# Magnets/ Magnetic fields energy storage?

1. Jul 25, 2012

### Momento

Very strong magnets like neodymium can create a very powerful force! I wonder the amount of energy supplied when there created to be magnetized, in a sense don't they store energy and it is converted"demagnetized" over time?

It came from the electricity used to create that magnetic field! Its really interesting to me honestly! Magnets are like natural capacitors for me that release a strong force! And discharged "demagnetized" over time! Even supercooled it takes a longer time!

What do you all think?!

2. Jul 25, 2012

### Staff: Mentor

3. Jul 25, 2012

### Momento

4. Jul 25, 2012

### phyzguy

Try calculating the total energy stored in the magnetic field of a permanent magnet and comparing it to, say, the energy released if I drop the magnet on to the floor from a height of 1 meter. I think you'll find that they really don't store very much energy.

5. Jul 25, 2012

### M Quack

I do not know of any way to extrqct the energy stored in the magnetic field of permanent magnets like NdFeB.

There have, however, been attempts to store energy in the magnetic field generated by superconducting magnets. Electromagnets need currents flowing. If the conductor has a non-zero resistance, then the stored energy will quickly be converted into heat.

A superconductor has no electrical resistance. On the other hand it needs to be kept cold (very cold) and that is not free. Also, superconductors do not like it if you change the field too quickly.

http://en.wikipedia.org/wiki/Superconducting_magnetic_energy_storage

Once you get to a field volume of 1 cubic meter times 8 teslas the amount of stored energy becomes noticable.

6. Jul 25, 2012

### CWatters

Best not think of it like that.

A planet can also create quite a strong force but gravity doesn't "wear out" or become "used up" just because objects fall on it.

Likewise a magnet isn't used up when it's put to work, for example, in a motor.

7. Jul 25, 2012

### Staff: Mentor

While their primary goal is different: The LHC magnets store up to ~3GJ (~800kWh) during operation, with 11GJ as design value.

This is really tricky to achieve.

8. Jul 26, 2012

### M Quack

9. Jul 26, 2012

### CWatters

The problem is that a lot of people (especially so called "free energy" believers) think that magnets are an energy source/store and that this somehow explains how fridge magnets stay up. That's totally wrong.

10. Jul 26, 2012

### M Quack

A good nuclear power station puts out over a GW. So even if you store 11 GJ in huge magnets like at LHC that can only replace a single nuclear plant for a few seconds.

11. Jul 27, 2012

### Khashishi

Inductors store energy in a magnetic field when current is passed through them. The stored energy increases with current squared. They aren't very practical for energy storage, because energy lost to internal resistance also increases with current squared, so any stored energy is quickly lost, unless you are using some kind of superconducting coils, like the EAST tokamak.