Solar Cover Question

[doc8404]

It depends on the clarity of the cover. If it's a very clear cover, it will let a significant amount of sunlight through, both visible and some infrared and some UV. Such covers do truly aid heating of the pool during the day. For an opaque cover, if it's white or reflective then there will be little heating of the water, but if it's a dark opaque cover then there will be some heat transfer for thin covers such as electric safety covers. For bubble-type covers, there won't be much sunlight absorption and heat transfer unless the top part of the cover is clear and only the bottom part touching the water is black or dark.

So in order of heating, it is the following:

Clear bubble-type cover -- passes through the most sunlight, retains heat well
Clear-on-top, dark-on-bottom, bubble-type cover -- dark bottom heats up from sunlight and passes heat to the water, retains heat well
Dark opaque thin cover -- dark cover absorbs heat and passes it to the water, but the thin cover doesn't retain as much heat
White or reflective bubble-type cover -- does not absorb heat but retains heat well
White or reflective thin cover -- does not absorb heat and the thin cover doesn't retain as much heat

The main trade-off is that the clear covers also pass through UV so while you get heating from sunlight passing through, you also get breakdown of chlorine.

With no cover at all, there is substantial absorption of sunlight which heats the pool where a white plaster pool with 4.5 foot average depth absorbs 60% of the sun's light energy and heats the pool at around 0.7ºF per hour with noontime sun. Competing with this is water evaporation where the same pool would lose about 5ºF if 1/4" of water evaporated. Evaporation depends not only on the water and air temperature (except for perfectly dry air), but also depends on the humidity and especially on wind at the pool water's surface. See the thread Water Absorption and Heating from Sunlight for more technical details.

so with my 30' round ABG pool with light blue translucent cover in the summer, keep on unless swimming?

 

[mas985]

Yes, you are probably better off in most cases to keep the cover on. For those really hot and humid days, you can probably leave it off and it won't matter much plus more than likely you will be swimming.

 

[richierich]

great info thanks. I was just a bit confused. which one of your explanations does the standard all blue bubble cover fit into

 

[mas985]

From my experience, the translucent blue covers are very similar to clear cover performance. Clear covers are not really "clear" but more translucent as well, especially after a few months of operation. Both allow about the same IR transmissivity based upon measurements. The visible spectrum is obviously different but that accounts for less than about 15% of the heat transfer anyway. As for UV, since both types use UV inhibitors, I don't think transmission of UV is likely in either case.

 

[Kiss4aFrog]

I have an L-shaped pool and covering the smaller part is real hassle, so I've just been covering the long part which is about 75%. Is it worth using the solar cover if it only covers 75% of the surface area, or is it like leaving the windows open with the heat on?

Welcome to TFP

If it's a true "L" shape I can fully sympathize as I have a lazy L and I have to take that section and fold if over onto the main part before I roll it up. 75% is better than nothing by I'd cover that other part too if you need the heat but to also cut down on FC loss when you're not using it. Either have it all one piece and fold it over before you roll it up or have a separate section for it.

 

[borjis]

The reason lighter covers are recommended is that they are easier to handle and thicker covers
don't last any longer.

I always go with 8 mil blue translucent....it helps keep chlorine on covered sunny days and by myself I
can easily put it on and take it off.

I would suggest buying them on ebay...the pool co's selling them usually list buy it now prices that
are from 1/3 to half the cost they sell on their websites and most offer free shipping too.

 

[jmastron]

Welcome to TFP

If it's a true "L" shape I can fully sympathize as I have a lazy L and I have to take that section and fold if over onto the main part before I roll it up. 75% is better than nothing by I'd cover that other part too if you need the heat but to also cut down on FC loss when you're not using it. Either have it all one piece and fold it over before you roll it up or have a separate section for it.

Have you (or sumter) considered cutting the L-shaped part off and putting it on the pool separately? I don't use a reel, but cut my 17x35 into 2 sections (approx 17x17 each). I accordion-fold onto the deck then roll them up. To put on the pool, I unroll and am able to slide each section off the fold stack back onto the water pretty easily. A small L section would be an even better candidate for this. I finally took a GoPro video removing/applying, Youtube video coming soon

 

[semperfi]

We've been using a blue solar cover on our pool for 20 plus years. This is not scientific
but our pool is always much warmer than other pool owners we know. By the way just found this site I
have learned a lot about pool chemistry my pool installer, and store never taught me.
CYA is an eye opener.