Question on covering solar collectors?

[peakbagger]

When I first installed my SHW panels long ago I mounted then conventionally lined up with a somewhat shallow roof pitch, the result was not enough heat in the spring and fall and way too much in the summer. I ended up tipping them up to a winter orientation. It extended my SHW season by a couple of months and reduced overheating in the summer. The only trade off is aesthetics. One plus is when snow builds up on the roof the snow slides down them and if its sunny day they will start putting some amount of limited warm water from the part that is not covered with snow.

There are poly tarps with silver color to them that seem to hold up far better than the blue ones. They arent that hard to customize, just cut them large and then fold the edges over. 3M sells special duct tape for tarps. Grommets kits are cheap and a couple of grommets on the corners where the tarp wraps behind the panels makes running bungee cords easy.

[sroof]

I've used a poly tarp to cover my panels when I go on summer vacation, but they wear out fast from the UV. I used a cloth painters drop cloth for a few days and it worked well. I like the idea of corrugated panels, or I was thinking a sheet of foil-covered rigid foam insulation might also work well. Just have to secure it well so the wind cannot get under any cover.

[J.P.M.]

Thanks, I appreciate the tips. Probably going to look in to using a tarp somehow. I like the idea of building rigid panels, but I don't have a place to store them during the cold months.

You're Welcome.

[spareparts]

Thanks, I appreciate the tips. Probably going to look in to using a tarp somehow. I like the idea of building rigid panels, but I don't have a place to store them during the cold months.

[J.P.M.]

I've got what is a workable solution for my situation: Corrugated fiberglass roof panels.

My water heating solar collectors (2 ea., 4' X 8') are mounted in portrait and one above the other on the roof with 6" free space between bottom of collector and top of roof deck. I have 2 ea., 2' (26" actual) x 8' corrugated roof panels covering the lower collector. The corrugated panels are affixed to the collectors with bungy cords that wrap around the collector/corrugated panel at 3 places, bottom, top and middle. The bungy cords stay at their location by attaching to roof supports at those bottom, middle and top locations.

While the method is not exact, rocket science detail and precision is not necessary. usually cover the lower collector on my system to help avoid overheating during the non winter/warmer/sunnier portions of the year. Been doing it since I redesigned the solar DHW system in 2005. The covering scheme has worked fine during that time. I got thye panels from big box

If you use the method, a comment/two:
- From the standpoint of thermally induced mechanical stresses, it's probably best to cover an entire panel. A partial cover over one collector doesn't hurt much, and I do it occasionally, but if you do partially cover a collector, be careful to partially cover it in a way that's perpendicular to the direction of the flow, that is, cover the bottom of a collector rather than the left or right side of a collector.
- Also, cover the coolest portion of any collector or array of collectors first. That'll cost a bit of collector/system efficiency, not doing so may well defeat some of the purpose of partially covering an array in the first place. Reason: Controller sensors are usually and probably best located at points where the coolant temps. are highest. Those are usually at the high points in the system. Covering the highest collector(s) may well "fake" the sensor that tells the collector to turn on/operate when the coolant temp. is high enough into thinking the coolant/system is not hot. Meanwhile, the lower (and now uncovered) collector(s) are really cooking under what are called stagnation (no coolant flow) conditions. Now, thermosiphon action will mitigate this condition some, but the pump will run less with the result that the lower collectors will run hot, maybe hotter than if nothing was covered. Cover the coolest parts of a system first.
- Make sure you have a secure place to store the panels from wind or other things.
- FWIW, I cut a 3" radius into the corner of each fiberglass panel. I lacerate my hands and arms less now than before I cut the radii.
- The bungie cords seem to last about 4 seasons before they lose their elasticity and/or fail.
- I started with white fiberglass panels. They were ugly. I switched to dark gray. I've got the system temps. dialed in pretty good to maybe ~ 0.1 deg. F. or so. The effect on collector outlet temps. from the color change is undetectable by any method I use.

For anyone reading this who is considering but does not yet have a solar thermal domestic water heating system, consider a collector design that has a mix/consideration of a tilt that's closer to the winter optimum, and a preliminary size that's close to the economic optimum for that tilt. Reason: Winter collection will be optimized and summer overheating will be minimized if not eliminated.

That's probably not the most cost effective tilt or design because of the < optimum single tilt for year round consideration, but it is one way to address the summer oversizing and resulting overheating situation if/when limited to a single tilt,

The problem with doing that is most folks are unaware of other things that come into play by doing so that will most likely complicate the design in other ways.

[scrambler]

You could make a cover from a regular tarp, adding some straps to wrap around the corners

[spareparts]

Hi, I'm some what new to the solar experience. Bought a home with solar collectors on the roof for heating fluid to warm the house in the cold months.

Now that the weather is warm we don't need the panels running. Our first year the glycol toasted in the sun during the summer months.

So I'm looking for ideas on how to cover the solar panels during the summer months. A local solar guy suggested pond liner.

These are 3 each 4x8 foot panels so I'm not quite sure if pond liner is the most economical.

Thanks, appreciate it.