My thoughts on solar heating and help me make it better....

[aqualicious]

We have a 21ft AG pool (346 sq. footage). We installed four 4x10 Enersol panels on our south facing roof. Exactly set up like this:

http://www.enersol.com/content/view/13/28/

So with 160 square feet of panel we have 46% coverage. Sun exposure from 9-5 on panels. I zealously use my solar blanket (standard blanket that came with the pool). The kids have been using the pool alot....most afternoons, but when not in use the cover is almost always on.

Ideal pool temp for me and the kids is 83 but we'll swim at over 78+. hubby will only swim at 87+ degrees . I know.... he needs a spa.

My thoughts

My thoughts on the solar is mixed. Basically as the name implies you are at the mercy of the sun. I know...duh...I find the claims and assurance of pool store salesmen to be more optomistic than realistic. If you invest in solar heating you cannot get angry at the sun. You must learn to go with the flow and accept what you get. The beauty of it is knowing you can turn the solar on and not get angry at your kids if they only went in for 15 minutes or didn't go in at all. Paying to heat a pool and have that happen would make me very stressed at my kids.

The hotter/sunnier the weather is......the hotter your pool.
If you want to decide when your pool is hot....solar heating is not the way to go.

What surprised me

By leaving my hand or standing in front of the return I found that the within seconds of a cloud going in front of the sun you lose heat almost instantly. It's quite impressive how quickly it reacts. This summer has been extremely cloudy, so on average our pool goes up about 4 degrees per day....and frustratingly due to cool summer nights...loses about 3-4 degrees at night. That's with the panels running 9-5.
It surprises me because our pool is in full sun from noon to 8pm....so I'm not sure just how many degrees the panels are doing vs. direct sun on pool. According to the claims and our sun exposure, I thought the panels with a full days sun would warm up the pool 5-10 degrees.

Performance

With daytime temperatures having been around 20-25 (70 degreesish) pool temps with 9-5 solar have been between 78 and 85.
During a 2 week nice warm spell in August we enjoyed temps of 85-90 which allowed us one and half weeks of late night swimming!!!

I don't have anyone to compare with day to day....but I think our temps seem to have been generally a bit higher than others I've had casual conversations with who have no heating.

What's next?

We've already spent more that we initially wanted to.....approx $2000 but also want to do the job properly.

We have room to add atleast one more panel if not 2.

or

We could add a goldline automatic control

I was wondering if anyone else has any thoughts on our performance...if we are maybe overlooking something. Are we expecting too much? Have we just had a crappy summer?

Also for those of you who installed a goldline controller maybe after the face....how much of a difference did it make?

RE the goldline....right now we have a 3 way valve where the water diverts to the panels and we also have a valve we shut off at the bottom of the panel plumbing to stop the water from draining out of the panels when we turn off the solar. We find that it stop all the air bubbles upon turning the panels back on the next day.
So if we install a goldline auto control....
a) aren't the panel plumbing lines always going to reempty causeing air in the lines?
b) do you need to leave our pump on high 24/7?

Hope this helps anyone contemplating solar....and thanks to any who can answer my questions

aqualicious

 

[JohnT]

Air in the lines doesn't really hurt anything other than being noisy on startup. I find it's pretty effective at getting the bugs moving toward the skimmer in the morning if the cover isn't on. You can have issues with some panels overheating if there is water left in them if the sun is out.

I don't know about your area, but this hasn't been a good year for warm water here in Indiana. Cold nights and cool days haven't given me much to work with.

I think an auto control system would be a good investment, as would more panels. I'm messing with the idea of a homebrew system (I'm an electrical engineer), not so much because existing systems are lacking, but because I could add data logging and internet control and status monitoring pretty easily. And it would be fun

I run my pump as long as there is solar gain to be had. That starts about 1030 and ends around 545 in the evening. The low sun angle just doesn't add much heat. I have kids at home during the summer, so if I notice the weather changing, I call them and have them adjust the system.

I find that I want to keep track of the forecast and bank extra heat if I see the opportunity. The automated system wouldn't do that on its own.

That seems like a lot of money for a four panel system. Did you pay to have it installed?

 

[aqualicious]

The panels were $299 each, plus start up kit $30. The piping which wasn't as cheap as we thought it would be had to go about 50 feet and then up the roof. With our lovely CAD taxes, that what it came to.
We decided to spend extra on the Enersol due to the better quality than the Sunheaters, which is the only other one available in this area. The Enersol can also be left installed during winter.

Because of the cloudy weather we've had, some days had a bit of sporadic sun which we couldn't take advantage of and other days we were gone at the trailer..and such and would have left it on if we knew it would turn off at night.....hence wondering does the auto control really give that much more heat. Otherwise I'm home and usually am the one to run outside and turn it on and off.

The goldline auto package which comes with sensors and valve runs about $499 on sale here.

 

[dmanb2b]

I hope I did not miss it above, but do you cover the pool at night with a solar cover? Thank should significantly cut down on your temp loss overnight. Our pool is at 78 deg today, with today's high at 76 and last night temps got into the 50s

 

[kjcole]

We have seen better performance (in terms of heat loss/gain) with about the same % coverage as you, but we also have struggled to reach the mid-70's during the extended cool/cloudy/rainy sessions we experienced this summer. Our panels are on south-facing racks that are unobstructed and we run the filter from 8:30am-6pm. However, our pool is snugged up tight to the west side of our 2 1/2 story house, AND is blocked early from the west sun by our 1-story detached garage. So we get full sun on the pool only during the middle hours of the day. We absolutely needed an auxiliarly heat source (solar panels). We also use our solar cover religiously at night and when the pool is unoccupied. I assume that we've experienced the same unusual weather (July was a record month for lowest average temp around here; August was a record wet month around here = lot's of clouds). Assuming all of this, I concluded that the Goldline controller helped quite a bit on those really cool but partly cloudy days when someone with a manual system would simply leave the diverter valve closed all day to prevent heat dissipation. I could use another panel for whacky summers like this. But I'm assuming we'll return to the typical hot and steamy summers I'm used to in eastern Iowa. Overall I'm very happy with our results since installing the panels in June, considering the less-than-optimal location of our pool re: sun exposure.

 

[JCJR]

When researching Solar Heating a couple of years ago, I got a lot of feedback stating that you need a auto-controller to prevent all the heat gain to be lost by cloud cover. When the controller senses that the panel temp is < 5 deg warmer than the pool temp the controller shuts off the flow of water to the panels. You can actually have the solar panels remove heat from the pool during the day if your not turning off the flow at the right time. In sunny FL, I witness my controller shutting water flow all the time to the panels.

 

[lborne]

That goldline controller price seems high. Don't know if you were quoting CD or USD, but either way it is high. Have you looked at E-bay. I've seen a system for $260 with valve, actuator, and sensors.

Also, you may want to check craigslist or such right now. Here where I am, many homes bought just a year or two ago are in forclosure and the owners are stripping them and selling everything before the bank takes over. So I've seen 1-2 year old panels going for 25% of their new price.

JCJR - I heard just the opposite. That controllers were needed just for those in northern climates to get the max from their system. But here in Florida they were not needed because just 1 hour of sun heats the entire roof and attic, and even if a cloud comes over, the panels will absorb some of the heat from the roof and attic. However, I was told I might want to install a controller to keep the temp from getting too high in the summer.

 

[kjcole]

I bought my Goldline controller (kit with 3-way valve, sensors etc) off E-bay for much cheaper than the on-line retailers. Keep scanning e-bay, especially as we get into fall/winter.

Kelly

 

[zephans]

Hi aqualicious,

In your situation I'd definitely get an extra panel or two.

Also you typically WANT to have the solar panels drain whenever they aren't in use unless you want some cooling. The biggest reason is that at night your solar panel surface area is effectively a radiator. Turn on the panels in the morning and you have a fresh batch of cooled water . Furthermore if the water cools enough relative to your pool and solar water is still connected to your pool water then it can create a thermosiphon which starts a small current COOLING your pool at night . For vertically aligned panels (as shown in your posted link) water can drain easily. For horizontal panels like mine a common installation technique is to mount them at a slight angle to help drainback when pump is turned off. In both cases a vacuum release is needed to let air in (thus letting the water back down).

Note that the bubbles will mildly increase PH if they are continuous, but are harmless if they are just temporary result of displacing air in the solar panels.

FYI: I live near Seattle in a convergence zone, so cold and cloudy are part of my culture . Typically our pool is between 65 and 72 between late May and early September. I just finished installing my SHW array (~50% of pool surface area) a couple weeks ago in hopes I can eek out a few more weeks and perhaps not have to pull out the wet suits as often. So far I've seen 5 to 8 degrees, but still very rare we get to 80 degrees. It's free and definitely better than nothing. I used to be a polar bear but now I prefer 78 degrees before I even consider a dip. I spent about $450 on panels (www.craigslist.org) but had to build a $1,000 deck roof for suitable mounting area. I haven't had time or funds to get the automatic controller, but I plumbed an area for it when I get the chance.

IMHO for northwest North America solar panels won't live up to the marketing claims of 10-15 degrees, even if doubling recommended size. That said if you get over 50% of pool surface area you will significantly knock the edge off the pool for free.

 

[aqualicious]

thanks for all the advice and thoughts.

Last week was really nice 25 degrees each day and mostly sunny each day.

We started out with 68 degrees. Each day we gained about 5 degrees and would lose 4 at night with a net gain of about 1 degrees each day (2 later on in the week). By Wednesday we hit 78 and enjoyed 78-80 peak daytime temps for the rest of the week.
If we can have a nice september like this I will be happy.

Here's another question....

I have a 2 speed pump and turn it on low for the night after we turn the solar off.

Do you think that filtering the water at night, having it go through pvc also contributes to overnight heat loss.
We decided to just turn off the pump at night (not sure if that's a good idea to begin with) and I think we had one less degree heat loss overnight. Makes sense?

 

[zephans]

Water traveling through PVC at night will cool it a little, but not enough to fuss over. Water traveling through your solar array at night would definitely cool the pool like a radiator. That's one major reason why a bypass valve is important component for solar hot water configuration. Heat loss due to not having a solar blanket on overnight would be much greater than PVC piping heat loss.

If you are bypassing the solar array at night then I'm actually surprised you noticed one degree loss difference when leaving pump on at night. Were both days and nights similar temp? If you don't have a solar blanket on then was the wind speed different? Perhaps there is another explanation for heat loss than PVC pipe + low speed filtering at night.

 

[aqualicious]

Yes, we are bypassing the solar at night. And we use the blanket every night.

Definately nighttime temps can have something to do with it.
Last week monday started out with just under 5 degrees at night and progressively got higher to about 12 degrees the last couple nights.

Guess that explains it. I guess I'll go turn by pump back on for the night.