[HN Gopher] Rain Panels: Harvesting the energy of falling raindrops
___________________________________________________________________
Rain Panels: Harvesting the energy of falling raindrops
Author : MadcapJake
Score : 75 points
Date : 2023-07-28 14:54 UTC (8 hours ago)
(HTM) web link (thedebrief.org)
(TXT) w3m dump (thedebrief.org)
| WesolyKubeczek wrote:
| Why not make panels that do both?
|
| Also make them harvest energy from the wind at the same time
| somehow.
|
| "Come Rain or Come Shine"(tm)
| PaulKeeble wrote:
| These need a conductor to touch the raindrop which ends up in a
| capacitor for the charge stealing to work. Any conductor you
| put on top of a solar panel will block the sunlight so it will
| decrease efficiency. The rain collectors equally need as much
| surface area as possible for the conductors with their
| underlying capacitor area close to them. It's more likely to be
| effieicent to have separate panels as a result. Also rain
| panels can face away from the sun and suffer no ineffiencies
| from that.
|
| So the optimal strategy is solar facing the sun and rain on
| roof that is not.
| johnea wrote:
| Fuget aboud it...
| monero-xmr wrote:
| Wouldn't it be better to have some underground cistern and as
| water flows down it passes through a turbine? A roof solution
| will generate a tiny amount of electricity.
| leetnewb wrote:
| Could theoretically put a wheel/turbine in downspouts from the
| roof.
| chucksta wrote:
| I forget the ending but I think its milliwatts
| https://www.youtube.com/watch?v=S6oNxckjEiE
| BizarroLand wrote:
| XKCD did a What If about this very scenario:
|
| https://what-if.xkcd.com/23/
|
| If the generator cost $100 to buy and install, it would take
| nearly a century to pay back its install cost even in one of
| the rainiest locations in America.
| lesuorac wrote:
| I found the bottom of that page much more interesting.
|
| >> What if you strapped C4 to a boomerang? Could this be an
| effective weapon, or would it be as stupid as it sounds?
|
| > Aerodynamics aside, I'm curious what tactical advantage
| you're expecting to gain by having the high explosive fly
| back at you if it misses the target.
| BizarroLand wrote:
| Death before dishonor.
|
| Or at least put a remote trigger on it so you can get
| some splash damage on your target.
| foobiekr wrote:
| EROI for that is almost certainly negative and it's more likely
| to just be a source of clogs and maintenance.
| ramesh31 wrote:
| > Wouldn't it be better to have some underground cistern and as
| water flows down it passes through a turbine?
|
| Congrats, you've invented the hydroelectric dam.
| gardenfelder wrote:
| Heck! For many of us, that cistern would help cover for our
| many drought periods, electricity notwithstanding...
| SoftTalker wrote:
| I've thought about it, but water in my area is so cheap the
| payback would be forever.
|
| I pay about $30/month for local utility water. It's metered,
| but I rarely exceed the minimum billing amount.
| [deleted]
| HelloNurse wrote:
| How can the huge and expensive panels required to intercept a
| meaningful amount of rain possibly compete with harvesting the
| energy of the same rainfall with small and inexpensive bronze age
| technology? Ridiculously high efficiency doesn't seem likely.
| bobthepanda wrote:
| It would probably be better if you had a roof for solar panels
| that also collected rainwater for storage.
| yuumei wrote:
| Am I missing something or does this generate on the order of 3
| nano watts? (They show charging a 4.7uF capacitor in 25s to 2v)
| jacquesm wrote:
| I've seen this idea in different guises many times by now, there
| should be one of those standard 'why your energy idea based on
| rain/VAT/resonance/sound/cold fusion/vacuum fluctuations won't
| work' checklists for this one by now.
| abeppu wrote:
| Even looking at the actual paper [1] I think no raindrop ever
| touched such a device during their experiments? In their
| extremely brief experiments section, they say "The water droplet
| was generated by the commercial infusion sets" which I think
| means ... they sprayed one of their devices with a hose? There's
| nothing which seems to indicate anything about droplet size, or
| rate of simulated rain. Did they use a pressure washer?
|
| Not describing the actual amount of "rain" they sprayed on the
| device also makes it unclear whether their "5 times higher"
| number is an apples to apples comparison, esp since 200W is a
| _lot_.
|
| > When the area of the raindrop energy harvesting device is 15 x
| 15 cm2, the peak power output of BAGs is nearly 5 times higher
| than that of the conventional large-area raindrop energy with the
| same size, reaching 200 W/m2
|
| I think perhaps the most important sentence on the posted article
| is (emphasis mine):
|
| > Christopher Plain is a _Science Fiction and Fantasy novelist_
| and Head Science Writer at The Debrief.
|
| [1]
| https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=101...
| ilyt wrote:
| I'm sure that 20W the whole panel generates every few days for an
| hour or two will offset the cost
| kevinlinxc wrote:
| 200W/m^2 is what it says at the end right? Regardless, the tech
| will improve and get cheaper and this will be a nice sell for
| countries with less sun. Maybe eventually we could get hybrid
| panels powers by Sun or rain?
| angry_moose wrote:
| Then their math is off by nearly 4 orders of magnitude
| somewhere (see other comments in the the thread).
|
| "Technology improvements" can't get around the fundamental
| limit in the amount of energy available to harvest.
|
| Edit: Oh, that's horribly misleading. They seem to be
| reporting the theoretical maximum output of this harvesting
| technology - e.g., how much energy could be recovered if they
| started blasting the panel with a firehose. The amount
| available in rain is on the order of .2-.4 W/m^2. At that
| rate you'd never recover the amount of energy as was used to
| produce the panel.
| jacquesm wrote:
| 200 mW at best... seriously, this is bunk.
| JadeNB wrote:
| > I'm sure that 20W the whole panel generates every few days
| for an hour or two will offset the cost
|
| You can--and it's usually safe to, in the translation from
| actual researchers to PR departments--ceertainly doubt the
| viability of this claim, but the whole article is devoted to at
| least explicitly claiming that they're aware of the obvious
| problems, and can overcome them:
|
| > ... the efforts to collect energy from falling raindrops have
| faced a technical hurdle that has made the concept inefficient
| and impractical. ... as one might expect, the amount of power
| per raindrop is incredibly small. ...
|
| > Now, a team of researchers says they have found a design and
| configuration that greatly reduces the coupling capacitance
| issue and one they claim could make energy-harvesting rain
| panels a practical reality.
|
| One key seems to be that, although you're obviously meant to
| think of rooftop panels, it seems more to be about large-scale
| installations:
|
| > "The peak power output of the bridge array generators is
| nearly 5 times higher than that of the conventional large-area
| raindrop energy with the same size, reaching 200 watts per
| square meter," Li explained, "which fully shows its advantages
| in large-area raindrop energy harvesting."
|
| (I do notice on re-reading that it says "... may lead to the
| development of rooftop, power-generating rain panels", but (1)
| one can freely claim that anything _may_ lead to something
| else, and (2) one can claim that anything _may_ lead to
| anything else, so I prefer to go by quotes from the researchers
| themselves.)
| ilyt wrote:
| Right, so why they are bothering ? The technical limit is
| known and it is making it barely acceptable if it was _free_
| (because you still need to have dedicated inverter channel
| for the power conversion as characteristics are much
| different than what solar panels generate).
|
| And if it wasn't free or near-free it's competing with
| putting one more panel or adding one more battery to the
| system. Or... just big, cheap funnel that is feeding water
| generator Sure you lose some of the velocity but it is so
| much simpler system
|
| Like, generating energy from tiny movements have its niches
| (like sensors powered by piezoelectrics from vibrations of
| machine they monitor), but using it for raindrops just feels
| like a waste of time, most areas don't even get enough rain
| for that to matter.
|
| Now if they figured out to do it to airflow with few moving
| parts, that would be more interesting.
| feoren wrote:
| Peak output doesn't matter: you cannot get more energy out of
| rain than rain has. You could build a turbine that can
| theoretically generate 10MW at its max speed, but if it's
| being pushed by ants, who cares what its max theoretical
| output is? Look at the top comment of this thread. Even at
| 100% efficiency, there is nowhere near 200 W/m^2 of energy to
| possibly extract from rain. Four orders of magnitude less.
| Retric wrote:
| Raindrops fall at 10m/s or less. The absolutely rainiest
| place on earth revives 12 meters of rain per year. A 1x1x12
| meter block of water weighs 12,000kg going 10m/s it has KE =
| 1/2 M * V^2 = 6 * 10 ^ 5j. 200 watts per meter is
| 200j/second...
|
| So your hypothetical 200 watts per square meter at 100%
| efficiency assuming spherical cow types of ideal conditions
| could possibly provide that power for 50 minutes _per year_
| under ideal circumstances or average 0.02w /m2 over a year.
| And average roughly 0.002w/m2 in extremely rainy though not
| world record setting locations.
|
| Now, you ignore the kinetic energy in rainfall and try and
| harvest the potential energy when it lands at a high
| altitude, allowing a large collection area and large
| differences in altitude. But we call those things dams.
| willcipriano wrote:
| In the UK it would probably look a lot better, rainforests as
| well.
| konschubert wrote:
| A factor 3 doesn't compensate a factor 1000
| willcipriano wrote:
| There is a sort of reverse time value of money[0] but for
| energy. When it's raining, it's often cloudy so solar isn't
| as efficient and the cost of energy goes up. Things like
| this become more attractive under certain conditions and I
| could see a use as the technology is improved and
| commercialized. Energy is never going to be a single
| technology, we will probably end up with dozens of sources
| in the end.
|
| https://en.m.wikipedia.org/wiki/Time_value_of_money
| Brusco_RF wrote:
| Even the most optimistic reading has these "rain panels"
| well under 1W/m^2. For comparison, peak solar irradiance
| is something like 1400W/m^2.
|
| This webpage has already burned more energy than that
| panel will ever produce.
| ilyt wrote:
| Right. So mount a wind turbine instead of this garbage
| Sirikon wrote:
| Between sun and rain, guess which one is there more regularly
| nowadays.
| Razengan wrote:
| Do we also have to guess where?
| taftster wrote:
| Depends on your area. Both conditions are trending towards
| extremes. Some areas are seeing more rain that are
| traditionally sunny and vice versa even.
| timbit42 wrote:
| This year we've had 3 times the rain we usually have. My
| municipality puts a foot bridge in the river each spring and
| we're at the end of July and they haven't been able to put it
| in yet because the river is still too high. We're also getting
| more heat which increases how much water the sun draws up into
| the atmosphere creating clouds.
| lygaret wrote:
| I was very surprised these weren't piezo or turbine based, but
| rather harvesting voltage differences in the water droplets
| itself.
|
| Could a piezo collect current like this, on a solar panel sized
| sheet? I'd imagine it's not an insignificant amount of power
| during a downpour.
| ragebol wrote:
| What's the velocity and mass of a single rain drop? And how
| many fall in a square meter in an average year?
|
| Can't do this homework at the moment...
| mcdonje wrote:
| 1. Is a triboelectric nanogenerator similar to a piezoelectric
| component?
|
| 2. Would this work any better than a downspout turbine? I suppose
| that could also be wired in series.
| qbrass wrote:
| It's a miniaturized version of this:
|
| https://en.wikipedia.org/wiki/Kelvin_water_dropper
|
| The actual device is: https://arxiv.org/pdf/1309.2866.pdf
| mcdonje wrote:
| That's super interesting and not at all what I thought. Thank
| you.
| NuSkooler wrote:
| I would imagine these could ultimately be combined with solar.
|
| _insert why not both? meme here_
| koala_man wrote:
| This is already the case according to The Guardian. Imagine
| solar panels that generate 200W/m2 at night when it rains.
|
| https://www.theguardian.com/environment/2018/mar/13/rain-or-...
| Brusco_RF wrote:
| You're off by 4 orders of magnitude. These "rain panels"
| generate <<1W/m2 even in heavy rain.
| [deleted]
| teeray wrote:
| Isn't this ultimately just a really inefficient way of harvesting
| solar power?
| mabbo wrote:
| It's just such a miniscule amount of power.
|
| Do you want to know why you don't see power dams below a certain
| size and height? Because gravitational potential energy is not
| very much. And I say this as someone who gets more excited by the
| Niagara falls power station than by the actual waterfall.
|
| I also question their math claiming 200w per sq meter.
|
| https://www.insidescience.org/news/how-much-power-can-we-get...
| angry_moose wrote:
| I tracked it down in another comment, the 200 w/m^2 is the
| maximum output of the harvester, e.g. if you started spraying
| the panel with a firehose.
|
| In this case, the input energy available is ~4 orders of
| magnitude lower than that.
| Brusco_RF wrote:
| Seems misleading to even mention 200W in any capacity at all.
| crtified wrote:
| 200W PMPO !!
|
| (in reference to the ridiculous advertising tactics of
| cheap audio/computer speaker systems in the 1990s)
| psd1 wrote:
| The may be other planets where the economics work out
| better.
|
| Probably wouldn't want to live there. Replicants would be
| able to run their fridges, though.
| powera wrote:
| This is a bad idea and cannot possibly work as well as the
| commenters here are imagining it.
|
| But it is easy to say "this would be big if true" and difficult
| to prove "these cannot make anything close to enough electricity
| to be useful". So, we have a comments section filled with blind
| hype and hope, and little actual knowledge.
| [deleted]
| ejz wrote:
| Seems like not that much power. I guess you could build this into
| solar panels (some kind of coating?) so that they generate power
| when it rains too so that the percentage of time the panel
| generates power is higher. But would the decrease in efficiency
| justify it or would it decrease the overall wattage produced?
| Maybe in places where it rains a lot, like Seattle, that would be
| worth it to increase the percentage of time it is producing
| power?
| barbariangrunge wrote:
| That page has so many ads I actually got confused about what I
| was reading and what was an ad
| angry_moose wrote:
| So 25mm/hour (1") is a fairly heavy sustained rain. Terminal
| velocity of rain drops is on the order of 10 m/s. Volume of a
| rain drop is on the order of .5ml.
|
| Total rainfall volume per m^2 is .025 m^3/hour. This is
| approximately 500,000 randrops/hour or about 14 drops/second.
| Each drop has 1/2 * m * V^2 = 25 mJ of energy.
|
| So putting it all together, this is generating 25 mJ/drop * 14
| drops/second = .35 W/m^2, and that's only when its raining.
| (Edit: and this is assuming 100% conversion efficiency,
| which....no. Don't know anything about this technology, but
| probably cut that number in half again).
|
| Sounds a lot like Solar Freakin Roadways.
|
| Edit: Just a sidenote; back in college the best course I took was
| billed as a "Renewable Energy" but was really just a weekly set
| of unit conversion problems like this that proved how absolutely
| stupid most energy proposals are.
|
| We did focus a fair amount on real technologies like Wind and
| Solar (and analyzing the shortcomings like storage, which haven
| gotten better since ~2009). The professor took a lot of joy in
| shooting down ideas like this though.
| K0balt wrote:
| How are they claiming 200w/ meter^2?
|
| That seems like an utterly fanciful figure for kinetic
| harvesting, and AFAIK the droplet charge also wouldn't be
| enough? What am I missing here?
|
| "The peak power output of the bridge array generators is nearly
| 5 times higher than that of the conventional large-area
| raindrop energy with the same size, reaching 200 watts per
| square meter," Li explained, "which fully shows its advantages
| in large-area raindrop energy harvesting."
| slashdev wrote:
| And way more intermittent than solar. Seems like a really dumb
| idea.
| jurassicfoxy wrote:
| Not in the PNW!
|
| > A tourist arrives in Vancouver on a rainy day. He gets up
| the next morning and it's still raining. In fact, it's still
| raining three days later. He goes out to supper and spies a
| young kid. Out of despair, he asks, "Hey kid, does it ever
| stop raining around here?!" The kid says, "How should I know,
| mister? I'm only six."
| slashdev wrote:
| I lived in Vancouver for a number of years. I sure don't
| miss the winter. Otherwise it's a lovely part of the world.
| But the clouds and the rain really got to me.
| taeric wrote:
| Funny, but also very inaccurate for large parts of the PNW?
| Maybe it is always raining in Vancouver, but summer is
| remarkably dry in large parts of the area.
|
| Edit: Granted, the time of the year that solar is likely
| too spotty, we do have rain.
| e40 wrote:
| I was visiting a friend in the PNW and we went for a walk.
| Shortly after we started, the drizzle started. Honestly, it
| felt great, the drizzle on the face. My clothes didn't
| really seem to be getting wet, either, that's how slight it
| was. Then, he mentioned "the rain" and I looked at him.
| Dude, you think this is rain? He said, yeah, it rains
| harder, but they consider this rain. I questioned him a
| bunch and it seems much of the time the rain was at drizzle
| level.
|
| Now, this was in the 90s. I don't know if the rain is
| harder now, due to, you know, the changin' weather.
| taeric wrote:
| I think this is still very accurate. I tell folks from
| the south that ask if it rains a lot here, that they
| likely wouldn't call what we get rain. It definitely
| looks wet all the time in the winter. As if it always
| recently rained.
| kzrdude wrote:
| A drizzle is pleasant when it's warm but part of grim and
| cold weather when the temperature dips down (below
| 15-10degC?)
| taeric wrote:
| The other fun thing of the PNW is that it really doesn't
| get too cold that often. :D
| gottorf wrote:
| Average daily high stays under 15oC (~60oF) from about
| November to April. Definitely cold enough that being damp
| is unpleasant, especially with any kind of breeze.
| taeric wrote:
| Depends on the rain. We don't have the cold rain I was
| used to from the south. Such that I'm perfectly fine
| biking in all year and basically all weather.
|
| So you aren't wrong that it can certainly be unpleasant.
| But it isn't as bad as rain from where I grew up. By a
| long shot.
| kzrdude wrote:
| This same kid also walks around in Bergen, Norway
| jonsen wrote:
| No, the kid i Bergen is twelve.
| gottorf wrote:
| He didn't see sunny skies until he was already a man, and
| by then it was nothing to him but blinding!
| Tagbert wrote:
| An amusing joke, but while rain is frequent in the winter
| in the PNW (Pacific Northwest USA) the rain is often light.
| Seattle residents tend not to use umbrellas unless the rain
| is particularly heavy. It might not be a very good power
| source.
| civilitty wrote:
| All it took was a year and a half in Bellevue and I've
| never needed protection from the rain ever since.
|
| Now that I'm back in California I get a lot of weird
| looks in the office when I go out into the rain on
| purpose. It's a lot easier to appreciate the rain here
| when it's not raining nonstop for nine months.
| gottorf wrote:
| Come spend some time in the Gulf Coast! Rain here
| actually physically hurts, sometimes. Big droplets
| (though probably not as big as the ones in the Alaskan
| Panhandle[0]), falling at a very rapid pace, looks and
| feels like a curtain of water. It's not unusual to have
| an inch an hour.
|
| [0]: https://en.wikipedia.org/wiki/Ketchikan,_Alaska#/med
| ia/File:...
| milsorgen wrote:
| I get the same puzzled bemusement here in Idaho.
| Originally from the Oregon Coast I now relish a good rain
| and love a long walk through it.
| klyrs wrote:
| This was true 20 years ago. Nowadays, we joke about
| Juneuary and this year we had Maygust. Our summers are
| hotter and longer, winters bringing weeks of freezing and
| snow where I grew up expecting a single day of snow. The
| calm weeks-long drizzles of my childhood are gone, replaced
| with days-long "atmospheric rivers" called "monsoon" in
| warmer climes.
| gottorf wrote:
| Is Juneuary June in January or the other way around?
| klyrs wrote:
| June in January, and August in May. As a kid, we wouldn't
| expect to even _see_ the sun until late May.
| willsmith72 wrote:
| noooo i'm sure it's the opposite here. January in June.
| (very accurate in 2023)
| CrzyLngPwd wrote:
| Seattle rain festival; January 1st to December 31st.
| zardo wrote:
| 100% it's always raining here it's especially bad in the
| summer.
| grecy wrote:
| As a fun data point, the capital of Sierra Leone gets more
| rainfall in a single month than the PNW gets in an entire
| year.
|
| I was there in the rainy season, it rained harder than I
| ever imagined possible for ten hours a day, every day.
| Brusco_RF wrote:
| You sent me down a rabbit hole. Holy crap! The AVERAGE
| rainfall in Sierra Leone in August is over 600mm... 23
| inches!
| gottorf wrote:
| According to Wikipedia, the average August rainfall in
| the capital, Freetown, is over a meter (~42")[0].
| Tropical wet-and-dry climates, they're wild!
|
| [0]: https://en.wikipedia.org/wiki/Freetown#Climate
| Brusco_RF wrote:
| Freetown gets more rain in one August week than my town
| (Scottsdale) gets in a full YEAR
| mjhay wrote:
| Seattle actually gets less rainfall per year than any major
| city east of the Mississippi. It's just overcast and
| misty/drizzly a lot in the winter. Summers are bone dry.
| lackinnermind wrote:
| First engineering is an iterative process.
|
| Which means something that's engineered is made better by
| successive improvements from previous work.
|
| 2nd this is failing to consider different environment
| conditions and applications may make gathering energy from the
| environment in creative ways practical and useful.
|
| Not saying this particular technology will eventually be
| practical from a commercial standpoint, only wishing to state
| it's more than just 'will this technology easily solve global
| energy demands'.
| dojomouse wrote:
| Correct, but what the parent here presents is a theoretical
| upper bound. A working product wouldn't even get close. When
| the theoretical upper bound shows that something could never
| aspire to more than a vastly inferior alternative to existing
| proven technologies, the correct approach is to abandon it
| rather than invest in iterative improvements.
|
| I agree we should keep an open mind regarding creative ways
| of collecting energy from the environment. But we should also
| abandon those which are quickly demonstrated to have no
| meaningful potential _even if we were to perfect them_.
| eesmith wrote:
| > successive improvements from previous work
|
| The first iteration produces 0.5 units. The next produces
| 0.75. The third produces 0.875, then 0.9375 and so on. Each
| iteration improves on the previous, but no engineering will
| surpass the 1.0 limit set by fundamental physics.
|
| > may make gathering energy from the environment in creative
| ways practical and useful.
|
| There's no end of crappy ways to produce electricity. Get
| electricity from walking across the floor? Yep [1]. Get
| electricity from exercise bikes at the gym? Yep. Get
| electricity from plants? Yep [2]. "Solar Freakin Roadways"?
| Yep. [3]
|
| [1] https://en.wikipedia.org/wiki/Pavegen#Criticism
|
| [2] https://www.sciencedaily.com/releases/2018/12/18121209330
| 8.h...
|
| [3] https://en.wikipedia.org/wiki/Smart_highway#Solar_road_pa
| nel...
|
| > it's more than just 'will this technology easily solve
| global energy demands'.
|
| You know how I know it's not a "potentially game-changing
| breakthrough in energy harvesting"? The best place to use
| this is not in extracting power from rainfall but in ultra-
| low-head hydropower energy production. Let the water fall on
| the panel as drops, and extract power.
|
| The energy involved corresponds to a head of about 3m, so it
| needs to be more efficient than other ULH methods, which
| already exist.
|
| Yet there's no mention of that application in the article.
| It's not like I'm an expert on the topic, so I conclude this
| is a solution in search of a problem.
| dieselgate wrote:
| Heck it feels like the majority of my whole engineering degree
| was unit conversions
| geph2021 wrote:
| I'm wondering if the charge generated by a rain drop could be
| from its static charge, rather than kinetic energy conversion?
|
| Clearly storm systems can accumulate a large charge
| differential with the ground (i.e. lightning), but I don't know
| if that's the principle behind rain drop charge harvesting.
| Cursory googling[1] tells me electrostatic charge may be the
| source?
|
| 1 -
| https://onlinelibrary.wiley.com/doi/abs/10.1002/smll.2023015...
| angry_moose wrote:
| I'm getting well outside of my depth here, but some starting
| points:
|
| Rain drops have been calculated to charge up to about 1/50 of
| an esu (electrostatic charge unit): https://agupubs.onlinelib
| rary.wiley.com/doi/10.1029/TE040i00...
|
| Their paper is reporting 70V, so Joule/drop is on the order
| of 3.7E-11 J https://www.wolframalpha.com/input?i=%282.65E%E2
| %88%9211%29%...
|
| (many, many orders of magnitude below the kinetic energy per
| drop)
|
| It's important to note most of the research they've published
| is not using real rain, but laboratory generated droplets
| that is intended to push the harvester to the maximum.
| MadcapJake wrote:
| Yes, the TENG that they refer to in the paper is
| TriboElectric NanoGenerators
| https://en.m.wikipedia.org/wiki/Triboelectric_effect
| jrockway wrote:
| I feel like if we want static charges there must be some sort
| of potential difference between the top of a large building
| and the bottom during a thunderstorm. Probably not, though.
|
| While we're at it, can we extract any energy from lightning?
| Not sure if the blocker is being able to store energy
| delivered over a short period of time, or if it's the
| unlikeliness of a purpose-built structure being hit by
| lightning. Probably both.
| chmod775 wrote:
| > While we're at it, can we extract any energy from
| lightning?
|
| Wikipedia has you covered.
|
| https://en.wikipedia.org/wiki/Harvesting_lightning_energy
| jrockway wrote:
| Ah, excellent!
| dojomouse wrote:
| Love you for this! I had exactly the same "solar freaking
| roadways" thought, although at least that idea qualified by
| basic theoretical analysis of available energy and area for
| harvesting and conversion efficiency. It was an obviously
| terrible idea for other reasons :-) yet it still got a
| prototype...
|
| I wasn't sure about the droplet analysis so took your same
| numbers (25mm/h, 10m/s) and just worked out aggregate mass:
| 25mm over 1m^2 = 0.025m^3 = 25kg
|
| 0.5mv^2 => 1250J/h... so looks like we agree.
|
| And to add a simple economic analysis of why this is such a
| dead-end idea:
|
| Mawsynram, in India, is apparently the rainiest city in the
| world with roughly 10,000mm of annual rainfall - 10x the global
| average.
|
| A given rain energy harvesting panel, deployed there, would
| generate 500,000J/yr... or 0.138kWh. That's significantly less
| than what a typical rooftop 1m2 solar panel would generate in
| an _hour_ on a sunny day. 0.138kwh is worth around 1.3cents at
| 10c /kWh.
|
| A big roof might get you $1-$2/year. You couldn't pay to clean
| your roof for that. You couldn't even pay someone to answer an
| email enquiry about the install costs for your system for that.
| This solution would have to be VASTLY cheaper than _paint_ to
| stand a chance of being viable.
|
| There is a reason our existing systems to collect power from
| rainfall rely on vast existing landscapes and aggregation
| mechanisms (rivers) to concentrate the rainfall for us.
|
| It is - in my view - a dead idea.
| playa1 wrote:
| Wow, I totally forgot about solar fricken roadways. That video
| was 2014.
|
| Looks like they ended up getting over $6m in funding. I can't
| tell how alive they are but they received some FCC approval for
| the wireless connectivity in Jan 2022.
|
| "So you are saying there's a chance?"
|
| https://solarroadways.com/faq-funding/
| SoftTalker wrote:
| Yes it's just very, very inefficient solar power.
| zie wrote:
| But if you could combine it with a solar panel, using the
| same footprint somehow, then you at least get some output
| while the sun isn't shining, which would be better than now.
|
| I'm sure that's a huge BUT for an engineer currently, I'm not
| trying to say it's easy or even doable, but that's the only
| reasonable use I could see, if it's just a touch extra energy
| for a solar panel, I could see it as a value-add, if the
| added cost is low enough.
| mrguyorama wrote:
| I mean this is true of nearly every single form of power
| available to us, maybe excepting nuclear.
| SoftTalker wrote:
| Yeah true. Geothermal I guess is another one.
| presidentender wrote:
| Geothermal is nuclear with extra steps.
| zardo wrote:
| It's still stellar power, but not from sol.
| MadcapJake wrote:
| No this is more like each raindrop shimmying down the sky
| carpet and then poking the panel to deposit the collected
| static charge.
| standardUser wrote:
| "The professor took a lot of joy in shooting down ideas like
| this though."
|
| Gatekeepers of domain knowledge usually do.
| bathMarm0t wrote:
| Ah yes. Physics, the ultimate gatekeeper.
|
| If an idea doesn't work on the back of a napkin, it's done.
| Think about other approaches to the problem and get another
| napkin. I think that's what he's getting at. Analysis from
| first principles is hardly gatekeeping.
| mrguyorama wrote:
| If you think a system not passing the sniff test because
| basic physics shows it to be mediocre, your problem is with
| reality, not a physics professor.
| irrational wrote:
| I live somewhere where it rains almost constantly for 9 months
| out of the year. Solar panels are really only effective for the
| other 3 months. It would be fantastic if this was a real thing.
| LegitShady wrote:
| its not. this is solar roadways level shenanigans
| notyoutube wrote:
| https://www.pv-magazine.com/2023/05/04/construction-
| begins-o...
|
| I saw the construction of this thing by chance the other day.
| Is it so obvious it's a "shenanigan" if they're still
| researching it?
| LegitShady wrote:
| there have been other tests of solar roadways - the costs
| are abysmal, the durability sucks, the efficiency is
| abysmal.
|
| https://www.sciencealert.com/the-world-s-first-solar-road-
| ha...
|
| https://www.sciencealert.com/solar-roads-have-finally-
| been-t...
|
| https://interestingengineering.com/innovation/solar-
| roadways...
|
| I think its someone pocketing grant money, or stupid
| bureaucrats spending tax money/grants for green headlines
| that has allowed those grifters to continue bullshitting
| people into building these poor decisions as "tests".
| timbit42 wrote:
| It would likely make more sense to put turbines on the
| downspouts of your roof gutters.
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