Aluminum frame assembly for a custom greenhouse

This feels like a dumb question, but my google skills are failing bigtime.
My parents are building a very small solar collector on the front of their house. To reduce the view obstruction, they want to build an aluminum frame.
I have found various aluminum channels for greenhouses, but I cannot figure out how they attach. Are there corner pieces? I can find lots of kits, but no place to find the parts separately with a way to attach them.
Anyone have resource for parts purchase or instructions on assembly of aluminum frame greenhouses with double walled polycarbonate panels? Thanks!!!

some are cut in a particular way and then screwed together and others have special fittings.
Maybe drop some details of what you want to use, and I may be able to help you?

Thanks!
Correction-not twinwall: polycarbonate sheets, probably 8 mm.
Basically, we want to use polycarbonate sheets and aluminum framing to build a 10 ft by 4 ft, 16 ft tall against their south wall. Aside from that, we are flexible as to materials. Do you know of a good system for this?

The channels for installing the 8mm twin-wall polycarbonate panels are just that, a means of holding the panels. They aren't structural, they are meant to fasten to a framework of wood, steel, aluminum. If you actually mean corrugated/wavy single sheets, those don't use the channels at all, but just overlap and screw directly onto a frame with special screws

There used to be an aluminum framing extrusion for greenhouse end walls, which used a special tool to cut and bend the tubes to create tabs to fasten them together with self-tapping screws. I cant seem to find it, I think the distributor no longer carries it, if it even still exists. One would then attach the other moldings to fasten the polycarbonate panels on top of this frame.

Square galvanized steel tube for greenhouse end walls uses L-brackets to join sections.

There is a system of T-slotted aluminum framing (originally 80/20 brand, from many manufacturers now). It is basically Erector Set (Meccano) for adult engineers, lots of options for brackets, hardware, profile shapes and sizes. It is quite a bit more expensive than wood, but it can be ordered cut to your dimensions (no waste or cutting tools required, needs only wrenches to assemble)

There is another steel framing system called "strut-channel" (brand name Uni-Strut) which has some similarities to 80/20, but generally used in construction for supporting pipes, conduits, HVAC equipment and ductwork. It is a bit more crude? but with a decent variety of connector options.

You might find some of these in 20-24' lengths, and the steel options might be available locally from a plumbing/electrical distributor, or from a steel supplier. The home-improvement box stores have a limited selection of the connectors for Uni-Strut, and just 10' lengths. (although check if there's a ship to store option for 20'?). McMaster-Carr sells all the connectors, and although heavy, they fit in a box and ship...

Wood is likely going to be the least expensive option of all, and the "2" of 2x4, 2x6... is just as wide as the aluminum channels, and the "4" or "6" is only 2 or 3 times as deep as a square metal framing member would be. Paint it to match the house? paint it green to blend into the view? Go get a 2x4 and hold it up there, see what it actually looks like.

You may need bracing to the house in the 16' height. It is possible that this could be loud in the wind, a 10'x16' diaphragm, like a drum head.

Wow, thank you so much! This is super helpful.
It will definitely be braced to the house - my father has designed and built the whole house and he always errs on the side of caution. Building out of wood he would know how to do it, but we want something thinner to minimize the disruption of the view.
I will mention the drum possibility…