Energy derived from the sun drives and sustains life on earth. So why can’t it heat your pool?

Aaaannnnd ACTION! Tangible effects of the sun's energy.

Welcome

Swimming Pools... your skin tingles in anticipation of diving in clear cool water on those ridiculously-roastingly hot summer days. This precise moment of contact makes all the hassle of cleaning and care of your pool worth it, does it not? Now if only the scorching days lingered a bit longer so you could get more use out of your pool. Alas, the seasons don't listen to you, and inevitably fall, winter and spring attack your precious pool, chilling it to its bones, making it completely unusable to you. Much of the year your pool sits, unused and unloved, like a dog eagerly awaiting the return of its owner, like a dormant daffodil bulb waiting for the snow to melt, like a Christian awaiting the Second Coming. Just as surely as weren't sent to Earth to suffer, surely we can all get what we want. And if for you that includes a heated pool without the astronomical expenses involved with Energy Companies, then welcome to the wide world of solar hot water systems.

The Way it Works

You may be familiar with solar domestic hot water systems- they take a small amount of water and raise the temperature to about 140° F. Solar pool heaters differ in that they have to heat up thousands of gallons of water to only about 80° F. [1] The most cost-effective use of solar energy today is to heat swimming pools- they require low temperature heat which is where solar collectors are most efficient. Each time the water passes through the solar collectors it is heated 2-5°. A properly sized solar system can raise the pool temperature 10-20° and maintain a comfortable swimming temperature. [2]

These systems make life more enjoyable for its owners by taking the water, circulating it through the collectors to heat it up, then sending it back for warm pool deliciousness. [3] It is important that the water be filtered before it is sent through the collectors to avoid clogging the system with debris. System controllers can be installed that will sense when the collectors are warmer than the pool and thus available to endow their heat on the water. If desired and/or necessary, pool owners may choose to install a conventional pool heating system to extend the swimming season and regulate the pool temperature.[4] The diagram below from the EERE website helps out the visual learners:

Example of a solar pool heating system from the EERE[4].

Size

Solar hot water systems can be installed to provide 100% of the pool heating needs. The size of the solar hot water system depends on many factors: the length of the desired swimming season, the desired pool temperature, solar insolation, wind factors, average temperatures of the region, and collector orientation and angle to name a few. [2] Generally, the collectors should be about 50-100% of the surface area of the pool. [5] Cooler and cloudier areas need to increase the ratio between the collector and pool surface area. Comfortable swimming pool water temperatures are usually between 78° F and °80 F in the summer and 76° F in the winter. [6]

For an in-depth study on system size, free worksheets are provided by Canadian taxpayers, available through RETScreen International Clean Energy Decision Support Centre. Use it as a decision support tool to evaluate the energy production and savings, life-cycle costs, emission reductions, financial viability and risk for the different types of solar hot water collectors.

Costs

Compared to the price of propane, fossil fuels and natural gas, solar hot water systems are often the most economical way to heat a pool. There is an initial investment for installing the system, and after that, the sunshine is free. They require very little maintenance and annual operating costs are low. On average, the initial price for these systems are between $3,000 and $5,000 and can be paid back between 1.5 and 7 years depending on the price of the fuel the system is replacing. The actual cost and the payback depends on the site, the type of system chosen, the difficulty of installation,and the length of the pool season. [5] If your pool pump is modern and properly sized for filtration and skimmer action then you most likely won't have to buy a new pump to get the water up to and through the collectors. The extra lift to the roof is balanced by the return head in a closed system. But if the pump isn’t large enough, a booster pump will have to be added to the system and to your expense list. [2]

Collector Orientation and Positioning

If you embody the classic characteristics of nortocentrism, then optimally your collector will be facing due south. If you are in the northern hemisphere, and this direction is impossible to take advantage of, you may be comforted to know that recent studies have shown that, depending on the location and collector tilt, the collector can face up to 90º east or west of true south without significantly decreasing its performance.[5]

If your pool is a summertime kind of gal, then the general rule of thumb is to tilt the collector at the latitude of the area minus 10-15 degrees to obtain maximum sunlight exposure. For winter only heating, use latitude plus 10-15°. [2]If she's a year round pool install it at latitude- that is unless you’re feelin’ extra nifty. If the latter is the case then one possibility is to build frames that can be adjusted seasonally either manually or mechanically. (Bonus nifty points given if you make it remote control.) [1]

The collectors should be installed as close to the pool as possible to avoid heat loss as the water travels through the pipes. In the quest for the holy grail of aesthetically pleasing solar hot water systems, most people prefer to mount their collectors flush with the slope of the roof. "Standoff" mounting to optimum tilt from a sloped roof usually will increase performance only 2 to 8 percent and is hardly worth the effort. [7] Other things to consider when positioning your collector include local weather conditions (foggy mornings? cloudy afternoons?), and anything that may cast a shadow across your system like trees, buildings, etc.

  • Flat roofs…

Rev2.jpg [1]

Materials

As you may have already suspected, solar collectors can be made out of a variety of materials. Collectors used only when temperatures are above freezing are easiest on the pocketbook- they can be made of less expensive materials such as thermoplastic rubber or polypropylene. Collectors that operate in colder climates on a year around basis dig much deeper into the wallet- they generally have copper absorber plates with low iron tempered glass as a covering. [2] PROBLEMS WITH COPPER PIPES

The Absolute Necessity of POOL COVERS

Tell me this- do you heat your house in the winter with the doors and windows open? Didn't think so. So why would you heat your pool and not put a cover on it when it's not in use? A question that confounds the world's current geniuses. Heat has that natural inborn tendency to rise… up and out of your hard-earned, lukewarm-treasured pool. Covering your pool when it’s not being used is the single smartest thing you can do to reduce your pool heating costs. Of all the dangers to your warm pool, evaporation proudly positions itself as warm-pool enemy #1: the greatest heat loss to your pool occurs at the surface due to evaporation. It takes only 1 Btu to heat one pound of water one degree Fahrenheit. But each pound of 80 degree F water that evaporates smuggles 1,048 Btu's out of the pool’s trust fund account, so lovingly deposited by Rich Daddy Sun. [5]

Depending on materials and the number of hours of use, temperature increases of 5°F to 10°F may be expected from a pool cover. A 5°F increase is reasonable when the cover is used 12 hours a day; 10°F when it is used 20 hours a day. [7]

Depending on care in handling and storage they will last between 3-5 years. They keep the pool clean, thereby lowering the cost of chemicals and filter maintenance. They are the surest and cheapest way of extending your swimming season. [7] Just use it. Need I say more? File:AEFprevf.jpg

Maintenance

Q: What about maintenance? A properly installed solar pool heating system should require very little, or no maintenance. However, regular maintenance of the pool and its filtration system is crucial. Pool pH and chlorine levels must be maintained within the limits specified by the pool water test kits. Chemicals should be added to the pool water far from the collector intake pipes. The filter should be cleaned as frequently as recommended by the manufacturer to ensure that adequate flow is supplied to the collectors. Check the solar heating system for proper operation at the beginning of each swimming season, particularly if it has an automatic control. Remember, a properly operating solar collector feels cool to the touch. The temperature rise of the water going through the collectors should be from 3°F to 5°F for most efficient operation. [2]

Fragments

http://www.canren.gc.ca/prod_serv/index.asp?CaId=142&PgId=763 http://www.house-energy.com/Pools/Solar-Pools-Technology.htm

Reference

  1. 1.0 1.1 http://go-solar.org/category/solar-heater/ Cite error: Invalid <ref> tag; name "Go Solar" defined multiple times with different content
  2. 2.0 2.1 2.2 2.3 2.4 http://www.p2pays.org/ref/13/12110.pdf
  3. http://www.rerc-vt.org/solarbasics.htm#POOL
  4. 4.0 4.1 http://www.eere.energy.gov/consumer/your_home/water_heating/index.cfm/mytopic=13230
  5. 5.0 5.1 5.2 5.3 http://www.eere.energy.gov/consumer/your_home/water_heating/index.cfm/mytopic=13250 Cite error: Invalid <ref> tag; name "EERE" defined multiple times with different content Cite error: Invalid <ref> tag; name "EERE" defined multiple times with different content Cite error: Invalid <ref> tag; name "EERE" defined multiple times with different content
  6. http://www.fsec.ucf.edu/en/consumer/solar_hot_water/pools/sizing.htm
  7. 7.0 7.1 7.2 http://www.fsec.ucf.edu/en/consumer/solar_hot_water/pools/q_and_a/index.htm
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