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Solar powered LEDs... help!!?
tegwin - 17/12/09 at 09:15 PM

I had a thought...

Can anyone help me with the theory?

Basically I want to have an LED powered lamp outside my house which runs all night long. (so 15 hours max at this time of year)...

The solar panels total size can be no more than 500x500mm

I need to provide a reasonable amount of light, so 9Ws of LEDs will possibly be required...

The question is... Would I be able to store enough energy to run that LED all night long during the day with a panel that size?

hicost blade - 17/12/09 at 09:24 PM

Talk to Les at:

http://www.paceuk.com/

He will sell you a 1w LED that will blind you!

Much better for solar power

brianthemagical - 17/12/09 at 09:25 PM

Are you sure you're after 9w? That's alot of power.
Any idea what voltage you're planning?

tegwin - 17/12/09 at 09:33 PM

Im not fussed at the voltage really... Whatever is best for charging/powering the LEDs...

Its hard, I know how much light I want, but I cant work out how many LEDs I need to get it.. I think I need to buy some LEDs and try it!

But I think 9W might be a bit much as you say...

If we look at this a different way....

If I have 15 hours of darkness and 9 hours of daylight..... My solar panel must be no bigger than 500x500mm.... what is the most powerful LED I can use?

MikeRJ - 17/12/09 at 09:46 PM

quote:
Originally posted by tegwin
I had a thought...

Can anyone help me with the theory?

Basically I want to have an LED powered lamp outside my house which runs all night long. (so 15 hours max at this time of year)...

The solar panels total size can be no more than 500x500mm

I need to provide a reasonable amount of light, so 9Ws of LEDs will possibly be required...

The question is... Would I be able to store enough energy to run that LED all night long during the day with a panel that size?


Not enough power.

Solar insolation in the UK varies from a best of 5kWh/m²/day all the way down to 1kWh/m²/day. Solar panel efficiency is around 15% for pretty decent multicrystalline panels, so worst case (i.e. Winter) you will get around 0.25*1000*0.15=37.5 Watt Hours from your 500mm*500mm cell. That gives you about 2.5 watts for 15 hours.

If you have deep pockets you can get more efficient panels, but you won't get 135 Watt Hours out of a 0.25m² panel without solar collectors etc. which will likely be too large for your installation.

quote:
Originally posted by hicost blade
He will sell you a 1w LED that will blind you!

Much better for solar power


They are only bright because all the light is focused in one direction, not very useful for floodlighting.

Bluemoon - 17/12/09 at 10:05 PM

^^^ Totaly agree also have you seen the cost of a 0.5mx0.5m solar pannel.. Not cheap. I have a smaller 5W panel, that maplin do with charge controler and LED light might be worth a look. It's designed to charge a 6Ahr 12V gel cell, I bet this is to small for you, if you want 15hrs of light, would be find for a few hrs a day using the LED lamp they supply (300mA I think when I measured it).

The LED lamp they supply is very directional and not water proof (but this could be fixed by sliding it inside a polycarbonate tube, or lots of mastic!). We us it in our awning (yes we have a small caravan, sad eh), works well for that.

Maplin don't seem to sell the kit anymore..

If you can have a motion sensor light you could try

http://www.maplin.co.uk/Search.aspx?menuno=69689

Dan

[Edited on 17/12/09 by Bluemoon]

[Edited on 17/12/09 by Bluemoon]

[Edited on 17/12/09 by Bluemoon]

smart51 - 17/12/09 at 10:12 PM

quote:
Originally posted by brianthemagical
Are you sure you're after 9w? That's alot of power.


Not really, its like an energy saving bulb. For outside, 9W is not much at all.

snakebelly - 17/12/09 at 10:12 PM

does it have to be on all night, surely you could make a major power saving user a pir sensor to trigger it?

tegwin - 17/12/09 at 10:19 PM

No, has to be all night...

Check these out...

http://www.streetlamp-solar.com/

Interesting.... but not sure what happens when the "reserve" power runs out... it would never be able to catch up with itself again?!??

[Edited on 17/12/09 by tegwin]

Confused but excited. - 17/12/09 at 10:54 PM

quote:
Originally posted by smart51
quote:
Originally posted by brianthemagical
Are you sure you're after 9w? That's alot of power.


Not really, its like an energy saving bulb. For outside, 9W is not much at all.


My outside light is only 11 watts and it is fine as long as you only want to see where you are walking. It illuminates a 20ft square area and fitted in one corner about eight feet high.

mad4x4 - 18/12/09 at 07:29 AM

quote:
Originally posted by tegwin

Interesting.... but not sure what happens when the "reserve" power runs out...


well then lets see ----- They go out!

tegwin - 18/12/09 at 09:24 AM

quote:
Originally posted by mad4x4
quote:
Originally posted by tegwin

Interesting.... but not sure what happens when the "reserve" power runs out...


well then lets see ----- They go out!



Wow.. how did you work that one out? Do you have the formula etc you used? Would love to see them

hicost blade - 18/12/09 at 01:57 PM

quote:
Originally posted by hicost blade
He will sell you a 1w LED that will blind you!

Much better for solar power


They are only bright because all the light is focused in one direction, not very useful for floodlighting.


It actually depends which diffuser you use up to 120 deg is quite normal for a high power LED

You can't buy this kind of LED from your local Maplins!

Talk to Les at Pace UK give him the spec you require and he will sell you a very efficient high power LED with a wide angle diffuser that you will not be able to look into

He makes LED warning bacons for the top of high buildings to warn aircraft!!

It will cost you about £50 for the LED (1/5 the price of a locost)

Image deleted by owner

SeaBass - 18/12/09 at 02:33 PM

£50 for a 1W Luxeon star and optics. I bought sixteen from ebay for £10.

Not sure how you're driving the LEDs but they like a constant current @ 350mA if memory serves.

JC

hicost blade - 18/12/09 at 04:19 PM

^^ was just an example of a few high quality, high power LED's that are not concentrated light ^^