Unintended Consequences of Solar

[Ted]

When we moved to Ohio close to 2 years ago, we ended up buying a house with a pool. I wasn't too keen on getting a pool, not wanting to deal with the cost and maintenance, but I figured that it would probably be fun, especially with a small child who would undoubtedly love splashing in the water.

Last summer we found we could barely use the pool. Because of its shaded location, it never got enough sun to warm up naturally. The hottest it ever got was 80, and that was only a few days out of the summer. For the most part, we were seeing temperatures in the low to mid 70s, far too cold for fun splashing around. The pool came with a natural gas heater, which I refuse to run. They cost a ridiculous amount of money to operate and, while I am not exactly a tree-hugger, I have an objection to burning natural gas basically for the sake of increasing your carbon footprint. We talked about options, and decided to go with rooftop solar panels.

The initial cost wasn't cheap at roughly 3x the cost of what a new propane heater would cost. However, they work great. The pool is now typically in the range of about 80-85F with days that have highs of a similar temperature. We're having a string of highs in the low 90s this week, and I bet it will get even warmer. It's great, it's like getting into a warm bath or almost a cool hot tub. This was exactly what we were hoping for. When compared to paying for natural gas to heat our pool (20'x45'), the installation will pay for itself in under 5 years, not counting the amount I sold the gas heater for on CraigsList to someone else.

The unintended part, though, is even better. Last summer, we were finding that we had to set the AC at 77 degrees and it still felt too hot in the house. The AC ran virtually non-stop and significant heat radiated from the ceiling all day long. At night we'd turn it down to 71 and still not be all that comfortable for bed. We were considering adding a second AC unit to help keep the upstairs comfortable.

Roughly half our roof is covered with solar panels for the pool now, and so a large part of that heat that was going into the house is now going into the pool. The result is that we now turn the AC to 77 at night and we're comfortable. During the day, we've been leaving the AC off entirely until late afternoon. The house gets up to around 85, and it's more comfortable than it was last year at 77. Last month, our electric bill was a full $100 cheaper than the same month last year, a roughly 25% reduction. Based on this alone, the system will pay for itself in around 15 years (figuring that reduction goes through the months we would normally have AC on), and we won't be spending the money on adding a second AC unit to the house since things are still comfortable. I also got into the attic yesterday afternoon to check things out - it was no hotter in the attic than it was outside, and we don't have a running attic fan.

Photovotaic solar panels still don't make a lot of financial sense given the ROI that gets to about the time I retire. But the water heating panels absolutely do. And that said, we're so happy with the improvement in the temperature inside that we might keep an eye out for some good options to cover the rest of the roof next year in photovotaics.

 

[Matthew]

Nice - maybe consider adding extra attic insulation, too.

 

[Ted]

Nice - maybe consider adding extra attic insulation, too.

That's an option over some parts of the house, but not most of it. We have vaulted ceilings.

 

[Matthew]

That's an option over some parts of the house, but not most of it. We have vaulted ceilings.

I had a vaulted ceiling on my first house, too. So I know what you mean.

 

[evapilotaz]

Move to AZ and you will have plenty of swimming days. Couldn't you have purchased a electric Heat Pump for you pool instead? Did you look into that option and compare cost with the solar panels?

 

[Ghery]

Another upgrade for you would be to modify the heat exchanger on your AC to have a water jacket. Plumb it so run pool water through it. The efficiency of the AC will go up and the waste heat will go to your pool. This has been done with great success in other parts of the country. So successfully that the pools got too warm.

 

[Ted]

Move to AZ and you will have plenty of swimming days. Couldn't you have purchased a electric Heat Pump for you pool instead? Did you look into that option and compare cost with the solar panels?

I looked into it and the pricing was in between natural gas and solar. I would also then still be paying money to heat the pool (although not as much as gas), so it really would not have been a good option.

 

[jsstevens]

Another upgrade for you would be to modify the heat exchanger on your AC to have a water jacket. Plumb it so run pool water through it. The efficiency of the AC will go up and the waste heat will go to your pool. This has been done with great success in other parts of the country. So successfully that the pools got too warm.

Used to help a lot. But now with SEERs up in the mid to high teens there's no waste heat to be had. We replaced our unit a few years ago. The old one had a waste heat recovery system on it which fed the hot water heater (a common installation on higher end homes in central Florida in the late '70's, early 80's.). I asked about it for the new one and got a blank look from the A/C guy. (You kids get off my lawn!) So I did some research online and found that they still exist, but don't get used much. I was told the "No waste heat to save." line. Once the new system was installed, I checked the high pressure line coming back from the condenser. (Just used my hand, nothing fancy.) It was barely above ambient temperature. They are THAT efficient at dumping the heat. The only way you could do it now is to incorporate it into the condenser unit to capture the heat between the compressor and the coil, which would void the warranty.

John

 

[Ted]

Another upgrade for you would be to modify the heat exchanger on your AC to have a water jacket. Plumb it so run pool water through it. The efficiency of the AC will go up and the waste heat will go to your pool. This has been done with great success in other parts of the country. So successfully that the pools got too warm.

We considered that as well. While it would've been about half the cost of the solar to install, it wouldn't have lowered our electric bill as much. We decided we'd see how well the solar worked on its own and maybe do the AC HX in addition if the solar didn't heat the pool enough. From what I'm seeing so far, it won't be necessary unless we want to turn the pool into a hot tub.

 

[RJM62]

I'm not sure why you'd want the water to be that warm... I always thought 70 to 75 was about right.

Then again, I grew up doing more swimming in the Atlantic Ocean than in pools; and because Robert Moses never installed heaters in any of the pools he built -- Caro and others have alleged that Moses thought cold water would keep Black people out of the pools -- even the water in the city pools usually didn't get much warmer than that.

(As an aside, based on my own research, I'm not convinced that that was Moses' intention at all. It's possible, but it's also possible that he just thought it would be impractical and too costly to operate. But that's way beside the point as touching upon the post.)

Back to the post in question... You may want to look into zoning your home's HVAC system so that the A/C only cools the bedrooms at night, and only the other parts of the house during the day. You'll basically need automated registers or duct dampers and an automated, zoned thermostat system. If you're running the A/C 24/7, the ROI should pay off the expense relatively quickly.

I do something along those lines, except I do it manually. I rarely need to use the A/C during the day because only the master bedroom and bath are on the second floor, where it gets hottest. The first floor cools nicely using just open windows on all but the hottest days. So once the heating season is over, I just close all the first-floor registers. On those two or three days each years when I need the A/C on the first floor, I open them.

This works fine for me because of the infrequency of days when I need to use the A/C during the day. But if I had to use it every day, as you seem to, I definitely would invest in the automated registers or duct dampers.

-Rich


-Rich

 

[kgruber]

I don't understand why refrigerators pump hot air into an already hot house. That should be vented outdoors.

 

[Alexb2000]

Are the panels on standoffs or direct to the deck? I would never install them without standoffs. Also how is your roof venting, especially at the ridge?

 

[FormerHangie]

We planted a tree on one side of the house. Now that it's taller than the roof it's made a noticeable dent in the summer electric bill.

We do have to clean the gutters in the fall, though.

 

[PaulS]

I don't understand why refrigerators pump hot air into an already hot house. That should be vented outdoors.

Just open the refrigerator door to cool it right down again.....

 

[Ted]

Good point on the zoning, Rich. We've thought about doing that as well and it will likely be a future upgrade.

 

[Ted]

Are the panels on standoffs or direct to the deck? I would never install them without standoffs. Also how is your roof venting, especially at the ridge?

They have standoffs. Our attic venting is decent, but we only have an attic over half the house. I was in there yesterday afternoon, it wasn't very hot - again, the solar panels.

 

[RJM62]

Good point on the zoning, Rich. We've thought about doing that as well and it will likely be a future upgrade.

It really saves a lot of energy, even the half-assed way that I do it. By closing the registers on the first floor, it only takes about 1/3 the time to cool the second floor, even though its footprint is only about 20 percent smaller than the first floor's.

My friend the engineer said this is because closing some registers increases both the volume of air coming out of the open registers, and its velocity moving through the ducts, which reduces the amount of ambient heat it absorbs while in the ductwork. So there's not only more air coming out of the remaining registers, but it's also colder air.

-Rich

 

[Ted]

In Pennsylvania I did poor man's zoning of sorts. In the winter I closed all the upstairs vents, in the summer I closed all the downstairs. Summer was cool enough that I could typically just open the windows at night and close them in the morning, that did fine. Cincinnati is far enough south that philosophy won't work as well, and our new house is designed in such a way that you'd not be able to simply open and close vents for AC, but we do tend to close upstairs ones off in the winter some.

I need to look into the zoning options, maybe for later this summer or into next summer.

 

[FormerHangie]

I'm not sure why you'd want the water to be that warm... I always thought 70 to 75 was about right.

Then again, I grew up doing more swimming in the Atlantic Ocean than in pools; and because Robert Moses never installed heaters in any of the pools he built -- Caro and others have alleged that Moses thought cold water would keep Black people out of the pools -- even the water in the city pools usually didn't get much warmer than that.

(As an aside, based on my own research, I'm not convinced that that was Moses' intention at all. It's possible, but it's also possible that he just thought it would be impractical and too costly to operate. But that's way beside the point as touching upon the post.)

Back to the post in question... You may want to look into zoning your home's HVAC system so that the A/C only cools the bedrooms at night, and only the other parts of the house during the day. You'll basically need automated registers or duct dampers and an automated, zoned thermostat system. If you're running the A/C 24/7, the ROI should pay off the expense relatively quickly.

I do something along those lines, except I do it manually. I rarely need to use the A/C during the day because only the master bedroom and bath are on the second floor, where it gets hottest. The first floor cools nicely using just open windows on all but the hottest days. So once the heating season is over, I just close all the first-floor registers. On those two or three days each years when I need the A/C on the first floor, I open them.

This works fine for me because of the infrequency of days when I need to use the A/C during the day. But if I had to use it every day, as you seem to, I definitely would invest in the automated registers or duct dampers.

-Rich


-Rich

Lap swimming pools are usually around 78 degrees. That's a little chilly for just splashing around. The pool I go to keeps its instructional pool at 82 degrees.

 

[Ghery]

Used to help a lot. But now with SEERs up in the mid to high teens there's no waste heat to be had. We replaced our unit a few years ago. The old one had a waste heat recovery system on it which fed the hot water heater (a common installation on higher end homes in central Florida in the late '70's, early 80's.). I asked about it for the new one and got a blank look from the A/C guy. (You kids get off my lawn!) So I did some research online and found that they still exist, but don't get used much. I was told the "No waste heat to save." line. Once the new system was installed, I checked the high pressure line coming back from the condenser. (Just used my hand, nothing fancy.) It was barely above ambient temperature. They are THAT efficient at dumping the heat. The only way you could do it now is to incorporate it into the condenser unit to capture the heat between the compressor and the coil, which would void the warranty.

John

Interesting. Thanks for the update. My suggestion was based on ancient information.

We considered that as well. While it would've been about half the cost of the solar to install, it wouldn't have lowered our electric bill as much. We decided we'd see how well the solar worked on its own and maybe do the AC HX in addition if the solar didn't heat the pool enough. From what I'm seeing so far, it won't be necessary unless we want to turn the pool into a hot tub.

Sounds good. Can't argue with success (although some people will try).

 

[Matthew]

I have an unfinished basement.

A couple summers ago I went through with foil tape and sealed all the HVAC and cold air return seams and gaps that I could find and get to. When I removed many of the registers, I could see a lot of gaps between the ducts and the registers that allowed airflow between the basement and the first floor, as well as the 2nd floor ceiling and the attic. Sealing those gaps, and all the other seams and openings that I could find, probably closed up the equivalent of a 12" diameter hole in each of the two circuits.

Also, I learned the trick of taking needle nose pliers and bending the vanes on those registers to direct air towards living areas rather than against a wall or into a corner.

All those little things helped.

I have marked with a Sharpie where all my basement air duct dampers need to be set for summer/winter to force more or less air to each level of the house.

 

[Alexb2000]

They have standoffs. Our attic venting is decent, but we only have an attic over half the house. I was in there yesterday afternoon, it wasn't very hot - again, the solar panels.

How about a radiant barrier of some kind, perhaps on the bottom of the panels? I can't see how this is anything but radiant transfer. They have paint, thin sheets, etc. that all provide a radiant barrier. Heck even tin foil must work, I see it on the windows in every trailer park.

 

[AggieMike88]

I have an unfinished basement.

A couple summers ago I went through with foil tape and sealed all the HVAC and cold air return seams and gaps that I could find and get to. When I removed many of the registers, I could see a lot of gaps between the ducts and the registers that allowed airflow between the basement and the first floor, as well as the 2nd floor ceiling and the attic. Sealing those gaps, and all the other seams and openings that I could find, probably closed up the equivalent of a 12" diameter hole in each of the two circuits.

Also, I learned the trick of taking needle nose pliers and bending the vanes on those registers to direct air towards living areas rather than against a wall or into a corner.

All those little things helped.

I have marked with a Sharpie where all my basement air duct dampers need to be set for summer/winter to force more or less air to each level of the house.

Sounds like you've been watching some of the Mike Holmes home repair TV shows

 

[Matthew]

Sounds like you've been watching some of the Mike Holmes home repair TV shows

Nope, not this time.

I was trying to get a quote to have some extra insulation blown into my attic (I'm getting too old to do stuff like that on my own). The guy came by, said, "Look. I can give you a quote right now, without even measuring since I've been doing this for so many years. But, why don't we take a look at first things first." We went through the house for about an hour, and he pointed out all the things I could/should do before adding extra insulation. I was glad I called.

 

[Ted]

Used to help a lot. But now with SEERs up in the mid to high teens there's no waste heat to be had. We replaced our unit a few years ago. The old one had a waste heat recovery system on it which fed the hot water heater (a common installation on higher end homes in central Florida in the late '70's, early 80's.). I asked about it for the new one and got a blank look from the A/C guy. (You kids get off my lawn!) So I did some research online and found that they still exist, but don't get used much. I was told the "No waste heat to save." line. Once the new system was installed, I checked the high pressure line coming back from the condenser. (Just used my hand, nothing fancy.) It was barely above ambient temperature. They are THAT efficient at dumping the heat. The only way you could do it now is to incorporate it into the condenser unit to capture the heat between the compressor and the coil, which would void the warranty.

John

I was under the impression that the newer systems took the hot freon before the condenser and ran it through the pool, and actually shut off the condenser for you as a result. But I didn't look into it very closely and made several assumptions there.

Water's around 85 or so now, was just in there for a bit. Might be pushing 90, who knows. Either way, we're plenty satisfied with the temperature so far. We'll see at the end of the summer, but I don't foresee us wanting to add any additional heat capability to the pool. We probably will at least look into what it would cost to cover the rest of the roof with photovotaics.

 

[jsstevens]

I was under the impression that the newer systems took the hot freon before the condenser and ran it through the pool, and actually shut off the condenser for you as a result. But I didn't look into it very closely and made several assumptions there.

Water's around 85 or so now, was just in there for a bit. Might be pushing 90, who knows. Either way, we're plenty satisfied with the temperature so far. We'll see at the end of the summer, but I don't foresee us wanting to add any additional heat capability to the pool. We probably will at least look into what it would cost to cover the rest of the roof with photovotaics.

If the condenser has a way to take the hot liquid just post compressor and before the coil that would work. I didn't turn that up in my research but that was about 8 years ago. They do produce a lot of heat. The older ones still had plenty after passing through the coil as well.

John


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[kyleb]

Our pool is surrounded by trees, so it only gets 5-6 hours of direct sunlight a day. We added a solar pool cover to see if it would help the pool warm up faster in the spring and stay warm longer into the fall. We've gained weeks on both ends. We also inherited a gas heater, which I won't use.

I think the real advantage of the solar pool cover (think bubble wrap) is that it greatly reduces evaporative cooling. The disadvantage? The cover is big and bulky, so can be a PITA to remove/replace. So we only use it in the shoulder seasons.

I'm thinking of buying a separate, smaller cover, for the deep end of the pool - we could leave it on most of the summer without impact to our pool use, and it would keep the pool a few degrees warmer, which would be nice given our usage patterns, which are pretty much driven by our 3 year old.

 

[RJM62]

Lap swimming pools are usually around 78 degrees. That's a little chilly for just splashing around. The pool I go to keeps its instructional pool at 82 degrees.

That would be much too warm for me. The few times I've been in heated pools (usually in hotels), I found them uncomfortable. I'd wind up taking a cold shower to cool off after the pool. The unofficial local swimming holes or the unheated, outdoor pool at the state park north of me are more my style.

I really think it has to do with what you got used to as a kid. We used to consider it "beach weather" when the water temperature at Jones Beach or Riis Park (depending on how much money we had for bus fare) broke into the 60's, which was usually a bit before Memorial Day. By late August, even the ocean seemed too warm.

Then again, I've also taken a few dips with the Polar Bear Club over the years, so maybe my water temperature preferences are a bit toward the left of the Bell curve.

The only heated pool I knew of as a kid was at the 9th Street YMCA in Brooklyn, and I'm not sure whether it was heated, per se, or was just always warm because of the glass roof. It was stiflingly hot in the pool area, like being in a greenhouse. I had a full membership (which cost something like $30.00 / year back then for kids), but I rarely went there in the summer.

-Rich

 

[Ted]

Kyle, we tried a solar cover for the pool. Yes, it definitely helps prevent evaporative cooling and probably gives you a bit of a greenhouse factor. We ended up deciding very quickly that it was ugly and we'd never get in the pool because of how much of a pain it was to use.

 

[Geico266]

I don't understand why refrigerators pump hot air into an already hot house. That should be vented outdoors.

And pull cold air in for cooling in the winter! I'm with you!

 

[Henning]

Back in the 80s I helped a buddy build a solar heater for his pool out of a 2M satellite dish and a tracking drive from a Mead Telescope. Took copper nickel tubing and wound it into a stainless cooking bowl, placed it where the LNB goes, an covered the dish with hex and pentagonal mirrors and put a pump in the system. The pool stayed warm in St Louis winter and when we added a heat exchanger to the HVAC system, his heating bill dropped to nearly nothing. All from repurposed junk (my buddy is a bigger junkyard scrounges than I am lol).

 

[KRyan]

Kyle:

I've got a co-worker here in Ohio that came up with a cheap solution to your same problem. He's got a pool in partial shade. He uses a bubble wrap cover, and has what he refers to as a "hillbilly heater." All it is is a coil of black corrugated hose that is attached to the output of the filter/pump, and then into the pool. He's got about a 30 foot coil of it in part of his yard that gets all day sun. He claims it raises the water temp about 10 degrees, which was the difference between too cold and just right. Cost was about $65.

 

[Badger]

My local utility just announced they want to increase the monthly fixed portion of customer bills from $10 to $50 and lower the cost per therm. That will kill many people's incentive to creatively conserve.

http://m.host.madison.com/ct/news/l...558a-9027-8d2ef45087ae.html?mobile_touch=true




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[Everskyward]

My local utility just announced they want to increase the monthly fixed portion of customer bills from $10 to $50 and lower the cost per therm. That will kill many people's incentive to creatively conserve.

http://m.host.madison.com/ct/news/l...558a-9027-8d2ef45087ae.html?mobile_touch=true

I love my new (and expensive) low-e windows even though they don't save me anything. I don't have air conditioning so my electricity consumption hasn't changed, however it's much more pleasant in the house in the afternoons. I should have done it years ago.

 

[comanchepilot]

So the true question is:

If solar is adopted on a wide scale, will it cause local cooling of climates since the energy which formerly struck the ground and heated the air is now being used to create electricity and is no longer available directly for climate purposes.

 

[CJones]

Have you thought of plumbing the solar panels into your interior hot water supply? Not sure if that is an option or financially feasible based on the ROI, but (so far) sunshine is free!

OR use it to add a little heat to your fancy new garage.

 

[comanchepilot]

Back in the 80s I helped a buddy build a solar heater for his pool out of a 2M satellite dish and a tracking drive from a Mead Telescope. Took copper nickel tubing and wound it into a stainless cooking bowl, placed it where the LNB goes, an covered the dish with hex and pentagonal mirrors and put a pump in the system. The pool stayed warm in St Louis winter and when we added a heat exchanger to the HVAC system, his heating bill dropped to nearly nothing. All from repurposed junk (my buddy is a bigger junkyard scrounges than I am lol).

Had a friend of mine with a well in a part of Connecticut where they brought city water - the wife insisted on the city water cause they had lots of iron whch meant lots of iron sulfide at times in the water .. ..

When he put in asphalt instead of a rock driveway he designed and buried 1/2" Pvc pipe, hooked it up to pipe extension from a part of the house, isolated it from the rest of the system and installed a hot water recirc pump from his pressure tank for the well, which he made bigger. starting in December when the ground started to freeze he turned that pump on - and it melted the snow falling and never had to plow his driveway. . . .pump added about $7 a month or so to the power bill - the only time he ever had a problem was with snow falls in excess of 12" - the it took about a day to melt it all - he made sure when they built the driveway it had a good swale away from the garage and the house - for your average 3-5" snow fall it melted on contact and never covered the driveway . just recirc the water back underground deeper than it came up -

Was a fantastic swamp yankee invention . . .

 

[Henning]

So the true question is:

If solar is adopted on a wide scale, will it cause local cooling of climates since the energy which formerly struck the ground and heated the air is now being used to create electricity and is no longer available directly for climate purposes.

That is something I brought up years ago. I think if harnessed on a world's only source scale, that yes, there will be some issues in the climate from reduced convection. I think that as it is most efficient to use in this format to just transport heat energy from one place to another very locally, and in that, even at the large scale there would be minimal environmental impact.

 

[Matthew]

So the true question is:

If solar is adopted on a wide scale, will it cause local cooling of climates since the energy which formerly struck the ground and heated the air is now being used to create electricity and is no longer available directly for climate purposes.

I got into that argument with my kids about windmill farms. If we build too many, they will use up all the wind, we'll have global warming, and polar bears will starve. So windmills kill polar bears.

The best they could come up with was, "I don't think it works that way."

 

[Ted]

I love my new (and expensive) low-e windows even though they don't save me anything. I don't have air conditioning so my electricity consumption hasn't changed, however it's much more pleasant in the house in the afternoons. I should have done it years ago.

That's pretty much the same as it is for us. We weren't using the gas heater, so it's technically not saving us money in that regard. It is saving us money on AC as mentioned, and the pool is more comfortable. So, it's worth it anyway.

If we had a reason to go for new windows, we'd absolutely go for the newer style like what you did.

Have you thought of plumbing the solar panels into your interior hot water supply? Not sure if that is an option or financially feasible based on the ROI, but (so far) sunshine is free!

OR use it to add a little heat to your fancy new garage.

Basically it would be a second system if we wanted to go with a hot water heater for the house. I have a friend with such a system around here, and he loves it. However to do it properly, you're basically pre-heating the water before it gets into your tank. So you get a second water tank, it gets heated by the roof to around 90F, the heater takes it the rest of the way. The way our house is set up, that would be more difficult to implement and would take up space in our storage room, which is already too small. So, not really an option. Maybe good for you in Jawjuh where it would probably heat your water the full way!

The garage is heated - two infra-red heaters that run 220V and plug in when needed. I should insulate the doors. So I think the photovotaics make the most sense if we decide to finish the roof off.