# Solar water heater -2



## budgetprepp-n (Apr 7, 2013)

I did a post a while back about using a automobile radiator to build a solar water heater.
I see that someone brought that post back to life.When I did that post I got a lot of negative
feedback of why it wouldn't be a good idea. OK I'm going to try again and explane why I know 
it will work. I been thinking about this for a while now. 

Ok think of a radiator mounted on a piece of plywood with wood 2x4s on all sides surrounding
it and a transparent cover over it. Like a radiator in a box with a transparent side facing the sun.
Everything would need to be painted flat black to help increase the amount heat absorbed. 
It will have the same effect as a car with the windows rolled up in the summer in the sun. Your not 
just using the sunlight for the heat but also the heat in the box using the heat from the contained 
ambient air. This would heat even the back of the radiator. Everything in the box would be heated
from the hot air even where there was no sunlight. It would have 1" space from the back of the box.

As for the amount of surface to absorb the heat a radiator has many cooling fins. That would give it a
huge amount of surface for collecting and transferring the heat to the water as compared to say just
tubing ran back and forth. It would be like adding fins to the tubing to give it much more surface.
If you close at a it a radiator it has what looks like 5/16 or 3/8 flattened tubes with fins attached. 
That's why the radiator is so good at cooling the water from the engine as air passes through it.
That same surface would collect heat instead of dispersing it.

With no air flow to cool the surface of the fins it would work in reverse the fins would absorb the heat
and transfer the heat to the water. 

Circulation? OK if you ever put your hand up next to the ceiling when heating in the winter then you 
know the air is a lot hotter than the air next to the floor. that's because eat goes up it doesn't matter if 
it's contained in water or air it allways goes up and cold water or air allways goes down.

A radiator has two openings that look like pipes about the same size as the radiator hose one in the
top and one in the bottom. A tank would be mounted above the radiator with two outlets one in the
bottom and one in the top. The top outlet in the tank would be connected to the top radiator outlet
and the bottom outlet of the tank would be connected to the bottom outlet of the radiator using 
tubing about the same size as a radiator hose for the top and bottom. 

As the water was heated it would rise to the top of the radiator and continue to rise up the top pipe and 
into the top of the water tank. The hot water would want to reside at the top of the tank the cooler water
would flow downward down the bottom pipe into the bottom of the radiator where it would stay until it 
was heated up and then it would begin it's natural coarse upward as it was heated to complete the cycle. 

This is all based on simple natural phizicks < How in the word do you spell that ? 

For circulation the radiator box would be mounted standing up leaning back a little towards the sun.

The tank would hold about 10 to 20 gallons and would need refilled as used I don't think this heater would
keep up if cold water was introduced as you were using it and I don't think it would do well in cold weather 

Note: I leave spaces in my post to make it easier to read if your eyesight isn't perfect like mine.

Ok so what am I over looking?

I am not offended if you criticize that's how we learn sometimes.


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## Kauboy (May 12, 2014)

All I can say is, try it.

I'm still not convinced that ambient air temperature will impart very much heat to the fins of the radiator, regardless of the color of the surrounding box.
I'd like my understanding to be proven wrong. It would open up more possibilities, and that's always good.
I'm just not sure it will work out the way you hope.


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## dsdmmat (Nov 9, 2012)

I think you will have more luck circulating a tank full of water through a 100 foot black hose left out on the roof during the heat of the day. When we would go to the field in the desert we would place black 5 gallon water cans on top of our ridged shelters in the morning and by mid afternoon the water would be the perfect temp to take a shower. 

For your box wouldn't you want to put reflective material around the inside of the box to reflect the heat back toward the radiator? It sounds like a great experiment and you never know until you try.


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## budgetprepp-n (Apr 7, 2013)

dsdmmat said:


> I think you will have more luck circulating a tank full of water through a 100 foot black hose left out on the roof during the heat of the day. When we would go to the field in the desert we would place black 5 gallon water cans on top of our ridged shelters in the morning and by mid afternoon the water would be the perfect temp to take a shower.
> 
> For your box wouldn't you want to put reflective material around the inside of the box to reflect the heat back toward the radiator? It sounds like a great experiment and you never know until you try.


Rather than reflect the sunlight I would think it would be best to absorb the light (and heat ) using flat black
long ago before the days of air conditioning police cars had the doors and top painted white to reflect the
off the car. That's where two tone police cars came from


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## Kauboy (May 12, 2014)

budgetprepp-n said:


> Rather than reflect the sunlight I would think it would be best to absorb the light (and heat ) using flat black
> long ago before the days of air conditioning police cars had the doors and top painted white to reflect the
> off the car. That's where two tone police cars came from


I think he means on the inside of the box.
If the top panel is clear, and there is any gap around the internal radiator, you would want to line the interior walls of the box with reflective material to redirect arrant rays back toward the radiator itself.
The exterior of the box should indeed be black, but painting the interior black would cause the box's wall to absorb heat, and not properly conduct it toward the radiator.


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## budgetprepp-n (Apr 7, 2013)

Kauboy said:


> I think he means on the inside of the box.
> If the top panel is clear, and there is any gap around the internal radiator, you would want to line the interior walls of the box with reflective material to redirect arrant rays back toward the radiator itself.
> The exterior of the box should indeed be black, but painting the interior black would cause the box's wall to absorb heat, and not properly conduct it toward the radiator.


You might be right, But keep in mind the sunlight is not what we are trying to gather.
What we are trying to gather is the bi product (energy) from the sunlight, in the form of heat.
We need to heat the air inside the box to heat up the radiator. If the inside walls absorb the heat that would
in turn heat the air in the box. And I would think that would help keep the radiator hot.
We need hot air so the radiator fins can absorb it.

Humm, Just a thought might help in insulate the outside of the box to help keep the heat in.

The foil would also be reflecting some of the sunlight back out of the box. 
Does that make sense to anyone but me?


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## tinkerhell (Oct 8, 2014)

if you have a way to create hot air, why are you heating the water instead of pumping the hot air into the house? furthermore, it seems to me like the hot air system should be much more massive.


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## Kauboy (May 12, 2014)

budgetprepp-n said:


> You might be right, But keep in mind the sunlight is not what we are trying to gather.
> What we are trying to gather is the bi product (energy) from the sunlight, in the form of heat.
> We need to heat the air inside the box to heat up the radiator. If the inside walls absorb the heat that would
> in turn heat the air in the box. And I would think that would help keep the radiator hot.
> ...


Yeah... see I still keep trying to divert you away from the idea that the ambient air is going to do anything to the radiator, or water inside.
You need direct rays hitting that radiator from all sides, not hot air.
You know this, to some extent, or you wouldn't worry about a clear top.


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## budgetprepp-n (Apr 7, 2013)

Kauboy said:


> Yeah... see I still keep trying to divert you away from the idea that the ambient air is going to do anything to the radiator, or water inside.
> You need direct rays hitting that radiator from all sides, not hot air.
> You know this, to some extent, or you wouldn't worry about a clear top.


that's a good point


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## paraquack (Mar 1, 2013)

I don't remember what state you're in but do you have to worry about freezing? All commercial 
units I seen use a potable antifreeze with a heat exchanger in a tank just before the hot water 
heater and a small pump to circulate the antifreeze. It appeared that they used copper pipe 
inside the "roof box" with everything painted black. My bro-in-law had a system with multiple 
roof boxes. Each had an aluminum sheet in the box that was bowed to create a reflector with 
only a few pipes in the focal area of the reflector, and the group of boxes were connected to a 
sun tracker. The pump was on a photoeye to shut off during the period of darkness so as not 
to pump heat back out into the cold. Down here in AZ, I see a lot of homemade, plastic pipe 
(painted black) solar heaters for swimming pools. They tie into the filter pump. Even the 
campground had one with maybe 500 ft of pipe on the rec room roof.


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## A Watchman (Sep 14, 2015)

paraquack said:


> I don't remember what state you're in but do you have to worry about freezing? All commercial
> units I seen use a potable antifreeze with a heat exchanger in a tank just before the hot water
> heater and a small pump to circulate the antifreeze. It appeared that they used copper pipe
> inside the "roof box" with everything painted black. My bro
> ...


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## Montana Rancher (Mar 4, 2013)

Here is a variation and IMO a more cost effective and productive unit, there are a lot of different youtube ideas, even a person that heated water using the

dun dun dun (used for theatrical enhancement)

The Beer Can Solar Heater






enjoy


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## paraquack (Mar 1, 2013)

A Watchman said:


> paraquack said:
> 
> 
> > I don't remember what state you're in but do you have to worry about freezing? All commercial
> ...


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## Montana Rancher (Mar 4, 2013)

paraquack said:


> A Watchman said:
> 
> 
> > So it's been in the low 60s during the day and down n the 40s at night. Pool loses a lot of heat when we have clear skies, which is most of the time.
> ...


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