Solar Energy - Solar thermal/hot water heater tour/details Enerworks

[garveynj]

I would love to see some reading on a bright sunny day to see how hot the glycol loop runs compared to the cold tank temp then you could see hom much extra out put you could get out of this system

[RimstarOrg]

@garveynj It was a cloudy day and the pump didn't start up at all. He also had a slow pressure loss issue, probably why he hadn't insulated it yet. That said, the piping is as it's supposed to be for this commercial system. I understand what you mean by the thermosiphoning issues (pipe size and type of heat exchanger) but this is a highly engineered system design with a lot of happy customers so it probably isn't as efficient as you'd guess. You bring up some good points though.

[garveynj]

looking at the gauges in the video I am seeing 25C income hot from collectors and 23cold out of collectors and the water tank side cold of about 18C the cold out of the heat exchanger should be within 1 or 2 degrees C of the cold side of tank or the heat exchanger is not working very efficiently

[RimstarOrg]

@garveynj Like I said, it was cloudy that day and he was having some pressure issues. I think I recall he even told me to ignore the gauges.

[garveynj]

also plate heat exchangers are not recommended for thermosiphoning applications due to there small passages and high restriction shell and tube style is much more free flowing.

[garveynj]

That system is designed wrong for proper thermosiphoning and the plastic pipe between the solar storage tank and water heater is a very bad idea also why did whoever installed this never insulate the piping between the tanks and a lot of other pipes on the cold side too. Conduction will make the cold pipes hot when no water is used and waste heat.

[RimstarOrg]

@garveynj I agree regarding the lack of insulation. I pointed it out to him when I was there and if I recall correctly he said he just hadn't put it on yet. Now that I think of it again, I should have mentioned that in the video. I'll add an annotation and/or something to the description. Re the way the thermosiphoning is done, what do you think is wrong with it?

[garveynj]

@RimstarOrg For thermosiphoning to be efficient you need large pipe diameter the pipe going to the top of the tank if undersized causing the heat exchanger to run hotter making the glycol loop have to run hotter making the collectors less efficient because the have to run at a higher temperature. normally for the thermosiphoning is brought into the too the side of the tank to prevent it from getting air bound

[garveynj]

@RimstarOrg but since you use the same pipe to connect to the aux water heater air bound wont be a problem but you don't need an expansion tank on the city side at all because the city side is an open system expansion could in theory flow all the way back until it was forced back into the water tower unless he wanted it to prevent shock loads such as water hammer it is unneeded.