Jim Cathey <mailto:jim.cathey...@gmail.com>
March 15, 2018 at 8:55 AM
Basic physics will sit off to the side and laugh at your antics.
Basic physics cares not.
-- Jim
Curley McLain <mailto:126die...@gmail.com>
March 14, 2018 at 10:44 PM
Ah Grasshopper! Basic physics and real science can be denied if
there are big bux to be made! And it helps if you usta be high placed
in the goobermnt. (Albore)
All ya have ta do is claim 97% of scientists agree, and bully (and cut
off goobermnt funds to) anyone who disagrees! (Albore)
If we wanna have downspout turbines, all we have to do is start a
goobermnt program and fund it. Majikally, the "science" will appear!
Jim Cathey via Mercedes <mailto:mercedes@okiebenz.com>
March 14, 2018 at 10:19 PM
My only point was that drip hydro can't even generate that much power!
So unless these static films cost at most pennies, _and_ didn't cut down
_any_
on the solar flux, they're utterly pointless.
Basic physics will not be denied.
-- Jim
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Max Dillon via Mercedes <mailto:mercedes@okiebenz.com>
March 14, 2018 at 7:28 PM
Science!
OK Don via Mercedes <mailto:mercedes@okiebenz.com>
March 14, 2018 at 6:50 PM
I hate to "rain on your parade", but if it sounds too good to be true:
Myth 2: Rooftop / Downspout Hydro
A second common microhydro-electric scheme that we are often asked
about is
the viability of putting turbines on a home’s gutter downspouts to
generate
electricity from the rain. Some imaginative folks know enough about hydro
to understand that the energy has to come from somewhere (in this case,
from the forces of nature), and that the height of the roof can contribute
head (pressure) to spin that turbine.
The mistake in this scenario is a simple and honest one of scale. While
some hydro units have been designed that can function on low head, such as
from the roofline of typical homes (and even lower), a hydro turbine’s
power output is a product of head *times* flow. And it is a lack of
significant flow that is the defeating factor in the power equation when
relying on rooftop rainwater collection. The watershed drainages for even
small streams are usually measured in thousands of acres or square miles.
Home roofs, even big ones, are measured in mere thousands of square feet.
Let’s look at example calculations for a large house in a very rainy
place—Seattle, Washington, gets about 40 inches of rain per year, with
November being the rainiest month at an average of about 6 inches.
Let’s assume that a tall two-story house would give us a 25-foot-high
roof,
and thus 25 feet of head. This 6,000-square-foot home has about 3,000
square feet of rainwater collection area (remember, it’s two stories).
That
means that in November, this house would receive about 1,500 cubic feet of
rain, or 11,220 gallons.
If that rainfall came as a constant drizzle all month long, flow from the
roof would be only about 1/4 gallon per minute. Currently there is no
turbine on the market to work with that flows that low, but using our
microhydro power formula (see sidebar), we could theoretically get 468
watt-hours that month.
*0.26 gpm × 25 feet ÷ 10 derate = 0.65 watts × 720 hrs./mo. = 468 Wh*
So even if there was a nanohydro plant that could harvest that small flow,
it would result in less than 1/2 kWh of electricity—per month!—and only 3
cents worth of electricity in Seattle. It’s a tiny fraction of what
even an
energy-efficient, 6,000-square-foot home would use in a day, not to
mention
a whole month.
Would the available energy increase if we weren’t dealing with a constant
drizzle? What if, to increase flows to a usable rate, and hopefully
increase viable energy production, we could hope that all that rain
came in
a great deluge of 1 inch per hour (a 100-year storm, in Seattle) over six
hours! At that unlikely amount of rain—practically all at once—flow from
our example roof would be about 31 gpm. That is a more viable flow
rate for
hydro turbines on the market and gives us a projected power production of
77.5 watts, but only for those six hours. The total of 465 Wh per month is
about the same energy as the drizzly example above (the minor
difference is
from rounding significant digits).
This is when inventive thinkers will begin planning for taller homes, or
additional rain-collecting roof areas, and tanks to hold the water for
release all at once to increase flow. But even that 11,220 gallons of
water
that falls on our 3,000-square-foot roof that month would weigh almost 47
tons if stored. Imagine a structure at roof level capable of supporting
that kind of load just to generate a minuscule amount of energy. And
remember, these discouraging energy production numbers are for the
rainiest
month, in one of America’s rainiest cities. Other months, other
places, and
smaller houses can only deliver worse performance.
In this case, it would be better to just spend the money on a PV
system. To
put things into perspective, even in Seattle, which gets only an
average of
1.7 peak sun-hours per day in November, an inexpensive (less than $100)
15-watt PV module would make close to the same amount of energy as the
proposed rooftop hydro system.
https://www.homepower.com/articles/microhydro-power/design-installation/microhydro-myths-misconceptions
On Wed, Mar 14, 2018 at 6:17 PM, Andrew Strasfogel via Mercedes <
mercedes@okiebenz.com> wrote:
