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Rainwater used to generate electricity


March 26, 2014

The three young inventors of the Pluvia system, which uses rainwater runoff to generate electricity

The three young inventors of the Pluvia system, which uses rainwater runoff to generate electricity

When we complain about the rain, other people will often say "Yeah, but it's good for the plants." Well, thanks to a microturbine-based system created by three students from the Technological University of Mexico, it's now also being used to generate electricity for use in low-income homes.

In a nutshell, the Pluvia system – developed by Omar Enrique Leyva Coca, Romel Brown and Gustavo Rivero Velázquez – uses the stream of rainwater runoff from houses' rooftop rain gutters to spin a microturbine in a cylindrical housing. Electricity generated by that turbine is used to charge 12-volt batteries, which can in turn be used to power LED lamps or other small household appliances.

The generator measures about 2 inches wide by 10 inches high (51 x 254 mm), and receives the water through a half-inch (13 mm) pipe. Once the water has flowed through the microturbine, it proceeds to pass through a charcoal filter and into a storage tank, leaving it "equal to or cleaner than the water in the network supply system of Mexico City," according to the students.

The Pluvia system has already been tested in Mexico City's Iztapalapa community. The university now hopes to increase the power of the system, allowing it to generate a greater amount of electricity.

Source: Investigación y Desarrollo (Spanish)

About the Author
Ben Coxworth An experienced freelance writer, videographer and television producer, Ben's interest in all forms of innovation is particularly fanatical when it comes to human-powered transportation, film-making gear, environmentally-friendly technologies and anything that's designed to go underwater. He lives in Edmonton, Alberta, where he spends a lot of time going over the handlebars of his mountain bike, hanging out in off-leash parks, and wishing the Pacific Ocean wasn't so far away. All articles by Ben Coxworth

something tells me the amount of electrical power generated by this system would be absolutely minuscule.


Why can't I have this at my house used with solar cells, wind turbines to make me partially energy independent?


Charcoal filter not required, you could achieve this: ""equal to or cleaner than the water in the network supply system of Mexico City," by passing it through a sock!!


Maybe the power generated per household is small but what about collectively city wide? I've always wondered why nobody has installed generators in toilets.

"Electricity generated by that turbine is used to charge 12-volt batteries, which can in turn be used to power LED lamps or other small household appliances."

You see, they make no suggestion it will power the house.

Righteous Indignation

Miniscule power might be overcome by stacking a bunch of units, maybe. I wonder about junk in the incoming water. One leaf could do a number on a 1/2" pipe, much less a microturbine with its teeny blades. The flow rate will be governed by the charcoal filter below. The amount of electricity created will depend on rainfall, which peaks in Mexico City in July and is less than 5cm per month October to April. Similar generation projects using interior sanitary piping have already been proposed, so this is not an invention, rather an adaptation. It is an interesting project, but I don't see much future in it.

Bruce H. Anderson

Adrien, it depends on how much rain volume your area experiences. I can see that this free source of energy would be a fantastic green upgrade to many homes and commercial buildings in Vancouver, for example. Further, buildings could have their rooftop drainage systems tailored to direct runoff to fewer and larger diameter down-pipes; thereby increasing flow to larger capacity turbines. The idea that filtered water could also be created is great but that's not our problem in a city whose North Shore mountains experience 110 inches of rain per year.


Install these micro generators in the water supply lines to every home, everywhere!

Steven Schnitzer

i can;t believe a simple photovoltaic wouldn;t

a. generate more energy and

b. be a lot cheaper per kw or kwh



Power = Flow X Pressure ...or... Watts = Litres per Second X Vertical meters from the turbine to the surface of the water X gravity (use 9.81)

From a "low-income home" presumably single story and fairly small roof area, the power produced here would be tiny, but it might just counteract self-discharge of the battery.

Stacking them wouldn't work because the first one uses up all the pressure.

"Green" shouldn't be mentioned if you're using chemical storage. And thankfully they haven't mentioned 'green' themselves.

I have 10 micro hydro turbines, stacked, $14ea, from aliexpress. This is running my lights, usb outlets, fan, radio, bug zapper, (in-car) DVD player. No batteries, 24/7 free power, and super-green. Not everyone has a nearby waterfall though.

I also have a turbine connected to my toilet sistern that powers an exhaust fan as the sistern refills. Something everyone should have. Maybe these guys can adapt their product for this.

Matrix Key Systems

@ Steven A. Schnitzer Each turbine would use up pressure. So the city would have to drive the pumps harder, or there wouldn't be any water pressure at the end of the line.

This product would produce more energy if the downpipes acted like tanks, which would allow pressure build-up. Without pressure, flowing water has very little energy. Pressure only comes with altitude, not volume. Maybe run a pipe uphill to a neighbours gutter? Or to a communal rain collective roof on top of a nearby hill, with a pipe down to each household?... with a rain storage tank??... acting like a battery?? a non-chemical battery... now we're talkin'

Matrix Key Systems

Pie in the Sky Dreams You will never get payback out of the investment. Only slightly better than the absurd idea also from mexico for burying pneumatic pumps in the road for cars to activate as they drove over. this sounds like a final term project for engineering students. There was one a Mac Master university a couple of years ago withe winning prize going to a generator mounted on a door. the shame of it was all of the really good projects that were passed over because of "Greenness" of the entry.


While this is an interesting idea it fails economically. The output will be too small and inconsistent, only when it rains plus someone will have to maintain it. Scaling this up and placing it in a nearby stream or river with a continuous source of water would at least have the potential to break even cost wise. For the intended purpose of this invention, tiny windmills would make more sense. In most areas the wind blows a lot more than the rain pours. I have always been amazed at how much electricity we think we need versus how much we really need. It's so much cheaper to use mechanical power than to use electricity. Most small appliances have a mechanical predecessor. When we do need some electricity, a small hand cranked generator would beat this rainwater scheme.


Lets look at some numbers: Assume a height of 12 ft, assume 2000 sq ft roof area and assume this is in an area of heavy rainfall, so a foot per month. This yields 2000 cubic feet off water at roughly 64 lbs per cubic foot, at a height of 12 feet, each month. Assuming perfect efficiency; no restrictions, no head loss, etc, the most that could be generated is 0.28 watt-hours per cubic foot of water falling 12 feet. That equates to 0.56 KWhr per month. One KWhr in many places costs far less than a dollar, and it would take two months to get just one, even assuming perfect efficiency in a rainy climate. A real system for the parameters assumed would be lucky to generate much more than a dollar in a years time. Payback isn't realistic.


I think a waterwheel would produce more energy from the small flow of water.

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