Waste heat recovery and ground sourced heat pump.

 Has anybody tried to recover the heat from
domestic waste water ( is that what is
meant by greywater in America?) to pump
back in to the cold end of a ground
sourced heat pump?

Nick Rouse

 

 Yes.  I have a vertical heat exchanger in my main waste line.  In the US,
'greywater' is a term to refer to the waste water from showers, washers and
sinks (the dirty soapy water is 'grey').  'Blackwater' would refer to waste
from toilets.

Depending on the inlet temperature of the water to begin with, recovering
energy from the greywater can be quite cost effective.  But it seems to be
rare that anyone thinks to do this.  This company makes the type of heat
exchanger I have:

http://www.gfxtechnology.com/

Nick Pine has been looking into building a slightly different design.
Hopefully he will keep us posted as to his progress/ success.

But the flow of water down the drain is pretty intermittent and don't know
if you could really use it in a heat pump system for central heating.  Or
perhaps you meant just a heat pump for water heating?

daestrom

 Here's a simple but perhaps messy way...

Put the bathtub and sink drain plug in, and hold the water unitl it has
cooled to room temperature.
Then again, if you run more hot water trying to clean up the soap scum,  I
guess that would be a loss unless you hold it til it cools also.

 
Thanks very much for the information
I have my heat pump mainly for underfloor
heating but I have got it so the flow can be diverted
to a coil in the hot water tank which I use in  
mid winter and before dawn the rest of the year before the solar
thermal kicks in. I fitted a motorised diverter in the feed to the
ground loops in the hope of some day putting some heat recovery
system in.
Do you filter your greywater before the heat exchanger or
do you have a port to rod it out if it blocks

Thank for any help
Nick Rouse

 

The GFX unit that I have requires neither.  The waste side is a straight, 4"
diameter copper pipe.  Being vertically mounted, water just clings to the
sides as it falls through it.  Any debris in the waste stream simply falls
through as well.

daestrom