Design, Development And Testing Of An Active Solar Vacuum Water Distiller

Motivation for this project was resulted from a visit in dry zones in SriLanka. Afterthe thirty years civil war the peoples who living that region, have limited availability ofclean water resources. They do not have adequate technology and money to access forgroundwater purification and thus their inhabitants are exposed to the elevated levels.Hence these peoples are potentially liable for diseases, such as the fluorosis, and manymore bacteria or arsenic problem as they do not have any other options, additionallythey never think their safety too.Due to the facts of marginalization and poverty it is important to investigatetowards decentralized and economical technologies which can be applied on a small-scale level. A low-cost and “low-tech” approach is necessary in order to provide thepeople with a technology which they can construct, operate and maintain themselvesalone. A promising approach is the technology of solar distillation for drinking watersupply on domestic level, making use of the high regional potential of solar energy. It isproven that this technology is capable of removing nearly any type of contaminants(inorganic and bacterial) from the raw water. The simplest and most durable form ofimplementation are the passive solar stills. But, the major drawback consists in its lowdaily output of drinking water (about two to four liters per square meter of insolatedarea). Hence an active solar system is considered to achieve the daily distillate yield.In this project a prototype unit of the active solar distillatory was built whichefficiently produce clean drinkable water from nearly any water source. The emphasisin construction was put on the use of local, economical and recycled materials as far aspossible, in order to lower the costs, attain a high reproducibility and to facilitate thepossibility of autonomous self-construction in rural areas. Hence the fabricated device isrelatively cheap, easy maintenance and depends only on renewable solar energy.In this system a parabolic solar trough was fabricated coupled with a customdesigned distillation device. The incoming solar radiation from the sun is focused andconcentrated onto a receiver vacuum tube by the parabolic trough then heating theincoming impure water, at which point it is sprayed into a custom designed distillationdevice where it evaporates and is re-condensed into pure potable water by passing steamthrough a cooler. The obtained results are very satisfactory in respect to theclimatological conditions of the project region and the typical efficiency and distillate output of the applied design. Mean daily distillate yields of around10L were reachedand it is sufficient for the drinking water supply of a family of four members.Furthermore the theoretical output of the system was calculated using basic heattransfer equations and they are compared with the experimental results. The projectfabrication and construction costs are determined. An additionally analysis of thedistillate water quality is made using pH meters and it was within the acceptable limits.Nevertheless, the construction of the proposed active unit is important for thefuture, since the water pollution increasing continuously with the global technologicalexpansion.