A solar water purifier is described which consists of a carefully designed black plastic sheet covered by a white glass window. The plastic is formed into an array of interconnected square cells which contain impure water. The selected material ensures that no plastic taste, colour or smell is transferred to the pure water output. There are no filters, no electronics, no moving parts and cleaning is rarely needed. It is lightweight, cheap, strong, durable and can be used in any sunny location on Earth. Seawater input with 35,000 ppm of totally dissolved solids (TDS) is converted into potable water with a TDS of 1-2 ppm. Yields up to 91/m(2) day are obtained at 35 degreesC ambient or approximately 1000 W/m(2) of insolation. (C) 2003 Published by Elsevier Ltd.