As far as I remember T-2, it's said that T-1000 cannot form explosives, since he does not have the required chemicals. But it can form solid metal shapes. But what does it use as the energy then? It cannot have a power cell inside, since it can morph in various way, and the power cell has to remain in the same form, otherwise it will stop working. So, what is the mechanism of power supply inside T-1000?
I know no canon answer but a bit about material technology.
Since the design of the T1k is decentralized, it probably doesn't have a central power supply. Just think when it turns into floor tiles to kill the guard - there is no blob left that stands out. The whole T1k flattens out.
So each cell cluster must have their own power supply. What could that be?
- Heat (thermoelectric effect)
- Magnetism (walking through Earth's magnetic field)
- Chemical reactions like in fuel cells. He could filter chemicals from the atmosphere and combine them to generate heat or electricity.
- Billions of tiny capacitors which are pre-charged when the T1k is formed.
- Creating resonance with radio stations to milk them for energy.
Note that the first three would not generate enough energy to let the T1k walk. Unlike humans, the T1k doesn't have a skeleton and joints, so walking will be a very expensive process since it has to mold itself.
The last form is also pretty unlikely. It does work but Radio stations notice this pretty quickly (they monitor their electrical usage very closely) and they would call a car from the FCC real soon to find the guy who sucks all their power. The process would make it very easy to locate the T1k, because it would basically turn him into an antenna which sends a very strong signal. You can see this effect today when you carry a fluorescent lamp to a radio antenna which send on the MW band: It will eventually start to glow without any wires. Radio stations hate it when you do that.
So the T1k probably uses some form of high-energy capacitor or some magical form of energy production which Skynet developed while it built the time machine.
Speculation alert: This is not documented anywhere in any of the films or TV series. Books, fan fiction, and other media may cover this, but I am unaware of their explanations. Here are some of my theories:
Because a T1000 is made up of billions or trillions of nano-machines, and each nano-machine has a 'return to essence' capability, it can be concluded that each nano-machine caries its own power supply.
This can be done several ways:
1) The nano-machine can be a catalyst, which facilitates chemical reactions of elements commonly found in the atmosphere without itself becoming altered. Platinum and Palladium do this in a cars catalytic converter. Upon capture of reactants, the nano-machine becomes slightly heavier than the nano-machines which have no reactants, and are drawn below the surface exposing reactant deficient nano-machines to the atmosphere. Once inside the reactants could be brought together to begin a reaction. These chemical reactions could release tiny amounts of energy which could be captured by the T1000 in much the same way tiny photvoltaic cells contribute to the whole of a solar panel.
2) Each nano-machine contains a tiny amount of radioactive material, perhaps only a few atoms worth, which can produce energy which is captures in the same way as mentioned above. Tactically, this would be a poor design, as anyone capable of detecting radiation would pick up on the signature.
There are elements with short half lives, Radon 222 for example has a half life of just shy of 4 days. This could ensure that the decay does not happen too slowly to be useless as a power supply, but not so fast that the power supply burns itself out prematurely. Radioactive decay has been used to power several satellites and probes that mankind has sent into the cosmos, and knowledge of this technology could have survived the nuclear war.
3) I am going to steal @Aaron Digulla idea of the pre-charged capacitors for this one, because that also seems like a viable idea in the event a small part of the T1000 becomes separated from the whole. (he gets an up vote from me because of his originality)
I am not a big supporter of the radio wave resonance theory, since after the war, it's likely that many radio towers would have been destroyed by nuclear weapons, or rendered useless by the EMPs produced, and therefore unavailable in great supply during the war with the machines.
Solar power seems an unlikely candidate because in the post nuclear war world, there could still be fall out clouds in the atmosphere, and then there is the challenge of keeping a charge going during nighttime operations.
If I remember correctly, time travel is only possible if the traveler is at least covered with living organic tissue (insurgents, T-100).
Logically, the same restriction must apply to the T-1000.
And if he at all has organic tissue, it must be a feature of the nano-machines themselves. Since the very livelihood of organics depend on chemical energy, I would favor the chemical energy-source.
However, I don't recall any scene in T2 that would show the T-1000 eating or drinking to support this
It's nanotechnology of some sort. I imagine each particle has its own power source, which it constantly refuels from the environment. Sunlight, hell... maybe it siphons off 60Hz AC whenever it lingers near a power outlet. If there were some type of microscopic fuel cells for each nanobot, it might be enough power to last for days, but it makes it more difficult to imagine a method for it to recharge.