Author Topic: Solar Panel backing?  (Read 5348 times)

0 Members and 1 Guest are viewing this topic.

juiced

  • Full Member
  • ***
  • Posts: 243
Solar Panel backing?
« on: November 03, 2004, 07:14:45 AM »
Was i supposed to put some kind of backing on my PV mount? I have basically two tubular pieces of metal, bent into a triangle with bolt-holes drilled in. The mount bolts into the space behind the rear seats and before the glass (in my car). The PV bolts onto the mount.


  I didnt put backing for heat reasons. Should i install a REALLY shiney piece of sheet metal across the back of the frame/panel to catch more light? (i guess it would also serve as protection...)


   I alwas thought the only thing you put behind panels is a pasive heater sys.

« Last Edit: November 03, 2004, 07:14:45 AM by (unknown) »

ghurd

  • Super Hero Member Plus
  • *******
  • Posts: 8059
Re: Solar Panel backing?
« Reply #1 on: November 03, 2004, 07:21:48 AM »
Factory made is fine like it is.  I hope!

Circulation is good.

G-
« Last Edit: November 03, 2004, 07:21:48 AM by ghurd »
www.ghurd.info<<<-----Information on my Controller

juiced

  • Full Member
  • ***
  • Posts: 243
Re: Solar Panel backing?
« Reply #2 on: November 03, 2004, 07:39:38 AM »
Hey! Good morning. I see im not the only coffee-surfer.. :p


  If my panel is 'cooled' by an external means, i.e. dry ice, nitro or something else, would it improve effiecancy?

« Last Edit: November 03, 2004, 07:39:38 AM by juiced »

troy

  • Full Member
  • ***
  • Posts: 227
Re: Solar Panel backing?
« Reply #3 on: November 03, 2004, 07:51:20 AM »
 A cold panel is a happy productive panel.  But efficiency would also depend on where the cold came from.  Making cold can be just as energy intensive as making hot.


I have actually seen slightly higher than rated output from my two panels on a very cold very clear day around solar noon.


Best regards,


troy

« Last Edit: November 03, 2004, 07:51:20 AM by troy »

ghurd

  • Super Hero Member Plus
  • *******
  • Posts: 8059
Re: Solar Panel backing?
« Reply #4 on: November 03, 2004, 11:34:36 AM »
I'm supposed to be working on work work. Seem to be working at play work.


Any decent panel is made for temps. it would see in the sun. The chemicials are balanced for that. It may pick up a little, but I would be suprised if it was over 3-4%. It may even screw something up. Either way, I can't see it ever being worth the bother or cost. It may even lower the output. I've never seen any charts that go to temps that low.


The over heating concern is more to keep the temps down to what it was designed for. If its nailed down on a 130' roof with no circulation, it is like a solar collector, and they are not designed for the kind of heat it will see. I've seen them so hot you couldn't touch them long. Eventually it will damage the PV, commonly refered to as 'burned' cells or panel.

« Last Edit: November 03, 2004, 11:34:36 AM by ghurd »
www.ghurd.info<<<-----Information on my Controller

nothing to lose

  • Hero Member
  • *****
  • Posts: 1538
Re: Solar Panel backing?
« Reply #5 on: November 03, 2004, 02:43:27 PM »
I geuss the answer is the heat issues?


I have often wondered why they don't just make solar pannels to be installed as part of the roofing system in new construction or when replacing old roofs. That would make alot of sense really. I mean if you could do away with 75% of the normal roofing ( plywood, felt, shingles, etc...) and the labour that takes, then solar pannels would look much better from a cost perspective. Imagine the entire roof (sun side) being built from all solar pannels. That would really drop the price compared to building a normal roof and then adding the pannels as extras latter! That type of pannel might cost a little more, but there could be large savings in the long run!


Also they could build in water cooling for the pannels and create solar hot water at the same time as one system. Maybe use a safe antifreeze system and a heat exchanger elsewhere in the house or yard depending if you needed the heat or not, winter or summer.


Since it is very common to have metal roofs, especailly in the south US  that would not be a problem. Interlock the pannels and use stripping to make them leak proof like a normal metal roof and insulate under the pannels same as a normal metal roof.


Heck think if trailer houses had solar pannel roofs instead of the thin sheet metal ones they actually do have!

« Last Edit: November 03, 2004, 02:43:27 PM by nothing to lose »

TomW

  • Super Hero Member Plus
  • *******
  • Posts: 5130
  • Country: us
Re: Solar Panel backing?
« Reply #6 on: November 03, 2004, 02:56:31 PM »
ntl;


I have seen a shingle / solar panel integrated into one piece at a couple of energy fairs. Very expensive but very neat idea I think. No idea what the company name was tho. It was basically a 3 tab shingle with the exposed part being a panel also forgot the specs but not as good as a normal panel if I recall correctly.


Cheers.


TomW

« Last Edit: November 03, 2004, 02:56:31 PM by TomW »

Ungrounded Lightning Rod

  • SuperHero Member
  • ******
  • Posts: 2865
Re: Solar Panel backing?
« Reply #7 on: November 03, 2004, 03:14:51 PM »
... forgot the specs but not as good as a normal panel if I recall correctly.


If you're covering your roof you can get away with lower efficiency in trade for lower cost.


Two downsides of solar shingles:

 - They absorb more solar heat, requiring better attic insulation or venting.

 - They're still too low volume and too expensive to be practical compared to purpose-built panes.


The latter is a vicious circle - which becomes a "good thing" once broken.  When a low-cost panel material is developed which is suitable for automated manufacture as a shingle component (raising the shingle price less than the cost of a discrete panel instalation), such solar-roof shingles will become practical.

« Last Edit: November 03, 2004, 03:14:51 PM by Ungrounded Lightning Rod »

BT Humble

  • Sr. Member
  • ****
  • Posts: 475
Re: Solar Panel backing?
« Reply #8 on: November 03, 2004, 03:33:59 PM »


Any decent panel is made for temps. it would see in the sun. The chemicials are balanced for that. It may pick up a little, but I would be suprised if it was over 3-4%. It may even screw something up. Either way, I can't see it ever being worth the bother or cost. It may even lower the output. I've never seen any charts that go to temps that low.


My primary solar PV system is made up of four Shell SR140 panels.  They're each rated at 4.25A continuous or 4.5A max current[1].  On a sunny, cold windy day in the middle of winter I saw a peak output into my batteries of 20A.  That works out to be about 10% extra, and is why it's always a good idea to have a solar regulator that's rated about 25% higher than the maximum output of your array.


BTH

[1]  24V panels, and I'm going from memory since I don't have the spec sheet in front of me righ now.

« Last Edit: November 03, 2004, 03:33:59 PM by BT Humble »

baggo

  • Jr. Member
  • **
  • Posts: 83
Re: Solar Panel backing?
« Reply #9 on: November 03, 2004, 04:25:32 PM »
There is a company here in the UK that supplies solar roof tiles to be fitted to new houses or as a replacement for existing roof tiles:


http://www.solarcentury.co.uk/content.jsp?sectno=4&subno=8.


The cost quoted for sufficient tiles to produce 2 kW is between 18,000 and 20,000 UK pounds depending on the type of tile which is about double the cost of the equivalent standard panels. It would possibly be a viable proposition if you needed to re-roof your house at any time and the aspect was suitable i.e plenty of south facing roof area. There are also grants available up to 50% of the cost of installation but, as is often the case, the grants are not available for DIY projects.


The systems that this company installs are all grid tied with no storage so it is possible to 'sell' surplus power back to the generating companies (if you can find one that will pay you for it!) but as there is no facility to store surplus power, you still have to use grid electricity at night and when the sun doesn't shine. I presume the idea is that what you sell back offsets the cost of what you have to buy. Hmmm, perhaps not such a good idea.


John

« Last Edit: November 03, 2004, 04:25:32 PM by baggo »

nothing to lose

  • Hero Member
  • *****
  • Posts: 1538
Re: Solar Panel backing?
« Reply #10 on: November 04, 2004, 05:25:56 AM »
"The systems that this company installs are all grid tied with no storage so it is possible to 'sell' surplus power back to the generating companies (if you can find one that will pay you for it!) but as there is no facility to store surplus power, you still have to use grid electricity at night and when the sun doesn't shine. I presume the idea is that what you sell back offsets the cost of what you have to buy. Hmmm, perhaps not such a good idea. "


Well I am glad to know some of the companies do have the right idea and trying.

I think with the above mentioned grid tie it would still be a simple thing to add your own batteries and remove the grid. I mean as long as you have the pannels and they produce the power then you should be able to use them anyway you would use other pannels, just have to buy all the extras as extras, batteries, controllers and whatnots. Hopefully you would not be required to buy alot of un-needed grid tie hardware you don't want just to get the shingles/pannels.


I am thinking more of a pannel about 3' wide and various lengths like 8' 10' 12' etc.. That's about what normal metal roofing and metal siding comes in. So if the pannel was made as such and you install it same as you would the normal metal roofing sheets I see no real difference unless the glass glazing magnifies the heat? More than the normal metal roof would get? Ever climbed a metal roof in the south on a hot AUG day at noon?? Will about melt your tennis shoes! If a protective cover that does not magnifie the heat nor block the sun were used then I would think you'd have the same heat as a normal metal roof. Most likly same problems like condinsation and have to use a moisture barrier also or it would be raining in your attic at times, not outside, just in the attic.


If the pannels were made in a standard 4'X4' size and interlocked together like metal roofing it should work. Small water cooling system for the pannels and hot water for the house should solve the heat problems, then insulate like a normal metal roof.

« Last Edit: November 04, 2004, 05:25:56 AM by nothing to lose »

ghurd

  • Super Hero Member Plus
  • *******
  • Posts: 8059
Re: Solar Panel backing?
« Reply #11 on: November 04, 2004, 10:10:23 AM »
Uni-Solar makes them.


VERY expensive.  VERY, VERY, VERY.


And it looks like you would need a lot of Union roofers and Union electricians to get them installed.


G-

« Last Edit: November 04, 2004, 10:10:23 AM by ghurd »
www.ghurd.info<<<-----Information on my Controller

Joel

  • Newbie
  • *
  • Posts: 34
Re: Solar Panel backing?
« Reply #12 on: November 04, 2004, 07:18:12 PM »
Agreed on the solar shingles.  I believe I remeber correctly when I saw a show exploring this option stated that the southern face of a standerd 2 story, 2000 sq. ft home would cost $30,000 to shingle in solar shingles.  Heck of a lot of arrays can be bought for that kind of money...


Joel

« Last Edit: November 04, 2004, 07:18:12 PM by Joel »

nothing to lose

  • Hero Member
  • *****
  • Posts: 1538
Re: Solar Panel backing?
« Reply #13 on: November 05, 2004, 09:14:01 AM »
I think it cost 10 or $20,000 about 10 years ago to put an all new roof on a barn my mother has now. Plywood, felts, Shingles, ect.. only thing not replaced was structeral members. And that was a lousy job too! I can look at the roof from the ground and see warps, buckles and waves rolling across it, but at least it does not leak and looks good if you don't look close.


Something like that would have paid for itself many times over now with solar panel roofing like I mentioned. Just a moisture barrier and interlocking panels to roof it.

 Open drafty barn so heat inside is not a problem.


Her house was using electric hot water heat about 100-200' away too. So winter cooling of the panels (if needed) could have saved a ton in electric hot water heating. Durring the summer still heat the house hot water tank and if needed just waist the rest of the heat, or find some other use for it.


Figuring the cost of the normal style roof she got off the cost of solar and the large area to cover, her normally ridiculous electric bill would have paid the differnce about now I think for the whole setup includng some batteries. Most of the bill is hot water, electric hot water heat.


And the house roof is nearly as big as the barns, and its a new house (about 10yrs).


She doesn't listen to anything I say, so of course it's all electric and propane. No RE at all!

 If I inherit the house someday I will either sell it and send the kid to collage or just burn it down and use the barn for storing cars!

« Last Edit: November 05, 2004, 09:14:01 AM by nothing to lose »