PDA

View Full Version : Extracting Electricity from Lightning storms: Would This Work?


ralph124c
01-24-2007, 09:46 AM
The amount of electricity in thunderstorms is awesome-a single lightning bolt includes a current flow of millions of amperes, albeit for only fractions of seconds. Could we extract and use this energy? Here's my idea; we tether large diameter copper wires to helium ballons, in spots where thunderstorms are common.e wires are connected to gian capacitor banks (millions of farads of capacity). When the potential in the clouds rises to several million volts, current flows through the wires into the capacitors, charging them. this energy is then dichraged skowly, and converted to AC, which can be fed into the grid. Would this work?

brewha
01-24-2007, 09:57 AM
It worked for Marty and Doc :)

I've actually wondered about this as well. I saw a tv show where they were studying lightining. They would go to a thunderstorm and launch a rocket into the clouds with a thin copper wire attached to it and the ground. About 90% of the time, as soon as the rocket hit the clouds, a lightining bolt would follow the wire to the ground.

In this situation, the rocket and the wire were destroyed by the lightining. I don't know how a balloon would survive. Also, it would take a HUGE balloon to hold up 5,000-10,000 ft of large enough guage wire that would survive a lightining strike.

Interesting question, though.

Mangetout
01-24-2007, 10:03 AM
It's going to be hard to make that cost-effective - large-diameter copper wires are going to be heavy (not to mention expensive), which means a large (expensive) lifting platform is required (in which the lifting gas must be periodically replenished (more expense). Large baloons are going to be hard to keep tethered at any kind of altitude, particularly in the stormy conditions that often accompany thunderstorms.

Perhaps a more workable solution would be some kind of tall towers - they need only be significantly higher than the surrounding terrain in order to attract lightning strikes - I suppose a small balloon lifting a lightweight cable could be extended from the top of these to provide a sacrificial initial path to ground.

...except it isn't a path to ground that you're talking about, it's a path to an insulated capacitor, which might also be an issue, both in terms of engineering (how do you make sure the charge goes into the capacitor instead of just travelling most of the way down the conductor, then skipping a short distance to ground?)

Also... is lightning really predictable/reliable enough to make it work? I doubt it.

Patty O'Furniture
01-24-2007, 10:33 AM
You're talking about banks of capacitors that would fill a football stadium - and that might be enough stored energy to keep a neighborhood happy but not much more.

Other issues: The capacitors would need to be rated massively huge for both capacitance value and voltage. High capacitance caps at low voltage ratings are common, as are low capacitance cap rated for high voltage. But when you start increasing both values, tnen you're really talking about some big Rosie O'donnell sized caps.

Lastly, it would take tons of nasty electrolyte to make all those caps. Nobody would want that in their back yard.

gotpasswords
01-24-2007, 10:37 AM
We don't have a dependable and re-usable means of controlling that much energy. We're not even able to replicate that much energy in lightning labs - the air simply can't contain the voltage without arcing. PG&E has a lightning strike test facility that can only put out about 700,000 volts at about 3/4 of an amp. That's a pittance compared to real lightning that can be up to 1,000,000,000 volts and 300,000 amps

It would be about as difficult as if someone told you to stand in the bottom of the Grand Canyon with a mason jar and wait for the Atlantic Ocean to fall fom the sky. Your task will be to capture that ocean of water in your jar without breaking the jar and without drowning at the bottom of the canyon.

Even Doc and Marty's fictional setup was destroyed on its first use.

According to Pliny
01-24-2007, 12:19 PM
I think it would work if you didn't try to send the electricity to earth, but kept it in the air.
Just keep a balloon in the clouds over nearly perpetual clounds of Seattle, and you could run a refueling station in the air for electric-fired hotair balloonists.

Sunspace
01-24-2007, 12:51 PM
How much energy are we talking about here?

Say one lightning bolt is 1 gigavolt (GV) at 300 kiloamps (kA), as gotpasswords mentioned. That's a power of 300 terawatts (TW), which can also be expressed as 300 terajoules per second (TJ/s), since power is a rate of energy flow per unit time. But how long does the bolt last? if it's 0.1 milliseconds (ms), that's a total quantity of energy of 300 TW x 0.1 ms = 300 TJ/s x 0.0001 s = 30 GJ.

How does 30 gigajoules compare to the quantities of energy in the electrical grid?

A 1-GW power station would require 30 seconds to put out that much energy.

A house with 100-amp electrical service can use electricity at a maximum rate of 100 A x 240 V (typical NA residential service is 240-V centre-tapped, remember) = 24 000 W = 24 kW. So to use up 30 GJ, the house would have to use all 100 A for a period of 30 GJ / 24 kW = 30 GJ / (24 kJ/s) = 30 GJ x 1/24 s/kJ = 30 000 000 kJ x 1/24 s/kJ = 30 000 000/24 s = 1 250 000 s = 14.4 days. :)

Looks like there's plenty of energy there. Now... how frequent are lightning strokes in each given area? And would harvesting them mess some atmospheric balance up somehow?

If you started bleeding off the energy in atmospheric voltage differentials before they built to the point of lightning discharge, would that affect convection currents and cloud formation?

Harmonious Discord
01-24-2007, 01:11 PM
More practical than a capacitor is a super cooled storage coil. The power company installed a couple somewheres in central Wisconsin to offset a capacity problem during peak draw periods. I've never heard anything about them since the announcement was made a few years ago. One day lightning may strike and defeat the safety features and we can see what happens. A big explosion is likely. The first stored lightning strike is possible, if some power shunts to ground.

Sapo
01-24-2007, 01:53 PM
Lightning is very predictable. If you live by the Catatumbo River, that is. Here is a pdf (http://fisica.facyt.uc.edu.ve/relampago/4.Publicaciones/Revista%20FARAUTE%20(English).Pdf) that describes the phenomenom. I wonder if that could be harnessed.

Here is the abstract for those with trouble with pdf:

Abstract
To the south of the Maracaibo Lake (Venezuela) it happens from remote times a recurrent lightning, even in dry seasons, denominated Maracaibo Lighthouse or Catatumbo Lightning. Diverse hypothesis has been surmised to explain the located character, recurrent and old of the phenomenon, being reason of controversy its complete understanding. The results of the expeditions are presented carried out with the purpose of to locate the epicenters and to characterize the phenomenon physically. Additionally a microphysics model is discussed; this model is based in the methane gas like causal agent of the atmospheric electric activity. Keywords: Lightning of the Catatumbo, Atmospheric Electricity.

Sunspace
01-24-2007, 02:20 PM
In many places we already have tall towers that are regularly hit by lightning. The CN Tower gets hit hundreds of times per year, for example. I presume that there are huge busbars that ground it to the earth. Could we capture that energy? What would happen if we put a coil around those busbars, hooked up some big-ass diodes, and fed it into a couple of DC rails?

I guess what I'm asking is, what are the precise qualities of the surges in these grounding bars when lightning strikes?

si_blakely
01-24-2007, 02:33 PM
You can use lasers to ionise the air to make a starter path for lightning. Safer than balloons and cables.

Your real problem is trying to avoid resistance (or is it impedence in this case). Too much as you try to capture it, and the lightning will just jump somewhere else to go to ground. It's just jumped an air gap of thousands of meters - you need some mighty good insulation.

Si

stuyguy
01-24-2007, 03:33 PM
It would be about as difficult as if someone told you to stand in the bottom of the Grand Canyon with a mason jar and wait for the Atlantic Ocean to fall fom the sky.
This has got to be one of the greatest analogies I've ever heard. Good job, gpw!

Crafter_Man
01-24-2007, 03:43 PM
It's impractical to directly store the energy of lightning in a capacitor. The capacitor would have to be able to store a very large amount of energy over a very short time interval, which means its ESR and ESL would have to be almost non-existent. Furthermore, the dielectric would have to have an extremely high breakdown voltage, which means the capacitance will probably be pretty low. Lastly, you'll probably want to rectify the voltage before feeding it to the capacitor. Good luck designing a rectifier that can withstand the lightning strike's current & voltage.

A better idea might be to use a lightning rod as the primary of an air-core transformer.

Billdo
01-24-2007, 04:14 PM
Isn't a variation of this what Benjamin Franklin did in his experiments in elecrticity with a kite and key (http://en.wikipedia.org/wiki/Benjamin_franklin#Inventions_and_scientific_inquiries)?

si_blakely
01-24-2007, 04:43 PM
Isn't a variation of this what Benjamin Franklin did in his experiments in elecrticity with a kite and key (http://en.wikipedia.org/wiki/Benjamin_franklin#Inventions_and_scientific_inquiries)?Yep, and ol' Ben was pretty lucky to not end up a crispy critter for that particular stunt - he should have got a Darwin award for that piece of genius.

Si

BubbaDog
01-24-2007, 05:06 PM
Issue 1: capturing lightning - hard, but not too costly

Issue 2: storing megawatts of electrical energy - hard, costly, very costly, so costly that nobody's found a pracical solution yet, so costly that even though prices on the power grid fluctuate wildly there are very few "storage" methods employed.

In other words the big problem isn't capturing the energy. The big problem is storing the energy.
The power industry has been trying for years to find cost effective ways of time shifting energy production to energy usage.
To date the only methods that are somewhat cost effective for large amounts of electrical energy are one-off methods like pumped hydro storage and compressed air energy storage.
As far as capacitors, coils, flywheeels, etc - there's a lot of research and prototype projects but nothing is challanging economics yet.

stuyguy
01-24-2007, 11:05 PM
Underneath the eyecrossing calculations in his/her post, Sunspace mentioned something that I'm hoping someone will address, namely this:

Looks like there's plenty of energy there... [What] if you started bleeding off the energy in atmospheric voltage differentials before they built to the point of lightning discharge...?This idea seems much more promising than... umm... catching lightning in a bottle.

Any thoughts on the feasability of this strategy?

Harmonious Discord
01-25-2007, 06:00 AM
Underneath the eyecrossing calculations in his/her post, Sunspace mentioned something that I'm hoping someone will address, namely this:

This idea seems much more promising than... umm... catching lightning in a bottle.

Any thoughts on the feasability of this strategy?

It's also the energy source and and space launch means of a whole series of stores with the Star Patrol and Med Ship. A number of books use the same universe plot. A large metel grid structure is used to bleed charge from the atmosphere on every planet that has one.

thirdname
01-25-2007, 07:00 AM
If you started bleeding off the energy in atmospheric voltage differentials before they built to the point of lightning discharge, would that affect convection currents and cloud formation?
I don't know, who is John Galt?

Sapo
01-25-2007, 07:03 AM
You can start here:

http://en.wikipedia.org/wiki/Atmospheric_electricity

and then for kicks, here:

http://en.wikipedia.org/wiki/Earth_battery