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A lightning bolt would be worth only about a nickel (2015)

engineering.mit.edu

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Re: A lightning bolt would be worth only about a nickel (2015)

#51

Post by usrn »

joosters wrote: post #16

Lightning-powered bitcoin mining is obviously the next big thing for green energy! Now you need a double helping of luck - first that you get struck by lightning, and second that your miner guesses the right hash to make a block. But maybe the two somehow combine? After all, people who survive a lightning strike are said to be so lucky that they should buy a lottery ticket... so following this logic, lightning powere…

I know a number of people who have been struck by lightning. It seems like you've got a decent chance at survival if you're not touching anything metal.

Re: A lightning bolt would be worth only about a nickel (2015)

#53

Post by ww_wpg »

peterpost2 wrote: post #39
praptak wrote: post #34

Earlier quoted context omitted.

If you really mean gigawatts (unit of power), then you have to multiply it by the time period when this peak power is reached to get the energy output. Lightning bolts have very short durations, tens of microseconds. Let's be generous and give it 1 millisecond. 1 millisecond times 1 gigawatt is 1 million joules, which is the estimate that the article gives.

Woosh, he is making a back to the future reference

Well, today I learned something about physics and pop culture.

Re: A lightning bolt would be worth only about a nickel (2015)

#54

Post by titzer »

omnicognate wrote: post #7
a9h74j wrote: post #2

This reminds me of an old (misleading) graphic in Wired magazine suggesting that people on treadmills could be significantly reducing their electricity bills.

Olympic track cycling medallist powers toasting a slice of bread, which takes everything he's got and leaves him exhausted: https://youtu.be/S4O5voOCqAQ

Yeah, toasters and microwaves take a ton of energy, 800-1000W.

Things like laptops and some desktops could be easily powered by bicycle, though. I managed 220W for 30 mins, and could probably idle 50-75W for hours, which is more than enough for multiple laptops.

Re: A lightning bolt would be worth only about a nickel (2015)

#56

Post by sebzim4500 »

usrn wrote: post #51
joosters wrote: post #16

Lightning-powered bitcoin mining is obviously the next big thing for green energy! Now you need a double helping of luck - first that you get struck by lightning, and second that your miner guesses the right hash to make a block. But maybe the two somehow combine? After all, people who survive a lightning strike are said to be so lucky that they should buy a lottery ticket... so following this logic, lightning powere…

I know a number of people who have been struck by lightning. It seems like you've got a decent chance at survival if you're not touching anything metal.

Do you know a lot of people who stand on top of tall towers during storms?

Otherwise, unless you know tens of thousands of people there is very little chance of knowing multiple people who have been struck by lightning.

Re: A lightning bolt would be worth only about a nickel (2015)

#57

Post by SubuSS »

yetihehe wrote: post #47
WJW wrote: post #15

Earlier quoted context omitted.

500W is an extremely high number as well. Pro cyclists can reach up to 400 Watt in short bursts, untrained people typically can't maintain more than 100-150W for long. We really use quite a lot of energy when measured in how many humans it would take to provide that much energy "manually".

> Pro cyclists can reach up to 400 Watt in short bursts I heard pro cyclists can reach up to 2kW. I managed to make 500W on a rowing machine for 5 minutes, but I'm a couch potato. I believe 400W is a normal rate for cyclists. When you are sitting, your body already produces about 100W of heat.

So cyclists measure their capability in terms of FTP - essentially what power output they can maintain at full throttle for an hour.

This hugely depends on body weight / gender / training levels etc., body weight being a big deal since that’s what you’re transporting. So the other way folks measure output is W/kg of body weight.

A beginner adult male will be in the 100-200W zone, around 0.5-1.5 W/Kg. Usually anyone can train themselves into the 200-300 (3-4 W/Kg) zone which is the recreational pace - the groups of cyclists you see on the road. Beyond 300 ftp (150lb body weight) (4-5 W/kg) you’re reaching race pace. The ones you see on screen have upwards of 5-6 W/Kg FTP output. They obviously have other constraints around putting this output at the end of a 200km ride for 20 mins etc as well, which makes it extra hard.

Finally we come to the KW numbers - all these folks have two kinds of muscles (fast twitch and slow twitch). The sprinters are saddled with a higher proportion of the kind of fibers that can allow huge spurts of power - they put out about 1000-1500W for about 5-10s. These are probably what you’re thinking of. This is pretty much an end of ride (or a sprint section) empty your tanks effort.

Semi related tidbit: track cyclists are a middle kind of beasts here: they put 600-1000W for a couple of minutes but don’t have to worry about riding 200kms to get there.

Re: A lightning bolt would be worth only about a nickel (2015)

#58

Post by martin_a »

praptak wrote: post #34
coldtea wrote: post #26

I call BS. A lighting bolt generates at least 1.21 gigawatts, which is good for many purposes...

If you really mean gigawatts (unit of power), then you have to multiply it by the time period when this peak power is reached to get the energy output. Lightning bolts have very short durations, tens of microseconds. Let's be generous and give it 1 millisecond. 1 millisecond times 1 gigawatt is 1 million joules, which is the estimate that the article gives.

> Lightning bolts have very short durations

That is why you have to hit the cable at a very specific time. It's not that hard.

Re: A lightning bolt would be worth only about a nickel (2015)

#59

Post by Merad »

anon_123g987 wrote: post #29
WJW wrote: post #15

Earlier quoted context omitted.

500W is an extremely high number as well. Pro cyclists can reach up to 400 Watt in short bursts, untrained people typically can't maintain more than 100-150W for long. We really use quite a lot of energy when measured in how many humans it would take to provide that much energy "manually".

While it's true that the power of a human is not much (certainly not enough to power a house), but we have a lot of energy . Most of us carries at least 1 kg (~2 lbs) fat, which contains ~37 MJ of energy. For comparison, a stick of dynamite has ~1 MJ of energy. https://en.wikipedia.org/wiki/Fat#Biological_importance https://en.wikipedia.org/wiki/Dynamite#Form

> Most of us carries at least 1 kg (~2 lbs) fat

It's a lot more than that. Even a fit (healthy, but not necessarily peak athletic shape) adult man will have about 15% body fat, 20% for a woman.

Re: A lightning bolt would be worth only about a nickel (2015)

#60

Post by andrewla »

> The average lightning strike contains about 1 million joules, enough energy to fry the founding father in his boots. “The typical house in the U.S. has 100 amp service or about 28 horsepower,” says Kirtley.

Boy do I get frustrated when using compatible units without conversion. The unit that I hate more than any other unit in the universe is the KwH, which is dimensionally equivalent to the Joule, so I don't understand why we don't just use that instead.

"The typical house in the U.S. has 100 amp service or about 28 horsepower" -- seems that it would be way more interesting to say that "the typical house has 100 amp service at 120V, which means 12,000 J/s".

The way the original quote is phrased (and the introduction of horsepower of all things) seems insane to me; the clarification adds zero value. You still haven't addressed the main question, which is "is the energy in a lightning bolt a significant amount of energy compared to household usage". For all I know 28 horsepower is 1,000,000 J/s, so a lightning bolt would only power a house for a second.

EDIT: as many commenters have pointed out, apparently most houses get 240V service, so just double the number above. Still, this is easily fixable, and the main point is that horsepower does not add any value to this discussion.

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