Can we extract energy out of a capacitor in the ocean?

• maial
In summary, this system tries to extract energy from waves through the use of a capacitor. However, salty water between the capacitor plates makes the system inefficiency.
maial
Hello, sorry about my english it's not my mother tongue. I hope this is the right section to place this.

1. Homework Statement

A cylindrical capacitor is placed in the sea so that when a wave comes (the water goes up), the water becomes the capacitors dielectric, when the wave has passed (the water goes down) the air becomes the dielectric.
So now when the water is at its highest, i attach a battery to the capacitor.

When the water goes down i detach the capacitor from the battery, this creates an isolated system in which the charge remains constant and can change the potential difference between the capacitors plates.

The force of gravity makes the water that was between the capacitors plates go down, and so it reduces the capacitors capacitance. The dielectric constant of water is quite high (about 81) and the change of capacitance is also quite high.

The charge remained the same but the potential difference between the capacitors plates has increased.
This means that the energy in the system has increased.
So i found a way to harvest energy from the waves movement without moving bodies... but...

1) Explain why this system in practice can not really work.
2) Think about how to make it work (even if with reduced performance).

The Attempt at a Solution

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I think this does not work because sea water is salty which means it conducts current. So now there's a current flowing through the capacitors plates which i think would damage the capacitor itself.
Actually when i attach the battery to the capacitor with water inside it makes a short circuit?

Honestly I'm not sure what happens when there's salty water in between the plates...

To make it work i think one would need to put distilled water in the capacitor or another insulating material and make it go up and down the capacitor thanks to the waves movement.

What do you think?

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You can isolate the plates to avoid contact to sea water (good to avoid corrosion as well).
How do you keep the capacitor at the same height?

You can also estimate the power you can get out of such a device.

maial said:
1) Explain why this system in practice can not really work.

maial said:
The charge remained the same

maial said:
The charge remained the same
Tom.G said:
The charge is supposed to remain the same. If you reduce the capacity of a disconnected capacitor by removing the dielectric the voltage of the capacitor and also the energy will go up, while the charge remains the same. The energy from this comes from the potential energy of the water.

I have a couple of questions which you should ask yourself.

1. Are there any forces on the cylinder of water caused by the electric field in the capacitor? (i.e., besides the force of gravity. Remember, the water is a dielectric.) If so, what effect are these forces going to have on the column of water?

2. I was going to ask about the inefficiency losses ($I^2R$ losses) of directly connecting a battery to the capacitor as described, but let's ignore that for now. One thing at a time. Concentrate on 1. for now. Perhaps we can come back to 2. later.

1. How can we extract energy out of a capacitor in the ocean?

The process of extracting energy out of a capacitor in the ocean involves utilizing the principle of electromagnetic induction. This involves using a coil of wire, known as an inductor, to create a changing magnetic field around the capacitor. As the magnetic field changes, it induces a current in the inductor, which can then be used to power devices or be stored in a battery.

2. What type of capacitors can be used for extracting energy in the ocean?

Capacitors used for extracting energy in the ocean need to be specifically designed for this purpose. These capacitors are typically made of materials that can withstand the harsh conditions of the ocean, such as corrosion-resistant metals and robust insulators. They also need to have a large capacitance and low leakage current to be able to store and release a significant amount of energy.

3. Is it possible to extract a significant amount of energy from a capacitor in the ocean?

The amount of energy that can be extracted from a capacitor in the ocean depends on various factors, such as the size and design of the capacitor, the strength of the ocean currents, and the efficiency of the extraction process. While it may not be possible to extract a large amount of energy, it can still be a valuable source of renewable energy, especially in areas with strong ocean currents.

4. What are the potential benefits of using capacitors in the ocean for energy extraction?

Using capacitors in the ocean for energy extraction has several potential benefits. It can provide a source of clean and renewable energy, reduce the dependence on fossil fuels, and decrease carbon emissions. It can also be a cost-effective solution, as the energy extracted from the ocean currents is essentially free and does not require any fuel or maintenance costs.

5. Are there any potential drawbacks to using capacitors in the ocean for energy extraction?

While using capacitors in the ocean for energy extraction has many benefits, there are also some potential drawbacks to consider. One of the main concerns is the environmental impact, as the installation and maintenance of these systems may disrupt marine life and habitats. There may also be challenges with the storage and transmission of the extracted energy, as well as the initial investment and maintenance costs of the equipment.

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