# LED lighting plus solar panels



## Rondil (Jul 3, 2014)

I have been considering using Solar Panels to drive High power LED lights. By using the output of a solar panel to both charge a small battery bank and drive LED lights I could avoid the whole Inverter plus driver issue. Basically I would Configure the Solar array to run 48 volts, then connect them to a 48 volt charge controller to a string of 4 12volt batteries. From there to a Fuse array. Then run 48 Vdc to each light. Since voltage drop in the cable would be an issue I expect to home run each light to minimize voltage drop issues. The actual voltage the array would be configured at would depend on the lights requirements. Several of the lights I have looked at run at 48 volt, however many places never list the actual Dc voltage used. I am talking high bay 120 watt to 200 watt. 


It seems to me that Solar plus LED is such a great fit. You can build your own solar panels and save a bunch of money in parts. Probably not so much in labor. Go to ebay and search 3x6 and 6x6 solar cells. There are a number of videos on You tube that explain how to build them. 


A 250 watt panel runs about $250.00 pre-made. So for a commercial install I would use them. But for your home build your own.


Pluses: 
No power bill at all from the power company. 
No expensive Inverters or driver to buy.
No transfer switches. 
Run it in parallel with the existing lights so if any problems develop the old lighting system could be turned back on.
12 to 48 volts is considered Low voltage so wiring rules are less strict. I would use 12/2 jacketed speaker wire. 




Questions I have are:


How sensitive are LED arrays to slight variations in voltage? If I have a voltage drop of 2 volts in the cable and I get 46 volts at the light will that be an issue? Assuming a 48vdc light. 


I am looking at a service bay with 12- 250 watt Metal halide lights. My calculations indicate that the 120 watt should work well. The existing 250 MH lights put out 14000 to 20000 lumens. While the 120 watt LED does about 10000 lumens. While the Lumens are less as I understand it LEDs are more efficient at projecting light, so less is needed. Am I mistaken about this?


12 lights X 120 watts = 1440 watts


1440 watts / 250 watt solar panels = 5.76


To have enough excess current to keep the batteries charged I would go with 8 panels. Keep in mind solar cells degrade from UV light over time, plus in winter you would have a reduction in output. 


8 solar panels X $255.00 = $2040.00
Charge controller ~ $ 150.00
Batteries X 4 ~ $ 300.00 
Fuse block $ 25.00
Mounting kits x 8 ~ $ 800.00


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## KITROBASKIN (Jul 3, 2014)

I would be curious what some of the experts here would say about this.


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## SemiMan (Jul 3, 2014)

KITROBASKIN said:


> I would be curious what some of the experts here would say about this.




The experts are too busy rolling around on the floor laughing to type a suitable response.

But seriously Rondil, go back and do a ton of research and then decide if it is a good idea. You may even want to look at some of the posts on solar lighting on CPF.

Semiman


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## Steve K (Jul 3, 2014)

are there really panels for a dollar per watt? I thought the figure was much higher.

The inefficiencies of solar panels are significant, as well as all of the non-ideal conditions that they will be operated in. A 250 watt panel may only put out that power when ideally aligned with the sun on a clear day and while the panel is still cool (i.e. hasn't been exposed to the sun for more than a few minutes). 

I would recommend starting with a single panel and playing around with it. Hook up a light or two, hook up a battery, etc. The cost is relatively small, and you'll get some experience with how much power you can really get from a panel. It'll entertaining and a good education. 

Have you considered a skylight? I just spent a few days in a lab with one, and it really does help.


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## AnAppleSnail (Jul 3, 2014)

KITROBASKIN said:


> I would be curious what some of the experts here would say about this.



$3300 in solar lighting gear would pay my whole electric bill for almost a year and a half. Lighting is a small part of my power bill - The electric AC, electric water heater, electric vent fans, consume most of my power - and I have about 300W in fluorescents in the kitchen for hydroponic lettuce and herbs.

A window - With or without a reflector on the lawn - would be a great light source. Same for skylights. Heck, a decent heliostat would bring light in for cheaper than that. Check out the SunFlower heliostat, for about $300 you get a volleyball-sized sunbeam to shine into a room. That's a lot of light during the day.


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## Rondil (Jul 3, 2014)

For one I am in the research stage. Part of my research is asking people who may know more than me. I am looking into this for one of my customers who has a 2200 a month power bill. I realize that his copiers, welders, water heaters, computers consume a lot of power and there isn't much I can do about that. A solar array to power all that would be prohibitively expensive. A solar array to take the lights off of Grid power is doable. I have seen NO INFORMATION to suggest that it isn't. 
If I can reduce that 500 a month then payback would be a year or so. High wattage Metal Halides consume a lot of power. 

It sounds like I will be doing the LED lighting on the grid for now and experimenting with solar. As it looks like none of you have a clue. No one was able to answer my questions.

I talked to the customer about skylights. He doesn't want them due to leakage problems. 

As for solar panels being a dollar a watt, just check ebay. I just saw one for 230 bucks for a 250 watt panel. If you build your own you can go a lot less.

If your so smart give me one good reason why it won't work.


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## inetdog (Jul 3, 2014)

An accurate accounting for battery costs (AH capacity = 5 x daily load AH and replacement in 2-5 years) should give you an ongoing cost for free power that is note than twice the cost per kWh that you would pay for utility power. Off grid solar lighting is far from cheap, especially where the light is for visibility and not just decorative.

Also, though, you can get first grade panels from a second tier manufacturer for under $1/watt pretty easily. Mainly as overstock or discontinued, but still good panels. Prices may be rising soon as tariffs kick in.


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## SemiMan (Jul 4, 2014)

Rondil I will not waste my precious time responding at length because your post shows you have done almost no research and considering you are getting paid ...... There are so many flaws in your logic that a read of even one half decent article on using off grid solar power seems to have not occurred. Spend a few hours reading about sizing of off grid solar power then come back here.

Semiman

P.s. good solar panels can be had well under $1.00 per watt as pointed out but shipping is not free and can be substantial. Build your own solar panels .... Still rolling.


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## FRITZHID (Jul 4, 2014)

Ty semi, someone had to say it. Lol

Sent from my SAMSUNG-SM-G730A using Candlepowerforums mobile app


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## RetroTechie (Jul 4, 2014)

Rondil said:


> It seems to me that Solar plus LED is such a great fit.


Let's start by saying that personally I'm _very much_ into your line of thinking, Rondil. But reality is a complex beast... And there's a number of flaws in your thinking:

1) If you've got sunlight, why not use that directly?
2) If LEDs are so good, cheap and efficient, wouldn't everybody use them? Oh right, most people do! Just to different degrees, and for different applications.

3)


AnAppleSnail said:


> Lighting is a small part of my power bill - The electric AC, electric water heater, electric vent fans, consume most of my power


True - for most of *mankind.* Sure it matters how you'd power those LEDs, but the same is true for all other equipment. If low-cost lighting is your thing, efficient light sources (like LED) do the trick. If energy saving is your thing, start with the biggest consumers first (heating, airco etc. comes to mind).

4) A 500 Watt-peak solar panel isn't what you need to power up to 500W worth of equipment. A 500 Wp solar panel is a *long-lasting energy source*, that provides *up to* 500W _under ideal circumstances_ (and 0 at night!). You shouldn't be asking how much Watt worth of panels you'd need to power everything in your house. You should be asking how much you want to invest in a solar setup _right now_, and what's the best way to use whatever energy comes out. Reduce your electricity bill, feed a surplus back into the grid, run that airco on hot days, charge the battery on your boat, whatever.

5) Store energy in a battery, and whatever goes through it, has a $/kWh cost attached that's likely much higher than _either_ solar or grid power. So first you'd have to ask yourself if you'd want to use a battery _at all_. And 2nd you'd have to ask yourself what for. Of course "to cut that LED lighting loose from the electric grid" is one option. But only one of many, and each purpose places different demands on battery type & capacity you need.



Steve K said:


> I would recommend starting with a single panel and playing around with it. Hook up a light or two, hook up a battery, etc. The cost is relatively small, and you'll get some experience with how much power you can really get from a panel. It'll entertaining and a good education.


+1

And indeed, the going price seems to be around $1 / Watt-peak these days. If it hasn't dropped lower in the meantime...


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## aw73 (Aug 2, 2014)

with all the negativity towards solar panels, it almost seems as if you all work or own stock in power companies....lol. dont ever let anyone discourage you from doing something or trying to make something better. we wouldnt even have lights if the inventor got discouraged from people saying you cant, its impossible, your crazy and so on....etc. it is possible.


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## SemiMan (Aug 2, 2014)

aw73 said:


> with all the negativity towards solar panels, it almost seems as if you all work or own stock in power companies....lol. dont ever let anyone discourage you from doing something or trying to make something better. we wouldnt even have lights if the inventor got discouraged from people saying you cant, its impossible, your crazy and so on....etc. it is possible.



Feel free to stick your head in the sand but the rest of us live in the real world. 

Its nothing against solar panels.... Its panels, 8-10 days of battery storage at end of battery life and cold for where used, batteries killed by heat, hopefully no shading on the panel, the large panel and large projected area for wind loading for pole and footing design, the larger footing to support the panel and batteries , the smaller light due to the limited power available, the increased failure rate due to increased complexity, eliminating the benefits of long LED fixture life by introducing a shorter life product , namely the battery.


Please explain why you think solar lighting is such a panacea?...lol


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## aw73 (Aug 3, 2014)

see what i mean about people trying to discourage?

i never said solar lighting was panacea. there are thousands of people using solar panels and cutting there energy cost in half or more and some are even making money. and batteries can be restored, i have done it, so maybe you need to do a little research on that. there is a reason when you buy a new car battery they want your old one.

solar lighting would only be used during the day, solar panels could be used to charged batteries during the day and lights would be used maybe 3 or 4 hours at night.

solar panels would only be part of energy savings, you would need to stop being such a consumer and be more responsible and learn to use less and have less to save energy just like most people do that are off the grid.

maybe you need to get your head out of the sand.....you sure your not working for the power company?....lol.


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## SemiMan (Aug 3, 2014)

With the exception of California and other very high electricity costs, no one saves money with solar panels without subsidies.

No one recovers properly treated lead acid batteries that have simply wore over time. Never been shown to be done in a controlled ... Ie independently observed environment.

They want your old battery back for the core charge. Most of the weight is lead and tin in some and is almost 100% recovered when reprocessed.

Your LOL just makes you look foolish as you hand wave without addressing real issues.

Again , some of us live in the real world ...where we solve real world problems. We don't simple LOL the problems away, we need to solve them as customers are really pissed when the lights fail.

Using solar to exclusively serve lighting makes little sense. Use all that you can on the loads that need it and store nothing as nothing is left makes far more cost and environmental sense.


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## aw73 (Aug 3, 2014)

i guess the power companies should of talked to you before they invested their money in solar panels and wind mills to get energy to the masses......lol. i guess solar panel company stocks are going to plummet now since you have shed the light on their stupidity.......lmao.


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## aw73 (Aug 3, 2014)

and yes i have recovered old 12v car batteries. just because you havent seen it or dont know how doesnt mean it isnt true or cant be done.


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## FRITZHID (Aug 3, 2014)

I don't think he's saying that it's totally uneconomic, just the fact that unless you want to devote a large investment initially, the cost vs. gain rises considerably.... more than other methods/technology.
A smattering of LEDs and solar panels spread over X.X ft² vs. same land area dedicated to solar power is staggering. You are comparing camp fires to nuclear power.


Sent from my SAMSUNG-SM-G730A using Candlepowerforums mobile app


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## Illum (Aug 3, 2014)

Well... I can see a couple problems off the bat. 


You mentioned 48V, nice... good to see people deviate away from 12V and take advantage of voltage over thicker wires... however...
You might have difficulty finding a commercially available charge controller to charge a 48V battery bank. Typical "12V" solar panels are about 21V open circuit [VOC], 17V max power [VMP], You'll need to daisy chain at least three modules in series to offset the charging differential if you ever did manage to find a charger. 


Another thing, if you're getting "48V" from daisy chaining four 6-cell Lead acids I got news for you. "12V" is a nominal figure. The voltage at depletion is about 1.7V/cell, or about 43.2V, voltage at full is about 2.2V/cell, or about 52.4V. While shopping for disconnects, take note on the voltage rating for DC, you'll find that many battery breakers aren't rated that high. My 120A main breaker for the "House battery" is only rated at 42V. You'll see an accelerated oxidation rate on your contacts running the system on voltages way above spec. 


Now you mentioned 48V LEDs... if they have internal drivers then they may be constitutionally incapable of compromise when it comes to supply voltage fluctuations. If they are resistor driven they could care less as long as the supply voltage is below their maximum allowable upper limit. If you are using the higher voltage to offset voltage drop I would suggest DC-DC converters and running lower voltage LEDs. As long as the DC-DC converter has a 2:1 [or better yet 4:1] input range your output won't be affected by the voltage drop or fluctuation one bit. 


Before you consider any solar project, evaluate where you are standing from a latitude perspective. If you're in an geographic location poorly suited for PV you might end up with a PV array three times it needs to be only to gain maybe a third of its rated production. Best luck to you.


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## SemiMan (Aug 3, 2014)

aw73 said:


> i guess the power companies should of talked to you before they invested their money in solar panels and wind mills to get energy to the masses......lol. i guess solar panel company stocks are going to plummet now since you have shed the light on their stupidity.......lmao.



Lmao ...yes I laugh at your ignorant posts. You really need to research before spouting off.

Solar panel stocks are pretty much maybe 1/3 their value of what they were in 2011 when government subsidies dried up and prices and values tanked. The largest solar panel company in the world Suntech declared bankruptcy.

The only reason they invested in solar and wind was due to government incentives and mandates.

That said, large scale solar thermal in California has promise even without incentives .... Ie handouts of taxpayer money.

Wind can have better kW/h costs but incurs large costs in backup generation.


No one has shown the recovery of a lead acid battery that has been treated properly and has aged normally. Never .... Not once under controlled repeatable conditions. Limited recovery of poorly treated batteries has occurred but that is not what we are talking about.

You talk a good story ... Now perhaps stop waving hands and show actual results.

By the way how much solar you out in? .... Me ... Hundreds of solar light and almost a megawatt of solar. How many solar chargers you designed?



Illum ....48v chargers are easy to find and buy.


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## aw73 (Aug 4, 2014)

how much solar am i out in? way more than you, im in the solar everyday all day its called the sun, some people have to work...lol. how much bull do you talk?......mega piles....lol. how arrogant are you?.....giga arrogant!!!!!! 

i dont like people like you, your not helpful, your hurtful, know it all, and always negative. you could of left a very helpful and positive post as illum did but, you chose to be a **** and be negative on your very first post on this thread.


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## SemiMan (Aug 4, 2014)

aw73 said:


> how much solar am i out in? way more than you, im in the solar everyday all day its called the sun, some people have to work...lol. how much bull do you talk?......mega piles....lol. how arrogant are you?.....giga arrogant!!!!!!
> 
> i dont like people like you, your not helpful, your hurtful, know it all, and always negative. you could of left a very helpful and positive post as illum did but, you chose to be a **** and be negative on your very first post on this thread.



Some people like to spout whatever crap they believe and hope that others believe them to as perhaps it makes them feel important. Others would rather spread the truth even if not popular.

Those who believe in honesty and integrity will choose the latter.

Those with knowledge and experience also don't jump on bandwagons as they know better.


Unlike you I am not full of bull and I don't make stuff up. You attack what I write but you don't counter anything with valid arguments. We can't have a discussion as you want to spout opinion not discuss facts.


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## SemiMan (Aug 4, 2014)

In terms of the original poster keep in mind his post is wrt a commercial venture with his client as he stated. When you do work for others you owe a duty of care to know either know what you are doing or spend the time to learn. It was obvious from the question and analysis that little research happened.

In terms of Illums post while you felt it was helpful it was not correct. There are many 48v charge controllers on the market. The rest of his analysis about needing multiple panels in series is bang on.


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## jtr1962 (Aug 4, 2014)

Wouldn't grid-tied solar make more sense here (assuming the power company pays for solar-generated power at the same rate it charges for grid power)? If you do that, then the grid is effectively acting as your "battery", saving you a ton of expense and aggravation.

On the batteries, why not go with LiFePO4 if you must have batteries? Lead-acid batteries are crap. They're cheap compared to LiFePO4 but you pay for that lower purchase cost later on in terms of reduced lifetime and less reliability. I never got more than 2 years out of a lead-acid battery in a UPS. If you have to buy new batteries for a solar setup every few years, what's the point?

I actually think if a person truly wants to go off-grid, some combination of solar and wind might work better than solar alone. Chances are good the wind generator can pick up some of the load when the solar panels aren't generating. That would not only allow a smaller battery, but also smooth the current draw. And yes, even in this case I would still use a LiFePO4 battery.


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## aw73 (Aug 4, 2014)

people forget that power, "energy" , is a luxury not a necessity, so truly off grid is doing with out some luxuries. 

as i get older i realize that some things are not as important as they use to be.

i feel very privileged to be able to talk to people around the world on the internet. 

back in the late 80's and early 90's internet to me was a fairy tail or fantasy, even a hand held cell phone was a futuristic fantasy. 

so i would never discourage anyone from experimenting or trying something new because it might lead to something great.


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## SemiMan (Sep 2, 2014)

jtr1962 said:


> Wouldn't grid-tied solar make more sense here (assuming the power company pays for solar-generated power at the same rate it charges for grid power)? If you do that, then the grid is effectively acting as your "battery", saving you a ton of expense and aggravation.
> 
> On the batteries, why not go with LiFePO4 if you must have batteries? Lead-acid batteries are crap. They're cheap compared to LiFePO4 but you pay for that lower purchase cost later on in terms of reduced lifetime and less reliability. I never got more than 2 years out of a lead-acid battery in a UPS. If you have to buy new batteries for a solar setup every few years, what's the point?
> 
> I actually think if a person truly wants to go off-grid, some combination of solar and wind might work better than solar alone. Chances are good the wind generator can pick up some of the load when the solar panels aren't generating. That would not only allow a smaller battery, but also smooth the current draw. And yes, even in this case I would still use a LiFePO4 battery.



Most UPS batteries are low quality, kept relatively hot, and can have questionable charging circuits.

Whether Lead-Acid or LiFeP04 depends on what your climate is and whether the lights have to be on, i.e. you expect them to work.

If you expect them to work, and you are in a colder climate, lead-acid is superior. If you are in cold climate, you need lots of storage, and will typically have shallow cycles. A good AGM battery will last 5 years+ and 7 would not be unreasonable if the system is designed well. AGM performance is better when cold as well. Your LiFePO4 costs can be 3x, without the commensurate life improvement.

If you expect them to work and you are in quite a warm climate with lots of sun most of the year, LiFePO4 may be better. They take high heat better and last longer when constantly warm. You can also get away with less storage and deeper discharge as sun resources are more regular and then don't mind deep discharge. Here your LiFe costs may only be 2x and life easily 2x.

Semiman


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## DIWdiver (Sep 2, 2014)

For high-bay lighting, LEDs are probably not greatly better at delivering lumens than HID (by whatever name), unless the length and width of the bay are substantially greater than the height. This is because without reflectors or other optics, LEDs lose a substantial portion of light to wide angles. HID is far worse, of course, until you add reflectors. All in all, LEDs _are_ better, but not by a factor of 2. You'd have to do some serious research to determine exactly what the lumens/watt delivered to the target are for the two different technologies, and specifically the two different products you are looking at, before you could do a precise comparison. I've never seen such a comparison done in a way that I'd have confidence in.

I don't think you've budgeted anywhere near enough for batteries. It looks like you are planning on 4 ordinary car batteries in series to provide 1440W of backup power. You have not budgeted for high-quality batteries, so you probably aren't going to get more than 50 A-H per battery. At 48V, you will have about 2400 W-H of capacity. That will run your lights for 100 minutes. Yet you seem to think you can run for several hours after dark.

You haven't budgeted for deep-cycle batteries, so running your batteries this way will destroy them in a few weeks.

I don't know where you are, but unless you are someplace where you can expect bright sun for most of the day on most days, you should count on far less than peak power from your solar panels. Even if you are in a location where you can expect bright sun most of the day for most days, you should count on no more than 50% peak power for 12 hours without sun-seeking equipment, which you have not budgeted for. Excuse me, I meant to say "for which you have not budgeted". In other places, much less. In any event, you need to budget more for panels. Yes, 50%/12H is a WAG. Prove me wrong.

When budgeting more for panels, you probably need to budget more for charge controllers, or sacrifice some of the peak hours, which means you need to plan for _more_ panels and/or _more_ batteries.

LEDs are _very_ sensitive to variations in voltage. For a modern LED at max output (XM-L2 at 3A), a 1.5% drop in voltage causes a 6.5% drop in output. You suggest a voltage change of 48V to 46V, but that's laughable. On charge, a 24-cell lead-acid battery is probably 55V or so, near discharge it's probably closer to 44V, or even 40V depending on depth of discharge. That would produce a HUGE variation in illumination, unless you provide proper LED drivers. With proper drivers, this issue can be completely overcome, but you think you can do without them.

You may mock the experts, and you may accuse them of ulterior motives, but until you have walked a mile in their shoes, trained a year (or many more) in their field, and worked a year (or many more) in their industry, you should not consider yourself superior.

Nobody here has said that solar power is a bad idea, or that we should not be doing it. Nobody has said that innovation is a bad idea, or tried to suppress it. They've only said that _economically_ it doesn't make sense. Unfortunately, in many cases, that's the same thing. That's why government incentives are important. They promote innovation where economics otherwise wouldn't. They promote research that otherwise wouldn't get funded. _That_, hopefully, should provide a better future.


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