Quick Solar Heater Question...

[chriszke]

I understand how the channeled black mats are designed to work. The radiant light energy from the sun falls upon the black mat, heating it...then the water comes into contact with the black plastic & absorbs the heat...yada yada...

I also understand how, if water is channeled through the mat at night...assuming the air temperature is cooler than the water...the mats can be used to cool a pool.

Then this stands to reason as well...right? :

If my pool water is cold (right now at 70 degrees) and the sun is going down (no longer shining on the mats)...but...the ambient air temperature is still over 70 (and right now it's 83)....then I'm still picking up heat through the mats.

Granted...at a reduced level...but I'm still heating the pool through the transfer of ambient air heat through the mat.

And allowing the pump to channel water through the solar heater, even while in shadow...is raising my pool temps (albeit slowly).

Any flaw in my analysis here? Thanks...

 

[stevenbrla]

your analysis makes sense to me... heat most always transfer from the warmest to the coolest...(assuming the cooler place is a conductor of heat)

assuming that there's no place in the system that is cooler than the initial water temp.... like air...

obviously if you are feeding the water back in and its running over a spillover where you're relieving the heat into the (cooler?) air, you'll be losing heat to the air.... right?

 

[JohnT]

Two flaws that I see in the logic. Air contains relatively little heat compared to water at the same temperature, so there really isn't much energy to transfer, and since the temp of the panels isn't much higher than the water, any transfer that does occur will be slow. The other problem is that while black things absorb infrared well and heat up, black things also radiate heat to the universe very well too. This is the same reason arctic animals are white instead of black.

The energy you are using to run the pump is far more than you are gaining from the warm air. An accurate thermometer in the flow of both the inlet and outlet water is the best way to know when to run the solar.

 

[JCJR]

I agree with Chris. hot goes cool and cool goes warm until they find an equilibrium. If your pool is 70F and ambient air is 83F then water running through the solar panels will raise in temp, maybe not efficiently but it will change. Same as your analogy of cooling the pool water when temp are cooler, which I guess will be more effecient.

 

[chazas]

Our solar heater has a temperature sensor on the roof and in the water stream - so long as the ambient temperature on the roof is above the temperature of the pool water, it operates.