Can we turn water into power?

Hydroelectricity is one of the world's oldest, and most renewable, sources of energy. And though the development of hydropower is limited by geography, advances in hydroelectric technology continue to be made.

It all started during Antiquity with norias, wheel-like machines fitted with buckets or winglets that used the natural flow of river currents in order to divert water away for irrigation. Ancient ancestors to the watermill, the noria was first referenced some 2200 years ago in the eastern Mediterranean Basin, and also in ancient China. The mechanisms were further refined during the Early Middle Ages by millers, who used increasingly relied on them to grind grain.

The technology to harness the power of the movement of water—from rivers, marine currents, tides, and even waves—has been refined as energy needs have grown, and has become increasingly efficient. For example, the watermills of the middle ages became the modern micro-hydraulic systems equipped with turbines that generate power from dams.

A major source of global energy

Today, the main means of drawing power from water is via hydroelectricity, which is the world’s first renewable (and storable) energy source, as well as the third most used, behind oil and gas. China, Brazil, and Canada are the three largest hydroelectricity producers, with the US a close fourth. However, some large dams pose ecological threats, as they require large areas to be submerged.

As the world’s foremost renewable energy source, hydroelectricc technology has seen major advances recently, thanks to dramatic increases in fossil energy prices along with the fight against greenhouse gases emissions.  Floating wind turbines (more efficient than land-based ones), water-current turbines (which harness marine currents’ kinetic energy), oscillating water columns able to draw power from waves, and tidal mills are but a few examples of these new technologies.

From large-scale to small

Apart from these, small devices (calculators, clocks, weather stations…) can also run on water via a process akin to reverse electrolysis. To achieve this, two electrodes—one positive, the other negative—are placed in water, which triggers an electrochemical reaction and produces electricity. Engineers have tried to create water-based engines based on this same principle, but unfortunately their efforts have not yet resulted in working prototypes.