Heat exchange from ufh pipes in summer to DHW

[Jilly]

Just musing.

Is this a thing? Possible?

The house overheats in summer due to solar gain. Is it possible to harvest the heated ufh water from the warm slab when the ASHP is in (reverse) cooling mode for domestic hot water when I eventually get round to installing a heat pump? 

 

Apologies to @SteamyTea for the crappy grasp of physics 

 

I have LPG for the moment and have a pretty low bills, so will probably wait until the boiler expires before I change it, as the current system of opening windows in summer is bearable, and currently there is no space for a hot water tank.

 

Any Heath Robinson suggestions...?

 

 

[JohnMo]

You can get heat pumps that do it, forget the make but made in Italy. They a have the normal water connections and additional pair of refrigeration lines that go to second coil in the cylinder.

 

Or you can use a small water to water heat pump, they are available, connect via a close coupled tee to the UFH return piping.

[SteamyTea]

3 hours ago, Jilly said:

The house overheats in summer due to solar gain. Is it possible to harvest the heated ufh water from the warm slab when the ASHP is in (reverse) cooling mode for domestic hot water when I eventually get round to installing a heat pump? 

All that really happen is that the outside unit, instead of of blowing air though a very cold radiator, it blows air though a warm radiator.

To save that energy you would need to collect that warmed air as it exits the ASHP unit, then store it in something well insulated.

Not really feasable.

GSHP can be set up to warm the ground where the boreholes/slinkies are, but if you have moving ground water, the energy is just taken away.

You may find that an EAHP works better, it takes that warm air out the house, with that air replaced with outside air. Would probably work well where I am because the OAT is never that high, 28°C is a very, very, rare event, over 22°C only happens for a few hours a year, like today, but now, at 21:50, it is 14°C, with the house at 21°C.

 

It should be possible to design a system that can provide genuine air conditioning and recover that energy to heat DHW, while also providing UFH when it is needed.  I think the real problem is cost and complexity, basically switching from heating a slab in winter to cooling air in summer, two different mediums need to to piped and controlled.

Fain Coil Units in a forced air heating system may be one method that is a bit simpler, it works in offices.  But no one wants to 'loose space'' to large duct work.

But I would question how large that ductwork needs to be be a low energy dwelling, probably not as large as people imagine.

I am all for just heating the air in a building if possible, then you can forget about wet pipework, water leaks, over complicated controls, reliance of 'heating engineers' that do not understand heat pumps and it would be easy to fit another FCU or three to a larger heat pump if more heating and cooling were needed, then can run in series, one after the other in an insulated box.

[Nickfromwales]

53 minutes ago, SteamyTea said:

All that really happen is that the outside unit, instead of of blowing air though a very cold radiator, it blows air though a warm radiator.

To save that energy you would need to collect that warmed air as it exits the ASHP unit, then store it in something well insulated.

Not really feasable.

I've just parted ways with a strong-minded client who stated the the idea of Heat & Chill Recovery "pleased him", but I didn't get the opportunity to tell him exactly how much of a ball-ache heat and chill recovery actually is, plus (as nothing is for nothing) just HOW MUCH heat / energy has to be created as waste, so it can be uneconomically collected an diverted elsewhere. This works well in other climates, mostly Oz and parts of the USA etc, but would do the square root of feck all in old Blighty I'm afraid.

 

Sometimes you see a river bank with corpses of dead horses that refused to drink.

 

@Jilly

I looked into this for a client many moons ago, but the amount of energy you see as useful is actually too small to be viable to spend money on capturing and diverting.