May we assume that the staircase is exposed to the sun? If it isn't, then the solar panel will have to be mounted remotely and wires run to the individual lights and batteries. Not much of a better option than using ordinary lighting, except for the power consumption. If the staircase is exposed to the sun, then there are many sources of stand-alone, solar-powered lighting. Search the internet.

I intend to mount Solar panel on the terrace. I will require suitable solar panel to generate enough KWh for the LED lights to remain on for 24 hrs., battery, charge controller and constant current circuit for the LEDs. We approached many companys who are ready to offer the system with CFL instead of LEDs, but the lights can remain on only from dusk to dawn. This also works out to be quite expensive. Where can I get find the circuit design leads for LED lighting? Presently we use 8W CFLs to save electricity.

I've yet to see a Solar LED so I guess you mean that your lighting system uses LEDs for lamps and solar energy to power it.

I'm not sure about how many LEDs you need. You need to determine how much light you need in the staircase and then calculate how many LEDs will be required per fixture.

Next your solar energy system needs storage batteries to enable it to operate at night. You need to determine how much power your lights consume and calculate how much battery time you need. Then you design your power circuit to provide power to the lights and charge your batteries at the same time. Also consider that a cloudy day will reduce your solar cell's output. You'll have to compensate for those eventualities.

I have just installed some three watt LEDs (mine are in GU10 220 volt format, but you can get them in a 12 volt version too), mine are warm white as against the blue white ones, but they are also available for €1,- each less.

The LEDs come in two main versions (apart from voltage) one has 3 x 1 watt LEDs, that give a wider dispersal of light, each of the 3 LEDS covers about 30°, but altogether at about 7 foot distance, you get a nearly 4 foot ring of strong good light. €39,95 each.

The other one uses a single 3 watt LED and has a 60° coverage. I did not buy this one as it was even more expensive than the other. €37,95 each.

Ones using up to 60 LEDs are cheaper in MR16 format for 12 volt usually around €19,95 each..

MR11 are even cheaper, but have significantly less light output. Also 12 volt operation.

You will have to work out how many LEDs per floor are needed to be installed, add up the total wattage needed, double it and that in conjunction with the sunlight expected on your shortest day (halve it) will give you both your storage needs and the size of the needed solar array.

To get maximum efficiency, you will need to have a solar array that can track the sun each day (and it should not go crazy when it gets dark!!!! I have seen that happen....some years ago!) for maximum charging.....

I would say as a general rule, double your needed storage and expect half the amount of sunlight. Also use a proper charge controller to make sure on sunny days you are not likely to overcharge and therefore gas your batteries......

ONLY use "leisure" lead acid batteries.....not car batteries, if you don't know why, ask me.

I am a solar fan. Try Backwoods Solar electric systems.

www.backwoodssolar.com They have the LED lights and will

help you design the system.

Good luck,

James

You need to compare the cost of the Solar panel, plus all installation costs, with the total power you will save by powering those LED's off the grid..

We sell solar panels, and would be glad to sell them to you...

However, if it's strictly the energy savings you are looking for, I think most brilliant minds on here would suggest just sticking with the LED lights powered on the grid..

When the cost of the solar system comes down, and their efficiency is improved, it may be viable in the near future.

Now, if you just want a 'Greener" building, and don't mind that that initial cost will never be recovered, by all means, go fo it...

I would suggest getting a company that is actively selling the systems to help you lay it all out, and then ask others to bid on that same system..

I would get 4-5 bids if I were you, obviously from us as well, and then decide your best option.

Also, if you wanted a better alternative to the 8 watt CFL, we can offer you an 8 watt CCFL, (which means Cold Cathode Fluorescent Lamps).

If these need to be dimmed, we would offer you the Litetronics brand, as they dim well, but are much less light output that some other brands we carry..

If dimming is not required, we have another brand that is as bright as a 60 watt 130 volt incandescent, while only consuming 8 watts..

These little lamps are rated at 20,000 hours, so that would at least save you

two lamp changes as those cfl bulbs only last around 6,000 hours as opposed to the advertising claiming 8-10,000 hours... NOT....

We also sell all the LED products you could ever need..

Donald

Donald, Why do you use bold?

Gwen, I suppose I use bold because it's easier for ME to see, plus for emphasis.

If this offends you, or others, i will stop using it..

Donald

I suggest adding IR detectors to the system, so that only the zones where people pass by are powered.

This will reduce the amount of used power significantly and with this you can reduce the size of your batteries.

Excellent and useful addition.....

Just a thought, but is it not possible that the IR sensors will consume more power than the LEDs ? I suggested PIR sensors for a childs night light project a few years ago and the client was quick to point out my energy error.

I cannot believe that personally as I have an IR burglar alarm in my caravan that has 4 x AA Alkaline batteries. It spends at least 3 months of the year switched on, I change the batteries every 3 year or so, but they are still able to supply the siren, which is 110 db....

It may be a factor of the design and range( mine is only 6 meters if I remember correctly) and I have never measured the current taken by it I have to say, but as they are PASSIVE Infra Red, does that not imply usually a small current usage?

I am willing to break into the circuit and measure it also, but I would guess that the measurement is not made continuously, but probably made say once a second to save power, for example.

I believe it has a potential free contact as well, so if it was available locally, it might do for the job of switching the LEDs on EXCEPTING, it runs 24 x 7 and ignores whether it is daylight or not, an important factor in battery usage.....for the LEDs I mean...

I stand corrected - Just googled PIRs and the first one I found consumed 500mW on AC supply. If this was used to trigger several 3W LED units, it's easy to see the potential saving.

No problem.

Although I knew from the alarm that it used a PIR and ran for several years quite happily on 4 x AA, I had not really thought about it much, so it is nice to know from your web research that generally speaking at least, PIR sensors are economical enough to make them useful in other battery powered systems.....

A significant factor to consider is the distance between the solar panel(s) batteries and load.

All these distances need to kept to a minimum to ensure efficient operation.

If you are stringing your LEDs over 8 stories the panel (i'm assuming here that the solar system will be on the roof) will be (in my opinion) too far from the load and you will get too much voltage-drop.

This can be reduced by using better quality cable, but with the rising price of copper these days this will be an expensive option.

Each 3W LED each light will consume (according to my calcs) 0.25Amps @ 12Vdc.

With only one light per floor you have a 2 Amp load.

Assuming 10ft per floor the return distance of the circuit is at least 8x10x2 = 160ft.

If you were to use 14awg cable you will get 8.4% drop. That may not sound a lot but this will double if you use 2 LEDs per floor. Also if you want a fancy cable run (ie following the banister) then cable distance and thus voltage drop will also increase.

Sorry to be a kill-joy but best to find these things out in the planning stage!

Hi Ian,

You raise a really good point that needs to be considered carefully and taken fully into consideration at the planning stage.

My personal thoughts are to increase the size of the cable, at least near to the battery in the area where the maximum current will flow, say the top 3 stories. Then you could go down a cable size for the next 3 and down another size for the last two....

I am of course assuming that changing the thickness will show a good saving on cable costs, but if the cost of thick cable all the way down is not so terrible (bought on ebay for example) then I am all for having the thick stuff all the way down.....

Amortization will have to be calculated here.....I would say within 3 years if possible....5 at the worst.

As it is low voltage (12 volts I assume to keep the price of the LED lamps cost effective), you could in fact use some surplus 3 phase connecting cable (of thick enough purposes and use a pair for the bottom 3 stories and a pair for the top 5 stories (and a single one in reserve!) and you only need to run that thick stuff down 6 stories......

There are several tunes than can be played here and if it is possible to find a 6 core power cable (probably unavailable!) of a suitable diameter, you can have 3 pairs to play with!!

As we still are not aware of the area on each floor to light, the number of lights needed, or the stairs themselves, we have to wait for further infos....

I personally see this as probably a fairly easy DIY job once we have ironed out as many of the possible snags as possible! Everyone's input is needed. I think that we are getting there slowly but surely!

Hi Andy,

Unfortunately the same current will go through all the circuit. Therefore if you use thinner cable for the 'top few stories' this will increase the overall circuit resistance (and therby the voltage-drop) for the whole lot.

Unless you are meaning to have seperate cable loops for the lower floors? i.e By-passing the upper floors? If that is the case then the cable distance increases. Voltage drop is directly proportional to current and cable distance and will therefore increase if you have seperate (more) cables.

The only way around this is to have several (smaller) panels nearer to the seperate loads, but I imagine sun-light (& therfore solar energy) at the bottom of a stairwell to be scarse as rocking-horse manure!

Alternatively you could use 24V panels and kick out enough 'juice' so that you can compensate for the volt-drop, but to be honest i think the point of the exercise is to use green power so lets not get silly and waste it. It takes plenty of energy to make these panels and batteries!

It would be better to run the lights from mains and use the solar system to run a drinks cooler on the roof terrace!

You misunderstood me completely and I have re-read my post, does this paragraph that I have clipped out not say it for you correctly? remember, from another post of yours, you recommended that Solar cells and batteries be on the roof....:-

My personal thoughts are to increase the size of the cable, at least near to the battery in the area where the maximum current will flow, say the top 3 stories. Then you could go down a cable size for the next 3 and down another size for the last two....

1) Charging Solar panels and batteries are stored on or near the roof.

2) The thicker cables will be required in the first few floors from the roof down as the complete current of all floors flows through this point!! Not at the bottom!!!

What sound does Homer make?

Have a great day anyway in spite of my Joshing!!!

I did not feel that I had to add any more detail than I did, I will re-read it to see if it was misleading, but ANYONE with only minor and basic electrical knowledge would understand that the maximum current is at the top and as each floor is paired off, the current going through the main vertical cables at that point reduces, the farther you go down!

I in fact feel that the cables should be thick enough to keep the volt drop to within 2% or less and as the farther floors (ground and basement) have the longest runs, should still have the over dimensioned cable as well I feel....

I have had some further thoughts that maybe it would be better to have batteries at each floor level (or a battery for say 2 floors) as charging current is going to be far less than the current from the battery when supplying the LED lights, so voltage drop will be less of a problem AND higher voltage Solar cells are quite normal and practical for battery charging....!

Also, you can have smaller solar cells and if one unit (battery or Solar cells) goes down, you only lose 1 floor (or 2 depending on the setup!)

Also, the owners on each level could opt to pay for lighting normally or buy the Solar system for their own floor (or not!)....

We are not finished here yet!!

cable size calculation is something to be done is each special installation.

As it will work on 12V DC the size needs to be well calculated, 1V drop is much worser here than working at 230V AC.

This kind of remarks are useless for me, it should be common knowledge.

You are SO right - again!

Thanks for all your interesting comments and suggestions.

Let me give you all some more info. Our floor height is approx. 10ft or 3m. Floor area required to be lit is approx. 8ft x 8 ft.

I can expect 5 hours of good sunlight for on a normal day.

I agree, the cost should preferably be recoverable in 3 to 5 years with savings in electricity bill.

Suggestion of IR is also good and I wish to consider, if cost permits. May be I can use it with the present system itself. If I use IR, will it reduce the life of CFLs / LEDs?

From all your discussions, I am a little worried about the cable quality, size and length to be used. I do not think, using a solar panel and / or battery on each floor is feasible.

Thanks for the update, maybe I can put down a few ideas using your post information,of course anyone is allowed to make other or better suggestions (thats the idea!), I do not consider myself to be anywhere near the final judge on this matter....I am also very interested in "getting it right" too....

1) make up a test "floor" complete in all details (in your garage?) to check out voltages, currents and lighting abilities of various LEDs as far as possible, before doing ANYTHING permanent in the building....

2) May I suggest a small hidden cable trunking going from top to bottom of the stair well as near to where the LEDs will be mounted. This will allow extra cables to be pulled in if required or repairs and updates to be made easily.

3) Each floor to be fused separately in case of a short circuit on that floor, not affecting the whole stairwell. These to be the smallest fuses in the system.

4) I believe that you might be able to get away with a single 3 watt LED mounted almost in the middle of each floor area, they have a 60° dispersion and will light a reasonably large area of the 10' x 10' area I feel. (this is one of the reasons for a test floor!). This will depend a bit on furnishing and colors, white being probably the best...

5) Either a single 3 watt LED for each stairway or maybe 2 angled to light each step well, one above and one below. Keep them well apart to stop one person's shadow making it difficult for a person following.

6) Find either a battery operated PIR sensor, or maybe a 12 volt version from a camping store, with either the lowest standing current or one that only activates say once a second to keep power usage low (you will only have at 8 of these if you are clever with the positioning!)

7) Have a circuit on the roof that removes power completely from the whole stairwell when daylight is available for all levels, so I guess the bottom level will need to be nest catered for primarily, but I do not know the building....

8) make sure that you buy an efficient solar charger control unit.

9) Use only "Leisure" Batteries, they accept an occasional deep discharge with no (better said "less") problems....Car batteries and similar do not!! The extra price will pay itself back the first time something goes wrong.

10) Oversize both on Solar cells and battery, its cheaper that way. But if you need to increase battery size, you can only do it in a proper manner with a further identical battery in parallel, just believe me on this point as the explanations are not needed here really.....pick the "sweet-spot" on battery size and cost. Have an emergency charger to hand for problems or dull days!

11) Fuse each battery separately and put isolating switches in to allow batteries to be checked out fully off line.

12) Make sure that battery compartment is fully ventilated as battery gas is explosive. Place no smoking signs and always have both eye protection and fresh water in case of spills or other accidents. Keep locked. Insulate from summer heat and winter cold. CO2 fire extinguisher to hand...

13) Oversize on cables remembering that the upper levels will have more current and the lower levels a longer distance. Plan for 1 volt or less drop on whole system...less is better of course! 12 volts is a bummer for voltage drops and current usage.....ask any car designer!!

14) I would suggest an accurate built in voltmeter for each battery, or one that can be switched around with a selector switch. This should be used also to make sure that overcharging is kept to a minimum (even though capacity will not be then 100% achieved, better an extra battery....) as this will also keep distilled water loss to a minimum which equates to not gassing as well!! Not overcharging will increase significantly the life of the batteries as a whole, as will keeping the minimum voltage levels above that at which batteries start to degrade and sulphate (even though it is a leisure battery(s) which supposedly accept this)

15) It may be a good idea to have a voltage sensing mains charger, that senses when the batteries are at their lowest allowable voltage to give them a boost AND IF it is still dark or better said, the solar cells are not charging for any reason......deep discharge of the battery should be avoided no matter what the manufacturers say!!

16) Design a tiny circuit with a push button and three low current LEDs, say green yellow and red, or a proper tiny voltmeter, fitted on the trunking on each floor,. so that a quick press of the button displays the current voltage on the main cable in the trunking on that floor level. It will help when installing and fault finding believe me and cost only a Dollar or two a go......

Please note that 12 volts is in most areas a non dangerous voltage, but Lead Acid batteries can deliver large currents instantaneously if a short circuit occurs, do not wear metal jewelry or watches when working on them. Any screwdrivers used should be insulated except for the tip itself....Do not oversize fuses unnecessarily, investigate any fuse popping using a cable loop current meter. The meter will be useful when designing anyway. Make sure that your digital voltmeter is accurate. Wear old clothes when working with batteries and a rubber apron & gloves if you do not want your clothes dropping to pieces from time to time from lead acid battery fumes.....! Wash or at least wet down anything that comes into contact with a battery. Wipe the batteries down carefully with a damp cloth occasionally too....

Final point, I know two things well, 1) this list is not complete and 2) the CR4 members are the best ones to maybe use this as a basic format and add or change or to do a complete redesign if needed.....

My personal thought: IR detectors are simple, off the shelf equipment and the extra cost will simply cover the alternative of tripling the solar panels and battery compartiment. The most PIR detection systems also contain a light level sensor, so that the zone with sufficient light does not consume costly electricity.

One simple suggestion on the solar panel mounting: make sure that you can clean the panels and that snow will not accumulate on them. Adding heating to be able to remove the snow automaticly is also a nice feature but it will cost you some extra panels and battery capacity to be able to give the power.

The battery compartment should be frost free and well ventilated!

You will not be able to save money on this, but you are sure that it will function.