Subject: Re: Off-Peak A/C with Ice Storage?

From: [email-masked] (Ron Bean)
Date: Sun, 8 Oct 1995 00:22:13 GMT

[email-masked] (George Goble) writes:

>A company called Cryogel
>makes something called an "iceball", a baseball sized ball of
>sturdy plastic filled with water and a small air pocket.  You
>fill a tank with iceballs for thermal storage.

   Do you fill these on-site, or are they sealed at the factory?
If the latter, that would imply some non-trivial shipping costs.
If they are pre-filled, are you sure it's water inside?

   Also, is the ball shape for strength, or so you can dump them
in a pile and still circulate air through them (as opposed to
putting them in racks or on shelves or whatever)? Or am I missing
something here?

   BTW, speaking of things that leak...
I have a couple of those blue plastic ice things that you freeze
and use to cool ice chests, that leaked after a couple of years
(actually, the seal came un-sealed). On the other hand, my
parents have a couple that are in metal cans that must be at
least 20 years old and don't leak. So maybe metal is better than
plastic after all?

==================
[email-masked] (Ron Bean)
uwvax!astroatc!nicmad!madnix!zaphod

---

From: [email-masked] (Nick Pine)
Date: 8 Oct 1995 06:40:32 -0400

>>A company called Cryogel makes something called an "iceball"... 

>... is the ball shape for strength, or so you can dump them
>in a pile and still circulate air through them...

They usually sit in an anti-freeze solution...

On another subject:

Article: 40706 of sci.energy
From: [email-masked] (Nick Pine)
Newsgroups: sci.physics,sci.energy,sci.engr.mech,alt.energy.renewable,
            alt.architecture.alternative,alt.solar.thermal
Subject: Re: Solar Energy
Date: 8 Oct 1995 06:06:21 -0400
Organization: Villanova University

Gary Coffman <[email-masked]> wrote:

>Putting that in perspective, you're talking about 594,000 BTU, about
>the amount of heat my furnace puts out in two hours. What do you suggest
>for the other 2158 hours I need heat each season?

I've tried to explain this at least twice before, but for some reason,
few people around here seem to listen, perhaps because everyone is shouting.
Sci.energy people seem to be very energetic, hopping up and down all the time.

Perhaps we can all pause and relax for a moment, and become perfectly calm.
Let us put aside our own thoughts for a moment, and allow the waters of our
minds to become less rippled, to become perfectly smooth reflecting pools,
perfect mirrors, perfectly still waters in which we can clearly and calmly
see the reflected reality of the world around us, just listening...

1. A 16' solar closet containing a 15' cube of 130 F hot water, say,
and 6" of insulation, stores a useful heat for space heating purposes
of about 15 ft^3 x 62 lb/ft^3 x (130F-80F) = 10 million Btu, not a
half-million, as stated above, and 

2. In the house heating system I have in mind, this heat battery would
only be used to heat the house when the sun is not shining. On an average
winter day, the solar closet just keeps itself warm. It does not supply
any heat to the house, except by leakage. On an average day in the winter,
with some sun, the house is heated by an inexpensive, low-thermal-mass
sunspace, that collects about 800 Btu/ft^2 of glazing/day, where I live.

If you tell me how much oil you use over a season, I can tell you how
big a sunspace you need. If you use, say, 1000 gallons of oil a year,
and the heating season is 200 days, you need 5 gallons of oil a day,
on the average, ie you need a sunspace glazing area of about 

5 gallons x 100,000 Btu/gallon/800 Btu/ft^2/day = 625 ft^2

of south-facing sunspace area, which is a pretty big sunspace, eg
about 40' long x 16' high. But then, that's a pretty big heat load...

You can buy the components for such a sunspace from a commercial greenhouse
supplier for less than $1,000... The components for a 3,000 ft^2 commercial
greenhouse (30' wide x 100' long) cost about $3,000, and three people can
put one up in one day, starting from scratch, with no foundation. These
components would make 4 2-story lean-to sunspaces for conventional houses,
each 50 feet long, ie 4 sunspaces 8' wide x 50' long x 16' high, each having
800 ft^2 of glazed area. About a dollar per square foot of glazing. 

>>May I make one suggestion???
>>
>>INSULATE that building NOW!!!!!!!!

Good suggestion. Plug up some of the air leaks, etc. 

Solar closets and sunspaces get to be very large on a house with average
or worse levels of insulation and air infiltration...
Here's a more reasonable application:

I have J. D. Ned Nisson and Gautam Dutt's 1985 John Wiley & Sons, Inc.,
_Superinsulated Home Book_ in front of me, and on page 57-58 they
calculate the total house heat loss coefficient for a 40' x 50'
rectangular house with 8' ceilings and no basement. The walls of
their house are R30, the ceiling is R60. The total window area is 12%
of the floor area and the windows have an R-value of 2.8. Two R10 doors
have an area of 42 ft^2. Infiltration is 0.05 ACH (extremely tight),
and a ventilation system with an air-air heat exchanger supplies an
additional 0.45 ACH with 70% heat recovery. This all comes out to
230 Btu/F or 67 watts/F. They suggest that 2,500 Btu/hour (about 700
watts) is a good estimate for intrinsic heat, ie internal heat generation.

If it is 70F inside and 30F outside, Nisson/Dutt's house would use
(230 Btu/F x (70-30) - 2500 Btu/hr) x 24 = 160 K Btu/day, with no sun. 

On pages 59-60, Nisson and Dutt calculate that their example house will gain
another 100K Btu/day of solar heat through the windows on an average day
in January in New York City. This reduces the average net heat load of the
house to 60K Btu/average winter day, with some sun. Gary's furnace would
have to run 13 minutes a day to heat this house on an average January day.

Bear in mind that this is a _superinsulated_ house, by 1985 standards.
Some people (eg William Shurcliff) say that once you have a superinsulated
house, you might as well forget about spending any more money on solar
heating, because the yearly fuel bill is so low. But it's nice to use
zero fossil fuel, and superinsulation does not heat water.

>You're not paying attention.

There's a lot of that going around :-)

>My furnace is rated at 275,000 BTU/hr.
>Of course it doesn't run all the time.

How often does it run? How much oil a year do you actually use?

>All I'm noting is that the seemingly monster 594,000 BTU of storage 

If this is the 16' monster cube, it holds 10,530,000 Btu, not 594,000.

>is really chicken feed, replaceable by 2 hours running time on my furnace.

Or 38 hours of your furnace running full blast, with the 16' monster.
Over a hundred gallons of oil. Was the 594K Btu the 8'monster?
Perhaps your house needs a bigger monster.

>I have need of 2160 heating hours a year in this climate, which is modest
>compared to the North.

Agreed... Now how much oil do you use in a season?
Tell me that, and we can size your sunspace.

>Now the furnace is a demand system, and only runs
>when the house temperature drops, but it certainly runs more than
>2 hours a day total, so the little water closet is insufficient.

Perhaps you need a bigger WC, when the sun is not shining.
But the closet size has little to do with the size of the sunspace.

>That's particularly true when you realize that it is starting at
>a small delta T

I figure the closet water starts out at a steady-state temperature of 130 F,
after a string of average days, with some sun, and the house air is 70 F,
ie the delta T is 60 F to start with.

>and that delta is declining as heat is extracted, making the heat
>extraction slower and slower so that you really can't get all that
>heat back into room air in a reasonable on demand fashion.

In the useful stored heat calc above, I figured the final closet temp
as 80 F, ie a final delta T of 10 F. Now suppose the hot water is stored
in 245 sealed $5 55 gallon drums, each having a surface area of 25 ft^2,
and suppose the slowly moving air in the closet makes an R-value at the
drum surface of 2/3 ft^2-Btu/F. Then with a 10 F delta T and a large
airflow volume, the heat transfer rate will be

(80F-70F) x 245 drums x 25 ft^2/drum /R=0.666 = 92K Btu/hour,

so at the end of its discharge life, this closet could supply in one hour,
roughly the same amount of heat that Nisson and Dutt's house used in a
whole day, but at the end of its discharge life, it can only supply heat
at 1/3 the rate of a 275K Btu/hour furnace... 

Not a high enough rate? OK, suppose we use 2 liter soda bottles instead
of 55 gallon drums. These have an area of about 1 ft^2/bottle, and a 16'
monster cube closet would contain about 50,000 of them, costing 10 cents
each, if new, stacked up in the hard plastic boxes that cost $2 each,
the ones you see stacked in the aisles of supermarkets. This monster would
be a more efficient solar collector, and at the end of its discharge
life, it would have a heat transfer rate of about

(80F-70F) x 50,000 bottles x 1 ft^2/bottle/R=0.666 = 750K Btu/hour,

ie it could crank out heat at 3 times the rate of the 275K Btu/hour furnace,
at the end of its discharge life. If we say that the end of the closet's
discharge life occurs at 100 F, it could replace 9 of those furnaces, in
terms of heat transfer rate. If we made the closet air velocity 10 mph,
(ie 880 fpm) and the bottles had a rough surface, the R value would decrease
to 1/(2+v/2), ie 1/7, and at 100F, we could replace 42 of those furnaces.
(We should also check how much airflow volume is needed for heat transfer.)

>Now a *large* thermal mass would do better, of course...

Hmmm, *large*... There's a lot of empty space in the middle of that new
administration center in Paris... :-) A solar closet L' on a side takes
about L^2 days to cool to 70 F, with no sun and no other heat load, in
32 F air. A hundred foot cube would take about 10,000 days to cool, ie
27 years with no sun, at 32 F. A mini ice-age. It seems to me that the
critical thing is the heat transfer rate, not the amount of thermal mass,
since the closet only supplies heat to the house when the sun is NOT shining.
In sunny times, the sunspace heats the house. 

>but even it won't supply *days* of even heat as was claimed for
>the little water closet.

Are we talking little monsters or big monsters now? It is not hard to
calculate how many days of heat a given closet can supply, if you know
the thermal characteristics of the house, or your yearly heating bill. 

Nick

---

From: [email-masked] (George Goble)
Date: 8 Oct 1995 12:37:29 GMT

>If they are pre-filled, are you sure it's water inside?

sealed at the factory.  It is water.. You may be able to special
order other fluids or water/glycols.. not sure.
 >putting them in racks or on shelves or whatever)? Or am I missing

It is ball shaped, with many flat "faces" on it.. Thick sturdy plastic.
You just dump 'em in a tank or pile and circulate your working fluid
(brine,  air, etc, thru the pile).  IT is designed for thermal
"cold" storage, not heat  storage.. sold by the "ton" (of refrigeration
effect).

If you just use a chiller to freeze water in a tank, then the
coils ice up first, impeding heat transfer from the rest of the
water.. With iceballs, you cool a working fluid, such is glycol/water,
and pump that thru the iceball tank.. and have no such problem as
the  coil freezing first, insulating it.  The glycol can remove
heat evenly throught the whole tank of iceballs..
 
 >least 20 years old and don't leak. So maybe metal is better than
 Those have real thin plastic.. iceballs are much sturdier.
 >uwvax!astroatc!nicmad!madnix!zaphod
--ghg
http://ghg.ecn.purdue.edu
http://worldserver.com/R-406A

---

From: [email-masked] (William Bahnfleth)
Date: Sun, 8 Oct 1995 20:03:36 GMT

George Goble wrote:

>In article <[email-masked]> [email-masked] (Ron Bean) 
> >>fill a tank with iceballs for thermal storage.

...

>heat evenly throught the whole tank of iceballs..

Of course, the ice balls are freezing from the outside in, which also reduces 
the heat transfer coefficient.  As the charge cycle proceeds, the leaving 
temperature from the tank falls, indicating that this is the case.  Toward the 
end of the cycle, chiller loading (and with it, efficiency) drops off 
precipitously because there is no delta T across the evaporator.

Bill

--
William P. Bahnfleth
Department of Architectural Engineering
Penn State University-University Park
[email-masked]