Production of electricity from atmosphere I read the electric field intesity at the surface of earth is 100v/m. Then why can't we keep two metallic sheets at different heights and produce a continuous current by connecting these two sheets via a electric cable?
 A: You can, and the current would be about a micro-amp, because the atmosphere has very high resistance.
So the useful power you get that way is very small.
Check this link.
A: In the 1970s Dr. O. Jefimenko experimented with balloon-lofted antennas and foil-plastic motors.   Rather than employing flat plates, he reduced the high resistance of the air by using arrays of needles which spew plumes of positive ions upwards.  Air which contains mobile ions is a conductor.
If we could fire a KMs-long lightning bolt from ground to ionosphere, and then stick a stepdown transformer in series with it, then perhaps we could extract significant energy from the Earth-ionosphere field.   Since this vertical e-field is thought to be created by the worldwide population of thunderstorms, it's actually a way of tapping the energy of lightning.  But it's tapping the energy of the lightning occurring thousands of miles away on another continent.
Suggestion:  look up the capacitance of the Earth-ionosphere capacitor, the voltage and recharge-rate, and calculate the total amps.  What's the wattage?  It's about the same as a single large power plant.   If we extracted all of it, we could only run a single small city.
