The potential generated by the static in clouds are truely phenomenal. As a rough estimate, the dielectric breakdown strength of dry air is aproximately 3MV / m. Extrapolate that to a cloud some 10km up and you end up with an enormous voltage.
When one looks at the effect of a lightning strike on objects, it normally does not cause a tremendous amount of damage e.g. one will see small rocks getting shattered (I don't want to be the object that is struck though) Sometimes people are struck by lightning and survives without any visible harm.
Benjamin Franklin, and others, flew kites in electric storms and tried to capture some of the charge in a Leyden Jar (a capacitor of sorts) There should be a plenty of info on Google Scholar.
I agree with David that the electrical potential difference can be enormous although not as high as the breakdown voltage of dry air would suggest. It is only under specific conditions that lightning strikes down to the earth surface. usually it remains in or between clouds. if the air is sufficiently ionized it can find its way down to the earth surface.
However the amount of energy is much less that you would expect from the spectacular visual effects. It will be difficult if not impossible toharvest this low amount for acceptable costs.
In fact Nicola Tesla attempted to extract such energy through resonance with the ionospehere. He did this before the resonant frequency of the ionosphere was actually "discovered".
Some figures (mean values) about lightning in France ,
550 000 square kilometers
10^6 strokes per year
1,8 10^9 metal poles (to catch all lightnings)
500MJ for each stroke (duration is less than 25ms)
at the end of the day, if the entire energy is captured it gives 20 MW.
The quantity of energy, converted to power is equivalent to a couple of wind mills.
More if you estimate the mass of metal needed to build the lightning catcher... and the cost of it...
It is useless to try and catch the energy from lightnings.
Looking at storing this energy, try to imagine how to store a 500MJ energy pulse that lasts less than 25ms with currents in the 40kA range...
thanks all for valuable information but is there some guide lines by which we can measure the static voltage.I Think lightning is the process of short circuit.
May be possible!
We can pass the high lightning current through some highly resistive load (which should obviously sustain such currents) (like a lightning arresters). Tremendous heat will be generated by that load which can be used for generating energy. Finally we can store that energy and bring it into use later.
Such energy will be a cleaner but dangerous one.
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