[Bernardo Mattiucci:]
>Con il mio staff abbiamo realizzato una piccola simulazione di una casa
>hi-tech illuminata a giorno con soli 100 W di potenza e utilizzando lampade
>gia' in commercio (http://www.lumileds.com/).
Uhm. Sono un fan dei LED bianchi e a tempo persissimo mi sto
progettando e costruendo una torcia a LED, pero` non li
vedrei tanto bene per l'illuminazione di una casa. Mi risulta
che la sensazionale efficienza dei LED bianchi sia una
leggenda basata su misurazioni errate: chi ha fatto le misure
di luminosita` non ha tenuto conto del fatto che i LED
emettono solo un fascio stretto, mentre le altre fonti di
luce considerate nel confronto la emettono in tutte le
direzioni...
Vedi ad esempio qui, e questa e`�gente che tra le varie cose
vende LED bianchi, quindi avrebbe tutto l'interesse a dirne
ogni bene:
Da
http://www.otherpower.com/otherpower_lighting.html :
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o 32 watt T8 fluorescent--85 to 95 lumens/watt
o standard F40T12 cool white fluorescent--60-65 lumens/watt
o compact fluorescents--low 30's to low 60's lumens per watt,
usually 48-60
o T3 tubular halogen--20 lumens/watt
o white LED--15-19 lumens/watt
o standard 100 watt incandescent--17 lumens/watt
o incandescent night light bulb (7w)--6 lumens/watt
o incandescent flashlight bulbs--dismal, less than 6
lumens/watt
But wait! What about all the white LED high-efficiency claims
that are all over...including the claims that used to be on
this site? Unfortunately, much of this information is
incorrect. Comparing the efficiency of a white LED light with
a compact fluorescent by measuring the intensity of a tiny
spot within the beam does NOT give proper efficiency results.
We got much of our data for efficiency claims from an article
in Home Power Magazine (click here to see this testing
article) and in literature from LED distributors. The
problem? All of the light from our LEDs is concentrated in a
20 degree beam, while the incandescent and compact
fluorescent lights were tested without fixtures...and most of
the light they produced was never measured in the test, since
it sensed only light falling on the sensor. It's OK to
compare different lights by how brightly they illuminate a
certain size area...but put a reflector behind the compact
fluorescent and incandescent bulbs in the test rig and the
data would change significantly. Therefore, while the LED
lights in this test may illuminate a small area as brightly
as other lights, they are NOT significantly more efficient.
LEDs can still be a good choice for illuminating your
workbench, for example, as long as the light cast onto your
small work area is as bright as you need--in this case your
LED light could be a good investment for saving power,
especially if your old incandescent fixture is also lighting
the rest of the room where you don't need the light (like in
the Home Power experiment link above). If you try and light
an entire living room with an LED fixture, though, you are
not saving much--in that case you want a wide dispersal of
light, and a fluorescent fixture would be the hands-down
winner for efficiency, cost and practicality.
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Sei sicuro che non convenga usare dei tubi fluorescenti?
Ciao
Paolo Russo
Received on Sun Aug 24 2003 - 21:33:29 CEST