Aqua Solaris – an optimized small scale desalination system with 40 litres output per square meter based upon solar-thermal distillation

Abstract

Classical small scale solar distillers (flat collector solar stills) have been in use especially in remote tropical locations for more than a century, but they only utilize a fraction of the available solar energy flux per area. Our aim was to develop a system that optimizes the energy efficiency and approaches the physical limit of freshwater output as close as possible. The construction takes into consideration the general principles of thermodynamics. The evaporation and (cooled) condensation chambers were separated, the evaporation chamber and surface increasing material were expanded into the third dimension (a collector cubicle instead of flat collector), additional mirrors are applied to increase the solar energy input and for wind protection, and the necessary electronic microcontroller that controls the airflow rhythm was empirically optimized by a long series of test runs and measurements. A prototype on the Island of Bonaire currently produces 40 l of freshwater per square meter surface area at an ambient temperature of 30°C for an estimated life cycle of 20 years. The applications are broad. Each unit can supply a large family with freshwater at low costs, and the water source can be anything from sea water to water polluted with heavy metals and mineral poisons (e.g. arsenic polluted wells in Bangladesh). The concept builds upon readily available low-cost standard materials and parts and can help to alleviate numerous social and environmental problems, including local dependence on bottled water import, the related garbage build-up on islands and adjacent coral reefs, water borne diseases as well as desertification, deforestation and even unemployment. In addition to scientific and technical details various project proposals, participatory approaches with local end-users and business models are presented.