In order to advance the concept of desalination by evaporation, I travelled to one of the driest regions in Europe to test my idea.
Filed trial in Spain
General conditions
The field trial took place in Spain on the Mediterranean coast.
Like Sicily (Italy) or Peloponnese (Greece), this part is severely affected by water shortages.
Weather
The region was dry and the sun was already very strong for April. The sand heated up to over 40°C at midday.
Black metal sheets heated up to over 60°C in the sun.
The hotter the weather, the more efficiently the systems work, as the seawater is preheated to a higher temperature using solar thermal energy. This means that less electrical energy has to be used to ultimately vaporise the salt water.
The output of the systems is also higher when the weather is sunny and there are more hours of sunshine.
This means that the most fresh water is produced precisely when it is needed most: The plants behave proportionally to the weather.
Checking salinity
All oceans have different levels of salt. Theoretically, the Atlantic has a salt content of 3.5%, the Mediterranean 3.8% and the Dead Sea 28%.
I wanted to check this myself and evaporated all the water in a basin.
One litre of evaporated sea water resulted in one litre of fresh water plus 38 grams of salt.
Conclusion
Evaporation by combining direct solar power (thermal heat) and photovoltaic power (electrical heat) works amazingly. This test was producing steam (100°C) and a steady rivulet of fresh water in no time. The efficiency isn’t that great yet, but given the high demand for fresh water, low budget systems that are easy to run and maintain are one part of the bigger picture.