Drinking with the Wind

Many developing countries are dealing with a shortage of safe drinking water. Desalinating seawater is a common way to obtain fresh water, but existing desalinating windmills are costly and far from energy efficient. TU Delft researchers have developed a windmill that does not require electricity or fuel and is more energy efficient. 

Reverse osmosis
A commonly used method to desalinate seawater in areas that have no or limited surface water is reverse osmosis. High pressure pumps push seawater through a cylinder consisting of a series of porous polymer membranes and the water comes out desalinated. Countries such as Israel, for instance, use seawater reverse osmosis to obtain drinking water. The pumps, however, are usually powered by electricity or fuel and require a lot of energy. That is why TU Delft researchers came up with the idea to develop a windmill that directly powers a high pressure pump.  

The combination of a windmill and reverse osmosis for the purpose of desalinating seawater isn’t a new one. However, existing desalinating windmills convert wind energy into electricity, which is stored and later used to power the pump. Due to the electricity storage and the electricity or fuel required to power a generator, these windmills are quite expensive. In addition, there is substantial energy loss in the transmission. As both money and electricity or fuel can be hard to get by in remote coastal areas, we developed a desalinating windmill that does not require electricity or fuel and isn’t as costly, because it directly uses wind energy to pump seawater through the membranes.

A complicating factor in using this technique is the fact that the pump is left to the mercy of the wind. In very high winds, it might push too much water through the filter, leaving behind a highly concentrated salt and calcium solution that could clog up the filter. This problem was solved by adding a second, smaller pump to the purification plant, which acts as a buffer to catch excess pressure and reroutes it back into the system. Furthermore, at any given time the system only turns 30 percent of the incoming seawater into drinking water. The remaining 70 percent comes out a highly concentrated residue, and is re-used.  

Practical use
Our desalinating windmill is especially suited for small communities in coastal areas without fresh water access. Based on the windmill’s power, it can produce an estimated 5 to 10 m3 of fresh water a day, enough to supply a 500-people village with drinking water. Eventually it should be possible to produce the windmill for around 35 thousand euro. It will then be able to produce one thousand litres of fresh water a day for 1 to 1,5 euro. A water reservoir will make sure the drinking water supply is sufficient even when there is no wind for five days straight.

Name author: webredactie
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