Need for and Possibility of Integrating Solar Desalination with Polyhouse in Arid Areas like Kutch

Development of agriculture in arid areas like Kutch is impeded because of widespread salinity and scarcity of good quality water. In view of this and the fact that insolation is high, we examine in this paper the possibility of integrating solar stills with greenhouse. Distillate yield on one hand and water demand from plants on the other are both driven by intensity of radiation. This feature makes the still appealing as a partial source. But, requirement of large evaporation area is a deterrent. Some investigators have reported that one would need a still of same (basin) area as the crop or even more to meet the water demand. This would appear to be true. A considerable reduction in the required evaporation area is therefore needed to make such a scheme feasible. This matter has been examined here a little more closely than found in literature. In particular, possible reduction by use of blending the distillate with groundwater is analysed. Analysis suggests that if distillate is blended with local water to reduce its salinity to the tolerance threshold of the crop, size of the still can be reduced significantly. Climatic conditions of Bhuj (Kutch) have been used in analysis. Tomato and beet have been used for illustration. Although, blending offers considerable scope, it is necessary to explore further avenues of reducing the required still size. Use of enclosures (polyhouse for instance) to reduce the crop water demand is suggested as a further important means of this.