Remote Irrigation over Very Long Distances
The concept is based on an extension of the natural principles that generate rainfall, and as such enables water to be moved over long distances with a minimum of effort and cost. The purpose is to reverse the effects of desertification, and make more arable land available for food generation and poverty reduction.
The extraction of salt from seawater by evaporation has been practised for centuries, and now the other aspect of the same separation process is being exploited to generate potable water from seawater, either by using locally provided energy, or by using a combination of solar power and waste energy from other industrial processes.
The remote irrigation concept relies on the evaporation of seawater, but collects the evaporated water, and channels it as water vapour. Higher vapour-carrying capacities can be achieved by raising the temperature of the air, which is the transport medium – air at 38C, for example, carries nine times more water than air at 5C.
High-humidity hot air is ducted from the collection point to the point of use, which could be many miles away, by special tubing, probably of plastic material, that is designed to heat the air inside it to the highest possible temperature during the day, under the influence of sunlight.
It is known that daily temperature variations in desert areas can be extreme, with night-time temperatures falling to below the freezing point of water. This would prove to be no difficulty, for even if ice were to be formed within the tube during the night, it would quickly melt and evaporate again the next morning, returning the air inside the tube to full humidity again.
The high-humidity hot air is propelled along the tube during the day by fans inside the tube itself. The fans are solar-powered, which requires either the provision of Photovoltaic Cells as the source of electricity, or fans which use the Stirling principle, and make direct use of the temperature differentials that can be generated by using simple concentrators. If Stirling principles are used, the humid air within the transport tube would be used for ‘cooling’.
Apart from leaks which may be present in the joints of the duct tube, the humid air could be expected to arrive at its destination with the same load of water vapour as when it left the evaporation site at the coast. The only requirement then is to condense it out of the transport medium. Here again, Stirling motor principles can be applied, and the humid air cooled to discharge its load of water. Alternatively, electrically driven condensers using power from photovoltaic cells would perform the same function.
Note that delivery of water to the remote site would only be expected during the day, when a reasonably high level of humidity could be obtained. However, apart from the initial capital investment, and installation, nothing must be carried, and the transportation requires no fuel input other than sunlight. Running and operating costs are therefore practically zero, and with correct design, only occasional maintenance will be required.
As far as I am aware, this concept is unique, and is hereby donated to the Public Domain. It may not be patented, claimed as Intellectual Property by any other individual or company, or the world otherwise deprived of it’s possible benefits, with the exception of allowable patents etc. on system components that may be designed and supplied by companies providing installations.
2nd. May, 2001.