Solar Sizing advice

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jeffblue said:
http://www.jacuzzi-spa-covers.co.za/images/sunwise_pool_blankets.jpg?79

i think you might be co-mingling two different products. solar covers and solar heaters. 'solar covers' don't really have anything to do with solar (in fact their primary use is at night), and are a pretty misleading term. they are more or less a giant sheet of bubble wrap that prevents evaporation, which is the main cause of heat loss. they don't really help you increase your temperature, but rather prevent temperature loss overnight. the less heat you lose at night the higher you start the next day. they are very beneficial though because heat loss can be 5-10 degrees at night and thats 5-10 degrees less your heater, no matter what kind it is (gas/elec/solar) has to work to recover that heat. solar blankets shouldn't cost more than 200 dollars.

a solar pool heater is actually a 'panel' of strips of black thin piping that is placed on the roof (or sometimes on the ground in some setups) that essentially works by having water pumped up to the roof, which is generally 120-160 degrees in summer, absorbing heat from the roof, and then returning to the pool. These systems are the most expensive to install, but have no additional running costs aside from the pump. These are the units that get temperature increases of 10-15 degrees.

this is a solar pool heater
http://poolheaterworld.com/wp-content/uploads/2015/06/pool-solar-panels.jpeg

this is a solar blanket

http://www.jacuzzi-spa-covers.co.za/images/sunwise_pool_blankets.jpg?79
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Exactly my point! I know the difference. But the solar heater ratings I was seeing assumed you were going to use the solar "bubble wrap" covers when the pool was not in use. Yes, they were combining the two to show unrealistic solar energy gains. Now I can believe that they could provide 2 degrees/day and with using the blanket you would not lose that at night and then another 1-2 and so on until you are at 10 degrees total for the season. I'll go out on a limb and say if your pool is in the sun you will get 1-2 degrees rise per day with it just sitting there.
 
I went to work this morning my pool was at 82 F
Came home and on my way to go swimming in 90 F water.
At about 38%, not piped in correctly yet ( need reverse return ), booster pump weak atm also.
May 19th with only 90 sq ft of homemade we hit 90 F.
 
The way I look at it;
Gas Heater = purchase and install + gas price + pump running
Heat Pump = purchase and install + electric price + pump running
Solar = purchase and install + pump running
If you have the room, a suitable surface, enough sun light per day, along with a solar controller.
Gas and electric will extend your season much longer then solar, but when air temp hits the high 70's my desire to swim fades rapidly.
 
Who did this, you?
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Yes

Is this a real world collection of data with each system?
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It uses empirical formulas for heat loss and theoretical formulas for heat gain.

I tried to follow it and I think I did - it looks like there was a 1-2 degree/day rise with Solar?
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Yes, but that depends on the size of the panels vs pool.

Do you know how to make an excel pivot table with this data?
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The format probably doesn't really lend itself well to a pivot table but you could try. The intent was to create scenarios in each of the columns which can be expanded if desired.
 
IMHO the best solution is a NatGas heater supplemented with solar. I am in Toronto, which is a bit cooler than where you are in NY. In warm summers, like last year, the solar heating can keep your pool in the mid 80s if sized correctly. But when it is cooler, or in the spring/fall you may need the gas heater to get it to where it is comfortable to seim. And this summer I have needed gas a fair bit to keep it warm.

I keep my gas heater set to about 81. On sunny, warm days my solar panels get the pool up to about 86. This summer the gas heater often kicks on in the morning for a couple of hours. Note - my solar heating is from evacuated tube panels which, in hindsight, may not have made the most sense.

I don't have a solar cover because it is too much of a PITA to put on and off and I don't have the room on my deck for it. Plus I have an irregular shaped pool. When I was growing up in the late 70s/early 80s my parents had a pool with a solar cover so I have experience in the pros and cons of them.
 
Well, looks like my roof made the decision for me, since i can only fit about 500 sq feet of heliocols. i was able to get a quote for 5750 installed including labor and controller etc for ~500sq feet (i think its actually like 496) of heliocols including. install date is set for next friday. maybe i'll actually get to swim this season.
 
wayner said:
IMHO the best solution is a NatGas heater supplemented with solar. I am in Toronto, which is a bit cooler than where you are in NY. In warm summers, like last year, the solar heating can keep your pool in the mid 80s if sized correctly. But when it is cooler, or in the spring/fall you may need the gas heater to get it to where it is comfortable to seim. And this summer I have needed gas a fair bit to keep it warm.

I keep my gas heater set to about 81. On sunny, warm days my solar panels get the pool up to about 86. This summer the gas heater often kicks on in the morning for a couple of hours. Note - my solar heating is from evacuated tube panels which, in hindsight, may not have made the most sense.

I don't have a solar cover because it is too much of a PITA to put on and off and I don't have the room on my deck for it. Plus I have an irregular shaped pool. When I was growing up in the late 70s/early 80s my parents had a pool with a solar cover so I have experience in the pros and cons of them.
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yea it seems like with solar you need to use a blanket, which is fine with me. i have a rockys roller reel which is easy enough to use. my fiancee can take it on and off the pool herself.

how much do your gas bills run since you're only supplementing the solar and the gas isn't your primary heater? around here nat gas runs about 4 dollars an hour for a pool heater. if i already had a gas or electric heater i could see myself supplementing with it if i really wanted it super warm here and there, but this purchase was born out of needing to replace a broken heater.
 

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yea it seems like with solar you need to use a blanket, which is fine with me.
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With any heating method you should have a cover. Especially for those methods that cost a lot like NG and electricity. Otherwise, you are just throwing away money.
 
mas985 said:
With any heating method you should have a cover. Especially for those methods that cost a lot like NG and electricity. Otherwise, you are just throwing away money.
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agreed. If its a matter of convenience and money doesn't matter (which i imagine it doesn't if you use a NG heater with no cover, why not get an automatic solar cover? it'll cost less than you'll spend on heating a pool with no cover, and then theres no inconvenience.
 
Information that pertains to your local situation. Lat, long, weather, pool size, cover size, solar size etc.
 
So, update, the panels are being installed now. The 496 square feet of panels that the installer and i originally discussed have been installed. i was under the impression originally that this would be 'maxing out' my roof in terms of space, however he informed me that this is not the case. i have room for another 4x8 panel where the green arrow is and room for 4 more 4x12.5 panels where the yellow arrow is.

at 496 i'm sitting at 62% coverage. the extra 4x8 up top puts me at 528 sq feet (66% coverage). if i add the 4- 4'x12.5' panels to the awning it will add another 200 sq ft and put me at 728sq feet (90%). he is charging me 250 each for the panels. before these additional panels, the installation quote was 5,750. this would bring it to 7,000 even.

Is it worth it to just max out the space to get from 62% to 90%. will it make that much of a difference in performance? (max temperature/recovery time). i will be using a blanket regardless. the installer isn't being pushy at all, he seems to indicate that maxing out the awning is overkill, so its not like he's trying to upsell me.

right now i'm leaning towards just doing the extra 4x8 to 'max out' the top section, and then seeing how this performs for the next 2 weeks and next season and go from there, but that being said, there are obvious benefits to doing it now in terms of saving on labor since he is already here doing the work with his crew.

i don't want to waste money and i'm also not in love with the aesthetics of the panels being on the awning as they would be very 'in your face'.

ErInetI.png
 
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Well, the simple answer is that going from 496 sqft to 728 sqft will add 728/496 -1 = 47% more heat.

If easy enough, I might do as you are thinking. Add the 1 on the top and see how next season goes.
 
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