The possibility of a Casimir Effect Battery

[siromar]

Let me begin by apologizing if this has been brought up before, but it has been on my mind recently, and I had to ask.

Would it be possible to create a battery that can extract work from the casimir effect? I understand that the energy required to separate the plates is greater than the energy generated by the effect, but that seems like a solvable problem.

For an example, a large number of uncharged metal plates are placed within a few nanometers from one another. A bridge is constructed between them to prevent them from actually touching. A crystalline material with piezoelectric capability covers the bridge, and electrons are generated through the pressure applied by the casimir effect on the plates.

Why would this not work?

 

[Q-reeus]

Sorry, but all you have is a completely conservative (and extremely feeble) force of attraction. Through one cycle of in and out nothing can be gained. No more chance of extracting net power than with a pair of magnets. If on the other hand you imagine the static 'squeeze' of the plates on the piezoelectric slabs can continually extract electricity, why not just use a g-clamp? Again, won't work.

 

[siromar]

I don't understand your objections Q-reeus. Doesn't the effect depend, partly, on the distance between the plates? Wouldn't it generate a lot of attraction at very short distances? A g-clamp needs an operator to exert force.

Even if the energy harvested is small, can you explain to me why it isn't possible?

 

[_PJ_]

Essentially, it's inefficient.
The energy is so small, (Based I believe on the linear distance) that to 'convert it into any useful ness, which would require the net energies of forces present across the surface area of both plates.

 

[Q-reeus]

I don't understand your objections Q-reeus. Doesn't the effect depend, partly, on the distance between the plates? Wouldn't it generate a lot of attraction at very short distances? A g-clamp needs an operator to exert force.

Even if the energy harvested is small, can you explain to me why it isn't possible?

Siromar, I can understand your attraction to the concept. There are 'professionals' out there who have made a career out of claiming to be able to utilize 'zero-point energy' (typically via Casimir effect) to generate unlimited power. It has gotten nowhere. Thing is the Casimir force behaves in a conservative manner - meaning it is purely a function of separation distance and not say how fast you move the plates, or which particular path one takes. In that respect it is no different to two permanent magnets (where the force of attraction also varies with displacement). A basic mechanical definition of energy is force x distance (more precisely the integral of the dot product). What one gains in one direction of motion is lost when the reverse motion is performed. Without some cycle involving motion there can be no energy change at all. Thus the static force idea is doomed from the start, even if there were some non-conservative dynamical possibilities (say a force that reversed with direction of motion). So there are two fundamental barriers to success in this case. But keep studying!

 

[siromar]

Let's say we had 2 plates, separated by piezoelectric material at a distance of 10 nm. You do agree that Casimir attraction will generate electrons, correct? However, the energy required to return the plates to the original position will be greater than what was generated, right? So what if there was some mechanism attached to the plates, that snaps them back to their original separation of 10nm once it crosses a certain threshold? Like a rubber band. Can ANY amount of energy be collected? I'm trying to picture what exactly prevents it.

 

[Q-reeus]

Let's say we had 2 plates, separated by piezoelectric material at a distance of 10 nm. You do agree that Casimir attraction will generate electrons, correct? However, the energy required to return the plates to the original position will be greater than what was generated, right?

Correct, since the tiny squeeze of the plates has infinitesimally compressed the piezo slab, in doing so creating an electric field that in turn may be used to draw a brief 'capacitor' type current. This in turn means the piezo slab has now less return 'spring' to return the Casimir plates to their original displacement. The plates are now by a tiny amount 'permanently' closer together.

So what if there was some mechanism attached to the plates, that snaps them back to their original separation of 10nm once it crosses a certain threshold? Like a rubber band.

But the rubber bands would be in the same situation - gain one way of movement, loss the other.

Can ANY amount of energy be collected?

Yes, but unfortunately only in the negative sense. There will always be some losses present (friction, hysteresis etc), meaning waste heat.

I'm trying to picture what exactly prevents it.

You will get from most a short answer - because it violates the conservation of energy principle. I have tried to indicate briefly why that applies here. Sorry, I'm off to bed!

 

[Vanadium 50]

There is a 25-year old paper by Robert Forward about building such a battery using helical plates. As you charge it, the helix untwists, and as you discharge it, it twists. However, apart from bragging rights, it's not so clear what the utility of such a thing is.

 

[alxm]

Why would the Casimir effect be better for this than it's more common, easily-utilized and stronger cousin, the London force?

Of course, we're already utilizing energy stored the latter way in every machine that's powered by a liquid CO2 canister. It's not a particularly good or convenient way to store energy, though. Anyone who's studied some chemistry also knows that London forces are extremely tiny compared to the scale of chemical reaction energies. So it would never be a good way to store energy.

In either case you do not, of course, get out any more energy than you put in. The Casimir effect does not allow you to build a perpetuum mobile more than anything else.
(Except in the sense that the Casimir effect may be calculated with perturbation theory, where it's relatively easy to violate conservation of energy by making a mathematical mistake)

 

[Q-reeus]

Do a search using say 'ZPE + energy extraction' and Casimir force comes up nearly every time. Energy creation, not storage, is the name of the game. It's an 'industry' - and that most likely is what attracted the OP's interest. Unaware of a single instance where London force comes up in that same context, maybe because it is treated as stemming from local, inter-atomic interactions, as opposed to the ostensibly more mysterious 'vacuum fields'.

 

[DrZoidberg]

There is a professor in Germany who claims he found a way to extract energy from vacuum fluctuations using the fact that photons travel more slowly in an electric field which means photons "fluctuating into existence" should have a longer wavelength and therefore less energy inside such a field.
He did an experiment to prove his theory
http://philica.com/display_article.php?article_id=155

However it has not been verified and may contain errors.
Also the energy extracted was very small. So even if it does work it is not practical.

 

[Q-reeus]

There is a professor in Germany who claims he found a way to extract energy from vacuum fluctuations using the fact that photons travel more slowly in an electric field which means photons "fluctuating into existence" should have a longer wavelength and therefore less energy inside such a field.

For starters the claim that an E field slows photons sounds dubious, but assuming so, shouldn't the relation be the opposite - a shorter wavelength? At least that's what lambda = c/f for a monochromatic wave of frequency f requires, c being the speed of light in the medium (in this case vacuum 'modified' by the presence of an applied E). This is somehow inverted for ZPF fluctuations?!

He did an experiment to prove his theory
http://philica.com/display_article.php?article_id=155
However it has not been verified and may contain errors.
Also the energy extracted was very small. So even if it does work it is not practical.

Surprised to see the design is one of a floating 'turbine' - a solid-state vacuum energy 'battery' arrangement is promoted elsewhere by a different team, also in Germany. The numbers here just don't stack up. He invokes DE (dark energy) = 'true' vacuum energy as power source. From http://en.wikipedia.org/wiki/Vacuum_energy
"Using the upper limit of the cosmological constant, the vacuum energy in a cubic centimeter of free space has been estimated to be 10⁻¹⁵ Joules."
Making the hugely unrealistic assumption that 100% of this DE pressure could somehow be unidirectionally converted into mechanical power, a crude calculation is W_max = 10^-15*V*rps watts, where V is the volume in cc swept out by the rotor assembly in one revolution, and rps is revolutions per second. From the article, one can make a reasonable estimate of V for the 'turbine' assembly used as V ~ (1/3)*pi*(6.4)³/4 ~ 70cc, giving W_max ~ 7*10^-14 rps. From the graphs provided, a claimed power output of around 10^-6 watt at an rps of 10^-3 implies this device is 'extracting' DE with an efficiency of ~ 10^-3/(7*10^-14) = 1.4*10¹⁰ times the ultimate conceivable value. To say the least, not likely! And this assumes the possibility of generating any differential pressure from DE, let alone 100%. A truly successful attempt to engineer a Casimir type net differential pressure based on say geometry would not imho imply the possibility of 'energy extraction' from the vacuum, but power creation ex-nihilo. The vacuum is after all taken to be in it's ground state and there's nowhere lower to 'fall' - DE or no DE.

 

[alxm]

Yes, I realize there are nuts that believe they can extract 'vacuum energy'. But most of those ideas are plain nonsense, and the ones that aren't, are based on perturbational calculations that were simply wrong.

Prof Leonhardt (mentioned in the other Casimir-related thread here) has written several rebuttals to those kinds of theories, showing that these energy discrepances disappear when you do non-perturbational, exact calculations.