DeSol – Solar seawater desalination by gravity-supported vacuum distillation

In the last years, the extensive usage of drinking water and the climate change caused a shortage of drinking water in many regions of the world. In costal areas, e.g. in Southern Europe and on many Mediterranean islands the groundwater is already contaminated by the intrusion of seawater. At the same time, precipitation in many areas is decreasing while the demand of drinking water is increasing. Even nowadays, a couple of islands get their water supply already by tank ships. The global population development and the tourism industry will intensify this problem in the future. Therefore, the production of drinking water from renewable fresh water sources is becoming more and more difficult.

Desalination of sea or brackish water is necessary to assure the water supply of many areas. Common desalination technologies like reverse osmosis and usual thermal desalination techniques are energy intensive and require high amounts of fossil fuels with the additional disadvantage of high CO₂ emissions. The costs for desalination are continuously rising due to the shortage of natural resources.

The Fraunhofer Institute for Interfacial Engineering and Biotechnology IGB and an European Consortium consisting of partners from industry and research centers develop an energy efficient and cost-effective technology for sea water desalination.

A vacuum distillation process with multiple stages enables the efficient usage of heat at low temperatures. Although the process works at low pressure no vacuum pumps or injectors are needed. Instead an innovative concept utilising gravity for vacuum production and maintenance is used. The process control is mainly done by hydraulic or mechanical components in order to minimize the requirement of measurement and control equipment. The technology is simple and has a modular design. The automated operation and the low maintenance efforts enable a continuous and user friendly handling.

By using common thermal solar collectors for heat supply and (on a small scale) photovoltaic collectors for the electric components, an independence from fossil fuels and the electricity grid is achieved. Furthermore, the usage of waste heat from industry processes or other sources is possible.

Small to medium sized facilities are suited for a decentralized, sustainable drinking water production (100 litres to approx. 10m³/day), like:

• Small scale (single households)
• Hotels and tourism sites
• Small neighbourhoods with independent water supply
• Production of demineralized water or drinking water for small or medium sized enterprises

Further areas of application:

• Reduction of waste water volume in various industry sectors (e.g. small enterprises) by concentration of the waste water and reuse of distillate for production
• Concentration of solutions (e.g. chemical or food industry)