Cold Ocean Depths Could Help Provide Freshwater for the Middle East

States located around the Persian Gulf are seeking alternative sources of potable water and have even considered the possibility of towing icebergs from the Antarctic. The combination of intense summer humidity, a nearby abundant source of a cold sea water, and advanced cooling tower design offers the region the potential to condense massive volumes of potable water from intensely humid air.

Introduction

While the Gulf states desalinate seawater to provide potable water for their populations and recycle used potable water, they still seek alternative cost-competitive sources of potable water. One option would involve carrying potable water inside tanker ships, including water from icebergs at the Antarctic. An alternative option would involve extract potable from humid summer air in the region, using an abundance of cold seawater.

Summer air temperatures in the eastern region of Oman often exceed 90 degrees F with humidity reaching 80 percent. Extracting potable water from the humid air on a massive scale would require the construction of several super-size cooling towers along the coast of Oman. The upper levels of each tower could be heated by concentrated reflected solar thermal energy, sufficient to produce powerful updrafts of air inside each tower. The intensely humid air would flow through an array of large radiators cooled by cold seawater flowing through the cooling passages, using seawater sourced from the Gulf of Oman.

Depth and Temperature

Solar thermal energy warms surface seawater to a depth of around 200-feet. During the northern summer when surface seawater temperature in the Gulf of Oman approaches 86 degrees F, seawater temperature at greater than 2000-feet below surface would remain around 40 degrees F. The Gulf of Oman lies in the northwestern region of the Arabian Sea, which is well in excess of 6,000-feet deep.

The sheer size and depth of the Arabian Sea provides an abundance of cold seawater that could be used productively on coastal land at Oman, depending on permission from the government of Oman. It would be possible to extract seawater from over 2,000-feet of depth and flow the cold seawater through an array of large radiators before returning the seawater to the ocean near the surface.

Water from Air

Water extraction from moist air is common at smaller scales. Fog fences are used in many mountainous locations internationally, to collect water from humid air. Modern dehumidifiers (based on refrigeration technology) are used to extract water from humid air found inside homes and offices, delivering up to 60 gallons of water per day.

While the technology has been proven at small scale, there is scope to explore mega-scale versions of the technology using precedents developed in the power industry and marine transportation sector. The early steam ships carried onboard condensers that were cooled by surface seawater to condense engine exhaust steam back into water that could then be pumped under pressure into the boilers. Large-scale condensing technology is also well-proven in coal-fired power stations.

Cooling Towers

During the 1980s, research at Stellenbosch University near Cape Town, South Africa focused on the development and construction of the largest air-cooled cooling towers for coal-fired thermal power stations. The research of Professor Kroger also focused on the possibility of using concentrated reflected solar thermal energy to heat the upper levels of the super-sized towers, to generate a powerful updraft that would pull air through a circular array of wind turbines around the base of the tower.

Further research would focus on replacing the wind turbines with large radiators that would be cooled by cold seawater. After passing through an outer array of cold radiators that remove humidity from air, the drier air would pass through an inner array of radiators at the same elevation, that are heated indirectly using solar thermal energy. The warmer and drier air would them flow into the solar heated tower. Installing an air turbine at the tower outlet would represent an alternative to a solar heated tower.

Further research would establish the daily volume of potentially potable water that the installation would produce and also determine the cost-competitiveness of mega-scale water-from-air extraction compared to carrying potable water by tanker ship from very distant locations, like the Antarctic region.

Precedents

There are precedents from coastal cities such as Sydney, Australia and Toronto, Canada where cold water from great depth sustains district cooling of buildings during hot summer months. Using cold seawater reduces electrical consumption required to sustain operation of roof-mounted, air-cooled air conditioners in groups of large buildings. While Toronto pulls in cold water from near the bottom of Lake Ontario, Sydney pulls in cold seawater from great depth in the Tasman Sea. There is scope to adapt the proven approach at other coastal locations where cold deep seawater is available near a coastline.

There is over 100 miles of coastline extending southeast from the City of Muscat, Oman that is within close proximity to the region of deep seawater in the Gulf of Oman. While there are several beaches and camping grounds along that coastline, there may be some vacant land where the construction of large towers could be possible. The deep seawater at over 6,000 feet of depth is much closer to the coast of southeast Oman than to the coasts of Pakistan or Iran.  

Persian Gulf water temperature would be too warm to operate large-scale water-from-air technology. Over the long term, Gulf states will need to look elsewhere for potable water and might consider future discussions with the government of Oman about operating large-scale water-from-air installations during the summer. It may be possible for potable water from large-scale water-from-air technology to be cost competitive with water imported from far distant locations.

Conclusions

The Gulf States need competitively-priced potable water for their populations. While desalination has been the main source of water, some Gulf States have considered importing tanker ship loads of potable water from far outside of the region. The combination of abundant cold seawater near Oman, intense summer humidity in the region and mega-scale tower technology offers the possibility of large-scale extraction of water from humid air. While the concept is technically possible, future research would be able to determine its long-term feasibility and the volume of potable water each installation would produce.

The close geographic proximity between Oman and the Gulf States of Abu Dhabi, Dubai and Sharjah allows for short-sea shipping of water, should the Government of Oman allow for construction of mega-scale water-from-air extraction on their territory. In some Middle Eastern regions, the cost of potable water often exceeds the cost of the identical volume of gasoline. The region seems committed to making greater future use of renewable energy, allowing for the combination of solar thermal energy and cold deep seawater to produce potable water for human consumption across the region.