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.     

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.     

Effect of dye on the performance of a double basin solar still

The use of single basin solar stills for water distillation has been well demonstrated. However, the amount of distilled water produced per unit area is fairly low which makes the single basin solar still unacceptable in situations where space is a limitation. Malik has suggested a new conceptual design of a double basin solar still to overcome the above problem partially. The relative results obtained on a double basin as opposed to a single basin solar still are reported here with reference to (a) its performance, (b) the effect of dye in the lower basin, and (c) the effect of maintaining the raw water level in the basins.     

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.     

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     

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.     

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.     

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.     

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.     

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.     

Monthly optimum inclination of glass cover and external reflector of a basin type solar still with internal and external reflector

In this report, we present a theoretical analysis of a basin type solar still with internal and external reflectors. The external reflector is a flat plate that extends from the back wall of the still, and can presumably be inclined forwards or backwards according to the month. We have theoretically predicted the daily amount of distillate produced by the still throughout the year, which varies according to the inclination angle of both the glass cover and the external reflector, at 30°N latitude. We found the optimum external reflector inclination for each month for a still with a glass cover inclination of 10-50°. The increase in the average daily amount of distillate throughout the year of a still with inclined external reflector with optimum inclination in addition to an internal reflector, compared to a conventional basin type still was predicted to be 29%, 43% or 67% when the glass cover inclination is 10°, 30° or 50° and the length of external reflector is half the still’s length.     

Cost analysis of different solar still configurations

The enhancement of the productivity of the solar desalination system, in a certain location, could be attained by a proper modification in the system design. Therefore, different design configurations could be found in literatures. However, the increase in the system productivity with high system cost may increase also the average annual cost of the distillate. Cost analysis of different design configurations of solar desalination units is essential to evaluate the benefit of modification from the economical point of view. The main objective of this work is to estimate the water production cost for different types of solar stills. In this paper 17 design configurations are considered. Systems with higher and lower values of productivity are considered in this investigation. A simplified model for cost analysis is applied in this study. The results show that, the best average and maximum daily productivity are obtained from solar stills of single-slope and pyramid-shaped. The higher average annual productivity for a solar still is about 1533 l/m² using pyramid-shaped while the lower average annual productivity is about of 250 l/m² using modified solar stills with sun tracking. The lowest cost of distilled water obtained from the pyramid-shaped solar still is estimated as 0.0135 $/l while highest cost from the modified solar stills with sun tracking is estimated as 0.23 $/l.     

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.     

Experimental validation of passive regenerative solar still

A thermal analysis of a passive regenerative solar still is presented for different configurations. Based on an energy balance for each component of the system, an analytical expression for thermal efficiency has been derived in terms of the design parameters. The theoretical results have been validated for special cases of the system. There is reasonable agreement between theoretical and experimental observations.