simple, cheap, shed system

2 Posts
Mar 30, 2009 09:06 pm
simple, cheap, shed system

I have a small storage shed (12' x 16') that I would like to install some lighting in.  It is not feasible to run an electric line to the shed.  My question is this:  is it possible to build a simple and cheap solar power system that would power 3 or 4 CFLs?

If I am only using the system to power lights can I omit a portion of the typical setup (skip the inverter and just use DC lights for instance)?  I would never run the lights more than a couple of hours a week.

I have seen some solar "shed light kits" but I need more than a single light and I would like more light output than these kits would provide.
220 Posts
Apr 1, 2009 04:49 pm
Re: simple, cheap, shed system

 hi marc,

 you kind of had me there by using the words "cheap" and "solar power" in the same sentence. but i see you posted on the 30th so it was not some april fools joke.

 kidding aside, this will be a great way to get your feet wet with renewable energy. the problem is once you start playing around with these renewables and see what you are capable of you won't want to stop there!

 for a bare bones workable system we won't need much.

a cheap group 27 marine rated battery can be had for about $50ish dollars.

 a small pv module (that's not a toy) like this one.

 and a few 12vdc cfl's like these.

 or these.

 add in some standard wiring and a few pull chain edison base lamp fixtures and you will be off to the races!

 with this size pv module and battery you can get away without any charge controller (staying within the accepted %2 standard) ie: group 27 battery is aprox 100ah X %2 = 2ah max for unregulated pv source. a 5watt module will max out at about 0.3amps- well within accepted practices even at double that. the module listed has nice 10 foot leads with a blocking diode built in.

 i would add an in line fuse here to the pv of an amp or two in the unlikely event of a diode failure in the shorted mode (very unlikely) as well as to the battery output (to the cfl's) if we use four of those 5watt cfl's and they are all on that's 5 X 4= 20watts/12volts=aprox 1.6amps those lamps have a slight startup surge so we might choose a 5amp fuse just to be safe in case we get a short somewhere.

 the expected output from the above setup should yield about 20 watt hours of power a day (at four hours of full rated sun) and be able to power all four of those 5watt cfl's seven hours each week, or two of them for 14 hours etc. we do want to try to get the module pointed perpendicular to the sun..just adjust it at around noon so you don't see a shadow around the frame and you should be good.

 comes to about $200 bucks, not cheap cheap but not soo bad...

 have fun, dave

edit: marc re-reading my post, i might add that it would be ok to go even a bit smaller with the battery..even somewhere around a 50ah trolling type battery would do the trick. i would not go much bigger than the 100ah though (here we run the risk of not being able to drive it to a full charge) my opinion only..find whats on sale.
« Last Edit: Apr 1, 2009 06:20 pm by david ames »
2 Posts
Apr 2, 2009 12:01 am
Re: simple, cheap, shed system

Thanks for the advice David.  I consider $200 to be pretty cheap especially considering what it would cost to run electricity to the shed.  I was pleased to hear that I can skip the charge controller as well with the PV module you suggested.

One last question.  Will I run into any problems if I wire everything with a standard AC house light switch instead of an edison with a pull string?  I'd like to place the lightswitch right at the door so I don't have to fumble in the dark for a pull string.
220 Posts
Apr 2, 2009 01:19 am
Re: simple, cheap, shed system


 a valid argument can be made against using an ac "only" type switch or even pull chain for this application. and for the purposes of this forum i agree that's not the right way..(the thinking was with such low currents it will not be a problem) but to do it "right" and for the record we should go with a rated switch. they go by the name of "snap switch" usually if they do not say ac only on them they are dual rated ac/dc. but to be sure we can get one that is expressly stated as being dc rated. heres some here.

 lots of good dc switches and plugs and such. follow the page links for dc switches.

 some interesting reading on the subject here.

kind regards, dave

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