what is eath coupling?
whe well water coming in should be at that temp say 50 degrees. That would be warm enough wouldnt' it.

btw the roof might improve with some kind of insulating cloth on the inside. Reflectix? does any one know of something. I've heard I can add r7?

Greendreams,
Are you nuts? Guys like you and Tesla jusy don't understand what you can see with your own eyes! The Earth is flat dude! <;-P
Your underground water storage container is as close to free as you can get. Mine was fifty bucks. 10,000 gallon Fiberglass, and strong enough to trust with gasoline
underground. I saw a local gas station removing their fuel tanks from the ground. They sold me two of them for $100 dollars. Check with 'local' companies that remove fuel tanks.
They will be thrilled to save a bundle by selling you one cheep! Even two!
Now, lower earth temps tend to be stable. This is partly / mostly due to the Delta T therom.
If 1 inch of dirt is at 45 degrees, and the next inch is at 46 degrees, then the third at 47 degrees, it will take a long time for the 45 degree dirt to reach 46 degrees.
As you move from one inch to one foot of seperation, the system begins to stabilize. The ground begins to 'relax' and losses stabilize.
But I understand what these guys are saying. If it is your mission to simply greatly improve your heat control, there are very good 'standard' ways of doing it.
If however you are doing research, then be prepared to make mistakes. Edison said he could show you a hundred ways not to make a light bulb.

Dana, I must ask you to explain this better. Beyond the vaporization issue,
*** … if you use water rather than dirt as your storage medium. The specific-heat of soil varies with soil type, but is universally much
lower than that of liquid water.***
My issue is not with the specific heat of the solution, but *with the resulting state of change*. This is important.
(If I was not specific about that before I apologize. My mind is small and difficult to multitask with.) I can store much more energy in sand (dirt) than I can with water
because water will change state long before sand will with high joule insertion. Boiling anything in this tank, change of state, is undesireable, and it will take a lot of
heat to boil sand... That is the point. I can raise a single tanks temp to remove the necessity for more tanks, as lond as the material does not change state.
My limitation here is op temps of plastic pipe and Fiberglass, long before a change of state with sand..

True, water becomes a cumbersome storage medium around 212F. But it is great at anything less.

Nothing prevents one from bringing the earth temps to the house (vs burying the house in the ground). You can run well water through the outer parts of the walls so that your interior heat loss is the equivalent to it being ~45F outside (direct use geothermal). But this has been discussed with the conclusion that more insulation is simpler and more cost effective.

(vs burying the house in the ground).
I've talked of this before. I might be doing this if I can put together the finances to pull it off. With large screen TVs as they are, for the difference in the price of siding and roofing installation and maintenance, you could install one in every room. Watch TV, or simply use an outdoor camera to transmit the local view. Or go online and put the Golden Gate Bridge outside your house, or a Fla beach in the winter. Add solar stored heat (dirt batteries) and solar pipes and you wouldn't know you were thirty feet below ground, or care that the outside temp was 12 below. Add maglev cars that travel at 200 MPH 20 feet above ground and life is good! As long as they still have chocolate!

Ya my current plan is multi year. I am doing research I guess because this land allows a main house and a tiny cabin, and all I've built is a tiny cabin. in year one I am going to improve the insulation,insulat the basement floor, install radiant heating, do the wiring to make it heated by well water. I bet you I can make it so the baseboards never kick in. In year 2 I Install a tank and thermal solar because I think it will need it. Just to bring the well water up a few degrees. In year 3 I start working on the goal of keeping this (and all buildings I eventually build at room temp all the time. This will require a large underground heat storage system for each building.

so the real advantage of dirt is that you can bring it to more than 212f. Hmm I need to play on strengths, better get out the magnifying glasses. I wonder if sandy stuff is best or 'rammed earth'.

That is a great point. One of the answers to say, a small backyard would be HOT sand.

I am thinking that sand being small pieces of rock, would transfer heat better (easier) than dirt. Not sure which would store more energy, but as long as I do not transend the melting temp of either, sand would more easily give up and keep the temp in balance amoung the medium. But as long as whatever medium you use is free ... I live next to Lake Erie, so I can get 'boatloads' of free sand around here. I would fill my 10,000 tank with the stuff laced with copper tubing to draw it when needed.

I guess the coper tubing is needed twhen plastic will melt. so how do you get anything 300 degrees hot?

I will use a Fresnel lens (probably 100 of them) focused on a flat black painted copper tubing encased in a glass covered box attached to a solar tracker to keep the Fresnel in alignment with the sun. The internal tubing temp will be monitored by the computer and when the antifreeze reaches 300 degrees F circulator pumps will kick in sending the hot fluid to the tank and replenishing it with cold to restart the cycle. I may use variable speed pumps for this so the fluid constantly feeds. The computer will speed up or slow down these pumps depending on the collector output temp. A bit more sophisticated, but it might be worth the extra couple of hundred bucks ... research. I figure we can run this thing March through December here in NY based on the solar intensity, possibly even all year, although there are few sunny days around here in Jan and Feb. But there are a few. I probably will not do that because of snow build up, or maybe adding a simple automobile windshield defroster to remove snow when viable. Solar light controlled obviously. (I sure do not want to climb on the roof to clean off the collectors. My car windshield is bad enough!) Then, when heat is needed in the house, an attached line and return with circulator pump will pump heated fluid from the ground tank into a heat exchanger inside my furnace system just like an air conditioner. I'm expecting this collector to run about $5k to $10k itself. I doubt if it will go any higher based on Fresnel and copper prices today. I had thought about modifying the collector pipes to include aluminum instead of copper to speed heat transfer, but I think that may be unnecessary. I know there are those out there who pooh pooh this, but I will make this challenge. Focus sunlight with a good Fresnel lens on the back of your hand and hold it there for one minute any time of the year and I will rethink this design. Tough guys excluded.

Storing anything at high temp for long periods of time has huge R-value problems, and spending putting the insulation budget into the (relatively modest temperature) house, not the storage will render storage the problem moot.

And generating/handing the high temp medium is also fraught with inefficiencies & losses. Your thermal losses right out of the front end of your fresnel-concentrated collector is off the charts inefficient. (It might be OK if you're operating in a vacuum instead of air at pressures that can sustain mammal life though.)

Really guys, do the math- this is off the deep end! Even if you could turn that into 300F sand, how much insulation do you think it would take to keep it above 100F for even a week when buried in 50F dirt, let alone months? This is not difficult thing to calculate. Start with how many square feet of surface area the tank or dirt-cube has, and the delta-T, and calculate how low the U-value needs to be to lose only 25% of the heat in 1000 hours of standby. Then calculate the necessary R value as 1/U.

And the amount of heat stored in 300F sand for a fixed volume is still less than you'd have in the same volume of 150F water (which also has huge R-value issues for long term storage.)

Have you calculated your BTU/hr INPUT from all of those TVs in your underground home? Seems to me you'd have a serious COOLING load to remove that heat rather than a HEATING load.

Seriously folks- MATH IS YOUR FRIEND! The cost of the copper heat exchangers & insulation to store a heating season worth of thermal energy in 10,000 gallons of hot sand is many times what it would cost to build a house sufficiently insulated to not need a heating system at all. I haven't run the numbers, but from just the order of magnitude alone you may be running out of headroom on melting temps of other materials than just PEX if that's going to be your approach- your copper is gonna crap out at around 2000F, but depending on the type of sand it may be already a puddle of glass well before then, even if you COULD insulate it sufficiently to not lose the majority to standby loss.

But if you don't even start running the numbers with pencil on the cigarette pack or lipstick on a mirror you'll be forever in the dark about just how far off the deep end you've gone here. Where the decimal point is matters.

Seems to me you'd have a serious COOLING load to remove that heat rather than a HEATING load.


that seems to be a cool spinoff of this radiant underfloor heating system I'm installing. You can also cool with it using well water. Now if I was clever I'd use that warmed up water I have to flush out as a heat source for next winter.

(that idea would need heat exchaners as the water would only be a little warmer than room temp..but maybe if it was ramped up)

With even 8 TV "windows" at 300watts each is 2.4kw of space heater (8.2KBTU/hr) about 1/4-1/3 of my design-day heat load in a non-superinsulated non-earth-tempered stick-built antique of a house.  For less money than it would take to insulate a 10,000 gallon tank to be able to store the full-season's heating shortfall I could retrofit an additional R20-R30 onto the outside of the building, buy some new windows & shutters and be down to less heat load on the coldest 1% of heating-season hours than those TVs would be putting out 24/365.  The rest of the time I'd be having to pump the heat out. In a modestly insulated sub-terranean home surrounded on all sides by 10C dirt it would need active cooling 100% of the time.

You can do a lot with just a little bit of geothermal heat pump, if freeze control was all you were after, but even a little bit of geo ain't 'xactly cheap.  In order to pump much low-temp heat into the space without ridiculous amounts of radiator/baseboard the water temp needs to be at least 10-15C above room temp. But if your design goal is merely to keep the room above 5C, that can be done very efficiently starting with 4-5C water from a well.  But if your "heating" water is just 5C above your room temp minimum, you're not going to be able to pull it off.

so water doesnt radiate at its real temperature?

I have radiant heating in the house here. Is it 15 degrees above room temp?

Hi Dana,
I understand your concern. I would bet there are alarms going off all over in your head. But consider this ...
If you look at this thing mathematically, what time frame does your math use? Now follow through with ten times the time. For example, if you insert 1000 cubic foot device at 200 degrees into 50 degree ground, within a few hours it will drop substantially. But earth is one of the best insulators there is. That’s why 20 feet below ground the temp remains the same because the above ground extremes cannot penetrate that deep. So, I heat the tank up to 200 degrees. The ground around it absorbs most of the heat and I must reheat the tank. The ground around absorbs it again, only this time the tank only drops 9/10 in the same time as it did the first time. Repeat this cycle 20 times, and eventually the tank and surrounding ground temps will stabilize. At one foot out, the earth temp will be 190, at two feet out 180, at three feet 170, and so on. As a result, your tank temperatures will also stabilize. I call this primary charge. Then, the amount of heat required to bring the tank temp back up is greatly reduced. This is why it takes a great amount of energy to bring a house whose temp has dropped to 40 degrees back up to 70, and why it takes much less energy to hold it at 70 over the same time. The one element not covered in a Delta T formula is time ... Remember all variables have an effect on the outcome, and time is the largest variable.
Now, on to the collector. The Fresnel heat box must be super insulated, as well as the lines to and from the storage unit. Think a 4 inch PVC tube with a 1 inch copper tube centered in it. Then we would use an expanding foam insulation to fill the voids around the copper. This tube would leave the collector on the roof and immediately enter the house, go straight down through the basement, and out underground 20 feet below ground level to the storage tank. Where here do you see the massive system loss? The Fresnel box would be similarly insulated, and the temp internally would be stabilized because it is filled with several runs of 200 degree pipe, surrounded with foam insulation, minus the light contact points. Heat can be contained, and 200 degree heat is not really that high. Six inches of basic foam insulation will shield this Delta T quite well in this box. And remember, my heat collection will primarily be done in 60 to 90 plus degree outside temps, not the 30 degree winter days. Heavy charge in the summer, trickle charge in the fall and spring, and possibly a little bit in Jan and Feb, depending on the sunlight availability.
As far as super insulating a house, it does not matter how thick you build the walls, it will drop down to ambient temp if you do not continually insert heat, or change the ambient temps, as with my sub terrain storage system.
I know you are skeptical. But do not allow that to overshadow mission focus. Skepticism is a sign of need for more thought, not a requirement to pronounce defeat. I try to balance skepticism with contemplation, and that allows for better problem solving. In order to reach beyond you must take the norm and extend beyond by considering all variables. Then remember, a single variable could have a pronounced effect only when presented with another variable. With 20 different variables, the possibilities become exponential. Without that we would have never walked on the Moon, or flown airplanes, or even built a fire. It is the one tool God gave us over all other living creatures. I know, get off your soap box …

Greendreams,
No, water does not radiate at its real temp. Hold your hand real close to a cup of hot coffee, then touch it and you will see what I mean. (Pain is the best educational medium I know!) That is the whole delta T thing. Two different temperatures. The Delta T is not a linear mathematical function. It is an algebraic function. Let me explain. If I have two different temps in the same neighborhood, as in air, water, or even a complete vacuum, the separation of temp levels and the thickness of the surrounding medium will determine how fast the temp will travel between the two points. A delta T of 2 degrees will hardly transfer any heat energy between the two points, while a Delta T of 20 might be ten times faster at that single second. As the heat transfers from lower to upper levels, the Delta reduces exponentially. If you have a delta T of 200, then the rate becomes much faster, maybe 100 times. This is the point Dan makes in his previous post. By changing the surrounding medium from earth to asbestos, the Delta T is changed radically. I suggest you skip the asbestos though, it killed my old man. Lets see, I can’t do a vacuum, but I can make asbestos … Oh well, lets make some money! NOT!

Huh?

The emissivity of liquid water is ~0.95, better than black paints or charcoal- about a good a radiating surface as there is in practical terms.

All your cuppa joe experiment demonstrates is that conductive heat transfer rates are typically much higher than radiant heat transfer.  But the exact temperature of water is readily measurable by the flux & spectrum of it's infra-red emissions- it's a very good "black body" radiator.
 
The R-value stackup differing materials introduce non-linearities to the temperatures found at different depths within the structure, but does not change the steady state R-value in an appreciable way- it's still pretty much an addition problem. Adding the R-values of the layers will get you to the total heat flux answer to well within 2%.  The gross delta-T across all layers remains the same, even if the substitution of other materials within the stackup changes the delta-T across individual layers.

Measuring heat transfer rates at the surface with your hand is useless.  If you can feel it AT ALL you're already 5 orders of magnitude higher than it needs to be to hang onto most of the heat for a week, let alone a season.

so now I have no plan. I was going to use well water but it's probably around 40degrees and it sounds like 50 is minimum. I guess even in year 1 I have to warm it up somehow...I can build a loop of pipe that's burried really deep like 20 feet and the water should warm up a degree or 2 but maybe its time to add a thermal solar panel in year 1 ...

Getting the heat transfer out of the water and into the room air across the boundary of the tubing & floor is the issue.  The large majority of the heat transfer in "radiant" heating is conductive, and the air it's transferring the heat into is by nature insulative.  If you coated all surfaces in the room with the water in liquid form the contact area would be large and the difference in room  air temp to liquid temp would be small.

The actual delta-T between the water temp in a hydronic system and the room air temp is a function of the heat loss rate of the room and the surface area & R-value of the radiators.  In most under-floor radiant systems with wood floors you have ~ R1-1.5 of wood between the tubing and the room, and a limited amount surface area contact between the tubing and the sub-floor. With aluminum heat-transfer plates between the tubing & floor and a moderately insulated room the water temps can be anywhere from 15-50C above room temp, and the floor surface 3-5C above room temp, depending on how much heat it needs to supply to the room.

If the radiation is metal fin-tube baseboard or similar, and the total surface area is the same (which takes a LOT baseboard, mind you) of the water temps can be much lower since the R-value of the metal is negligible.  But in order to get the air between the fins of the fintube into the room it has to be heated high enough that it's density is light relative to the room air to convect away, and this convention drops to very low levels indeed below a 15C delta-T.

Think of it this way:  The room temperature will stabilize at pretty much the average of the temp the surface area of all the interior surfaces.  Put one very hot radiator like a wood stove in the room, it brings the average way up.  To keep the average above 0C using 5C water means you need to have a VERY large surface area of 5C surface, if the interior surface of the windows are -5C, and the exterior walls are 0C.  If you're using fin-tube to increase the surface area, it's no longer 1-1 on surface area, since the fins themselves do not face the rest of the room, but each other, and need convective currents to distribute the heat- it's' not direct radiation.  15C delta is something of a lower bound, and assumes a large amount of fin tube.  Most hydronic baseboard heating systems in the world need water temps 40-60C above room temp to be able to deliver sufficient heat on "design day", but doubling the length of baseboard can bring it down to radiant-floor type temperature requirements.