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Insulation beneath concrete slab---or not. - Page 5

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Posted by Duane C. Johnson on June 8, 2006, 9:57 pm
 
Hi Jeff;


 > I've just run some numbers and it looks to me like
 > storing heat for a  week is a difficult task.

Not so hard if the temperature is higher.
Say 600F or so. See some of my calculations:
http://www.redrok.com/concept.htm#storage

It's easy to reach these temperatures with tracking
solar concentrators.

 > Realistically, isn't it a better plan to store heat
 > for the night and oversize the collector a bit for
 > cloudy days, than to store heat for several days.

 >   Jeff

Duane

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Posted by Jeff on June 8, 2006, 11:30 pm
 
Duane C. Johnson wrote:


  That's beyond the reach of most of us. And most of us wouldn't want a
basment you could fry eggs on!

  I notice that you've mentioned a price of around $/square ft for your
hand made versions. What size have you been able to make and when can we
take look? How does this do on hazy or overcast conditions.

   If you are considering doing this commercially, I would think going
straight to some other form of energy would make more sense, than
storing all that heat. A competetor to PV makes a lot of sense.

   Jeff




Posted by Duane C. Johnson on June 9, 2006, 4:34 pm
 Hi Jeff;

 > Duane C. Johnson wrote:

 >>> I've just run some numbers and it looks to me
 >>> like storing heat for a  week is a difficult
 >>> task.

This is true if you are only thinking of storage
at low temperatures. High temperature storage is
significantly smaller with many extra benefits.

 >> Not so hard if the temperature is higher.
 >> Say 600F or so. See some of my calculations:
 >> http://www.redrok.com/concept.htm#storage

 >> It's easy to reach these temperatures with
 >> tracking solar concentrators.

 > That's beyond the reach of most of us. And most of
 > us wouldn't want a  basement you could fry eggs on!

Possibly.
However, we would not want 600F in the basement unless
the insulation was VERY reliable. I would rather have
this high temperature high performance storage system
just outside the north side of the house, (south side
for our friends south of the equator).

 > I notice that you've mentioned a price of around
 > $/square ft for your hand made versions.

Hmm, that was a guesstimate in 1996. I suspect that
figure is lower today.

 > What size have you been able to make and when can
 > we take look?

I'm a designer of solar trackers and haven't had the
time to do the hard work on a large scale design.
I recently have retired and will now have much more
time available to me to do this work.

However, I have, throughout the years, been working
on many of the components.

OK, the "total package: hasn't been built but each
of the parts has been worked on by me and others.

 > How does this do on hazy or overcast conditions.

Not so good, actually not good at all for those days.
But this is an engineering problem. We would want to
size the heliostats to be able to input enough energy
on the good days.

Not every location is suitable for these high
temperature high performance storage systems.

I find that cold northern climates are best suited
for these systems, such as Canada.

Locations like the southern sunny climates may be
more suitable to more conventional thermal storage
systems. Why, because they just don't need that
much heat storage.

Although the hotter climates could benefit from high
temperature heat storage for use with cooling systems.

 > If you are considering doing this commercially, I
 > would think going straight to some other form of
 > energy would make more sense, than storing all that
 > heat. A competitor to PV makes a lot of sense.

I agree whole heatedly. Something like a Rankine
engine (steam engine) used to produce electricity
stored in the power grid. See:
http://www.redrok.com/engine.htm#scroll

The total system I envision is an array of heliostats
and a dish, facing north, heating a high temperature
high performance storage system. With the high
temperature a lot of problems are solved making
domestic heating, cooling, and electric production
possible with high efficiency and low cost.

 >   Jeff

 >>> Realistically, isn't it a better plan to store heat
 >>> for the night and oversize the collector a bit for
 >>> cloudy days, than to store heat for several days.

Well I don't know?
Is it better to use a huge low temperature storage system
useful for only domestic heating or a high temperature
system that provides for a holistic home energy system?

 >>> Jeff

Duane

--
     Home of the $5 Solar Tracker      Receiver
    http://www.redrok.com/led3xassm.htm       [*]
   Powered by             \  \     \        //|
  Thermonuclear   Solar Energy from the Sun / |
Energy (the SUN)           \  \     \  /  /  |
Red Rock Energy             \  \     /   /   |
Duane C. Johnson   Designer  \  \  /  \ /    |
1825 Florence St  Heliostat,Control,& Mounts |
White Bear Lake, Minnesota    === \   / \    |
USA      55110-3364                ===   \   |
(651)426-4766        use Courier New Font \  |
redrok@redrok.com     (my email: address)  \ |
http://www.redrok.com   (Web site)          ===

Posted by Jeff on June 8, 2006, 8:53 pm
 JoeSP wrote:


Let's see concrete stores about .25 BTU for each degree F per pound

To store one therm you would need to heat 100,000 lbs (50 tons) 4 degrees

   So, in other words, think days, not months!!!

   Jeff


Posted by R L driver on June 8, 2006, 10:12 pm
 fryster@burntmail.com wrote:

I live in a house in the UK with concrete floors , they are freezing
cold all year round, and so we have to wear slippers. Its now in the UK
building regulations to have insulation ( 50 mm urethane foam or
similar) under the concrete. All of a sudden the concrete is warm!
steve the grease

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