Atmospheric electricity as energy source
Using lightning as power source? Unlikely due to high volate and current. But, a lightning discharge is not necessarily required, in order to collect atmospheric electricity.
Lightning arrestor principle
I guess, a lightning arrestor is actually not hit by a lightning, since, assuming low diffusion, the charge, surrounding it, is continuously depleted to earth. Thereby the air resistance around a lightning arrestor is increased, protecting the corresponding building from the lightning discharge. On the other hand, a high, electrical potential between sky and earth leads to accumulation of charges on any outstanding, high, conducting object. Since in cities many buildings conduct charges, the charge dissipation per building is reduced. Maybe also this way, lightning becomes absent in cities. Of course, the presence of single, extraordinarily high buildings again increases the probability for lightning discharges, since the charge searches the shortest way through the comparably strong resisting air.
Anyways, the presence of a naturally occuring, electrical potential raises the question for it's collection and usage.
- conducting, with low resistance (lost energy becomes heat)
- resistant to strong heating, without melting or burning
- collect the charge difference between earth and sky in large capacitors
- that still resist internal discharge, even in the presence of several thousand Volts
- while, on the other hand, having a strong electrical field inside
- resistant to large changes in the voltage's order of magnitude
High Voltage Conversion
The electric discharges occur in waves, rather than continuously. Therefore inductors / electric transformers could be used, to lower the voltage in favor of higher currents (and vice-versa), whenever higher or lower voltages are favored.
Prolonging the discharge
The shorter the discharge, the higher the requirements to the apparatus, since it has to withstand higher voltage and current changes. Therefore it would be advantageous to collect the fast discharge but prolong it's dissipation through the power collecting apparatus. To achieve this, conductors could be arranged to form inductors, in order to store some energy in form of a magnetic field. Of course, this increases the electrical resistance of the apparatus, making it a more uninteresting target for the atmospheric electricity to discharge.
Maybe one could make use of on aspect in the nature of lightning here: Air is a strong isolator, isolating the earth's charge from the sky's charge. But, as soon as this border has been overcome, when the electrical potential between earth and sky became high enough to break through this isolator at some point, creating a tunnel of electrical charge dissipation (and lightning), the air in this tunnel (and close to it) becomes hot and ionized. This way a temporary "pseudo-conductor" is created between earth and sky, which attracts more charges, wanting to use it for dissipate. The electrical potential between earth and sky is thereby diminished or annihilated, reducing the probability for the formation of another such tunnel, at least nearby and for a certain period of time. This way charge has only one option: Use the existing tunnel to dissipate. This, in turn, has the potential to solve the above problem of the "uninteresting target": The collector of our apparatus should offer a high potential (low conducting resistance), making it an interesting target for atmospheric charges, but, as soon as they have established a conducting tunnel through air and are thereby committed to using it, the electrical resistance of our apparatus may increase, allowing it to collect the dissipating energy. Inductors offer themselves for this task. Of course, one should also ensure, that an established ionization tunnel won't break down again too fast, meaning, the apparatus must not increase the electrical resistance too much. On the other hand, increasing it too few, stresses the apparatus physically. I guess, further science must be carried out, in order to design an appropriate apparatus, providing for this precise requirements.