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By TarjeBargheer
I moved to the city a couple of years ago, and have noticed how clean the roofs always are. No leafs get up there. Further, from every roof there runs a pipe all the way along the edges of the roof, and to the ground in order to make the rain that ends on the roof go to the ground without pouring down on the windows.

My idea is simply to put a little mill inside the pipes that go from the roof to the ground, the mill should run a simple generator in order to produce power. - Since the roofs are always clean in the city, the problem of dirt accumulating in the mill is not an issue.

It wouldn't be much of an extra cost to produce such pipes, since both the generator and the mill are easily made out of few raw-materials (plastic for the mill, and some copper and magnets for the generator).

There is quite a lot of square meters of roof in a city, and if these pipes were installed as a replacement of the old ones when the roof should be renewed anyway, it would propably accumlulate a neat amount of energy (although not nearly as much as a dam!).

Reward: A sample of the product?
By Rishi
Good idea. Any idea for a renewable energy source is welcome.
There are some issues in this case.
1. The power is generated only when it rains.
2. Output is variable depending on the intensity and duration of rainfall and height of pipe.
3. The generated voltage will vary.
4.Some form of regulation and storage will be needed.

For a 5cm dia pipe of 15 metres height flowing full, the power generated will be about 100 to 150 watts. Considering the intermittent production of power even the cheapest system will prove uneconomical.

Still it is the thought of conservation that is important. Power from rain water may turn out to be important. In a sense that is what all hydro-electric generation is. It really is power from rain water.

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By CodeThumper
I think this is a good Idea also.

How does water flow in a city? Where does it go? Maybe a larger generator could be fitted in to the system under the city with turbines large enough to avoid garbage or other things that get washed down the drain.

The power may be able to be fed to a power transfer station?
By Rishi
Using a city drainage is likely to be more effective. Different cities have different approaches to storm water handling. In low rainfall areas the drain may be linked to the sewage system. In high rainfall areas storm water drains usually get linked to some nearby stream, which drains into a lake or a larger river.

Since there is no dam as such what is needed is a low head hydel generator. Such a generator can develop power that can be fed into a power grid. A UN sponsored project has come up with suitable designs for upto 50 to 100 Kilo Watt power is what I remember.

By Daryl666
1 issue with installing it in a single downpipe for a house is the small flow of water (it there is not enough water flow at the same time the water just goes through and doesn't turn the turbine) this could solved by allowing for a storage tank say like 10 gallons to be above the turbine near the top with a automatic switch to allow the entire tank to empty down the pipe then close the valve when the flow is no longer suitable for the turbine.
By Daryl666
this would work with the storage and would be ideal for taller buildings. it would have to be a turbine suited for extreme head pressure (head pressure is determined by the height the water falls in the pipes b4 the turbine) but suited to extremely low flow. i know the exact name of that type of turbine but cant remember it at this moment. it would only work for like a 100 - 350 watt turbine and only for large tall buildings. Alas this world needs every bit of renewable energy contribution it can get.
By DirtpatchSmacky
The turbine would have to be geared to such a low ratio as to be allmost useles, there is allmost no pressure behind the water in a downspout, cant think of what the mathematical formulea would be, but something along the lines of gutter mass(if completely full) times resevour mass(water on roof, if constant) times gravity at turbine height. for the turbine to be geared to produce anything but negligble amounts of energy, the resevour mass would have to be along the lines of sustainably holding 40 times the amount the gutter can hold per foot untill it reaches the turbine. so if the gutter, per foot was capable of holding one cubic foot of water the resevour would have to hold 40 cubic feet, then multiply that by the linear feet of the gutter,, say 10 running foot, times 1 cubic gallon per foot, is 10 cubic gallon, so the resevour would have to sustain around 400 cubic foot of water. when the water in the resvour got down to about 100 cubic foot, there wouldnt be enough pressure to power the turbine, if geared to produce noticable amounts of juice.i am far from a mathemetician or energy turbine theorist, so these numbers may be flawed,, but they should be close.
By DirtpatchSmacky
one very easy way to help the conservation effort when it come to spill off from roof tops, get a ten gallon bucket and a 55 gallon drum, cut a hole in the top of the drum 3 inches in diameter smaller than the bottom of the 10 gallon bucketdrill a bunch of holes in the bottom of the 10 gallon bucket, small enough that pea gravel wont fall thru, fill the 10 gallon bucket half way with pea gravel to act as a filter for large items like leaves, then simply place the 10 gallon bucket over the hole in the drum, set it so the gutter drains into the bucket then filters thru to fill the drum with water. use this to water house plants outdoor plantings etc. i built a system like this when i lived in chicago, one of the ladies in the building made a nice lattice screen to hide the setup so it wasnt so uglly, at one point we had 5 55 gallon drums full of water, so we used a sump pump to water the lawn after a long dry spell
By bayon forte
Collect all the run off in a water tower as high as possible.
Then have the water drain from a larger diameter pipe say 2" that
is reduced gradually to say 1/4" jet stream and have a little turbine generator at the bottom.If used along with solar and wind it could help charge a battery bank.
By GadgetmanKen
Perhaps you could build a water wall generating station. By this I mean you could start with a reservoir water collection stack of tanks. In the bottom of each water tank you would have a large bladder for air. As the tank fills with water it also compresses the air in the bladder. When the tank gets full of water it bypasses to another. When the first tank fills with water, a second, or third, or however many are likely needed could be used to hold extra usable water. Now there are several options. The water could be held for power gerneration and use, now, or later. First the air pressure would power a generator and when the air runs out, the water starts to flow out to a different generator and run into a second tank. The trick with the multible tanks would be that as the air flows out, the air goes into another bladder to prime and the water goes into the same tank and starts the process all over till it reaches the lowest tank and the maybe into an underground storage tank or to waste, all by gravity.
By simply me
if power from water is derived from height and mass. could rain energy from falling from the clouds of 13000m be collected to componsate for lack of mass on a rain drop?

can anyone think of a way to collect this energy?

how much rain falls per metre sq in our rainer countries, say Ireland, does anyone know?
By asesh
How nice? Frankly I also thought this for a while and still think it is practical. I wish we do a 'go ahead'.
Higher the building and bigger the quantity of rain water collection higher the energy. Yes, if there is no rain, no power.
If we can store the water high and calculate the rate of flow to be enough for the next rainfall, then are we ont taking care of the continuity?
The narrowness of the rain water pipe will determine the flow rate and that should actual the power generator.
Question is do we have such tiny miniature water turbine? Dynamo to create power? Rest is only feed into the regular electrical lines with appropriate metering.
I think we have an idea.
Let me get your encouragements.
By innoventor
I am completely enamored with this idea and have been obsessing about it for some years now. I spec'd out some stream generators when I was at the Real Goods Solar Living Center in Hopland California several times -- Harris Turbines, Pelton Wheels, something called the "Jackrabbit" stream generator, but they were out of my budget at the time (over $1,000). They looked simple enough though -- one website I checked out showed how some folks built a micro-hydro generator with a rewound alternator and some spoons. Their advice was to focus on the way you set the nozzles (like the Harris Turbine I saw at Real Goods they split the main source of water into four jets at right angles around the wheel.) Having no experience in rewinding alternators or generators I let the idea sink. But last year, when I visited the waterwheel section of the Deutsches Museum (the big science museum) in Munich, I got a chance to see exhibits on the history of waterwheels and hydroelectric power with great working models spanning a thousand years. Some of the models were small (so that visitors to the museum could learn the principles) and it seemed to me that one could power a small turbine with the amount of rainflow that I see coming off of roofs here in Germany from 3 or 4 story houses (like ours in Westphalia).

My wife and I have a 400 watt small wind turbiine (the Air403) and in mild winds it produces 75 to 100 watts, which is fine for keeping the batteries charged when the sun isn't shining on our PV panels. Given how much it rains here in Germany I can't imagine why we shouldn't let the roof rain do some of the charging. It really doesn't matter to me that this concept may not be economical for profiteers. Home security is what we are after, particularly because we've had power outages when the fierce storms knock down power lines, we are always in a conflict with Russia over gas prices (which they monopolize) and we had a near terrorist attack in the Essen train station. My attitude, especially with a newborn on the way, is "let's make our homes as disaster proof as possible".

While we can't afford to do more than install the vacuum tube heat pipe solar hot water system and composting toilet we are buying right now, next year some time I will splurge for a small pelton wheel or harris turbine and try this idea out. I think we will try the idea of the poster who suggested we first run the water through a 40 liter filter bucket and then a 200 liter drum. Meantime, if any of you all has any experience and can recommend the best small water turbine, so we don't waste time and money, it would be much appreciated!

Let's go ahead with this, as asesh says!


T.H. Culhane
By qasidsafeer
Since an average person uses 150L of water per day, why not rig your little turbine to the main waste water pipe at the bottom of high rise flats?
By theNay
One day in my electronics class, we were discussing the Big Hydro dam projects here in Wa state- my instructor had worked as a technician at one of them- breaktime, I asked him about if It would work to do this at home- and of course he said "not enough water". However, I never did think he was right about this issue- he isn't exactly a "think outside the box" kind of fella. Anyway- too me it seems like a no-brainer- it Has to work..just a matter of coming up with the most efficient way to harvest and store the power. Sure, the big hydro projects dam up big rivers and create big reservoirs- but they are also intended to power the Entire City of Seattle- and the rest of the NW. So, the small amount of rain on a roof should be able to harness small amounts of electricity. This gets me thinking- as others have mentioned- it does not rain every day, so the reliability is dodgy- however, the large scale hydro projects face the same problem in regulating the amount of water in the "lakes" created by the dams....and balancing this out with rainfall,snowmelt, and water needs. So, as others have suggested, collection of the rainwater into a water tower seems like the ideal solution to having control over when power is produced. I believe this idea bears further exploration.

I Love the idea of harvesting hi-rise runoff- it could create a whole new look architecturally.

Incidentally- I was dismayed to find out that in my city, rain barrels are Illegal! the city actually believes that they own the rain....I have heard that this was true elsewhere- but now they got me mad enough to build a secret rainbarrel/reservoir/hydropower plant in my backyard! they actually tell the citizens of the need to conserve water- while declaring rainbarrles illegal! insanity! anyway- anger is a powerful motivator for me to get stuff, I will be back, to learn, and pass on anything I learn.

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