Author Topic: Solar ROOF preacticality? (Read 3360 times)

Psycogeek · « **on:** March 14, 2005, 03:58:08 AM »

More stupid ideas from the psyco.

When we build solar systems, they are generally going on roofs , especially where i would want to do a new build at, it would be in an area where there are trees , unlke development stripping and re-landscaping.

so the roof is the most practical location to keep the trees from shading the solar pannels.

What i have been seeing is Doubble roofs (in my mind) they put a roof on the house, then another roof of solar pannels on the house. this increases the load on the roof, even though it might shade the house better.

What is the practicality of building a roof OF solar pannels? not shingles but that the top wood on the trusses is the backing plate for the cells.

how the heck would a person go about that?

Modularly

sealing up the roof from the elements

construction time, if it rained on ya

fragility

repairability (years later)

vents that need roof access

what ideas would you have for accomplishing a task that different and difficult, although logical for a new solar build house?

Shadow · « **Reply #1 on:** March 13, 2005, 09:08:44 PM »

I would think the insulation factor would be nil. A problem this far north. And farther south I would worry about too much heat in the attic, spontaneous combustion comes to mind.

TERRYWGIPE · « **Reply #2 on:** March 13, 2005, 09:22:14 PM »

I'M A ROOFER AND ALTHOUGH I'VE NEVER WORKED WITH OR PHYSICALLY SEEN THEM I DID SEE A SOLAR ROOFING SYSTEM, IT WAS ON ONE OF THOSE HOME-EMPROOVEMENT SHOWS, I THINK "THIS OLD HOUSE",YOU MAY WANT TO EMAIL THEM AND CHECK IT OUT. IT LOOKED SOMETHING LIKE VINAL SIDING

TERRY

BT Humble · « **Reply #3 on:** March 13, 2005, 10:18:46 PM »

If you go to Home Power magazine (http://www.homepower.com) their current issue has a good story about roof-integrated solar on page 56 (it's a free download).

The previous issue also had a good story about a roof-integrated installation in NYC, let me know if you're interested.

BTH

nothing to lose · « **Reply #4 on:** March 13, 2005, 10:32:33 PM »

Most people don't like all caps, normally considered shouting also.

I think the problem with solar roofing is the current design of the pannels basically.

This is something I have givin alot of thought. It does make alot of sense to simply eleminate the normal roof (and cost) and use the pannels as the roof itself. It's not very do-able though!

Solar pannels get very hot as I hear, alot of talk about how to keep them cooler etc... for home built pannels. The hotter they get the less power they make and also could be damaged by the heat. So the first problem it would seem is how to mount them as a roof and prevent leaking and such, they're not designed for that to begin with. Then you have to somehow cool them. Get that heat out and away. As a roof you will have all that heat in the attic as mentioned. As a normal mount they are standing in the air with air flow all around them, as a roof they would not be.

Heating your attic in the summer of course is not a good thing either, perhaps durring the winter though that heat could be piped down to heat the living area of the house and actually be usefull with some fans moving it.

One of the things I thought about would be maybe using a cheap metal roof under the pannels. Run water lines up through the ridges of the metal roofing and then mount the pannels as a roof over the metal. This way the metal roof is protected from the sun and most rain/snow etc.. and should last longer and be cooler durring the summer being shaded. The water lines absorb the heat from the pannels and metal roof for solar hot water heating and the entire metal roof acts as a heatsink to cool the pannels this way.

Still got a real roof though. Also other problems like the angles and such. Pannels would not be adustable to the sun durring season changes so less effecient over all. Either would need to be a steep angle or leaves may build up and reduce or stop power.

They need to produce the solar cells as a type of shingle that is easy to install and self cooling, eliminate the cost of shingles and rolled roofing, that would help alot.

Psycogeek · « **Reply #5 on:** March 13, 2005, 10:53:35 PM »

ahh now that is more along the lines of my thinking process

they do have solar shingles, but they have a higher cost per watt, and they are not a "roof" itself, although its a very nice design. but that is untested, no one knows its ability for sure over time. usually the soft flexable stuff is based on plastics, and we know how well tose work in the sun

they have a metal roof design, but it basically is a metal roof, with pannels attached.

if i am going to fully integrate solar cells into the house, and mabey build them myself, and mabey (magically) do it better stronger faster , and definatly CHEAPER.

then it just seems that some sort of Enclosed finished pannels AS the roof itself would work.

take your thoughts on air/water transfer through them.

what if each roof unit, went from Eaves to top, had replaceable acrylic tops , could survive a hurricane (just the wind part) , and a hail storm .

putting an air or water transfer system in them would be much easier, with present cheaply available stuff, to use the leftover heat, and to simeltaneously cool.

air transfer could be FILTERED, so dust and stuff wasnt as big a problem, once the "system" is ducted (enclosed). water transfer would be more efficient, and usable for the ever used hot water pre-heater.

so now attach the top :-( and seal it. and have a walkway around Every one of them. and have that walkway be just as sealed, and safe, and accesable.

electrondady1 · « **Reply #6 on:** March 13, 2005, 11:27:39 PM »

it would be wise to have some sort of water tight membrane under the modular panels in case of failure/repair/removal.

Psycogeek · « **Reply #7 on:** March 13, 2005, 11:29:32 PM »

Take one of these short term pieces of cheap vinal

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=42239&item=4363923325

how would you run it down inside the pannel, then put the cells on top.

but more importatally, how would you remove the cells off the top, replace the vinal after it got wasted in the sun, and replace it and the cells.

its not like the cells can be on fold up pannels :-)

somone mentioned attaching the solar cells themselves to the TOP of the pannel, not the bottom. the problem with that is any thing hitting the top, then impacts the cell. i still thought there was some brilliance in the idea. we always think put cells in, attach top.

if a tempered glass at 500+ lbs was used and it could be folded back to access the bottom of the cells, and the water jacket, all you would need is 10 People to help you do it :-)

running copper pipe lines vertically , attached to aluminum (water heat collection) back plate, would be far more practical. but i cant imagine the costs of that.

so now i have 6 layers,

the wood back plate,

the copper pipes

the aluminum collection plate

the conductive insolation

the top pannel

$$$$

hmm what would stop the conduction of the cells power, but allow the conduction of heat. mabey simple silicoln sealer.

silicoln is not GOOD for 20 years, it ages exposed in less than 10, but it would not be exposed, to the sun or the air, for the majority of it.

besides the extensive horrendous costs of all that, what els would be wrong :-)

Psycogeek · « **Reply #8 on:** March 13, 2005, 11:37:29 PM »

you mean like roof paper.

see that is some of the things i cant figure.

you have a bunch of open joists with big holes in between, trying to put a modular roof pannel on, and the goverment comes along and say "its not to code, you must have tar paper in there"

if you have acrylic, or glass roof, how do you put tar paper in there :-)

Psycogeek · « **Reply #9 on:** March 13, 2005, 11:39:45 PM »

oops that would be 7 layers, the tar paper on top of the wood.

that would slightly insulate the copper pipes.

nothing to lose · « **Reply #10 on:** March 14, 2005, 01:05:54 AM »

OK, you can't have anything flexing because the cells break so easily. But how about this.

Someone here building pannels mentioned using mineral oil inside the pannels to prevent condensation and reduce heat. I don't know how well that works with the cells myself. But lets say you make your pannels yourself, take sheet metal for a backing and fasten the cells to that. Add support side ways so they can't sag, the trusses/rafters are the supports vertically. Make the pannels to run from the eaves to the top of the roof as one long peice. leave the walkway between pannels. So you have 16" centers on the trusses, you have 32" of solar panel, 16" walkway all the way from top to bottom of the roof vertically. Now cover the pannels with glass or plexy of your choice. Fill with mineral oil. At the bottem of the pannel and the top also are connections for pipe which runs to a large water tank and heat exchanger. You pump cool oil into the bottom of the pannel pushing the hot oil out the top, cool the oil at the water tank, pump back to pannels. Nice solar water heater, and pannels stay really cool if you keep that oil cool enough and pump fast enough. Cooler pannels mean more power too so that might offset some of what your using to run the pump, with enough pannels you might break even on gain and losses?? You could wire in a tempsensor so the pump only runs when the oil is above a certian temp in the pannels. That means early morning when everything is still cool but the suns out the pump won't turn on till things start getting hot. You could also wire in a light sensor so that the pump shuts off when the sun goes down and the cells stop producing power. Then even if still hot enough to trigger the tempsensor the pump shuts off, they won't be getting any hotter if the sun goes away so they can cool on their own.

As one long pannel from top to bottom of the roof no leaks. You could have the outer 8" of each pannel as part of the walkway to make up that full 16" and then you could have a fold over seam you can hammer down tight, again no leaks. You will of course have to fasten to the trusses somehow so it don't blow away in a high wind. Make mounting brackets under the sheel metal on those cross supports and fasten to the trusses on the attic side not the outside.

The two keys are don't let them flex or they will break, and keep them cool. Now how you can actually do the above and not flex the cells will certainly be the main problem! Also how to handle a 30'long or larger pannel that runs from top to bottom of the roof may not be too easy either. You could make the pannels smaller but then your back to connecting them without leakage and you'd have more connections for the cooling lines for the mineral oil to be pumped through.

Now I don't know if mineral oil is going to work or not, I just know I read of someone here using it, or maybe they were thinking about using it and hadn't yet? I don't remember who it was though.

Psycogeek · « **Reply #11 on:** March 14, 2005, 02:10:44 AM »

assume a maximum of 20' roof can i get plywood in more than 8x4 sheets?

you made me think of somthing, with some plastic junk solar WATER thing in the pannels, the pressure of the water at the low points would be very high, not gonna work vertically on the normal pitched roof. making real pipes more nessisary.

that would be just like the mineral oil, the pressure at the bottom of the pannel would be enough to spew oil back to the roof top if it leaked :-)

the pressure at the bottom of the pannel might be beyond a silicoln simple seal, mabey a windshiled sealer would do it, but on leak and it would be heck to try and reseal or repair. they still cant seal a windshield when they replace the glass :-)

if you had to run the liquid into the ground, then that is more pressures again.

then sealing it back up after cracking it open, with oil, would mean haveing to ammonia or detergent clean the whole thing first.

Side notes: glass is actually a liquid, and over 100Years it flows down (supposedly) they show some 100 year old windows, and they are 2x as thick at the bottom and thin at the top.

Temp guages, and water or oil cycling , seem like an unnessisary element to me. the moronically simplistic method would be Sun hits, liquid moves.

as soon as you have any form of sun, (in Ca) you have more heat than the water out of the ground. but i dont know how water suplimental heaters work.

i was thinking EASY, use the municipal pressure , but without consumption there would be no flow.

TomW · « **Reply #12 on:** March 14, 2005, 06:01:16 AM »

Terry;

Please, please. Push that "Caps Lock" key on the left side of your keyboard. No need to shout.

Cheers.

TomW

finnsawyer · « **Reply #13 on:** March 14, 2005, 08:57:05 AM »

Go back to Feb 7 th. and bring up a posting on solar panels. You can find a link to the company that makes solar shingles there.

pyrocasto · « **Reply #14 on:** March 14, 2005, 12:24:02 PM »

I'm trying something like that now that my tracker's up. I'm using oil to cool the cells, and for heating as well. Since the cells cant get that hot using the oil, I'm also going to put a few times the light on them to see what happens. Either I'll get more output, and have more heating for my house, or I will ruin the cells. Time will tell after I finish setting it all up.

I also dont see why people dont run air through thier cells to help heat thier homes in the winter as well.

nothing to lose · « **Reply #15 on:** March 14, 2005, 01:37:01 PM »

"I also dont see why people dont run air through thier cells to help heat thier homes in the winter as well."

Condensation of moisture most likely, I hear that's not a good thing and could ruin the cells. Otherwise it might not be that bad an idea, but how to dry the air and keep it dry? It will pick up moisture if circulated in the house.

Also air is not as good at moving/removing heat as other things like water or oil, that's why we have coolant in the car engines instead of just blowing air through it

nothing to lose · « **Reply #16 on:** March 14, 2005, 01:48:23 PM »

Actually the pressure could be a good thing, if worried about that just pump the oil into the top and let it run downhill freely and there will be no pressure at the bottom.

Hmm, build yourself an oilfall gennie to help gain back some of that power that was used to pump the oil up there to begin with.

Just a water fall with oil insead of water

As far as a leak then, no big deal. Pump just enough oil to cover the cells and keep them cooled and wetted and don't bother pumping the pannel full.

It'd still be alot of oil on the total roof, but just a thin layer covering the cells.

We're not talking a gallon per cell, just a thin covering over them.

Maybe you could use lard instead of mineral oil, it would solidify when cooled and stick to the cells over night ready for the next days heat. This would prevent moisture from getting to the cells durring the cooler nights and cool durring the hot sun both. Not sure if lard or animal fats are good for cells or not, be sure to use salt free lard if trying this

Psycogeek · « **Reply #17 on:** March 14, 2005, 03:00:07 PM »

eww lard , it would get rancid over long times

a oil waterfall, wouldnt REALLY have to hit every MM of the cells, as they conduct heat through themselves. so just a rain with a pipe with a series of holes in it.

but then what roof is perfectally straight.

some of the walls in these developer homes, are off by as much as 2"

roof sag exists too, even if we will not see it in the realestate sales.

jimjjnn · « **Reply #18 on:** March 14, 2005, 03:08:45 PM »

Solar shingles are a pain to install cause of all the wiring that has to be done through the roof unless they have a new way to do it. The metal roof type looks a lot better as it has built in channels to run the wires to the peak and connect to a buss at that point

Psycogeek · « **Reply #19 on:** March 14, 2005, 04:42:12 PM »

i was seeing that. i thought they might be on Long rolls,

they have normal shingles that are on long rolls now.

to put these solar shingles on, you would have to fill the roof with holes (see homeowner running and screaming:-)

but at least they had some major overlapping going on. and at least they are as wide as a real shingle, instead of even smaller pieces.

I think Age still would worry me most, the things were messing with now are glass, and metal. polywhatevers (plastic to me) havent cut it in time in the sun that i have seen yet.

pyrocasto · « **Reply #20 on:** March 14, 2005, 05:34:12 PM »

Of course it wont, but it eliminates alot of the money and hassle.

To keep it dry, I guess a dehumidifier is the only thing I can think of.

TERRYWGIPE · « **Reply #21 on:** March 15, 2005, 09:48:28 AM »

First off sorry everyone for "shouting" i'm a novice as far as computer chat room manors, wont happin again.

As far as any heat factor with a solar roofing system, it shouldn't be any different than any other roofing material, such as say asphalt shingels. most are dark in color many are even black. so the same princibles of ventilation should apply.

The only aspects that I would think should be a factor is material useful life and price per square. Yoou can get a good convential roof for abuot $35 per square.

Phil Timmons · « **Reply #22 on:** March 15, 2005, 11:47:43 AM »

Well heading back towards the starting concept -- which I read to be why put a roof over the roof? I am thinking that something analogous to standing seam metal roofs would long thin trough concentrators/collectors. Yeah, I know that is not cells, but considering $$$ and/or PITA, with cells, I am starting to think that is not such a bad thing.

It seems that most rooftop (over-layer) hot water units make only hot water -- no real application towards cranking the electric meter backwards -- only reducing how much it is going forward.

It seems that stepping up the heat level to serious hot (above boiling) with a hot oil for a heat exchanger, could actually give some positive energy production. Of course you still get the hot water and building heat as surplus waste product -- such a problem.

But I think the real clever part of the starting topic was that it REPLACE the actual roof. While that lowers the original building cost, in many states it also makes the portion of the building -- in this case the entire roof -- exempt from property taxes.

There are some simple versions of this for space heating only, as well. Sort of a double layer metal roof that gets warm, and gets air drafted through it and into the building.

Even with solar cells, you could build them into a metal frame that "lapped" the top sections over the bottom and sat directly on roof trusses, or between the trusses. That would eliminate the roof decking, radiant barrier (if used) waterproofing layer, and shingles in a conventional house.

Psycogeek · « **Reply #23 on:** March 15, 2005, 08:27:35 PM »

i despise black asfault shingles in california.

put a solar heat collector on your shading unit ,

that never made any sence to me

When we re-roofed one location, i almost wanted WHITE

but because all of the houses used black, we used a nice

light brown to fit in.

gotta keep up with the joneses

even if they get stuck with idiocy too :-)

Light Gray roofs are becomming more popular

so that is a good thing

i wouldnt want to clean white anyways.

a pound of prevention is better than 500$ of cure :-)

but then with the solar cells, its back to black.

Kwazai · « **Reply #24 on:** March 16, 2005, 08:30:48 AM »

there are some pool solar heaters that are essentially built like flexible rubber roofing- maybe that is an option- membrane roof that collects heat- would be even better if you could get it to pump itself....

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Author Topic: Solar ROOF preacticality? (Read 3360 times)