question about solar panel pricing

[asheets]

I just got the harbor freight flier today, and they have this advertised for $9.99 this week -- http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=44768 -- Basically, it is a 12V, 1.5watt (so I'm assuming its .125A)  12" x 8" panel.  Any good?  This comes out to about 11 cents per square inch.

Also, occasionally, they have this -- http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=41144 -- on sale for $39.99.  12V, 5 Watt (.4167A) 18" by 12.5".  This comes out to 18 cents per square inch.

They also have some for 44 cents per square inch (http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=90599, 12V 45 watt), as well as a few others that don't have their sizes listed but are in the "expensive" range.  

Assuming that the power output is the same per square inch (is that a reasonable assumption, BTW?) is 11 cents per sq inch a good price or can it be beaten elsewhere?

[Opera House]

Unless you are naked, I wouldn't be buying by the inch.  This type of panel (BLACK) wears out and has a higher failure rate.  They are cheaper and do have a better performance when hot. Small panels are always very pricey per watt.  Better panels are BLUE in appearance.  Every panel has a use.  Sounds like your application isn't critical.

[ghurd]

The 'price per square inch' is not a good way to look at it. 'Price per amp' would be better.

The price seems good, but the quality of those is 'questionable'. They just don't last very long. It's only a good deal while they still work.

The 1.5W fails with no obvious reason. The wire is not sunlight resistant.

The 5W seems to have layers seperate.

The 15W does both.

A better choice for the small sizes could be the VW panels. Mine all make more amps than they claim. They'll need a little weatherproofing. EBay, or the VW dealer may just give you a couple.

Spend a little more money for something in the 15 to 50W range.

G-

[johnlm]

You might want to do a search on this site regarding the Harbor Frieght panels. They are amorphorus silicon panels (the cheapest kind) and my experience with the small 1.5 W unit is that you can get about 1 watt out of it and the 5 W panel will only give you about 2.5W. Some people have reported a bit better performance than this. I have no experience with the 45W set but I suspect similar performance. If you factor in this limited capability the price is not really that good.  The small (1.5W) ones, if you get them for $10 US, are a fun toy to play around with, and ok for charging nicads but not very useful for any serious charging.  I use one of these small panels set in a window of my camp trailer up in the boonies to keep the 6 D (3.5AH) size nicads in a radio charged up.  Works good for that.

And I use two of the 5W panels in parallel to provide a trickle charge on the main 12V camper 115AH battery when the wind is not blowing - I use a modified box fan motor conversion capable of 3 to 4 Amps in a 15 mph wind with a 4 ft prop as the primary charger for the 115AH battery.

Johnlm

[Nando]

Johnlm:

>I use a modified box fan motor conversion capable of 3 to 4 Amps in a 15 mph wind >with a 4 ft prop as the primary charger for the 115AH battery.

What about if you detail your Fan motor conversion, this is one that could be used in many places and may be in-expensive enough even in un-developed countries.

PHOTOS would be ideal

Regards

Nando

[johnlm]

Nando,

I can do that but Ill have to take it apart and take some pics.  Give me a couple of days.  I think I have maybe around $15 to $20 in it.  It uses 12 ea of the 1 X 1/2 X 1/8 neos that Windstuff Ed sold for awhile for about $1 ea, and maybe 150 ft of AWG 18 wire.  I took the motor out of an old 20 inch box fan that my parents bought back in 1965.  Had to replace the rear bushing with a ball bearing unit I got at Ace hardware for about $3.  The ball bearing assembly provides better for thrust on the shaft.  I guess I could take some pics and put together a somewhat detailed proceedure in a the diary section.  It is the most successful box fan conversion I have done as far as getting some reasonable power out of it.  Ive not had quite as good of success with the more recent box fan motors that you find on 20 inch fans in Wallymart for 10 to 15$, although they are not totally bad.  Im testing one of the wallymart (forget the brand name of the fan) conversions right now that I made into a 3 phase unit using 8 of the same neos mentioned above.  It will only put out about 2.4 amps into a 12V battery using a 3.25 ft diameter 4.8 TSR prop in a 15 mph wind.  I mount these on a gravity furled platform base made out of wood, and raise them up on a guyed TV mast pole(s) to around 30 ft.  These units are kind of rough looking as most are experimental but they work ok.  I got interested a year or two ago on converting these box fan motors when one of the posts on this board suggested a contest to see if someone could get 10 watts at 10 mph for $10 out of one of these motors.  I rate most of these up to around 15mph wind speed as that is pretty characteristic of the wind speed I like to work with, and it usually doesn't get too much above that up on my mountain property.  Sometimes we get 50 to 60 or greater mph chinook winds down here along the front range of Colorado, but at those times Im just hoping my mills don't blow away into Kansas.

John

[asheets]

I don't have an application... yet...  I'm just building stuff and charging random batteries and running lights off of really small/cheap/homemade inverters...

[asheets]

Fair enough...  I was just looking around for stuff to play with and figured I could spend about $100 and have something reasonably sized to play with...

I was thinking about getting at elast 1 of the 1.5 watt units to power my electrolysis rig with...

[asheets]

OK, converting to price per amps, I'm getting a range of $20 to $150 per amp.  The best deal was neither the biggest or the smallest unit -- it was for a 12VCC, 5W "battery charger".  All but 1 of the units were 12VCC panels with black cells

For comparison purposes, I also looked at some Electronic Goldmine offerings.  Most of their offerings are 0.5VOC cells, so I'm not sure that they are a valid comparison.  However, the prices I'm getting are between $1.87 and $4.98 per amp.  I couldn't tell if they were blue or black, but most of them were chipped or rejects in some way (not a big deal for me).

A couple of others I sampled on Froogle (Sharp, C Crane, Kyocera, Envirolet -- all 12 VCC models, some blue and some black) ran from $53 to $179 per amp.

[asheets]

OK, thinking a bit more about this...  if I went with the EG cells, I'd need about 30 of them to get to 12VCC.  That brings their price up to between $57 and $150 per Amp, excluding construction costs and labor.

[zap]

Alan I bought the HF 45 watt kit for myself for a Christmas present. I had been looking at it for awhile and decided to get it when I received a 20% off coupon from HF.

The panels put out only about 36 watts but that's only been one test, I still need to mount them somewhere. They don't look to be too well sealed for weather but a little silicon would probably cure that.

I tested the charge controller and it seemed to work. The multi-voltage taps on the front worked but seemed to be a little low on their output voltage.

The two 12v cfl's put out a pretty fair amount of light at about 4.5 watts.

The frame they include is a little baffling.

Adding a battery gives a pretty fair system to goof around with if that's your plan and if you've got a coupon it may make the decision that much easier. I figure the bulbs are worth maybe $5 each, lets say $15 for the controller, add in the coupon and that brings the price down to around $5/watt even if they never produce more than 30 watts.

Like the others have said, I don't know about long term for the panels but time will tell.

[veewee77]

When pricing solar panels of any type, the only way you can really get a handle on the effective cost is in dollars per watt. You can't really compare them by amps because amps will depend on volts and vice-versa.  But since watts is amps times volts, you can always get a standard on a price. Panels of usable size are running around $5 per watt right now.

Example, if you have a 24V panel that makes 100 watts, that would be 4.16 amps and about $500.

If you have a panel that makes 4.16 amps, but your system is 12V instead of 24, the wattage would be 50 watts and about $200. Still the same amps, but different prices because they are sold by wattage, not amps.

Use wattage. . .

100 watts at 12V is 8.33A and 100 watts at 24 volts is 4.16 amps.  But it is still $500 no matter how you slice it.

Doug

[ghurd]

The $/watts on HF type non-UL panels is skewed, like IIRC the 15W panel is peak power rated 15V at 1A, but most panels are rated at around 17V.

[ghurd]

The controller with those seems to be junk (I struggled for a kinder word) if is still a little yellow one. The daily gain in the battery will be greatly improved using a different controller, like the SG-4 (~$25). One guy told me the difference was like 'night and day'.

Silicone them ASAP, just in case.

I know of a 45W (3 at 15W) running fine after 6 or 8 years. Maybe more.

BTW, I get called when something dosen't work. Nobody calls if everything IS working.

G-

[ghurd]

It gets worse!

A 12V PV should have 36 cells.

The EG cells I got seem to measure short circuit amps.

Some of EGs watt ratings are short circuit amps x open circuit volts. At least for the little panels.

ie the 4V at 100ma ($7), 4 in series (16V) into a 13.5V battery is ~65ma (might have been 35ma). 2 (8V) in series into 4 AA at 5V got near 100ma. Someone there is measuring stuff creatively.

I personally would not bother making one from the EG cells. To expensive, to hard, to complicated, to much work.

The 45W kit is probably about as reliable as a home brew, maybe more. And a LOT cheaper.

HF emailed a 20% off coupon just a minute ago. That kit is starting to look a little better for a starter setup. (after the controller is changed)

John is right about amorphorus. I only mess with crystalline, single or multi.

G-

[asheets]

OK, then... so what I'm seeing is that, per "watt", my target for a budget, non-long-term, panel is between $4 and $5.

In that case, my purchase candidates would be:

The Harbor Freight 45W panel -- $200

The Kyocera 50 W panel -- $233

The Sharp 185 W panel -- $880

The Kyocera 190 W panel -- $836

Although, I think I will go ahead and pick up a couple of the HF 1.5W, $9.99 units just for playing around...

[asheets]

I meant to say "advertised watt"...

[zap]

Hiya G, here's a little info on that controller. Not sure about the "little yellow one", this one is grey : )

A shot of the guts.

The brains appear to be a Texas Instruments CD4069UBE chip. Just an FYI!

[ghurd]

The 50W is a good deal (for conditions right now).

[ghurd]

Never saw that one before!

The commonly supplied little yellow charge controller 'ICP'-roblems with quite often.

[Drives]

G:

Is this worth the money, and what wattage would you expect it to put out?

http://www.surplusshed.com/pages/item/m3009.html

Thanks,

[zap]

Dean that's probably about 1 watt. If you look through all their solar stuff you'll see a 6"x6" panel that is probably the same panel that is in that light. If you're using it as a light it's probably fine.

http://www.surplusshed.com/pages/item/r3089.html This one probably is the best as far as output.

[ghurd]

I have a couple of those! Somewhere.

Zap is probably right. Maybe about a watt.

It's been a long time. Seems like they are 6V, and (mine) shipped with a tiny dead 6V SLA. We connected it to a drill battery of the proper voltage. It worked as advertised.  The panel had no chance of keeping up with the bulb, around here at least.  I intended to stuff some LEDs in it, never did.

Seems like we used it for a while to charge a 6V drill battery, with the switch to the light part shut off. It worked but not fast enough.

Those are 'really old'. Got mine over 5 years ago, and they were really old when I got them.  They are smaller than they look.

Probably no good for real battery charging, but worth $7 in fun for sure.

[asheets]

That's about $2.67/watt!  Gonna get some of those...

[zyewdall]

Price per watt is commonly what's used in the industry.  For small panels (10watts) around $10/watt is expected for quality ones.  The small amorphous ones aren't as good (good ones will have a 25 year warrantee, or at least a 10 year), and will be cheaper.    Unisolar are the only amorphous ones I would use for projects designed for full time outdoor use.  The others are fine for part time use.  Unisolar are also unbreakable (I've seen them with dents, bullet holes, etc, still working).  For ones bigger than 50 watts or so, I say that anything under $5/watt is good.  Large orders could get under $3/watt last year (large being several MW), but the price has gone up quite a bit this year from the shortage.  Low $4/watt is about the best you can expect even in the MW range it seems.  Mid $4/watt is good for small purchases.

The amorphous ones are about twice to three times the area per watt as the crystalline (blue) ones.

[zyewdall]

Morningstar makes good controllers for these small things.  They are a bit more expensive ($60 instead of $20) because they are not designed as consumer goods in which price trumps quality.  I've used the cheap ones, and gotten several years out of them, but I've got 20 year controllers made for serious PV systems that are still working.  Xantrex, BlueSky, Heliotrope (not in business any more), Outback, and Shell make good charge controllers as well.

[ghurd]

The SG-4 I mentioned is a Morningstar.  

Rated to 4.5A. PWM. Same specs as the SS series, but smaller. Temp compensated even. No green LED. Not adjustable for SLA or flooded. Intended more for SLA, but I have great results for flooded.

Retails around $25.

http://www.morningstarcorp.com/products/SunGuard/info/SG_DataSheet.pdf

[Clifford]

Definately look at price per watt.

Still there may be some variability.  I am still trying to figure out the calculations.

For example, if you are feeding a 12V battery,

Shoot for VOC (Voltage Open Circuit) of around 18-20V for a 12V panel.

Short circuit Amps may or may not represent the number of amps you can push into your batteries.

Note, as you approach the VOC, the power (amps) drops significantly.

Thus, say you have a 12V panel, VOC=20V, With Short Circuit=2 Amps

I presume your Maximum Theoretical Watts is somewhere close to 2 Amps * 12V = 24 Watts (not 40 Watts using VOC in the calcs).

However,

If you are buying bare Cells...  they may be rated on the VOC and Short Circuit AMPS....   So, it may seem as if you have nearly double the power which really isn't there.

I believe that most 12V panels have multiples of 36 individual cells.