Do I need a solar cover

[Spensar]

[QUOTE=Poconos;64779]

Otherwise, they don't do much for the pool temperature in a moderate or northern climate.

Spensar,

I don't know what you consider a moderate or northern climate but I can assure anyone that here in the northeast they do make a big difference as those tables in the links will confirm. Nights are usually quite cooler than the water and they do help retain any heat you gain during the day. Heat is heat whether it is obtained naturally from just the sun on the pool or by fossil fuel or heat pump. Am I missing something?

Al

True, heat is heat. If you have a hot day and the water heat's up, the cover will help keep the heat in.

I think it is fair to give people a heads up that a solar cover by itself will not do a lot to increase the temperature of the pool water. It's greatest utility is in keeping the heat in, not generating it. This especially applies if there is a big difference between the water and air temperature like when you are heating the pool. To many people by it thinking it is some kind of solar heat that will do wonders for their pool temperature, and are very dissapointed afterwards with the modest impact. Most people around here don't bother with it after a while, unless they are heating. I'm in Ottawa, Ontario.

[cleancloths]

Heat loss due to evaporation is the biggest heat loss of a pool, an order of magnitude greater than convective losses. I live in NJ and keep the solar cover on whenever we are not using the pool - it makes a huge difference. I run my heatpump to initially raise the temperature in the early spring - that is it. I have two solar mats that are 2' by 20' each, and between them and the cover my pool stays at 80-85 degrees all the time.

[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...