Oral dal

The document I'm going to talk about is composed by a diagram showing all the oscillating water column system and a text untitled « using wave power to generate electricity ». It's taken from several physics website. As its name suggests, they both talk about how the power of waves can be used to generate electricity. So, first, i'll present and coment on the documents while i'm focusing on the differents types of energies involved in the oscillating water column process and the conversion between them. And in a second part, I will try answer the following question : what do you think of this method to generate electricity and why is it necessary to develop renewable energies.

The first part of the text raises a short introduction about the electricity generation. Today, thanks to stucture like the OWC or others, we can convert the wave power into electricity. Of the coast, when the wind blows, it presses the still quiet sea. We observe then a light shiver on the surface of the water, only some wrinkles. If the conditions are adapted, these are going to expand little by little, to be transformed into swell and to propagate towards coast. When the swell approaches them, the depth of the water decreases. The profile of the swell bends more and more. Waves rise, fall over forwards and eventually unfurl.

The second part of the document explain how the OWC works. The principle is relatively simple: the swell makes increase the height of water in a concrete column fixed to the bank. This sudden rise of water is going to reduce the volume of the cavity and thus to compress the air which is situated inside. This air will have no choice but to be evacuated under pressure at the top of column through a turbine reversed forecast in a generator. The turbine will be put in rotation by the compressed airflow. Once the maximal amplitude of the wave reached, this one gets down again and causes an in-draft in the column. This time this, the air come in the column with strength in the other way and made turn again the turbine. It produces some electricity. Regardless of the airflow direction, the turbine will turn ensuring a constant production of electricity.

During all the process, 4 types of energy are involved. The first one is the hydraulic energy produced by the swell.  Then, when the water get into the column, the trapped air is compressed and so it stores pneumatic energy which is converted into mechanical energy through the turbines. Eventually, a generator changes this one into electricity.

The last paragraph of the text deals with the share of this type of hydro-electricity worldwide. In fact, the hydraulic energy produced by wave power could be the only source of electricity production but today, the share of its type of energy is just 3% of the worldwide energy and the sixth source of electric production after crude oil, carbon, gas, nuclear, and biomass. So, it's the 1st renewable source of energy in the world.

Now, I'm going to answer the question : what do you think of this method to generate electricity and why is it necessary to develop renewable energies ?

In my opinion, this method is a very good thing for the future. On the one hand, it's a renewable energy, it's safe for the environment without any impact for the global warming. It can also be useful for isolated islands. But on the other hand, this method is very expensive and has not a good yielding : it needs a very large area of machines for a very small energy return. Moreover, it creates visual pollution.

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