Sources of renewable energy can be found in unexpected places, and one of the less well-known processes currently being researched is the generation of osmotic power, or salinity gradient power.

This describes the energy available from the difference in salt concentration between two bodies of water, for example a river and an ocean. The world's first osmotic power plant was opened in Tofte, Norway in 2009.

Osmotic power is explained in this week’s 'How It Works' animation.

earthrise airs each week at the following times GMT: Friday: 1930; Saturday: 1430; Sunday: 0430; Monday: 0830.

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Source: Al Jazeera