Capillary solar still for clean drinking water in informal settlements Bester, J.J.G. Department of Chemical Engineering, University of Pretoria BACKGROUND o Informal settlements −Extremely vulnerable −Size of settlements increasing −No resilience against disasters (e.g. storms, fires, floods, pollution) o Clean, potable water (drinking/cooking) −Drinking/Cooking −Necessary for survival −Access and availability major problem WATER IS LIFE o Informal settlements −Extremely vulnerable −Size of settlements increasing −No resilience against disasters (e.g. storms, fires, floods, pollution) o Clean, potable water (drinking/cooking) −Drinking/Cooking −Necessary for survival −Access and availability major problem WATER IS LIFE Problem statement o A lot of informal settlements has access to water source (e.g. river) −Contaminated water o Key challenge − Access to clean water for essential activities (e.g. drinking, cooking) o Water available from single access point −Maintenance and vandalism problems o A lot of informal settlements has access to water source (e.g. river) −Contaminated water o Key challenge − Access to clean water for essential activities (e.g. drinking, cooking) o Water available from single access point −Maintenance and vandalism problems LOGISTICS o Will deploy a unit to each household o 8 – 10 L/day average clean water (enough water to do essential activities e.g. drinking/cooking) o Estimated unit cost: R 300 o Will deploy a unit to each household o 8 – 10 L/day average clean water (enough water to do essential activities e.g. drinking/cooking) o Estimated unit cost: R 300 THE INVENTION o Water from the sun o Solar still −Simple system −Low maintenance −No operating cost o Capillary solar still −Jute cloth raise active surface area for evaporation −Black dyed cloth – Improved solar absorption −Uses capillary forces and concentration profile to migrate water to collector surface −Water evaporates & condenses on cover −UV radiation/temperature kills bacteria −Improved efficiencies (50 % - 55 %) o Building materials – Local, widespread, cheap −3mm thick black HDPE body −Black dyed jute cloth (replaceable by synthetic fabrics e.g. piece of clothing) −Acrylic glass (PMMA) (90 % transmissive) o Maintenance −Daily cleaning of dirty water holding tank −Occasional cleaning of jute cloth −Occasional cleaning of PMMA cover o Water from the sun o Solar still −Simple system −Low maintenance −No operating cost o Capillary solar still −Jute cloth raise active surface area for evaporation −Black dyed cloth – Improved solar absorption −Uses capillary forces and concentration profile to migrate water to collector surface −Water evaporates & condenses on cover −UV radiation/temperature kills bacteria −Improved efficiencies (50 % - 55 %) o Building materials – Local, widespread, cheap −3mm thick black HDPE body −Black dyed jute cloth (replaceable by synthetic fabrics e.g. piece of clothing) −Acrylic glass (PMMA) (90 % transmissive) o Maintenance −Daily cleaning of dirty water holding tank −Occasional cleaning of jute cloth −Occasional cleaning of PMMA cover IMPACT ON WATER AVAILIBILITY o Not dependent on single water source, responsible for own system o Avoid long ques, long walking distances and insufficient clean water availability o Reuse water (e.g. washing, laundry, dishes) as the water is cleaned of all contaminants when evaporated o Clean water from available but contaminated water sources o Resulting in lower vulnerability and higher resilience against the availability problems of clean, potable water o Not dependent on single water source, responsible for own system o Avoid long ques, long walking distances and insufficient clean water availability o Reuse water (e.g. washing, laundry, dishes) as the water is cleaned of all contaminants when evaporated o Clean water from available but contaminated water sources o Resulting in lower vulnerability and higher resilience against the availability problems of clean, potable water Components and operation of a capillary still (Tiwari, GN, Singh, HN and Tripathi, R (2003) “Present status of solar distillation”, Solar Energy, 75, 367 – 373.).