Why can't we capture lightning and convert it into usable electricity?
This is an interesting idea, which has been raised from time to time but seems likely not to take off for several reasons.
For starters, let's try to put a few numbers into the problem. There's a lot of variability here, so the following numbers are just ballpark figures to help us get a feel for just how useful lightning could be if harnessed.
A typical lightning bolt carries energy of a few hundred million joules. A joule is the energy that corresponds to one watt of power for one second. For example, a 100-watt bulb uses 100 joules of energy every second. An hour has 3,600 seconds in it, so a 100-watt bulb running for one hour uses 360,000 joules, and it uses 3.6 million joules in 10 hours. Of course one 100-watt bulb consumes very little energy compared to all the stuff you likely have in your house, and you're just one person!
You can probably start to see the problem - lightning bolts just don't carry that much energy relative to the rate at which we use it.
There are additional problems. First of all, lightning is sporadic, so one can't count on it being there when one wants it. Energy would have to be collected and stored for use as needed. Unfortunately, it's not easy to convert the very high voltage of lightning to some lower voltage that we know how to deal with easily.
There have been suggestions that one might be able to use lightning to generate hydrogen from water in a fairly direct way and then use that hydrogen later, but there hasn't really been a lot of serious work done on this. People have also suggested trying to harness the energy caused by heating of water (or other materials) due to lightning, but again, the total energy you get seems too small to bother with.
Add to that the fact that lightning tends to be quite destructive where it hits and that given the relatively small amount of energy per strike one would need huge arrays of lightning collectors, and it seems likely that we'll be taking easier routes to getting energy for quite some time.
Dr. Knowledge is written by physicists Stephen Reucroft and John Swain, both of Northeastern University. E-mail questions to drknowledge@globe.com or write Dr. Knowledge, c/o The Boston Globe, PO Box 55819, Boston, MA 02205-5819. 