DIY COPPER solar collector and Salt Water...

[armstrr]

Chem Geek....this one is aimed at you! i am entering the final planning stages of concurent building projects...both fairly large (in my mind...) one is a garage with a basement workshop, the other a 20 x 40 inground vinyl liner pool. i hope to heat both levels of the shop with in floor radiant heat...with the heat provided by DIY solar collectors as found on builditsolar.com. in the summer, and shoulder swimming seasons, i would like to use these same panels to heat the pool.

i know the black plastic (unglazed) solar collectors are efficient and effective and chemically inert...perfect for pool water. if i follow the BBB methods of maintaining a pool, is it possible to pump the pool water directly to copper solar collectors or would this be a total no-no due to the pool chemistry not playing nice with the copper pipe? what in specific needs to be watched or kept in check to make this work? or is this fool hearty and do i need to use a shell and tube heat exchanger (and an additional pump)?

a little off topic, but i even wonder if i could repurpose a pentair intelliflo during the winter months to pump water to the collectors in a drainback type system.

your thoughts (and prayers! are appreciated!)

thanks,
robb

 

[PoolGuyNJ]

I urge you to keep the systems separate. Pool water and copper pipe is a bad mojo. Also, PEX piping used in radiant does NOT like pool water.

An Intelliflow is way too much pump for the PEX. A TACO circ pump is likely to be a better choice for the radiant system.

Scott

 

[JasonLion]

Standard solar heating panels made for swimming pools are fairly inexpensive and much more efficient than anything you can build yourself. I would buy the panels commercially and then install them yourself.

Copper is definitely a bad idea.

 

[armstrr]

ok, so its a bad idea. its interesting that there are commercial copper systems available: www.sunraysolar.com/poolpanels.php

and as for the intelliflo being too powerful (probably quite true!). my building is to be 44' long, and i plan on having solar collectors the whole length, so its not like there was going to be 2 or 3 panels.

i still plan on some diy panels similar to what sunray sells. i will just have to use a heat exchanger in the mix. any thoughts you have on that are welcome.!

 

[JasonLion]

Sunray panels are designed to be efficient when the air temperature is relatively cold. They will certainly work, but they won't be nearly as efficient during the swim season when the air temperature is high, as a solar panel designed for pool use would be. On the other hand, they will be far far better for heating the building during the winter.

If you have the panels up for heating the building anyway, there is some merit to using them for the pool in the spring/fall when the building heat load is lower. However, you need to keep in mind that a swimming pool needs far more heat than a typical building does and the reduced efficiency of that panel designed combined with the heat losses in the heat exchanger make such a mixed use system much less efficient than it might at first appear. Depending on how much roof area you have available, using a mixture of two different kinds of panels starts to make more and more sense.

Copper is very sensitive to low PH, which can etch copper out of copper pipes which can then form unsightly stains on the pool which are very difficult to remove. If you are circulating pool water through the pipes this makes copper a very bad choice. If you have a sealed system, with special water just for the panel system, this is not an issue because the heat exchange water can be treated to be safe with copper.

 

[armstrr]

all points are taken. yes, i understand that the system i am looking at building is less efficient during the typical pool weather...but like you say, at the beginning and end of the season, the flat plate (glazed) collector is likely to be somewhat more efficient. really, my kids will swim in ANYTHING. (we went to the beach the other day...the water must have been barely above 50 degs...they were in it...mind you for short periods...the expression on their faces was priceless). the solar collectors are really for my workshop, the fact that i can tie them in to the pool is just a bonus and will make it so I will get in the pool a little earlier...) i am also planning to religiously use a solar cover. ( i'm designing an in-deck roller for asthetics and ease of use)

i may take a look at a dual type system however...there may be merit to having the systems seperate...i'll start a new thread about commercially available choices.

 

[chem geek]

Though copper is found in some heat exchangers in gas heaters, the trend is to move to more chlorine-resistant materials such as cupro-nickel or titanium. This is especially true for higher salt levels. The main difference is that it is much less expensive to replace a copper heat exchanger in a gas heater than it is to replace most or all of your solar panels.

Yes, there are solar panels that use copper (such as most glazed solar panels), but these almost universally use a separate fluid for the panels and then use a heat exchanger between that system vs. the pool water.

If you hardly ever had to shock your pool, kept the salt levels low, and kept the FC/CYA ratio low, then the rate of copper corrosion could be kept to a minimum. If this is your own system and you are willing to take the risk, then that's one thing, but I know when I asked some glazed solar panel companies (when I was researching that for the future) about putting pool water through directly, they balked.