Boosting Solar Throughput

Jump to latest Follow Reply
W

Wolfmarsh

0
Jun 18, 2007
151
Charleston, SC
Hi Everyone,

In the past 2 summers, I havent really been satisfied with the way my solar heating system is working. It does bring the temperature up on warm, sunny days, but quickly loses that over night and takes all day to recover the heat.

I know a solar cover would help dramatically, since its losing the heat over night, and I plan to do that.

One other thing I was considering was adding a second pump. I currently have a 1.5 HP pump powering the filter, and have a spare 1 HP pump just laying around. The solar controller can turn on a second pump when it goes into heating mode, and I was thinking of just adding this second pump to the solar loop. The water coming out of the return when the solar is on is VERY hot, so I was thinking adding the additional pump would push more water through the heating panels and heat the water up faster (I read somewhere on here that there isnt enough water going through the system if it is more than a few degrees warmer than the water in the pool).

Does that sound like a decent thing to try? It would only really cost me the extra PVC fittings to add the pump to the system.

Thoughts?
 
That would probably work, but there might be something simpler that you could do to get the same result. A 1.5 HP pump should be more than enough to get plenty of water flowing through the solar panels. Perhaps your diverter valve isn't sending enough water to the panels. It might be something as simple as adjusting the stop on the diverter valve so it sends more water to the panels.

Do you have the system setup so that the current pump runs any time the solar controller is calling for heat? Adding a separate solar only pump makes the largest difference when there is some reason not to run the main pump the entire day.

Another question is how many panels do you have? A 1 HP pump dedicated to the panels would be too much if you only have a couple of panels.

Any additional information you can give up about your setup will help us give you better advice.
 
Your pump is already oversized for your setup, so I can't see how you could be having low flow. Does all of the pump output go through the solar? I can't run all of my 1HP pump's output through my panels
 
Before I installed a solar cover, I was loosing about 15 degrees overnight (ambient 85 in the day, 60 at night). Now I loose about 1-2 degrees. Heck, I don't even need to heat the pool, the sun does it through the cover. Pool was 85 this morning when ambient was only 82 (clear sky, sun out).
 
shakenbake said:
Before I installed a solar cover, I was loosing about 15 degrees overnight (ambient 85 in the day, 60 at night). Now I loose about 1-2 degrees. Heck, I don't even need to heat the pool, the sun does it through the cover. Pool was 85 this morning when ambient was only 82 (clear sky, sun out).
Click to expand...
Yikes! I'll bet you had a decent amount of wind or perhaps your air is very dry (very low relative humidity). Usually, evaporation wouldn't be that high to lose that much temperature overnight. I know in my own pool at similar day/night temperatures in the summer that having the cover off would lose about 6 degrees overnight while with a fairly thin mostly opaque electric automatic safety cover I lose around 3 degrees overnight. However, we generally have no wind at night (it's mostly in the afternoon). With a more insulating bubble-type cover, I estimate the loss would be more like 1-1/2 degrees by cutting down heat loss from conduction through the cover which is what you are seeing.
 
I know I could use more panels, only have 80 sq ft of them. Unfortunately I don't have any more accessible roof space without going all the way up to the top of the second story.

The panels are a good 100 ft away from the pool.

I'm surprised how low your temperature losses are. If I get the pool up to 85, it can drop into the high 60's overnight, a 15+degree drop. Our ambient temperatures are the same. It can be in the 80s during the day and in the 40s-50s at night.

My pool is above ground, so maybe that's the difference?
 
chem geek said:
shakenbake said:
Before I installed a solar cover, I was loosing about 15 degrees overnight (ambient 85 in the day, 60 at night). Now I loose about 1-2 degrees. Heck, I don't even need to heat the pool, the sun does it through the cover. Pool was 85 this morning when ambient was only 82 (clear sky, sun out).
Click to expand...
Yikes! I'll bet you had a decent amount of wind or perhaps your air is very dry (very low relative humidity). Usually, evaporation wouldn't be that high to lose that much temperature overnight. I know in my own pool at similar day/night temperatures in the summer that having the cover off would lose about 6 degrees overnight while with a fairly thin mostly opaque electric automatic safety cover I lose around 3 degrees overnight. However, we generally have no wind at night (it's mostly in the afternoon). With a more insulating bubble-type cover, I estimate the loss would be more like 1-1/2 degrees by cutting down heat loss from conduction through the cover which is what you are seeing.
Click to expand...

It's been super windy here in austin for the last month or so.
 
Wolfmarsh said:
I know I could use more panels, only have 80 sq ft of them. Unfortunately I don't have any more accessible roof space without going all the way up to the top of the second story.

The panels are a good 100 ft away from the pool.

I'm surprised how low your temperature losses are. If I get the pool up to 85, it can drop into the high 60's overnight, a 15+degree drop. Our ambient temperatures are the same. It can be in the 80s during the day and in the 40s-50s at night.

My pool is above ground, so maybe that's the difference?
Click to expand...

100 ft runs could explain why your have such low flow rates through the panels. What size are the pipes and how high are the panels? Also, what is your filter pressure with the panels on vs off?


Also, if you are seeing a 15 degree drop over night, that would imply that you have a 15 degree gain during the day but I don't think that is possible with 80 sq-ft of panels so something isn't adding up? How did you get the pool water to 85 in the first place?
 

Enjoying this content?

Support TFP with a donation.

Give Support
1.5" all the way there. THey are about 9 feet off the ground at the low point, and 13 feet off at the high point.

The place where the panels are is perfect, south facing. It gets sun all day long. Ill take some measurements once I get everything going again for the summer, but it does rise 10-15 degrees by days end. If i run the pump from 8am to 5pm, the panels stay on all day and the pool does get that warm (as long as ambient is also that warm). By the next morning, its back to the low temp.
 
I'll have to chime in that a pool cover is going to be the cheapest and easiest way to maintain your temps. Here in AZ, where it is dry, I would experience around a 10 or more degree loss in pool temps right now without the cover on. With it on, I lose 2 degrees ;)
 
I have a 20x40 inground pool and heat it mostly with 80sqft of solar mats that are on the ground near the pool. I always cover the pool when not in use which makes a huge difference. I have an intelliflow pump that I run at a very low flow rate during the day just to get flow through the panels. Since I have time of day electric pricing I only boost the pump output at night when power is cheap and don't let the water flow through the panels a night (obviously). This combination keeps my pool at 80-85 degrees most of the year and I only use my heatpump at the very start and very end of the season for maybe two weeks.
 
The solar cover is more important than the solar heater!

I think you would be wasting your time with the second pump and costing yourself a lot of money. Figure out what it costs to run a one HP pump - you will be surprised at how much it costs. Are you panels all piped in series? If so you might want to consider plumbing them in parallel, that will drop your pressure loss and increase your flow rate. Does all the flow go through the panels or only part of it? If part of it why not increase the flow through the panels?

During the day I set my pump to run at about 200 to 300 watts and have the flow go through a pair of 2' by 20' panels in parallel, that is enough flow to have the water just slightly increase in temperature and get maximum heat extraction from them.
 
I agree, the pump is a waste of time and could possible cause more problems. With 80 sq-ft of panels, you only need about 8 GPM to reach maximum efficiency. You might actually try bypass some of the flow from the panels. What is your filter pressure with and without flow through the panels?
 
You must log in or register to reply here.
Thread Status
Hello , This thread has been inactive for over 60 days. New postings here are unlikely to be seen or responded to by other members. For better visibility, consider Starting A New Thread.
Top Bottom
Back
Jump to latest Follow Reply