Solar lighting (real not artistic) ;-)

[T i m]

Hi All,

I would like to put some solar powered lights in the 20' x 10' x 8' (to eaves) workshop, mainly just to be able to see in there to move about rather than work as such. I don't have power down there all the time atm (long story) and even if I did (and in the spirit of d_i_y) I still like the idea of 1) making use of some of this kit [1] and 2) having some alternative lighting in there.

So, I don't mind having a few unit, say one on each of the 5 roof trusses and a pull switch by the door to turn them on and off but what is currently the most efficient and good vfm please, LED or CF / Fluro? 12V inverted up to ~600V or regulated down to 5 etc?

I was thinking those tubular 12V x 8W fluro inspection lamps (typically a fiver) or LED equiv held under the beams by a couple of Terry clips each (as that way they could be easily pulled down to replace the lamp (fluro)) or to help me see in a dark corner). They also have clear outers (not 'diffusers') and even a built in reflector so I can get most of the light out and where I want it and being designed for 'inspection' would probably take a knock or two without damage. If I leave some slack cable on them they could be temporarily re-positioned making use of the hook you often see on the ends of such things?

the fluorescent, are there good and no_so_good, from an efficiency pov please? Does spending more money generally mean I get a better design (from a Lumens pov and ignoring the same unit priced higher etc).

I did think of using a maintained lamp unit but they would be more expensive and I don't necessarily want them on when the power is off (and I don't think they would be easy to switch etc).

Any ideas welcomed. ;-)

Cheers, T i m

p.s. I guess I could use an inverter to run the existing 6' fluros off a solar / mains charged battery but that might make the whole project that much bigger and I'm not sure how efficient it would all be? This all started from seeing one of those 15 quid solar shed lights! ;-)

[1] I have various solar panels (@~5W), can probably find an ex backup type battery or two and have some suitable cable, so it's just the actual lighting units I need.

[meow2222]

CFL is most efficient, then linear fl. LEDs vary - theyre most useful for very low light output devices, eg 1w. Ideal for low power drop lights due to robustness.

Every change of voltage loses energy, so 12v will be most efficienct.

I'd probably use a couple of those for ceiling lights, and a droplight or 2, maybe LED.

there is significant variation. Very thin tube CFLs are some of the best.

Tesco microspirals are efficient and cheap. High CCT lamps are slightly more efficient, but the light quality's nasty.

While you could run a 5 footer at 240v, it would take a real long time to replenish the energy used at just 5w. Energy capture can be improved a little with diffuse reflection in winter only - dont concentrate in summer.

One option would be to run the 5 footer at much reduced power. Details depend on the ballast type, but either way its easy to do. Tube life would drop signifcantly, but tubes are so cheap and other methods not so, so it may work well.

TBH though I'd not overlook gas lighting. Its way more reliable than solar electric, needs no installation, gives sensible output levels.

NT

[T i m]

Ah, didn't know that.

Ok ..

That's what I was thinking but whilst I could probably (nearly) run LED's directly from 12V DC (ie, no regulation > wastage?) don't these CFL's have inverters in them anyway?

Ok.

I don't suppose they are available in 12V though? :-(

As long as they illuminate the area efficiently I'm not fussy. ;-)

Understood.

;-)

Hmm, I think I'll stick with an independent system then. 240V for real / working lighting and this solar for the odd time I pop down there with the mains off (why is it the tool you need is where you aren't).

Hmm, not sure about that (gas) .. sounds like the recipe for an instant sun roof on my workshop!

All the best ..

T i m

p.s. Sorry but I'm getting old and my memory is failing fast ... did we meet up once, solar panels and generators etc?

[The Natural Philosopher]

AFAIK that is in fact not true.

Of course. One reason they are not very efficient.

Consider the typical 12v powered caravan fluorescent.

If you are using solar panels to charge car batteries, anyway.

Yes. I would simply have some batteries charged by solar if you must, or by mains charger, and use caravan lights as emergency, and proper mains tubes for real power.

[pete]

If you fancy playing around with some LEDs, try these kinda things:

high-power LEDs are extremely bright. These units claim up to

400 lumems (c.f. 100W bulb: 1700 lumens) and can be wired in series to match the voltage from your battery - more or less. The one's I got a couple of years ago were 1W jobs, they came with a warning not to look directly at the light source. Although not as bright as a mains bulb, the source is much, much smaller so the light is more concentrated.

[T i m]

Is this in general .. in comparison with incandescent (mind you, I could do with some heating down there as well). ;-)

I guess it's all relative. Lucky my eyes are still reasonable in the dark and all I'm looking to do here is make it easier than stumbling about in the pitch black or taking a torch.

I have the panels and ex UPS batteries so I might as well have them wired together and doing *something*?

Well, there are currently 6 x 5' (not 6') singles down there and supplementary light over the bench and an Angle poise with mini spot over the lathe. I could leave an auto charger on there as well cos if the solar panels do their job there won't be much for the mains charger to do when the power is on?

Cheers, T i m

[T i m]

Understood.

Yes, I have a single_LED torch and it is very intense indeed!

If it's agreed that LED's are the most efficient I'm thinking I could wire a few of those little 'stick-up' lights (that normally take 3 x AAA or similar) together in series parallel (if each unit is designed to run on 3 x 1.5V (4.5V) then 3 in series should be ok on ~14V ?

I've seen said pretty cheap on the markets and I think are often also magnetic (so would clip directly to my steel roof angles). ;-)

enough it will look like those halogen downlighters that people were so keen on before they became too expensive to run. ;-)

Cheers, T i m

[meow2222]

Yes, but of a different type to the one's you'd use externally. Ever voltage conversion step loses energy, so the less steps you add the better from an effieicncy POV. Of course most efficient isn't always cheapest - 240v CFLs cost less than 12v ones.

I guess not :)

Then again if you only use it occasionally, and you've got more than one 5w panel and a battery big enough to supply it for as long as you use it, it would be ok. If.

ha - they do produce a lot of heat.

Sorry, I've not been to any of the ukdiy meets yet, so I dont think so. Been to other events though, if that's what you mean.

NT

[meow2222]

Both technologies cover a range of efficiencies, so best to look at individual ones if you want exact figures.

NT

[meow2222]

Both technologies cover a range of efficiencies, so best to look at individual ones if you want exact figures.

You need regulation for that, unless you want to run them with a very inefficient ballast. A constant current regulator is good, ideally an LDO type.

CFL and linear FL are the 2 most efficient domestic white light sources.

NT

[T i m]

So better or worse than the external ones do we think? I mean the external ones are much bigger and what must be built in so and I presume they wouldn't do that less they had to (bigger / heavier might be better but more expensive)?

Agreed. I was thinking that the nearer I could get to a (say) raw 12V as a ideal supply the less regulation I might need? However, you often deed a bit of an offset for active regulation so maybe I'd end up looking for a 9V supply rail for the LED's? With yer std LM7809 type regulators does that mean the surplus energy is going to be 'wasted' in the reg?

By quite a percentage it seems. :-(

I have since found quite a few suppliers of 12V CFL's and it seems they may be the preferred solution for remote buildings, stables and sheds etc. ie, You can get kits with panel, battery and a couple of lv CFL's.

Indeed, and that may well be the actual scenario / usage pattern.

As an aside I've just bought a couple of ~1.5W 12V (not 12V but higher of course) bare panels with the intention of making them up into fully waterproof modules to fix the South facing wall of this house, where it happens we park a couple of our motorbikes. A suitable non-latching connector fitted in the right place on the bikes and the panels should at least balance any background losses from alarms, and maybe even keep them topped up and ready.

I think there could be a market for a long, narrow 12V 'charging' panel that could be fitted on or on the wall underneath external window sills. Not the ideal angle(s) maybe but probably better than nothing and not 'obvious' to passers by?

I was thinking more the mixture of gas and air and a lighted match!

I was thinking I may have been to yours, a few years back but I must have my wires crossed (sorry).

Cheers, T i m

[The Natural Philosopher]

Indeed. But AFAIK the figures are roughly 10-25% efficient for linear fluorescents. 6-10% for CFL, similar for LED and 1-3% efficient for incandescent.

This makes reasonable reading.

CFL bulb is merely a normal fluorescent with all the efficiency compromised by a cheap and nasty inverter, a shortened and coiled tube, and use of natural light phosphors to make it 'look' nicer.

Industrial grade striplights with electronic ballasts compromise light quality to get efficiency.

[The Natural Philosopher]

That right, but CFLS are not as efficient as linear.

From experience, the caravan type linear fluorescent is probably the best thing from a 12v source, though some LEDS seem to be catching up fast.

To got from DC to inverted AC, then to a mains CFL, and then back to DC and to AC again in the bulb is madness.

[meow2222]

They're really 2 fairly different things. Efficiency and life expectancy vary a fair bit for both types.

If youre thinking of LEDs here, its the other way round. The closer your LED string is to 10.4v (cutoff voltage for 12v lead acids), with an unregulated ballast the more the LED current varies as the battery varies from 10.4v to 14v. Say we have a 10v LED string, then the ballast drops anything from 0.4v to 4.4v, current changing by a factor of 11, which is quite useless.

If you want efficiency, you need to use a regulator as an LED ballast.

Whats dropped in the reg is wasted, yes. But you cant use a 7809 as 78 series require a min Vdrop of 4v, and 10.4v - 6v =3D 4.4v max for your LED string, with consequent poor efficiency. Best to use an LDO reg (Low DropOut) in constant current mode, then you can go upto 10v or more with your LED string.

If you went with a switched mode reg, then the dropped V wouldnt be wasted, but for LEDs the cost & complication isnt generally worth it. OTOH if you know how to easily make a basic sm reg it would likely be practical.

Would save you buying anything but an invertor & changeover relay.

Then again if you've got mains you dont need the panels.

Maybe in summer. Are they going flat?

I'm not sure a PV solar panel is that useful whre there's already mains.

Who would leave it on unlit?

Ah, yeah must be someone else then

NT

[The Natural Philosopher]

LEDS of the silicon/gallium sort have typical forward voltages in the

1-3v region.

They need to be current driven. the cheap and cheerful wy is to bung in a power wasting resistor. The better way is a SMPS that detects the current and adjusts output accordingly. Essentially chop te DC to AC and put an inductor in series to limit current losslessly - well fairly losslesly anyway.

7809 is not what you want at all.

Econmomies of scale. If you have a large office or industrial space to illuminate, you use shitloads of striplights. They are the most efficient, and because they are produced in shitloads, they are cheap.

The mini ones are just as hard, if not harder, to make, and have slightly more complex electronics. And probably slightly less efficient electronics. And are sold in much smaller quantities for boat and caravan type usage.

Yup. I've got about 4 such in my camper van. No battery though. Just a

12v capable mini fluorescent pair with the inverters. YOu can in fact get fluorescent torches as well.

Really?. I don't understand at all. 5W is 5W irrespective of the voltage.

I can run a couple of 12v fluoros, an occasional water pump, off a nearly fsked leisure battery for a couple of LONG evenings before it goes flat.

Many people with boats use solar panels to charge leisure batteries, and run without mains of generator power at all.

Its not hugely efficient, nor is it cheap, but if te biats engine isn; running, its reasonable compromise.

Again, look at the caravan market. My caper has a mains to 12v SMPS charger that is very compact and very efficient. Not weatherproof, but that is simply a question of the right enclosure.

Meow is as usual disseminating a mixture, of truths, half truths and mieleading stuff improperly understood.

If you want to go into a solar/leisure battery/12v lighting system,with or without mains backup, go and find a caravan or boat specialist suppliers. Everything you need will be there.

using an inverter to the run stuff intended for mains is a dubious path: If you want to go THAT route, use a computer UPS - they will run a complete mains installation from batteries for a period.

And then use proper full length striplights, not CFLs.

[meow2222]

fair enough, though CFLs also use higher efficiency phosphors (triphosphors), and some of those caravan 12v linear modules have awful ballasts. You also need to compare the 2 options at the specific light output level you're looking for, and ratios vary.

If you use high efficiency tubes, yes. There are also less efficient ones. Short T12 halophosphate in warm colours dont perform so well - and its lower power tubes that 5w panels will run.

NT

[meow2222]

I think you exaggerate there.

240v CFLs are no less efficient than 12v ones. In fact the CFL ballast switching device drops much less percentage of the supply voltage with a 240v one. The drop in the mains ballast rectifier is tiny (percentage wise) compared to the greater percentage drop in the 12v ballast switching device.

The significant differences between the 2 routes are invertor losses and the greater efficiency and convenience and lower cost of mains CFLs.

NT

[meow2222]

White LEDs drop 4v or more. I assume Tim would go for white. No LED drops 1v.

5' tubes are 65w or 58w. 240v fittings run them at full power, not less. There are invertor losses and lead acid battery energy losses. A 5w panel won't deliver anywhere near 5w in winter, so will take a very long time over recharging. Simple enough.

yes, run time is down to battery capacity, recharge time down to that & panel output.

Its common enough. It has the advantage that you can run a range of mains appliances when you want to, and the plus that you can get your CFLs with the groceries, or use ones you rejected for house use.

It will run (without load) whenever mains goes down, in most cases discharging itself before you ever get round to switching the light on. Not ideal :)

Full length strips will eat far more power, not very ideal for a 5w panel.

funny. Neither of us is perfect, but lets stay in reality.

NT

[The Natural Philosopher]

Exactly. Why use 2 inverters when you can use one. In bith cases you have to up convert from 12v, at putativley similar efficiencies; then you add another stage - the electronic ballast. It cant be more efficient that way.

[The Natural Philosopher]

That marvellous invention called 'A Switch' generally fixes that ;-)

You dont have to run them as backup. They are after all simply inverters that run all the time..off batteries tat are charged all the time..you can get the separate bits.

Well I already said that the ideal for low power running of 12v were caravan lights.

I was merely pointing out that if you wanted to use mainly mains but occasionally battery, mains lights and an inverter would be possible.

And te UPS industry ahs suitable perty high power invertersm, if you have a shed load of batteries.

Well you do wander off into needless complexity.

Before you discuss solutions, it pays to analyse the problem properly.