Solar wall with thermal mass of inertia?

Solar thermal energy in all its forms: solar heating, hot water, choosing a solar collector, solar concentration, ovens and solar cookers, solar energy storage by heat buffer, solar pool, air conditioning and solar cold ..
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phil53
Grand Econologue
Grand Econologue
posts: 1376
Registration: 25/04/08, 10:26
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by phil53 » 23/04/12, 12:03

Here are the promised references:
The Solar House Guide
by Edward Mazira
Brackets edition
24th is on Priceminister or Amazon for a little less

Not too much of your opinion Lietseu
What was already usable in the 70s has remained at the experimental stage.
Today all new homes should incorporate this principle while we are still at the same stage as 40+ years ago.
So some elders understood but not all, 1 in a million.
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FALCON_12
I understand econologic
I understand econologic
posts: 147
Registration: 20/04/12, 18:58
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by FALCON_12 » 07/05/12, 11:35

Here are the promised references:
The Solar House Guide
by Edward Mazira
Brackets edition
24th is on Priceminister or Amazon for a little less




Thanks Phil! :P
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dedeleco
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Econologue expert
posts: 9211
Registration: 16/01/10, 01:19
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by dedeleco » 07/05/12, 14:44

FALCON_12 wrote:

Yes Mr Perrier had planned one, his small assembly with AOP is a hysteresis comparator which controls the fan. But I saw that you could also use simple convection. Again, I am not sure what is important. Simple convection is practical: no fan, no electronic circuit: fewer potential failures. Less hassle and less work ...

Without a fan it will have less heat exchange, in my opinion. So it would probably be necessary to dimension the sensor differently: give it a larger exchange surface. But how big? I am not a thermician. I can do thermal calculations to size radiators for electrical components, but it looks different. Anyway, I'm thinking.


This is calculated, in order of magnitude quite easily, first of all the heat stored in a wall (low between 3 to 10KWh / m3 roughly according to the variations in T, about 1 kilo of burnt wood, often less)
Then the phase shift which is really the diffusion of heat, very complex if we want to be precise, but simple in order of magnitude, with diffusion with penetration on a depth, like the square root of the time spent broadcasting, so slows down quickly, typically D <= 1mm2 / s often:
http://fr.wikipedia.org/wiki/Diffusivit%C3%A9_thermique
with all the necessary values.
For concrete or earth, clay, as simple and cheaper, and more ecological, we store on this increasing thickness as the square root of time, ie 1mm in 1s, 10mm in 100s = 1min40s,
100mm in 10000s or 2h, 77
1m in 1million seconds, or 11days22h.
if D = 0,1mm2 / s (humus, wood etc.) then the depth is reduced by the rax factor (0,1) = 0,316, therefore max of variations, a factor 3 below.

With the course, especially for an unlimited domain in Fourier series:
http://fr.wikipedia.org/wiki/Conduction_thermique
above all we get the factor pi dividing time t = T for periodic oscillations of period T giving a depth of penetration
as delta = rac (DT / pi) in delta = rac (2.D / 0mega) with the pulse Omega = 2.pi / T
http://fr.wikipedia.org/wiki/Diffusivit%C3%A9_thermique

for a 24 hour day = 86400s and D = 1mm2 / s, (compact earth clay), this gives an exponential penetration of the oscillations between day and night of
delta=rac(1.86400/3,14)=165mm=0,165m=16,5cm

So if you want to store the variations of T well, the sun by day for the night, it is useless to take a thickness greater than this value (to correct the true value of D for the chosen material, a factor of 3 between marble or granite and wood).

Finally the heat stored is that on the volume in this depth of penetration, or with a specific heat of 1KJ / dm3 ° K = 1MegaJoule / m3 ° K, (about that of clay, variable according to its origin and twice as much for concrete see the table:
http://fr.wikipedia.org/wiki/Diffusivit%C3%A9_thermique
) we obtain with 0,165m and 36 ° C of variation, between day and night (a lot) 10KWh / m3 and for 0,165m of depth 1,65KWh / m2, very little 1/3 of wood burned in a stove.
The value 36 ° C is excessive (taken because of 3600s / h for simplicity), and is rather half, which means that such a wall stores little per m2 between day and night sun, and is only useful in a very very isolated house, requiring very very little heat.

Daytime heat can be increased by convection or air or water circulation over a much larger storage area of ​​about 16cm thick.

But the volume must be high typically more than ten tonnes, 10 times more than for a mass stove which gives a variation of T 10 times higher than this passive sun.

Finally the same method can be used to store between seasons, summer heat for winter, free underground, more than 3 to 6m deep, as functional since 2007, at
www.dlsc.ca
here can heat 52 houses completely in winter at 20 ° C, (but not totally domestic hot water, because you want too hot in winter to wash, 60 ° C)
and discussed on:
https://www.econologie.com/forums/chaleur-d- ... 10828.html
https://www.econologie.com/forums/stockage-d ... 10173.html
https://www.econologie.com/forums/stockage-i ... 11366.html

The inter-season storage volume, on earth is measured in 500m3 to thousands of m3 per house, depending on the thermal insulation of this house, but free land allows this by drilling every 2m or so, over a volume of almost spherical shape, to reduce losses by surface diffusion.
The summer sensor can be very inexpensive for large areas, simple 16mm polyethylene pipe, a little insulated below, and in plastic film.

Finally all CO2 and nuclear can be replaced by this shallow geothermal solar solution, by developing it with a research cost much lower than the price in addition to developing the EPR, for heating, free to perpetuity, without CO2, without radioactive pollution, or nuclear disaster, emptying an entire region for centuries !!
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