dear all,
please, advice, I have this idea in my mind for long time. And now with gas costs up, it pushes me to investigate. So I search here for kind advice, first comments.

Idea is that to heat a house during winter with the solar energy from outside. I would place solar collectors, heat water, on the outside of the house, on the wall. I would connect it with pipe to the inside radiator, placed higher on the wall. Magic is sun would heat water in the collector outside, hot water would circulate up, and so to the inside of the house, after cooling, it would go down, and back outside.

I made very simple drawing, trying to explain.

Goal would be to help heat the house during winter. There should be no maintenance needed. Closed system. Should be as cheap as possible and easy to install.

Thanks for any comments, advice, tips...

(I am from Slovakia, not from Wisconsin, but there was no such option to pick) But I have a friend in Wisconsin which I also visited


[ibb.co]


Siviu



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There WILL, repeat WILL, be maintenance.

+ You will need 'automotive' antifreeze as freeze protection

+ You will need an expansion device (open tank) to controll expansion of heat transfer fluid - said tank connected to top of the system (? in attic ?) also acting as air vent

+ You will require LARGE pipe size (? 2"+ ?) for convection flow

+ Any thermostat placed in-line will overly restrict the 'gravity flow'

+ You will STILL require conventional heat for the coldest days when the sun is NOT shining and at night

IMO: not practical for a retrofit


BEST OF LUCK

==============================================

"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638



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your theoty is correct.
my question is "will the sun warm the entire solar panel so the temperature at its top is the same as its bottom?"
i don't know how much temperature differential you will need to create convection ?
as pointed out you will need to account for expansion.
i believe 1 inch pipe would be sufficient in size.
remember that in order for convection to work the loop has to lose heat. the temperature difference is what moves water around.

please let us know as this goes along.

lastly.. the pipes should be sloped. up for the hot side and down for the return side.

insulate pipes on the hot side and no insulation on the return side.

good luck

thanks a lot for comments. see below my observations

There WIL, repeat WILL, be maintenance.
S: Well, should be minimal to none if possible. I was thinking, the pump is major item to maintain, so I focused to avoid it. I might be wrong.

+ You will need 'automotive' antifreeze as freeze protection
S: Yes, I was thinking about it. Should be a closed system, stable for years, maybe 5 years, than replace the coolant.

+ You will need an expansion device (open tank) to controll expansion of heat transfer fluid - said tank connected to top of the system (? in attic ?) also acting as air vent
S: This one I omitted totally. But for sure is needed. I would still try to make it part of the radiator inside the house. To go to attic, it complicates everything a lot, more pipe, more cost, hard to install...
How big it should be? How many gallons? 3 gallons outside radiator, 3 gallons inside radiator, 3 gallons expansion tank next above the radiator? Probably there is a formula to calculate expansion tank to the quantity of water used.

+ You will require LARGE pipe size (? 2"+ ?) for convection flow
S: 2 inch is a lot, but to make run well, why not. There is no limitation. It will increase amount of water.

+ Any thermostat placed in-line will overly restrict the 'gravity flow'
S: Yes, should large one, as it is in the car. But, is the thermostat needed? I thought, thermostat is needed to stop water circulating during night, or when water temperature is too low. Or how would it behave when cold water?
Same during summer, there should be a way to take it out so it does not heat the house? But probably you can not just close it, or it will explode, right?

+ You will STILL require conventional heat for the coldest days when the sun is NOT shining and at night
S: Yes, we have gas heating entire house, in the floor, works perfect. But, gas, due to war, is very expensive. So I am searching for way to decrease costs, consumption of gas.

IMO: not practical for a retrofit
S: Yes, looks like not easy to make it practically work. I wanted it to be an iPhone style solution. So simple and intuitive.

Again, thanks for you comments.

There WIL, repeat WILL, be maintenance.
S: Well, should be minimal to none if possible. I was thinking, the pump is major item to maintain, so I focused to avoid it. I might be wrong.

+ You will need 'automotive' antifreeze as freeze protection
S: Yes, I was thinking about it. Should be a closed system, stable for years, maybe 5 years, than replace the coolant.

Quote

System needs to OPEN to atmosphere at the expansion tank

+ You will need an expansion device (open tank) to controll expansion of heat transfer fluid - said tank connected to top of the system (? in attic ?) also acting as air vent
S: This one I omitted totally. But for sure is needed. I would still try to make it part of the radiator inside the house. To go to attic, it complicates everything a lot, more pipe, more cost, hard to install...
How big it should be? How many gallons? 3 gallons outside radiator, 3 gallons inside radiator, 3 gallons expansion tank next above the radiator? Probably there is a formula to calculate expansion tank to the quantity of water used.

Quote

1/2" pipe to tank - top of tank open to atmosphere - tank initially filled 1/3 vertically - 3 gallons would be a good starting point (tank CAPACITY = 9 gallons)

+ You will require LARGE pipe size (? 2"+ ?) for convection flow
S: 2 inch is a lot, but to make run well, why not. There is no limitation. It will increase amount of water.

Quote

1-1/2" would probably also work

+ Any thermostat placed in-line will overly restrict the 'gravity flow'
S: Yes, should large one, as it is in the car. But, is the thermostat needed? I thought, thermostat is needed to stop water circulating during night, or when water temperature is too low. Or how would it behave when cold water?
Same during summer, there should be a way to take it out so it does not heat the house? But probably you can not just close it, or it will explode, right?

Quote

A 1/4 turn ball valve anywhere in the 'loop' will stop/regulate circulation, BUT, without VERY COMPLEX controls will require MANUAL operation.

+ You will STILL require conventional heat for the coldest days when the sun is NOT shining and at night
S: Yes, we have gas heating entire house, in the floor, works perfect. But, gas, due to war, is very expensive. So I am searching for way to decrease costs, consumption of gas.

IMO: not practical for a retrofit
S: Yes, looks like not easy to make it practically work. I wanted it to be an iPhone style solution. So simple and intuitive.

Quote

A 'hot box' exterior 'collector' with a solar powered fan to circulate the heated air into the interior .....................

==============================================

"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638



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Not Practical is right. Water will start moving with a 7 degree temperature change but now you're talking a 50% glycol antifreeze solution. The reality is the up-front-cost to do it the right way will take 20 years just to break even. You're going to need circulator and you're going to need a large storage tank. If you're going to head down the rabbit whole, you better bring your check book.

Antifreeze coolant, not that expensive, 25 liters, 100 EUR, you mix it 1:2..., so should be ok. We get max -15 in winters.

I am thinking about expansion tank, if the radiator inside is big enough, if it is not filled up to the top, it can work as expansion tank, right? Would be sort of two in one

Crazy idea-

Also question of how much heat can it bring? During winter? Lets say it gets 3 hours sun shine, there is 20 gallons of water, will it heat it to 120 Fahrenheit?

Thanks for answers

How would this work? A 'hot box' exterior 'collector

Is it metal based, aluminum? The air would be taken from exterior of from interior?

We have installed on the house the air recycling unit. It is supposed to change air without loosing the heat. See model below, we have an older one. Works very well, we just change filters. It has a heater inside, so it does not freeze during winter.

[www.komfovent.com]


But it is installed on the other side of the house, no sun shine there.
Otherwise could be reused, to blow hot air inside the house. the pipes goes to each room

thanks a lot

Quote

I am thinking about expansion tank, if the radiator inside is big enough, if it is not filled up to the top, it can work as expansion tank, right?

System MUST be totally filled to establish 'gravity' / convective circulation.

You are confusing (as do many others) an expansion tank (open gravity circulation system) with a compression tank (closed pump driven pressurized circulation).


A solar collector can be built in a shallow box shape from a sheet of plywood + insulated polystyrene + copper sheet painted matte black + glass top using 2x4s as sides.

Add two ducts one connected at the top and one at the bottom to the inside and a solar powered fan to move the heated air .... voila.

Your mileage may vary ....... IOW: best of luck

==============================================

"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

if you have aluminum in the piping system make the antifreeze is OK for aluminum.
the pipe going to the expansion tank only needs to be 1/2 inch. i can run uphill/downhill it doesn't matter. the expanding water will move back and forth in a pipe connected to a tank regardless of the direction of the slope.

ditto

==============================================

"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

Although they are not common, we have passive solar installations in California, primarily for heating pools. They typically pump pool water through coils or grids of black pipe to collect heat. Sometimes they put glass over the collectors, which admits visible light but retains infrared, to heat the coils further. This is cheap and effective for 5-10 degrees of heating. Some roofs have two or three coils, each 10 feet/3 meters in diameter.

Of course, these systems heat the pool water directly. The challenge for heating a home would be heat transfer from the water to the air inside the house.

here is a link:
[www.energy.gov]

Some off-grid homesteaders are looking at systems like this because they are simple and require very little energy input to run the pump.



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