Transient analysis of a stepped solar still for heating and humidifying greenhouses Original Research Article

This paper presents the transient analysis of a stepped solar still for heating and humidifying agriculture greenhouses (GH). The still body consists of five stepped basins insulated from the bottom with an inclined glass cover. Air from the GH enters the still from the bottom and flows between the basins and glass cover where it is heated and humidified, and then re-enters the GH from the still top. The still performance parameters, i.e., still components heat rates, air temperatures and humidity, still yield and efficiency are analyzed and presented. The results show that (1) the still daily average efficiency (ηav) is about 63%; (2) total daily yield is about 4.92 L/m2 out of which 0.81 L/m2 is condensed on the glass cover and the rest (4.11 L/m2) enters the GH as humidity carried by the circulating air; (3) temperature distribution for still components increases along the still and follows the sinusoidal trends as the solar intensity; (4) circulating air relative humidity increases along the still and always leaves the still at saturation conditions; and (5) decreasing air flow rate has an insignificant influence on the system productivity; however, it does influence the GH heat load.