Some Noob Questions About A Solar System

[Surf Hawk]

I'm plying away at different components of the pool in the house we bought 2.5 months ago. It has a older rooftop solar system on a west facing roof that has no obstructions. When we moved in early Sep it was cranking out hot water. The previous seller said if he forgot to bypass it during the summer the pool could hit 100°. I turned it off shortly after moving in because of pool information overload, but now have it on again and seeing if it makes a difference. A few questions:

1) What do solar owners think their power consumption is when the solar is on vs. bypassed? I thought pumping all that water 20' up would take a lot of power, but some quick tests looking at our meter with it on and bypassed showed that switched to solar actually used less, which seems impossible. Our power meter read 1.60kW w/o solar and 1.56kW with solar. Not sure what else was in the house at the time but I ran the test 3 times in a 10 minute period and numbers were always the same.

2) Now that we are in Nov with a fewer sun hours and a lower angle of sun, does it make any sense to run our solar? Our pool has dipped to 64° since I bypassed solar, sunny skies and temps now 75° in the day, 50° at night. We were still taking quick dips with our daughter in a wetsuit at 70° so the ability to keep it in the 70s would be worth something to us.

3) These panels look old and you can even see some dried up moss on them in some parts. Has there been any dramatic improvements in efficiency in the last decade that would make replacing these with new ones an attractive option? They are vertically oriented 4' wide ones, maybe 10' long. We probably have 8 of them. Our pool is 500sqft (16x32) so the current system is probably undergunned.

I realize I should of taken photos of these panels, I plan to soon. Thank in advance for any advice.

 

[linen]

1) What do solar owners think their power consumption is when the solar is on vs. bypassed? I thought pumping all that water 20' up would take a lot of power, but some quick tests looking at our meter with it on and bypassed showed that switched to solar actually used less, which seems impossible. Our power meter read 1.60kW w/o solar and 1.56kW with solar. Not sure what else was in the house at the time but I ran the test 3 times in a 10 minute period and numbers were always the same.

Your results are correct. Since there is a little more constriction (head loss) in your plumbing with solar engaged, you are pumping a little less water which actually reduces your instantaneous power consumption (...i know, i know...this seemed counter intuitive to me at first as well).

2) Now that we are in Nov with a fewer sun hours and a lower angle of sun, does it make any sense to run our solar? Our pool has dipped to 64° since I bypassed solar, sunny skies and temps now 75° in the day, 50° at night. We were still taking quick dips with our daughter in a wetsuit at 70° so the ability to keep it in the 70s would be worth something to us.

It all depends on your specific setup, but if you are still getting good sun on the panels, you may still get some heating benefit. Addtionally, having a solar cover on (especially at night) will help keep your heat in the pool.

3) These panels look old and you can even see some dried up moss on them in some parts. Has there been any dramatic improvements in efficiency in the last decade that would make replacing these with new ones an attractive option? They are vertically oriented 4' wide ones, maybe 10' long. We probably have 8 of them. Our pool is 500sqft (16x32) so the current system is probably undergunned.

You panels sound similar to the ones currently available, though post some pics including a couple of closer up ones so we can see the size of the "tubing". For the most part, solar efficiency is dominated by surface area, though if the individual tubes are large, the panels will be less efficient.

 

[jblizzle]

I agree with all the above.

Will just add that my pool has dropped to around 70 running the solar with no cover. No one has swam in probably almost a month. So, I just shut mine down over the weekend ... why add a little heat if it is still not warm enough for people to want to swim?

In my case, having the solar off means I can run my pump on low speed, to it certainly saves me money to turn it off.

 

[Surf Hawk]

Thanks for the responses. Good news that the power readings I am getting are correct. If and when I get a dual or variable speed pump I look forward to running at low speeds when the solar is off.

We are due for sunny skies so I am going to keep the solar system and solar cover on all week . Saturday when I do my weekly maintenance I will see if the temp improved any. Then I will get some more details and photos about the solar system I have.

 

[Isaac-1]

Answering your questions without knowing your location means we have to do a good bit of guessing (you should add it to your profile so it shows under your name like ours does).

1, As has been mentioned already the power consumption of your pump should not change much, but while on solar your total water flow rate will be reduced due to the added back pressure. So from a $ per gallon filtered you will be paying more with the solar on, but for $ per run time hour you should not see much change.

2, Solar is good at maintaining temperature, but not so good this time of year at regaining water temperature once lost, this time of year most of us with solar pool heaters are fighting a loosing battle, with weaker sun light, shorter days, colder temperatures, and for many cloudier skies. Often all it takes to go from comfortable pool temperatures to end of the season is a few cloudy days in a row.

3, Very little has changed in performance of commercial panels in the last 15-20 years, I would say that there have been some improvements in materials relating to life expectancy as well as mounting hardware, but little in performance improvements (maybe 5%-10% at best, and this is under ideal conditions).

When it comes to getting the most out of solar panels, an automated solar controller can really help maximize output as it turns the panel flow on when there is heat to be generated, and off when heat would be lost through the panels, either at night, when clouds come out, or when the wind starts blowing on a cold day

 

[Surf Hawk]

Sorry, just edited my profile. We are in Santa Barbara, CA. Will report back this weekend on how the temps looks after 5 days of the solar on, and some photos of our system.

 

[Surf Hawk]

So my test with the solar cover and solar system on for 5 days of sunny skies got the temp from 63 to 68. This week my test is solar cover on but solar system off and we'll see what happens.

I was also able to check out the system on the roof, and boy is it clapped out. It is a series of metal tubes with fins on each side. A lot of moss and a lot of broken tubes that have been welded shut by previous owner. They are 44" wide x 10' long and I have close to 10 of them. I calculated it to be 312sqft if the whole system was operational. This compares to to our ~500sqft pool. I am surprised this thing even works. Here are some photos of the system and pool.

The system on our west facing roof around sunset. Inlet is on bottom, return is on top. Looks like the black paint is pretty badly wearing off.
[attachment=1:19m2eugn]IMAG1423.jpg[/attachment:19m2eugn]

Close up of one panel, with moss on bottom.
[attachment=2:19m2eugn]IMAG1424.jpg[/attachment:19m2eugn]

Close up of moss and ~3/8" OD tubing with metal fins on each side.
[attachment=0:19m2eugn]IMAG1425.jpg[/attachment:19m2eugn]

 

[Surf Hawk]

Here are some more.

Looking to the south
[attachment=2:1nefho72]IMAG1426.jpg[/attachment:1nefho72]

Some pretty bad shape hoses connect the panels
[attachment=1:1nefho72]IMAG1428.jpg[/attachment:1nefho72]

I hear some noise at this valve where it goes to the return, not sure if air gets in here
[attachment=0:1nefho72]IMAG1429.jpg[/attachment:1nefho72]

 

[Surf Hawk]

Here is the pool, not in the best shape.
[attachment=1:k0rzj9ll]IMAG1430.jpg[/attachment:k0rzj9ll]

When the pressure in my DE filter gets to 30psi, I get air in the return line when running the solar. A backflush will solve this for a week or two. Next weekend I plan to open the filter and do a manual cleaning of it, as the pressure rose from 22 to 30 in one week.
[attachment=0:k0rzj9ll]IMAG1432.jpg[/attachment:k0rzj9ll]

Thanks for all of the insight so far.