Solar panels vs DIY coils

[kenandshari]

This started out as a question on another thread, but was moved to its own thread, so I edited it in hopes of getting a good discussion going on the subject. We're looking to add a few months to the swimming season. I'm looking at the Sun Grabber solar panels, vs DIY coils, vs the Extend a Swim wood burning pool heater http://www.warmwatersolutions.com/

I'm specifically not considering an electric or propane because the operating costs appear high. Someone let me know if I'm way off here.

DIY Coils pros:

initial appearance is relatively cheap to make
simple concept

DIY Coil Cons:

you have to build it
it may not work
trial & error process
appearance on roof

Soar pros:

Virtually hands free operation, set the pump timer and forget about it.
Almost free operation: free sunlight, and already running the pump about 8 hours daily for water maintenance.
Relatively low cost for the kits: Sun Grabber kits with 5 panels (4' x 20') are about $1100-$1200 on ebay with shipping.
Our home has a large roof area, house is positioned right for solar (back yard faces South), full sun almost all day long (7-8 hours daily)

Solar Cons:

Freeze concerns: According to the mfg site, the panels need to be removed and stored from the roof prior to the first frost of the season.
Putting up and taking down annually seems like it would add extra wear & tear, and must be planned out-akin to holiday decorating tasks.
You need sunlight and semi-warm days to collect heat.
No way to maintain or gain heat on demand.
Seems to be a limit on how much temperature you can gain.
Needs lots of roof area to do the job properly
Requires holes to be made in a relatively new (5 year old) roof & shingles that do not currently leak.
appearance on roof
weight on roof

Wood Fired pros:

Simple installation: place it on a quickcrete pad & connect water in and water out pipes, (appears DIY in a few hours)
Install it and leave it.
Simple operation with no moving parts to break (firebox & heat exchanger)
Heat on demand (relatively speaking) day or night, clouds or sun. - so you can plan to use the pool.
Ability to superheat water and transfer it to pool, theoretically bringing the temp up hotter faster.
No holes in roof
Don't have to breakdown and store before freeze/frost
drain & bypass to winterize: this amounts to turning a couple of valves and opening a drain plug.
free firewood (I'd have to cut my own)

Wood Fired cons:

Stoking the fire several times daily.
Cutting wood to burn.
Smell from stove pipe smoke.
Heater location: not particularly unsightly, but needs to sit 3' away from any structure which would put it out in the middle of the side yard for us (mostly unused space that currently houses the pump & filter pad)
appearance in yard
Cost about $2500 -$3000 depending on size (Large or XL)


As far as freezing goes, we have an outdoor shower and 4 hose bibs all attached to our brick home and have never had any freeze issues with any of these. We've never needed to do anything to them to "winterize". We live in an area where sunlight and firewood are both plentiful. Steps from my yard I can cut all the free firewood I want, and we've already had a few 80+ degree days here in Savannah. I'm interested to know what you chose and how it is working out. Would you do it again and what would you do differently? Thanks to all who reply.

Split off of DIY solar heater questions. JasonLion

 

[JasonLion]

Commercial solar panels will be dramatically more efficient than anything you can build yourself, and unless you are getting most of your materials for free the commercial panels will cost less per amount of heat gathered as well.

If you are thinking about firewood, keep in mind that wood fired pool heaters use really dramatic amounts of wood. In many common situations you could easily use a cord of firewood in less than a week.

 

[bk406]

If you are thinking about firewood, keep in mind that wood fired pool heaters use really dramatic amounts of wood. In many common situations you could easily use a cord of firewood in less than a week.

And if anybody is interested, here is a picture of how much a cord is. IMO, heating a pool with wood is not practical.

 

[Bama Rambler]

BK, that looks like a half a cord to me. but since it's split, it may be a cord.
A cord of wood is 128 cuft, 4' high x 4' wide x 8' long, or 4' high x 2' wide by 16' long. Regardless, that's a lot of wood.

 

[bk406]

BK, that looks like a half a cord to me. but since it's split, it may be a cord.
:

Dave,

I got the pict of the net as a full cord, but i was thinking the same thing. As you said, its a LOT of wood and is the reason heating a pool this way is a daunting task to say the least.

 

[mas985]

Just a few comments

Freeze concerns: According to the mfg site, the panels need to be removed and stored from the roof prior to the first frost of the season.
Putting up and taking down annually seems like it would add extra wear & tear, and must be planned out-akin to holiday decorating tasks.

I think that is unique to Sun Grabber. Most manufactures don't require you to remove the panels in the winter. If you install a vacuum release valve in the proper location and make sure that you do not have a local low area such that the plumbing and panels are self draining, most panels should survive the winter just fine.

No way to maintain or gain heat on demand.

With any solution, you will want a solar cover to not only maintain heat but to limit evaporation. A heated pool will have much more evaporation than a non-heated pool. Also, any heater will have it's limits as to how quickly a pool will be heated. The largest wood pool heaters shown here has a maximum output of 150k BTU/hr. Assuming 20% heat loss, this heater would only raise the water temperature about 0.6 degrees per hour.

Seems to be a limit on how much temperature you can gain.

The temperature rise is limited more by air temperature and wind than anything else. Heat loss over night is a big factor as well which is why a cover is helpful. I can easily get my pool well over 90 degrees with solar and I can heat my spa to 105 with just solar.

Ability to superheat water and transfer it to pool, theoretically bringing the temp up hotter faster.

Besides being dangerous, that would also be less efficient than pumping water through a wood heater. Higher water temperature leads to more heat loss so the resultant pool water temperature would probably be less than if you just pump water throught a heat exchanger. This is why solar panel efficiency decreases with lower flow rates. Lower flow rates increases the water temperature in the panels and also the heat loss from the panels so less BTUs are added to the pool.

 

[learthur]

Dude! You want an electric air source heat pump. You just don't know it yet. Or go all out and put in a ground source one large enough to heat your home also.....but that is pricey.