Solar Pool Heater Idea - Asphalt w/PEX!

[atomlinks]

I live in northern ohio and want to build a diy solar pool heater. I have seen the solar systems that you can buy, but they don't seem like they will do the job well or last very long.

Here is my idea:
-Build a 4'x40' "table" stick built with pressure treated plywood for the top.
-Run PEX line throughout the top
-Pour 1inch layer of asphalt over the plywood/pex(I will run cold water through PEX during asphalt pour)
-Insulate underneath plywood with 1/2 inch XPS

My thought is that the asphalt absorbs heat well and will completly surround the PEX for max heat transfer. I want to build something big enough to heat the entire pool. Plan would be to raise it 1 1/2 feet above the ground, completely surrounded by wall block behind the pool running the entire length of the pool+concrete pad. I told my wife it would look like a planting bed...with asphalt instead of mulch

A few questions:
Is this big enough?
How/where do I connect this contraption to the return line?
Any other inexpensive ideas other than plywood that might last longer, hold the weight of the asphalt etc?
Has anyone ever heard of/attempted such a thing?
Would this work, or am I crazy?

This is my first post on this forum, still in the planning phase of my first diy inground pool. Still undecided about pool size, either 16x32, 14x28, or 12x24 all standard hoppers and max of 6foot deep end(High water table).

 

[zea3]

Hi, welcome to TFP! I can't tell you whether or not your idea would work, but since it sounds like an expensive undertaking you may want to try building a small working model to test it out if you don't get any feedback on your idea.

 

[duraleigh]

Being direct, that will not work. 4' x 40' is too small for the pool you are contemplating and the logistics of supporting, installing and applying that much asphalt would simply overwhelm you.

I can't remember but I think asphalt is delivered at around 350-400 degress so even if you figured a way to get it on (and not collapse) that platform, I don't think you could run enough cold water through the pex to keep it from failing.

I have seen the solar systems that you can buy, but they don't seem like they will do the job well or last very long

Why do you think that?

 

[X-PertPool]

My father built a DIY solar system that worked fairly well. He used 3/4" black poly pipe in coils on a roof. The coils were in a box covered by old sliding door glass. The whole box was maybe 4'x8'. The enclosed glass box helped a lot with gathering more heat. Regardless a real system works much better and is easier to fix when there is a leak. When it comes to solar it's all about moving the water quickly through a large surface area. This usually means multiple small diameter pipe (think of how actual solar systems are made with very tiny tubing spread flat across a surface)

 

[atomlinks]

Thank you for your feedback. I first was looking at the panels that you can buy like this:
http://www.ebay.com/itm/4x20-Solar-Pool ... 0924653547

From the description, I would need between 4-6 of these 2'x20' panels @$100-$150 each. The cost is decent but I don't want to get into a situation where I am replacing them from year to year. There are many brands out there and some of the reviews that I have been seeing say they may need to be replaced every few years.

I am hoping to find/construct something that would last > 20-30 years with little maintenance.

 

[jblizzle]

Welcome to TFP!!!

I agree with the others that it is nearly impossible today to build a DIY heater that is as effective and costs less than the commercial solar panels.

If you properly care for them, there is no reason to have to replace them every year. You just need to ensure that you open them up and drain all the water our before winter so that there is not water in them to freeze and split the tubes.

That said, I think your expectations are a little overly optimistic as not much these days lasts 20-30 years with little maintenance.

 

[Isaac-1]

When it comes to solar, and thermodynamics in general there are many "common sense" assumptions that are either wrong or backwards. For example the question of using a glazed or unglazed collector, "common sense" and many reports would suggest that a glazed collector (glass covered box) would work the best, but thermodynamics that this is only true if there is a large temperature gradient between the environment and the water temperature, (usually more than 20 degrees F) If the water is within about 20 degrees F of the ambient and there is little or no wind then a cheap unglazed panel will out perform the glazed box. As to the service life of common plastic solar panels, many of the premature failures we see reported can be directly attributed to incorrect installation (expansion rubbing, stress points, etc.) , or abuse (allowed to freeze with water in the panels, and over pressurization). People also have different definitions of problems, some people consider a small leak that required tightening a hose clamp to repair a failure, others would call it a routine maintenance adjustment, this likely has to do with if they are the type to pay for an expensive service call, or simple turn a screw a quarter of turn themselves. I am not going to say that common plastic solar panels will last you 20-30 years without maintenance, but I will say that people here with proper installations seem to report 5-10 years of service before substantial issues tend to appear.

 

[atomlinks]

The tube thickness of the commercial solar systems ... Do they tend to be pretty thin? If so, is this where leaks tend to occur after 5-10 years of use? It sounds like smaller tubes with thin walls would absorb and transfer more heat than a thicker/larger material, but might not last as long.

I like the idea of the coil within some type of transparent enclosure. That seems like a good idea. I'm starting to think that asphalt might not be the best idea at this point. I was trying to think of an inexpensive material that holds heat and would transfer to the pipe well.

 

[Isaac-1]

Thickness of the commercial panels varies considerably, partly depending on type of construction (individual tubes or extruded panels) If you read the spec sheets from a few different companies and look at the weight of the panels of matching size you will quickly see there is a lot of variation. For example I have 4x12 Techno-Solis brand extruded panels which weigh 30 pounds each dry, compare this to another popular brand that uses a connected tube style 4x12 panel like the AquaTherm panels sold by Elm distributing which weigh 22.3 pounds dry. Many of the DIY kits use thinner panels so they can be rolled tighter to ship through UPS, etc. instead of being palatalized and shipped truck freight like the stiffer / thicker panels. As to the topic of glazed box, be aware that these can gather as little as half the heat of a common unglazed panel when water is near the ambient temperature (think early and late traditional swim season when the daytime highs are in the 70's and nights are in the 50's and 60's)

Ike