Trying to keep up w/ Chem Geek

[CarlD]

I was going to plum them in series, however, I don't think the water would be in each panel long enough to heat it up enough.
....

Any suggestions?

Shelley

Yes. Abandon the assumption that the water needs to heat up in the panels and come out "hot". There ARE limiting factors to solar panels, and C'Geek can (and has) explained them. But they are limits to a fundamental truth: the more water you move through the panels the more heat you'll get in your pool.

Think of your panels as a giant car radiator working in reverse. Do you think that SLOWING DOWN the rate of water flow through your engine will cool it MORE???? Of course not--the faster the water moves the more heat is pulled out of the block to be distributed by the radiator. Sure there are limits, but that's why when your water pump isn't moving as much water, your engine overheats. The panels work the same way.

Remember how I ALWAYS say: In direct sun your panels should be cool to the touch, or, at most, mildly warm. Imagine: it's 95 degrees and the sun is blistering, downright cruel. But your solar panels are COOL! What is going on? Turn 'em off and they get firey in minutes. Clearly the water is cooling them. EXACTLY!

And all that lovely heat energy is dumping into your now-comfortable pool!

Sure, there are maximum efficiency points on the panels, and too much pressure can cause cavitation, not to mention LEAKS, and there's fancy issues with the fluid in the center moving faster than the fluid on the wall of a chamber--but Chem_Geek can explain that to get MAXIMUM EFFICIENCY from a panel.

Meanwhile, parallel plumbed panels each can function as a separate entity, at max efficiency.

In general (with some caveats and exceptions) the more flow you get the faster your pool heats up. You don't "wait for the water to warm up" any more than your car engine waits for the water to warm up in the block.

It "seems" to make sense, but it doesn't really.

I keep hammering this: You want BTUs, not temperature to warm your pool. Pool heaters are rated in BTUs--because that is how heat energy is transferred.

Remember: A BTU (British Thermal Unit) is the amount of heat energy needed to raise 1 pound of water 1 degree Farenheit. It takes 10x more BTUs to raise 6800 pounds of water 1 degree that it takes to raise 68 pounds of water 10 degrees. (that is, 100 cubic feet vs 1 cubic foot)

[ShelleyAnn]

CarlD - Let me ask it this way...Do you think the water will be as warm as last season when I forced all 48 GPM thru 32' of solar panel?

[CarlD]

CarlD - Let me ask it this way...Do you think the water will be as warm as last season when I forced all 48 GPM thru 32' of solar panel?

I think if you plumb all your panels in parallel rather than serial you will see a SIGNIFICANT boost in effectiveness, especially if you add the two new panels that way.

Remember: It's BTUs that matter, not temperature.

Once I get my panels hooked up, with this nice weather I should see temp gains of 8-10degrees per day. When all the panels were in serial, I'd see 4-6 degrees per day. (my panels are 2'x4' but I have about 30 of them--split into 2 parallel plumbed groups).

[ShelleyAnn]

Carl D - First off, thanks so much for hanging in there with me.

Question - Won't I have the same amount of water going thru as last year, just without the too-high pressure?

Last question - Do you think I should bag the corregated hose I had last year and spend the $$ on flex PVC with the smooth lining? Will there be that much difference?

Thanks again.

[chem geek]

ShelleyAnn,

I'll take a stab at this one, at least for your first question. When connected in parallel, the total flow rate will be much higher because there will be far less resistance in the solar panel piping compared to being connected in series. Think of it this way -- your pump is spinning at a certain fixed rate (RPM) so trying to force water through a longer but narrower pipe (i.e. solar panels in series) is much harder so will result in higher pressure and lower flow rates compared to forcing the water through a shorter but much wider pipe (i.e. solar panels in parallel) which will result in lower pressure and higher flow rates. When I refer to flow rates, I mean through the entire system into your pool, not "per panel".

Now it is true that the flow rate per panel when connected in parallel may be less than the flow rate when they are connected in series, but when in series the water heats up as it goes from panel to panel and this higher temperature water radiates its heat back into the air via a hot panel (the last panels in series, especially). When connected in parallel, the panels stay cool and absorb heat from the sun most efficiently. The much larger total flow rate more than makes up for the smaller temperature increase on output into your pool -- this is what Carl means when he says it is the BTUs that matter, namely the total heat that is transferred to your pool.

Imagine it this way. If you heated one cup of water to 100F higher temperature and added it to your pool, it would have the same effect if you took 100 cups of water to 1F higher temperature and added it to your pool (ignoring the small change in total water volume). It's the same amount of added heat in either case. The reason it is better to add more water volume at smaller temperature increase is that this is more efficient. You can imagine that having a cup of water at 100F higher temperature than your pool water won't stay that way very long sitting in a cup -- it will lose heat rapidly since it is so much hotter than the surrounding air. In the same way, water flowing through solar panels that is much hotter won't stay that way if the air around the panel is cooler (which is typically the case -- the air is cooler, but the sun's energy makes the panel slightly warmer and transfers this heat to the water flowing in the panel).

Richard

[CarlD]

Carl D - First off, thanks so much for hanging in there with me.

Question - Won't I have the same amount of water going thru as last year, just without the too-high pressure?

Last question - Do you think I should bag the corregated hose I had last year and spend the $$ on flex PVC with the smooth lining? Will there be that much difference?

Thanks again.

You know, I really don't know the answer to this. It SEEMS to make sense, but there will be water trapped along the edge while other water moves past it, but I'd be lying if I said I could give you a definitive answer.

I personally prefer TigerFlex because I can use glued-on fittings, which I consider far more reliable than barbed fittings and hose clamps. Yet corregated hose is VERY easy to work with and will bend to fit FAR tighter corners than T-Flex. The connections between my myriad little panels are all corregated and T-Flex would be impossible to use.