It Makes Your Cold Pool Warm
SolarCraft’s solar pool heating systems work seamlessly and are fully automated. You set the desired water temperature on the digital control panel and let your pool’s filter pump do the rest. The solar heater only runs during the hours of operation of the pool’s filtering. Once the heat sensor on the solar panels senses a higher heat than the pool water an automatic motorized valve diverts the water through the solar panels and carries the suns heat back to the pool. This process is continued until either the pool’s filter pump shuts off or the desired pool temperature is reached. During certain months of the year we have had reports from our customers of mid 90 degree temperatures. It is that simple.
The quality of SolarCraft systems starts to show in the solar panel’s unmatched ability to transfer about 85% – 90% of the sun's energy into the pool. The solar panels were tested by FSEC to put out 1063 BTUs per sq ft, per day (the industry's highest). That amount of energy will heat 1 pound of water, or 1 pint of water to 1063 degrees Fahrenheit! Of course, the amount of water traveling through the system will not allow such extreme temperatures and these temperatures are measured per day, but it can give you an idea of the power of the sun's energy and the ability for FAFCO products to capture it.
With the combination of performance and quality of our products and our great service, you will not need to remember these facts because you will not need to service this system yourself.
Types of Systems
Solar pool heating systems come in many sizes and styles. Over the years all manner of different configurations and materials have been tried in delivering the sun's energy into a swimming pool. In the early to mid 70's copper collectors were used. They proved to not only be costly but, because of the radical nature of a swimming pool's chemistry they corroded quickly and the copper oxide deposits then stained the pool. Also used were pipe systems using 1" to 1-1/2 " pipe. These proved to be heavy and over time very unsightly. During this period the modern co-polymer or polypropylene absorbers were being developed. This technology in essence was a quantum leap in terms of heat production, durability, weight, and esthetic appeal. Systems have also been developed using EPDM rubber, but due to suffering from oxidation from the ultraviolet wavelength of the sun's energy and the same effect internally from chlorine, they are not as common as the plastic family of pool panels in widespread use today.
The evolution of the designs are an obvious attempt to create more heat with less weight, greater strength, and more heat production. The copper absorbers used a copper fin or 4" to 6" sheet of copper with a copper tube soldered to the fin. The heat striking the fin would then be conducted to water inside the tube completing the collection process. The pipe systems were at an obvious disadvantage in that only the top section of water in the tube would receive any heating effect and the rest of the volumetric capacity was wasted.
Due south is the optimal orientation, but modifiers can be used if the array is facing to the East or West of due south. The examples here are for pool heating panels as the angle of incidence is not as critical as the glass covered solar water heating panels which reflect incoming energy as the angle increases. These modifiers are used for the Central Florida area and may be different for other areas of the country or different climatic circumstances.
The number one rule is to never design or install a solar pool heating system that faces in any portion of the 180 degree arc of the compass that faces north. When you need it the most it won't work. Needless to say installing solar panels in the shade of a tree or building will also not be functional.
For pool heating panels any mounting area within a 45 degree arc from due south is acceptable. After that multipliers should be used to increase the collector area as performance decreases due to an orientation away from south.
DHW (Domestic Hot Water) panels should be placed as close to due south as possible because of the reflective nature of the glass used to glaze or cover the absorber surface. This cover is used to create higher temperatures in the panel for production of household water in the 120-160 Deg. range
A solar pool heating system can be operated by simply using a 3-way valve. The system is either on or off. Although this simple method is bullet proof, in other words...no service, it has some rather severe drawbacks, the first problem being one of performance. If there is flow through the panels in cold, rainy or otherwise inclement weather not only is the system not producing any heat, it can actually cool the pool. The net result may be a pool that is actually colder than the one next door due excessive heat loss.
The next dilemma is one of comfort. During many months the system produces more daily heat input to the pool than is actually needed and this may result in a pool that is too warm. Although this may seem to a cold pool owner as a not so terrible problem, diving into a 95 Deg. F. pool may not be desirable either.
The use of an automatic control system fully automates the solar heating system by using a microprocessor based differential control, sensors on the roof and in the pool water, and a motorized valve to direct the flow of the water.
When the control detects via a 10,000 ohm thermister on the roof that the temperature is 5-10 deg. warmer than the same type of sensor in the pool plumbing is reading , then the control activates the motor drive, turning the valve to the "Solar On" position.
Once the desired temperature is reached or the roof temperature falls below the pool temperature then the solar is turned off by rotating the valve to the "Solar Off" position. All of the solar pool systems that SolarCraft sells include an automatic control system.
Physics of Pool Temperature
A pool loses heat at night or in inclement weather at a quantifiable rate, this rate is then used to determine the amount and type of heat needed to keep a pool at a given temperature.
Swimming pool heat loss occurs primarily at the surface where the evaporation of water accounts for this loss. This is the reason for the tremendous net effect of a pool cover.
In-ground pools lose only about 10% of the total losses through the wall of the pool into the ground or through the lines removing and returning water to the pool in the normal course of daily filtration cycles.
Pool covers reduce most if not all of the evaporative losses from the pool when in use. With this component of heat loss being 70% a cover with a small R value can achieve as much as a 75% reduction in heating costs when used.
Swimming pools gain heat naturally during the day by absorbing the infrared radiation from the sun. An open pool gains almost twice the amount of the sun's energy than a screened pool due to the blocking effect of the screen enclosure, very similar to an umbrella with holes in it. The net result in the Central Florida area is a pool that is 6-8 Deg. F. warmer than it's screened counterpart.
Solar pool heating systems can be sized to gain anywhere from as little as 4 Deg. F up to as much as 16 Deg. F before cost effectiveness becomes an area of concern. The dilemma being that sizing for extreme conditions when the sun's energy is relatively weak and the outside ambient air temperatures are low means that the collector area required becomes cost prohibitive. On a 58 Deg. F. day swimming may not even be desirable, or said differently even if the pool is warm- is anyone in their bathing suit.
Since 70% of all heat loss from a swimming pool is evaporative and convective a simple vapor barrier with an added R value such as a pool cover can cut almost all of these losses.
The Effects of Pool Covers
The net result is a savings of 65-70 % in heating costs or a much greater net gain in energy when using a solar pool heating system. Although these covers are relatively lightweight, a simple device such as a winder or deck reel for removing the cover can make the usage of a cover far easier.