Piezoelectric - Rain water

A piezoelectric device as a rain impact force sensor, maybe. There probably are easier ways one can measure this force. Using a piezoelectric device as a electric power source from falling rain, no.

In other words, a hydroelectric dam...

Piezo film has no electrical response unless it is being impacted, flexed, relaxed or otherwise disturbed.

So, once a cushion of water builds up, no more response.

Dam good answer.

Yes you could, it's called "picowatt energy harvesting", but you're at least 6 years late to the game. Here's a paper to get you started:

http://www.ferrodevices.com/1/297/files/APicowattEnergyHarvester-document.pdf

Use your favorite search engine to get more info.

Yes, though one of these does a more efficient job:

Which is the modern equivalent of one of these:

Why not use something (on a small basis) to catch rain and direct it over a wheel connected to a generator. They call this low-head hydroelectric, and there are quite a number of designs by now, including things that look sort of like wind turbines running under water.

You're allowed to do that down there? I understand some western states won't let you catch rain water any more. May short the neighbors down stream.

State Rainwater Harvesting Laws and Programs

Arizona | Arkansas | California | Colorado | Hawaii | Illinois | Nevada | North Carolina | Ohio | Oklahoma | Oregon |Rhode Island | Texas | Utah | Virginia | Washington | U.S. Virgin Islands

The city of Portland claims it owns the rainwater that falls and harvesting is prohibited in the city.

Sounds like a bunch of Crack Heads or some other form of Draconian A-hole runs that town. They are welcome to it, and hope they drown in it. I guess they own G.D. air too? WTF! These people are worthless.

Wait till you run into "viewshed". It's a term that means, if I can see it then I have the right to say whether or not the property owner will be allowed to modify it.

If I set up a swing set where my neighbor can see it, he can sue me for the loss of his unobstructed view. The city has regulated some areas that a change to the appearance of a property requires permits and approvals and you can be fined if you don't get them.

How do they stop fog, rain and plant growth from obscuring the view?

Those are natural, organic and "picturesque", therefore OK.

They don't acknowledge God, so they don't require him to get a permit.

They will fine you for cutting down a tree.

So if the neighbor complains when you cut down a tree on your land that is threatening to fall on your house, what happens if you plant several poplar saplings in their driveway?

If you didn't get a permit to cut the tree, you get fined.

When the poplars get high enough to see, they can complain and get them removed, but only after you get a permit.

"It's for the kids."

Sounds like parakeets fighting in the evening hours over who gets the top perch to me. For God sakes, take turns!

Viewshed: the view out from inside my shed. Looks good to me. Somebody watched too many episodes of "Bonanza" where the Cartwrights were sticking their nose into everyone else's business. The day they start that crap down here in Texas, there's gonna be more than tires burning.

A quick search reveals 32 places are named Portland. Which Portland location claims all of the rain water that presumably flow into municipal storm drains?

Well, all of them can go take a flying leap, AFAICT or care.

Portland, Oregon, home of the homeless campers, plastic shopping bag free and troubled by unpicked-up dog poo.

Beaverton also claims the water. For the rest of you, Beaverton is the first suburb west of Portland Oregon.

Sounds like we hearken back to the days of Range Wars, water access, and barbed wired fences. It's all fun and games until somebody gets hurt.

Sure, but is it worth it? I have a 3500 sq ft flat roof, 25 feet off the ground and one day after a few beers I wondered the same thing. Would it be worth harnessing the energy in the rain falling on my roof? It was easy, straight forward calculation, square footage, inch of rain, weight, then horsepower conversion. 33,000 foot lbs per minute, 745 watt hours. It really didn't turn out to be much. Even my solar array put out almost as much power on a cloudy day as the rain on my roof... Now if you had a skyscraper, 1000 foot of head, that might work!

e=mgh

h = 300 m

Say you want 1 kWh (= 3.6 MJ)

3,600,000 = m x 10 x 300

m = 3,600,000/3000

= 1200 kg (=2650 lb)

So you would need 1,200 kg of rainwater from the top of a skyscraper to generate 1 kWh. That, out of interest, is almost exactly what it takes to run my dishwasher, once.

So from a skyscraper roof of about 40 x 40 m you could run my dishwasher about 50 times for every 25 mm of rain (less for efficiency losses of course).

Translation: So from a skyscraper roof of about 130 x 130 ft you could run my dishwasher about 50 times for every 1 inch of rain.

It is simpler to use rainwater to turn a turbine and generate electricity. By damming the flow in a reservoir we also ensure continual power without continual rains.