Potential solar earth-water distillate yields in Africa

Abstract

A model for predicting solar earth-water distillate yield for soil moisture contents up to saturation is presented. The model developed by join-point analysis for a 20 cm tall solar still with reflective interior siding is: Water Yield = C1(SR) + C2(T MIN) + C3(T MAX) − 30.65 + C4(∣T MAX − 30.65∣) + C5(MC − 8.0 + C6(∣MC − 8.0∣ + I Where SR, T MAX, T MIN, and MC represent the total daily solar radiation, maximum and minimum daily temperatures, and soil moisture content, respectively. C1, C2, C3, C4, C5, and C6 are the regression coefficients in the predictive model, and I is the intercept. The model indicates that maximum yield can be obtained at 8% soil moisture. The equation is used to predict potential earth-water distillate yields for 8 locations in Africa. Four levels of soil moisture content (5, 10, 15, and 20% by dry weight), and 50% and 100% of clear-day solar radiation and appropriate temperature values are used. For the four tested soil moisture contents the predicted daily earth-water yields vary from a minimum of 0.56 1 m −2-day −1 at 5% soil moisture and 50% solar radiation to a maximum of 2.12 1 m −2-day −1 at 10% soil moisture and 100% solar radiation. Distillate yields increase as soil moisture content increases from 5 to 10%. Above 10% soil moisture, the earth-water yield decreases as the moisture content increases. Distillate yield varies with soil moisture in the following manner: Y 10% > Y 15% > Y 20% > Y 5%, where Y is the predicted yield.