So why can’t we just harness the power from lightning?

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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

A few problems.

– Lightning is unpredictable. We never know when a storm is going to form and if that storm will generate lightning. We can’t _reliabily_ use it for power.

– Capturing lightning is hard. You need to have a lightning rod attached to a capacitor bank, so you can only capture the bolt if it strikes in _exactly_ the right spot.

– We can’t just put the power into the grid directly – a massive influx like that would burn out the grid. We’d need to store it and deliver it over time, which leads to the next problem.

– Storing lightning is even harder. There is a massive amount of power in a lightning bolt, and we simply don’t have batteries that can store that much power that quickly.

Batteries work at lower voltages and higher currents. Lightning works at insanely high and unpredictable voltages in the millions of volts. The problem with high voltage is that it pierces through any material you could use to contain it, and generally it just destroys things. Lightning is so powerful it can jump from the sky to the earth through miles of air. For comparison, even high-voltage power lines are weak enough that you can hold them 50 feet in the air and the electricity won’t make the jump to the ground or people nearby.

Very little technology is designed to contain or tolerate millions to billions of volts. The technology that can would be complex scientific or industrial equipment, not something small or cheap. And this lightning capturing device would need to be small and cheap. Lightning can strike the same place twice, but it doesn’t do it repeatedly all day, every day. If you want to capture a large and reliable amount of power from lightning you’d need these devices all over the place. It’s just not practical compared to how easy it is to make a solar panel or wind turbine, or to use fossil fuels.

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.

We’ve tried, the power levels involved are just crazy high so the tend to blow the systems out

A single good sized lightning bolt has an energy of 5 GigaJoules (1,389 kWh) but because its transferred over about 10 microseconds the power level is 500 Terawatts

A power plant like Hoover dam can provide 5 Gigajoules over about 40 minutes. The lightning strike is taking those 40 minutes of production and cramming them into 10 millionths of a second and hoping you won’t just vaporize portions of the grid

You can’t use batteries for something like this, they charge about a million times too slow. You end up needing ludicrously large capacitor banks about 10x bigger than the National Ignition Facility uses to fire its lasers to make fusion, and even then you need there to be a thunderstorm overhead otherwise its just spending its time sitting there wasting money

Why don’t you fill your tea kettle from the fire hydrant? Why don’t you charge your cell phone in 7 seconds by plugging it in to the same outlet as your electric car? The answer for all is kind of similar: handling a lot of power for a short period of time is often much harder than handling less power for much longer. Besides all the other practical barriers people have mentioned like predictability and timing and so on.

At the end of the day, spending millions of dollars on a device that can capture a lightning bolt a few times a year is a lot less practical than building a wind turbine that can capture that same energy continuously.