The Desalination Solution
THOUGH FRESH WATER SOURCES ARE NON-RENEWABLE AND RAPIDLY DWINDLING, UNDERGROUND SALINE AND OCEANIC WATERS (IMPAIRED SOURCES) ARE VAST, RENEWABLE AND VIRTUALLY LIMITLESS.
Desalination is therefore the most viable solution to our developing global water crisis. To transform impaired waters into fresh, modern desalination technologies use a handful of energy-greedy processes which are ultimately dependent on the combustion of fossil fuels (extreme hydraulic pressures, massive heat sources or extreme electrical currents). Operating efficiencies and costs are impractical and the high energy needs tether these technologies to pre-existing energy and water distribution utility infrastructures via centralized water production models. Neither the developed nor the developing world can afford this kind of water production, yet the fact that new desalination plants are beginning to come on line here in the US is testimony to our desperation.
Poor desalination efficiencies are a chronic, pan-technology problem. Even accounting for expensive energy recovery systems, and specialized siting appropriate for only a small fraction of users, operating efficiencies are still too far from the thermodynamically defined minimum amount of energy needed to separate salt from water (thermodynamic limits) for desalination to be cost-effective. The result is non-adoption by all but the wealthiest and most desperate.
Sensing the potential of desalination to avert our present course towards a global water crisis, but fully aware of current systems’ shortcomings and inefficiencies, the US Department of the Interior has called for dramatic energy-efficiency improvements through the increased academic and industry support of alternative desalination technology development. This was a decade ago, yet most of the innovations since then represent incremental improvements to the existing methods. Operating efficiencies have barely improved, and given the time and money spent over the past several decades, it must be concluded that present-day methods are fundamentally constrained from approaching the thermodynamic limits any further. We seem to be stuck at a severe technology innovation bottleneck imposed by our traditional view of the problem.
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