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Offshore towage of water in huge fabric bags is a proven technology.

It is currently in operation in the Mediterranean, with water being towed from Turkey to Greek Islands in fabric ‘bags’ with a conveyance capacity up to 30,000 T. (for more background information please click here.)

The bags have relatively low towage speed in the water due to relatively poor streamlining. As a consequence, this form of conveyance would be too costly in case of long towage distances.

Note: this also applies to traditional methods of water conveyance by means of a canal, pipeline or supertankers due to the fact that frictional flow resistance and associated energy cost per KL would be too high.

Drawing on more than forty years experience in ocean engineering and by application of fundamental fluid mechanics principles, Marecon managed to greatly reduce the towage resistance of the bags (hereafter called ‘containers’).

This has been accomplished by various technical innovations and by minimization of the so-called form drag through optimized ‘fishtailing’ of the container profile at both ends as shown below:

schematic drawing of Watertow container

By applying a special method (*) of compacting the emptied containers, the towage vessel’s return voyage to the ‘upstream’ single point mooring can be undertaken at high speed, close to the vessel’s hull speed limit. This minimizes return trip time and maximizes the total volume of water that can be conveyed per towage assembly per year.  (*) patents pending

By applying an industrial fabric stronger than steel it is now possible to fabricate containers as large as supertankers. This greatly reduces transportation cost per KL.

As a consequence it is now realistically possible to convey water over long distances, well in excess of 2000 km, in a reliable manner and at highly competitive cost.

The WATERTOW containers are to be fabricated in Australia by one of the world’s largest manufacturers of high-strength industrial fabrics. The containers are towed by tugs or towboats operated by a reputable Australian towage company.

The connecting towline is relatively short as shown below:

This enables the assembly to change direction over a short distance as required to negotiate narrow fairways or bends in estuary channels.  However, it necessitates the use of a high-stretch tow rope in combination with specially designed (*) elongation provisions on the towage vessel in order to reduce the peak force in the towline during severe wave action. (*) patent pending

Water is pumped into and from a container by means of proven Single Point Mooring (SPM) technology as commonly used for the filling and discharging of supertankers in the oil industry. The system incorporates flexible hoses and an operational control vessel which is permanently moored at the SPM buoy as shown below:

               

Towage vessel, generators and pumps are all powered by bio-diesel, a carbon neutral fuel derived from 'dry soil' crops unsuitable for human consumption.

This implies that the WATERTOW technology is eco-friendly, without any biological or climatic disadvantages.

Capital cost of implementation per KL of conveyed water is relatively low, amounting to less than half the cost of alternative water supply technologies such as recycling of waste water or desalination of seawater.

The WATERTOW system can respond quickly to changes in water demand by the deployment of additional towage assemblies or, conversely, by reducing the number of operational units during periods of higher than average.