The sun's ability to warm the earth's surface (and brighten everyone's spirits) is well known. When the planet's orbit takes, say, Massachusetts, nearer the sun in the spring, ice melts, snowsuits get mothballed and winter covers are removed from pools. Each day between then and the summer solstice gets longer, allowing the sun more time to warm the water.
Of course, the earth's rotation plunges the pools in Plymouth and parts beyond into darkness each night, and much of the free warmth the sun provided or the heat gas-fired appliances and solar collectors added is lost through evaporation. Fortunately, pool people figured this out a long time ago and developed products to keep that heat from escaping. Among the first was the solar blanket, which was introduced to the pool market more than a generation ago, according to John Starr, vice president, Covertech, a solar blanket manufacturer in Etobicoke, Ontario. Since that time, Covertech and others in the industry have developed other products to retain heat in the pool, while at the same time inhibiting evaporation and keeping chemicals in the water. Standard solar covers have been joined by liquid blankets, introduced several years ago, and more recently by a new modular solar cover designed for thermal conservation and added safety. Even the commoditized solar blanket has Solar blankets save heat, water and chemicals undergone some improvements as manufacturers have worked on increasing their heat-drawing capacity and making them easier for consumers to handle.
Manufacturers of the different types of solar or thermal blankets may tout their products as the best way to retain heat, retard evaporation and conserve chemicals, but they'll all agree that a pool owner without any type of blanket or cover at all is foolish and wasteful.
"The Department of Energy states that evaporation accounts for about 70 to 80 percent of heat loss in a pool, and so when you can slow down that evaporation, you're essentially keeping the heat in the pool," says Grant Moonie, Heatsavr division manager for Flexible Solutions International Ltd., Victoria, British Columbia.
Basic Coverage
Traditional solar blankets mays have attracted lots of competition in the 30odd years they've been around, but they're still hard to beat at retaining heat, manufacturers say, and they're also pretty good at adding heat, as well.
"We make the bubble solar blankets, and their main purpose is a couple of things," says Brian Frost, director of marketing, GLI Pool Products, Youngstown, Ohio. "First, you want the blanket to be as clear as you can possibly get it so that the sunlight will be able to pass through it and actually heat the pool water during the day.
"Then, when you go out to a swimming pool at night you see all this steam rising, and so what the blanket does is act as a barrier to stop all of that evaporation of the water and all of that heat from escaping. It also stops the chemicals from evaporating out of the pool. So not only does it save you money on your heating bill, but it saves you water and chemicals that you would lose through evaporation."
Just how much heat the solar blanket adds to water during the day and save at night is a matter of some dispute, with estimates ranging from just under 10 degrees Fahrenheit to nearly 20 degrees.
"It's really tough to tell exactly what it's going to do, it depends on the weather," says Frost. "But typically you can get 10 to 15 degrees warmer by having a solar blanket on the swimming pool. We've done all kinds of testing on swimming pools, and how much heat gain you get and how much heat you save over an average day, an average evening. You lose a lot of heat at night if you don't have the pool cover. And if you have your pool heater going, not only are you losing heat but you're wasting energy, too."
Starr's estimates are a little lower. "I think if you can get 8 to 10 degrees you're doing extremely well," he says.
In an attempt to increase the amount of heat its blankets can add to pool water, Covertech added a twist to its standard blue bubble blankets about eight years ago.
"Thermal-Shield is a cover with a black color on the top part, and the bottom part is still blue," Starr explains. "We did some testing of the blue-black over the blue and found we can increase the water temperature quicker. The black is not completely black — it's opaque so the sun will
still go through it, but with the black pigmentations in it, the sun's attracted to it, and that's what allows the water to warm up a little quicker. So we've had great success with that product."
Customers are generally familiar with the concept that darker colors absorb more heat, Starr says, so dealers who carry the newer blankets will find few barriers to making sales. In fact, since the Thermal-Shield was introduced, sales have increased steadily to the point where they outsell Covertech's blue covers by a more than 2-to-1 ratio nationwide.
"A lot of dealers will carry both products and have a 'better-best' program, if you'd like to call it that," Starr explains, "where they have a pricepoint that they can go into the marketplace at, and then as the consumer walks in they have an opportunity to upgrade them to a better product."
GLI has also tweaked its bubble-type covers by incorporating an additive called Thermatex, which, Frost explains, is designed to intensify the sun's rays.
"It acts like a magnifying glass," he says. "You know, when you hold a magnifying glass over a leaf, for example, you can actually burn the leaf. Thermatex works much the same way. So a blanket with Thermatex definitely heats a pool better than one without it."
Fishing For Sales
The effectiveness of bubble-type solar blankets is undeniable, but of course they're only effective when they're covering the pool. But what about those times when the cover's off. About 15 years ago, Flexible Solutions introduced the liquid solar blanket. Originally named the Tropical Fish but now rebranded as Ecosavr, it was designed to conserve heat, water and chemicals by changing the water's evaporative properties, and to remain on the water day and night. Dispensed through a plastic fish that sinks to the bottom of a pool and slowly drips the product over the period of a month, the product has gained wide acceptance in a relatively short time. But how does it work?
"The molecules of the active ingredient are lighter than water, so they'll always want to float on the surface area," says Flexible Solutions' Moonie. "They're not attracted to each other so they don't want to stand on top of each other, so they don't stack up, but they always want to be holding on to each other, so they'll always connect and form a layer, if you will. So the product won't really build up in the corner of the pool, it'll always automatically want to spread out and form and create that layer by reaching out across the whole surface area.
"The molecular layer is transparent; you don't notice it when it's in the pool, and it allows solar gain to enter the pool. Solar gain from the sun will heat the pool water, but what we do is stop that energy gain from leaving. We can slow down evaporation by 30 to 40 percent, sometimes up to 50 percent, depending on variables like weather, temperature and that kind of thing. If you don't heat your pool, your main benefit is going to be reduced heat loss overnight, because a lot of people who don't heat their pools experience a drop in heat overnight when the air temperature goes down. So we can reduce that heat loss by around 50 percent, so if you're losing 10 degrees overnight, that can be reduced to 5 degrees. Moonie grants that liquid solar blankets are a little more difficult for consumers to conceptualize than their more-visible counterparts. After all, if you can't see them…
"There is a definite learning curve with the product," Moonie says. "The person selling it needs to understand how the product works. Often the people selling it off the shelf don't know — they're not chemists — so they do need to have the product explained to them, and there are some simple explanations that I give to people that let them wrap their heads around how it works. I'll tell them that similar to how a car may leak oil and leave a thin film on a puddle, you can see that over the surface of the water. This product works very similarly only the layer that it's creating is biodegradable, transparent and totally safe for human interaction. It won't affect your pool chemicals, it's pH neutral and it's biodegradable."
Once customers understand a little of the chemistry behind the product, dealers can emphasize the fact that, unlike a bubble-type blanket, it's always on the pool, says Stephen Shulman, creative director for SmartPool, a Lakewood, N.J., manufacturer that makes a liquid blanket called SolarPill that's placed in a pool's skimmer.
"Basically there's always a hassle involved with having to put the regular solar blanket on top of the pool, then taking it off anytime you want to go swimming, then putting in back on," he says. "There's none of that. Plus, the cost is minimal with the SolarPill. It lasts up to two months, depending on the size of the pool, so those are a couple of advantages. SolarPill is available in two sizes: one for a 12,000-gallon pool and one for a 30,000-gallon pool, basically for your typical above-ground pool and your typical in-ground pool. If you buy the 30,000-gallon pool version and your pool is 15,000 gallons, it'll just last longer."
Shulman explains that the SolarPill's design keeps it out of the way of robotic cleaners, which he says can interfere with the liquid blankets that sit on the pool's floor. And, he adds, the liquid evaporation barrier it provides is most effective when the surface of the pool is calm.
"It works best when there's no disturbance in the pool, so when people are swimming in it it's not really working to optimum effect," he says. "But when people get out and it calms down, then it's working again and will continue to inhibit evaporation and heat loss."
In addition to the bubble-type blankets and the newer liquid blankets, there's another new player in the thermal-retention game. Solar Sun Rings, a Temecula, Calif.-based manufacturer, introduced it namesake product at the AQUA Show in 2004.
The cover is actually a series of 5-footdiameter rings linked magnetically to form a thermal barrier and to allow thermal gain through the spaces between the rings. An added benefit the company touts is that it won't entangle someone who accidentally falls on it.
"It was the idea of Richard Rosene, who'd been a pool man for approximately 20 years working running a large number of residential and commercial pools," says David Bartoli, business manager. "He and I realized that there was a point at which if the blanket was in small enough pieces, it was incapable of entrapping swimmers.
"Just about everybody with small children is looking at it primarily as a safety product. Most other people are buying it for the performance and for the ease of taking in on and off the pool. With the magnets, they're just strong enough to where if you pull slowly you can take every one off the pool from one spot with one person."
Something's Better Than Nothing
No matter what type of cover customers choose, manufacturers reiterate that it's important to have at least some barrier between the air and water. A combination of liquid and solid covers may even be the best way to go, according to Starr.
"My opinion is that they go hand in hand," he says. "There was a belief that solar blanket sales would drop off because of the fish (and other liquid blankets) coming into the marketplace, but in fact it hasn't. It's actually increased. If there's any breakage of the water plane, the liquid is dispersed. So I think people are using both. But again, any concept that retains the heat is going to be looked at favorably, and anything that gives them options to sell to the consumer is a good thing. Let the consumer decide what's best at the end of the day. We're all trying to make a product that will do the consumer some good."
