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Old 04-24-13, 03:59 PM   #11
ELGo
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I remember a fellow telling me that he built a "wall of water" on his southern wall for the effect you are hoping for. The trick is to well shade the wall during the daytime in the summer.

The winter is a problem though, because the wall temp will tend towards the median daily temperature outside, and that is cooler than your home.

All in all, I am not a fan of thermal storage. I think PassivHaus design, meaning passive solar and cooling with excellent ventilation and air quality management is the way to go.

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Old 04-24-13, 04:55 PM   #12
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How deep in the ground is your basement? if it is much below grade, the milk jug mass would be best set up there, near the wall area below grade and on the floor. Water does an awesome job at leveling out air temperature, given enough surface area. With this type of arrangement, air could mingle between the individual jugs well. The jugs would be out of the sun, so heat gain wouldn't be an issue. They would draw the "cold" from the walls and floor well if not very insulated below grade, not so well if insulated well.

However, heat rises and cold falls, so you would need to move the cold air upstairs. Like razor said, you could move the air with your furnace blower by routing an existing duct to a low point on the level. I would suggest using a small fan (300 cfm or less) to suck air from the low point and exhaust it into your central air ductwork. When the central blower isn't running, the small blower would blend the cool air at the bottom with the warmer air above, drawing some warmer air from above slowly into the basement. When the central system kicks on, the cooler air in the ductwork would be the first to arrive where it is needed.

I have a setup like this running between the main level and the second story of my home. I rigged a HEPA air cleaner to the lone central vent upstairs so that it blows warm air down into the central ductwork below. Using this blower, along with my window a/c unit turned air source heat pump, I found that my heating needs are being met down to about 45F by the heat pump alone. This winter, I estimate I have saved over $1000 in natural gas bills at a cost of around $300 in electricity! Before adding the blower rig, the window heat pump did a good job of keeping the upstairs warm, but the gas heater still ran more than it needed to.
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Old 04-24-13, 05:23 PM   #13
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I like that idea, if I could create "columns of water" 5 feet tall that could sink any heat into the ground with plenty of space in between these columns. for air to freely go through. What would make an ideal column? Five gallon buckets would be easily sourced but the small contact between two buckets would be less than ideal.
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Old 04-24-13, 05:56 PM   #14
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Quote:
Originally Posted by scottorious View Post
...I could create "columns of water" 5 feet tall...
Why don't you just live in the basement during the summer?

I think that's what any self respecting, simple, stone age human would do.

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Old 04-24-13, 06:02 PM   #15
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My dog(labrador) would hate being stuck in the basement all day(no windows to look out) and he would pretty much hate life in an 85 degree house. I am considering sleeping down there anyway. I am still holding to the idea that if I could use electricity at 3 am when its around 3 cents a KWH I could pre-cool my house and my thermal mass to cruise through peak demand times.
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Old 04-24-13, 06:06 PM   #16
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Quote:
Originally Posted by scottorious View Post
My dog(labrador) would hate being stuck in the basement all day(no windows to look out) and he would pretty much hate life in an 85 degree house. I am considering sleeping down there anyway. I am still holding to the idea that if I could use electricity at 3 am when its around 3 cents a KWH I could pre-cool my house and my thermal mass to cruise through peak demand times.
Perhaps, but then you would close off your home to the free cool outside air.

In my climate, I ventilate my house like crazy at night, and then put effort in preventing the house from heating up during the day.

Shade, insulation, shade

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Old 04-24-13, 06:21 PM   #17
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I'm just musing ....

You have a temp gradient in your home, from colder at the basement floor, to hotter at your ceiling.

How about a pipe with a fan in it that collects air from the basement floor and deposits it at the ceiling ? You might end up with a reverse chimney.
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Old 04-24-13, 06:25 PM   #18
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opening the windows is always an option if it looks like the temperature will drop to a comfortable level. I just wrapped up an experiment with a single gallon of water in a plastic jug. With my picaxe I logged data points at every minute for the last 3 hours to track how much heat a gallon might absorb just sitting in on a chair. The graph isn't perfect to read but the water started out at 48 degrees F which was from the tap. In 3 hours it rose in temperature to 58 degrees with the ambient air temp at a pretty consistent 68F. The other line that holds at 62F was a third temp probe that was just resting on the side of the jug. The probe in the water was roughly dead center of the jug. Raising 10 degrees in 3 hours absorbed 80 BTU. If this scaled up in the same manor that would be roughly 80,000 BTU in total or a bit over 26,000 BTU an hour. 26,000 BTU an hour seems like a nice help to the central air. I know in the summer it would be difficult to get water to 48 overnight. However I think the 20 degree temp difference could be achievable. Diurnal temp swings in July can be about 20 degrees. Just opening the windows late at night could feasibly remove a large portion of the heat boosted by the central air at off peak rates.

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Old 04-25-13, 11:44 PM   #19
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I don't think your notion of cooling at night is going to save you money. I am only reasoning here and relying on my experience at home, so I may be off ...

Homes have quite a bit of thermal mass themselves. If the home thermal mass has not reached low ambient temperature by the AM, it implies that there is unutilized mass, and adding more is not going to make a difference.

In my home, I open all the windows for night ventilation AND run a whole house fan, yet my home AM temperature is at least 5F above the outside night time nadir. As summer progresses my interior nadir temperature slowly rises. This is in part from mean temperatures rising, but it is also my home's thermal mass that slowly increases in temperature despite my best attempts to cool it down at night.

Now, you have a choice to cool the home thermal mass and water with AC, but as you run the AC more, the inside-outside temperature difference increases and thus so does the loss of energy to the outside.

This really sounds like a case where one hand gives, the other takes.
----

I'll also mention that your quite optimistic scenario of collecting 80k releasable btu (net) in the 1000 gallons of water is equal to about 2.5 -3 kwh of electricity a day using the AC in the usual manner if the AC's COP is about 3.0.

I'll all for saving energy, but even I would draw the line at 1000 jugs of water in the house for 3 kwh a day
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Old 04-26-13, 01:48 AM   #20
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I use a program called power smart pricing (powersmartpricing.org) and I pay rates that vary greatly. As an example I used a day in the heatwave we had last year. june 29 had prices as low as 1.9 cents per KWH which occured for 3 hours during the early morning. During peak demands prices jumped to 9 cents per KWH. here is the link to that graph. Hourly Prices for Wednesday, December 31, 1969 : Power Smart Pricing /29/2012&display=table so if I could use thermal mass to shift when I use the AC....that is WHEN I use the A/C, I could save quite a bit of money. Even if I still ran the A/C the same amount or even a little more than I currently do but at hours that are off peak I could save money. I'm not trying to get anything for free just attempt to slow heat gain down so I can use the A/C at 3 am instead of 3 pm. Pre-cooling with a decent amount of mass sounds like a feasible way to make that happen.

Explain what is optimistic about my 80,000 BTU estimation. if 8 pounds raises 10 degrees in 3 hours why would 1000 pounds of water in 8 pound containers not raise 10 degrees?

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