The performance investigation of triangular solar stills having different heat storage materials

Abstract

Desalination of water can be achieved via the use of solar stills, especially as they are considered to be the cheapest option for potable water production in remote, arid and small communities with limited availability of freshwater. However, one very common challenge with water production via solar stills is that the amount of water produced is usually low. The aim of this work is to evaluate the productivity enhancement of solar stills using different heat storage materials in the basin. To conduct the experiments, three triangular solar stills were fabricated with similar shapes. In each solar still, a transparent polythene film and a stainless steel trough as cover and basin were used, respectively. Each basin had a length of 50 cm, width of 30 cm and depth of 8 cm. The solar still configurations differed based on inclusion of 2 cm depth of black soil or a layer of black paint in the basin. Experimental outputs indicated that there was significant increase in the amount of potable water produced using different heat storage materials under Malaysia tropical condition. Daily cumulative results of water production using these solar stills showed that the solar still with black-painted basin was more efficient; its level of productivity over the conventional solar still and the solar still with black soil in basin was 101 and 20 %, respectively. Some water quality parameters were also tested in the laboratory which indicated that the treated water met the WHO standard for drinking water.Keywords Solar distillation Á Stainless steel basin Á Black soil Á Black paint Á Potable water Nomenclature T w1 Temperature of water of solar still SS1 (°C) T w2 Temperature of water of solar still SS2 (°C) T w3 Temperature of water of solar still SS3 (°C) T a Temperature of ambient air (°C) T ic1 Temperature of inner cover of solar still SS1 (°C) T ic2 Temperature of inner cover of solar still SS2 (°C) T ic3 Temperature of inner cover of solar still SS3 (°C) I s Solar irradiance (W/m2) W h1 Hourly water production of solar still SS1 (L/m2) W h2 Hourly water production of solar still SS2 (L/m2) W h3 Hourly water production of solar still SS3 (L/m2) W c1 Cumulative water production of solar still SS1 (L/m2) W c2 Cumulative water production of solar still SS2 (L/m2) W c3 Cumulative water production of solar still SS3 (L/m2) V Wind speed (m/s)

Potable water production using two solar stills having different cover materials and fabrication costs

“…It can be observed from Figure S1, Supporting Information and Figures (4 and 5), and 6 that similar patterns were noticed for both solar stills, where the basin water temperature (T w ), and inner and outer cover temperatures (T ci and T ce ) increased to the maximum values at 2.00 PM corresponding to the highest hourly average solar irradiance and then they decreased corresponding to the decrease in solar irradiance throughout the day ( Figure S1, Supporting Information and Figures 5 and 6). These findings conform to studies by other investigators [4,6].…”

“…Similar pattern has also been reported in previous works [6,30,31]. Figures 5 and 6 show the hourly water production for PSS and GSS, respectively.…”

“…Thus, the above mathematical equations can be applied for both solar stills using different cover materials. The effect of using flat black paint in the stainless steel basin can be observed with the increase in solar radiation absorption by basin due to lower absorptivity of stainless steel itself as compared to the absorptivity of flat black paint ((a st 5 0.37) [21] < (a fb 5 0.97) [22]) which resulted in higher water temperatures as compared to the values of T w in conventional solar still without painting the basin black [6].…”

“…The covers of solar stills are usually made of heavy glass and this can make fabrication difficult particularly in remote, rural, and coastal areas [4]. The PSS and GSS had different fabrication costs of RM 82.50 and RM 416.00 or US$22.54 and US$113.66 respectively (Tables 2 [6] and 3). The PSS was made using local and cheap materials as well.…”

“…In order to improve the productivity of passive solar stills, some researchers have conducted experiments to evaluate the performance of solar stills using different transparent cover materials. An investigation of three passive solar stills with different heat storage materials in basin, tilt angles of 608, transparent polythene film covers, PVC pipes as frames and stainless steel troughs as basin was conducted in Malaysia [6] in order to compare their outputs. Stainless steel troughs were used as basin of the solar stills in order to prevent the basin metal, that is exposed to water and humid air inside the solar still, from corrosion [7].…”