Who makes the most effcient solar panel in the $1.50 to $2/watt range?

rollandelliott

Who makes the most effcient solar panel in the $1.50 to $2/watt range?
I was looking at sunpower panels and the fact that they would take up 1/3rd less space was really nice, but they aren't sold to the DIY'er.

What's the next best/efficient panel in the $1.50 to $2/watt range?

I have a feeling they are all about the same effciency at that price point, but maybe I'm wrong.

Solar Guppy

Re: Who makes the most effcient solar panel in the $1.50 to $2/watt range?

Evergreens, best performance and tolerance cell on the market

When I did the math on Sunpower is was less than a 10% area savings when I compared to Evergreens watts / size

ggunn

Re: Who makes the most effcient solar panel in the $1.50 to $2/watt range?

Solar Guppy wrote: »

Evergreens, best performance and tolerance cell on the market

When I did the math on Sunpower is was less than a 10% area savings when I compared to Evergreens watts / size

Get 'em while you can. Evergreen appears to be history.

Solar Guppy

Re: Who makes the most effcient solar panel in the $1.50 to $2/watt range?

ggunn wrote: »

Get 'em while you can. Evergreen appears to be history.

What are you talking about?, they are simply going to walk from there debts in Bankruptcy, company is and will be fine, if not better without the debt.

ggunn

Re: Who makes the most effcient solar panel in the $1.50 to $2/watt range?

Solar Guppy wrote: »

What are you talking about?, they are simply going to walk from there debts in Bankruptcy, company is and will be fine, if not better without the debt.

Time will tell....

RCinFLA

Re: Who makes the most effcient solar panel in the $1.50 to $2/watt range?

I will probably take the wrath of many but I prefer monocrystaline cells.

Maybe it's my background from semiconductor industry which requires an obsession with low defect density.

PV cells can stand a high defect rate and still have an acceptable performance.

Polycrystaline has a large number of defects by default due to the random crystal grain orientation interfaces.

There are poor monocrystaline wafers also produced with high defect count.

Defects provide low resistance shunt paths. These shunts usually do little to effect the overall current production but can be sites for hot spots to develope during shading that can create additional damage to the cell that will eventually effect production.

Most of the really rotten wafers are weeded out by commercial panel manufacturers specification requirements, and end up on eBay for sale to DYI's panel builders.

rollandelliott

Re: Who makes the most effcient solar panel in the $1.50 to $2/watt range?

"and end up on eBay for sale to DYI's panel builders."

I've head this so many times with absolutely no information to back it up. How would anyone know where these cells come from and if they are sold on ebay or not? It gives ebay a bad name when most sellers I've dealt with are pretty honest. Yeah there are scams out there, but poisoning the well is not the right thing to do.

niel

Re: Who makes the most effcient solar panel in the $1.50 to $2/watt range?

don't get your tathers in a tither.:p

if you would you rather believe they sell the best cells for diy and keep the bad ones for pv modules so be it. don't make it so.

tmarch

Re: Who makes the most effcient solar panel in the $1.50 to $2/watt range?

Solar Guppy wrote: »

What are you talking about?, they are simply going to walk from there debts in Bankruptcy, company is and will be fine, if not better without the debt.

How many of us would be better without our debt???????????:roll:

rollandelliott

Re: Who makes the most effcient solar panel in the $1.50 to $2/watt range?

"if you would you rather believe they sell the best cells for diy and keep the bad ones for pv modules so be it. don't make it so. "

doesn't really matter to me, DIY is more expensive anyways for large solar systems and I'm never gonna buy them, but I'll bet everyone who claims ebay sells junk cells has never ever bought cells off ebay, they are the ones that are making false accusations. It's like saying all Chinese panels are junk, a vauge useless generalization. One bad apple does not spoil the bunch. Besides by that logic one would have to conclude that any manufacturer on ebay only sells their lesser quality junk. I know from first hand experience that is false.

anywho, back to the topic... I have some ever green 215w panels. The 240w sunpowers for a 10k array take up 1/3 less space if their web site specificaitons are correct. By the lack of responses I'm guessing there isn't any other panels besides sunpower that are known to take up less space.

Cariboocoot

Re: Who makes the most effcient solar panel in the $1.50 to $2/watt range?

RCinFLA wrote: »

Most of the really rotten wafers are weeded out by commercial panel manufacturers specification requirements, and end up on eBay for sale to DYI's panel builders.

The bold is still mine. People do need to understand this; that the cells sold freely through many sources are ones the factories have rejected.

That does not mean they are all 100% no good.

It does mean that when you buy lots of cells to build your own you should test each cell individually to make sure all the ones going in to your panel are at least consistent even if only 80% up to snuff. Unfortunately most people don't do this because it's not easy to do (nor do they know they should).

As far as panel efficiency is concerned, RCinFLA is spot-on about monocrystaline panels. However, they tend to cost more. So do the "dual" panels. As in the other thread about "military" panels; how much do you want to pay? In practical terms it comes down to $ per Watt and can you fit enough of them on the roof?

If efficiency is the only issue, there's lots of things you can do to boost that - starting with dual axis trackers. The thing is, it all costs money. Lots of money. And the power return on that investment can be pretty meager compared to just buying more 14% efficient polycrystaline panels.

RCinFLA

Re: Who makes the most effcient solar panel in the $1.50 to $2/watt range?

The part that is not realized by many DYI'ers is low shunt resistance can get them in real trouble. They get good output at full sun and think things are wonderful.

Again, many DYI'ers don't realize the need for bypassing diodes within the cells of the panel.

When a cell gets shaded, and it can be just a leaf that lands over a single cell or a bird flying by that lets go a large load, so that cell stops producing. The other cells force the blocked cell into a high voltage reverse bias condition.

If the shunt resistance is low, 10 ohms or less, the high reverse bias voltage causes a great deal of heating on the cell. If the low resistance is concentrated at a single dominate leakage point on the cell it can get very very hot, enough to melt the solder tabbing connection on the cell. This in turn can create sparks and potentially start a fire.

3 to 10 ohms of shunt resistance has little effect on maximum illumination current output from a cell. 0.5v divided by 3 ohms is only 167 mA of current loss.

When there is a number of cells in series, and one cell gets blocked, the other cells in the series loop drives the block cell into reverse bias. If there are 36 cells in a panel, there will be 35 x 0.5 vdc or 17.5 vdc of potential reverse bias on the blocked cell. The current will be limited to the normal maximum Isc current, but this may be 4 to 5 amps.

If the cell has 3 ohms of shunt resistance and there is 17.5 vdc reverse bias, or 4 amps of available current from the other cells, on the blocked cell there will be 48 watts of potential heat dissipation on the block cell. If concentrated in a small area, this will get the cell very hot and potentially melt solder. It also can further degrade the cell defect and make the shunt resistance worse.

Commercial panel manufacturers usually limit the cell leakage resistance to 10 ohms minimum by sorting and place bypass diode every 20 to 24 series connected cells maximum in order to limit the maximum reverse bias to about 10 vdc.

DYI'ers should test each cell they use by applying a reverse bias of 10 vdc, with cell covered so it is dark, and throwing out any cell that draws more then 1 amp during reverse bias test. They should also place bypass diodes every 12 to 20 cells.

Failure to test the cells for excessive leakage current can get you this.

bmet

Re: Who makes the most effcient solar panel in the $1.50 to $2/watt range?

While that's a possibility, there's no way to know which other factors contributed to that picture. Everything about that particular installation bared witness to a lack of information, experience, and detail. Even newbies (like myself) were shaking our heads.

BB.

Re: Who makes the most effcient solar panel in the $1.50 to $2/watt range?

That photograph is from (I think) this thread:

Panel Fire Question

We know many of the issues that went into causing the fire--We (here) do not know if low shunt resistance for a cell was a cause for this particular fire or not (I believe it was delamination of the copper cell to cell or even copper bonding to cell face failing due to flexing/wind/water damage causing arcing/ignition of the plastic panel case). We do know why it spread (plastic panels).

There are many way for things to go wrong--And with vendors able to sell cells of unknown quality/heritage on EBay--it will probably only be a matter of time before some smart lawyer/engineer/DIY'er puts 2+2 together and sues everybody in sight (deep pockets theory of liability) over these bulk/raw solar cells starting a fire (whether it was the cell's fault or not).

-Bill

bmet

Re: Who makes the most effcient solar panel in the $1.50 to $2/watt range?

That installation reminds me of something I did years ago while volunteering for a local video producer.

Sometimes the County doesn't have funds for professional support, and my Producer claimed he could properly illuminate a boxing arena in a venue which lacked that infrastructure.

Bailing wire and duct tape, to hold various 'shop' lights, in an overhead circle above the boxer's ring. All was fine until the fight began, the swaying shook things loose. One set of lights almost hit a boxer, but to their credit the competitors finished the event.

Today I have the knowledge and experience of a seasoned Roadie to know how it's supposed to be done. I"ll never be pressured to chicken-wire something like that again. When I see those photos of burned panels, it reminds me of how important it is to have the right tool for the job, including professionals.