Solar Blankets Explained

by Pool Builders on 11-13-2007 in Articles

Solar Blankets for swimming pools are standard equipment for many pool owners. Pioneered in the 1970's, solar blankets caught on fast and are staple of the retail and wholesale pool trade. Just what goes into a solar blanket and why are they popular when they don't last very long? This article will address these fascinating issues!

Solar blankets are essentially extruded polyethylene film. They are essentially an uprated version of the packing bubble that kids (and some adults) love to pop. The manufacturing process is relatively simple. Plastic resin pellets are heated to the melting point in an extruder. The hot plastic exits the extruder in two sheets of wide, hot film to keep the material flexible. The two sheets are passed over a rotating drum filled with holes to which heavy suction is applied. As the sheets come together under the hole filled drum the suction pulls the warm plastic into bubbles that form the familiar bubble wrap look. The finished sheets are wound onto rolls. The rolled material is heat or ultrasonically welded to make wider sections. These sections are then cut to the necessary dimensions for all the different pool sizes out there.

Solar blankets provide two important benefits: evaporation control and passive solar heating. The evaporation control is a no-brainer. Spread a sheet of floating plastic on water and it won't evaporate very fast. The passive solar concept is also simple. The bubble-trapped air is an insulator and the warm summer sun provides the heat. Solar radiation passes through the transparent solar blanket and is trapped in the pool by the insulating properties of the air bubbles. This can warm pool water to a depth of nearly one foot coupled with the evaporation control has a noticeable affect on water temperature. This sounds like a pretty good deal. Why don't solar blankets last more than a season or two?

When first introduced solar blankets were between 25-30 millimeters (mils) thick and sold for as much as .30/sq. ft. This heavy plastic treated with UV blockers allowed these early blankets to last 4-5 years and longer. Pretty good in a harsh chemical environment with damaging doses of ultra violet radiation! Unfortunately price competition drove manufacturers to continually reduce the film thickness in order to stay in the game. Today's blankets range in thickness from 4-9 mils regardless of where they are purchased. With that little material these modern blankets are nearly one-season throwaways. Some manufacturers offer heavier blankets with up to 14 mils thick at a premium price. These heavier blankets will offer better service life but are still well below the performance of the solar blankets of years ago. In the final analysis there is no way to buy a heavy solar blanket today. Today's pool owner must settle for buying a new solar blanket every season or two. Fortunately, they cost quite a bit less.

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