For this purpose, solar energy is the attractive familiar way in producing such fresh water where the cost of other energy is continuously increased. This paper represents the experimental results carried out with a solar still with inclined evaporating yute to study the effects of air gap, base slope angle and glass cover slope angle on the performance of the still. In order to investigate the parameters involved in the still, three models have been designed, manufactured and tested against some experimental measurements on a still having 1m × 1m basin area. The models have been designed in a way that it can give different base slope angle and glass slope angle. A comparison between the three models has been made for three glass slope angles. The test results show that the model with base slope of 15° and glass slope of 35° gives the best results. It gives a daily desalinated water quantity of 5.6 liter/m².day.     

Theory and experimental investigation of a weir-type inclined solar still

A weir-type solar still is proposed to recover rejected water from the water purifying systems for solar hydrogen production. This consists of an inclined absorber plate formed to make weirs, as well as a top basin and a bottom basin. Water is flowed from the top basin over the weirs to the bottom collection basin. A small pump is used to return the unevaporated water to the top tank. Hourly distillate productivity of the still with double- and single-pane glass covers was measured and the latter showed higher production rates. The average distillate productivities for double- and single-pane glass covers are approximately 2.2 and 5.5 l/m²/day in the months of August and September in Las Vegas, respectively. Mathematical models that can predict the hourly distillate productivity are developed. These compared well with the experimental results. Productivity of the weir-type still with a single-pane glass was also compared with conventional basin types tested at the same location. The productivity of the weir-type still is approximately 20% higher. The quality of distillate from the still is analyzed to verify the ability of the still to meet the standards required by the electrolyzers.     

Performance of solar still with a concave wick evaporation surface

Surfaces used for evaporation and condensation phenomenon play important roles in the performance of basin type solar still. In the present study, a concave wick surface was used for evaporation, whereas four sides of a pyramid shaped still were used for condensation. Use of jute wick increased the amount of absorbed solar radiation and enhanced the evaporation surface area. A concave shaped wick surface increases the evaporation area due to the capillary effect. Results show that average distillate productivity in day time was 4.1 l/m² and a maximum instantaneous system efficiency of 45% and average daily efficiency of 30% were recorded. The maximum hourly yield was 0.5 l/h. m² after solar noon. An estimated cost of 1 l of distillate was 0.065 $ for the presented solar still.     

Experimental investigation of the effect of using the cylindrical parabolic collector,different solar panels and their cooling on seawater desalination in double-slope solar still

ABSTRACT

The present study was aimed at examining the effect of using solar panels and cylindrical parabolic collectors, or CPCs, on solar still unit. Cooling of the solar panels up to 25°C has been also conducted in order to rise the amount of produced freshwater. In the first setup, the solar still unit has been made up of 300 W and 600 W solar panels along with the CPC devices of lengths 1 m and 2 m outside for water heating. The second setup was designed in a way that water is heated by the solar panels as well as the CPC device with the copper pipe circulation inside the solar still unit, so the hot water within the pipe has raised the temperature of the water as a heat exchanger inside the solar still. Based on the results, the second setup had a higher efficiency than the first setup. Moreover, the highest amount of fresh water was 4.215 kg and 5.091 kg during one day in the first setup and the second setup, respectively. Cases 1 to 6 are related to the first setup and cases 7 to 12 are related to the second setup. The lowest fresh water production in case 1 was 2.852 kg. the highest water temperature in experimental setup 1 was 71.9 °C and in experimental setup 2 was 84.8°C.     

Exergy Analysis of Solar Still with Sand Heat Energy Storage

This paper studies the experimental and exergy analysis of solar still with the sand heat energy storage system. The cumulative yield from solar still with and without energy storage material is found to be 3.3 and 1.89 kg/m², respectively for 8-h operation. Results show that the exergy efficiency of the system is higher with the least water depth of 0.02 m (m_w = 20 kg). Competitive analysis of second law efficiency shows that the exergy efficiency improves the system by 30% than conventional single slope solar still without any heat storage. The maximum exergy efficiency with energy storage material is found as 13.2% and it is less than the conventional solar still without any material inside the basin.     

Comparative thermal performance evaluation of an active solar distillation system

In this paper, thermal models of all types of solar collector‐integrated active solar stills are developed based on basic energy balance equations in terms of inner and outer glass temperatures. In this paper, hourly yield, hourly exergy efficiency, and hourly overall thermal efficiency of active solar stills are evaluated for 0.05 m water depth. All numerical computations had been performed for a typical day in the month of 07 December 2005 for the climatic conditions of New Delhi (28°35′N, 77°12′E, 216 m above MSL). The thermal model of flat‐plate collector integrated with active solar still was validated using the experimental test set‐up results. Total daily yield from active solar still integrated with evacuated tube collector with heat pipe is 4.24 kg m^?2 day^?1, maximum among all other types of active solar stills. Copyright © 2007 John Wiley & Sons, Ltd.     

Comparative study on the multistage solar still performance utilizing PCM in variable thicknesses

In the present experimental research, a five-stage solar still was investigated using phase change material paraffin wax. Owing to Iran's climatic conditions and its location in a dry area and nonexistence of fresh water sources, producing this water from saline water sources is essential. In this research, thus, a multistage solar still was planned and examined as a commonly used freshwater source via (phase change material) paraffin wax. On the back of the collector absorber plate, paraffin wax (phase change material) was used as an additional energy source for the sun. The volume of water produced in different thicknesses of 2.5 cm, 5 cm, and without PCM was investigated. The study results specified that the application of phase change material paraffin wax in the thickness of 2.5 cm agent led to a 15% increase in freshwater production. The quantity of water generated in the flow rates of 0.7, 1.3, and 1.8 L/min was also studied. The highest quantity of water produced was obtained in the 1.3 L/min flow rate. Moreover, the quantity of water generated in the five stages of the desalination process was separately measured that the highest amount of production was associated with the first stage.     

Estimation of internal heat transfer coefficients of a hybrid (PV/T) active solar still

In this paper, an attempt is made to estimate the internal heat transfer coefficients of a deep basin hybrid (PV/T) active solar still. The estimation is based on outdoor experimental observation of hybrid (PV/T) solar still for composite climate of New Delhi (latitude 28°35′N and longitude 77°12′E). The internal heat transfer coefficients are evaluated by using thermal models proposed by various researchers. The comparison of hourly yield predicted using various thermal models to the experimental has also been carried out by evaluating the correlation coefficient and percentage deviation. It is observed that, Kumar and Tiwari model (KTM) better validate the results than the others model. The average annual values of convective heat transfer coefficient for the passive and hybrid (PV/T) active solar still are observed as 0.78 and 2.41 W m⁻² K⁻¹, respectively at 0.05 m water depth.     

Experimental evaluation of a single-basin solar still using different absorbing materials

Single-basin solar stills can be used for water desalination. Probably, they are considered the best solution for water production in remote, arid to semi-arid, small communities, where fresh water is unavailable. However, the amount of distilled water produced per unit area is somewhat low which makes the single-basin solar still unacceptable in some instances. The purpose of this paper is to study the effect of using different absorbing materials in a solar still, and thus enhance the productivity of water. Experimental results show that the productivity of distilled water was enhanced for some materials. For example, using an absorbing black rubber mat increased the daily water productivity by 38%. Using black ink increased it by 45%. Black dye was the best absorbing material used in terms of water productivity. It resulted in an enhancement of about 60%. The still used in the study was a single-basin solar still with double slopes and an effective insolation area of 3 m².     

Effect of energy storage medium (black granite gravel) on the performance of a solar still

In this study, a detailed experiment has been conducted on a single‐basin solar still which is modified with energy storage medium of black granite gravel. An attempt has been made to utilize the maximum amount of solar energy and to reduce the heat loss from the sides and bottom of the still. The conventional still is modified with an energy storage medium of black granite gravel of 6 mm size which is provided in the basin for different (quantity) depths. The black granite gravel functions as energy storage medium and also as an insulation layer to reduce the bottom and side loss coefficients. The black gravel is used for absorbing the excess heat energy from solar radiation during the noon hours. Due to this, the heat accumulated in the space between the water and glass surface is reduced and hence the temperature difference between the water and glass surfaces increases. The depth (quantity) of the gravel layer in the basin will influence the performance of the still and some of the parameters like basin temperature, water temperature, glass temperature and still productivity. This study deals with the effect of aforesaid parameters on the performance of the still. An attempt has been made to optimize the still performance for the above‐mentioned parameters. A mathematical model is developed to estimate the water, gravel, and inside glass temperatures theoretically and to estimate the hourly and daily yield. To show the effectiveness of the modification, its performance is compared with the conventional still under the same climatic condition. It is found that the still yield is increased by 17–20% with almost no cost for this modification as black granite gravel is very cheap. Error analysis was done by comparing the theoretical and experimental results to show the validity of the mathematical model. It is found that the maximum percentage of discrepancy for all the parameters is about ±18%. Theoretical value of yield per day has 8% discrepancy over experimental value. Copyright © 2007 John Wiley & Sons, Ltd.     

Productivity enhancements of compound parabolic concentrator tubular solar stills

The performance of compound parabolic concentrator assisted tubular solar still (CPC-TSS) and compound parabolic concentrator-concentric tubular solar still (CPC-CTSS) (to allow cooling water) with different augmentation systems were studied. A rectangular saline water trough of dimension 2 m × 0.03 m × 0.025 m was designed and fabricated. The effective collector area of the still is 2 m × 1 m with five sets of tubular still – CPC collectors placed horizontally with north-south orientation. Hot water taken from the CPC-CTSS was integrated to a pyramid type and single slope solar still. Diurnal variations of water temperature, air temperature, cover temperature and distillate yield were recorded. The results showed that, the productivity of the un-augmented CPC-TSS and CPC-CTSS were 3710 ml/day and 4960 ml/day, respectively. With the heat extraction technique, the productivity of CPC-CTSS with a single slope solar still and CPC-CTSS with a pyramid solar still were found as 6460 ml/day and 7770 ml/day, respectively. The process integration with different systems cost was found slightly higher but the overall efficiency and the produced distilled water yield was found augmented.