Why no heatpump refrigerator combos?

[oz93666]

A big push for (air) heat pumps in the UK ... The outdoors unit has refigerant exiting the expansion valve at around -20C , it would be an easy afair to wrap a copper tube around this larger outlet copper tube from the expansion valve before it reaches the radiator , in effect creating a secondary heat exchanger with salt water pumped through it , this could enter the kitchen and enter the fridge freezer and another heat exchanger ... This may only be feasable where the outside HP is in close vecinity to the kitchen , but the saveings would be around 400KWHrs/year , and it would increase slightly the overall efficiency of the HP.

 

[OmCheeto]

Thank you for the for me a delightful Sunday morning maths quiz.
Your 400 kwhs/year yields me a per day savings of ≈0.2 euro.
As an old yank, I'd bend over to pick up two dimes.
But....... I spend more on a single sushi order than what your system would save me a year($80).

Quite the planetary quandary/conundrum/dilemma/problem, I must say.

 

[Lnewqban]

The outdoors unit has refrigerant exiting the expansion valve at around -20C...

Are you describing the heating mode?
If so, your wrapped-tube heat exchanger would be slightly increasing the temperature of the refrigerant entering the outdoor unit, reducing the amount of heat that unit can suck from the atmospheric conditions.

That is assuming that the low thermal load of the refrigerator in winter is demanding any help for cooling and starting the circulation pump.

 

[sophiecentaur]

it would increase slightly the overall efficiency

"Overall efficiency" would need to take everything into account. The kitchen fridge has the effect of warming up the kitchen every time the motor runs. If you pipe cold water to the fridge condenser coils then, yes, the motor would run less but you would need extra power to maintain the kitchen temperature when the motor is not running.

saveings would be around 400KWHrs/year

That's around 1kWh a day. Can you show your calculation to arrive at this figure? A scheme like this would involve 'co operation between two different domestic systems, with a fluid pumped between them and the supply companies having to talk to each other to arrange this and ensure that the system worked to the satisfaction of both. Would that be 'good' engineering? Best to keep your services as separate as possible.

I'd rather use anti-freeze mixed with the circulating water; it's designed to avoid corrosion.

 

[Ken Fabian]

I think that level of integration may have it's place in larger systems - the larger multi story residential and commercial buildings and businesses that provide central heating and cooling or do lots of refrigeration. It seems like refrigeration is just one element, possibly not the easiest, that could be combined to improve efficiency. I think not so much in suburban domestic situations.

It does seem to require planning and designing and will work best when building are made to support it. Mostly Combined Heat and Power systems use fossil fuels, increasing their effectiveness and reducing emissions but are ultimately incapable of elimination of emissions.

I did encounter the idea of ducting the cold air produced by heat pump hot water systems into homes for Summer cooling here in Australia - kinda the inverse of exploiting heat from refrigerators - but you would have limited control over it (maybe thermostat controlled vents?) and it would probably be inadequate, ie a regular A/C system is still needed, in which case it is easier to just rely on the A/C - which is a heat pump with good efficiency.

Ease and convenience do count for a lot. With our rooftop solar we have energy far in excess of our needs - although an EV will use much of the excess (one day, not too far away?), but still leave us ahead, by the reduced energy use for our car.