I'm picking plastic bits out of my pool as yet another pool cover disintegrates. In our area, there is no pretense that pool covers are recyclable. Pieces of it will be stuffing my trash barrel for at least a month. That's a hidden cost (not to me, but to the environment) in the use of solar covers. (By the way, I noticed that the bubbles within a few inches of the seams failed before the bubbles further away from the seams. Something (heat?) in joining sheets at the seams appears to weaken the bubbles.)
As I go to pick out a new solar cover, I find nothing has changed in the last couple of years. As consumers, I think we all agree that the primary purpose of solar covers is to prevent evaporation, thus saving water and either saving energy or extending the pool season. The advertising verbiage about the bubbles focusing sunlight is just an advertising gimmick..
Saving on chemical costs is a secondary advantage. There is some advantage to solar covers that filter out that part of sunlight that breaks down hypochlorous acid (chem geek indicated it was around 235-240nm in this thread - That's UVC). I don't know whether the thinnest (8 mil) covers block 100% of that wavelength, or whether thicker covers block more than thinner covers.
Meanwhile, the pool cover needs to withstand UV radiation itself as well as be resistant to the effects of pool chemicals. A quick web search indicates there are a number of additives to protect polypropylene (etc.) from UV radiation. I presume these are already in what we buy, but what I saw suggested longer life that we're seeing. Perhaps the pool chemicals interfere with or leach out the additives. I wish the vendors or manufacturers, or some testing entity can identify exactly what is in we get sold.
But, my question today, why do all the solar covers have thin-skinned bubbles?
The covers that I've had over the last 20 years have an upper layer that is flat and relatively thick compared to the skin of the bubbles. The material that is the skin of the bubbles is quite thin. In my experience, it is usually the skin of the bubbles that fails first. That isn't surprising because a thinner material is likely to degrade or be abraded more quickly.
What is the purpose of the bubbles? I suspect they are instrumental in the buoyancy of the the cover. They also implicitly cause users to always orient the covers the same way. Potentially they provide some rigidity of the cover or other structural benefit (consider how Saran Wrap folds & clings to itself).
Or maybe the bubbles are just there to make the consumer think they provide some benefit ("focusing the sunlight", "transferring heat to the water") That way, consumers don't go out and buy cheaper plastic sheets that are not specifically sold for pools (Lots of examples at Amazon).
Why aren't pool covers offered that have a flat surface toward the water? If a 12-mil pool cover was a single sheet of plastic, with no differentiation in cross section, why wouldn't that be a better option? The full 12-mil of plastic would have to fail rather than just some thin (1-mil?) bubble layer.
I'd welcome any manufacturer to tell us why their solar covers are constructed the way they are. (Hmmm... Maybe I should search for patents.)
The one possible answer I can imagine is that the bubbles and the main sheet are different materials. The bubbles are more resistant to pool chemicals and are there to help protect the main sheet, lifting it above the water. The main sheet is more UV resistant and protects the bubble layer. (Even so, why not make the skin of the bubbles thicker?)
Is anyone here knowledgeable about the construction of the solar covers - why the design is pretty uniform, and what UV protection mechanism is used for these solar covers?
As I go to pick out a new solar cover, I find nothing has changed in the last couple of years. As consumers, I think we all agree that the primary purpose of solar covers is to prevent evaporation, thus saving water and either saving energy or extending the pool season. The advertising verbiage about the bubbles focusing sunlight is just an advertising gimmick..
Saving on chemical costs is a secondary advantage. There is some advantage to solar covers that filter out that part of sunlight that breaks down hypochlorous acid (chem geek indicated it was around 235-240nm in this thread - That's UVC). I don't know whether the thinnest (8 mil) covers block 100% of that wavelength, or whether thicker covers block more than thinner covers.
Meanwhile, the pool cover needs to withstand UV radiation itself as well as be resistant to the effects of pool chemicals. A quick web search indicates there are a number of additives to protect polypropylene (etc.) from UV radiation. I presume these are already in what we buy, but what I saw suggested longer life that we're seeing. Perhaps the pool chemicals interfere with or leach out the additives. I wish the vendors or manufacturers, or some testing entity can identify exactly what is in we get sold.
But, my question today, why do all the solar covers have thin-skinned bubbles?
The covers that I've had over the last 20 years have an upper layer that is flat and relatively thick compared to the skin of the bubbles. The material that is the skin of the bubbles is quite thin. In my experience, it is usually the skin of the bubbles that fails first. That isn't surprising because a thinner material is likely to degrade or be abraded more quickly.
What is the purpose of the bubbles? I suspect they are instrumental in the buoyancy of the the cover. They also implicitly cause users to always orient the covers the same way. Potentially they provide some rigidity of the cover or other structural benefit (consider how Saran Wrap folds & clings to itself).
Or maybe the bubbles are just there to make the consumer think they provide some benefit ("focusing the sunlight", "transferring heat to the water") That way, consumers don't go out and buy cheaper plastic sheets that are not specifically sold for pools (Lots of examples at Amazon).
Why aren't pool covers offered that have a flat surface toward the water? If a 12-mil pool cover was a single sheet of plastic, with no differentiation in cross section, why wouldn't that be a better option? The full 12-mil of plastic would have to fail rather than just some thin (1-mil?) bubble layer.
I'd welcome any manufacturer to tell us why their solar covers are constructed the way they are. (Hmmm... Maybe I should search for patents.)
The one possible answer I can imagine is that the bubbles and the main sheet are different materials. The bubbles are more resistant to pool chemicals and are there to help protect the main sheet, lifting it above the water. The main sheet is more UV resistant and protects the bubble layer. (Even so, why not make the skin of the bubbles thicker?)
Is anyone here knowledgeable about the construction of the solar covers - why the design is pretty uniform, and what UV protection mechanism is used for these solar covers?