swimming pool solar covers vs. "pills"

The wind is howling outside like a winter storm, but some day it's going to warm up and I'll want to open my in-ground swimming pool. In order to extend the season (I live in Maryland), I'm thinking about either a solar blanket or a "pill". The former appear to be made out of the same bubble wrap you see in packing, and require a reel to take them off the pool. The latter is apparently a substance that slows down evaporation, which presumably is the main form of head loss.
The pills are not supposed to be as efficient as the blankets (perhaps the blankets have a slight insulating value, and at a guess they're better at retarding evaporation); the ad claims 60% of a blanket's efficiency. On the other hand, a blanket plus reel for my size pool (22x44) costs a minimum of $700 and are warranted for 6-8 years, while the "pills" cost maybe $30 for a four-pack and last "up to" 30 days (I'd need two at a time for my size pool). So figure four to six per season (a month or so at beginning and end of season). And the blanket looks like a lot of hassle to put on and take off, and to store when it gets hot out, and in the winter.
Presumably the chemical from pill doesn't feel oily when you're swimming.
Thoughts? Given the difference, I'm leaning towards the pill, but I'm skeptical about how well they work. And it's hard for me to do a scientific comparison, since I only have one pool :-).
Mike Maxwell
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On 15 Apr 2007 20:07:00 -0700, " snipped-for-privacy@ldc.upenn.edu"

Ah, faith. Isn't it wornderful.
It sounds like were talkin about 60 dollars for the first and third year for pills, and 30 dollars every second year.
So if it would help learn which is better, you've got little to lose by starting out with thepills. Unless somehow they are worthless. But it's still only 60 or 90 dollars for the first one or two year.s
Even if you have to buy the blanket, you'll be buying it later and it will last to a later date.
I hadn't thought about it but I guess evaporation does cool of the water in the pool. Just like one gets cold when he gets out of the bath, but after all the water on him evaporates, he starts to warm up again. Even without a robe.
Remember, don't take these pills on an empty stomach.
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snipped-for-privacy@ldc.upenn.edu writes:

Link for these pills? What are they made of?
Don't forget a blanket is 100s of square feet of more stuff to keep clean.
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Nothing to keep clean. As a matter of fact the cover keeps the pool clean.
--
Steve Barker




"Richard J Kinch" < snipped-for-privacy@truetex.com> wrote in message
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On Mon, 16 Apr 2007 08:24:30 -0500, "Steve Barker"

So leaves and sticks and bird poop won't get on the cover when it's keeping the pool clean?
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YA, you just roll them up, and roll them back out. OR you can use the leaf blower to blow the loose stuff off before or during the roll up process. If the cover weren't there, those items you mentioned would be in the pool.
--
Steve Barker




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Just like he said. You have to clean it.
wrote:

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solar pills aka liquid solar blanket, solar fish etc...
isopropyl alcohol 80-90%.
http://www.sunsolar.com http://www.ecosavr.com/documents/MSDSHeatsavr.pdf
best regards,
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On Apr 16, 12:33 pm, snipped-for-privacy@gmail.com wrote:

also see us patent 6943141
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The alcohol is just a solvent for the active item: octadecanol aka stearyl alcohol, greasy stuff used as a cosmetic base. Kind of like "pouring oil on the waters".
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On Mon, 16 Apr 2007 22:36:50 -0500, Richard J Kinch

Does this mean that one woudln't have to put on skin oil after swimming. I'm not talking about sunburn protection, just oil that some peopel use. Otherwise, might not be so good, depedning on how much there is.
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mm writes:

The layer is pretty thin, so you won't get much. But not unlike bath oil, yes.
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On Tue, 17 Apr 2007 23:07:51 -0500, Richard J Kinch

Yeah, when reading my post, I realized I had never heard of skin oil.
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NREL says 1550 Btu/ft^2 of sun falls on the ground on an average 53.4 F April day in Baltimore. The average humidity ratio w = 0.0052, with V = 10.4 mph average windspeed, which makes the airfilm conductance about 2+V/2 = 7.2 Btu/h-F-ft^2.

ASHRAE says an uncovered A ft^2 pool loses about 100A(Pw-Pa), where Pw and Pa are pool and air vapor pressures. Pw = e^(17.863-9621/(460+Tp)) "Hg (100% RH at Tp (F)), approximately, and Pa = 29.921/(1+0.62198/w).

Maybe R1 with 80% solar transmission, for a clear vs blue blanket.

You might weigh a pill and chop it up or dilute it several times, homeopathic-like, to treat water in one dark plastic bucket (does the coverage formula include depth?), and put a pool cover sample over another bucket of the same kind...
If the pill completely eliminates evaporation and you wrap both buckets with a few layers of bubble wrap with black plastic on the outside, the covered one might gain 1240 Btu/ft^2 = 24h(Tc-53.4)1ft^2/R1, which makes Tc = 105 F :-) The pill version might have 1550 = 24h(Tp-53.4)1ft^2x7.2, which makes Tp = 62 F.
These will both work better if you paint your pool black or let it get muddy, like a natural lake in the sun.
Nick
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It might be about 59 without the pill...
20 W=.0052'humidity ratio 30 PA).921/(1+.62198/W)'ambient vapor pressure ("Hg) 40 FOR TPX.78 TO 58.8 STEP .01'pool temp (F) 50 PW=EXP(17.863-9621/(TP+460))'pool vapor pressure 60 GAIN50-24*(100*(PW-PA)+(TP-53.4)*7.2)'net gain (Btu/day) 70 PRINT TP,GAIN 80 NEXT
58.78 2.795166 58.79 .6347656 58.8 -1.525879
Nick
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I really can't imagine how any chemical treatment would cause a solar gain. My vote is for the solar cover. They work great. They prevent evaporation, insulate to a small degree, and the very design of them causes solar gain.
--
Steve Barker




" snipped-for-privacy@ldc.upenn.edu" < snipped-for-privacy@umiacs.umd.edu> wrote in message
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I also live in Marytland...and last week or the week before when I peaked under my cover the water was already GREEN... darn..
However I have no experience with these Pills...but years ago I did try using a blanket in the spring and again in the fall .. honestly it was moor problems then it was worth becuase the kids were in and out of the pool every 15 minutes.. their mother (I was at work) got sick and tired of working the real then covering up the pool..
Never put it back on the pool...figured if the kids would figure out for themselves whent he water was not tooooo cold...
Bob G.
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Put it on at night only.
If it was my inground pool, I'd go for the big bucks and install a motorized cover. That's good for covering the pool in the winter and you can use it as a solar cover too.
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i don't know about the pills... but i have a blanket and it's worth every penny to me.. the reduced evaporation and increase in temps make it worth the hassle.. i have a solar heating array as well and the combination extends my swimming season by at least 3 months
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I have a 27,000 gallon pool and I am using solar pills in addition to heating with 24x12 feet of solar panels (about 40% of the area of the pool surface, less than the 50% or more recommended) and without the I feel that the solar panels heat about 8-10 degrees more than pools around here without a heater, and with the pill it's another 3-5 degrees according to my very unscientific tests. I hope to do some real accurate tests, as each day is a little different and I could have been using the pill on a hotter day. Hmmmm, time for two buckets of water, one with a cc of drops from the pill and one without. But I can say that the pill is inexpensive ($10 or so retail at beginning of season) and very convenient, no blank to mess with. I would strongly recommend the solar heaters though. Check out my web site that I'm creating (http://www.mypoolkit.com ) for pictures of the solar panels, they are well worth the money at about $1000 invested. If I have the heat going to my spill-over spa only, it heats up to 105 degrees in no time!
Kent
http://mypoolkit.com
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