Scientists make electricity from tap water

Courtesy of J’s Notes, it seems as if a Canadian research team has created a way to make electricity by moving water through a “microscopic channel,” providing a source of clean energy that could power small electronic devices:

The key to the phenomenon is the way that charges naturally separate at the interface between the surface of a channel and a fluid. Scientists believe that this occurs because minute parts of the solid of one charge (either positive or negative) dissolve into the water. As a result, the surface becomes charged.

Opposite-charged ions (charged atoms) in the liquid are attracted to it, while like-charged ions are repelled, resulting in a thin liquid layer with a net charge, called the Electric Double Layer, measuring a few billionths to a few millionths of a metre across.

The team constructed a channel with a diameter similar to the distance across the layer and forced liquid through this channel. When a fluid, such as water which naturally contains an equal number of oppositely charged ions, is forced down the channel, a charge separation occurs.

The ions that have a charge opposite to the solid are preferentially attracted into the channel (remembering that opposite charges attract each other) and transported to the far end. The ions of the same charge as the solid are preferentially left behind at the inlet side of the channel.

Therefore, the liquid at the two ends of the channel have opposite charges. This produces a voltage difference. If conducting electrodes are placed at the two ends of the channel and connected by a wire, then current flows and electricity is produced.