Author Topic: Active Annualized Heat Storage?  (Read 6200 times)

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evilpsych

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Active Annualized Heat Storage?
« on: May 19, 2007, 05:22:01 PM »
Hi guys, first post, but I've been a longtime fan of the site, especially the wind generators.


I've had a great deal of interest in passive solar home design, PAHS, geothermal, wind and alternative energy sources for awhile. More for the longterm economic and independency positive aspects of it rather than any particular political agenda, global warming, etc.


My wife and I have been looking at property, and I've been brainstorming concepts like the umbrella house, monolithics etc, and have come up with a compromise that would seem to work with pretty much any house style. This is just for heating/cooling of the home.


Two-Part Approach:



  1. Masonry House shell - HTM home, made from dry-stack block, and foam board insulation - similar to the T-Mass stuff being marketed by Dow Corning right now. This would allow pretty much any conceivable contemporary or historic home design to be used. One caveat - hydronic system running through the entire home, including the walls and the ceilings. No special earth-sheltering considerations, only modification necessary to a pre-existing design not already made for this purpose would be the adjustment for wall thickness, the hydronic system, and an appropriately angled roof aligned for proper solar focus.
  2. A large excavation of roughly 90k cubic feet either beneath the home, or close nearby on the property. This excavation would be insulated, waterproofed and then backfilled with dry earth, and a separate high density hydronic system included. This secondary hydronic system would be super-heated by roof-mounted solar collectors, perhaps to 90-100 degrees f. This 'reservoir' of heat would be drawn upon by the home for all its heating purposes, once the TM of the home had equalized.


A secondary reservoir could be added for cooling, instead of solar collectors, in the wintertime typical automotive radiators could be used to supercool the reservoir, creating a reservoir drawn upon in the summertime


An active system, which would have few moving parts, (anywhere from 3-10 small low-flow pumps could be used)

« Last Edit: May 19, 2007, 05:22:01 PM by (unknown) »

Nando

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Re: Active Annualized Heat Storage?
« Reply #1 on: May 19, 2007, 12:24:38 PM »
Interesting the concept.


In Plano, Texas, about 20 or so years a professor got a grant to build a house with minimum electric power to have two reservoirs in the "basement" one for hot water and the other for cold water.


The exterior walls with a very high R rating, if I am right around 50 ?, and the roof with large solar collectors to heat or to cool water depending on the season.


Windows with triple panels and south side with winter heating collectors, also next to the house was a small creek, around 2 liter/sec during summer season what was as well used, I did not know exactly what for, maybe cooling, though I saw that the water was returned to the creek.


For two years, I got information that the project was a great design reducing the needs of energy for a family of 5, after that the information stopped and did not know what was the end of it.


Nando.

« Last Edit: May 19, 2007, 12:24:38 PM by Nando »

wdyasq

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Re: Active Annualized Heat Storage?
« Reply #2 on: May 19, 2007, 03:28:09 PM »
Just off the top....


I don't think I would excavate. 'Earth' is rated at R2 and 'limestone' about 1.3 a foot. Although it would take 6 foot of earth or 10 foot of to finally get "R13", it does add and eventually the mass of earth or limestone will eventually insulate itself.


One would need to bore holes and chill or heat the mass of earth/limestone. But - it will be far less expensive than excavation and back-fill. One would also need to calculate how much heat they could store, what "Delta T"(the temperature difference between mediums) would be of the final mass in relation to the desired room temperature and the ambient. I would think a minimum of 30F 'Delta T' may be necessary for any decent exchange to work with a water/air exchange.


In the North Dallas Texas area "Geo-thermal" was tried several years ago. The idea was one would heat the earth in the summer with the heat pump then use that heat in the winter. The "cooling season" is/was 7 months and the "heating season" was 5 months. There may be ordinances against opening doors and windows as it is seldom done. Folks bragged about the savings the first couple of years. More were built. Then, the longer heating season started raising the local ground temperature and the cooling costs went up higher than those with air cooled heat pumps. This fact has been kept a lot more quiet than the initial 'savings'.


'Geo Thermal' is again being used. They are using a lot more area to disperse the energy. The sellers of the newer systems aren't bragging about the savings ... yet.


Let us know how your project progresses.


Ron

« Last Edit: May 19, 2007, 03:28:09 PM by wdyasq »
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PeterAVT

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Re: Active Annualized Heat Storage?
« Reply #3 on: May 19, 2007, 04:44:30 PM »
This is not much different from the public road stops on Interstate-80 in Colorado if I recall correctly. I had travelled through there about 20 years ago, and the stops were a project for the local universities, to see what is more energy efficient. I took some interest in this because my home state (NY) and town is roughly upon the same lattitude; however the energy costs here are exhorbitant thanks to politics.

As I recall, the best designs used "hot rocks" or thermal mass; The structure itself was quite thick with rocks, the insulation could be directed inwards at night, and sat upon a very large bed of even more rocks which were automatically exposed or shuttered to the sun. What little electricity was needed was provided by PV panels upon the roof, and a battery bank. I suppose the same could be done with many small wind gennys up north here.

« Last Edit: May 19, 2007, 04:44:30 PM by PeterAVT »

whatsnext

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Re: Active Annualized Heat Storage?
« Reply #4 on: May 19, 2007, 07:15:05 PM »
I can't imagine that insulating your storage would ever be as effective as just insulating your house so you wouldn't need much heating or cooling. You have to go in and out once in a while so air infiltration will definately overcome any amount of insulation. Plus, if you live in a hot climate you don't need to save heat and the opposite is true in cold climates. I would calculate the exact costs of creating these large storage areas and compare that to just building a low E home.
« Last Edit: May 19, 2007, 07:15:05 PM by whatsnext »

rossw

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Re: Active Annualized Heat Storage?
« Reply #5 on: May 20, 2007, 01:02:35 AM »
Plus, if you live in a hot climate you don't need to save heat and the opposite is true in cold climates.


I live in an area that I would consider pretty warm. Summer temperatures here get to (and over) 46 degrees C (115 deg F).... but I still need heating in winter. Sure, we don't get it as cold as many, but -7C (about 20 deg F) is about 27 deg C too cold!


Additional thickness of earth, quite seperate from its insulation properties, has a quite seperate and beneficial effect - thermal mass. We built our home with all cinderblock internal walls, concrete slab for floor and roof, have lots of thermal mass inside and the temperature fluctuations are amazing. Where our old home - insulated walls and ceilings, double-glazed windows etc, would vary easily 30 degrees C on a typical summers day, our new place varies about 1 to 2 degrees.


Whereas airconditioning is virtually essential in homes in our city, we have none at all, and were comfortable this summer!

« Last Edit: May 20, 2007, 01:02:35 AM by rossw »

whatsnext

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Re: Active Annualized Heat Storage?
« Reply #6 on: May 20, 2007, 11:27:51 AM »
I understand this but it has nothing to do with what I was commenting on. The original poster is considering the creation of large heat and cold wells that, I can only assume, he plans on using in oposite seasons.

John...
« Last Edit: May 20, 2007, 11:27:51 AM by whatsnext »

GaryGary

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Re: Active Annualized Heat Storage?
« Reply #7 on: May 20, 2007, 11:42:01 AM »
Hi,


This is a tempting concept.

A while back I tried to estimate how well such a system would work for my house.

Even with me driving the backhoe, I could not get the numbers to work out.  The heating season energy for my house is pretty large, and the cost of an insulated hot water storage excavation plus was high.  Controlling heat loss from the excavation requires a lot of care and good insulation.  You need a way to keep the insulation dry -- this has been a big problem on some existing commercial installations.  

But, I do live in cold climate (MT), and there is only so much I can do to get the heat loss down on my existing house, so the scheme might work better for you with a new house from the ground up.


There is some good information on building the underground heat storage "tanks" -- if you search on "seasonal heat storage" or the like you should find them.  There have been a number of them built in Europe, and there are papers that analyze performance (often not up to expectations) on ones that have been in service a while.  These are typically larger than needed for one home, but (I think) the issues are the same.


The Drake Landing community uses underground seasonal storage -- their storage scheme is different, but interesting -- search for "Drake" on this page: http://www.builditsolar.com/Experimental/experimental.htm


I think that it is a concept that definitely needs some careful design and analysis.  You could start with a heat loss on your projected house:

http://www.builditsolar.com/References/Calculators/HeatLoss/HeatLoss.htm

This will give you and idea of the full winter heat demand.


You can get a very rough idea of the "tank" size by taking the winter heat demand from above and dividing it by the temperature range you can use for the tank -- maybe 150F down to 90F, or a 60F range.  So, if you need 30 million BTU for the winter and can run your tank from 150F down to 90F, you need (30000000/60F) = 500000 lbs of water or 60K gallons.  This ignores the heat you will collect in the winter, which would reduce the storage, but also ignores tank losses which would increase the tank size.


To get a very rough idea of the collector size you might need to charge the tank, you might assume that you can store about 1000 BTU/sqft of collector per day.  So, if the collection season is 150 days(?), you might get 150000 BTU per sqft of collector per season.  To store up the 30 million BTU, you might need about 200 sqft of collector -- not so bad.


Some people have looked at this and concluded that it makes more sense to work on getting the house envelope well insulated and tight, incorporate passive solar, and perhaps some active solar but with storage for only a couple cloudy days.  


Gary

« Last Edit: May 20, 2007, 11:42:01 AM by GaryGary »

hydrosun

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Re: Active Annualized Heat Storage?
« Reply #8 on: May 20, 2007, 12:34:57 PM »
I read an article in the old Mother Earth News in 1984 about a house in Montana that used passive annual heat storage. So in 1985 I built one here in cloudy western Washington.  I was 26 and really didn't know what I was doing then.  I used 5 inches of styrofoam and three layers of plastic sheet over the top. The insulation tapers to two inches out to 10 feet from  the front of the house and 15 feet out the back. the house is a quonset hut shape make from ferro cement.  I've lived in it since. In the summer the temperature inside never gets over 78F. Around about the end of October the temperature starts to cool off to 65F and we start burning a small hot fire in the woodstove in the evening. We go through a cord and half through the winter to keep the house close to 70F.  I'm using less wood now that we use extra power from the hydro to run a heat pump.  Sometimes we start the wood stove just so we have hot water for showers.

 So I know that a earth sheltered design works. But a well insulated house with  a separate heat storage may work just as well. Water would hold more heat in a smaller space than dry dirt and the heat can be moved and controlled more precisely.  I remember one article describing a house in cloudy Oregon that used a lot of cheap homemade solar water heaters used to heat water in a huge storage tank that heated the house through the whole winter without backup heat. So the storage was short term rather than annual. The trick was lot's of insulation and oversized collector area to utilize the few days of sun that do occur in the winter.

Chris
« Last Edit: May 20, 2007, 12:34:57 PM by hydrosun »

chadking

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Re: Active Annualized Heat Storage?
« Reply #9 on: May 21, 2007, 01:32:21 AM »
Very interesting. Do you have any other information available regarding your house?  I've been interested in this type of heat storage, but there is not much info available regarding it.


Here's one article regarding annualized Geo-solar design...

http://www.ecolivingcenter.com/articles/geosolardesign.html

« Last Edit: May 21, 2007, 01:32:21 AM by chadking »

ddrew

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Re: Active Annualized Heat Storage?
« Reply #10 on: May 24, 2007, 01:22:41 PM »
Hey Ron,


I'm building west of DFW, in the Springtown area (far south Wise County), and am digging into the South side of slope to build a HTM home, using 12" Papercrete walls and geothermal for Radiant Heating/cooling in Adobe floors.  I've considered using PAHS, but the cost of digging is getting out of control due to fuel costs.  The data I've seen indicates there is a comfortable 65 - 70 degree mass under this area, and hope to use geothermal wells along with an insulated underground storage tank to hold water for recirculation. I agree that our average temperatures are getting higher, but I'm thinking that the radiant heat concepts will also work for radiant cooling. Have you seen any newer data that gives a better picture of the temperature ranges around here, since we've gotten warmer??  


I may have to rethink the geothermal aspects if there is solid data indicating ground temperatures are growing.


Best regards,


Dale

Springtown

« Last Edit: May 24, 2007, 01:22:41 PM by ddrew »

evilpsych

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Re: Active Annualized Heat Storage?
« Reply #11 on: November 20, 2007, 05:58:34 PM »
Well.. I've researched the concept more, and feel that it can be simplified somewhat from my earlier ambitious concept. I only came up with the original concept after reading a lot about PAHS, and thinking that it could be made to work better.. However, here is the refinement of the design concept, it still involves 2 storage tanks, however much more reasonable. 2 500 gallon water storage tanks, insulated similar to the 'super-solar' tanks on one website. The first 500 gallon tank is purely solar-heated water/fluid, with 2 massive copper coil heat exchangers submerged in it, one for domestic hot water and the second is the storage/mixing tank for the home system. The second tank has the aformentioned AAHS 'ground loop' pumping into it. The PAHS style with the buried plastic sheeting and insulation boards to retain heat would be used. Hydronics in the house would only need to be in the floor and walls, not the ceiling. PEX would be used to create zones.


The ground loop would be maintained around 68-70 degrees by thermostatically controlled pumps dumping heat into it in the summer and winter. The house hydronics would draw from both tanks, primarily the ground loop tank for maintenance, and the solar tank for emergency heating, with a gas backup.

« Last Edit: November 20, 2007, 05:58:34 PM by evilpsych »

evilpsych

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Re: Active Annualized Heat Storage?
« Reply #12 on: December 02, 2007, 02:55:45 PM »
also, to explain more about why I'm not approaching this directly from a house design and envelope insulation frame of reference.. The area I'm considering building in already has several historic buildings (late 1700's, early 1800's) and to keep the architectural feel appropriate, we would be building in this same style - this pushes us to look at more non-traditional forms of heating and cooling. Somewhat of a waste from an energy standpoint - and compared to a lot of the homes described on this forum, but still long-term less expensive


also, regarding the storage of 'coolth' what i described in the initial post is not simply piping the cold into the ground like boreholing or PAHS.. image digging a hole, and constructing a plastic lined  styrofoam cooler in which wet earth (for the cold storage) or gravel and water mix are dumpedon top of a grid system of coolant tubing layered until the top. One thing I'm considering for use for this concept are used shipping containers

« Last Edit: December 02, 2007, 02:55:45 PM by evilpsych »