Turbines submerged in water (Part 2)

In part one we have covered the turbines, that have found their place in rivers. Now, I would like to talk a bit more about the turbines ”rolling” in the oceans and seas. As you probably already noticed, we as human beings are uncontrollably driven to solve problems (new inventions, improvement of old ideas etc.). We could say, that we have found a way to get the energy out of (almost) everything the Earth has to offer. Actually, it was just a question of time, before someone will come up with an idea on how to obtain the energy from seas and oceans since they have so much to offer (waves, currents, tides, etc.). It turns out, people have been playing with these ideas for quite some time now and they have come up with very diverse and remarkable innovations. These innovations are always designed in a way, to perform as best as possible in the conditions for which they are built for.

Related articles:

Impact of the hydropower on the environment 

The construction of hydropower plants 

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However, as I said, in this article I will only cover the technology, that helps us to obtain the free-flowing energy from the seas and oceans with the help of turbines. The ideas behind the turbines are very easy to understand. There are blades, which are attached to a rotor. The rotor is moving along the stator and during this movement, the magic happens. Now… let’s go see the magic actually happens.


Ocean currents


We refer to ocean currents as continuous movements of seawater, driven by many factors (tides, differences in salinity, temperature etc.). These movements of water are more or less horizontal (except for the ”short” distances of rising or lowering the level of the current due to the water temperature). We call this complex net of currents The ocean conveyor belt. The ocean conveyor belt plays many important roles and has the power to influence the climate as well as many natural processes happening both on land and ocean.

The current, where most of the try-outs are going on is the Gulf stream. The reason behind this is, that it is one of the strongest streams, which happens to also be steady and close to the surface. Steady current is very important and allows us to better calculate the amount of energy that could potentially be produced. Another good thing about the steadiness is the fact, that we know exactly what kind of conditions the structure needs to be able to withstand. The fact that the stream is flowing close to the surface makes the construction (that can be something like this) a lot easier (then it would be in deep water) and therefore more likely to occur.


Why is warmer water located closer to the ocean or sea surface?

The reason behind this is in physical characteristics of the water molecules. They get excited, when the heat is present (sun, underwater volcano eruptions etc.), which makes them move faster and start bumping into one another. Because of this action, they tend to have larger spaces between them and the density of water molecules decreases. The exact opposite is true when the source of heat is absent. In this case, the water molecules are quite lazy and only make small and very slow movements. Because of this, the density increases making the cold water flow deeper.


However, the ideas for the construction of current power plants began to pop up around 2012, and there have already been some turbines put to test. At my latest research, however, I didn’t stumble across an actual operating under-water current farm.

currents


Tidal power


The first power plant harnessing the energy from tidal power was built in the UK in 2003. Today, the biggest one is located in South Korea and is capable of producing 254.000 kW of energy. This type of power plants is very predictable since the amount of water inflow and outflow highly depends on the lunar cycles. This makes them very predictable (we know exactly how much energy we can expect to get at a specific period of the cycle) but nevertheless, it is impossible to only use this method for generation of all the needed energy.


The romance between water and the moon

All the objects in the universe have some gravity and they influence one another by the gravitational pull. This is exactly what is happening between our planet and the moon. The moon is actually a very small object in the universe (and so is the Earth) meaning, that their gravitational pull is not very strong, but is still present. More or less, the moon only has enough power, to influence the water levels a bit and its pull is highly dependent of its position to the sun (I hope you checked the scheme I linked before).

tidal-power


There are different ways of harnessing the tidal energy, some more and others less environmentally friendly. The more environmentally friendly way are these floating turbines, that stay in place and obtain the energy when tides come and go. The problem here is, that a lot of energy goes to waste since it doesn’t pass the turbines. The other way to obtain the energy from tides is to build the wall (not the great wall and also not a tremendous wall, but just a wall, which would still be quite expensive). The wall would act as a barrier, forcing the water to enter the area behind it, through one of the installed turbines (and in the meantime generate the energy). When the tide would back up, the water would be again pushed through the installed turbines and again produce some energy. The biggest problems from the human point of view are the facts, that this area can’t be used for anything else and the accumulation of the sediment on the side of the wall closer to the coast. Removing the sediment is very costly which makes the whole power plant expensive to operate.


Wave power


This idea of obtaining the energy is (at least from my point of view) the most common from all of the ways we obtain the energy with the help of saltwater bodies. The first option I would like to present is the power plant located completely onshore. The electricity is being generated by the movement of the waves. The chamber where this is happening has only so much space and so the air needs to flow in and out when the waves come or go (rising and falling of the water level). The easiest way to obtain the energy offshore is to simply construct the turbines and connect them to the electrical grid with underwater cables.


How do waves form?

It all starts with the sun, heating the Earth’s surface. Of course, the whole surface can’t be equally warm and since everything in nature wants to be in a balance, it tries it’s best to do so. It came up with a brilliant idea – to heat the air above its surface. By doing this, the density of the air changes and leads to the occurrence of the wind. While the winds are doing their thing, they also travel across the bodies of water (such as oceans, seas, and lakes), forming the waves along the way.   


waves

Wave power is usually quite stable and easy to predict since the global winds and currents are moving in the same way. This is why we have some places in the world, that are known to have huge waves (most of them are on the west coasts), and in other places, we can only see really small waves (that are sometimes hard to even be called that). The power plant that currently produces the most energy is located in Sweden and is capable of producing 10 mW of power. However, there is a lot of research being done, which will probably lead to new wave power plants soon.

Do you know of any other ideas of obtaining the energy with the help of turbines from seas and oceans? Do you happen to live close by to one of them and would like to share your observations and experience? If so, please leave me a comment below.

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