# Tag Info

36

For the photons that make up light to exist they have to be travelling at the speed of light. This means that to store them you have to put them in a container where they can move around at the speed of light until you want to let them out. You could build the container out of mirrors, but no mirror we can build is 100% reflective, or indeed can be 100% ...

26

Your examples are a bit misleading. For example you say: We can store cold (ice),heat (i.e. hot water bag) But we can only store heat temporarily, just as we can only store light temporarily. Your ice pack will eventually heat up and your hot water bottle will eventually cool down, just as light stored between two mirrors will eventually escape. ...

10

Some energy densities for easily compactified substances: Purely electric storage: electric field in a capacitor, 0.000 36 MJ/kg electric field in a supercapacitor, up to 0.004 2 MJ/kg 1 T magnetic field has energy density $\frac{1}{2\mu_0}B^2 = 0.4\,\mathrm{MJ/m^3}$, estimate mass for superconducting magnet enclosure to decide where to put this on the ...

6

Yes, we can store energy as the kinetic energy of a flywheel. The problem is that we can never completely eliminate friction, so our energy leaks away over time. But then we don't store energy as charge if we want long term storage, because we can never make resistance infinite and our charge gradually leaks away. Batteries store energy as chemical energy, ...

6

Storing electricity as electricity is currently possible only in capacitors. A lot of fuss is made about the potential of super-capacitors and ultra-capacitors to scale up, but little has happened yet at the grid level. Almost everything else involves converting electricity to a different kind of energy; and then converting it back to electricity when ...

6

(I tried to post this response with chart and links, but I'm new here, so the system won't let me include images or more than two links. Please cut and paste the other links to view them in your browser.) This diagram from the NH3 Fuel Association (taken from www.nh3fuelassociation.org/about-us--why-nh3) (scroll down the page) may answer part of your ...

6

One alkaline AA cell has about 11 kJ of energy. For a laptop battery, it is 360 kJ. Chevrolet Equinox Fuel Cell has 58 MJ of energy. One kilogram of TNT carries about 4.184 MJ of energy. Divide the numbers from the previous paragraph by this constant to see that the AA cell, laptop battery, and electric car battery have 2.6 grams, 86 grams, or 14 kilograms ...

5

Making ammonia is an absolute bugger because nitrogen is so unreactive. The normal route is the Haber process, http://en.wikipedia.org/wiki/Haber-Bosch, but this requires high pressures and temperatures. Hydrogen is easy to produce from electricity, and I guess that's why it's the first choice for storage of energy generated by unreliable sources like wind ...

3

I'll try to answer your question in the spirit of how you asked it. Basically you can't really store anything you've mentioned. The ice will eventually heat up, the heat will cool down and the battery will lose charge. A box of mirrors with light shined in it will "store" light like your other examples but it will lose the energy much faster then any of ...

3

We can store light - just for very small amounts of time. I'm no physicist though, so perhaps this link isn't what you intended? http://news.bbc.co.uk/1/hi/sci/tech/3308109.stm

3

This site covers four current modes of electricity storage: 1.Pumping water from low to high elevations for future hydroelectric use as needed. 2.Melting salt at solar farms to several hundred degrees and storage in insulated tanks, for future use. 3.Compressed air energy storage by wind farms into underground geologic formations. 4.Utilizing "flow ...

3

There is actually a technology called "energy recovery linac" that is designed to take the power stored in a beam and deposit it back into the fields of the accelerating cavity (always superconducting in this case, it seems) so that the next beam can take it. Sort of a relay race -- when one beam gets exhausted after too many collisions, another, higher ...

3

The problem with maintaining a constant voltage is not restricted to flywheels, but is important for all kinds of generators. Power plants have to generate a constant voltage independent of the momentary load on the grid, yet this is not how a plain electric generator works - it will spin slower under load, just as your cordless screwdriver does when you use ...

3

It is possible to capture positrons (antiparticle of electron) in a magnetically confined plasma - the repulsive forces get very large unless you do something to equalize the charge. The energy density that could be achieved is stunning. This was the principal plot line behind Dan Brown's "Angels and Demons" - this plasma (made at CERN, that den of mad ...

1

I'd love to see more elaborate answers to this, but generally the idea is intuitive. Resistors are linear and only dissipate energy. Inductors and capacitors are nonlinear and store magnetic and electric energy respectively. Their constitutive relations are the following: Inductor: $v = L\frac{di}{dt}$ Capacitor: $i = C\frac{dv}{dt}$ It's only when you ...

1

The system you describe, a water tower with pumps and turbines, is a version of a pumped hydro storage system. The amount of energy stored in a pumped hydro storage system is defined by the elevation, i.e. the height that the water is lifted; multiplied by the volume of water that is lifted (assuming that the height the water will fall, is the same as the ...

1

The equilibrium position of the molecule from the surface will be due to the tradeoff between a (relatively) long range Van der Waals force (or electrostatic force if the molecule is charged or dipolar) and the short range exchange repulsion. You would expect the minimum to be when the molecule touches the surface, so it would around the Van der Waals ...

1

It's hard to store light as light because the most common way light interacts with matter is through absorption and emission, which is how mirrors work. However light rays can be bent by gravity, so it would be possible to arrange several massive stars in a way such that a light ray would move in a loop around the stars without energy loss.

1

As Everett says in his comment, you can't apply a huge voltage, or indeed any voltage, across a superconductor. Because the resistance is zero the potential difference between any two points in the superconductor is also zero. If you have a superconducting loop/coil, when you put energy into it you are basically storing the energy in the magnetic field ...

1

Ammonia is also toxic, tricky to handle and burning it is going to generate a whole bunch of the same nitrous-oxides you get from fossil fuels.

1

A battery's energy capacity is normally quoted in Amp-hour, (or mAh) the number of amps it could (in theory supply) for an hour. If you multiply this by the voltage you get energy. Specifically if you multiply by 3600 seconds in an hour you get Joules. A NiHH rechargable AA cell is about 2200mAh and is 1.2V; 2200mA * 3600s * 1.2V = 9.5KJ, an alkaline (ie ...

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