Enhancement of daily yield in a double basin solar still

A straightforward transient analysis of a double basin solar still has been presented, incorporating the effect of water flow over the glass cover and flow of hot water in the lower basin by a flat plate collector. It is concluded that, for higher daily yield, the collector should be disconnected from the still during off-sunshine hours.     

Analytical study of multi-effect solar still

A simple analytical study of the multi-effect wick type solar still has been presented incorporating the effect of various parameters, viz, still length, water flow velocity, inclination of absorber, etc. It is observed that (i) the performance of the still increases with a decrease of flow velocity for a particular length of still and (ii) the optimum number of condensing surface area is found to be 3, and after that, there is not any significant ouput. Numerical calculations have been carried out for a typical day in the month of April, at Port Moresby, Papua New Guinea.     

Transient analysis of double basin solar still

The effect of water flowing over the upper glass cover of a double basin solar still on its transient performance has been presented. A comparative study of the daily distillate production of a double basin solar still with and without water flowing over the upper glass cover has been made, and some interesting conclusions have been drawn. Numerical calculations have been made for a typical hot day (viz 2 May 1980) in Delhi.     

Performance of a double condensing multiple wick solar still

Because of high insolation on hot days, the condensing glass cover of a simple multiple wick solar still becomes reasonably hot, and hence, the yield is not very high. To increase the yield under this situation, a double condensing, multiple wick solar still has been proposed. In this case, the area of the condensing surface can be increased by introducing an additional G.I. sheet just below the blackened wet jute cloth with a slight spacing around the absorbing surface, such that the excess of vapor can also be condensed below the G.I. tray G₁ and above the G.I. tray G₂.     

A step basin type solar water heater-cum-solar still

This communication reports the design details, performance and testing of a step basin type solar water heater-cum-solar still. The combined efficiency of the system is 64.5 per cent.     

Double basin solar still

This paper presents a periodic analysis and observed performance of a double basin solar still, mounted on a stand. Observations on this type of still are in fair agreement with the results of analysis. The daily distillate production of such a still is on the average 36% higher than that of a single basin still. Some aspects of the operation, design and performance have also been discussed.     

Single basin solar still coupled with flat plate collector

This paper presents the transient performance of a single basin solar still coupled with a flat plate collector. The average daily production of distilled water has been found to be 24% higher than for a simple single basin solar still     

Solar distillation of water using a V-trough solar concentrator with a wick-type solar still

A V-trough solar concentrator has been combined with an inclined flat-plate wick-type solar still. Outdoor testing was carried out with and without the solar concentrator on clear days in summer and winter. The equipment was used to investigate the enhancement of the outdoor performance of the wick-type solar still by the solar concentrator.It has been concluded that use of the solar concentrator with the inclined wick-type solar still can lead to a greater fractional increase in still efficiency and productivity on clear days in winter than on clear days in summer.     

On the verification of the effect of water depth on the performance of basin type solar stills

Many experimental and numerical studies have been done on different configurations of solar stills to optimize the design by examining the effect of climatic, operational and design parameters on its performance. The majority of the investigators presented their results in scatter diagrams rather than correlations. One of the most important of the operational parameters that has received a considerable attention in the literature is the brine depth. A good number of the investigations on the effect of brine depth are cited in this study. For each of these studies, a correlation was developed from the data reported by each study. A concluding correlation from all brine depth data was developed. The correlation showed a decreasing trend in the productivity with the increase in the brine depth. An experimental study was subsequently conducted to verify this trend by an experimental investigation on a solar still that was constructed and tested with five different brine depths, namely 1, 4, 6, 8 and 10 cm. The present study validated the decreasing trend in productivity with the increase of brine depth and showed that the still productivity could be influenced by the brine depth by up to 48%.     

Demonstration plant of a multi wick solar still

A solar distillation plant of capacity 70 litres/day (annual average) has been installed at the Centre of Energy Studies, Indian Institute of Technology, New Delhi, India. The system has been working for the last 1 year, and its performance is found to be satisfactory. It meets the requirements of distilled water in the Institute.     

Further studies on double solar still

This paper is devoted to the development of a transient model of the performance of a double solar still and its validation by experiments. the dependence of the daily output of the distillate on wind velocity, ambient temperature and daily insolation has been studied analytically. It is seen experimentally that the presence of a black dye in the lower basin increases the distillate output by 10 to 15 per cent.     

An analytical expression for efficiency of solar still

In this Technical Note, an analytical expression for the efficiency of a solar still has been derived as a function of solar still and climatical parameters. The analysis is based on the basic energy balance of the solar still. It is observed that an expression for the efficiency of a solar still is of the same form as obtained for a flat-plate collector.     

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.     

Development of a tube-type solar still equipped with heat accumulation for irrigation

A tube-type solar still is found to be suitable for use in desert irrigation. The effectiveness of a heat accumulator with regard to distillate productivity is experimentally and numerically verified. The heat accumulator consists of tube bundles immersed in wax in order to utilize the latent heat of wax. The dynamic response to stepwise variation of irradiative intensity verified the contribution of wax to an increase of productivity only when the phase change of wax occurred. The effective distillate productivity was found to be 294.3 g/m² during the cyclic stepwise change of irradiative intensity, from 200 to 600 W/m² and back. Velocity vectors driven by natural convection and temperature contours estimated by numerical simulation verified the effectiveness of the heat accumulator especially after peak solar intensity. The latent heat of wax effectively contributed to a 15% increase in total distillate productivity per day. The still can feasibly meet irrigation water supply demands above an irrigative threshold of 17 MJ/m² d.     

Improvement of basin type solar still performance : Use of various absorber materials and solar collector integration

Experimental measurements to determine conditions necessary for efficient solar desalination are given. The effects on performance of using various different absorber materials together with the integration of flat-plate collectors with storage systems in basin type solar stills are investigated. Correlations between daily yield (Y, in litres) and solar insolation (I, in MJ/m²day) are found to be, Y = 0.152I − 0.706 (for black-paint absorbers), Y = 0.180I − 0.987 (for charcoal absorbers), Y = 0.225I − 0.467 (for integrated solar collector and storage system, with black-paint absorbers). The calculated daily-average monthly yields for each case are also given.     

Single basin double slope solar still with minimum basin depth and energy storing materials

Solar still is a simple device which can convert available waste or brackish water into potable water using solar energy. A single basin double slope solar still with an inner basin size 2.08 m × 0.84 m × 0.075 m and that of the outer basin size 2.3 m × 1 m × 0.25 m has been fabricated with mild steel plate and tested with a layer of water and different sensible heat storage materials like quartzite rock, red brick pieces, cement concrete pieces, washed stones and iron scraps. It is found that, the still with ¾ in. sized quartzite rock is the effective basin material. The still is theoretically modeled. In previous researcher’s work, variation in transmittance is taken as constant. The variations in solar incidence angle and transmittance of the covers are also considered in this work. The theoretical values are compared with actual values. The theoretical water and glass temperatures and the theoretical production rate are having higher deviation with actual. Hence, another thermal model developed for this still is applied to validate the results accurately. It is found that, the theoretical production rate using thermal model agrees well with experimental.     

Transient analysis of solar still

This paper presents an analysis of the transient performance of a basin type mounted still; explicit expressions for hourly variation of temperature of glass cover and water in the basin and distillate output have been obtained. The results of the analysis are in good agreement with experiments.     

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.