Our Moon does more on the earth than shine a light in the night sky. Our Moon also is the main cause of us having tides. The same force that makes sure apples fall down also pulls the water in our oceans up a little towards the Moon (and Sun to a lesser extent). This force is called gravity. When the water in the sea is pulled upwards it is called high tide. If you’ve been to the beach it is when there isn’t much beach left to play on. When the Moon pulls the water up elsewhere on the earth we see the water drain away creating a low tide. That’s when the beach looks big because the water’s edge is far away. The height difference between low tide and high tide depends also on the geography. It can be as high as 16m and as low as 1m in the middle of the ocean.
We can make use of this huge quantity of sea water moving in and out repeatedly every twelve hours by constructing a barrage (barrier) and putting turbines inside large tubes connecting each side of the barrier. As the water flows between low and high tides (and back) the turbines rotate and we can generate electricity. Another way is to place large tidal turbines on the sea bed where there are naturally large tidal currents. These can occur between islands and in the straights between different seas.
A tidal power station (Rance) has been operating in France since 1966.
Tidal power can create large dependable quantities of electricity. The MayGen tidal power scheme in the Pentland Firth in northern Scotland is under construction and when completed could generate enough to power one hundred and seventy five thousand homes (see below).
We have to be careful when constructing tidal schemes to look after the fish, animals and plants that live in and by the sea. Large barrages can be expensive and could affect the local wildlife. We always need to consider the local habitats and environment when we plan big projects like this.
Living Laudato Si' 