Solar Desalination Theory
The sun has been providing energy for billions of years. As long as there have been humans, we have used that energy to grow food and warm homes. The sun can also make life possible in places that otherwise wouldn't be possible by using its energy to create fresh drinking water through a process called solar desalination. Does this Spark an idea?
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The Facts
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There are two methods of solar desalination. One method is reverse osmosis (RO), which provides exceptionally clean water but requires filter membranes to be replaced on a regular basis. The other, solar humidification-dehumidification (SHD), uses just solar energy alone to convert salt or brackish water to fresh water. This system works on the principle that as water evaporates, water vapor rises and the residues or chemicals that were dissolved in the water are left behind. RO systems can be costly in the long run, so this article will focus on SHD systems.
Geography
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SHD systems work best where there is not a lot of cloud cover to block the solar energy from evaporating the water. Luckily, places that have very few clouds are usually the places that are in need of water, such as deserts. This provides a perfect matching for the SHD system. The most ideal setting would be a desert area next to a water source like the ocean, such as the Sahara desert or the Northern Territory of Australia.
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Features
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An SHD structure is built like a greenhouse with either a concave or pointed roof. The interior has two sets of piping. One set brings in the salt water via a pump or gravity feed system. The other removes the fresh water from the system. As the water evaporates and the vapor begins to rise, it will attach to the ceiling and form water drops. The shape of the roof then forces these water drops to the outer edges, where the fresh water receiving receptacles are placed.
Size
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An SHD does not have to be a specific size in order to work, but can be scaled up or down based on space available and amount of fresh water required. Before building an SHD give serious thought to how many people it's intended to supply now, and how many people there will be in the future. Although you can always build another SHD system, building some additional capacity into a system is a good idea.
Warning
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A big concern with an SHD is that a warm, wet area, such as on the fresh water side, will be a haven for bacteria and algae. It's extremely important that your SHD be cleaned on a regular basis to reduce the chances of a dangerous bacteria growing in the fresh water side of the SHD.
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