roof power generators

What other kind is there? And don't go calling that corrugated crap for chi cken sheds metal roofing. The breakthrough in metal roofing, that gets thos e 50 year warranties, is the space age paint technology that not only retai ns the original color forever but also protects the metal.If you get the re ally lightweight stuff, the material cost is about the same as asphalt, the installation labor is what makes the install a bit more expensive. The bes t scenario is to have a roof designed with metal roofing in mind. The McMan sion idiots with pseudo-complex roofing that serves no other purpose other than the brain dead "wow factor" with bunches of fake dormers, nested gable s and other forms of unnecessary nonsense are going to pay top dollar for a ny roofing technology.

The latter. It looks like a regular install, except that the brackets clamp to the standing seams rather than penetrate the roof surface.

In a buddy's house with a plain (no solar) metal roof, not at all. The metal roofing's resonances are heavily damped by the underlayments it rests on.

I'd think the clamped-to-standing-seam construction would do pretty well acoustically as experienced from inside the building, since the sound has to cross the felting damping / mismatch barrier to make it to the roof deck.

I wonder if the panels themselves, with a regular roof, might make a bit of patter. Those look a bit like 'sounding boards' rigidly-coupled to the roof decking via their brackets.

Cheers, James Arthur

Exposed fastener vs. not exposed.

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I have several neighbors with metal roofs, plus helped repair a leaky metal roof for a friend. No two were the same.

On the solar neighbor's roof, the roofing panels somehow snap onto brackets that are attached to the roof decking. I didn't see the installation, but the result is that no fasteners show or penetrate the sheathing.

All the others had some variation of nailing the sheathing to the decking either along a ridge formed in the metal sheathing, or even in the valleys (!), 'sealed' by a flaky-looking plastic seal under a big-headed nail.

Needless to say, some of those are less equal than others.

the space age paint technology that not only retains the original color fo rever but also protects the metal.

Yep. The choices include aluminum (most expensive, IIRC) or steel, galvanize or no, and various platings & coatings.

The no-penetrations aspect is important too. One neighbor's roof has hundreds of exposed fastener leak-points, the other's has zero.

ame as asphalt, the installation labor is what makes the install a bit more expensive. The best scenario is to have a roof designed with metal roofing in mind. The McMansion idiots with pseudo-complex roofing that serves no o ther purpose other than the brain dead "wow factor" with bunches of fake do rmers, nested gables and other forms of unnecessary nonsense are going to p ay top dollar for any roofing technology.

The metal roof installation is a breeze--placing a big panels is a lot more fun than nailing a pile of of heavy shingles. Here the cost difference is mostly materials.

Cheers, James Arthur

Thanks. I've been trying to untangle the relative merits of the two technologies for a bid. The common assumption is that thin film is less efficient that polycrystalline. Yet, the latest numbers look like they're much the same. Of course, these are mostly from research reports, which tend to include cute tricks like cooling the panels.

Thanks again. We don't have many metal roofs in the area. One of the local roofers gave me some addresses to look at, but I haven't had the time. Meanwhile, I'm looking at double sided solar panels such as: which incidentally are incredibly thin (about 1/4) and reek of hype: Add a metal roof into the mix, and I'm lost.

On a conventional roof, adding solar panel doesn't seem to increase the rain noise at all. I've done before-after tests on those. Solar electric panels are a sandwich of plastic, glass, metal, silicon, more plastic, etc, which does a fairly good job of deadening any sound. Unlike a roof, mechanical resonances are heavily damped and at fairly high frequencies. However, I don't know much about metal roofs and haven't witnessed their acoustic behavior while raining. Good to know that such roofs are insulated and sound dampened.

Topic drift: I got some email from readers asking about solar power system. Mainly, they involved combining solar, wind, hydro, generator, battery backup, and utility power sources. The latest current issue of Home Power magazine has an interesting article featuring a home system that utilizes most of these. Also included is a LiFePO4 battery pile for backup. Interesting reading: Click on "Inside this Article" links to the right of the photos to see the drawings and system diagram. Spoiler: It cost $127,000 before incentives.

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
Santa Cruz CA 95060 http://802.11junk.com 
Skype: JeffLiebermann     AE6KS    831-336-2558

A local firm has a tracking parabolic collector and harvests the surplus heat from the collector to heat water:

But, fairly heavy (concentrated) to install on the flimsy roofs, here (no snow load so roofs aren't designed to handle any substantial weight)

Would be an eyesore to install at ground level...

Lots of problems with such systems. Quick summary:

1. The system will only produce as much electricity as sunlight it can collect. Ideally, it's DNI (direct normal irradiance) or 1KW/m^2. A rooftop full of solar panels will produce considerably more power than what looks like a 1m^2 dish, no matter if it's a panel or concentrated.
2. They track the sun and therefore have moving parts.
3. The reflectors cast shadows on each other.
4. You need space between the collectors for maintenance, which wastes roof area.
5. Solar cells drop in output when hot. That's why it needs cooling.
6. Dumping excess heat into hot water storage is a good idea for industrial processes that actually use the hot water. However, on weekends, when the plant is turned off, the hot water is not used by the plant. So, it has to be stored somewhere, or dumped on the ground. Basically, the hot water storage capacity has to be equal to one days consumption of coolant, or some means of storing or dissipating the heat needs to be found.
7. etc...

Anyway, I'm stuck with new construction, a South-West facing roof, a strange client, ever changing specifications, and an unstable budget. I'm working with the architect and seem to have plenty of time to work out the details. The basic problem is that if I propose a 50 year roof with stick on thin film solar strips, what will be needed to keep it going for the 50 year life? I'm looking at inverter obsolescence, long term corrosion, weathering, environmental regulation changes, politics, etc. Life was much simpler when everything was expected to fall apart after about 25 years. Much of this is new to me.

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
Santa Cruz CA 95060 http://802.11junk.com 
Skype: JeffLiebermann     AE6KS    831-336-2558

Um, you *can* use more than one dish! Note the link I presented was an 8 dish array, ~6KW + 8KW of hot water.

Yes. Though there have been some mirror shapes developed that minimize this (at the cost of efficiency)

No more than flat panel collectors mounted on a FLAT roof!

You can ACCESS the roof under the collectors instead of having to pay to remove and reinstall them each time the roof needs maintenance!

That's why it uses the heat pulled off the cells -- instead of letting the flat panels absorb (and retain) the heat.

There's no free lunch. Flat panels store the heat in themselves (counting on radiant cooling to remove whatever it can)

By far (IMO) the bigger concern is the potential for wind and hail damage. We experience frequent microbursts which topple trees of all sizes (toppling a small tree is often harder than a large one!).

I suspect some of the recent PV panel installations will see some unfortunate consequences as the winds pounce from the north -- and that is the side of the panel(s) that would be elevated (i.e., as a wind sail).

It will be interesting to see if these events just tear the panels from their mounts, damage the panels *or* damage the house structures, themselves.

[A nearby flat-roofed apartment complex has a large PV panel sail, as well -- but, they are further out of this local microclimate so possibly don't experience the same storm events]

Here, the local utility has been proposing tariffs aimed at discouraging solar. First proposal was a $50/month surcharge to have access to the grid (for cloudy days). I think that has been scaled back to $20. But, that's an extra $20 of power you have to come up with before you're "saving money".

Who's to say it won't be $30 after that? The "regulators" look at the company's financial statement: infrastructure cost doesn't go *down* just because you have solar customers (I think about 10000, here, now); it just doesn't INCREASE as much as it would, otherwise!

And, if you aren't billing them for power (cuz they are cogenerating), then the money has to come from SOMEWHERE...

Doesn't that break the surface paint where the clamp distorts the metal?

How does that work? AFAIK, the seams are supposed to sit on the rafters and fastened through the "standing" part so water is channeled away from the screws.

Good question. His roof is 'Galvalume,' a zinc-aluminum coated, painted sheet. Clamps breaking the sheathings' coating might create a corrosion cell, depending on the materials. I guess they could use rubber pads in the clamp jaws to prevent that, but I do not know what they actually did.

I'm not sure how his is fastened. He explained it but I never could understand. But it's resting on a standard felted plywood roof deck--you can't just hang 29 gauge sheet metal between rafters.

Cheers, James Arthur