Electronic – Static Electricity Accumulation

You can't guarantee the polarity of the charge and so some form of rectification is needed to ensure that any current is passed through in the same direction irrespective of polarity. This could be achieved with two capacitors and two diodes so that you can store the energy from positively and negatively charged people on two separate capacitors.

The diodes should have an extremely low leakage to prevent charge being lost. The capacitor should also be chosen to have very low leakage for the same reasons.

I think I'd also consider having a spark-gap protection device across the input to the diodes to prevent over-voltage damage. If you use the carpet static value value below to work out the capacitance and voltage rating you should be OK: -

20 mJ = \$\dfrac{CV^2}{2}\$ and if you chose 1 uF, the voltage rating would need to be: -

\$\sqrt{\dfrac{2\times 20\times 10^{-3}}{1\times 10^{-6}}}\$ = 200 volts.

For 10 uF the voltage rating would be 63 volts

1 nF would require a voltage rating of over 6000 volts.

I was planning to have a metal plate on a wristband and the capacitor connected to this and then to ground, this I think should charge the capcitor from what I understand. Would this work?

I would consider the capacitor(s) and diode(s) to be fixed and let folk walking around discharge themselves to a plate connected via the diode(s) to the capacitor(s). It might be a good idea to issue conductive thimbles so that folk don't feel the spark that might jump to the plate. Safety should be considered and the diodes will prevent someone getting a full energy discharge if they touch the plate.

You are confusing electrical current with electrical energy. Given how you express confusion over the fact that current can go in a loop yet energy is wasted, I think that you are also tied to the notion that energy must be tied to the matter that happens to be carrying it.

Yes, current goes in a loop. We do not, on an everyday basis, create or destroy electrons*, and electrons strongly repel each other and are strongly attracted to atomic nuclei, so any current that flows is forced to loop around and come back to the source. This does not mean that energy does not flow, however. If I connect a battery to a pair of wires here, then the battery adds energy to any electrons flowing through it from its positive electrode to its negative electrode. This potential energy per electron is seen as the voltage of the battery. If those wires are connected to a light there, then current will flow through the light. The energy imparted in those electrons in the battery will be converted to light and heat in the light. If you ignore any losses in the wires, then the energy has flowed from the battery to the light, but the net number of electrons has stayed pretty much the same everywhere.

If you're still caught up in the "how can electrons go in a loop but the energy goes from point A to point B" problem, then consider hydropower. The sun shines on the sea. It imparts energy to the seawater, some of which evaporates. Some of that blows over mountains, and some of that rains down. Some of that forms into a river, which someone has dammed. The water impounded behind the dam is run through turbines generating mechanical energy. Then the water runs back into the sea. The water has gone in a loop. The energy has been transported (with great inefficiency) from the surface of the ocean to the turbines in the dam.

Dunno if this helps -- it's always hard to know what will clear up a confusion.

* Please, please do not bring beta decay into this discussion. Yes, electrons are created. No, it is not on topic.