2.1. Prototype

The prototype uses primarily local materials and requires no energy other than solar radiation. It is constructed from concrete, glass, a plastic barrel, paint, simple PVC fittings and tubing. The core of the design consists of a 0.83m2 concrete basin. A 240L barrel filled with seawater is connected to the basin filling the still to a depth of 1cm. The still is covered with a 0.9m2 sheet of glass on a 23° incline, hermetically sealed to keep heat and water vapor from escaping. Solar energy vaporizes the water, which then condenses on the glass. The water trickles down the incline of the glass into a trough that leads to a fresh water catch basin.

During January of 2008 the solar still produced a maximum of 2L of water per day. The distilled seawater was analyzed by the National Institute of Water Resources Management [INGRH — Instituto Nacional de Gestao dos Recursos Hidricos]. Results indicated that the sample exhibited the chemical properties of potable water, though the chemist recommended chlorine treatment to kill any potential bacteria. With the success of the solar still prototype, work began on the planning and construction of an improved solar still.