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Thread: Year Round Swimming in Southern California

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    Year Round Swimming in Southern California

    Greetings all....new to the Forum, but I've read some of the conversations on solar heating. Trying to find out what is the best solar choice for heating my in-ground, approx. 510 sq feet pool all year long here in Southern California. (Riverside is about 80 miles inland from the beaches of Los Angeles). It get's hot here in the summer, but nights do cool down. I am actually in the process of buying a completely new filter and pump too, so the whole package can be compatible. I DO have a solar cover which is rolled on and off....so I know that will help. But from what I've read, there are many options for solar heating, but don't know if any of them will heat it to 80-85 in the winter? Anyone out there in this climate who does heat all year with solar? From what I've read Evacuated Tubes are the best....but they are pretty much only used back east? Won't they work all the better and longer here in California then? Also read about glazed and unglazed tubing. Thanks in advance!

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    Mod Squad pooldv's Avatar
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    Re: Year Round Swimming in Southern California

    Welcome to TFP!

    Can't make specific comments for your climate. Hopefully others can fill in details. Solar heat can help a lot and if it can't keep up then it can supplement heat from a heat pump. Water is first heated in the solar panels and then the heat pump. Be sure to use a good solar controller that is compatible with your pump.

    A Pentair variable speed pump paired with a Suntouch would be a good option for controlling the pump, solar and a heat pump. I am a Pentair guy, I'm sure there are other brands that could work as well.
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    JoyfulNoise's Avatar
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    Re: Year Round Swimming in Southern California

    Quote Originally Posted by pooldv View Post
    Welcome to TFP!

    Can't make specific comments for your climate. Hopefully others can fill in details. Solar heat can help a lot and if it can't keep up then it can supplement heat from a heat pump. Water is first heated in the solar panels and then the heat pump. Be sure to use a good solar controller that is compatible with your pump.

    A Pentair variable speed pump paired with a Suntouch would be a good option for controlling the pump, solar and a heat pump. I am a Pentair guy, I'm sure there are other brands that could work as well.


    I live in Southern AZ which is probably close enough to Riverside climate-wise. I have never heard of anyone just using solar to heat in the winter. In fact, in the cold winter months, I believe you would have to shut off the solar portion of the heating system or else it will radiate heat away from your pool water if the pool water is warmer than the ambient air temperature. In my neck of the woods, most folks use solar on the margins of the swim season (March-April and Oct-Nov) to extend the swim season a bit. The only option for heating a pool in the winter months would be a gas heater and even that would really only work on a spa not a large volume pool. I heated my spa once in the dead of January but only in the late afternoon and with the cover on to keep the heat in during warm-up. After it's exposed, the water temperature noticeable dropped when the gas heater reached the set point temperature. There was a noticeable spike in my gas bill from that experiment.

    Hope that helps.
    Matt
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    borjis's Avatar
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    Re: Year Round Swimming in Southern California

    solar heating the water to 80-85 degrees in the winter?

    I'm not sure that would be possible unless you live in an area that has very warm winters.

    I know mine works best when it's at least 90 degrees and full sun. Less than 80 doesn't add much.
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    Re: Year Round Swimming in Southern California

    Here in Tucson, solar with a cover will get you a season from mid March to about Thanksgiving. December, January and February are going to require a lot more than solar. If you plan on keeping the pool up to temp at all times, and covered when not in use, I think solar coupled with a heat pump is your best option.

    I have Heliocol panels on my roof (equal to approx 80% of pool surface area) and with a cover and the solar my water was in the high 80's in mid March.
    chiefwej
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    Re: Year Round Swimming in Southern California

    As shown in Solar Panel Technology Comparisons it is NOT true that evacuated tubes are the best for pool heating even in winter. That technology is best for much larger temperature differences so for domestic hot water heating in the winter. The best technology for heating including the winter months is glazed panels. These used to be about three times as expensive as unglazed black plastic panels but these days it's more like twice as expensive (and evacuated tubes are twice the price of glazed panels).

    Even with glazed panels you will likely need to supplement heating the pool in winter with gas unless you thoroughly insulate your pool. That means a very insulating cover, but also insulated piping and even insulation around the gunite shell. So unless you had the pool built with a design for having minimal heat loss, you simply aren't going to have enough sunlight in the winter to keep the pool heated unless you have a VERY large surface area of panels. Technically, glazed panels absorb no more heat than unglazed (they actually absorb a little less) but where they are better is that they do not re-radiate their absorbed heat back to the air very much. So with colder air even with wind the glazed panels continue to operate. The problem is that in the winter there is far less sunlight.

    What is relevant in terms of heating is knowing the average day/night temperature. In July and August in Riverside, that's about 80F so even a clear bubble-type solar cover alone would easily heat the pool by itself. In June and September with the average day/night temperature being 74F and 77F respectively, a cover alone should still be OK since it can usually increase water temps by 10F, but you shouldn't expect more than 15F from a cover alone. That's where solar heating kicks in another 10-15F for a net 25-30F rise or more (in summer) depending on your panel surface area. The problem will come in the winter where December through February average roughly 56F so to get to 85F you need a 30F increase.

    Riverside, CA is at about 34N latitude so at the transition of spring to summer (late June) the sun is 34-23.5 = 10.5 from vertical so the sun's peak 1000 Watts per square meter is only cut down to 1000*cos(10.5) = 983. However, at the transition of fall to winter (late December) the sun is 34+23.5 = 57.5 from vertical so only 1000*cos(57.5) = 537 Watts per square meter. That also assumes you have a sunny day with no clouds or even haze.

    So basically to get that 30F increase during the winter, you may not only need glazed panels, but an area of them that is at least 150% of your pool's surface area. While having panels with 80% of your pool's surface area would be fine for extending the season through spring and fall, getting through winter would need more area. Even then, this assumes no clouds or haze. With cloudy days the sun's output may be only one-third or less of it's peak so for such days you'd need three times that 150% of panel area to heat with the panels on those days. So you can see how this quickly becomes impractical. Instead you would likely use gas heat during the winter. Whatever panels you have may help a bit but the bulk of your heating would come from gas.
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    Isaac-1's Avatar
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    Re: Year Round Swimming in Southern California

    The problem is not so much the temperature as it is the lack of available solar heat with the shorter days and sun so far to the south in the middle of winter. I see Riverside CA is at almost 34 degrees north, I live in Louisiana at just under 31 degrees north and while we do have our share of sub freezing weather, it is also not uncommon to have highs in the 70's here in December and January, but even with those highs solar heat on the pool does little to provide warmth as there is not enough heat energy available in the sunlight. Sure if you have a big enough solar heater it might work, but there are practical limits to such thing for most people, instead for my climate even with an indoor pool, and solar heat sized at about 70% of the pool surface I find it only heats the pool about 9 months of the year, and solar heat available drops off quickly those last couple of weeks of the season even though the average outdoor temperature only goes down by a couple of degrees.

    As to the evacuated tubes vs glazed vs unglazed solar panels go, all this depends on the different between the water temperature and the daytime air temperature. If the daytime air temperature is within about 20 degrees F of the desired pool temperature then unglazed performs the best, at greater than a 20 degrees F then glazed or evacuated tubes perform better. By contrast if daytime air temperatures are within 20 degrees F of the desired pool temperature, and you want year round solar heat, then the solution is a bigger array of unglazed panels.
    Last edited by Isaac-1; 08-10-2015 at 07:44 PM. Reason: typo
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