Hi-tec solar panels

[shikkapow]

I found a local advertisement for three year old Hi-tec HT-10 (4x10) solar panels for $20 each. I've been thinking about a DIY system with PVC pipes or Irrigation pipes, but I dont think I can beat the price of these panels. How long do these panels last and is it worth the investment?

http://www.earthenergyunlimited.com/SolarProducts/SolarWaterHeating/SolarPoolHeating.html

here is hi-tec website, but it looks like they changed the model numbers, now HT410(which makes me wonder if there was an issue with the old model so they updated the design?):

http://www.hitecsolar.com/specs.html

I have an 11k gallon inground pool (screened) and have a perfect south facing yard for the panels. I was planning on putting in a 4 gpm pump with its own small PV panel that runs when the sun is up, and turns itself off when it goes down. this leads me to a few more questions.

1. I plan on picking up 5 of these panels, so the headers will be on the bottom and top, and have about a 12-15 foot head. Is there a small reasonably priced pump that will hit 4 GPM @ 20~ psi (max) that will work with a small panel?

2. If I have all the headers at the bottom (source) and top (discharge) connected in parallel, will that reduce the pressure seen by the pump as if there is only one panel, or will I need a 20 GPM pump, or is the 4GPM carried across all the panels?

3. My pool is irregular shape, 33 feet long at its maximum, and 18 feet wide at its max. (600ft2~) do I need 50% panels to give me enough square footage to warm up my pool? I live in Northern Florida and get 6+ hours of sunlight on my planned area now, and can expect it to be pretty close to that in late December. I dont expect to be able to swim year round, but I had to close the pool almost 2 months ago (probably because of the screens) because it was just too cold. Todays temps were in the low 70's and sunny. I'm hoping I can eek out an additional 6 weeks out of the pool on both ends of the season with 5 panels (200ft2) but 6-7 panels arent out of the question because of the price.

4. it does occasionally freeze here, so I'll have to drain it, but if I forget is there some device that I could install to protect the panels from getting destroyed by ice?

Thanks!

[russ]

4 gpm - Not enough turn over for the pool to be of any use

[Naptown]

you should go for the 50% or 7- 8 panels that size if you can get them.
You use the pool filter pump to circulate the water with a controller and diverter valve to control the flow.

[shikkapow]

you should go for the 50% or 7- 8 panels that size if you can get them.
You use the pool filter pump to circulate the water with a controller and diverter valve to control the flow.

Thanks naptown. I can get up to 20 of these, but I was thinking 10 would be fine (cut rate in bulk ). they look to be in great shape, just need some cleaning.

I wanted to not run it through the filter pump if possible to creat "free" heat, but I dont know the GPM i would need to push through the panels, and rus didnt exactly help with his enlightening tip.

the panels state 4gpm is recommended, but do I multiply each panel by 4 to figure out what I need? 40 GPM seems a bit excessive (ten panels), Im just trying to do this as a DIY project and looking for some help figuring the whole thing out.

[inetdog]

Thanks naptown. I can get up to 20 of these, but I was thinking 10 would be fine (cut rate in bulk ). they look to be in great shape, just need some cleaning.

I wanted to not run it through the filter pump if possible to creat "free" heat, but I dont know the GPM i would need to push through the panels, and rus didnt exactly help with his enlightening tip.

the panels state 4gpm is recommended, but do I multiply each panel by 4 to figure out what I need? 40 GPM seems a bit excessive (ten panels), Im just trying to do this as a DIY project and looking for some help figuring the whole thing out.

Since the solar thermal panels will not reach nearly as high a temperature as a gas-fired pool heater, they need correspondingly higher flow to move the heat from the panels to the pool at a lower temperature.
4GPM per panel (40 GPM for ten) may be more than you need, but it is the flow rate at which the panels have a chance of producing their rated output.
The other limitation of using solar is that you have to keep pumping during the good production hours of the panels instead of only the more limited time that a heater would be running.
If you don't need to have your circulator running that many hours just to filter your water, then that expense becomes part of your overhead for the solar heating.
You could put in additional solar PV panels to produce power to a solar-engineered pool pump, but that will cost you more in the short run.
Getting started by using your current circulating pump until you can see what you get from the thermal panels seems to me to be the way to go.

[Naptown]

Since the solar thermal panels will not reach nearly as high a temperature as a gas-fired pool heater, they need correspondingly higher flow to move the heat from the panels to the pool at a lower temperature.
4GPM per panel may be more than you need, but it is the flow rate at which the panels have a chance of producing their rated output.
The other limitation of using solar is that you have to keep pumping during the good production hours of the panels instead of only the more limited time that a heater would be running.
If you don't need to have your circulator running that many hours just to filter your water, then that expense becomes part of your overhead for the solar heating.
You could put in additional solar PV panels to produce power to a solar-engineered pool pump, but that will cost you more in the short run.
Getting started by using your current circulating pump until you can see what you get from the thermal panels seems to me to be the way to go.

First of all 4 GPM is not nearly enough flow. Flow should be somewhere in the 2-3 GPM per collector range. Go with the manufacturers recommendations on flow rates.
These are generally unglazed collectors. We use and sell a lot of Aquatherm or Solar Industries (same thing) collectors.
Look at the BTU curves on these ( SRCC ratings) These work best at high flow low temp applications. Reducing flow to increase outlet temperature is counter productive. More BTU's will be produced when the collector is operating closest to the ambient temperature..

[shikkapow]

the 4gpm is from the manufacturers website:

http://www.hitecsolar.com/specs.html

Recommended Water For Rate (gallons per minute) 4.0

I didnt know if that was multiplied per panel, or just spread across the entire collector as one unit (if that makes sense) to equal 4 GPM total
or if 10 panels = 40 gpm 3 panels = 12 gpm etc

i have zero experience in anything solar other than a few good sunburns, and figured this was a good way to cut my teeth since its a (relatively) simple project and all I need to do is figure out the pump. the plumbing and rack should be easy since its going to be a 10 foot head vs a rooftop install, im just trying to figure out how to make it all "free" with a 12 v or 24 v pump that will turn on with the sun, and turn off when it drops down in the evening.

inetdog... good point . I could tie it into my existing pump an put in a valve to open it or choke it down to figure out what flow rate I would need and then build the pump setup to match my requirements, and just cut it out of the system when I am ready. i think that's what I will do

[inetdog]

the 4gpm is from the manufacturers website:

http://www.hitecsolar.com/specs.html

Recommended Water For Rate (gallons per minute) 4.0

I didnt know if that was multiplied per panel, or just spread across the entire collector as one unit (if that makes sense) 10 panels = 40 gpm 3 panels = 12 gpm

etc

i have zero experience in anything solar other than a few good sunburns, and figured this was a good way to cut my teeth since its a (relatively) simple project and all I need to do is figure out the pump. the plumbing and rack should be easy since its going to be a 10 foot head vs a rooftop install, im just trying to figure out how to make it all "free" with a 12 v or 24 v pump that will turn on with the sun, and turn off when it drops down in the evening.

It is multiplied by panel, and a solar powered pump with a 40 GPM output is unlikely and the solar panels could cost more than the rest of the system.
Even if you have to run your circulating pump, the heat would be free.
If you would not normally be running the pump during the day, then in addition to the remote controlled diverter valve that Naptown described, you would add a relay that would turn on your pump if it is not already on. So no operator attention would be required.

It sounds like this is the way you are going to go, so good luck. Your idea of experimenting and measuring is good and we would like to hear your results.

[Naptown]

It is multiplied by panel, and a solar powered pump with a 40 GPM output is unlikely and the solar panels could cost more than the rest of the system.
Even if you have to run your circulating pump, the heat would be free.
If you would not normally be running the pump during the day, then in addition to the remote controlled diverter valve that Naptown described, you would add a relay that would turn on your pump if it is not already on. So no operator attention would be required.

It sounds like this is the way you are going to go, so good luck. Your idea of experimenting and measuring is good and we would like to hear your results.

There are controllers that are available. Heliotrope is the one we use. If your pool is fairly modern look at the control panel. Many Pentair etc will be set up for solar already. this means you only need to purchase the valve and sensors to complete the system.
If you have more than a simple timeclock for the filter pump post the controller model number and manufacturer.

[shikkapow]

i just have the simple time clock for the panel its an "older" install from about 2002. I forgot to mention that its a salt water system, and the timer clock is tied to the salt cell/controller so when the timer kicks on, the entire system kicks on. The salt cell is energized and starts to work, and the pump is running full steam. The pool is in a screened enclosure, so this time of the year I can turn down the filtration to just a few hours a day to save a little electricity and more importantly save the salt cell some of its expected life time, because nothing is falling into the pool and no one is in it, so i just need to maintain chlorine levels to keep the algae out. Saving the main pump and chlorine generator some operations time (and lengthening their lifespan) is why I want to hook the heater pump to a separate system since I don't need to run the chlorine system as much this time of the year.
__



If I warm the water up to where I want it, the chlorine generator and filter will have to run longer to keep the pool clean.
The whole point of the solar pump is to save electricity in the winter because the main pump is running a lot less because the cold temps dont require the system to run as much as it does in august (because its too damned cold to get in).

if you warm it, they will get in.


______
(The above was internal dialog and figured I would just share because the lightbulb went off as I was typing. its amazing what a few cold beers will do to unlock your brain )

I'm just going to tie in the panels to the main pump with a cross connect valve like inetdog suggested and eventually replace it with a newer pump (its original and probably a power hog). I was just really looking forward to running the pump on solar,getting "free" heat (yay for rainbows and unicorn farts) and missed the fact that it'll make the water funky if its warmer and the algae is happy.

unintended consequences.

sigh, Ill post pics when the system is up and do my best to give you data on the inputs and outputs of the system.

[shikkapow]

I finally got around to installing the heater, I plumbed the system into the existing pipes, and put in a three way (manual) diverter valve.
I was only able to get 6 panels onto my platform, but it seems to be working pretty well. we didnt buy the blankets or any type of covering for the pool yet because we wanted to see if the final project would be too much of an eyesore, and if it would be efficient enough to heat the pool.

How do I calculate the BTU's? the pool temp is currently 77 degrees, and the closest jet to the heater is pushing out 81 degrees (there is probably some loss on the far jets because the ground is sucking some heat out)
purely scientific method for flow rate was a pool noodle covering the jet and filling a 5 gallon bucket resulted in 20 seconds per jet. 45 GPM~ flow rate.

I cant find the formula to determine the BTU's from the panels.
its 82 degrees outside and little wind and lots of sun.

Thanks!

[Naptown]

Flow rate x 8.2 ( weight of water) x temperature rise input to outlet = btu per minute x 60 = btu per hour.

[Szumlanski]

First of all 4 GPM is not nearly enough flow. Flow should be somewhere in the 2-3 GPM per collector range. Go with the manufacturers recommendations on flow rates.
These are generally unglazed collectors. We use and sell a lot of Aquatherm or Solar Industries (same thing) collectors.
Look at the BTU curves on these ( SRCC ratings) These work best at high flow low temp applications. Reducing flow to increase outlet temperature is counter productive. More BTU's will be produced when the collector is operating closest to the ambient temperature..

You it the nail on the head about running water through solar panels too slow. Most people think that letting the water heat up more is more productive. However, solar panels are more efficient at absorbing heat when the difference between the water temperature and surface temperature of the panel is larger.

[thastinger]

For a DIY install you're going to need to figure out how much pressure the panels can tolerate and how much pressure is present at the height you plan to install them. My system runs from the regular pool pump and a series of valves manages how much water goes to the solar heater vs how much returns directly to the pool (temp control). Don't forget your check valves/drain valves and air valves, they keep the panel water from back flushing the filter into the pool after the pump is shut off and allow for winter draining etc.

[oliviajohnson]

Go for 7-8 Panels as it is best option for you, Use the pool filter pump to circulate the water with a controller.But in my opinion, best thing for you is to hire any Professional solar water heater company and talk them regarding your problem.This will be definitely a best solution for your problem.If you would like to get affordable services with top-notch company, then you should consider this one, as i have taken their services in the past and they were great.They did their work with great passion and their team was so experienced.