I’ve got this great idea for a home-built solar pool heater. I plan to construct a solar box out of plywood, 2x4s, and plexiglass. Inside, I had originally planned to run copper pipe, manifold-style, creating a huge heat exchanger, and plumb it in-line with my pool filter. Lately, however, I’ve been thinking about an even more efficient form of heat exchanger - a couple of huge (truck?) radiators.
The one question I haven’t figured out, tho…can an automotive-type radiator withstand the mildly corrosive (chlorinated) pool water?
I may be mistaken, but I believe modern radiators are made by bonding aluminum fins to copper coils. If that’s what you’ve got, then you’ve got no problem. Copper has the best resistance to chlorine corrosion of any readily available tubing. Even some grades of aluminum are OK, but I’d try to find out more about the radiator if it has aluminum tubes.
There are chemicals which replace chlorine, if you choose. They are more expensive and less corrosive (to people and equipment).
To prevent corrosion in metal: The pH must be maintained! This is the single biggest corrosion issue with metals. Alkalinity kills one kind of metal, and acidity kills other types. pH is the thing to be monitored.
Metal plumbing survives in the home, and the water is chlorinated, yet it is pH balanced.
A genuine pool heater would cost anywhere from 500-2000 dollars. That might be the best bet.
I think a couple of factors other than chlorine - total alkalinity and PH might play a big part. The PH for obvious reasons and the total alkalinity because of the buffering action when it’s at the proper level.
Although chlorine is certainly a reactive element,the two pool chemistry seminars I attended concentrated on PH as the main item affecting pool plumbing corrosion.
ricepad I am knowledgeable about solar heating but I do not understand your OP. A vehicle radiator will not work well at all as a heat collector if that is what you mean (I am not sure)
As far as building heat collectors, yes, you can, but I do not see why you would want to when you can buy them already made. If you were closer I’d give you some that I am not using.
In any case, make sure you design the whole thing correctly.
For thirty bucks, you can buy a clear plastic cover which turns your pool into an effective greenhouse during the day, and keeps the heat in at night. Much cheaper than any of the rest
Thanks, TNTruth, Diver, and sailor for your responses. I hadn’t considered that modern radiators are copper with aluminum fins. I also had forgotten about the importance of ph in the whole equation.
But sailor, why don’t you think my idea will work? By my reckoning, it’ll get to about 200 degrees F inside the solar box. With the radiator inside the solar box, it should absorb a fair amount of heat, right?
I’m intending to build my own because commercially-available collectors are too friggin’ and I have no place to put one, and the ones I’ve seen are too expensive, too. I figure I can make my own for less than $200.
Car radiators are designed to transfer heat between water and air. That means lots of thin fins sticking out to increase contact area with the air while keeping the overall size reasonably compact.
But with a solar water heater, you want the radiator to absorb as much sunlight as possible, and not lose the heat to the air. Which means maximizing the area lit by the sun (i.e. maximizing the overall size), and minimizing the area not lit by the sun (i.e. smooth flat shapes, no fins). So the ideal water heater is a very large flat tank, painted black. Or even better, a transparent tank with the inside bottom surface painted black, so that the black surface is in direct contact with the water. That’s not very practical though. A reasonable compromise would be a big metal panel painted black, with copper pipes welded or soldered to it.
So you see that the black PVC pipe idea and the ‘clear sheet over the pool’ idea, already posted, are very close to ideal. A car radiator would be ideal if you wanted the water to warm up to the temperature of the air and not any higher, but a well-designed solar heater should get a lot more heat into the water.
Disclaimer: I am not an engineer, I have no sense of practicality, I’m just speaking as a scientist who’s thought a lot about heat transfer lately.
I should also mention that the ideal solar water heater is also the ideal radiator (i.e. device for cooling the water) at night. You are going to shut off the flow at night, and drain it in winter, right? The radiator can get much colder than the air, and in winter the water will freeze and rupture the pipes. I know that can be hard to believe, but think about this - when the heater is facing the sun which is hot (6000 degrees), it can get hotter than the air, right? So when it’s facing the night sky, i.e. the cold of deep space (-270 degrees), it can get colder than the air.
I must not have been clear in my OP. The radiator will be inside a solar box. Since the ambient temperature inside the solar box should be around 200 degrees F,and the radiator will be inside the solar box, wouldn’t you think that would raise the temperature of the water?
well, I am not going to tell you not to do it. Just let me know how it goes. My impression is that anyone with a good technical knowledge of the subject can see it it not going to be very efficient. I think you are trying to save money the wrong way. Solar panels are engineered and built for their intended purpose. You can build an installation using other stuff but my guess is that the yield will not pay for the installation or your labor. Do the math. It would probably be much more efficient to paint the bottom of the pool black.
I know people hate math but you have to do the numbers. Anything else means nothing but opinions. I keep listening to people go on and on about how great alternative energy sources would be if only there weren’t that vast conspiracy against them. The one thing all these people have in common is they do not have a clue about the numbers involved (and, frankly, they don’t care). Wishful thinking is not reality.
I’d like to see some realistic numbers regarding the cost of the project and what kind of energy you expect to get out of it. And I’ll be happy to play devil’s advocate.
I do not think it can come even close to the efficiency of a conventional solar panel of equal surface area. I’d like to see the theoretical analysis and the actual results.
Elsewhere on the boards I reported that my silver ring was
completely blackened by overchlorinated water, and even one
of my gold rings got a little spot on the bottom of the shank, which I attribute to a trace of welding material or whatever jewelers use. Before you say my rings must be fake, let me point out that they were bought from a reputable independent retailer of LONG standing.
Yesterday I finally got around to getting a jar of Goddard’s Silver Dip, and after soaking for a half hour in this compound, my silver ring came out white, but a lot less lustrous than it used to be. I think the corrosion was so bad that it pitted the surface.
