Solar Heating - Adding Panels Placement Suggestions

[Jon123]

When we bought this house, it was already plumbed for and the house had 4x 2ft x 20ft solar panels.
I put them on the roof, and over-engineered things a bit so they'd stay put (courtesy of the H2T Sun Industries install examples IIRC):


After a few years of this, I'm thinking I'd like to double the installation.

The pool has about 500sqft of surface area, and the panels up there right now are only 160sqft.
I'm in MA and I routinely see during the hot sunny days we've been having recently that I'll get 1.8-2.0°F increase off these.
But at night, I'm sometimes losing ~1-1.5 degrees.
My hope is that by doubling the panels I'll end up getting something like 3.5-4°F increase, and if my loss stays similar to where it is today, I'll actually net closer to 2°F/sunny day.

As you can see the roof and existing plumbing don't immediately lend itself to doing this, but I think this setup would work?



So the idea would be to move the existing panels down about 4ft, which would open up enough room for another 4 panels in an ideal (from a plumbing perspective) location.
Then I'd pipe the water in series from the first bank of panels to the second (new) bank of panels.

There is a bit more shade on the top half of the roof, but it's not as bad as the photo makes it look - this photo was taken in March and the angle of the sun is a bit better once summer hits.

Any other suggestions or concerns about this change?

 

[needsajet]

I'd say it will probably work fine as you have it planned. I'll just mention that one design element is to maximise flow through the system, so parallel would be better than series, but I suspect it won't be much of a difference between parallel and series, especially compared to the much bigger gain of adding surface area. Judging by spacing, you might be able to add 3 panels in parallel between the skylights, which might be a worthy option.

It's worth mentioning that adding elevation changes things. You'll probably be fine, but if the system is borderline on filling to the tipping point, then going higher could be problematic.

Always worth a mention is use of a pool cover, especially early in the season. Some get scared off covers because of looks. An option is to have disks and just use them for a while in spring, then fold them up and put them away until the following year. Any amount of covering reduces evaporation which reduces the amount of overnight heat loss, so don't ignore covering if you've been led to believe that only 100% coverage can work.

Nice to meet you via TFP

 

[Jon123]

Thanks @needsajet, nice to meet you as well!

Judging by spacing, you might be able to add 3 panels in parallel between the skylights, which might be a worthy option.

I considered this, but I figured I could get +40sqft with the version I proposed. Having said that, it would be much easier to just add 3 of them - moving the whole rig probably won't be very fun. I'm going to have to think about this a bit more.
Hmmm, I could add 6 panels if I were to work around those center skylights. I'd need to double check how much sun we get in those spots though.

It's worth mentioning that adding elevation changes things. You'll probably be fine, but if the system is borderline on filling to the tipping point, then going higher could be problematic.

Any recommendations for testing this? I don't remember if I ever checked the pressure at the panels, but I'm 90% sure I did and the readings were good. I know the filter pressure shows +5 psi when running to the panels. Is there something else I should be concerned about here?

Always worth a mention is use of a pool cover, especially early in the season.

Definitely - I had the cover on until 2 days ago, it's a nice thick thermal cover. I took it out to power wash it, then the power washer decided to choke on me (of course), so right now the cover is just killing my lawn - I'll put it back on tonight.

 

[needsajet]

Sorry, for my out of place response! For some reason this popped up as just the solar upgrade under unanswered, so I had a go. Anyhoo...

WRT testing proposed highest point...

All you need is a wee bit of positive pressure at the highest point of the system. If there was a way to attach a garden hose or something and take it to that highest proposed point, then you'd know. If water is still coming out, your pump generates sufficient pressure to go higher. On my system, it's an adjustment of a three-way valve, so I could just close down the diversion a little if I wanted to go higher (that is, send more flow to the solar). My system has a vacuum relief valve at the highest point, with a removable cover. My valve is set so that with the cover removed, water spurts out anywhere between 1.5 ft to 3 ft. If yours is similar, you could remove that cover and see how high you can make the water spurt out (no wind). If that's higher than the highest proposed point, or nearly so, you'd probably be good to go.

Another option is temporarily piping up to the new highest point and see if the system fills normally. (assumes your system drains after use, which most systems do)

A pressure gauge might not work because you're checking a small difference.

 

[Jon123]

Sorry, for my out of place response! For some reason this popped up as just the solar upgrade under unanswered, so I had a go. Anyhoo...

Not your fault - two of my posts got merged, then unmerged, so things are a bit jumbled right now. I think Marty is going to fix it though

All you need is a wee bit of positive pressure at the highest point of the system.

Gotcha - so I should have mentioned, this is a flat roof. On the inlet side, I placed the panels on top of the stone pavers, so they are just about 2 inches higher than the outlet side.
This probably doesn't do much, but it gives it a minor decline.
If I add the extra panels, I'd just need to figure out how I need to handle things in that regard, but my guess is I can just place them and it will be fine no matter what given the very small variances.

 

[needsajet]

OK, if they're flat, just be extra careful about freezing. Normally rooftop solar is installed so it drains between uses.

 

[Jon123]

The panels up there do drain when the pump turns off right now (the vacuum relief seems to do it's job). It sounds like a lot of water coming down - but I don't know how much water remains in the panels. When we close the pool for the season we blow the lines to get all/most water out. There was a night there about 2 weeks ago where we had 1 night of frost after not having them for a month - that scared me a bit, but all is well.