Glycol heater system problems

[LucMan]

How was the system working before you lost pressure? If OK then proceed with repairing the leak, flush the system with clean water until it comes out clear. If you get any chunks or flakes flush with Rhomar Water Hydro-Solv. Refill with Rhomar Rhogard Solar Guard glycol and hope for the best. You can go to Rhomar's web site for procedures and spec's.
Good Luck

[spareparts]

It works pretty good when it's full of fluid. I live in the mountains in northern New Mexico, our highs would be in the low 30's and on a sunny day the system could get the living room up to 72.

Something I thought of from my HVAC days, can I use temperature differentials to get an idea of the efficiency of this old unit? Would it tell me anything useful?

[J.P.M.]

It works pretty good when it's full of fluid. I live in the mountains in northern New Mexico, our highs would be in the low 30's and on a sunny day the system could get the living room up to 72.

Something I thought of from my HVAC days, can I use temperature differentials to get an idea of the efficiency of this old unit? Would it tell me anything useful?

You sure can and it's not as conceptually difficult as it is a PITA in a practical sense, but possible. I've done it many times.

Unfortunately or otherwise, you'll need more than temp. differentials to est. system efficiency, but you're on the right trail. You can get a lot of useful information with two thermometers and a way to measure flow rates. However, getting a reasonable estimate of the energy input (the solar energy) is usually a challenge, depending on how much accuracy you want. Without some appreciation of how that input is calculated and how it changes, even before talking about clouds and atmospheric variation, most guesses about irradiance are useless and misleading.

But, overall, it's a simple concept: System eff == Output/Input

For input you'll need some way to determine something called "Plane of Array" irradiance. That is, how much solar energy is crossing a plane parallel to the panels. That will usually and commonly require knowledge of something called Global Horizontal irradiance (GHI), and some way to translate the more commonly available GHI to POA irradiance.

The GHI is found with something called a pyranometer. The transform from GHI to POA irradiance is available, but a bit complicated to go into in this format. See Duffie and Beckman (The solar energy bible) or Google.

To estimate output you will need some way to measure the system flowrate, such as a rotometer and two (or more) thermometers to measure temp. differences at points determined by what you want to include in the efficiency calc. For example: To measure only collector efficiency, measure the fluid temps. at collector inlet and outlet. To measure overall system efficiency, measure the fluid temps. immediately before and after the devices (radiators ?) that deliver heat to the dwelling or to storage if it exists. Doing so will give you something called "instantaneous" (but not really if over an hour) efficiency or efficiency over short periods of maybe an hour or so. To get day long efficiency, you'll need some way to get integrated day long values of all the POA irradiances, temps. and flowrates over the time when the sun is shining on the collector.

For system efficiency, however you want to define it as describe above, divide the system output for any instant (or any time integrated period) by (the product of the POA irradiance * the collector aperture area) for the same period.

BTW, I lived in Albuquerque for several years and spent a fair amount of time rooting around NM north of Santa Fe and Taos and up in the Jemez. Prettiest place I ever lived/roamed around in,
and about the best solar climate on earth.

[spareparts]

It's a small world. I live in Los Alamos, my wife is the brains of the family and is doing a postdoc at LANL. Some amazing places to see up here. I've got some pics of double rainbows at the caldera from this last fall.

Thanks for that detailed description. Might be a little advanced procedure for me at the moment, though

[J.P.M.]

It's a small world. I live in Los Alamos, my wife is the brains of the family and is doing a postdoc at LANL. Some amazing places to see up here. I've got some pics of double rainbows at the caldera from this last fall.

Thanks for that detailed description. Might be a little advanced procedure for me at the moment, though

Double rainbows are fairly common around there to my experience. I've seen a few strong triples - one w/ a180 deg. arcs, but they usually don't last that long.

I appreciate that the procedure I described is a PITA. My purpose in describing some of what's involved is twofold: Provide some info if anyone wanted it, and maybe disabuse a few of those who may be led to false conclusions by thinking it's only about temperatures.

There were (are ?) a lot of solar thermal systems in/around NM.

Back in the day, LANL, among other things, did a lot of work on solar thermal (see, Balcomb, et. al.). That later mostly morphed into NREL.

Also, being about the best solar climate in the U.S., the area attracted a lot of solar advocates (and more than a few '60's burnouts it seems to me). Put those together and the result is a lot of residential solar installs, some well designed and engineered, some of them sort of proof of design things, some closer to wet dream redneck engineering. But all that seems to be part of what makes the Land of Enchantment what it is. Of the systems that worked, the passive designs seem to have stood the test of time better than the more mechanically complicated ones.