Do I need a solar cover

[chem geek]

A mostly clear solar cover will let the sunlight enter the pool and heat the water during the day. Without any solar cover, a white plaster pool has the water absorb around 60% of the sun's energy; a dark surfaced pool absorbs over 90%. I'm not sure how much gets through a clear solar cover, but it's probably substantial. Technical details about this are in this thread.

So a clear solar cover can allow the sun to heat the pool while preventing heat loss from evaporation (and reducing that from conduction/convection as well if the cover is well insulated). So one can get a net temperature rise in the pool and maintain it just by using a solar cover. The downside is that the UV from sunlight still gets through so the clear cover does not substantially cut down chlorine consumption.

If one uses a darker cover, such as a blue one or a mostly opaque darker cover, then this cuts down the chlorine loss from sunlight, but also prevents some or all of the light from getting into the pool to warm it. If the cover is insulating, then the heat of the cover won't get into the pool very much. So such covers are better at retaining heat and reducing chlorine consumption, but not as good at raising the temperature of the pool water.

If one uses a thinner less-insulating dark cover, such as with an electric safety cover, then the heat from the sun heats the cover and some of this gets transferred to the water in the pool to heat it, especially when the pump is running to circulate the water under the cover. We just switched from a light tan electric safety cover to a dark blue one and noticed the extra heating of the pool right away so that the solar system shuts off much earlier now.

If one lives in a very hot climate where one does not want the extra heating in the pool, then using a thin white or reflective cover will prevent heating during the day while removing the cover at night can allow for some evaporative cooling.

Richard

[Poconos]

Some good info Richard, Thanks. One question....what is an 'electric safety cover'? Couldn't find anything related to pool covers that made sense by googling it.
Al

[CarlD]

I don't know much about electric safety covers other than that they are covers that deploy at the touch of a switch.

We just came home from a 5-day jaunt to Banff for a friend's wedding. (It rained most of the time). I left my solar panels turned off, but my solar cover on--today the pool was 96 degrees! That's in North-Central New Jersey, with a 20,000 gallon pool, using a cheaper blue cover. It had been in the mid-80's when we left.

Covers insulate AND prevent evaporation-based heat loss.

[steveinaz]

Though I live in southern Arizona, neglecting to put my solar cover on at night will lead to a loss of anywhere from 2-4 degress the next day. Probably a combo of extremely low humidity and cool evenings regardless of high day time temps. As an example, we've been averaging about 97 degree day time temps, but evenings/over night temps are around 68-70 degrees.

My solar cover has been on since 1 February; it took until about 15 June to get the temp to 82 in the pool. Since about 23 June, it's been 85-87 consistently everyday by 2pm. A friend of mine with a similar pool uses no cover, his water is at 78-80 right now...