Seawater Desalination

Elixier of Life

Aqua Claudia, one of ancient Rome’s aqueducts (start of construction under Caligula 38 CE, finished under Claudius 52 CE). In the first century, urban Romans used more water than modern Europeans around the middle of the 20th century: about 1 m³ per human and day!(Source)

Clear, fresh water is the epitome of life. The first advanced civilizations thrived near water-rich rivers or lakes — e.g. cultures of the Fertile Crescent or Egypt. In the Roman Empire, the storage of water through barrages and its transport with long aqueducts to the places where it was needed became common. Little has changed in this respect since then. We take the water from natural sources and precipitation, collect and distribute it. In arid areas, this recipe can fail, as the repeated Californian draughts show. We can no longer count on the natural water cycle delivering what we need: We should start to artificially create fresh water on a grand scale.

Water per se is not rare on our planet, which has been dubbed, not accidentally, “blue Planet”. 75% of earth’s surface are covered by oceans. Sewater is too salty for humans and most land-based lifeforms, though. Technology can help here.

Nuclear desalination plant Shevchenko in the Soviet Union (now called Aqtau). Energy source is the fast breeder reactor BN 350.

Modern desalination plants usually rely on fossil burning, such as the world’s largest unit Jebel Ali in the United Arab Emirates. Nuclear desalination has been done experimentally: The fast reactor BN_350 in Kazakhstan produced 80.000 m³ of potable water daily for 27 years, as well as 135 MW of electricity.

The DFR is especially suitable for this application. Thanks to the high operating temperature, no energy needs to be re-routed from electricity production: Turbine waste heat at 250 °C is perfectly fine. A 1500-MW-DFR, generating electricity at 60% thermal efficiency, can use the remaining 40% to pump out 7 cubic meters of potable water per second using multi-stage flash distillation, corresponding to 580.000 m³ per day, similar to a smaller river. Several DFR desalination units can be combined to create artificial streams of respectable size, which may be routed into desert regions to green these and open them up for agriculture — massive increases in food availability would result, most of all in Africa.

Mountain ranges between sea and desert need not be an obstacle here: The energy needed to pump water over gradients can be delivered by a DFR. Per liter, meter of elevation gain and second, 10 Joule are needed, or 70 MW of power to raise 7 cubic meters each second over 1000 meters — small task for a 1500 MW DFR unit.

Fresh water can be seen like pure aluminum, which used to be a rare substance on earth but has become common through human industrial processes. The Russian scientist and philosopher Vladimir Vernadsky called this principle Noosphere (sphere of thought): Human action work as a geological force creating substances and structures unknown on earth beforehand.