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re: solar assisted interior lighting
10 mar 2002
n. thornton wrote:
>hi nick.
hello n,
>dimming filament light bulbs does not save a great amount of energy,
>as a given drop in energy use produces a much greater drop in light
>output.
god spoke to me last week, saying "change the sanctuary floodlights
to compact fluorescents!" so i did, but i only changed two of them,
lest the more substantial and possibly more powerful building and
aesthetic committees speak to me next.
i replaced 2 75 w floods near the back of the room with 2 23 w philips
dimmable cfs. at the same luminous output, they use 1/5 the power with
5x the efficiency and 5x the lifetime:
sylvania 75 w flood philips 23 w cf
rated output 940 lumens 1500 lumens
power consumption
at rated output 75 watts 23 watts
power consumption
at 940 lumens 75 watts 15 watts
lifetime 2,000 hours 10,000 hours
these cfs ($19.95 at home depot) lose less efficiency than incandescents
when dimmed. they still shine bright when the floods on the same dimmer
are nearly invisible. the 940l/15w spec came from a curve on the philips
lighting website. it corresponds to about 63 vs 65 l/w at full brightness.
>and you're shining lihgt on the ceiling, so you'd be better to just dim
>the ceiling lights, not all of them. that would produce more energy saving.
we'll see... the cfs are not floods, so they don't aim at the beige floor.
more of the light hits the white walls... the aesthetics committee will
probably start talking about "glare."
>if its 20' away, why use a flat mirror? 2 or 4 flat mirrors giving x2
>or x4 concentration would surely achieve more.
the same amount of light at greater cost, with 2-4x more motors and
controls? this could provide more uniform illumination and be more
interesting, art-show wise, with several spots on the ceiling, and
the heliostats would be closer to a final home product.
>1kw per square foot? i thought 1kw per sqaure metre was more like it.
duane figures sunlight is about 100 w/ft^2, but half of that is ir, and
incandescents are only 4% efficient. go figure. btw, sunlight has about
twice as many lumens per watt as the best fluorescents, which is a good
thing in summertime.
>you would achieve still more energy saving by adding a flat mirror
>under the windoww to reflect skylight in. at first glance it doesnt
>look so eficient, but...
this art show requires more pizazz, imo. have you tried this on the north?
>finally there are some other tricks you can do to much improve your
>electrical energy savings.
do tell. btw, we have a demand meter.
nick
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