Installing Solar Panels Directly on Rafters: Advantages, Heat Dissipation, and Sealing Edges

I am thinking of installing the panels directly on the rafters.
As in the picture:



Grounds:
- easier assembly
- more durable structure - a frame under the panels and cables not exposed to snow, wind and rain
- easier installation - available cables from the bottom of the panels
- lower price - installation on steel profiles mounted to the rafters, without the need to use roof tiles and a roof membrane


Of course, I'm not the first to think about it - whole systems exist. However, I have not encountered any accessories for such assembly of standard panels, maybe I am looking for a wrong one.


Questions:
1. What is the issue of heat dissipation in such an assembly?
2. Are there seals between the edges around regular panels? Or side profiles to connect panels together like tiles like below?



3. Possibly, has anyone applied such a solution?

Thanks in advance for your comments

These are the Centrosolar integration modules - we had these.

In general, the mounting accessories are much more expensive, you need to buy special gutters at the top, bottom, sides, some plastic supports, too.

The modules themselves are also not the cheapest.

Another disadvantages are the possibility of leakage and certainly heating - the module has much worse ventilation and will heat up more = power loss.

The only thing that some people like aesthetically much more.

How much higher temperature can there be in such a system? And by how much lower efficiency per year?

I thought about connecting ordinary panels with polycarbonate profiles. They are sealed and intended for a similar purpose.

Compare here free standing with building integrated

http://re.jrc.ec.europa.eu/pvgis/apps4/pvest.php?

from what I can see it is 5% less energy per year

Installation is simple with the thin-film without a frame. All you need is a rail and brackets inserted under the tiles and screwed to the rafters.

Well, on the other hand - polycarbonate is flexible, it will adapt to the movements of the roof structure due to wind or drying of the wood. Panel not necessarily and may break.


I'm new and a bit 'green' on this topic. What is the cheapest frame? Doing your own work?
Only it probably has to be made of aluminum, because it is expected to last 20 years.

A few months ago, in one of the threads, someone described a structure to which he "rigidly" glued amorphous silicon panels, hoping that the silicone layer would compensate for the work of the structure.
And after a few days, the panels began to crack.
Materials are not combined, otherwise they work with temperature changes, and flexible and inelastic materials (panels).
For example, let me give you a neighbor who built a house with a wooden ceiling. The ceiling in the rooms was made of drywall. But his "brilliant" team of bunglers made ceilings strangely fast during his several days' absence. After a short time, it turned out that the cardboard plates were screwed directly to the wooden structure. Very quickly the plates started to crack ...

Where can I get more information about the frames (profiles, holders, how to mount the rafter holders tightly, etc.)?

maciejzi wrote:

I thought about connecting ordinary panels with polycarbonate profiles. They are sealed and intended for a similar purpose.

I was thinking about exactly this solution. the use of system solutions for polycarbonate roofs. they have gaskets at the top and bottom, cover strips ensure tightness.
You do not have to worry about working in changing temperatures - polycarbonate has about 8 times the thermal expansion coefficient than glass. if polycarbonate works, the panel will handle it. vertical movements should compensate for the seals.

there is only 1 problem - horizontal connections (when looking at the slope). how to get the tightness here. the idea came to my mind to glue the angle to the bottom edge (I put on the frame panels), so as to make an "extension" of the panel (one side of the angle against the frame, the other side flush with the upper surface) which will fit on the lower panel and in the event of thermal operation will allow movement.
has anyone seen something similar? or met with a similar solution

In my case, I do not assume the need for 100% water tightness because I will have full boarding and a membrane underneath. it is about eliminating the tile and making it airtight

Airtightness is one thing, but polycarbonate is flexible and glass is not.
And in the long run, however, the roof structure moves under the influence of wind, snow deflection, drying of the wood. Polycarbonate will not break, but glass is fragile. You thought about it?

I thought. when you install the panels in standard holders, they work exactly like the roof, because there are probably no elements that select displacements resulting from the work of the roof? because most of the systems are probably rigid assembly
some users use window seals when fixing to steel frames and nobody seems to be hurt. system gaskets for polycarbonate seem to provide more movement.

maybe I am wrong, so please correct it

Is it worth saving?
According to normal prices (eg ASAT), using the original aluminum profiles and aluminum / stainless steel fixings, the material for mounting on rafters or flat roof and aluminum triangles costs PLN 740 / 1kW or PLN 88 / m2. This applies to thin films without an aluminum frame. It is said that the frame is cheaper to install, but I do not know. For me, it was cheaper due to direct access to the importer.
I could combine it with welding a steel structure, but I won't save much, much more work and there is a maintenance cost.
So for a 3kW installation we have a cost of PLN 2220, and for a 10kW installation, PLN 7400. At a price of PLN 3,500 / kW, it is 21%.

Jan_Werbinski wrote:

Is it worth saving?
According to normal prices (eg ASAT), using the original aluminum profiles and aluminum / stainless steel fixings, the material for mounting on rafters or flat roof and aluminum triangles costs PLN 740 / 1kW or PLN 88 / m2. This applies to thin films without an aluminum frame. It is said that the frame is cheaper to install, but I do not know. For me, it was cheaper due to direct access to the importer.
I could combine it with welding a steel structure, but I won't save much, much more work and there is a maintenance cost.
So for a 3kW installation we have a cost of PLN 2220, and for a 10kW installation, PLN 7400. At a price of PLN 3,500 / kW, it is 21%.

do I understand correctly that you have a system with rafters mounting? I did not find a system for such an assembly in the ASAT offer

it is not about saving, but about a system that will ensure a tight surface. I have not found such a solution (at a reasonable price, because they are supposed to be BIPV, but this is a price space for now, and there is also a visual aspect - you do not have to choose the type of panel)

I have two under construction: for the rafters http://www.sklep.asat.pl/pl/p/Uch useful-standard-do-dachowek-ceramicznych-i-betonowych-%2C-Art.007-/128 which is mounted on a flat roof and alu triangles.
I am not going to make an airtight roof, if only because it is inconsistent with the panel manufacturer's instructions (cooling, dilatation, expansion, etc.).
The visual aspect is great: completely black SL1-90 panels with a black frame.

Jan_Werbinski wrote:

So for a 3kW installation we have a cost of PLN 2220, and for a 10kW installation, PLN 7400. At a price of PLN 3,500 / kW, it is 21%.

I do not deny that these are good solutions, but personally, if I had to spend so many thousands on the mount alone, I would rather try to figure it out a bit.
Do something and even have it galvanized - probably half of this amount would work out.

These polycarbonate profiles can be used on 4 sides by joining the panels together.

The connection with the tiles can probably be made through a roofing apron or a metal sheet (on one side fixed in the profile and on the other side under the tiles).

As for cracking - in rail mounting, these rafter mounts can bend a little as the roof moves. As for mounting directly on the rafters, there is no such range of motion, because the panel is rigidly fixed on the beam. I don't know what it looks like from this point of view.

Putas wrote above that the panels mounted in this way broke someone else.

Another thing is ventilation. At high temperatures, not only is the efficiency lower, but also the efficiency drops faster and therefore the service life is shorter.

Despite all these issues, there are direct assembly (integration) systems and they even look good.

http://tnij.org/y57ryxf

This is what I wanted to do at home when I was building a house - to do under ordinary tiles.
But then I had too little knowledge and did not want to fight too much with the roofers.


Coming back to the assembly of panels, is it not easier and more reliable to make the cheapest roof covering with steel tiles and simply install the panels on standard fasteners.
The roof is lighter and cheaper, and the metal tiles will hardly be visible.

For me, one of the issues is safety during assembly. Ie. instead of tiles, you can install them from the inside, from the attic, and you have to climb onto the roof on a separate rack. As my roof is 6 - 9 m above the ground, self-assembly from the outside is a risk.

putas wrote:

Jan_Werbinski wrote:

So for a 3kW installation we have a cost of PLN 2220, and for a 10kW installation, PLN 7400. At a price of PLN 3,500 / kW, it is 21%.

I do not deny that these are good solutions, but personally, if I had to spend so many thousands on the mounting itself, I would rather try to figure it out a bit.
Do something and even have it galvanized - probably half of this amount would work out.

The galvanized coating will not last that many years. There is a problem how to galvanize a large structure? Or maybe its elements and then corrode on the joints? What about electrolytic corrosion? If original panel fixings and rails are used, they are aluminum with stainless steel screws. If you connect a large zinc-coated steel piece, what will corrode first?

the galvanization will last long enough, but you have to separate elements and connect them with screws, the coating must be airtight

maciejzi wrote:

As for cracking - in rail mounting, these rafter mounts can bend a little as the roof moves. As for mounting directly on the rafters, there is no such range of motion, because the panel is rigidly fixed on the beam. I don't know what it looks like from this point of view.

Putas wrote above that the panels mounted in this way broke someone else.

Another thing is ventilation. At high temperatures, not only is the efficiency lower, but also the efficiency drops faster and therefore the service life is shorter.

but putas probably wrote about sticking panels where silicone holds permanently and blocks displacements from temperature, and here we are talking about gaskets that allow movement, this is something else.
I assumed that the space under the panels (if it was possible to create a closed one) would be ventilated, if necessary with additional fans.

I am joining this topic because I have a lot of plastering on the walls of the building. I counted that the plaster itself is the same cost as the panels. I really like "glass" buildings, but is there a ready-made fastening system for something like that?

The second thing is what is the actual efficiency of amorphous panels, i.e. if I install these panels on all walls, it is known that not only on the east, west, south, but also on the north wall.

What power from the 100W panel can I expect on the north side?

And here if someone wants to watch my play:
https://www.youtube.com/channel/UCuk3XURmHVTPf5rTHzfHd4Q

When installing on walls, especially on northern walls, there will be a big problem with uneven panels. It is known that each panel (even amorphous) needs sun to work well. If you fasten a few panels, and some of them will be in the shade because they are covered by the roof, one big sneezes will come out.
You'd have to think of a lot of microinverters, but that's the cost. You will definitely need several inverters anyway, preferably with several MPPT paths.

Added after 48 [minutes]:

wwawer wrote:

And here if someone wants to watch my play:
https://www.youtube.com/channel/UCuk3XURmHVTPf5rTHzfHd4Q

I watch part 2 and I think one is serious, but it comes to my mind.
panels are mounted practically on the roof surface. The roof has a slight slope and probably towards the front of the panels. when snow falls, some panels will be covered and, in addition, the melting snow will not be able to slide down - it will stop on the panels. On a sloping roof it is called a snow fence .


Sorry, I wrote too quickly.
And it was enough to look a few minutes later in the film ...

putas wrote:

When installing on walls, especially on the northern walls, there will be a big problem with uneven work of the panels. It is known that each panel (even amorphous) needs sun to work well. If you fasten a few panels, and some of them are in the shade because they are covered by the roof, one big sneezes will come out.
You'd have to think of a lot of microinverters, but that's the cost. You will definitely need several inverters anyway, preferably with several MPPT paths.

I do not know about amorphous ones at all, but everyone says that they can act shaded. I suspect that it is about the fact that the glass is conductive and does not have amorphous circuits as in polycrystalline or mono, so shading half of the panel probably causes a decrease in efficiency by exactly 50% ...

But that's why I wanted to find out someone who has them.

I only read that amorphous ones are usually 90-110V and thus there must be only 3 pcs in a row for an average inverter. I thought to connect these in parallel in sets of 3 times 7 (2.1kW) to one MPPT.

Summarizing and flattening the question: Does a 100W amorphous panel produce 100W of power does it have to be in full sun?

wwawer wrote:

Summarizing and flattening the question: Does a 100W amorphous panel produce 100W of power does it have to be in full sun?

YES.
The rated power of each panel is determined at a light intensity of 1000W / m? - which is essentially full sun and the optimal angle of incidence of rays.
as the panel gets less solar energy it produces less electricity.

Each panel is made up of individual cells.
The glass is not conductive in any of them.
In poly and mono cells are square or close to square. Covering such a link causes that the given string essentially ceases to produce.
In amorphous (thin-film) individual cells, they are shaped like long and narrow rectangles, arranged along the long side. The current-producing layer is thinly applied to the foil and secured on both sides with glass. If you cover a part of the panel along its long side, you will cover several whole cells - the panel will stop working. But if you cover a part of the panel along the shorter side, you will cover the links only in some part, and the unobstructed rest will work, but proportionally less.
And when it comes to working in poor lighting conditions, the results of various studies show that thin films achieve better results by about 5% compared to poly and mono.

But in general, any panel must get good sun to produce well. And nothing will change that, because it is the law of conservation of energy. To produce electricity, you always need to supply other energy - in this case solar.

I also used to think about the facade of panels, the topic fell, because I couldn't damn well integrate the windows with the panels to make it look somehow.

I only thought about the southern facade, but what a problem to do, for example, with 3 walls and the fourth one with another expedition. and if the whole "glass house" is to be, you can probably give ordinary tinted glass for the northern wall

going back to the main thread
I have already come to the conclusion that I will make panels on the roof on paper or other membrane, panels as close to each other as possible but with spaces and water flowing under the panels on the roof. not to install against the manufacturer's recommendations. but once again browsing the thread and in one of the links I found the shelters, so somehow it can be done to keep it tight . now I know how to make a terrace roof.
Moreover, all these integrated systems work, you can find a lot of implementation. do you think that there really is such a large loss of power and people go into it to get tightness?

I glued the layered ones thinly to the frame, one of them broke because I gave them too thin a layer of silicone, but the other 5 are over a year old. To glue the panels, place wooden spacers and then glue them and they will lie like on gaskets.