Subject: Re: Solar storage tank design

From: [email-masked] (Nick Pine)
Date: 26 Mar 1997 00:34:40 -0500

Tvoivozhd <[email-masked]> wrote:

>...don't even think about a wooden tank.

Plywood tanks lined with EPDM rubber have been used for off-peak storage in
electric resistance house heating systems for years. Sven Tjernagel of STSS
(477 Woodcrest Drive, Mechanicsburg, PA 17055, USA) started making something
like tallish prefabricated steel circular swimming pools lined with EPDM and
foam when UL wouldn't approve site-built plywood tanks. (Sven built hundreds
of 10x20' solar collectors out of EPDM rubber bladders as well.)

>Go to the local library and have the librarian get on interlibrary 
>loan the two Ken Kern (deceased) books on "Owner-built home" and
>"Owner-built homestead".  Much cheaper, much better, much easier...

Perhaps not, for a 1000 gallon tank inside an existing garage.

>...think about using a phase-change material like Glauber's salt...

>From  what I've read, Glauber's salts get tired of changing phase after a few
hundred cycles, and have to be mechanically stirred up, or something, to help
them keep working. Corrosion, cost and getting enough thermal mass surface
area for charging with solar-warmed air without lots of electrical power for
fans and blowers can also be problems. And I've read that phase change waxes
catch fire, and often need to be stored outdoors, building-code-wise... 

>...I've forgotten the math, but phase-change materials occupy a lot smaller
>space than liquids---l/l0th?, l/20th?----and size of installation translates
>directly to cost.

How about water phase change in a lithium chloride solution? Cypress-Foote
Mineral sells LiCl for about $4/pound, and it can absorb 12X its weight in
water, at 1000 Btu/lb vs about 50 Btu/lb for sensible water heat storage, so
100 lb might store 1 million Btu for a cloudy week, in a house with lots of
internal thermal mass and external insulation, which can keep itself warm
with a low-thermal-mass sunspace for 24 hours over an average winter day,
with an average amount of sun. Put a solar still in the sunspace, store
concentrated LiCl in 2 uninsulated plastic 55 gallon drums in the house, and
let the LiCl somehow absorb water from a damp basement floor or an indoor lawn
as it evaporates with ground-coupled heat on a cloudy day?  

Then again, an all-masonry house with exterior insulation can have an RC time
constant of several weeks (and 1/3 the fire insurance rate), so all it needs
is a low-thermal-mass sunspace with lots of glazing, which gets cold at night.
Who needs more thermal storage? 

Nick

From Box, 830, Petersburg, AK, 99833 Thu Mar 27 21:53:22 EST 1997
Article: 1876 of alt.solar.thermal
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From: "Judith R. Sarber" <[email-masked]>
Newsgroups: alt.solar.thermal
Subject: Freezing water supply
Date: Wed, 26 Mar 1997 01:59:20 +0000
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Need some suggestions for keeping my water supply from freezing.  I 
collect rainwater off roof and store in cistern in back shed, which is 
only protection it gets at this time.  I can't sink a tank under the 
house because I only have 18-inches of overburden and hard shale 
beneath.  I live off the grid so there is no electricity.  I must leave 
my house for trips of 6-21 days.  Most of the time I have no problem, 
but when I am called out on a trip for several weeks in mid-winter, I 
must drain the system "in case" the weather turns cold.  Cold in this 
area is zero to 25-degrees, but cold weather means sunny weather.  I 
have "good" solar available for only 2-3 hrs during deepest winter.  
Does anyone have any suggestions?  I heard recently about a water 
container that can be put out for birds during winter, which has 
"channels" that prevent the water from freezing except during very cold 
periods.  Has anyone heard of this? or know of the principle behind it?

---

From: Will Stewart <[email-masked]>
Date: Wed, 26 Mar 1997 21:22:07 -0500

Nick Pine wrote:
> them keep working. 

That was a problem years ago, but has since by rectified by various
additives.

> Corrosion, cost and getting enough thermal mass surface
> fans and blowers can also be problems.

Direct gain is a perfect application of phase-change materials.

> And I've read that phase change waxes

I know people who use phase change waxes in storage tanks in their
homes.  Could you cite a building code that prohibits this?
 
Cheers,
-- 
William R. Stewart
http://www.patriot.net/users/wstewart/first.htm
Member American Solar Energy Society
Member Electrical Vehicle Association of America
"The truth will set you free:  - J.C.

---

From: [email-masked] (Bruce Hamilton)
Date: Fri, 28 Mar 1997 08:22:33 LOCAL

In article <[email-masked]>

>homes.  Could you cite a building code that prohibits this?

A couple of decades ago, wax filled storage heaters were 
banned from NZ houses after a series of fires. Most of the
fires were from one brand ( Skope? ). I'm not certain if they
still are banned, but they were replaced with ones filled 
with thermal bricks or oil-filled units. There has been some
very interesting developments in high specific heat bricks
in NZ that can hold a lot more heat per unit volume and
mass, but I don't think they are on the market yet.

        Bruce Hamilton