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Power Science

Energy From Raindrops 144

Posted by ScuttleMonkey
from the don't-stop-the-rain dept.
conlaw writes to share that according to Discovery.com scientists have found a way to extract energy from rain. A new technique could utilize piezoelectric principles of a special kind of plastic to generate power from falling water in rainstorms or even commercial air conditioners. "The method relies on a plastic called PVDF (for polyvinylidene difluoride), which is used in a range of products from pipes, films, and wire insulators to high-end paints for metal. PVDF has the unusual property of piezoelectricity, which means it can produce a charge when it's mechanically deformed."
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Energy From Raindrops

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  • well, that's not exactly the galt engine, but it sure smacks of that sentiment.
    • Re: (Score:3, Insightful)

      by kestasjk (933987)
      (It's worth noting hydroelectric dams have been used for power generation for a long time now)
  • by buanzo (542591)
    One for the floor of your shower.
  • by Finallyjoined!!! (1158431) on Saturday February 09, 2008 @08:36AM (#22359436)
    The amount of rain we get here. :-)
  • Seriously though, Portland is trying to gain the title of the renewable energy capital of the United States and this would be awesome in the whole Pacific Northwest as they slowly ween themselves off the major dam systems they build up over the past 80 years.
    • by mangu (126918)

      Portland is trying to gain the title of the renewable energy capital of the United States and this would be awesome in the whole Pacific Northwest as they slowly ween themselves off the major dam systems they build up over the past 80 years

      Do you mean hydroelectric power isn't renewable? Hydro power *is* energy from raindrops, where do you think the water in the rivers came from?
      • by jdray (645332)
        We in Portland are (as a group) typical of the "think green" group, wherein we want to consume energy, feel good about where it comes from, and not think too deeply about the sensibility of it all. Oddly, solar and wind energy are good (this makes me happy, because I work for a wind energy company), but hydo is bad (think of the fish!). Few people stop to think that they're all forms of solar power. Furthermore, natural gas is okay for heating your home and making hot water, not to mention the popularity
      • Do you mean hydroelectric power isn't renewable?

        No, hydro is renewable, but it isn't cool. You can't have an old reliable tech and not expect treehuggers to bitch about it. I consider treehuggers a very small portion of the environmentally conscious population, treehuggers will only be happy when everyone lives in crappy mud brick communes and conserving water by only showering weekly. These are the very same people who bitch about wind farms disrupting the birds. I'm sure even solar furnace towers [wikipedia.org] will
        • by dgatwood (11270)

          The wind thing is pretty silly, I agree. That said...

          Those folks aren't wrong about hydro being bad. Hydro power creates lakes that end up burying lots of plant matter on the floor, which then rots and gives off lots of greenhouse gasses (methane, primarily). In fact, IIRC, at least one study concluded that many hydro power plants are less green than coal power plants because of the sheer quantity of methane released by those lakes.

          That's not saying that all hydro power requires creating huge lakes.

          • by mangu (126918)

            IIRC, at least one study concluded that many hydro power plants are less green than coal power plants because of the sheer quantity of methane released by those lakes.

            No, I don't think you remember quite correctly. At least, it's not "many" dams. That case you mention has been made for only one dam in the world, AFAIK [google.com].

            And do you know what would have been the simplest solution for that one? Let loggers cut the trees before the dam is filled. And burn the remaining brush, CO2 is not as bad as letting it rot t

      • where do you think the water in the rivers came from?
        Cow piss. Cow farts being the second greatest contributor to global warming, they gotta balance it out somehow.
  • These things don't generate much energy, but should be enough to power a perpetual tiny rendition of Gene Kelly' 1952 hit film.
    • Re: (Score:3, Funny)

      by 4D6963 (933028)

      should be enough to power a perpetual tiny rendition of Gene Kelly' 1952 hit film.

      Would that be "Watching 'Singing in the rain' in the rain"? That would make a catchy song! "I'm watching Singing in the rain in the rain, I'm watching Singing in the rain in the rain, what a glorious feeling, I'm happy again!"

  • meh (Score:1, Insightful)

    by Anonymous Coward
    Or just collect the water and run it through a water mill. WTF??
    • Re: (Score:3, Insightful)

      Because with this, you can just put them on the roof! Under the solar panels! Oh . . . wait, no. On top of the solar panels! No, that won't work either . . .

      Seriously, though, if it actually worked, it might be an alternative in a spot that gets enough rain / regular cloud cover to reduce the attractiveness of solar. I guess.

      • by mikael (484)
        You have a gutter below the solar panels on the roof. This collects the rain water and funnels it down a sprinkler onto the set of piezo-electric raindrop energy generators. This water then runs off down a couple of water-wheels before being collected into storage barrels, where it is gradually released and drives a micro-miniature water turbine.

        Imagine all the energy that is going to be created!!!
        • Re: (Score:2, Insightful)

          by DavidTC (10147)
          That's almost enough energy to hoist it up there in the first place!
      • by fbjon (692006)
        You can put it on the south side of the roof (for north hemispherians). Add a wind turbine [windside.com] or a few, and you've covered the majority of weather conditions.
    • by X0563511 (793323)
      Do both! Let the rain fall in a big pit lined with this, and let the water run off into a collection tank which feeds a watermill.
    • Re: (Score:3, Interesting)

      by TheGavster (774657)
      Collecting the water and running it through a mill only takes advantage of the drop from the roof to thr ground, where this device takes advantage of the larger drop from cloud level. That said, there's no reason that you can't line your collection pan with this stuff and still use waterwheels in downspouts. I'm also guessing that a waterwheel can do a better job of extracting energy than this plastic, so for taller buildings (closer to the cloud/farther from the ground) I can see turbines winning out.
      • Re: (Score:2, Informative)

        by MadnessASAP (1052274)
        I'd be willing to bet that a raindrop reaches terminal velocity in a very short distance making the difference in height between a roof top and a cloud irreleveant.
        • Re: (Score:3, Informative)

          Terminal velocity for raindrops is around 9 m/s [hypertextbook.com] (slower for smaller drops, like drizzle). Acceleration is 9.8 m/s/s. So big raindrops reach terminal velocity in 9/9.8 = 0.9 seconds, during which time they fall 0.5*a*t*t = 0.5*9.8*0.9*0.9 = 4 metres = 13 feet.
  • Whatever happened to water wheels? We have been using them for thousands of years.
    • by FroBugg (24957) on Saturday February 09, 2008 @08:54AM (#22359512) Homepage
      We upgraded to hydroelectric dams, which provide a very significant amount of power both in the United States and worldwide. China's still working on the Three Gorges Dam, the biggest ever.

      Unfortunately, the US is tapped out on hydroelectric. There really is nowhere for us to put in additional ones, and the ones we already have are often cited as concerns with regards to environmental impact and municipal water supplies.
      • by TheRaven64 (641858) on Saturday February 09, 2008 @10:10AM (#22359918) Journal
        Hydroelectric dams are not quite as good, in theory, as power from raindrops. The sun heats up water, which evaporates and forms clouds. These then fall a long way (lose a lot of potential energy, mostly turning it into kinetic energy and losing some as heat to air resistance) and are caught in a reservoir and lose all of their kinetic energy. They then fall a bit further over a turbine, but by this time they have lost most of their energy.

        Now, if you could build a completely frictionless waterwheel and put it underneath each raindrop, you would get a lot more energy than if you caught the same raindrop in a bucket and then let it drip onto the water wheel (which is effectively what a hydroelectric plant does). There are two problems with this idea. The first is that rain falls over a large area. The total energy from all of the raindrops is a lot, but the individual energy is quite small. The reason hydroelectric seems like a good idea is that, although you only capture a small fraction of the energy from each drop, water falls in to the reservoir from the surrounding hills, so you are capturing rain drops from a very wide area. Once you concentrate rain enough, your losses to friction become a lot less (try building a waterwheel that will spin when a single raindrop hits it, then try building one that will spin when you pour a bucket of water on it and see which is easier).

        This piezoelectric idea is quite neat, because it allows you to capture a significant proportion of the energy from each rain drop and convert it directly into electricity (although you'll probably lose a lot transforming it into anything that you can draw a stable current from). It has the same problem that the hypothetical rain-powered water wheel had, however, and the same problem solar power has: You need a lot of surface area to get a decent amount of energy out. If we assume that it is twice the power output per unit rain of a hydroelectric plant (water falling more than twice the height, but lower efficiency power conversion. Entirely made up number, but probably within an order of magnitude) then it will need half the area of the hydroelectric plant to generate the same amount of power. Note that this isn't just the area of the reservoir, it's the total area that rain falls.

        Some more back-of-an-envelope calculations:

        Annual rainfall where I live is around 1-3 metres (more slightly inland than on the coast). Let's say 2m as an average. Cumulous cloud (the kind that typically causes rain) forms at 2-16km. Picking a number somewhere in the middle, let's say 8km for the average distance rain drops fall. That means, every year, two cubic metres of rain fall 8km per square metre of ground. That's 2,000 litres, which means roughly 2,000 kg. The total energy in this is calculated as mgh, so: 2,000 x 9.8 x 8,000 = 156,800,000 J.

        That sounds like a big number, so let's break it down. Electricity is usually sold in kWh. One W is one J/s, so one kWh is 3,600,000J. That means this gives us 43.5kWh/year energy generation for every square metre of land we allocate for it (note: I am assuming 100% efficiency here, while I would be really surprised if it got 20% in the real world). The average household uses something in the range of 3-4MWh of electricity per year, so you would need 1,000 m^2, or roughly a 30x30m area of land per house. Assuming a more reasonable efficiency, you're looking at somewhere closer to 60x60m, which is still under an acre. Of course, you could probably combine this with solar energy, since solar power is pretty useless when it's raining and so you wouldn't need to supply the entire house's electricity with just this. If they can get efficiency to the 10-20% range, it seems feasible for a lot of uses.

        • by QuickFox (311231)
          It sounds to me like you'd get more energy from this material by having strips of it fluttering in the wind.
          • by Adambomb (118938)
            Why not both? Wouldnt a horizontal sheet have only a short list of vectors from which wind would cause no turbulence, so most winds would?
            • Wouldn't the pressure of the wind (assuming flurries of wind instead of a constant wind) do pretty much the same thing as the pressure of a rain drop? Put it on an angled roof and you'd get solar power, rain power, and wind power all in one. Use these things instead of shingles. If we could make these things tough enough then we could replace all sidewalks with these things and also make use of walking energy.
          • I'd like a shirt made of this stuff. It could probably provide enough to charge a cellphone, or a soldier's communications device.
        • by Aaron Isotton (958761) on Saturday February 09, 2008 @10:37AM (#22360114)

          Annual rainfall where I live is around 1-3 metres (more slightly inland than on the coast). Let's say 2m as an average. Cumulous cloud (the kind that typically causes rain) forms at 2-16km. Picking a number somewhere in the middle, let's say 8km for the average distance rain drops fall. That means, every year, two cubic metres of rain fall 8km per square metre of ground. That's 2,000 litres, which means roughly 2,000 kg. The total energy in this is calculated as mgh, so: 2,000 x 9.8 x 8,000 = 156,800,000 J.


          The calculation seems to be correct but the concepts don't hold.

          The *potential* energy of the rain can indeed be calculated using m*g*h as you said. The piezoelectric panels convert the rain's *kinetic* energy to electricity. The kinetic energy on impact is *not* equal to the potential energy, because most of it is lost to air friction.

          As others pointed out, the speed of a rain drop is around 8 m/s. This means that the kinetic energy of your 2t of water is E = mv^2 = 2000 * 64 = 128,000J. You're three orders of magnitude off.
        • by mindstrm (20013)
          Terminal velocity for raindrops appears to be about 20mph, or about 32km/h, or about 9 m/s and that's for extremely large drops in huge storms. They would hit that after falling for about 1 second.. so all that extra altitude wouldn't seem to be helping at all.

          Your calculation would the be 2000 * 9.8 = 19,200 J

          http://www.shorstmeyer.com/wxfaqs/float/rdtable.html [shorstmeyer.com]

          • A better idea, perhaps, would be a massive cascade of these things, angle slightly downwards, so that rain would hit, drip off, fall for about a second, hit another, drip off, etc. That distance is about 9/19.6=.45m. So for approximately each additional half meter, you are gaining another unit area.
            • The only reason this is better than one is because the rain that hits it has less drag force on it (D=1/2 rho Area v^2). You could cascade them so that the drops reach 8 m/s each time. That might be cool.
        • by ultranova (717540) on Saturday February 09, 2008 @11:23AM (#22360506)

          Annual rainfall where I live is around 1-3 metres (more slightly inland than on the coast). Let's say 2m as an average. Cumulous cloud (the kind that typically causes rain) forms at 2-16km. Picking a number somewhere in the middle, let's say 8km for the average distance rain drops fall. That means, every year, two cubic metres of rain fall 8km per square metre of ground. That's 2,000 litres, which means roughly 2,000 kg. The total energy in this is calculated as mgh, so: 2,000 x 9.8 x 8,000 = 156,800,000 J.

          Unfortunately, this is wrong. A raindrop doesn't keep on accelerating all of these 8 kilometers; it will reach it's terminal velocity, at which point the deceleration due to air resistance exactly cancels the acceleration due to gravity. Since raindrops are small, their surface area is large compared to their mass, so I'd imagine the terminal velocity to be rather small - which is a good thing, otherwise we'd get our skulls crushed to powder by rain, but sadly means that we can't extract all that much power from a single raindrop.

          Actually, I checked, and according to WonderQuest [wonderquest.com], the average speed of a raindrop is between 2 (for small ones) to 9 (for large ones) meters per second. Since kinetic energy is mv^2, this works out to between 2000kg * 2m/s * 2m/s = 8000J (= 0.002 kWh) and 2000kg * 9m/s * 9m/s = 162 000J (= 0.045 kWh) per square meter per year.

          Since the price of electricity is about 0.07 euros per kWh where I live, and a square meter of this thing would need about 22 years to produce a single kWh under optimal conditions and assuming a 100% efficient conversion, I don't think that it is a good investment.

          • Re: (Score:3, Informative)

            by ultranova (717540)

            Hups ! That should be 0.5*mv^2. So the above figures are twice as good as they should be - it's going to take 44 years to produce a single kWh per square meter :(.

        • Re: (Score:2, Interesting)

          by maxume (22995)
          The distance that the raindrop falls is irrelevant when calculating the energy available when it hits the ground -- the velocity is what matters. You are imagining that you can capture the entirety of the potential energy that the raindrop contains before it starts falling, when in reality, you are limited to capturing the kinetic energy it contains when it lands. So if air resistance happens to slow the drop down, you are losing energy well before the drop ever gets to your system. Googling says that the t
        • Problem: not all of the GPE will get converted to kinetic. A raindrop is pretty small so it will, I think, have a low terminal velocity. Hence after a relatively speaking short distance, it will lose GPE to friction rather than increasing its speed.
  • by hyades1 (1149581) <hyades1@hotmail.com> on Saturday February 09, 2008 @08:53AM (#22359510)
    If they put this stuff on the floor around the urinals at my local bar, we could meet Canada's energy needs for the next hundred years.
    • I tip my hat to you sir, I was just going to post the same thing. I read the summary and thought to myself, "does this work with piss?" I am sorry that you managed to post about it first.

      Seriously, though, this could be a very revolutionary technology for areas that have a lot of rainfall and not much sun. I my area you could put rings of this stuff under the trees and power the whole place.
      • by hyades1 (1149581)

        Ah, a Left Coaster, I'm guessing. I have friends and relatives out there. Pale, stoned people who seem to have a lot more fun than me.

        This does seem to offer some promise. It would take quite a while, I'm thinking, to slow the planet's rotation by making use of the kinetic energy of raindrops.

        And I don't doubt you'd have beaten me to the post if I hadn't noticed just last night how nice it was to have worn waterproof winter boots to the pub.

    • Re: (Score:3, Funny)

      by couchslug (175151)
      "If they put this stuff on the floor around the urinals at my local bar, we could meet Canada's energy needs for the next hundred years."

      If they trapped the runoff from under the urinals at your local bar, they could sell it as American beer.
      • YEAH??? Well... shit, you're right. U.S. beer *is* like making love in a canoe: Fuckin' close to water. Damn it, the truth hurts.
  • by xzvf (924443) on Saturday February 09, 2008 @08:59AM (#22359536)
    Anything that moves can produce energy. The point is how much and at what cost to capture and reuse or store. I can solar panels on my roof for about 15K that averages about $120 a month. About a 10 year payback. A wind turbine that generates about 20% of my needs would cost 5K and have a payback of 15 years. Strapping a motion generator to myself and family to produce enough power to charge cell phones doesn't appear to ever justify the initial cost. Raindrop system.... call me when it costs the same as a shingle.
    • by iamhassi (659463)
      "Anything that moves can produce energy. The point is how much and at what cost to capture and reuse or store."

      Mod parent up. He's exactly right. I'm tired of hearing about all these hairbrained schemes to find new sources of power, only to read it costs thousands to implement and only creates a couple kilowatt an hour (if that much!), compared to just buying it at the rate of 7 to 10 cents per kWh.

      That's why we don't have water wheels [wikipedia.org] on all our drain spouts because you'd never recoup the initial i
    • by Presence2 (240785)
      ROI is not the only consideration for alternative energy. Quit asking "what's it in for me" while looking at your wallet and go visit a stream near a coal plant, or take a deep breath in a city, or look at the evening news about Iraq and ask yourself what the ROI really is. You sir, are exactly why we have these problems in the first place; cheaper is not always better.
      • by bendodge (998616)
        Clean energy was killed by the very environmentalists who tout it. I was talking to an engineer recently who worked on nuclear power plants, and he told me about a plant somewhere (can't remember the name) that planned to build 6 cores. I can't remember the exact numbers, but the cost went up exponentially every time they finished a core because of the paperwork and regulations. The first core cost millions; the last would have cost hundreds of billions. They had to quit building at three cores, but if the
    • by FooAtWFU (699187)

      Anything that moves can produce energy. The point is how much and at what cost to capture and reuse or store. I can solar panels on my roof for about 15K that averages about $120 a month. About a 10 year payback.

      Yeah, about that. Does that include your opportunity cost, where you could put that $15k in a very very safe FDIC-insured 4% savings account / CD / money market account, and make $50 a month off it? Then that's more of a... 18-year payback. (Longer if you can get a better return off of riskier investments. Like stocks, and bonds, and such.)

  • ... but whether this means it really produces power from water vapour, or is an idea they cannot implement is unclear.
  • Let's build a very large vat. I mean it has to be huge. Then collect lots of rainwater in it, and stick a mechanism that changes outflow into something that can be used to spin a generator. Boom, electrical energy from rain!

    Of course this is still just indirect-indirect-indirect solar power, as always. But jeez, do you have to make things so complex by default? Is this the "innovation-promoting" effect of patenting?
    • by foxxer (630632)
      I can't tell if you're being sarcastic or not, but didn't you just build a dam on a nice canyon-y river?
      • Of course I'm not sarcastic. Would you not buy a used car from someone named "skulgnome"? Hm? Do you have something against gnomes? "Diminutive jews", I heard someone say.

        The device I described is of course known as ELECTRORAINIMATOR in the civilized (i.e., non-US) world. It has been the trade secret of my family line for the past four centuries.
      • by p4ul13 (560810)

        Let's all give Foxxer a big round of applause. If there's anything that's funnier than a science joke, it's somebody explaining a science joke to everybody who already got it.

        Take a bow sir!

    • Is this the "innovation-promoting" effect of patenting?

      This thing captures (some of) the kinetic energy of the falling raindrops; this energy is lost in your vat.

      I wonder how this material stacks up, in terms of cost and surface area per generated Wh, against a vat up on a pole with a water wheel and a generator. Hey, you can even combine the two: shingle your roof with this new material, and put a small generating turbine at the bottom of the drainpipe. Even so I doubt that you can generate signific

  • I have one powered by a generator attached to my knee joint. One to a string vibrating in the wind outside. One to my hamster. I'm seriously running out of cell phones by now. I'm starting to feel guilty not using more of this green energy.
  • by Ancient_Hacker (751168) on Saturday February 09, 2008 @09:32AM (#22359688)
    Hmm, raindrops... Why didn't someone think of this before? For a good reason:

    • Let's be generous and assume it's raining all the time.
    • And it's a real gully-washer, say an inch an hour.
    • And let's be really generous and assume this gadget captures 50% of the energy of falling water.
    • And each raindrop is at maximum terminal velocity, about 10MPH.
    • So that's about 700000 gallons of water per day per acre falling at 10MPH.
    • Which works out about 6 million pounds per acre per day at 10MPH.
    • Which is about 100 million foot-pounds per day per acre.
    • But that's only 1157 foot-pounds per second, barely 2 horsepower.
    • Roughly 750 watts at 50% efficiency.
    • Or roughly 17 milliwatts per square foot.
    • Or at ten cents a kwh, it's making almost 100 watt-hours a year, or almost a penny.
    • Re: (Score:3, Interesting)

      by baadger (764884)
      Another way of looking at it is a 1 inch puddle of of water covering 1 acre is going to weigh approximately 100 tonnes. Falling at 10 MPH, (~4.5 m/s) and using E = 0.5mv^2 the maximum amount of kinetic energy here is approximately 1 Megajoule, which over an hour is about 280 watts.

    • by Yetihehe (971185)
      It would be better to collect all this 700 000 gallons of water with some roof installed several meters high and run water turbine with water falling down. Of course you have then 700000 gallons of water per day, which you can slightly filter and you hve drinking water. Pure profit, and no ???.
    • Re: (Score:1, Interesting)

      by Anonymous Coward
      Wow, I'm still unsure whether you intentionally mixed the largest amount of different not easily convertible units together, or that's just the way it is when calculating with antiquated measures.

      To recap: inch/hour, miles/hour, gallons/(day*acre), pounds/(acre*day), (foot*pound)/(day*acre), (foot*pound)/second, horsepower, watts, kilowatt*hour, watt*hour/day

      Sure, with metric measures the list would be just as long, but you would find the same units used everywhere instead of switching between inches, miles
    • by Fizzl (209397)
      Furlongs per fortnight?
  • I would think the most obvious application would be as a lining for highway and rail beds, maybe even sidewalks and streets in some places. True, the variations in traffic load would determine your capacity for a C/B analysis to decide where to install the systems but if the carbon cost to manufacture the material is offset by the by the "carbon-less" power generated (discounting vehicle consumption), then why not take advantage of all that free vibration? I can see where this might be able to generate su
    • by fluffy99 (870997)
      Snicker. What ever energy you could leach from passing traffic, just gets added to the power requirement of the traffic. Would you reduce gas mileage by 0.5% just to make a couple hundred of watts? You're likely to expend more energy creating this magic material than it will ever produce in its lifetime.
  • This energy is just drops in the bucket compared to what they could get from lightning.
  • by p4ul13 (560810) on Saturday February 09, 2008 @09:50AM (#22359790) Homepage

    ...this breakthrough comes after failed attempts to generate power from roses, whiskers on kittens, bright copper kettles and warm woolen mittens.

    These are a few of those researchers favorite things.

    • by LuxMaker (996734)
      Actually the researchers were tired of singing the same old song, "Raindrops keep fallin on my head." and decided to convert their irritation to energy.
  • THE RAIN
    --found in Architect's Creek Hut, Westland Nat'l Park, New Zealand

    It rained and rained and rained
    The average fall was well maintained
    And when the tracks were simple bogs,
    it started raining cats & dogs

    After a drought of half an hour
    We had a most refreshing shower,
    And then most curious thing of all,
    A gently rain began to fall!

    Next day but one was fairly dry
    Save for one deluge from the sky
    Which wetted the party to the skin
    And then, at last, the rain set in.
  • by Grond (15515) on Saturday February 09, 2008 @10:11AM (#22359920) Homepage
    A typical raindrop has a fall velocity of about 8 m/s [madsci.org]. Assuming a pretty healthy rainfall of 10cm (4 inches) we get 100 liters of water per square meter of land. 100 liters of water weighs 100kg, of course, and plugging that into the equation for kinetic energy gives us 6400 joules. Spread out over 2 hours, that's a whopping .89 watts per square meter.

    All of that assumes 100% conversion efficiency and no losses due to standing water absorbing the impact of the drops. If the overall efficiency is, say, 50%, then you'd need something like 30 square meters to light a single compact fluorescent bulb. To generate a megawatt would require over 2 million square meters (over 500 acres).

    Given that in most places it rains less often than the sun shines, this seems like an astonishingly inefficient way to generate electricity. There just isn't that much energy in rainfall.
    • Re: (Score:2, Insightful)

      by noidentity (188756)

      Given that in most places it rains less often than the sun shines, this seems like an astonishingly inefficient way to generate electricity.

      But it's a great way to generate research money.

  • Just imagine: if this stuff panned out, it would not only be rain that could deform it. It could be deformed by say birds walking on it (toughen it against claws). So instead of cities trying to actively chase pigeons away (some places chase them on the ground with dogs and in the air with falcons, etc.) and the "don't feed the pigeons" signs - you would instead see "feed the pigeons right HERE." (where the special plastic is). Hopefully they get some of that rain working for them to, to wash the pigeon poo
  • This is more newsworthy as an arcane Rube Goldberg method of extracting energy than as anything remotely practical. You could extract more power by implanting braces of dissimilar metals in the mouths of two teens, then forming a battery when they kiss.
  • Collecting the heat energy of the gasious output of your local politicians would gain much more energy for free. You only have to convince them to speak into the pipe of your selfmade heatcollector instead of the microphone.
  • by haeger (85819)
    Obviously I didn't read the article, what kind of slashdotter would I be if I did that, but what's with the focus on rain? Why not put something like this where there are lots of people moving about? Shopping malls, trainstations, airports... I'm not sure how much energy it produces but it might be enough to justify the cost. Also it would be locally produced electricity, something that's very high fashion right now.

    .haeger

  • Now, if they could get energy from steam, THAT would be vaporwa... oh wait, nevermind.
  • This stuff would be great for my lighted clear plastic raincoats!

    www.clearplastic.com

  • Um, don't we already do this? I mean hydroelectric dams harness the power of rain as it flows from higher elevations to lower elevations.
    • Well yes, but _if_ it could be done efficiently and on a sufficient scale, wouldn't it be a second bite at the cherry? First you could get the piezoelectric effect as the rain hit the 'ground' then secondly, once it had been channeled get the second bite at the dam itself? OK all it may ever be (due to those laws of thermodynamics) is an offset rather than a net gain in our energy requirements but maybe that is better than nothing? Personally I think we have the technology (which will improve in efficiency
  • It seems quite possible to harness power from rain. We can harness the sun on a sunny day for solar energy. We can harness the wind on a windy day for wind energy. We can harness the ebb and flow of the oceans based on the moon's position for tidal energy. So why not harness the rain on a rainy day, the snow on a snowy day, or lightening on a stormy day?

    Two things to consider is location and time of year. Imagine solar and wind energy powering much of Arizona during the dry season and weather energy
  • I thought about using piezo material years ago. Weather dependent energy devices are iffy at best, wind and solar are too intermittent. Why not harness all the sidewalks, roads, dance floors where vehicle and foot traffic abound. Feet pounding the pavement seem more reliable that raindrops.
  • "the unusual property of piezoelectricity, which means it can produce a charge when it's mechanically deformed"

    What, never had a crystal radio? Kids these days. Piezoelectricity isn't so unusual. You can go buy many products using it. Even at outfitters (read: outdoors and camping stores) you'll find plenty of devices using piezoelectricity. Given that we've known about it from the late 1800's that isn't unusual either. Some sugars, bones (let them dry first), ceramics, and many crystals are piezoelectrical
  • Let's see - I smell vinyl, I smell flourine, I smell all kinds of crap in there. Generate a few hundred square miles of that crap, and I wonder what the slag, pollution, run off, waste, and other toxic crap making polyvinylidene difluoride would require.

    Oh, but that's right: electricity for my 52 inch plasma screen is more important.

    RS

  • by miracle69 (34841) on Saturday February 09, 2008 @09:34PM (#22365782)
    Power Surge, baby. Power surge.
  • ...it would be far much easier to just build a dam and a waterwheel to harness the energy of rain.
  • by Eivind (15695)
    This is extremely silly. There's not much energy there, larger amounts can be gathered trivially.

    Falling raindrops reach terminal velocity after aproximately 5-10 meters, assuming they're the large type. Tiny raindrops reach terminal velocity after something like -1- meter.

    So, if you could somehow collect the entire energy (not possible most of it goes into heating the drop as it's vigorously stirred on impact) you'd have collected the same energy as for the water falling perhaps on the average 3 meters.

    Let

I have never seen anything fill up a vacuum so fast and still suck. -- Rob Pike, on X.

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