Using photovoltaic panels to heat a pool

ecodad

In The Industry
Sep 7, 2007
3
#1
A comment here about using PV solar panels for heating a pool. Absolute waste of a very expensive piece of equipment. Heating a pool with electricity is bad enough, heating it with solar electricity is stupid. Reduce the amount of electricity you use and save the environment rather than waste it... power your pool pump, run your fridge, run your lights & TV instead...

It makes much more sense to use conventional solar thermal collectors to heat an out door pool - they cost about 1/20 as much as a PV system, works better & lasts longer.

I've been designing,selling & installing solar heating systems for 28 years - installed hundreds of solar pool heating systems & never seen a less appropriate application of a solar system....
 

chem geek

TFP Expert
LifeTime Supporter
Mar 28, 2007
12,082
San Rafael, CA USA
#2
I fully concur with ecodad. If you are going to be heating the pool and find that using a solar cover is not sufficient, then using standard solar panels for heating the water will be around 80% efficient in terms of capturing energy from the sun. Compare this with typical solar electric (PV) panel efficiencies of 8% (relatively inexpensive systems) or 15% (expensive systems). Some lab systems are at 30% and the maximum theoretical efficiency of the multi-layer broad spectrum absorbers is 70% (though I think the current record is closer to 50%). Perhaps if someday these latter systems become available, then it will make more sense to use PV instead of solar panels, but not now.

PV is certainly better than no PV, but if choosing between PV and solar panel water heating, there's no contest.
 

KurtV

LifeTime Supporter
Mar 29, 2007
270
SE Louisiana
#3
ecodad said:
A comment here about using PV solar panels for heating a pool. Absolute waste of a very expensive piece of equipment. Heating a pool with electricity is bad enough, heating it with solar electricity is stupid. Reduce the amount of electricity you use and save the environment rather than waste it... power your pool pump, run your fridge, run your lights & TV instead...
The OP said that heating the pool wasn't the reason for installing the solar panels; they're used for providing household electricity. I imagine he had the pool heat pump before installing the PV array. I, and I think everone else who read the original post, took it as a fun way to show us his PV array in the context of a pool forum.
...

I've been designing,selling & installing solar heating systems for 28 years - installed hundreds of solar pool heating systems & never seen a less appropriate application of a solar system....
eco,
I've been hanging around internet forums for a number of years and I've never seen a more inappropriate first post on one. Try chilling out a little.
 

The Mermaid Queen

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LifeTime Supporter
Mar 28, 2007
2,522
Northern KY
#4
ecodad said:
A comment here about using PV solar panels for heating a pool. Absolute waste of a very expensive piece of equipment. Heating a pool with electricity is bad enough, heating it with solar electricity is stupid.
chem geek said:
I fully concur with ecodad.
I am neither particularly green nor do I know much about solar power. But personally I thought it was a great way to heat your pool. If you already have the solar, why not??

If the roof is already covered with PV panels, where would you propose he put the solar pool panels, anyway?

Would you all think using NG or LPG a better option? Or plugging that heater into the wall? I would think even greenies like ecodad (judging by your name) would like people using solar for a rather frivolous thing like heating the pool, instead of using up 'city power or gas' for that.
 

ecodad

In The Industry
Sep 7, 2007
3
#5
Perhaps my assessment of the use of PV for heating a pool seemed harsh :shock: - it was intended to point out the wastefulness of using a product that could potentially save energy and prevent pollution / green house gases, being used to increase consumption rather than reduce it. The owner of the PV system was simply boasting about his conspicuous consumption - not about saving energy or money or the environment.....
If the PV system is being used to heat a pool, it can't be saving electrical energy in his home - or even running his pool pump. Heat your pool with thermal solar collectors (and use a solar blanket) and forget about PV for heating anything - at least until they are cheap enough that the government doesn't have to subsidize them (so we're not paying for his wasteful behavior). :x

ecodad
 

chem geek

TFP Expert
LifeTime Supporter
Mar 28, 2007
12,082
San Rafael, CA USA
#6
My comment agreeing with ecodad also wasn't meant to be harsh. It's just that heating pool water with solar power currently is not nearly as efficient use of the sun's energy compared to using a traditional solar pool water heating panel. The ideal situation, if you had enough roof (or other) space, would be to have some space allocated to heating the pool with traditional solar water heating panels, some small space allocated to heating water for the hot water heater (these are special panels enclosed in glass) and the rest as PV for powering the house, pool pump, etc. That way you maximize the utilization of the sun's energy per exposed area you are capturing. The exact balance will depend on the specifics of usage of each item.

Obviously, if you've already got the full roof space set up for PV, then you can use it for anything you want including heating pool water. I don't think ripping out some of the PV and replacing with solar pool water panels makes much sense unless you could sell the PV panels to someone else and recoup most of your cost (which would be hard since some of it is labor).

A full analysis would take into account that pumping water through solar panels on the roof requires more energy. I know in my own pool, for example, that without the solar (and with my variable speed pump) that I only need 275 Watts for 26 GPM and one turnover per day vs. 1500 Watts when the solar is on to get 48 GPM through 12 panels for 4-6 hours per day. The panels have around 40 square meters exposed to the sun and output around 20,000 - 30,000 Watts (70,000 - 100,000 BTU/hr) from the sun for heating the pool. So the extra pump electrical "cost" of around 1200 Watts is relatively small (<= 6%) compared to the total heating power obtained form the sun. The same area exposed with PV panels, even assuming 10% efficiency, is 4000 Watts.

[EDIT] I should add that solar panels for heating pool water have an efficiency that is sensitive to wind speed and air temperature vs. water temperature. If the air is cooler than the water and there is wind, then the efficiency drops (a 10F difference with a light breeze drops efficiency from 80% to 70%). Such effects don't affect PV systems (except indirectly in terms of the temperature of the PV panels and slight effects on efficiency).

I should also note that a side benefit to the solar water heating panels is that they keep the house cooler since they essentially act as a heat router directing heat to water away from the roof instead of heating up the attic. We noticed this effect this year after adding one additional panel over our bedroom which is now noticeably cooler compared to previous years (during similar summer heat waves). [END-EDIT]

Richard
 

SeanB

TFP Expert
Platinum Supporter
LifeTime Supporter
#7
ecodad said:
I've been designing,selling & installing solar heating systems for 28 years - installed hundreds of solar pool heating systems & never seen a less appropriate application of a solar system....
You've said you did not mean to seem so harsh in your first post. You came across as judgmental and condescending, but I think we are all willing to accept that perhaps it did not come across in the way you intended. Sometimes intentions are hard to convey when you are not communicating face to face. Please just remember that there are many different ways to do things and we all have our own opinions and circumstances. I'm sure you'll agree that you'll change more minds with persuasive, courteous reasoning than you will with harsh words and rhetoric.

Regarding your 28 years experience, we like to identify people who "In the Industry" with a simple tag under their username. You'll notice I have added that tag to your username.

Thanks for joining TFP and we look forward to learning from your experience. I'm sure you have a lot to contribute. Please just remember to be considerate of other members. Being polite and civil is just about the only hard rule we have here and we take it very seriously.

Sean
 

bluenoise

LifeTime Supporter
Jul 25, 2007
187
Alamo, CA
#8
That's a slick setup! While it certainly isn't the most efficient way to convert sunlight to warm pool water, it's the coolest way to make your home more independent and it sounds like it's about to become a fantastic investment both financially and ecologically. Once I am in a house that I'm am certain will hold me for the years needed to recoup my investment, I'm going solar electric, too.

I like the idea of being able to run pool equipment and A/C without worrying about the electric bill.
 

KurtV

LifeTime Supporter
Mar 29, 2007
270
SE Louisiana
#9
ecodad said:
Perhaps my assessment of the use of PV for heating a pool seemed harsh :shock: - it was intended to point out the wastefulness of using a product that could potentially save energy and prevent pollution / green house gases, being used to increase consumption rather than reduce it. The owner of the PV system was simply boasting about his conspicuous consumption - not about saving energy or money or the environment.....
If the PV system is being used to heat a pool, it can't be saving electrical energy in his home - or even running his pool pump. Heat your pool with thermal solar collectors (and use a solar blanket) and forget about PV for heating anything - at least until they are cheap enough that the government doesn't have to subsidize them (so we're not paying for his wasteful behavior). :x

ecodad
Calling the OP wasteful, boastful, and a freeloader is a funny way of apologizing.
 

kirbinster

Well-known member
Apr 30, 2007
293
NJ
#10
Wow have not been here in a while, can't believe the attacks. Let's set the story straight.

A solar water heating system would do very little to heat my pool when I need it most April and Sept/Oct - there is just not enough sun hours to do much. I don't need much heat in June/July/August.

The most economical way to heat my pool when I need it is an electric heatpump. Those of you that think electricity is not the way to go don't know anything about heatpumps. Mine has a COP of about 6, so for each unit of energy I put in I get six back.

I had the heatpump long before the PV system. I was showing sort of in jest my solar system to heat the pool. And yes it is economical and is environmentally friendly as I am using the sun to produce the power needed rather than fossil fuel.

This year I abandoned my solar (pita) cover in favor of 80sqft of black solar water mats. They generate enough heat in June/July/August that my pool maintained its temp without the cover.

First I think most of this green crap is nothing but BS, but my PV system pays for itself in 4 years and I get 12,000 to 14,000 KWH of electricity each year for free. So bad mouth my system all you want while I laugh my way to the bank.

Thanks.
 

duraleigh

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Apr 1, 2007
31,333
Sebring, Florida
#11
Kirbinster,

I took your initial post in the way it was intended and I understood the application. I believe the majority of readers did the same.
 

bluenoise

LifeTime Supporter
Jul 25, 2007
187
Alamo, CA
#12
kirbinster said:
Wow have not been here in a while, can't believe the attacks. Let's set the story straight.

A solar water heating system would do very little to heat my pool when I need it most April and Sept/Oct - there is just not enough sun hours to do much. I don't need much heat in June/July/August.

The most economical way to heat my pool when I need it is an electric heatpump. Those of you that think electricity is not the way to go don't know anything about heatpumps. Mine has a COP of about 6, so for each unit of energy I put in I get six back.

I had the heatpump long before the PV system. I was showing sort of in jest my solar system to heat the pool. And yes it is economical and is environmentally friendly as I am using the sun to produce the power needed rather than fossil fuel.

This year I abandoned my solar (pita) cover in favor of 80sqft of black solar water mats. They generate enough heat in June/July/August that my pool maintained its temp without the cover.

First I think most of this green crap is nothing but BS, but my PV system pays for itself in 4 years and I get 12,000 to 14,000 KWH of electricity each year for free. So bad mouth my system all you want while I laugh my way to the bank.

Thanks.
Amen to all your points!

It's a great system that needs no apologies.

We're currently looking at buying a property and one of the challenges I was pondering was how to get electricity out to where we'd build a small barn. I did a little research to see what running power from the house would involve and it was going to cost at least $2000 for the trenching and materials and a concrete patio would have to be trenched, too. Your setup inspired me to look into the solar option. For the modest needs of a small barn (a few strip lights at night, perhaps a radio or electric trimmers in the day), a PV storage system would be perfect. If we end up moving forward with that place, I may seek your advice on that option.
 

JCJR

LifeTime Supporter
May 4, 2007
267
Miami
#13
Beggining of this year before pool build, I had a Solar guy come out and give me an estimate. Fafco (solar panels) around $5000 and some cons were when overcast they are not that efficient, take a lot of space and can be ripped up by high winds. They had another product (PV?) and the salesman stated that these glass panels were new technology and for my size pool needed two panels at cost of $13000. Good news, State gave me a break on taxes and I ended up paying the same as solar $5000 after rebate. Pros were that these panels were more efficient, can route water heater and do all my hot water needs, instant hot and they performed the same even with three days of overcast. It sounded good, but since I did not have the money and just inquiring did not pay much attention. I have never heard of any one heating their pool this way so payed little attention till now.

I will be inquiring more information, but does any one know of this? Is there such a thing? I understood that this system heated water not that it produced electricity to run a heat pump. I am in Florida.
 

chem geek

TFP Expert
LifeTime Supporter
Mar 28, 2007
12,082
San Rafael, CA USA
#14
kirbinster said:
The most economical way to heat my pool when I need it is an electric heatpump. Those of you that think electricity is not the way to go don't know anything about heatpumps. Mine has a COP of about 6, so for each unit of energy I put in I get six back.
You are right and I am wrong and boy, do I feel like an idiot :oops: . I am sorry and I apologize. I was only thinking of using the electricity directly for heating as with an electric heater. The Coefficient Of Performance (COP) is the ratio of heat output to the work (energy) input, both expressed in the same units. The COP of 6 is very high so your heat pump is very efficient (or the temperature lift is low so the source is already at a relatively high temperature). So that combined with an efficient, though still practical, solar cell, brings the overall efficiency into a reasonable range above 50%. Combined with the other factors you mentioned in terms of time of year and the inefficiency of solar panels during cooler temperatures, your system makes a lot of sense.

When solar cells become even somewhat more efficient, then their electricity combined with an efficient heat pump will be a more efficient use of the sun's energy than a traditional solar heating panel. Right now, they are close so which to choose depends on the specifics of the application and economics (price of more expensive solar cells vs. cost savings from your own generated electricity).

For anyone wondering where the extra heat comes from in a heat pump, it's from whatever heat source is available, such as the ground or air. The COP varies with the temperature lift which is the difference in temperature between the colder source (evaporation side) and the hotter output (condensation side). A heat pump "moves" heat from a lower temperature source to a higher temperature output (governed by the [EDIT] second [END-EDIT] law of thermodynamics) and that takes a lot less energy than to generate the heat directly via a conversion of energy.

Richard
 

kirbinster

Well-known member
Apr 30, 2007
293
NJ
#16
Chem Geek, you are far from an idiot - and you are not the poster that really ticked me off.

The nice thing about solar PV systems is that are actually more efficient the colder the temperature. I had my hightest electric production day ever on a February day two years ago when the temperature peaked at about 5 degrees for the high.

I'm also a lot more comfortable with PV panels on my roof than plastic panels with water flowing through them.

Conventional solar mats are probably a very good method for most people to use, they just don't help that much in the fringe months. That is why I installed the heatpump, but to save money I iinstalled the 80sqft of water panels this year. My total cost including piping was under $300, and my heatpump has not needed to run even without the solar cover on since early May.
 

ecodad

In The Industry
Sep 7, 2007
3
#17
Dear JCJR

I suspect, unfortunately, that you were conned. The Fafco collectors can operate at 85% efficiency - there is no other product that rates as high. (BTW I don't sell Fafco) Glazed collectors max efficiency is 75% - so you need more glazed collectors, not fewer to heat your pool. Before someone jumps in and talks about how much more efficient glazed collectors are when the air temperature is low - remember that the pool is losing heat at a much greater rate when the air is cold, and no solar system is going to keep the pool warm. Plastic panels are FAR better than glazed collectors for outdoor pools. (no metal corrosion issues either)

Regarding heat pumps. Quoting the maximum COP is very misleading. The level of 6 is seldom (if ever) actually achieved. The seasonal average is the only proper number, and you're lucky if that is 3.

If people think that PV is a good way to heat a pool (through a heat pump) let them buy the PV system without the large subsidies the gov't(s) provide. Those subsidies come from our tax dollars. Yes the system is neat from a technical-toy point of view, but do feel the $30,000 he got from the government (from you & me) so he could use more electricity and not pay for it, is a good use of your money??

Ecodad
 
G
#18
ecodad said:
Dear JCJR

I suspect, unfortunately, that you were conned. The Fafco collectors can operate at 85% efficiency - there is no other product that rates as high. (BTW I don't sell Fafco) Glazed collectors max efficiency is 75% - so you need more glazed collectors, not fewer to heat your pool. Before someone jumps in and talks about how much more efficient glazed collectors are when the air temperature is low - remember that the pool is losing heat at a much greater rate when the air is cold, and no solar system is going to keep the pool warm. Plastic panels are FAR better than glazed collectors for outdoor pools. (no metal corrosion issues either)

Regarding heat pumps. Quoting the maximum COP is very misleading. The level of 6 is seldom (if ever) actually achieved. The seasonal average is the only proper number, and you're lucky if that is 3.

If people think that PV is a good way to heat a pool (through a heat pump) let them buy the PV system without the large subsidies the gov't(s) provide. Those subsidies come from our tax dollars. Yes the system is neat from a technical-toy point of view, but do feel the $30,000 he got from the government (from you & me) so he could use more electricity and not pay for it, is a good use of your money??

Ecodad
how do you know the government is involved.

ok, i may be sortof new here too, but you are coming on way too stong for a public forum, personally i find you an annoyance and would love it if you were banned, but there are rules to modding these sites i know, but just for future refrence lets tone it down here, do you even have a pool, or did you just join to cause flame wars.
 

NWMNMom

TFP Expert
LifeTime Supporter
Apr 8, 2007
1,582
Waaay NW MN
#19
Well there are some nuggets of very useful info in this thread.

It does seem like the atmosphere is getting a bit aggressive; this makes it very difficult for someone coming in "cold" to be able to sort through that type of thing and glean any real objective info. How about taking it down a notch? Thanks!
 

JCJR

LifeTime Supporter
May 4, 2007
267
Miami
#20
Ecodad,

I don't know what you mean by glazed collecters. The new technology panels they showed me look exactly like the glass PV type collectors. They were not plastic tubes, and yes I have read also that Fafco panels are some of the most effecient plastic tubing collectors out there. My pool surface is about 780 sq ft of surface and I was quoted about 14-16 panels of Fafco but only two large glass (mirror) type PV panels that can heat my water heater and pool on demand even on over cast days.