Question about magnetohydrodynamics (MHD) for electricity production

  • #1
DavAeroEng
4
1
TL;DR Summary
Is this design theoretically possible for electric energy production? Could be realised to be used to produce electricity?
Picture1.png
Picture2.png


According to the MHD theory, is case of energy production, a magnetic appplying a magnetic field to a moving charge perpendicular to the magnetic field, that could be plasma as well a solution full of ions, and placing two plates, electricity could be produced.
Now I have a question, let's say instead of moving the charges, the magnetic field is moved, in paricular in a circular motion with two ring

magnets
Screenshot 2023-12-26 082619.png
like in the image. Let's say they are ferrite magnets, so the intesity is kinda low respect to neudium magnets. These are made spin very fast, in the same direction. Now in theory by putting the a charge in between, and I though to fire, that is a plasma, and two plates.

Could this design produce a relevant amount of electricity? Could this work?
Screenshot 2023-12-26 082619.png
 
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  • #2
What is your energy source?
 
  • #3
I'm not sure if I understand the concept, but it looks like you want to reproduce a generator - extracting electricity from the motion of the magnet rings? You get a force from a time-dependent magnetic field inducing an electric field, but the field here is time-independent.
 
  • #4
mfb said:
I'm not sure if I understand the concept, but it looks like you want to reproduce a generator - extracting electricity from the motion of the magnet rings? You get a force from a time-dependent magnetic field inducing an electric field, but the field here is time-independent.
Yes exactly, Normally in MHD generators the hot gas is shoot in between the fixed magnetic field, but what if the plasma, in this case fire from the combustion stays in that semi-ring, and the magnets over them spins, could this setup produce electricity? In other words could moving the magnetic field like this produce the necessary lorentz force to produce electricity?
 
  • #5
There is nothing moving here (besides the field source). A moving particles in a magnetic field works: In the reference frame of the magnetic field you have the particle moving, in the reference frame of the particle the field transforms to have an electric field component. But here both reference frames are identical and you only have a non-moving charge in a magnetic field, assuming perfect symmetry in the setup.
 

FAQ: Question about magnetohydrodynamics (MHD) for electricity production

What is Magnetohydrodynamics (MHD) and how does it relate to electricity production?

Magnetohydrodynamics (MHD) is the study of the behavior of electrically conducting fluids, such as plasmas, liquid metals, and saltwater, in the presence of magnetic fields. In the context of electricity production, MHD refers to the process of generating electric power by converting the kinetic and thermal energy of a conducting fluid into electrical energy through the use of magnetic fields.

How does an MHD generator work?

An MHD generator works by passing a conductive fluid (such as ionized gas or plasma) through a magnetic field. As the fluid moves through the magnetic field, it induces an electric current perpendicular to both the fluid flow and the magnetic field. Electrodes positioned within the flow path collect this induced current, which can then be used to generate electricity. The process is based on Faraday's law of electromagnetic induction.

What are the advantages of using MHD for electricity production?

Some advantages of using MHD for electricity production include the absence of moving mechanical parts, which reduces mechanical losses and maintenance requirements. MHD generators can also operate at higher temperatures than conventional turbines, potentially increasing thermal efficiency. Additionally, MHD systems can be used in conjunction with traditional power plants to improve overall efficiency and reduce emissions.

What are the main challenges in implementing MHD technology for electricity production?

The main challenges in implementing MHD technology include the need for high temperatures to ionize the working fluid, which can lead to material and engineering difficulties. Efficiently ionizing and maintaining the conductivity of the fluid can also be challenging. Furthermore, the initial cost of setting up MHD systems can be high, and the technology is still in the experimental or early commercial stages, requiring further research and development.

What are some potential applications of MHD technology beyond electricity production?

Beyond electricity production, MHD technology has potential applications in areas such as propulsion systems for spacecraft and submarines, where the absence of moving parts can be particularly advantageous. It is also used in the study of astrophysical phenomena, such as solar flares and the behavior of the Earth's magnetosphere. Additionally, MHD principles are applied in industrial processes, such as electromagnetic casting and the control of liquid metal flows in metallurgical processes.

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