Origin of renewable energy sources [ctd.]

1.4 Tidal power

If you live in a coastal area or if you have ever been to a beach, you might have realized that the ocean is a massive reservoir of water with an unimaginable capacity!

The ocean is a really playful place.

Even though the deep sea looks like a calm place the ocean turns to be a wildly overwrought tiger in some locations especially, in the shallow areas.

It interacts with the wind, the Sun and the Lunar leading to different types of disturbances in the sea level and morphology of the ocean.

As we discussed in the previous article, the interaction between the ocean and wind results in ocean currents and waves. In this article, we will discuss another form of ocean energy: Tides!

Tides are formed as a result of the gravitational interaction between the earth and moon. Of cause…. The gravitational interaction between earth and the Sun also causes tides but not as powerful as the tides that caused by the Lunar (Since we are far away from the Sun).

As we all know it, the moon revolves about the earth. Water in the oceans is pulled by the moon’s gravity when moon located just above the ocean. As a result, high tides occur on two sides of the earth simultaneously as shown in above figure. Low tides occur as a compensation, on another two opposite sides at the same time as shown in the same figure. The rise and fall of the sea level that occur twice a day are called tides.

Unlike other forms of ocean energy, tides represent neither direct solar energy nor indirect solar energy. Anyway, tidal power is also a renewable source of energy since tides are continually being replenished naturally. In other words, like all other renewable energy sources, tidal power would never be exhausted.

As long as the earth and noon exist tides would flood onto the shore and recede!

General background

Tidal power has a well-matured technology with a long history compared to any other form of ocean energy. Some countries have already built tidal power barrages to generate electricity.

The first tidal barrage was born in Germany in 1912. However, it was damaged in World War I, unfortunately [1]. One of the famous and oldest tidal barrage built as early as 1966 at La Rance in France is still generating electricity with a power capacity of 240 MW [1, 2]. So it gives an exciting example of a successful tidal barrage built 5 decades ago.

Worldwide tidal power potential has been estimated at 3 TW. Obviously, we can’t install the tidal power devices everywhere since tidal power is highly site-specific. Simply, there are some technological and practical limitations in tidal energy harvesting. Only a few areas in the ocean are technologically and economically viable. Some areas are technologically suitable but are economically impracticable. These technological and economic challenges largely limit the amount of energy that could be harnessed from tides. It has been estimated that less than 3% of the global tidal power capacity is suitable for power generation [2, 3].

It is equal to 90 GW of power!

Some important facts about tidal power

• Tidal power has already become commercially viable and is already being used to generate electricity in commercial scale (France, South Korea, Canada, etc.) [1, 4].
• Several countries are planning to build tidal barrages in near future (the UK, South Korea, Russia, Canada, etc.)
• Garolim tidal power station in South Korea would have a capacity of 500 MW once completed.
• Although worldwide tidal power capacity is 3 TW, the maximum power that could be harnessed would not exceed 90 GW due to technological, environmental, social and economic limitations.

Remark: Global energy demand was around 17.5 TW in 2010 and it would reach 63 TW by next century (2100) according to the recent estimations [5].

• 1 TW= 1000 GW
• 90 GW 5 % of current global energy demand. 

So, what can we conclude?

Tidal power is a renewable energy source. It releases no harmful emission to the environment and therefore, does not intensify the climate change or global warming. However, the practically viable power capacity from tidal power is extremely limited compared to the current global energy demand.

[5] Hu, A., Levis, S., Meehl, G. A., Han, W., Washington, W. M., Oleson, K. W., and Strand, W. G. (2016). Impact of solar panels on global climate. Nature Climate Change, 6 (3), 290-294.