Like many others I’m contemplating an earlier opening due to our stay at home orders. I’m wondering if there is some calculation for determining how warm the water can be given a certain water temp and air temp and assuming that the panels are only used while it sunny. On a recent 50 F degree day the panels just sitting the sun were 120 F so it seems even with low air temps there is a decent amount of solar gain even if the water running through them was 75 to 80. At what air temp does solar become inefficient or counter productive and start cooling the pool?
Running Solar Heaters In Cool Weather
- Thread starter IsThisWhereIPutMyName?
- Start date
I think, with solar it's more about freezing then anything else. As long as the temperatures are going to be above freezing, you should be okay. It's only early April, so the chance of seeing below freezing temperatures, especially at night is still pretty high. Although I am in Canada, I am only about 30km North of the most southern spot, and generally we don't think about opening the pool before the end of May. Although I am starting the try to get leaves off the cover. It's hard though when they are under nearly a meter of water....
I don't have solar panels but if the air temp is higher than the water temp, you won't be losing heat even on a cloudy day. If the air temp is lower than water, you will lose some in the plumbing but gain a lot of heat if it is sunny outside.
I follow a local weather station near my house to track the solar radiation which will give you watts per square meter. You can calculate the square meters of your solar panels to determine how many watts per hour you could possibly absorb from the sun. Even on a day with decent cloud cover, you would still get some watts. I would say if you can run the solar panels when the watts are 300 or higher, you will be warming it up but you would have to do some math to get a correct number.
Here is a link for a random one I picked in MA so you will need to find a Personal Weather Station near your house which tracks solar radiation. The solar radiation is in yellow.
I follow a local weather station near my house to track the solar radiation which will give you watts per square meter. You can calculate the square meters of your solar panels to determine how many watts per hour you could possibly absorb from the sun. Even on a day with decent cloud cover, you would still get some watts. I would say if you can run the solar panels when the watts are 300 or higher, you will be warming it up but you would have to do some math to get a correct number.
Here is a link for a random one I picked in MA so you will need to find a Personal Weather Station near your house which tracks solar radiation. The solar radiation is in yellow.
Personal Weather Station Dashboard | Weather Underground
Weather Underground provides local & long-range weather forecasts, weather reports, maps & tropical weather conditions for locations worldwide.
www.wunderground.com
A pool automation system ought to handle this, well, automatically. @IsThisWhereIPutMyName? has no signature, so we don't know whether he or she has automation. Hint hint.
As soon as freeze danger is past, I enable solar on my Pentair EasyTouch. The ET allows me to set the temperature differential between solar and target.
There is no danger of accidentally cooling the pool with automation. I can set the ET to use the solar panels to cool at night, but that's rarely needed. This is one case where even a primitive automation system like the ET works much better than a dumb thermostatic solar controller.
As soon as freeze danger is past, I enable solar on my Pentair EasyTouch. The ET allows me to set the temperature differential between solar and target.
There is no danger of accidentally cooling the pool with automation. I can set the ET to use the solar panels to cool at night, but that's rarely needed. This is one case where even a primitive automation system like the ET works much better than a dumb thermostatic solar controller.
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You know, before I posted this I did update my profile, but apparently not my signature. I think I did it now.
My current solar automation is looking at the weather forecast and if it’s sunny I turn the valve to on and if not I turn it to off.
Everything is always absorbing heat from environment while also at the same time emitting heat back into the environment. When the absorption is higher than the emission, then things heat up. If I’m running water that’s warmer than air through the panels then they will want to emit more heat. It’s just the balancing act of the solar gain and if that’s enough to counteract the emission. I think that would be the case, since the panels laying in the sun and a cool spring day are still over 100F.
Glazed panels insulate the panels from the air and create a bit of a greenhouse effect and can be effective at lower temps from what I’ve read. I have standard unglazed panels and I wasn’t sure of the efficiency loss from a higher temp difference. I usually don’t start worrying about water temps until late May early June since there’s other things to do outside. I think I’m just going to try to be aggressive with it and see what happens. My goal is to comfortably swim when the daytime highs are in the low 70s. Usually we don’t think about swimming until were in the 80s for daytime highs. We’ll see.
My current solar automation is looking at the weather forecast and if it’s sunny I turn the valve to on and if not I turn it to off.
Everything is always absorbing heat from environment while also at the same time emitting heat back into the environment. When the absorption is higher than the emission, then things heat up. If I’m running water that’s warmer than air through the panels then they will want to emit more heat. It’s just the balancing act of the solar gain and if that’s enough to counteract the emission. I think that would be the case, since the panels laying in the sun and a cool spring day are still over 100F.
Glazed panels insulate the panels from the air and create a bit of a greenhouse effect and can be effective at lower temps from what I’ve read. I have standard unglazed panels and I wasn’t sure of the efficiency loss from a higher temp difference. I usually don’t start worrying about water temps until late May early June since there’s other things to do outside. I think I’m just going to try to be aggressive with it and see what happens. My goal is to comfortably swim when the daytime highs are in the low 70s. Usually we don’t think about swimming until were in the 80s for daytime highs. We’ll see.