Domestic solar water heating purposes ?

[Externet]

Hello.

A roof mounted solar water heater can be used in several configurations, as

-Preheating the electric/gas domestic water heater inlet

-Providing direct warm water to use points

-Work in parallel to electric/gas water heater

-Fill an insulated reservoir with warm water for demand moments

-With heat exchanger

-Combinations of the above

 

They have their good and their bad; unless a bunch of flow diverters/valves are implemented in the piping circuits. That brings complexity, cost and attention depending on season, time of day, temperature reached...

 

Trouble with colder than utility supply in too cold weather/nights/early morning.

 

What is in your opinion the best piping layout for 'average' latitudes ? No canadian colds, no equatorial tropics.

[DrP]

I do not know what the 'best' layout would be.. and I am not sure what it is exactly you want.... but I wrote a tech pamphlet once for a firm that was selling installations. Not sure if this is what you want, but here is what I know (which might not be that much..)

 

For optimum heat transfer they used copper pies painted black which had been flattened to increase the surface area of the pipe exposed to the sun. The pipes ran zigzag through/on a black metal backing board which further helped absorb heat and transfer it to the pipes.

[Externet]

Thanks, DrP.

Yes, it is poorly worded from my part.

 

The pipes going to and coming from a roof solar water heater can be hooked in many configurations to a household piping, to obtain different applications as listed.

Can anyone suggest a more convenient one ? Or, how would you hook it ?

 

DrP: on a side note, am just curious of how that firm you dealt with, handled protection against freeze-bursting of copper pipes.

[DrP]

Good question Ex, I am not totally sure. I can take a guess though.... these systems are only meant to compliment an existing system, as you stated, the can be hooked up to your current hot water supply to pre heat it - thus you do not need to heat the water as often..... I would guess that in the cases where you might get freezing pipes that a convection current of moving water around the system as a whole would keep it free from freezing... although it does seem kinda counter intuitive on days like that as you are actually loosing nett energy by warming the pipes..... Maybe you can cut off the system and drain the loop that goes outside on such days where freezing/energy loss would be a problem... What do you think?

So in short then - just an idea - you could have the outside loop as an optional addition which can be switched on and off by a ball valve - it shouldn't be too hard to drain or refill. (and this could be automated pretty simply to drain and refill when the temperature is right)

Edited October 22, 2015 by DrP

[J.C.MacSwell]

I do not know what the 'best' layout would be.. and I am not sure what it is exactly you want.... but I wrote a tech pamphlet once for a firm that was selling installations. Not sure if this is what you want, but here is what I know (which might not be that much..)

 

For optimum heat transfer they used copper pies painted black which had been flattened to increase the surface area of the pipe exposed to the sun. The pipes ran zigzag through/on a black metal backing board which further helped absorb heat and transfer it to the pipes.

How would flattening of the pipes effect their pressure rating? I am assuming they are used at the same pressure as the rest of the system for household use.

[Externet]

-When using a solar heater to pre-heat the main heater inlet-

 

If the pipes are of some flattened elastic tubing that will expand when freezing allowing 10% extra room; the bursting gets solved. Not a simple find in the building materials stores. Their durability and reliability from fatigue comes also to play. And must be ultraviolet/weather resistant

 

I have no problem dealing with the freeze expansion now; I was just curious of how others would tackle the problem.

 

My unsolved part is the blockage that ice in the solar heater pipes does to flow towards feeding the main heater inlet, and the extra insolation time needed to melt and restore flow. Plus an initial much colder ice-melt water the main heater has to heat up.