Shop solar heat problem!

[varmint]

A couple of years ago, when one of my brothers had to re-roof his house, he hired a crane to remove 5 large solar heating flat panels, and decided to not to re-install them. A friend and I took a truck and trailer out to the midwest, and came back to Maryland with the 5 6' x 8' panels, 2 120 gal. water storage tanks, the oil-to-water heat exchange module, spare parts, 15 gal. of synthetic heat exchange fluid, a fill-pump rig, etc. I mounted two panels on my shop roof, and using a circulator pump, heat the oil when the sun shines, pump it thru a Nascar oil cooler (another frustrating story about Ebay) with a computer rack cooling fan behind it and get cheap space heat. I love measuring 135 degree hot air blowing out, all for about 100 watts of electric power for the fan and pump, and a few watts for the controller.

Here's my problem: the system requires an expansion tank, of course, and I can't find one anywhere with a bladder that's compatible with the fluid. I have borrowed the tank (made by Amtrol, with a hydrin bladder, for the original manufacturer back in the 80's, but no longer available) that came with the salvaged system, but my friend will be needing it when his system, which will heat water, gets finally installed. It was part of the exchange module, and he has dibbs on it. The oil, called Brayco 888, is no longer available, but is ideal for the application- non toxic, non-corrosive, stable, good heat transfer characteristics, etc., so I would like to use it. But, the system can go from whatever the low temp. is, 0 degrees is possible, to a high of 300 when the system stagnates in the summer, so expansion control is a must. I have searched the internet for a hydrin exp. tank, to no avail. Butyl, the common material, won't hold up for long. I am going to be desperate for ideas next fall. A few pictures (taken before completion) should show the system basics.
Thanks for any ideas! (an air pressure riser won't work- the oil will oxidize and mix with the air) and using a regular tank will cause failure and contaminated oil. Using another fluid presents problems, but I hear that the Brayco oil is valuable in the SW, where a lot of Novan system were installed.

 

[GT2]

Why not buy your friend a new "water" tank and keep the one you have?

 

[magicheater]

Why not just run a 50/50 glycol/water mix? That is what we do here in the mid west. Usually we just put it in the floor and use a 12 volt pump and a photo voltaic panel to drive it. Pretty fool proof system. Of course you would have to dump the heat somewhere in the summer.....

 

[MikeD74T]

Use two tanks. A 20 pound propane tank for the oil & T'd off that an Extrol tank. Put nitrogen, heluim, or argon between the oil & one side of the extrol tank. Air in the bladder. Mount the propane tank inverted with oil going into the normal fill end (now the bottom). Weld a T onto the propane bottom ( now the top) & drill a hole into the tank. Connect the extrol to the end of the T and a schraeder valve to the side of the T to charge the inert gas side. If you want to get fancy weld some pipe couplings to the side of the oil tank, cut thru with a holesaw, and get sightglasses ( from Grainger, McMaster-Carr) to monitor oil level. Wish I could show a drawing??? MikeD74T

Or just use one larger tank & charge with 1/2 oil & 1/2 inert gas (from welding supply). You could even use propane for that small amount & in an oxygen free environment.

Lots don't realize that before antifreeze it was common to use light oil as a coolant in gasoline/diesel engines.

 

[AHNC]

I was in the solar business 30 yrs ago and used the brayco 888. While it is a great and stable fluid it is a giant pitX to deal with and was distinctly unprofitable. Its viscosity is such that it will leak where nothing else will and I know how to put pipe together. It will eat anything in its path. As I recall, and I may be wrong, it required viton eveything.

I'd suggest you check with the standards of todays closed loop systems and not have to deal with Brayco 888. If it is a problem now, it will continue to be in the future.

 

[varmint]

I agree that Brayco oil is a giant pain the butt, and it will leak somewhere in a screwed joint no matter how careful you are. I sold and installed a bunch of Novan systems in 1982-83 (back when we had a great tax credit, totaling 60% between the Feds and the state, if I remember right) and I must have been younger and stronger then, because I never had any leak issues- carefull 95-5 solder joints, and meticulous screwed joints- but my present install has one leak that will make me drain and redo one joint. The glycol-water blend won't stand the high temperatures, or so I am told, so that won't work. Yep, viton o-rings are required, and a hydrin or viton bladder. I am going to think about the two-tank idea. I will be talking with an engineer who has some experience with this, and hopefully will figure something out. If I can get $100/gal for my oil, that would be an incentive to switch, but to what???

 

[forgeblast]

What about those pressure tanks for wells, will the mix your running now eat the bladders?

 

[slowzuki]

Just charge a non-bladder overfill tank with nitrogen so you won't have the problem with oxygen. If needed you could use a refrigeration vaccum pump to remove most of the oxygen in the tank before charging.

 

[dodge man]

If you google "Brayco Oil" you will get several hits. It looks like it has aviation applications, but I'm not sure its the same stuff.