Use an old Water cisteren for heat storage?

[Bobwied]

Greetings,

 I have just found this site and what a lot of good ideas.  Many of the articles and post have gotten me thinking.  Would it be possible to use an unused 3000 gallon cisteren in my basement as some sort of heat storage by using a home made solar heater in the summer and reclaim it in the winter?  How would you figure how much heat you could store and reclaim? I have many questions but I think I will start with these two.  Maybe just a pipe dream.  Thanks for your time  Bob

[adelaide]

at gess would neeed a type of vacum /reflective insulation to stor that long but u  may be able to help. if u had fire heatting it up at night then soler if sun and use when u need car radiator etc. maby heat the ground under house may help to just big cloecter aria .i used water bed bladder was brown to heat small 4 ton water in pool to hot as bath ,will paint it black this year,poly pipe/pond pump /thermal swich in circle is cheep to ,bladder needs to have no head presher or popp. i think pespe insulates alot better in colecter but limeted life and may buckle in hot summer if no flow,maby u could pump hot ait threw rocks /gravel as well ,but insulation is the hard part for 6 months long time prob to long

[techwolf]

I'll take a stab at it, even thought about doing the same thing.

First you need to insulate to keep the heat in the tank, else it would

just heat your house all summer long..

Anyway, you get 1 btu / lb / degree F

so 3000 gals is about 30,000 lbs of water.

lets say you could get it 100 degrees F above room temp, and thats hot 170...

so 100 x 30,000 is 3,000,000 btu, this is not really a lot of heat.

A cord of firewood might have 20,000,000 btu,

could be done but I think you need more storage to last all winter.

Depending on how cold/long your winter is.

[crashk6]

Yes is is possible... the most practical thought on this mater is to use a heat pump... this would also have the advantage of cooling the home in the summer.

The type needed would be a what is called a ground source heat pump, specifically the ones that process ground water... you would be using it in a slightly un-orthodox manor as you would not be using it with ground water but rather your cistern.

The next thing you would need is a set of solar thermal panels and a proper heat exchanger. Effectively a closed loop glycol system... wont freeze in winter!

You will also need a thermostatically adjustable differential controll for the solar side of things.

The operation of said system would work fairly simply going into fall and thru winter the thermal panels raise the temp of the water in the cistern to give the heat pump the thermal energy it needs... as long as the solar input can keep the water 50o F or above the heat pump will be quite happy with that extraction temp range.

In the summer the the solar thermal panels would be used in reverse... like this.. thru the day the heat pump would be pushing heat into the cistern, at night the solar thermal panels would pull the heat from the cistern exposing it to the night sky... effectively dumping the heat and dropping the cistern temp back down to around 50-40o F this process is especially efficient on non-cloudy nights! The differential control is what minds the solar collectors and makes sure they do there job automatically... the heat pump would function as any heatpump does.

Effectively this system is two different types of heat pumps coupled together via a storage medium.

One tip however... every 3 - 6 months you may want to dump some hydrogen peroxide into the cistern to keep the water from turning... stagnant water can really stink a place up... the heat pump would be circulating a great deal of the water... e.g. moving water... but in a closed system it can still turn. But use a week solution, too much/strong and it will oxidize your mechanical systems and shorten their working life.

Do NOT use chlorine in conjunction with a ground source heat pump!

--

crashK6

[pyrocasto]

Should work fine. Dont really need it for the whole winter, but just overnight when the sun is not out. 1 cord of would could heat a small house for quite some time.

[Volvo farmer]

I think the premise is impractical. I do not think you can realisticly store up heat in the summer and release it in the winter with water storage. The laws of thermodynamics are working against you. Your're going to have a bunch of thermal losses out of that tank. If you don't put any heat in for a week or so, I bet all the water ends up being the same temperature as the air in your basement. Even if you do have some solar collectors, they are not going to be able to raise the temperature of that much water more than a few degrees during a winter day and the next morning, you're going to be right back where you started.

Solar water heat systems that have been designed and are proven to work use a tank sized at a degree of magnitude smaller than the one you are talking about. They operate on a daily cycle, rather than a yearly one. It's much easier to keep 120 gallons of water at a useful temperature (~100F) overnight and heat it up again the next day than it is to do what you are proposing.

You might be successful filling up that cistern with head-sized river rocks and blowing solar heated air through it during the day and reclaiming that heat at night.

[Kwazai]

http://www.ece.villanova.edu/~nick/solar/solar.html

if the cistern is empty the solar closet idea would probably work well. Most of what I have seen says to insulate somewhere around r-40. If the cistern is big enough you could probably run the cooling the same way(ground loop water and fans). Nick Pine has a lot of calcs and a short computer program buried in usenet postings (you would need to search-solar closet).

I had seen some solar homes designed with milk jugs or 2-litre bottles as water /heat storage in the basement. Basically they took greenhouse air and fed it thru the 'closet' (and house-during the day) to warm the water jugs and tapped it at night for house heat (less expensive than other storage mediums- though rock, sand, etc. are also good)

anyway its a place to start(calcs...).

L8r

Mike

[Kwazai]

http://www.westol.com/jbrown/jimsspot.htm

a little simpler overview.

[pyrocasto]

I read wrong. Making heat in summer to use in the winter, no it would not work.

[MountainMan]

"Do NOT use chlorine in conjunction with a ground source heat pump!"

More info please.  What does chlorine do to harm a heat pump?

thanks,

jp

[crashk6]

Chlorine damages a heat pump over time by corroding the metals (generally copper) in it's heat exchange coils. Trace amount of chlorine will not shorten the life span of the equipment, but with large amounts of water folks tend to chlorinate to the levels you see in swimming pools... which will damage them. I also must admit I have a personal dislike of chlorine as it's an endocrine blocking chemical that is damaging to the central nervous system... and in large tanks of water when the chlorine escapes it does so as deadly chlorine gas. On the other hand peroxide can control bacterial growth even with just trace amount and trace amount of peroxide are not damaging to the human body. But peroxide is a damaging oxidizer in larger concentration both to the body and mechanical systems, but as spairing use is all that's required all is well..  and no smelly water!

--

crashK6

[hvirtane]

The problem is that it is really

difficult to make such an insulation

that the heat would stay a long

time in any kind of storage.

For example in Sweden they

have done some research

concerning storing heat energy during

the summer for the winter.

One system was made

to use a kind of big thermoflask.

It seems to be that it could

be made working somehow,

but it is very costly.

The other research

was directed into the use

of discarded mining tunnels

or other big 'caves' underground

as the storage, utilizing

instead of best possible insulations

really big heat mass storage capacities.

The latter idea might work even as

a self made system, but I don't know

about any examples.

An extract from a text:

-------------------------------------------

A different approach to

shallow geothermal energy

- Underground Thermal Energy Storage (UTES)

Burkhard Sanner

Institute of Applied Geosciences, Justus-Liebig-University

Diezstrasse 15, D-35390 Giessen, Germany

A general conclusion can be made:

HT-UTES is required to allow

direct use of stored heat,

without further energy input,

e.g. for heat pumps.

If high temperature heat

is available from

clean sources (solar collectors,

geothermal) or as waste,

the overall result of HT-UTES-opera-

tion is always favorable.

The remaining problems all

seem to be not too hard to be solved...

------------------------------------------

Please see also:

http://www.geothermie.de/egec-geothernet/energy_storage.htm

- Hannu

[Kwazai]

that constant cool air in a cave...

 I went to mammoth cave one summer and the entrance had a sizeable rush of air coming out of it- seems it was a big geothermal solar chimney. I believe you are right in terms of long term storage of the heat-prohibitively expensive.

The cistern for house size heat requirements would probably be overkill and cause more summer 'heating' problems if the entire 3000gal were to be heated (not to mention the cost of the panels and pumps). also would have a lot of water quality/health issues as an 'open' water tank. The solar closet overview link above has a fairly sophisticated control system on it and my thinking (being a 'lo-buck' type) a simpler control system could be accomplished with a thermostat and some duct fans by tieing it in to the heat side of the house thermostat.

Mike

[kell]

A few weeks ago I followed a link from some post here to a web site about a heating system somewhat like you describe.  The system does not store heat for months, of course -- that's just not feasible.  It uses a heat collector on the roof with USED motor oil (black, absorbs sun) under glass, running down corrugated steel and flowing down to old radiators (house, not car) installed in the cistern to transfer the heat into the mass of water contained there.  A sunny day and you get a lot of heat stored in the cistern.  Thousands of gallons of hot water -- nothing to sneeze at.  Everything, especially the collector on the roof, has to be sealed perfectly or you have a very nasty problem with the smell.  Interestingly, the variation of the oil's viscosity creates a kind of feedback -- when the systsem's cold, the sluggish oil stays longer in the collector, gathering heat, but if the system has already lots of heat, the oil will flow quickly past; it can never really overheat.

[RickieBlue]

There are several issues concerning water storage in a cistern. Due to the surface area exposed at the top, there will be loss of water (evaporation) and loss of chemicals used to treat the water. One idea I read about years ago, was to cover the surface with ping pong balls, as they effectively reduce the exposed surface area. Moisture problems directly above the cistern would be a major concern. I personally think water storage is a decent way to go, as it is easy to pipe and control different zones. Solar could also be backed up with a wood boiler, as we all know firing a boiler hard for 4 hours daily is twice as efficient as having a smoldering fire for 24 hours. My 2 cents worth!!!

[benjamindees]

It takes one btu to raise one pound of water one degree Fahrenheit.  One gallon of water weighs about 8.2 pounds.

3000 gallons of water raised from 70 to 200 degrees Fahrenheit represents (3000 * 8.2 * 130 =) 3,198,000 btu.

That heat is equivalent to running a 10,000 btu/hr wall heater continuously for 14 days, or a 60,000 btu furnace at half duty for 4.5 days.

And that's assuming you can keep it hot until the time you want to use it.

[GaryGary]

Hi,

Its hard to store heat in the summer for use in the winter for the reasons that others have mentioned -- it takes a lot of thermal mass to store enough heat to last for months of winter, and you have to insulate it well.  The only system that I have seen that seems to work for an individual home was developed by John Hait from Montana.  His scheme uses a large quantity of dry dirt around the (buried) home.  The dirt is insulated on top by a large "umbrella" of insulation that goes out many feet from the home.  This umbrella also keeps the dirt dry, since water moving through dirt can rapidily remove heat.  The dirt storage is heated by solar gain from south facing windows of the house.  The house walls between the house and the dirt storage area are not insulated, so heat can transfer in and out of it to the house.  Its a really interesting system, and John has built and instrumented several homes -- he makes a very good case for the system actually working well in 8000 deg-day Monatana.

More on it here:

http://www.builditsolar.com/Projects/SolarHomes/constructionps.htm

Scroll down the page and look for this entry:

Passive Annual Heat Storage

John Hait

There are some links here to articles and books he has written on the system.

There have also been some large commercial seasonal heat storage projects that have been used to supplement heating for multiple residences.  These systems do appear to work, but they are very large projects.

Gary

 

[Solardreamer]

There is a new Net Zero home in Boulder, CO called the Harvest house that uses solar DHW as its only heat source ( besides passive solar gain).  It uses 12 reclaimed Novan collectors to heat a custom 6,000 gal H2O storage tank.  It can heat the home for 8 days at -20f with no solar gain by the stored heat.  

http://www.ecofuturesbuilding.com/files/active/0/1887%20Brochure%20WEB%20VERSION%2012.15.pdf

I guess if you could have a 5,000 gal double walled evacuated stainless steel cistern you might be able to store the heat for quite a while, still doubt it if you could make it 6 months though.  Need to keep it charged....

[solidwoods]

No can do.

Waste of time.

Dont mean to be mean.

Build a wood fired hotwater heater, way more bang for your buck.

Mine runs on free wood chips

jim

Heat pumps can be plumbed with SS, tube for the heat ex. tubes that are in the water.

As the water heats up it runs the heat pump more hot and less efficient.