Do solar pool covers really work?

[alchemysa]

I've had a number of pools and solar covers and they definitely make swimming more comfortable.

BUT I've never really thought much about how they work... until this thread. I've since googled quite a lot about the bubble type blankets and the thermal blankets and its remarkable how little is explained or known about how they work. Even quite large documents from swimming pool associations are pretty vague and confusing.

Heres what I think is happening...

Neither the solar or thermal blankets actually heat the water. The water will get just as warm or possibly warmer during the day WITHOUT the blanket. However, a blanket reduces evaporation, and evaporation causes cooling, so a transparent solar BUBBLE blanket MAY help warm the water during the day, although this benefit may be marginal at best as the blanket may actually reduce solar absorption. Not having to top up the pool with COLD water is also a benefit although this could possibly be countered by slowly topping up with water through a long black hose.

THERMAL blankets block out the sun so they REDUCE the warming effect of the sun during the day so should not be on the pool during the day.

The real benefit of bubble and thermal blankets is to reduce heat loss during the night. Thermal blankets seem to be more efficient at this than bubble blankets, although at greater cost.

This suggests that, for heating purposes, a solar blanket really only needs to be used at night. Doing so would considerably prolong blanket life as it would not become sun damaged (as long it was fully protected from the sun when on the roller during the day)

Consideration of aspects such as cleaning, evaporation and chemical usage really confuses the the whole issue.

I might be wrong about this stuff but, like I said, authoritive info is hard to come by.

 

[kenmac]

I've had a number of pools and solar covers and they definitely make swimming more comfortable.

BUT I've never really thought much about how they work... until this thread. I've since googled quite a lot about the bubble type blankets and the thermal blankets and its remarkable how little is explained or known about how they work. Even quite large documents from swimming pool associations are pretty vague and confusing.

Heres what I think is happening...

Neither the solar or thermal blankets actually heat the water. The water will get just as warm or possibly warmer during the day WITHOUT the blanket. However, a blanket reduces evaporation, and evaporation causes cooling, so a transparent solar BUBBLE blanket MAY help warm the water during the day, although this benefit may be marginal at best as the blanket may actually reduce solar absorption. Not having to top up the pool with COLD water is also a benefit although this could possibly be countered by slowly topping up with water through a long black hose.

THERMAL blankets block out the sun so they REDUCE the warming effect of the sun during the day so should not be on the pool during the day.

The real benefit of bubble and thermal blankets is to reduce heat loss during the night. Thermal blankets seem to be more efficient at this than bubble blankets, although at greater cost.

This suggests that, for heating purposes, a solar blanket really only needs to be used at night. Doing so would considerably prolong blanket life as it would not become sun damaged (as long it was fully protected from the sun when on the roller during the day)

Consideration of aspects such as cleaning, evaporation and chemical usage really confuses the the whole issue.

I might be wrong about this stuff but, like I said, authoritative info is hard to come by.

That is why I say they don't work.(at least for me) I get enough heat during the day and it's hot at night. SO, for me, I never saw any temp difference using the bubble/solar cover or not using it. I won't be buying another 1.

 

[Piston]

What is the solar heating method that some of you are referring to? Do you basically make your own heater using a bunch of black plastic pipe laying in the sun to circulate water through?

Does anyone have any pics of what this type of system looks like?

 

[Piston]

I ended up with this one, we'll see how well it works.

In The Swim 16 Mil Ultra Clear Pool Solar Cover 20 x 40 Rectangle:Amazonatio, Lawn & Garden

 

[Pixguy]

What is the solar heating method that some of you are referring to? Do you basically make your own heater using a bunch of black plastic pipe laying in the sun to circulate water through?

Does anyone have any pics of what this type of system looks like?

Here is the system I've priced for the pool in FL (winter) but haven't pulled the trigger yet.

 

[alchemysa]

Here is the system I've priced for the pool in FL (winter) but haven't pulled the trigger yet.

View attachment 380869

I'd suggest you give consideration to having an entirely separate pump and plumbing for the solar heater. That way you can run a small low cost heater pump during the day and only run the big filter pump when you really need to.

The heater pump doesn't have to pump hundreds of gallons a minute to be effective. A properly sealed solar heater needs minimal pumping to keep the water circulating through the system. Once all the air is out of the system the water returning to the pool 'sucks' water up into the heater (as long as the inlet and outlet are both under the water). You then only need a 'relatively' small pump to keep it moving.

My last pool was plumbed like that. But note that it also had an automatic 'floating ball' valve at the top of the solar panels to let the water drain out when the pump was turned off. And the system I describe is only suitable if all the pipes and solar panels are 'rigid'.

 

[C4Ranch]

Curious... I don't understand the physics behind your statement that moving water doesn't lose heat as easily. I understand the heat is transferred by one of three means... radiation, conduction, and convection. Convection being the operative word here. I would think the opposite is true.

My experience has been running pump during day heats water faster than at night. 30k gal 9' pool.

I believe its because the pump is circulating the water and when it's 100 degrees out its moving the deeper cooler water to the surface where it's warming up with the sun thus attempting to warm much more water than what's sitting at the surface if pump not running during the day.

I have no degrees in the field of thermal heating or pool operation. Just my experience and hours of worthless pondering. YMMV.

 

[dragoneggs]

My experience has been running pump during day heats water faster than at night. 30k gal 9' pool.

I believe its because the pump is circulating the water and when it's 100 degrees out its moving the deeper cooler water to the surface where it's warming up with the sun thus attempting to warm much more water than what's sitting at the surface if pump not running during the day.

I have no degrees in the field of thermal heating or pool operation. Just my experience and hours of worthless pondering. YMMV.

Yes, this makes sense. If the outside air is warmer than the water, moving the water past it will warm faster than if it is still. This is convection cooling/warming. Same of course holds true if the air is cooler. The water will cool faster if moving rather than still. One exception is that the pump itself will warm the water via conduction. The pump is warmer than the water and the contact surfaces will warm the water as it passes through.

 

[Pixguy]

................

Just my experience and hours of worthless pondering. YMMV.

You do that too?

 

[woodchuckie]

I have a few hundred feet of hose coiled on my metal roof and when the pump is on the pool a portion of the water circulates through the hose. I have the pool pump set to come on when the sun is shining on the hose. It adds lots of warm water to my pool which is in the shade after 2 every day so its needed to keep the water about 84 which is my ideal temp. Before the shade was so big I use to run a fountain at night to cool the water off from 90 back down to 82 or so.