Onoff

Full Oil Tank As A Thermal Store!

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Courageous.

 

And oil has roughly half the specific heat capacity and half the latent heat of fusion of water. And it's less dense so its volumetric versions of those figures will be worse still.

Edited by Ed Davies

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1 hour ago, Ed Davies said:

And oil has roughly half the specific heat capacity and half the latent heat of fusion of water. And it's less dense so its volumetric versions of those figures will be worse still.

OK so perhaps not the best idea then!

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If he needs an alternative to oil which will also (hopefully) not involve a rapid phase-change, as is not concerned by fire risk, I see that TNT has a higher volumetric heat capacity.

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I like the American solar forum, forget efficiency just make it BIG!

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6 minutes ago, Onoff said:

I like the American solar forum, forget efficiency just make it BIG!

 

Years ago there was a discussion elsewhere about big thermal stores.  IIRC, I suggested that burying an old milk tanker might be a reasonable option.  They are already insulated but it wouldn't be hard to add more insulation around them if burying one in some form of basement-like structure.  They hold around 8,000 to 9,000 litres, I think.  

 

 

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14 minutes ago, JSHarris said:

Years ago there was a discussion elsewhere about big thermal stores.  IIRC, I suggested that burying an old milk tanker might be a reasonable option.  They are already insulated but it wouldn't be hard to add more insulation around them if burying one in some form of basement-like structure.  They hold around 8,000 to 9,000 litres, I think.  

 

I looked into this, as well as large insulated stores within the thermal envelope. Couldn't make the numbers work.

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There was a house (I think in Passive House magazine) a few years ago that had a large cylindrical water tank as the central core of a staircase.  I can't remember the details but I think that worked OK to fill the short period when the house needed heating.  I remember thinking that it looked like a neat solution, putting the large thermal store pretty much in the centre of the house, extending up well into the first floor.  Unfortunately I threw out all my old copies of Passive House magazine as  apart of the ongoing "mass clear out"!

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1 hour ago, jack said:

Couldn't make the numbers work.

Yeah, if you try to store all the heating you'll need in the winter during the summer (e.g., http://www.earth.org.uk/milk-tanker-thermal-store.html ) then the numbers won't work. But there're long periods in the shoulder seasons (spring and autumn) when currently harvested energy just about balances your energy use averaged over a small number of weeks and even in the worst bits of the winter there's some energy to be harvested. My rather big bet is that a large thermal store will cover the gap from, say, early December to early February when there's a net energy loss from the house.

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to get best from solar thermal   you will need more than one tank ,if you are wanting more than just DHW

with different temp levels for the tanks -so you can always store the heat you are getting 

eg if main tank has a target  of 80c  -then days when you not getting 80c -it goes nowhere ,

so you need to have dif  target temp levels for the tanks   

also if using for ufh a way to send it directly to the floor in winter when temps from panels will be low and your tank temps have depleted 

I am working on this for my new house ,but price of tanks is always going to be the killer  when doing a cost comparison to a ASHP

but I think  you will be talking about 2 or 3 tanks with a total of 8-10,000 litres,(could be too much with near passiv house, maybe 5000 litre ), 

I think to get get all year round  supply  and 3 or 4  x30 tube panels 

I could be wrong --more work needed  yet 

I would like to do it that way --but doubt costs will stack up  by the time you have built concrete tanks in  the foundations /plant room 

 

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