There are some decent quality linear fluorescents with 12 vdc
ballasts on the market, too. I would consider a combined system: one
fluorescent for overall room lighting, and some LEDs for task
lighting around the perimeter. I don't like the LEDs alone, but mixed
they can be very effective. One advantage of Travis's suggestion, is
that the inverter will act as Low voltage disconnect on the higher
wattage fluorescent, but you could still have the LEDs on DC. Thus
the main light goes out, and tells everyone to go home, but the LEDS
let them know where the door is, and avoids total chaos.
R. Walters
Solarray.com
NABCEP # 04170442
On Aug 18, 2009, at 5:58 AM, Travis Creswell wrote:
I don’t have time to do the exact math but think a small inverter
and linear fluorescent is a clear winner of your trying to
adequately light the bulk of the class room.
Linear fluorescent has lumens per watt in the upper 80’s. CFL (DC
or AC) is upper 40’s and LED is the same as CFL and maybe a little
worse depending on whose products you are comparing. You’ll also
note that it’s next to impossible to get Lumens per Watt specs from
LED suppliers. It’s like the new car company refusing to publish a
MPG spec but readily waves a made up spec that alludes to MPG but
isn’t really. I’ve been asking the numerous LED manufactures that
call on me for samples so I can do side by side testing with CF and
LF and NONE of them call back a 2nd time so I’m really still quite
nervous about LED for “real” applications. Ok sorry about that LED
rant….LED’s are cool they are not the panacea they are being made
out to be,
Two evenly spaced fixtures that use a single 4’ tube will almost
adequately light the entire room of that size and use about 60
watts total. Total Lumens would be ~5400. Assuming the tare and
efficiency losses put the Morningstar 300 at net efficiency of
approx 85% that take our lumens per watt to something in the mid
70’s which is still much better then DC LED and DC CFL.
Best, Travis Creswell
Ozark Energy Services
From: [email protected] [mailto:re-wrenches-
[email protected]] On Behalf Of Walt Ratterman
Sent: Monday, August 17, 2009 5:34 PM
To: 'RE-wrenches'
Subject: Re: [RE-wrenches] Solar 12 volt DC lighting for school in
Haiti
Hello Lee,
Walt here.
I will be leaving for Haiti in about a week, and be there for three….
We have done lots of schools. If you are strictly 12V, your
choices primarily are 12V CF and LED lights. There are lots of
pros and cons to both.
The real question is what you intend to use the lights for.
If you go to our photo gallery (link from home page:
www.sunepi.org ), and check out the Sierra Leone gallery, you will
see some clamp-on LED Lights that are 12V and are used for night
time studying. They are pretty much task lights and are low level.
If you are trying to keep the system really small in terms of watts
of solar panels, (and cost) these can be great, but again – the
primary question is what will the light be used for.
A step up from that would be the 12V CFL’s. Might be tough to get
in Haiti (for replacements). I can check next week and let you know.
If you have any kind of distances involved, you will probably want
to consider an inverter (Morningstar SS-300 is great) to avoid the
losses associated with 12V dc wiring.
Feel free to contact me off line if you want to go over this some
more….
Thanks,
Walt
From: [email protected] [mailto:re-wrenches-
[email protected]] On Behalf Of Lee Bristol
Sent: Monday, August 17, 2009 2:53 PM
To: [email protected]
Subject: [RE-wrenches] Solar 12 volt DC lighting for school in Haiti
Can anyone recommend lights for a school in Haiti. I am going
there in a couple of months to install a 12 volt solar PV system
and need to illuminate seven 16 x 20 foot school rooms. I am so
confused by all of the light bulb options, base options, CFL vs
LED, what wattage is required, etc. I would expect that two
fixtures with bulbs would suffice for a room. Any ideas?
There is no grid power available…this is really out in the boondocks.
Thanks
Lee
--
Lee Bristol
NABCEP Certified Solar Designer/Installer
Chief Technology Officer
Standard Solar, Inc.
202 Perry Parkway, #7
Gaithersburg, MD 20877
(301) 944-5105
(240) 479-1510 (c)
www.standardsolar.com
_______________________________________________
List sponsored by Home Power magazine
List Address: [email protected]
Options & settings:
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-
wrenches.org
List rules & etiquette:
www.re-wrenches.org/etiquette.htm
Check out participant bios:
www.members.re-wrenches.org
_______________________________________________
List sponsored by Home Power magazine
List Address: [email protected]
Options & settings:
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
List rules & etiquette:
www.re-wrenches.org/etiquette.htm
Check out participant bios:
www.members.re-wrenches.org
