Can energy be extracted from clouds?

Can cloud charge imbalance be used as an energy source?

First off quite some energy must be present in clouds: a lightning path is quite long, and electrical breakdown of air requires about 1MV/m. Most (many, smaller) electric discharges are not seen because they occur within clouds. The electric energy built up can also be lost in other ways (i.e. Lorentz force).

Some of it comes to ground and when it happens it has such large peak power (on average about a trillion watts) that it can not efficiently be harvested.

I assume that charges build up quite continuously during the lifetime of a cloud: if we knew what cloud to select for discharge we could control (by selecting the right cloud or part of a cloud) the power flux, though not easy its hard to rule out as impossible.

Now how exactly do I propose to do this? Air can be made conducting through bruteforce electrical breakdown (not efficient), or by heating it (not efficient) or by an energy form encouraging with higher specificity the ionization of specific molecules present in air (be it oxygen or nitrogen or ...).

Apparently non-lethal weapons were designed which do not use projectiles: a UV laser with 2 optical, parallel paths, each connected to an electrode at the weapon side can tetanize (stimulate at such a pulse rate as to keep the muscle contracted) with specificity any of the 3 broad muscle types (voluntary skeletal muscle, involuntary smooth muscle, and cardiac muscle all respond to different pulse patterns/frequencies). A weapon on same principle was designed to stop cars up to 2km by frying the control chip in the car.

According to hstvi (not sure how credible this source is) ionizing wavelengths with lasers can make a path of air conductive to 2km:

"With an ultraviolet wavelength of 193 nanometers, the maximum effective range is about 100 meters. The effective range increases to two kilometers when a wavelength of 248 nanometers and a more intense beam are used."

Now for our clouds we would not need 2 optical paths to the laser.

Problems I envision: clouds heights are on kilometer scales, so possibly stages of such lasers would need to be mounted on weatherballoons, preferably locked by cable to a certain height/location.

Each laser would could be surrounded by a thick piece of transparent insulator (glass?) so as to allow UV to pass but not current to enter the setup. On the glass electrodes are placed which are connected to a similar electrode on say a retroreflector of this balloon (a lower one targets this balloon).

If forming a conductor with the lasers consumes more energy than would be got from the lesser charged clouds (or parts of them), we may need to allow electrical breakdown to occur at which point switching of the laser beam would not stop the lightning.

Problem lightning?

-
Irrespective of the charges involved, hydroelectric dams are one way of extracting energy from clouds. – AdamRedwine Jan 24 '12 at 13:16
just like they are a way of extracting energy from the sun ... – propaganda Jan 24 '12 at 15:00
So I am not sure how to answer your question because it involves several aspects from physics, engineering to economics. What is currently successful to study lightning is to simply propel small rockets into the clouds that drag a thin copper wire into the lower atmosphere. The lightning then goes down the wire and you could try to harvest the energy by charging high voltage capacitors or other systems. It is all not that practical though as there are very places where you have clouds that are useful during the whole year. – Alexander Jan 24 '12 at 17:34
Anecdotally, it appears not to be practical as the Empire State Building is struck many times a year in the same spot and yet they do not harness that energy. If there were an economic way to harvest this resource, surely they would do so. – AdamRedwine Jan 24 '12 at 18:23
or they are not telling us: perhaps lighting could be seen as some native american resource – propaganda Jan 25 '12 at 6:08
2. The distance of 2 km by far not long enough but that is a minor point.