Solar gain from auto cover

[DorsalSpine]

We are supposed to have some really warm weather for the next week or so. My water is 66 and I'd like to get as much solar gain as possible. I have a medium grey auto cover. I can leave the cover closed during the day or open it during the day and just cover it at night. My vote is keep it closed to avoid evaporation losses. Thoughts?

 

[mas985]

Is the cover in contact with the water or is there a layer of air between the cover and water. If the later, the insulation value would be higher so it might be better to remove the cover. However, if the wind is blowing hard, it might be better to have the cover on. It really depends on the conditions. You might just run some experiments and measure the heat gain during the day with and without the cover with differing weather conditions.

 

[bmoreswim]

I have the some color cover. I find that in still weather, the solar gain is greater with the cover open. Even with a breeze but with humid weather the same applies, as there just isn’t that much evaporation, so long as ambient temps are well above the water. My water is 77 degrees doing a combination of open and closed during the days and closed at night. I also get full sun on the pool from about 2 hours after sunrise until 1 hour before sunset. That also plays a big part.

 

[DorsalSpine]

The cover lays on the water so there isn't an insulating layer of air. I didn't think about the air/water temperature differential when I was worried about evaporation. The water is pretty cold in comparison to daytime air temps. I'll open the pool during the day and cover it at night until the water temps get a lot higher.

 

[mas985]

Evaporation is related to the difference in water temperature and dew point temperature (not air temperature). So evaporation will be higher for areas with lower dew point temperature even though the air temperature might be the same.