Black and White Issue

[whoose]

While riding the chair lift at our local ski hill yesterday a I told a friend about my water wall. He said good idea but you need to put something black behind the 1 gallon jugs. I know a little Physics and I said to him that the light has already passed through the water and would only be absorbed by the black background. I suggested white or shinny silver. He said no and suggested I watch some YouTube. Got to the top of the hill. Who is Correct and why?

[UFXEFU]

What is the purpose of the water wall?

[Ricky Shaw]

One reason would be to moderate temps. The jugs heat up in the day, and would radiate that warmth back at night.

[whoose]

To lower the high temps (summer) and raise the low temps (fall and spring).

[Hellmanns]

The black would absorb the lights energy in the form of heat, and radiate the heat back to be absorbed by the water.

[Worth1]

I have no idea who is right.
What I do now is what we see as light does not heat up anything.
IR wave lengths heat up stuff this is the solar radiation we dont see but feel.
Stones brick water and so on absorb IR light.
Aluminum and gold will reflect it.
So you have two choices stack bricks behind the jug to absorb the IR readiation or put up aluminum to reflect it back into the room.

Also if you have it you have black plastic containers one of the ways you can keep them cool it to paint them with silver paint shade them or wrap foil around them.
A big sheet of aluminum behind a radiant heater works wonders reflecting heat back into a room instead of it going into the wall.

Worth

[Cole_Robbie]

Painting the jugs themselves black would make the water warm up the fastest during the day. Clear jugs will pick up heat from the air as the greenhouse warms during the day, but not very much from the sunlight directly. Try two of them side-by-side and you will see.

Also, if you are using electric/gas heat, the wall of water can actually increase the time that your heat has to run in the morning. A lot depends on the exact conditions and cloudiness, but a "heat sink" should be more appropriately termed an "energy sink." If your goal is to increase temperatures, and that water is cold, it's going to work against your efforts to raise temperatures.

[Ricky Shaw]

Probably too hot, but the biggest impact would be spray painting the jugs black. A good test, spray one jug, compare it's temp at the end of the day to a clear one.

[Ricky Shaw]

Cole Robbie is obviously a genius.

[BigVanVader]

Plus the jugs will last longer

[UFXEFU]

Originally Posted by whoose

To lower the high temps (summer) and raise the low temps (fall and spring).

I don't see them doing both raising and lowering temps. Back to the black and white issue. Black will absorb more heat than white. Black absorbs heat and white reflects light, therefore less heat is absorbed. Maybe black in winter and white in summer.

Bob

[whoose]

Lower the high temps in the heat of the day and raise the lows in the early morning by shifting the heating and cooling curves. Also less peaks and depressions on the curve.

[Cole_Robbie]

Originally Posted by Ricky Shaw

Cole Robbie is obviously a genius.

As a narcissist, I am incapable of disagreeing. That doesn't make either one of us correct, though.

Mass is great, but it has its own difficulties. The heat released will be at its max right when the sun sets, and then slowly decrease over the night. The coldest part of the night is 4-6 am or so, and at that time, the mass is releasing its lowest level of heat.

Let's say the night got down into the 30s. Your jugs of water might be in the 40s at sunrise. Let's also say your electric heat is set at 60; and furthermore, for the sake of this hypothetical, it's a cloudy morning. Say you had two greenhouses that you wanted to heat to 60 degrees. One was empty, and the other had a wall of water jugs at the temp of 40 degrees. Which one would take longer to heat?

Cold mass works against heat, just like the old-time iceboxes used to work before there were refrigerators. If you put food in an insulated box with a big chunk of ice, then your food will stay cold.

[Worth1]

That's exactly why your refrigerator wont run as much if it is full of beer.

worth

[whoose]

I have decided to go with silver sided 1" 4X8 foot insulation boards. I will let you know how this works out.