What Are Solar Blankets?
Solar blankets are polyethylene-based sheets of bubble material that float on the surface of a swimming pool. The blanket traps the heat of the sunlight that passes through, keeping the water warm. Solar blankets can increase the temperature of pool water by 10 to 15 degrees F.
Capturing and Retaining Solar Heat
The blankets work by allowing short-wavelength solar energy to pass through to the water below. The pool water captures the heat. The heat radiated by water is composed of longer wavelengths than the heat absorbed from the sun-heated air, and the heat is radiated upward at longer wavelengths. These longer waves cannot pass through the polyethylene bubble material, and the heat remains trapped on the surface of the water and is subsequently absorbed by the water. Some solar blankets use an aluminum underside that additionally reflects the heat back into the pool water.
Solar blankets reduce pool water evaporation by up to 95 percent and chemical evaporation by up to 50 percent.
Solar Blanket Thicknesses
Solar blankets are commonly available in thicknesses of 8 mm, 12 mm and 15mm. The thicker the blanket, the better the heat retention and the more expensive the product. The thickness of the blankets relates to the "profile" or height of the air bubbles contained within the polyethylene sheets.
Solar Blanket Sizes
Most companies provide a number of ready-made solar blankets in round, oval and rectangular formats, sized to fit the majority of standard swimming pools. Custom sizes are available from some distributors at a higher cost.
Solar Blanket Operation
Solar blankets must be laid out over the entire surface of the pool. To obtain maximum benefit, the blanket should be kept on overnight and at any time the pool is not in use. Reel or roller systems make the process of rolling and unrolling the solar blankets more efficient. Solar blanket reels operate with a simple crank handle for rolling and unrolling the blanket over the pool's surface.