Lightning appears to be this limitless supply of energy, so why isn’t this being considered as a valid source of our future energy needs. Surely we could have some sort of lightning rod connected to a huge array of batteries to store all of this electricity. I’m sure there is a simple explanation, but I’m interested to hear what it is.
In: 1090
The actual amount of energy in a lightning bolt is not *that* high. A lightning bolt contains about a gigajoule of energy, much of which is lost as thunder or heat in the path of the stroke. You might realistically be able to extract something on the order of a few hundred megajoules from the actual electricity in the bolt, if you could get it to hit a system made to do that (which you could probably build if you really wanted to – it has some engineering challenges, but nothing beyond what humans can already do).
For comparison, electricity in the US costs roughly $1 per 50 MJ. So each bolt carries perhaps $10 worth of realistically-capturable energy, tops. That’s not that much. If lightning struck your car and managed to make the gas tank explode (it wouldn’t, but what’s an ELI5 without a little Michael Bay-ing of science?), the explosion (~2 GJ) would release more energy than you could have captured from the bolt.
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Another way to approach this is to think about land use.
The most lighting-prone areas on Earth are found in [the highland jungles of central Africa](https://www.researchgate.net/publication/354549112/figure/fig1/AS:1067623387234305@1631552659845/Map-of-world-lightning-frequency-from-NASA.png), where around 50 lightning bolts strike every square kilometer every year. That’s an insane amount of lightning relative to most places; even the fairly thunderstorm-prone southern US only gets about 20.
(EDIT: I’d made a typo in the calculations in the next paragraph that had things off by a factor of 10. I fixed them at the same time as I saved this edit, so if you’re seeing this these numbers are now accurate.)
50 lighting bolts per year, times 500 MJ per bolt (probably a high estimate) is 25 GJ per year per square km. That’s an average of about 800 watts per km^(2) averaged over the year, or roughly the power generation of a few people on bikes pedaling really hard. For comparison, direct sunlight is about 1,300 watts per square **meter**, an area a million times smaller than a square kilometer. Solar panels capture a few percent of this, so a square kilometer of your lightning capture will generate less energy than a single decent size solar panel (especially in the tropical region we’re talking about).
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As a general rule, violent things like lightning bolts or explosions don’t actually release that much total energy, they just release it really *fast*. (There are some exceptions, like nuclear weapons, but even then the rate is much more of a factor than the total energy release.) In other words, they don’t have a lot of *energy*, they have a lot of *power* (energy divided by the time over which it is released). Whatever you eat for lunch today will contain more energy than a hand grenade, it’s just released slowly.
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