The Seawater Greenhouse: background, theory and current status

Whereas there is a growing demand for desalinated water, the process of desalinating seawater requires a substantial energy input, resulting in significant carbon dioxide emissions. In particular, the use of desalinated water for agriculture would cause huge CO2 impacts because of the large amounts of water needed. To provide water to grow food for one person would produce en estimated 2 tonnes of CO2 per year if conventional approaches to desalination and agriculture were used. The Seawater Greenhouse aims to provide sustainable local production of food by combining a growing environment in which water usage is minimised, with a desalination system powered substantially by solar energy. In this paper we describe the theory of the Seawater Greenhouse and use it to derive the minimum effectiveness required of the condenser in order for the system to be self-sufficient in water. Finally, we comment briefly on the experience gained from experimental projects and on the current status.