What solar panel type to power a conventional typical light bulb?
Saturday, July 17th, 2010 at
4:07 pm
I built a shed out back and I would like to install a solar panel to power a small light inside and outside of the shed. Or maybe just the inside. Does anyone have any advice and suggestions?
I’m confused now
Well, i plan on just using it when i go out to the shed and need a little light on to see inside at night.
Wow, so many great answers!
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Tagged with: shed • solar panel
Filed under: How To Install Outdoor Lighting
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You want to use as little power as possible, so do not use a regular incandescent light bulb. Most of their electricity is used for heat, not light. Use a CFL (twirly bulb) or LED bulb. You can get them in DC power, so you don’t need to convert the DC power (like a battery) to AC power (like what you plug into your wall outlet). They are more expensive, but will save you a lot of money in the long run.
How many hours a day would the light be on? Let’s do the math with 1 hour, you can multiply it by how ever many hours you need it.
15 watts x 1 hour = 15watt hours (wh). (If it’s 2 hours, that’s 30wh) Take that number and put it in a solar calculator like http://www.altestore.com/store/calculators/off_grid_calculator/. It asks how many days you want to store in case you have no sun, how cold it gets there, and how many volts. That will tell you how big of a battery. 2 days, really cold, 12V, you’ll need a 10ah battery, that’s really small.
Then it will ask where are you, to decide what size solar panel you need. Here in Boston, I need a 5W panel.
To make sure the battery doesn’t get over charged, you should use a charge controller.
15W DC CFL Light bulb (equal to 100W incandescent) – http://www.altestore.com/store/Lighting-Fans/Compact-Fluorescent/Compact-Fluorescent-Dc/Phocos-CL1215W-12V-15-W-Warm-CFL-Lamp/p1007/
6W 12V panel – http://www.altestore.com/store/Solar-Panels/1-to-50-Watt-Solar-Panels/Sunwize-SC6-12V-6-Watt-12-Volt-SolCharger/p4218/
12V 12ah battery – http://www.altestore.com/store/Deep-Cycle-Batteries/Batteries-Sealed-Agm/Universal-UB12120-12V-12AH-20HR-Sealed-AGM/p1996/
4.5A 12V charge controller – http://www.altestore.com/store/Charge-Controllers/Solar-Charge-Controllers/PWM-Type-Solar-Charge-Controllers/Morningstar-Charge-Controllers-PWM/Morningstar-Sunguard-45A-12V-Pwm-Charge-Cntrlr/p793/
Or buy one already made with solar, lights, and batteries built in – http://www.altestore.com/store/Lighting-Fans/Outdoor-Lighting/Sunwize-Solar-Outbuilding-Light-System-10-Watt/p4644/
My suggestion is to buy a solar powered shed light.
I suppose you could make one… figure out the maximum amount of time you could possibly need the light during a day, convert to hours… multiply that by the wattage of the light source you intend on using… that gives you a watt/hour rating for a battery storage device. Find yourself a solar panel with a voltage that’s usable for the circuit you are making, 12v usually or maybe 5v for led lights (but then there’s some circuitry that needs to happen to make that one work). You figure out the amount of sun you’ll get there on a short day (think winter solstice) in hours and then figure out how many watts your solar cell needs to put out to charge that battery from earlier.
Say you have a 18 watt/hour battery (12v) and a 2 watt solar cell (12v) and you get 9 hours on the solstice… see? 2×9=18
Now you need to put in an overcharge preventer, so you don’t overcharge the cell on longer days, or days you don’t use the light… and voila!
Or you can buy a solar powered shed light….
solar panels have very low output which is measured in wattage and the volts output are DC volts
so if your running anything household you would have to buy a inverter to change DC to AC household currant
so a little bulb in a car is around 18 watt
hope this helps
from a old timer
As a solar panel only puts out a couple of volts you would need several to power say an automotive bulb at 12volts. It is a rather expensive way of lighting your shed as you would also need a battery to store the power up as when you need the light it will be dark so the cell will not be working.
The interstate system uses a small solar array, about 12" x 12". You could contact them for info. Since you are only using one lightbulb, get a 24V one and then you can hookup to 2 12V batteries in series. If not, then you would have to go with an inverter to use standard 110V wiring.
Robin answer is the only one that makes sense. A solar panel can not power a light bulb without a storage vessel. A panel can store the current to a battery or two until needed then the dc light will save you money instead of buying a converter. Depending on your area a wind powered generator might be more efficient. OH a web site can be found at Mother Earth News. they have alot of sites for people wanting to go green even can help person who are wanting to go off the grid.
Hey Beef, I could talk for hours on this one. We wired an 80 foot barn recently for lights with nothing more than a 55 watt panel, some golf cart batteries and a $70 inverter. It has 5 compact flourescent spotlights inside, a small light over the door inside, and another outside. The little lihts are 12 volt, so they can be turned on straight from the batteries without an inverter. This might be all you need if you just want a light for a few minutes here and there, skip the inverter, go with a smaller battery and smaller panel. The most efficient lighting for something like this is a 12 volt LED strip. Sometimes you can find them at truck stops on the freeway for just a few dollars, or at an RV place. My favorite place for them is super bright led’s dot com, listed below.
If you have an old car battery, or better yet a deep cycle 12 volt battery, just shop for a small panel, maybe 40 or 50 watts. A 50 watt panel will put out 2.8 amps in direct sun. There is a rule of thumb that as long as your panels amperage is not more than 2% of the battery’s amp hour capacity, you don’t need a charge controller. You will need a diode however. A diode is nothing more than an electrical check valve, allowing the solar panel to charge the battery during the day, but not allowing the battery to discharge through the panel at night. Most panels today come with them already installed. A car battery could typically have anywhere from 50 to 90 amp hours of storage, so a small panel would work fine. Just hook the positive of the panel to the positve of the battery, and the negative of panel and battery together, and you’ll be charging. Now you can hook your lights up to the battery. Our installation uses mechanical timer switches for the small 12 volt lights. It is very important they not be left on all the time, they would run the battery down to nothing, and in a few days the battery would be toast. Inverters have low voltage disconnects built in, they shut off when a battery gets down to about 1/3 charge anyway. When we go into the barn, we just wind the timer switch up for a few minutes, then we can turn on bigger lights if we want. Then we reverse the process when we are leaving.
A good quality led strip from the website might cost you 10 to 15 dollars, but light up a work area on a table, but only use 2 watts. Another fun thing to do is use a small inverter to run led Christmas lights, they typically use 2 watts per string, so 2 or 3 of them is no biggie for an hour or two during a party. If you decide to put more horsepower in your little shed, look for Trojan T-105 batteries at any golf cart place in the phone book. They are 6 volts each, so you need at least 2, but they hold 220 amp hours, you can hook up to 80 watts of solar to one pair without any charge controller. Then with a 750 watt inverter for about $70, you can run drills, spot lights, small power tools like an electric weed wip or similar contraption. The one to steer away from is refrigeration. Seems like everyone I talk to that wants to do this considers putting a small fridge in their shed or barn before long. That reefer needs to be running 24/7, and it will take 5 times the solar power they have to keep up with it. Lighting is almost never a problem. I’ll put some sources below. Good luck, and have fun, Rudydoo
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