Solar heater or no heater at all?

[jro33176]

I've read so many threads on this topic! I would appreciate confirmation of the information I have collected so far...

At this point, I have narrowed my options to purchasing a solar bubble cover and maybe adding a solar heating system.

I put together the following information based on the format and links posted by others (Chemgeek?) on this forum.

location: Miami

	Jan	Feb	Mar	Apr	May	June	Jul	Aug	Sept	Oct	Nov	Dec
Avg High	74	76	78	81	85	87	88	89	87	84	80	76
Avg Low	55	57	59	62	68	72	73	73	73	69	63	78
Avg Rain (inches)	2.14	2.45	2.91	3.01	5.34	10.07	6.8	9.7	8.99	6.69	2.97	1.62
Solar panel tilt (Kwh/m2/day)	3.5	3.5	3.5	3.5	3.5	2.5	2.5	2.5	2.5	2.5	3.5	3.5
Gallons in Pool	Pounds	target temp	Total BTUs	FPL cost	heat pump output	hours to heat
19152	158,962	85 F	2,384,424	.09 - .11 per Kw	133,000 / 140,000	18 hrs / 17 hrs.

As I understand it:
1. With only a bubble cover, I can expect to achieve and maintain a pool temperature that is equal to the High temperature for the day. If I want to swim in 85 degree weather, I can swim from May - October. Is this correct?

2. To swim in the other months, I will need to use a heater. To calculate how long it would take to raise my water to the temperature I want, I calculated the number of BTUs I will need to raise my water 15 degrees (the greatest increase needed during the months outside my range). How does this relate to the solar panels? Do they have BTU output equivalents?

Am I on the right track here? My PB is suggesting a 140,000 BTU heat pump for ~$5,000. For solar panels, I'm told it will be roughly the same cost. Seems like solar panels would be the better option.

 

[jblizzle]

1. I am not sure about getting the water to the high temp of the day. Solar covers are generally more about heat retention (especially at night). If you do not have a lot of wind, then you will actually increase the pool temp more without a cover when the sun is shining on it. If it is a hot cloudy day, you may not be adding much in the way of heat at all and just hoping to reduce losses.

2. Solar panels (in optimum orientation and full sun) generate about 1000 BTUs per sqft per day. You need about 160k BTUs to raise the temperature by 1 degree. So if you have a 320 sqft solar array, you should add about 2 degrees per day from the panels. My pool is a little smaller and I have 500 sqft and have seen the pool rise 5 degrees in a day (that includes the solar panels and sun hitting to pool etc). Right now my solar is only running a few hours per day to maintain temp in the upper 80s.

Solar is nice because the heat is free (after install), but have realistic expectations. You are not going to get a lot of heat quickly, clouds and rain mean no heat added that day. An automatic controller is a VERY good idea so you do not cool water when a storm rolls in.

 

[Isaac-1]

Like Jason said, you must have realistic expectations of solar performance, this means you can't decide that you suddenly want a warmer pool tonight, it is much more realistic to decide you want to pool to be warmer in 3 or 4 days. The same holds true of desiring an exact temperature instead of a temperature range. Also as you noted up front cost for solar is similar to a heat pump, but operating cost will be much less, another nice benefit of solar is it can be used as a pool cooler by running at night and during rain storms during those hot summer days when your pool may be uncomfortably warm.

 

[jro33176]

Thanks for your responses. I need to read it through again to absorb this information.

For the solar bubble cover, if I only cover the pool at night, I am preventing heat loss and maintaining the temperature of the pool that is achieved during the day. With this method alone, the water will never be much warmer than the outside temperature?

With the solar panels (thank you for the BTU number!), I need to calculate the square feet of the installed panels to determine the degree of rise in temperature I can hope to achieve in any given day. For a pool with 648 SF (mine) and 500 SF of panels, I can estimate about a 5 degree rise in temperature in ideal conditions.

In contrast, with the heat pumps, I can achieve a more rapid rise in temperature, but at a greater expense. If I use the heat pump to reach my ideal temperature and then place the solar bubble cover at night, will I be able to maintain the pool temperature?

Am I understanding this correctly?

It's a good advice that I should consider how I want to use the pool. If I don't plan ahead (by 3-4 days), I won't have the pool heated to temperature I want with solar panels. Even a heat pump requires planning ahead by at least 1-2 days...

 

[Isaac-1]

Generally with solar panels you set your desired temperature and leave it there, you don't turn it down when not in use, as during marginal conditions they can take weeks to reach their desired temperature goal. Think 3 steps forward during the day then 2 steps back each night. Having said that in your climate it is possible to manage 12 moth pool operation with solar heat alone. For some good general solar advice I suggest doing some reading at http://h2otsun.com/ while it is slanted towards there products, there is still a LOT of good generic information mixed in.

Ike