- Wow, getting a drone to survive the massive electromagnetic fields (and plasma!) around lightning strikes is quite an accomplishment. Prior art in the area used rockets trailing a similar light wire to trigger lightning - used by Dr Uman's team at University of Florida (https://ufdc.ufl.edu/UFE0047331/00001).
- And the prior art before that involved a kite and a key
- Rockets triggering lighting with wire has been since the late 50's (M. M. Newman), what's cool about the drone is you can send back data before the strike. Obviously a kite or aerostat would work as well.
I'm sure someone in the 90's was using rockets without wires, the exhaust from the rocket made the trail. I cannot source it.
These guys charging cars shows they are not really serious, but a lot of forest fires are lightning, it's a worthy thing to control if possible.
- This is really cool, but I'm super skeptical of their proposed use case for protecting cities.
Aren't lightning conditions often preceded by strong winds and poor weather conditions? Not a great time to be flying drones. And the approach seems more complicated than simply installing lightning rods.
I'd sooner envision people using the technique to get a kick out of throwing lightning around like they're Zeus.
- My scepticism was more like “don’t cities already have lightning rods?”
- > Aren't lightning conditions often preceded by strong winds and poor weather conditions? Not a great time to be flying drones.
Well, the drone would be tethered by the ground attached wire, so it might not need to be that controllable. Elevation is the main concern, so as long as it can reach the right altitude, the tether could keep it reasonably in the right area.
- I've flown my Mavics in rain and strong wind before - certainly stronger than anything I'd associate with lightning. Most of the lightning storms I've seen haven't been especially windy, but it might vary elsewhere. And that's a consumer drone with negligible weatherproofing.
I assume if there's a business case, they'll eventually automate this with drone swarms that wait in cabinets on building rooftops.
- FWIW, where I live there are often intense thunderstorms during the spring and summer, and they are usually accompanied by windstorms, sometimes generating tornadoes.
- I've been in Tokyo in some massive storms (NTT is a Japanese company), the wind and rain is absolutely insane sometimes. Kind of like a 30 minute hurricane.
- AFAIK the electric buildup starts even before the meteorological shenanigans.
- > Traditionally, lightning protection has relied heavily on lightning rods. However, their protective range is limited, and in some cases—such as wind turbines or outdoor event venues—it may not be feasible to install them. At NTT, we are exploring the use of rapidly advancing drone technology to create a new approach: "drone-triggered lightning"2.
I can't believe that's a practical solution. Surely just installing more lighting road is simpler et more effective. They just want to do something cool and try to justify it sideways.
- The expensive bit isn't the lightning rod itself, but the conductive path all the way to ground that has to handle 10^5 amps.
- > Future efforts will focus on developing technologies for capturing and storing lightning energy for potential use (Figure 7).
According to a quick search, a typical lightning strike carries about 1-5 billion joules of energy, equivalent to roughly 250-1500kWh; enough energy to power a typical home for 10-60 days. But larger bolts of lightning can have up to 8000kWh, almost a year's supply of electricity for a home in a single bolt!
- 8MWh is equivalent to a few hours of electricity generation of a wind turbine.
- Kuala Lumpur gets (generous assumption) about 100 lightning strikes per square kilometer per year [0].
If a single drone could service a lot of square km, then it could conceivably collect a lot of electricity. E.g. if it could service 20 square km: 20 * 100 * 8mWh = 16gWh per year. Not bad, but an upper bound, and it hinges a lot on that first parameter (service area).
- You need ~4 strikes per hour to keep up with a single large offshore wind turbine (15MW at 40% capacity factor).
That would mean 350km² just to match a single wind turbine (at 100% capture efficiency for 5GJ lightning strikes).
This is not ever gonna make economical sense.
- True that an offshore wind turbine can produce 15MW. But it can cost $100m+ just for 1 turbine (built and installed). If drones are going up anyway (to protect a city/citizens from strikes), then electricity generation is effectively free, and the marginal cost is equal to the hardware required to capture it (maybe relatively low).
- I thought it was muuuuuch more than that! I've learned something otday!
- > flying drones into optimal positions beneath thunderclouds to actively trigger lightning strikes, and then guiding the discharge safely away from vulnerable areas
From a military standpoint, I wonder what it would take to discharge into a vulnerable area...
- You could put the wire in the vulnerable area - perhaps using the same drone? But I don't think it would be any use. A lightning strike releases about 1 GJ of energy, mostly into the sky. So the effect at the target would probably be no more than a few kg of explosives which you could have delivered using the wire anyway.
- Plausible deniability?
People tend to get mad when you bomb them, but if no one noticed the drone in the storm it's just a natural strike...
- Fire it at a transformer, take out power in an entire region and blame God. A perfect tool for the CIA.
- > I wonder what it would take to discharge into a vulnerable area
HAARP /s
- This [1] article claims that the electricity from 115 strikes could power the entire US grid for a year, but it's surely napkin math. Awesome tech, though!
[1] https://www.treehugger.com/how-much-energy-is-in-lightning-8...
- Apparently a single lightning strike contains the equivalent of about 40 gallons of gasoline. It’s very powerful but not that significant on the scale of a whole city.
In fact a quick back of the napkin math suggests it would only power a city of a million people for half a second.
- This comment made me wonder about the idea of harvesting lightning as a power source. Obviously it’s incredibly challenging, but I wondered if we had magic sci-fi technology that allowed it, how useful would it be?
Back of the napkin math suggests that even with theoretically perfect prediction, capture, storage and distribution you’d still get at best ~1% of the US’ energy through lightning capture.
- I wonder what the average property damage is per strike. And if forcing lightning reduces or changes storm power. Maybe for preventative reasons you put them outside of towns and such.
- Secondary school physics teacher here: The article is conflating power (watt or joule per second) and energy (joule or kilowatt-hour), so any claim they make is nonsense and the article shouldn't be taken seriously. My students make the same mistake all the time but they don't get to publish it :-)
Power is energy per time unit (thus: energy = power x time), so while the power of a lightning strike is very high (~10GW), the overall energy isn't because it only lasts for a very short duration (apparently the duration of a lightning event is hard to define, [1] says about 0,5 seconds, other places mention much shorter durations, ~10us). So if that 10GW lasts for 0,5 seconds, the total energy is 1,4MWh, which is 1/6 to 1/10 of the electrical energy an average American household consumes in a year[2].
[1] https://amt.copernicus.org/articles/16/547/2023/ [2] https://www.eia.gov/energyexplained/use-of-energy/electricit...
- That article seems very very wrong. I think they missed the difference between GW and GWh.
- that article does not make that claim
- I think it does:
Right at the bottom under Frequently Asked Questions:
How much lightning would we need to capture to power the entire U.S. electricity grid? Merely capturing the energy from 115 lightning strikes would supply all of the U.S.'s annual electricity needs.
- [dead]
- Protecting cities from lightning damage? This is a weapon and you all know it.
- I wonder if we managed to harness and store this electricity from the lightning into some kind of large battery. If a drone can successfully fly and connect with the lighting, this seems like a possibility.
Edit: I read past the line where they mentioned this was in the plans.
- We've come a long way from Benjamin Franklin flying a kite into lightning. https://en.wikipedia.org/wiki/Kite_experiment
- The lightning "strike" mentioned in the article was probably not a direct hit. Nothing can really survive >30kA of current. I recall concerns from Boeing engineers when they switched to carbon fiber fuselages, that a strike would be far more serious than before, with Aluminum fuselages.
https://www.weather.gov/safety/lightning-power
https://aviation.stackexchange.com/questions/35493/are-carbo...
- > I recall concerns from Boeing engineers when they switched to carbon fiber fuselages, that a strike would be far more serious than before, with Aluminum fuselages.
It's a serious problem for carbon-fiber wind turbine blades. Fiberglas is an insulator, and doesn't have lighting problems. Aluminum is a good conductor, and doesn't have lighting problems as long as there's a good a path to ground through the hub. But carbon fiber is a resistor, so conducting a lightning strike generates heat. Some copper or aluminum wire has to go into the turbine blades to bypass this.
- I believe Boeing puts a conductive mesh into the carbon fiber fuselages, but there is still a trade between conductive capacity and weight. Guess which one wins?
- There's 2 kinds of CG and there's long-line-induced EM.
Ordinary -CG is 30 kA / 30 C / energy of 1 t of TNT. +CG is 10x that.
Direct hits are survived all the time by lightning rods for the past 275 years.
Long, unshielded lines of any sort can induce massive transient voltage transients (low current) that need to be protected with appropriate TVS circuits that will wear more in storm-prone areas. EMI from nearby lightning in unshielded computing systems with antennas or even without antennas can also be a factor.
- A lightning rod is copper the thickness of your thumb. Anything thinner would melt. Lightning rods are expensive because thick pieces of copper cost a lot.
- That is impressive, specially the drone surviving! I expect something along the lines of disposable drones, which would like still be cost effective at saving 100-200b yen a year! It’ll be fascinating seeing this deployed!
- https://youtu.be/D6_ZC6BywXs
“Remember who the real enemy is!”
- That's a freefly Alta X in the photos which is a $20k drone commonly used in cinematography.
- So.. how long do we have before situational personal lightning bolt is a thing?
- Apparently they already have the ability to create lightning bolts in the lab for testing. Maybe they can license that.
> we conducted artificial lightning tests on drones equipped with the lightning protection cage. The results showed that the system withstood artificial strikes of up to 150 kA—five times greater than the average natural lightning strike—without any malfunction or damage, covering over 98% of naturally occurring lightning conditions.
- The future is now: Check out Lightning On Demand, https://lod.org/ (Tesla tower approach & scientific motivations) & https://youtu.be/lix-vr_AF38?si=w78LyF9tlxGJB8Ay (capacitor driven Lorentz plasma cannon demo)
- Next step, use the energy?
- This is never going to be economical.
Lightning is ~5GJ per strike. That means you'd need ~4 lighning strikes per hour just to keep up with a single large offshore wind turbine (15MW with 40% capacity factor).
There is also no realistic way to scale the whole thing up to significant levels of power; with the wind turbines, you just build several hundred to get into the GW range. There's simply not enough lighning to achieve that.
And the whole power buffering infrastructure that you would need would be an underutilized waste of (expensive) components.
There's never been any serious attempt at harvesting lightning at scale because a single glance at the numbers reveals how (economically) pointless an exercise it is.
- Yes, thanks for repeating the content from the article.
"In addition, we aim to not only trigger and control lightning, but also to harness its energy. Future efforts will focus on developing technologies for capturing and storing lightning energy for potential use (Figure 7)."
- isn't conventional wisdom that this is "impossible" because you cannot charge batteries that fast?
- Like most things, you’d probably end up heating water somehow and using that energy.
- If the energy is going into batteries. It doesn’t necessarily have to.
Also, technology continues to improve, and this isn’t a “next year” thing.
- Maybe a bank of (extremely) huge capacitors that get charged up very quickly, and are then connected to a battery pack to charge it more slowly?
Keeping control of those charges seems like a huge challenge, as they literally contain the electrical energy of a lightning bolt. I guess for physically plausible capacitors you'd also need to step the voltage way down (by six or eight orders of magnitude!?) before it reaches the capacitors. Are there physically-plausible transformers or other devices that could do that?
Or something that somehow captures the lightning as (lots and lots of) mechanical or thermal energy and then gradually converts that back into electricity?
- Stick the caps in series?
- I'm sorry but Figure 1 Lightning Protection Drone....all I see when I look at that is a abomination of antenna....like 5 or 6 roof antennas crammed into a single point in space time.
Not that it don't look super cook in its own way. But I just reminds me of antennas
120 points by gnabgib 14 hours ago | 57 comments