Solar Desalination

Solar Desalination | Low Temperature Solar Thermal in Australia | Further Information | References

Solar Desalination

Where water quality is poor, either because it is saline, as in many parts of central Australia, or contaminated with biological organisms, water desalination and pasteurisation are essential for the provision of water suitable for drinking and cooking. Solar desalination is the desalination of water using solar energy. Solar desalination in the modern era extends back to the early 1950s when simple solar stills were studied for remote desert and coastal communities. The cheap availability of water pumps and pipelines and declining energy costs in the 20th century, ensured these were not competitive for community-scale projects. Recently, there is evidence of emerging research interest in the field. This is prompted by growing energy costs, demand growth in the face of depleted fossil water stores, and the growing human pollution of many communities' water supplies (Wikipedia, 2006).

The Solar Humidification-Dehumidification-Method (HDH)

HDH is a thermal desalination method. It is based on the evaporation of sea water or brackish water and consecutive condensation of the generated humid air, mostly at ambient pressure. This process copies the natural water cycle. The most simple configuration of this technology is the solar still, evaporating the sea water inside a glass covered box and condensing the humidity on the lower side of the glass cover (Wikipedia, 2006).

In box type collectors, as the internal temperature of the collector rises, water molecules from the saline solution gain heat energy, allowing them to evaporate. Desalinated water droplets condense on the internal side of the transparent cover and are channelled into a collector (see Figure 1).

Figure 1 The Solar Desalination Unit at the Solar-Institut Jülich in Germany.

More sophisticated designs separate the solar heat gain section from the evaporation-condensation chamber. An optimised design comprises separated evaporation and condensation sections. A significant part of the heat consumed for evaporation can be regained during condensation. An example for such an optimised thermal desalination cycle is the Multiple-Effect-Humidification-Method (MEH). MEH applies multiple evaporation-condensation cycles at separate temperature levels in order to minimise the total energy consumption of solar humidification processes. A desalination plant in Saudi Arabia uses MEH technology powered by solar energy to supply an office building in Jeddah. This installation (see Figure 2) uses the heat from 140 m² solar collectors delivered by the German Company Citrin Solar and supplies about 5000 litres of drinking water to the roof storage unit (MAGE-TiNOX Group, 2006).

Figure 2 The MEH MidiSal TM 5000 desalination unit, built by the Austrian MAGE-TiNOX group. This desalination system was commissioned in December 2005 in Jeddah. (photo courtesy of the MAGE-TiNOX Group).

Another method of solar desalination that has been developed is the Solar Multistage Condensation Evaporation Cycle (SMCEC). The SMCEC is a technique for solar desalination using natural convection in a vertical chimney. It uses a natural chimney effect to draw the outgoing heated water vapour past condenser plates (through which the incoming water runs), thereby pre-heating the incoming water and increasing the overall system efficiency (Wikipedia, 2006).

Low Temperature Solar Thermal Technologies in Australia

For some of the research in solar thermal technologies in Australia click here

Further Information

RISE Resources - Information regarding available renewable energy resources.

RISE Technologies - An extensive collection of information regarding renewable energy technologies.

RISE Applications & System Design - Renewable energy application information and system designs.

RISE System Displays - Case studies and information on installed renewable energy systems & performance data.

The Energy Resources Institute – Solar Thermal

The Solarserver – Solar Thermal Technologies in the United States

Australian National University – Solar Thermal Energy Research

Wikipedia – Solar Energy

Renewable Energy Commercialisation in Australia – Solar Thermal

Texas Water Development Board - An Introduction to Thermal and Membrane Methods of Desalination

Texas Water Development Board has many excellent resources on their Desalination Activities Page

References

Wikipedia, 2006. “Solar Desalination” (Online) http://en.wikipedia.org/wiki/Solar_Desalination (Accessed 23 February 2007).

MAGE-TiNOX Group, 2006. "Solar driven desalination unit supplies office building in Jeddah " (Online) http://www.tinox-watermanagement.de/ie1024/news-3img-1024.htm (Accessed 23 February 2007).