Harvesting potable water from humid air at competitive cost

Posted on May 09, 2016
Posted By: Harry Valentine

Producing Potable Water from Geothermal Energy and Cooling Towers


The energy industry has long used cooling towers to condense exhaust steam into liquid water, for re-use in thermal power stations. Cooling towers form the basis of energy chimneys that create an updraft of air that passes through air turbines to produce electric power. The geothermal industry has developed seasonal heating and seasonal cooling by using the thermal capacity of ground water found in subterranean layers of gravel. There is potential to combine these technologies in regions that experience intense summer humidity, to produce potable water at competitive prices for nearby populations.

Such technology would be applicable at locations where ambient daytime and night time temperatures are too high for water to condense on to vegetation or on to mesh fences installed at strategic locations. The mining, oil and gas exploration sectors have developed seismic testing techniques to identify the nature of the subterranean geology that may include layers of gravel capable of holding massive volumes of seawater that may be used for seasonal geothermal storage purposes. Combining proven technologies from diverse sectors of the energy industry offers a method by which to harvest potable water from intensely humid air.

The oil and natural gas industry of the Middle East has uncovered several unique applications for seawater. They initially pumped seawater into deep level underground porous rock to displace residual natural gas while an oil well project in Saudi Arabia pumps massive volumes of seawater deep underground to displace crude oil that would otherwise have remained underground. Some coastal cities that were in need of potable water pumped massive amounts of groundwater, only to discover that seawater slowly seeped inland into the soil and underground gravel to replace the displaced potable groundwater.

Away from the ocean coast, some inland cities have discovered that they could store potable water underground, as groundwater. During the rainy season, massive volumes of potable water may be diverted deep underground, to seasonally replenish the supply of groundwater. However, a new approach may be applied at locations where seawater has displaced the depleted groundwater. During the cool season, it becomes possible to cheaply reduce the underground water temperature, including using cold ocean water from the greater depths as a heat sink. As summer weather approaches, massive volumes of saline groundwater could be near the freezing point.

During summer, cold saline groundwater pumped through corrosion-resistant pipe networks could provide interior cooling to campuses of large buildings. At locations that endure extreme summer humidity, the combination of structures built to the shape and size of power station cooling towers could along with cold saline groundwater, provide large volumes of potable water harvested from the humidity. Warm air rises inside tall chimneys, assisted by concentrated solar thermal energy applied to the upper levels of the towers, to initiate and sustain convectional that draws humid air into the base of each tower.

Cold saline groundwater would be pumped through heat exchangers installed at the lower levels of each tower, just above the inlets through which incoming humid air would flow. The heat exchangers would condense the humidity from the incoming air while a water collection and pipe network would transfer the potable water into storage tanks. The concept of condensing potable water from humid air has proven successful and offers a potentially low-cost method of producing potable water at locations where humidity may be high while rainfall may otherwise be quite miniscule.

Solar heated chimneys are also well proven as a means by which to to initiate a convection of air. Some large-scale cooling towers may operate on convection due to their sheer physical size. Prevailing winds usually carry humidity from the sea and from waves that break along the shore with considerable spray, toward land and higher elevation. A cooling tower adapted to extract potable water from humid air would need to be located near to the coast as well as an underground deposit of gravel that is saturated with seasonally cold seawater.  

Authored By:
Harry Valentine holds a degree in engineering and has a backround in free-market economics. He has undertaken extensive research into the field of transportation energy over a period of 20-years and has published numerous technical articles on the subject. His economics commentaries have included several articles on issues that pertain to electric power generation. He lives in Canada and can be reached by e-mail at harryc@ontarioeast.net .

Other Posts by: Harry Valentine

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