Energy savings: thermal storage of still warm gray wastewater in a cellar or isolated room?

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Christophe
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Energy savings: thermal storage of still warm gray wastewater in a cellar or isolated room?




by Christophe » 27/08/22, 18:21

Given the exploding energy prices (even if it's difficult for some...in the end it's a good thing for the environment and it revives good ideas like the one in this subject 8) ...Macron said it: the end of abundance, you know what!) so I'm reviving this old idea of heat recovery from gray water already discussed on forum years ago and in multiple topics (do a search)

A shower is 2 kWh on average (see calculations here: https://www.econologie.com/calcul-cout- ... chauffage/ ), a 250L bath is 8 to 10 kWh, a washing machine from 2 to 4.5 kWh, a dishwasher about 1 kWh (various sources on the internet)...the idea would therefore be to thermally buffer the gray water in an isolated enclosure of the house in order to recover the residual calories...

For a family of 4 people, we can therefore arrive at several tens of kWh which go into the gray water every day... if it is 20 kWh, it is the equivalent of 2.5 L of fuel oil (corrected yield)! Over 6 months of heating season it's 350L equivalents that can be saved, it's not nothing at all!

There have been (publicized) attempts to recover calories from the siphon, but it doesn't work well: it's expensive, so it's not profitable and it's full of hassles (clogging)!

View: water-pumping-filtration/heat-recovery-from-the-shower-a-french-distinguishes-t11302.html

So why not, much more simply, make a buffer tank of a few hundred L in an isolated place in the cellar, crawl space or another room in the isolated volume in order to passively recover these calories while the still hot gray water cools down? :?: :?: :?:

For the necessary volume, it would suffice to take that of your largest bathtub and apply a coef to it. of 1.5 which seems more than enough to me...in short, 500L will be more than enough!

There remains the concrete practice: there will inevitably be dirt which will end up accumulating in the buffer and it will therefore be necessary to provide for easy cleaning...(once a year max that would be good...)

Plan ideas?

ps: I admit this subject is not innocent, I have just insulated the walls of my crawl space and I have an apparent gray water evacuation! So it tickles me to test the idea! Depending on the house, the difficulty will be to centralize the evacuation of all the gray water... or else you have to put several buffer tanks... to be seen!
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Re: Energy savings: thermal storage of still warm gray wastewater in a cellar or isolated room?




by GuyGadeboisTheBack » 27/08/22, 18:23

It's not just the calories that need to be recovered, the fleet too.
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Re: Energy savings: thermal storage of still warm gray wastewater in a cellar or isolated room?




by Christophe » 27/08/22, 18:29

Yes absolutely, well agree and one does not prevent the other!

Although recovering the fleet when you shower at Tahiti Douche or other filthy chicks (oops...) from L'Oréal et cie, I'm not sure that the vegetables or your garden in general appreciate...for the WC possibly but there the hydraulic assembly is a gas plant...

Read the article on the cost of a shower, I had distinguished the price of water and kWh (at the costs of the time...)

https://www.econologie.com/calcul-cout- ... chauffage/
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Re: Energy savings: thermal storage of still warm gray wastewater in a cellar or isolated room?




by sicetaitsimple » 27/08/22, 18:52

Christophe wrote:So why not, much more simply, make a buffer tank of a few hundred L in an isolated place in the cellar, crawl space or another room in the isolated volume in order to passively recover these calories while the still hot gray water cools down?


To be sure you understood correctly, do you "just" want to install a tank in which the gray water arrives, the heat recovery being done without an exchanger, only by convection/radiation from the walls of the tank?
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Re: Energy savings: thermal storage of still warm gray wastewater in a cellar or isolated room?




by Christophe » 27/08/22, 18:54

That's it...hence the fact of:

a) install the thing in an isolated room or better in the heated enclosure (like a storage room behind the kitchen...)

b) have a fairly large volume (depends on the consumption of the occupants)

The "new" waters must stagnate long enough to diffuse all their calories...a well-made tank should do the trick...ideally aluminum! : Mrgreen:
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Re: Energy savings: thermal storage of still warm gray wastewater in a cellar or isolated room?




by Macro » 27/08/22, 19:03

And recover only the hot gray water...a washing machine sends out hot water just after washing...The 5 or 7 rinses are cold...
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Re: Energy savings: thermal storage of still warm gray wastewater in a cellar or isolated room?




by Christophe » 27/08/22, 19:19

That's unmanageable Macro...well yes, but super complex to set up because you have to detect the cycles of the machine and each machine has its own cycles...big mess to manage in perspective (same for the using cold tap water...) : Shock: : Shock:

It doesn't matter: the rinsing water comes out lukewarm at least at first and...if the volume is large enough it doesn't change the overall calorie recovery...it will just take a little longer... .

Obviously you should not put the thing on a tap that comes out only cold water with large volumes ...
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Re: Energy savings: thermal storage of still warm gray wastewater in a cellar or isolated room?




by GuyGadeboisTheBack » 27/08/22, 19:26

Christophe wrote:Still recovering the fleet when you shower at the Tahiti Shower or other filthy chicks (oops...) from L'Oréal et cie...

None of that with us. Aleppo soap (20, 30, 40% bay laurel oil), organic shampoos in soap bars, 100% natural toothpaste and basta.
Otherwise, I put a thermostat tap to supply the washing machine and the dishwasher, heated by the solar water heater.
Last edited by GuyGadeboisTheBack the 27 / 08 / 22, 19: 31, 1 edited once.
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Re: Energy savings: thermal storage of still warm gray wastewater in a cellar or isolated room?




by sicetaitsimple » 27/08/22, 19:31

Honestly I'm not convinced... Because all these waters (except washing at 60°C) are roughly at 35°C maximum, part of it is also cold water (see Macro's remark but also washing water in the kitchen for example), it will get cold during the trip to the ferry,...
In short, I think that the average temperature of the tank will not be huge and that the power exchanged will be minimal since it is supposed to be in an isolated volume of the house.
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Re: Energy savings: thermal storage of still warm gray wastewater in a cellar or isolated room?




by GuyGadeboisTheBack » 27/08/22, 19:34

In winter, we leave the water in the bathtub until it is cold, so we recover the calories directly in the bathroom. (In summer we don't wash... : Mrgreen: )
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