Solar Collectors vs Solar Panels

[mas985]

I have a solar cover and it never reached 83F w/o solar. 80F was the highest it got and that was in late July. It would only be about 68-70 on June 1st.

The solar cover temps do depend somewhat on the type of cover. I was a assuming a clear blue bubble cover. But remember too that the temps I am showing assume at least a week of cloudless days. I am not sure that happens in your area. A cold cloudy day can reduce pool temps by quite a bit.

So are you saying then that even if I didn't go Solar and went with a heat pump heater - which maxes out at about 140k btu, that it wouldn't help at all?
I mean I already bought the parts so I can just keep it for space heating only; but its kind of discouraging to find out that I really have no options to get my pool heated. Even if I combined the 140k btu from a heat pump heater and the 200k btu from the solar panels it sounds like it would barely make a dent. Is that right?

A 140k BTU heat pump generates 140k BTU/hr so it can add 3,360,000 BTU per day which is 174x that which your panels can provide. To match your panel output, you would only need to run the HP slightly over an hour. With a 90F setpoint and with a cover, you would need only about 3 hours of run time. But you need to run it every day to top off the heat that is lost.

 

[Yinn]

The solar cover temps do depend somewhat on the type of cover. I was a assuming a clear blue bubble cover. But remember too that the temps I am showing assume at least a week of cloudless days. I am not sure that happens in your area. A cold cloudy day can reduce pool temps by quite a bit.

A 140k BTU heat pump generates 140k BTU/hr so it can add 3,360,000 BTU per day which is 174x that which your panels can provide. To match your panel output, you would only need to run the HP slightly over an hour. With a 90F setpoint and with a cover, you would need only about 3 hours of run time. But you need to run it every day to top off the heat that is lost.

Thanks for clarifying. So taking the Raypak 8450ti for example, it uses 42A @ 230V and generates 129,000 btu/hr on the low end. So it would take roughly 9.66kwh for 129,000 btu.

Going along those lines. To run it for the equivalent 200,000 btu/day would consume 14.98kwh. Using a mid-grade solar panel (300W) at a .85 derating factor. 10 solar electric panels would generate 14.03kwh/day for me. So the cost to operate is about the same. But the overhead costs (heater + solar panels + inverter) would be significantly more - but it’d be able to meet my demands without any issues.

In all three options I’ll still have a space issue regardless of whether I go solar electric, Solar thermal, or solar pool heating. I’ll put these up first since I already purchased and see what happens. If it doesn’t make a dent I’ll have buy a heater to supplement and install more solar electric. Guess I’ll start keeping an eye out for surplus inverters..

Edit: I just realized, if my pool needs as much heat as we’re estimating. This is going to get really expensive if I don’t go solar. 200k BTU from a heat pump at 15kwh/day would already be $70/mo. If I needed the 40-600k btu/day, we’re looking at $140-210/month to heat the pool. Ouch.

 

[mas985]

It looks like the average overcast for your area is close to 50% when you want the most heat. Are you sure that solar is the best option?

Newark Climate, Weather By Month, Average Temperature (New Jersey, United States) - Weather Spark

In Newark, the summers are warm, humid, and wet; the winters are very cold and snowy; and it is partly cloudy year round. Over the course of the year, the temperature typically varies from 26°F to 86°F and is rarely below 12°F or above 94°F.

weatherspark.com

 

[Yinn]

It looks like the average overcast for your area is close to 50% when you want the most heat. Are you sure that solar is the best option?

Newark Climate, Weather By Month, Average Temperature (New Jersey, United States) - Weather Spark

In Newark, the summers are warm, humid, and wet; the winters are very cold and snowy; and it is partly cloudy year round. Over the course of the year, the temperature typically varies from 26°F to 86°F and is rarely below 12°F or above 94°F.

weatherspark.com

I think you’re considering efficiency when I’m considering mainly cost.

My 10kW solar electric system is only about 12% efficient at the panels. Then loses another 10-15% in transmission. In an area that’s 50% cloudy with less than 6 hours of full sun at peak, it doesn’t make sense on paper.

Long story short, my 10kW current solar electric system makes enough to cover all of my electric bill, plus thanks to state incentives I get a check for an additional $3,000 a year.

Inefficient but cost effective. My break even on that system was 4 years And it’s been income after that. So yes, positive I want solar.

 

[mas985]

Sorry, I meant pool solar not PV.

 

[Yinn]

Sorry, I meant pool solar not PV.

It’s worth a try. My existing hot water system cost $2000 to set up for two panels, and it generates enough hot water for a family of 4 all year round and dumps excess heat to space heating in the winter. Break even on that was just about 3 years.

This was even better at $1250 for 10 panels. At 200k btu/day, that’s $70/mo or $840/year of electricity saved. I’d break even in about 2 years. Even if I only generated half of that I’d break even on the system in 4 years. The question will be if it’s enough BTUs to heat the pool. (Doubtful based on what you said)

Worst case, I’ll have to buy a heat pump in addition to this and I’ll use this to supplement in the summer, and switch it to space heating in the winter.