Should I order solar heat?

[MrNica]

Here is the link to my build: http://www.troublefreepool.com/threads/87710-New-pool-build-in-Nicaragua

I like my water about 85 degrees. Have been getting varying answers from friends that have pools here. (Not many people have a pool).

We are at 9 degrees latitude with some windy days part of the year and a rainy season that is a lot like florida (puffy clouds and rain in the afternoon).

The weather here is nearly always high of 84-88 and low of 70.

The pool will have direct sun about 5-6 hours a day.

Will I need heat to maintain it at 85? I prefer to not mess with a solar cover. As we will use this pool a lot.

I was looking at: http://www.amazon.com/dp/B004VU98AS...UTF8&colid=24U6U1Y19NHQJ&coliid=IX1KWD8B9FX71

Is there a better product that is less "flimsy". All of these solar heaters seem to be poorly built and delicate?

The alternate could be a heat pump? (Imagining it would run very little).

I also do not wanna freeze when the pool is opened for the first time! So I prefer to not wait and see how warm the pool becomes. LOL

Might buy a cheap solar cover to start up the pool however.

Thanks for the help!

 

[JasonLion]

In your location keeping the pool nice and warm should not be a problem, at least during the summer.

 

[MrNica]

LOL All year is what you would define as summer but it can be windy and the pool is shaded part of the day.

 

[Isaac-1]

There are better panels out there, some panels are semi-rigid and are difficult to ship, others easily roll up and fit in a box to ship. Given your location you are probably better off the second type, one respected manufacturer of this type is http://h2otsun.com/ As to the question of your need for solar heat it is a hard question to answer, partly depends on your preferences, in general this ranges from about 77-95 degrees, personally I prefer my pool water around 83 degrees, which many people feel is too cool, but by comparison official Olympic competition pools are kept at 78 degrees, which I feel is on the bottom end tolerable also you must consider when you want to swim as water that would be warm enough to comfortably swim in during the evening might cool off enough over night to be too cold in the morning.

 

[chem geek]

If there were no sun hitting the pool and no water evaporation, then the pool water temperature would be roughly the average of the day/night temperature or around 78ºF (according to this link, the highest average day/night temp is in March and August at 79 while the lowest is in June at 75). As noted in the thread Water Absorption and Heating from Sunlight, in a white plaster pool of typical depth around 60% of the sun's energy is absorbed by the water in the pool. This heats the pool at noon by around 0.7ºF per hour. So over 5 hours (not all of which is directly overhead sun but I'll ignore that) this is 3.5ºF. If there were no losses, this increase would occur every day (but of course there are losses as I describe below).

Without a pool cover, evaporation will cool the pool as noted in this post where 1/4" evaporation in a 4.5 foot average depth pool cools the water by nearly 5ºF. The rate of evaporation is a function of the temperature difference between air and water, the relative humidity of the air, and the amount of wind. As noted in this paper, "Pan evaporation in a previous study at Victoria de Julio, 70 km from Rivas, was 2586 mm/yr averaged across 9 yr (van den Broek et al., 2001), which is probably comparable to pan evaporation at Rivas." So that is a pan evaporation rate of 0.28" per day. As shown in this link, relative humidity is usually between 64% and 80% so the pan evaporation amount is surprising unless there is regular wind at the water surface of 4 MPH on average. As shown in this link, this may be the case (6-9 knots is 7-10 MPH).

A solar cover would virtually eliminate evaporation so would allow the sun's heat to build up temperature of the pool water, probably by 10ºF or more so would be enough to get to your target temperature.

What this all means is that without a pool cover or without solar heating your pool is unlikely to warm up much if at all and if not protected from wind it could even be cooler than the avg. day/night temperature. Since you don't want to use a pool cover, then solar heating is certainly an option for heating the pool given the amount of sunlight you have each day even though you also get clouds part of the time in the rainy season (May-Nov) while the dry season (Dec-Apr) should have clear skies. The question will be how many panels you need. Since you only need a relatively small temperature rise to get to your 85ºF target temperature, I'm guessing that you won't need much more than 50% of your pool's surface area in solar panel area, but this really depends on whether you can shelter your pool from wind (i.e. fences or hedges or other wind breaks).