Pool Info: Solar Pool Heaters
Why Solar Heating?
The best thing about solar heating is that it is free pool heat. After the initial investment, there will be no additional cost for your heat. Free heat is hard to beat You won’t get the quick temperature rise you would get from a gas heater, but solar pool heaters will raise the water temperature 10-20 degrees or more. The response you get from your pool solar heating system will depend on your geographical area, the weather, the location of the panels, whether the pool is covered and the most importantly, having enough solar panels, or surface area, to match your desired water temperature.
According to the United States Dept. of Energy, solar pool heating is the most cost effective use of solar energy. Also, there are no expensive parts to replace, no pilots to light, no electronic components. And best of all, no expensive fossil fuels to burn, and no dangerous and noxious fumes exhausting.
How does Solar Pool Heating Work?
Solar pool heating systems usually have four basic components. The pump, solar collectors and a control valve and check valve. The pump pulls the water from the swimming pool or spa and pushes it through the filter. The water travels from the pool filter to a 3-way flow control valve. The valve regulates how much water goes to the collector panels. A rather slow rate of flow is usually best, to absorb the heat most efficiently, without over-cooling the panels. Experimentation with the 3-way valve and a pool thermometer will allow one to dial-in the best flow rate for any solar heating system.
The solar panels are made of small black tubes, of rubber or polypropylene usually, which absorb the heat from the sun and warm air, and transfer it into the water as it passes through. After the pool water is pushed through the panels, a pipe carries water from the roof or rack back to where it reconnects into the pool return line, via a Tee fitting. A check valve, or one-way flow valve, installed on the solar return pipe prevents water from traveling backwards up into the solar system.
Solar heaters can also be used in conjunction with a conventional swimming pool heater, lowering heating costs by 50%-70%. Using a solar blanket will double the efficiency of your solar pool heating system.
Solar heaters can also be used to cool a pool or spa in certain geographical areas. If the pool is too warm, the solar system can be set to run during the night hours, and off during the daylight hours.
A solar controller device is recommended to automatically control the 3-way valve operation, sending water to the solar panels only when conditions are optimal for heating. Solar controllers allow you to set a thermostat, or select a temperature for your pool. An automatic valve turner called a valve actuator will turn the valve to send water to the solar panels, often enough to maintain the selected temperature. It does this with the help of two temperature sensors, one mounted next to the solar panels reads air temperature, and another sensor is clamped into a hole in pool pipe, to read water temperature.
How well do Solar Pool Heaters work?
Solar heaters heat best during sunny weather and warm temperatures of course, and they don’t heat at all at night, or during rainy days. Solar pool heaters work well in all parts of the United States, but lose most of their effectiveness during winter. A properly sized and oriented solar system, with at least 6 hours of direct sun, can be expected to add 10-20 degrees during any month of your swimming season, and add several weeks onto each end of the season. Oversized systems, where space permits, will provide even greater heat to the pool.
What does the Ideal Solar Pool Heater System look like?
A southern facing single story roof that’s at least 20’ long, with unobstructed sun, for at least 6 hours daily would be best. Even better if it is close to the pool pump and filter, so that long plumbing runs aren’t required. Another good location would be a free standing, triangular shaped rack, built of slotted angle bracing or lumber framing with a plywood deck. These can be placed up against a fence, on the sunny side.
Remember that the sun is always moving across the sky as our seasons change. A large tree that doesn’t block the sun during May could be a real shade tree in September. Also you need enough solar panel surface area to make a reasonable difference. An undersized solar system will only produce 5-10 degrees of heat.
How many solar panels are needed?
The more panels you have, the more heat you can harvest. Swimming pools in ideal solar conditions should use at least 50% of the pool surface area, For example, an 18x36’ pool has a surface area of 648 square feet. 50% of that would be 324 feet of solar panel surface area, or about 4 of the 4’x20’ panels, which are 80 sq ft each. In less than ideal conditions, such as an east/west orientation, or partial sun obstruction from trees or houses, a higher multiplier of 70-80% can be used, to compensate for panels that receive less direct continuous sun.
Can solar panels be installed on separate roofs?
Yes, you can install separate sets of panels, in series, on different facing roof sections for instance. The water will run through the first panel set, exit and then enter the second set of panels. This is used when the roofline is small or is not facing due south.
Do I need a booster pump?
No, most solar systems operate just fine on the volume of water pushed from the existing filter pump. Even installing panels on a second story roof is no problem for most inground pool pumps. There are instances where a larger filter pump or booster pumps are recommended, but these are not the norm.
Installing a Solar Pool Heater System
Not too difficult to do, most in ground pool solar heaters can be installed in one day. Above ground solar heaters can be installed in less than an hour. Location is most important, so after figuring out if you will install on a roof, fence or deck, the panels can be installed. A southern orientation is best in the US, and installing at a 45 degree angle will absorb more heat. The solar panels can be roof mounted in a few hours, secured to protect them from winds. Then you connect plumbing from the return line, after the filter, to the panels on the roof, securing vertical pipes to the wall. The final step is usually wall mounting the solar controller and installing the temperature sensors.
Care and Maintenance of a Solar Pool Heating System
Solar heating systems require very little maintenance. It is important to keep your pool water balanced and your filter in good operating condition. Since the water that goes into the solar collector comes straight from the filter, if there is anything that bypasses the filter, it can potentially clog the solar collector.
Improper pH and calcium hardness can cause mineral build up in the solar collectors. Low pH or high levels of chlorine can cause the plastic to become brittle. If you have very high calcium hardness levels in your pool, use a scale inhibitor on a regular basis to prevent mineral build up in the solar collector.
Although rare, splits or damage to the tubes in a roof mounted solar pool heater can be repaired with an inserted plastic sleeve. This works similar to a stint placed in a blocked artery. One of the greatest things about solar pool heaters is their reliability, and simple design.
How long do solar pool heaters last?
Ironically, the summer sun will eventually attack a solar pool heater, causing it to become brittle and breakdown. Most polypropylene solar heater panels will last at least 10 years in the hottest parts of the country, and longer in the more temperate regions. More durable solar panels made of rubber can last 20 years or more before the material begins to weaken.
Winterizing a Solar Heating System
Most solar heating systems have drain plugs to allow the water to drain out of the panels. They are often installed at a slight tilting angle to facilitate drain down. For proper winterization, it’s a good idea to blow air through the collector to remove any trapped water in the panels or on top of a vertically mounted check valve. Winterizing is also a good opportunity to inspect the collector panel for damage and inspect the mountings; to be sure the solar panels are secure and ready for the winter.