Solar heatsink

System

Hello Folks,
I have been trying for days to find info on storing solar collected heat in a heatsink.
I hope I am posting in the right area of your forum.
Since I have yet to find anyone who has done anything like I am hopeing to be able to do I will continue.
I will thank any and all in advance for your comments.

What I have --- is a cement well casing (ID) 33 in x 33 in by 80 inches deep.
The well itself is 130 feet into the ground but is inert.

My idea is --- to seal the well drift closed, insulate the outside of the cement housing/caseing, set up solar panels and run loops within the chamber.
The square footage (filled) plus the cement will retain heat.

Then run a separate band of loops to my house to tie into my existing hot water heating system.

My questions are --
1) -- How many feet of looping is required ? Or do I just do a maximum with --say two inch spaces ?
2) -- What do I use to fill the void around the pipes with to get the best heat transfer?
--- water?
--- used cooking oil?
--- sand?
3) -- Can used auto transmission oil be used in the solar panels instead of water and glycol.
4) -- What is the best way to seal the inside of the cement chamber to prevent heat loss through ground water passing (weeping) through?

Hope someone can help, and again, thx for now.

Bill

Cariboocoot

Re: Solar heatsink

You might want to check out Build It Solar: http://www.builditsolar.com/

Somewhere in all those neat projects I remember seeing a system like this, only using an underground polypropylene tank.

To store any significant amount of heat over any long period of time you need a very large solar mass, such as hundreds of gallons of water.

A few other remarks based on my experiences in many fields :

Sealing concrete that as already in the ground is nearly impossible. To prevent water seepage from outside it needs to be sealed on the outside just the way they do a new foundation. Unless you can dig down all around it (expensive) and seal it up tight it will probably leak at least some. Interior sealing is always less than perfect because the hydraulic pressure coming through the concrete works to push the sealant away instead of towards it. If you want to try some of the standard concrete sealers available at hardware/building supply don't be surprised if they're disappointing (i.e. don't invest too much).

Don't use ATF: it's toxic and if it leaks you've got a nasty mess.

Most of the systems of this type use a "full reservoir" with water/glycol solution circulated through the collector and into the tank. Thermostatically controlled so that it doesn't circulate when the collector isn't hot. A second coil within the reservoir is used to pick up the heat and transfer it elsewhere, as in for home heating or hot water.

There are a huge number of variables in a project like this. Your location being a very big one. It may not be a very practical thing to undertake. But it might be fun and informative!

System2

Re: Solar heatsink

Thx for your reply.
Will check out that site.
I have access to a track hoe so getting down all around the six feet will work.
I suspect blue styrofoam would be best.
Which leaves me with the inner problem.
They do have rubber dam material for rock gardens but I do not know if I can get it made into a liner to fit the interior.

No on the ATF ( I would agree with you on the toxic part--and very unfriendly enviromentally.) I think the same on antifreeze, but there are few choices.

I wonder if anyone has ever tried re-filtered used or new cooking oil.

Thx again for your input.

mike95490

Re: Solar heatsink

I'd think, for underground based storage/transfer, that using anything other than potable water, would be very risky. Say your well is dry , but it may connect to a lower aquifer, and you would not want to be the person found pumping XYZ into the earth, that shows usp 15 miles away in a city well.

TnAndy

Re: Solar heatsink

I can't quite picture what a "well casing" is that you describe as 33x33x80"......a well casing here is a 6" steel pipe driven down a couple feet into bed rock to keep surface water from entering a well drilled on below......but whatever.....say you have this concete "box" of the above dimensions....and say, some how you CAN dig the whole thing up ( because you'll need to insulate UNDER it as well...pardon the pun ), you still only have a box that will hold about 350-400 gallons.....

A BTU is a the amount of heat required to raise one pound of water one degree F.

400 gallons is about 25,000lbs.

Say you get the water up to 150 degrees without to much loss, and use that water down to 100 degrees for heat ( much below that, and a direct exchange of heat falls way off in the efficiency of transfer, I'd guess )....so you get to "use" 50 degrees x 25,000lbs or 1.25 million BTUs.

I have no idea what your heat loss is for the building you're heating, ( or where you're located......either/both would be handy info ), but say you need 100,000BTU/hr furnace to supply you now.....you can see your water tank might be good for something like 12 hrs, assuming 100% efficiency and no losses.....which AIN'T gonna happen, so more likely you'd get something like 8-9 hours ( again, making an assumption about building loss ).

I personally have used an old 500 gallon propane tank ( with 2" of insulation around it.....and it STILL keeps the basement toasty warm ) in my basement for the last 25 years running a heating loop thru my fireplace.....I get the water temp up to 190-200 degrees on a regular basis when we fire up for winter, and that still only let's us coast a day or so. If I had it to do over, I'd put at LEAST a 1,000 gallon concrete septic tank under the basement floor and use that.....which is what I'd tell you to do as well.....forget trying to insulate something already in the ground, and use the trackhoe to dig a hole for a new tank.

GreenPowerManiac

Re: Solar heatsink

Sounds so much like Solar Water heating. Why not consider this ?

I've seen something on instructables.com where a solar water heater collector was made for about 5 bucks with some household items.

http://www.instructables.com/id/Solar-Thermal-Water-Heater-For-Less-Than-Five-Doll/

System2

Re: Solar heatsink

Thx for the info.

I called it a well casing as I had no other name for it.
I have never seen a set up like this before myself. (it was here when I bought the property).
It is a cement rectangle box over a 4" pipe that is about 100 feet into the ground with a cast iron lid.
The dimensions I gave were the interior measurments.
I just thought as the well is useless that I may be able to use the space to store solar heat.
I am aware as is stated that it may not give me much gain.
There seems to be little info out there on such with the exception of using rocks and forced air through a hot air solar panel set-up.
Maybe that is the way to go on this one if only for an experiment.

All info provided helps of course and is appreciated.

Cariboocoot

Re: Solar heatsink

Woodworm wrote: »

Thx for the info.

I called it a well casing as I had no other name for it.
I have never seen a set up like this before myself. (it was here when I bought the property).
It is a cement rectangle box over a 4" pipe that is about 100 feet into the ground with a cast iron lid.
The dimensions I gave were the interior measurements.
I just thought as the well is useless that I may be able to use the space to store solar heat.
I am aware as is stated that it may not give me much gain.
There seems to be little info out there on such with the exception of using rocks and forced air through a hot air solar panel set-up.
Maybe that is the way to go on this one if only for an experiment.

All info provided helps of course and is appreciated.

That is a well casing, or more accurately a "well pit" (redundant!) There's lots of different types. Many are rounds concrete - as in shallow wells. The kind you describe is usually used to accommodate a shallow-well pump which pulls water from down the 4" pipe. The concrete "box at the top" gives room for the pump and to be able to work on it. With a 100' hole in the ground it qualifies as a deep well, so why they didn't just put in a submersible pump and saddle connector I don't know.

The basic problem you face is being able to raise enough mass a sufficient amount of temperature to make the heat recoverable in a practical amount. Insulation is essential. If the whole storage tank were below freeze level it'd be easier, but even "warm" ground temperature is lower than you'll want to get for heating purposes.

Maybe you should think about using this abandoned well as a source for a "ground source" heat pump?