On-demand water desalination?

From Science Daily:

Scientists report that they have developed a method for harnessing light to generate electricity from water.  This method, they say, could possibly be used to manufacture a device that would desalinate seawater by exposing it to sunlight.

There are a lot of things we don’t know about this new discovery.  It is often difficult to move from basic research to final commercial feasibility.  At this point, it is impossible to know how costly it would be for this technology to produce large amounts of potable water.  However, if (have I already said this is a big if?) the technology pans out, it could address what has been an oft-raised objection to traditional desalination methods: that they require enormous capital expenditures on large-scale desalination facilities.

Traditional desalination facilities are large affairs, costing hundreds of millions of dollars to build and tens of millions of dollars to operate.  Demand for them tends to go up during water shortages, which is when they tend to get built, to provide supplemental sources of water.  But then, when the shortage passes, they stand idle, and many see them as a big boondoggle.

This issue was raised in a recent panel discussion of desalination at University of California, Irvine.  There, Professor Newsha Ajami of Stanford objected to desalination by pointing out the experience of the city of Santa Barbara in the 1980’s in building an expensive desalination plan in the midst of a drought.  Said Ajami:

Why pay higher prices for desalinated water on a permanent basis if it’s only needed during the occasional drought?

I would argue that there is no reason why the desalination plant would  necessarily have to go idle after the drought passes.  Even if it is not needed immediately, water could be produced and stored, perhaps by injecting it into groundwater aquifers.

The new technology may not address other objections raised to desalination, such as the production of large amounts of salt as a waste product, and the local environmental impacts on local marine life.  But at least Ajami’s objection could be countered if water could be desalinated on demand, as the new technology promises.  Plus, the new technology would rely on solar energy, which would help address another concern of traditional desalination plants: that they require large amounts of energy.

Again, we may be a long way from commercialization, but this new discovery might be worth pursuing to see if it can be a significant source of low-cost water that takes little fossil fuel energy to produce.

Published by

Mark Kanazawa

I am Wadsworth A. Williams Professor of Economics at Carleton College, Northfield, MN