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How do you choose which brand and model of PV panel to use?


By Jedon, Section Solar
Posted on Sun Sep 23, 2007 at 08:06:14 PM MST
There is a wide variety, I don't like just picking at random!

I'm trying to pick out the panels for my off-grid system.
Here is what I have come up with so far.
Types: Mono, Poly, Multi - Mono is old tech, poly is new but costs more, multi is newest and costs even more than poly.
Voltages: 16-32V or so, you pick this to match your battery bank voltage?
Wattage: Some 160W cost more than 200W, what gives?
Amperage: So watts = volts  x amps, is it better to have more amps or more volts?
Availability: certainly a concern, I've heard Europe is gobbling up a lot of panels.
Brand: Seems like a few brands dominate ( BP, Kyocera, Sharp etc)and then there are some smaller companies, do they all get their panels from a few suppliers?
Specific Situation: Okay a lot of this seems to come down to how it will be used so here is my situation.
Off Grid - There is no power near by, it's out in the woods in Northern California.
I have plenty of room, 97 acres.
I was thinking of using a 48V HUP battery system
I had initially specced 16 200W Kyocera panels @ $945 each.
Outback MX60 charge controller, 2 Outback 3600W inverters.
I'm thinking I'll use about 600KWh/month or less.

So... What should I look for in a panel?

Thank you!
-Jedon
http://darklingcastle.com
How do you choose which brand and model of PV panel to use? | 25 comments (25 topical)

Re: How do you choose which brand and model of PV (3.00 / 0) (#1)
by Volvo farmer on Sun Sep 23, 2007 at 05:09:14 PM MST

There's a really comprehensive comparison of almost all solar panels on the market in the latest issue of Homepower magazine.

One thing you haven't mentioned is power tolerance. My BP SX170s can be as much as 9% less than their rating under standard test conditions, and still be labeled as a panel with 9% higher output. BP is one of the worst in negative power tolerance. Almost all other brands are minus-three to minus-five percent.

You really should pick up that magazine, they list every specification of over 100 current production panels, and even explains what each specification means.

Volvo Farmer



Re: How do you choose which brand and model of PV (3.00 / 0) (#2)
by TAH on Sun Sep 23, 2007 at 06:52:12 PM MST

If you are going to use an MX-60 charge controller you want to use the highest voltage panels you can find or connect them in series to get a higher voltage that the MX-60 will use. The MX-60 will convert to your battery voltage and you will have less wire loss and need less copper.

If space is not a concern then the lowest cost per watt that you can work with might be the way to go. Buying by conversion percentage only reduces the square footage of panel you need. If you are going to have tracking this could be important too since lower conversion would mean more trackers or bigger. To get 600KWH per month you will need around 5KW worth of panels depending on your average sunlight and if it is fixed or tracking. A thin film setup to average 600KWH per month where I am would be about 1000 sqare feet of panels on a fixed setup. A high output system with dual axis tracking might only need 200 square feet of panel.



Re: How do you choose which brand and model of PV (3.00 / 0) (#3)
by Volvo farmer on Sun Sep 23, 2007 at 07:59:50 PM MST

Just a couple of caveats...

Careful on the maximum voltage of an MX60, a person needs to calibrate for maximum VOC of the panels at their coldest expected winter temperature. It's surprisingly easy to exceed the maximum voltage with a 72V nominal array in below zero temperatures. 140VOC is the limit, and VOC goes up with cold temperatures.

I'm also curious why you even mention a dual axis tracker for off grid use. The gains over a single-axis tracker are rather insignificant, especially in the winter, where off grid solar people are traditionally in their least productive time. For a net-metered array. I might consider dual axis tracking for the summer months, but for off-grid array, my calculations were that it was a waste of time and resources.

Volvo Farmer


[ Parent ]



Re: How do you choose which brand and model of PV (3.00 / 0) (#4)
by TomW on Sun Sep 23, 2007 at 08:15:04 PM MST

Volvo;

I have to agree on the declination angle tracking. I find that seasonal adjustment seems fine. I think the difference in even a months angle to horizon is not significant enough to track constantly. But, I doubt it will hurt anything or use much energy over just daily horizon to horizon tracking if the hardware is there already.

Cheers.

TomW

The Truth is the Truth, even if no one believes it; and a lie is a lie even if everyone believes it


[ Parent ]



Re: How do you choose which brand and model of PV (3.00 / 0) (#5)
by TAH on Sun Sep 23, 2007 at 09:27:28 PM MST

I did say the highest voltage that the MX-60 can use. I don't know if other panels vary a lot more but mine are listed as 40VDC and they run from 35 to 55VDC from 10 below OF to 95F on the input side of the MX-60's.
As for the dual axis, if you are putting up tracking the extra would not add that much and it would save regular manual adjustments. If the mechanism is there for vertical tilt motorizing it shouldn't make it any weaker. I have a fixed array because I really didn't want a tornado to take a lot of expensive parts. Last summer I had several 3ft diameter oak trees blown down less than 1000ft from my panels and didn't loose any panels just a small windmill. I am thinking about a tracking reflector to get some gains in the morning and afternoon but I might just add more panels with some fixed SE and some SW.

[ Parent ]


Re: How do you choose which brand and model of PV (3.00 / 0) (#6)
by Jedon on Mon Sep 24, 2007 at 02:26:08 PM MST

Volvo farmer:
Thank you, I'll pick up that issue of homepower right away.

TAH:
It sounds like you are saying that since space isn't a concern that perhaps using monocrystalline panels that are cheaper per watt would be a good idea?

I hadn't planned on using tracking, I talked to a guy near me who has some panels tracked and some not and he suggested just buying more panels with he money saved on a tracker.

We don't have really extreme weather here, we do get snow but I've never seen it get below 20F or so and summer temps are usually in the 90's at the hottest.

I'm not sure I'm getting the whole thing about input voltage to the MX60, is it being said that since the deviation of the panels could be 9% that I could put too much voltage into the MX60 on a high output day and fry it?

I know I need 5KW of panels but I can't really afford that right now so I'll get 3.2KW of panels and probably have to use the generator some, then hopefully next year I can put in the micro-hydro to supply the rest of the power.

Thank you both for the advice!
-Jedon

[ Parent ]



Re: How do you choose which brand and model of PV (3.00 / 0) (#8)
by TAH on Mon Sep 24, 2007 at 06:15:25 PM MST

The MX-60 is a mppt charge controller and will accept panel voltages much higher than your battery bank and step the current up/voltage down to the charge voltage you need. The higher voltage generally means less loss in cables and connections.

If you are not going to be tracking and 5000 watts of any type of panel is a lot of square footage to be hanging on trackers. Building a homemade tracker out of a satelite dish won't be much of an option. You can get 5120 watts of thin film for $15,000 right now.

[ Parent ]



Bull Droppings (3.00 / 0) (#7)
by TomW on Mon Sep 24, 2007 at 04:49:09 PM MST

jedon;


I talked to a guy near me who has some panels tracked and some not and he suggested just buying more panels with the money saved on a tracker.

I would suggest that depends on the size of the array and the tracker and is somewhat irresponsible "general" advice that may have been accurate in 1960. Next someone will say the panels use more energy to create than they will produce. Which is another often regurgitated bit of misinformation.

My tracker cost very little compared to even 10 watts more PV and I know it pays back on the expense every day.

If you are the "has to buy everything" type it may hold true but for most that I know it is well worth the cost / time to do.

Just reality checking in.

Tracking 300 watts of PV every day and proving the anti tracking "experts" wrong every day as well.

It is your money and time but check into what other guys like allan from down under who relies on PV daily has to say on the subject before accepting that neighbors well meaning advice.

I am always amazed at the bad advice people will blindly follow from someone who probably bought their whole setup and achieved expert status pass out. Not saying it is the case for your neighbor just a trend I see.

Cheers.

TomW.

The Truth is the Truth, even if no one believes it; and a lie is a lie even if everyone believes it




Re: Bull Droppings (3.00 / 0) (#9)
by DanB on Tue Sep 25, 2007 at 09:38:15 AM MST

Yes - Tom and others have changed my thinking somewhat on this over the years.  Overall I think Tom is right, you have to balance the cost of the tracker against the size of your arry.  Much like buying an expensive MX60 - below a certain point it doesn't make sense but at some point it definitely becomes very cost effective.

It also depends on the site to some degree.

[ Parent ]



Re: Bull Droppings (3.00 / 0) (#10)
by Jedon on Tue Sep 25, 2007 at 10:22:42 AM MST

"My tracker cost very little compared to even 10 watts more PV and I know it pays back on the expense every day."

Did you make your own tracker? I'm not quite a "has to buy everything" guy but neither am I a highly skilled fabricator, I'm a software not hardware engineer :-)

I'm not against tracking, just didn't see how to do it economically with so many panels, maybe with thin film it would be possible?

Where can I get 5KW worth of thin film for $15K? I'd be very interesting in that!
Thanks!
-Jedon

[ Parent ]



Re: Bull Droppings (3.00 / 0) (#12)
by TomW on Tue Sep 25, 2007 at 11:19:35 AM MST

jedon;

Here is my setup mounted on an old C band satellite dish with a rack made by a friend who really knows how to weld. I am not entirely happy with the actuator mounting but it has worked fine going on 5 years now:

http://www.anotherpower.com/gallery/album57/100_0417

Only 300 watts but if I had a larger array like you talk about then a Traxle ground mount would be the way. That style could be built to hold a lot of panels and is quite easy to construct but takes some real estate.

Everyone needs to make their own decision based on local conditions, personal skills and resources. This is why absolute statements can often be wrong.

Cheers.

TomW

The Truth is the Truth, even if no one believes it; and a lie is a lie even if everyone believes it


[ Parent ]



Re: Bull Droppings (3.00 / 0) (#11)
by ghurd on Tue Sep 25, 2007 at 10:48:02 AM MST

Could be he has a junk tracker too.  They made a lot of different junk trackers.
Some track based on the temperature, following the idea the later in the day, the higher the temperature. They did it with some kind of refrigerant, IIRC. If a cold front came through at 2PM the tracker went back to facing East.

It would be economical with so many panels because it wouldn't need as many panels.
Beware of the $3/W thin-film companies.
G-
Ghurd.info
[ Parent ]



Re: Bull Droppings (3.00 / 0) (#13)
by Jedon on Tue Sep 25, 2007 at 11:41:36 AM MST

I would think it's a matter of math, if a tracker increases power production by 15% then a 3KW fixed array would be 3.6KW tracked. 600W worth of panels would be around $3K so the cost of the tracker plus increased installation costs would have to be under $3K to make it worth it. If you can make your own tracker for $1K then it would be worth it, and in the case of smaller arrays where the hardware doesn't have to be super beefy it's easier to make the tracker so it's more likely to be worth it.

"Beware of the $3/W thin-film companies."

Which ones and why? Are they unreliable? De-laminate? Don't operate to listed specs?
Thanks!
-Jedon


[ Parent ]



Re: Bull Droppings (3.00 / 0) (#16)
by ghurd on Fri Sep 28, 2007 at 08:50:19 AM MST

I know of some that must be over 10 years old and still 'fine' according to the owner.

From the post linked below, I find it interesting...
One month, happy. (not a $3/W PV)
One year, not happy. (was happy for 6 months)
Two years, not happy. (was happy for 1 year)
One and a half years, happy.
One year, happy.
http://www.fieldlines.com/story/2007/9/4/202849/9400

Makes me wonder where are all the 5 and 10 year old 'considerably lower than market price' thin-film PVs, or the companies that made them.
G-
Ghurd.info
[ Parent ]



Re: Bull Droppings (3.00 / 0) (#19)
by TAH on Fri Sep 28, 2007 at 06:47:59 PM MST

"Makes me wonder where are all the 5 and 10 year old 'considerably lower than market price' thin-film PVs, or the companies that made them"

I have seen 20+ year old chronos arrays that were still putting out good power. I have some of these and they are crappy compared to the EPV panels. The EPV are two layers of saftey glass with the thin film applied to the plastic in the middle. This is built the same as a car windshield and they warranty the output for 20 years the same as other companies. I don't know how many years they have been building these but I have only had them for a year and half so that's all I go by. If I had any other panels it would be a year and half for those too.

[ Parent ]



Re: Bull Droppings (3.00 / 0) (#21)
by ghurd on Fri Sep 28, 2007 at 07:32:58 PM MST

And I have thrown piles of them in dumpsters, even if I didn't spell it right...
http://www.fieldlines.com/?op=search&offset=0&old_count=30&type=comment&section=& ;string=chronar&search=Search&count=30

Ghurd.info
[ Parent ]


Re: Bull Droppings (3.00 / 0) (#14)
by powerbuoy on Thu Sep 27, 2007 at 05:43:13 PM MST

Ghurd:

What's wrong with the $3.00 EPV thin films? ... I believe that's what TAH has on his roof and he seems to like them  ...

Powerbuoy

[ Parent ]



Re: Bull Droppings (3.00 / 0) (#15)
by TAH on Thu Sep 27, 2007 at 06:54:58 PM MST

Yes I have 62 of them on my roof now and I am going to put another 34 up. I started hanging unistrut today. I don't see how they would delaminate since they are built the same as a car windshied and I haven't seen one of them delaminating. Today the panels on the are over 1 1/2 years old, are on a fixed roof that is only at the correct angle in May and Aug. Solar output for this latitude should be around 900 WPSM right now. I was getting over 90% of the rated output when I looked at the meter at 2:30.
They take up more room but only 200 sq ft per kW. I would think just about any house would have at least 200 square feet of roof or wall facing somewhat south. Some people claim that side by side with crytaline type panels these will output 20% more per day per watt. I have some mono and some poly crystal panels that put out nothing on cloudy days when the thin film are doing 30% of the rated output. When I can afford it I will probably be getting some more of these.


[ Parent ]


Re: Bull Droppings (3.00 / 0) (#17)
by powerbuoy on Fri Sep 28, 2007 at 01:11:41 PM MST

TAH:

I just went thru all the literature that I picked up at the Solar Expo in Long Beach. Going over the homepower magazine I could not help but wonder if the house that's shown on Atens advertising for thin films is actually yours? If that's not the same pic as from a previous post then I'll be damned.
I hope that you are not a little bit too biased when praising these panels since you are obviously selling them ...

PB





[ Parent ]



Re: Bull Droppings (3.00 / 0) (#18)
by TAH on Fri Sep 28, 2007 at 06:05:06 PM MST

They never told me that they used my picture. I haven't sold any of these to anyone else yet. I would sell them and not make much off them if anyone wants some but only because I have had them on my house and I am happy with them. I am working with a group in Greece to do a large scale project with these and if that works out I hope to make a little money besides.

[ Parent ]


Re: Bull Droppings (3.00 / 0) (#20)
by ghurd on Fri Sep 28, 2007 at 07:13:19 PM MST

My above post included someone 'happy with $3/W thin-film' to the one and a half year point.  Please disregard that particular installation.
Notice, at this moment, people responding to the link shown earlier have nobody happy for over 1 year.

"I haven't sold any of these to anyone else yet" ?
"working with a group in Greece to do a large scale project with these and if that works out I hope to make a little money" ?
Both sound more than a bit questionable in the bias department.

I admit a bit of skeptic bias when all someones posts are related to selling the same product.
I admit a bit of bias when I personally go fix what I sell.
I admit a bit of bias when a large percentage of my #800 phone calls are related to me attempting to fix someone else's junk too.

Maybe your picture is the biggest installation they have ever done?
Maybe your picture is the biggest installation they have still working?
I never saw one, so I won't even guess.

If they used your picture without permission, I bet they send those 34 PVs you want for free.  That's fairly cheap, <$3k (their cost) for a commercial image.  They might even fed-ex them!
G-
Ghurd.info
[ Parent ]



Re: Bull Droppings (3.00 / 0) (#22)
by TAH on Fri Sep 28, 2007 at 07:41:56 PM MST

I would not sell anything like this without trying it.

They did not give me any free panels but I would like some. I paid more than the current price.

Aten is a distributer and not the manufacturer. They asked me for a picture a while ago but never said that they were going to use it for advertising.

EPV only sells containers directly so someone is doing a whole lot bigger installs since a container will hold at least 1000 panels.

Since you sell panels to people even though I don't doesn't that make you suspect and biased by your rules?

The people I am working with are planning a multi megawatt installation. I got involved with them recently by through a completly unrelated project.I brought these up as an option because they have worked better than any anti-thinfilm people have said. I won't be selling them any panels they will buy enough to deal directly with the manufacturer. I will be working with them on the electrical and structural parts of the project.
I originally bought my panels to power my house and they work well. If I can get someone a lower price on panels I will.

[ Parent ]



Re: Bull Droppings (3.00 / 0) (#23)
by ghurd on Fri Sep 28, 2007 at 10:19:29 PM MST

Their (EPV) websites will not open at this time.
Guessing a container is 150KW. Probably more.
Guessing they don't have any 5 year old installations.
HF PVs have a longer track record for "trying it"?

If Yousri Abdou didn't ask permission, might want to ask him why.

"Since you sell panels to people even though I don't doesn't that make you suspect and biased by your rules?"
I said I was bias.  Which brand am I pushing people to?  What brands do I sell, or currently have in stock?

I can see what you are saying, "my cheap PVs worked for 18 months so far".
I am saying "quality PVs work for decades".
Ghurd.info
[ Parent ]



Re: Bull Droppings (3.00 / 0) (#24)
by TAH on Sat Sep 29, 2007 at 09:44:20 AM MST

I sent him an email asking about it.

Thin film panels have and do work for decades. Some have several problems that I don't believe these have. Many loose 20% or more of the output in the first couple of months of use. 18 months and no output loss.
Some of them delaminate. The contruction of these makes that very unlikely. Not anymore likely to fail that way then any expensive panels.
Some discolor soon after being in the sun. So far I have none of this.  

Chronos panels were a low quality cheap panel and they will last for many years. I have seen two 1KW arrays that were over 20 years old and still wroking. Chronos are one layer of glass with a plastic substrate that peels off easily. The electrical connection is not good. They discolor very soon after being put into use. They can loose 20-30% of the output within a couple of months. They don't have a good mounting system. And still one of the sites I looked at still output 80% of rating after 20 years.
I don't know of any current panels of any kind that are built exactly the same as they were twenty years ago with the same materials and processes so a quality PV may fail early. How many Evergreens bursting have you heard of? I have a few monocrystals Siemens that are effectively dead and only 15 years old and 4 thin film panels from the early 80's that still work and give me 20 watts each 1ft x4ft panels no name or labels on them so I don't know the original rating.  


[ Parent ]



Re: Bull Droppings (3.00 / 0) (#25)
by veewee77 on Tue Nov 06, 2007 at 08:53:27 PM MST

And the guy who sold said neighbor would like to sell more panels than less panels and a tracker because stationary panels don't require as much labor to install. The difference between track and no track on a decent sized array could mean the cost difference between the tracker and the panel, and truth be told, it might even be less expensive to take array of X size and put it on a tracker than it would be to add enough panels to make up the difference.

The panels work best when the sun is within a 15 degree span of directly in front. So, if you have 5 hours of sun (you are lucky if you do) you will have only about 1 of those at peak output without tracking, and nearly all 5 at peak output with tracking. . .
You decide. . . Those panels are expensive. . . get more out of them by tracking.

JMHO - YMMV

Doug

[ Parent ]



How do you choose which brand and model of PV panel to use? | 25 comments (25 topical)
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