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.

 

[sophiecentaur]

I think that level of integration may have it's place in larger systems

There's nothing new under the Sum. When `Battersea Powerst Station (London) was built, (in the 1930s) the cooling water was piped under the river to a 'new' Local Authority estate by Victoria Station and provided free heating to the residents. I worked with a guy whose mum lived in a flat there and he told me the residents were 'well chuffed' with not needing to carry coal upstairs. The flats are still there but the Power Station is now a posh shopping mall with equally posh apartments. The residents across the river have to make their own heating arrangements. Eric's mum would never believe the prices of some of her old neighbours' apartments now.

CHP is a very attractive idea - on the right scale.

 

[sophiecentaur]

still leave us ahead, by the reduced energy use for our car.

Only for so long, though. The Government have their beady ol' eyes on the possibilities of significant tax revenue from that scheme now they've encouraged so many users.

 

[Ken Fabian]

@sophiecentaur - I suspect my government will differ from yours and future governments will differ from present ones. Decarbonising looks vitally important to enduring prosperity as well as to remnant natural ecosystems to me and given the abundance of consistent top level science based expert advice, should be vitally important to policymakers applying due diligence as their duty of care.

 

[sophiecentaur]

@sophiecentaur - I suspect my government will differ from yours and future governments will differ from present ones. Decarbonising looks vitally important to enduring prosperity as well as to remnant natural ecosystems to me and given the abundance of consistent top level science based expert advice, should be vitally important to policymakers applying due diligence as their duty of care.

We must hope that the action they take will be a good compromise between treasury income and losing votes - as with the rest of our lives.

 

[sophiecentaur]

To avoid over-spending on electricity for your fridge, make sure you have plenty of air circulation at the back ; keep the coils well away from the back wall and never place it in a warm part of the kitchen.

 

[OmCheeto]

What would be nice would be if we had some data from various members as to how much energy their refrigerators actually consume, and the associate data surrounding said consumption.

Example:
In January of 2017 I collected data which indicated my refrigerator consumed 150 watts on average over a week. Average in house temperature was 66°F.

My bestie prior to that said she had a fridge that was much more efficient than mine so I let her dump it into my house and discovered that it consumed the exact same amount of energy over the course of several months, even though her fridge was 20 years newer.

SHOW ME THE DATA!

 

[jrmichler]

What would be nice would be if we had some data from various members as to how much energy their refrigerators actually consume

SHOW ME THE DATA!

Refrigerator bought new in 2002: 39 Kwh/month.
Newer refrigerator bought 2011: 35.8 Kwh/month.
Data is from a Kill-A-Watt power monitor.

Our total electric power consumption is 250 to 300 Kwh per month.

 

[OmCheeto]

Refrigerator bought new in 2002: 39 Kwh/month.
Newer refrigerator bought 2011: 35.8 Kwh/month.
Data is from a Kill-A-Watt power monitor.

Our total electric power consumption is 250 to 300 Kwh per month.

And your total power consumption per month would be?
And are your numbers over a full year, or a segment of a year?

 

[jrmichler]

From my electric bill for December 2025.

July was high because of air conditioner and dehumidifier. December and January are high because of furnace blowers. Electric dryer is used year around. Computers are turned off when not in use. All lights are LED.

The house was designed to be energy efficient. In 2022, we used 670 therms of natural gas for heating house, shop, and domestic hot water. That year had 9725 heating degree days (65 deg F basis).

 

[OmCheeto]

From my electric bill for December 2025.
View attachment 371298
July was high because of air conditioner and dehumidifier. December and January are high because of furnace blowers. Electric dryer is used year around. Computers are turned off when not in use. All lights are LED.

The house was designed to be energy efficient. In 2022, we used 670 therms of natural gas for heating house, shop, and domestic hot water. That year had 9725 heating degree days (65 deg F basis).

Thank you!
This thread reminds me of the Wizard of Oz; "just ignore the energy consumption behind the curtain".

 

[sophiecentaur]

Decarbonising looks vitally important to enduring prosperity as well as to remnant natural ecosystems to me and given the abundance of consistent top level science based expert advice, should be vitally important to policymakers applying due diligence as their duty of care.

We have suffered , over the years, from a too-even-handed attitude from BBC and others. This glaringly obvious fact of life (need to reduce carbon output) seems , only recently, to be accepted where it counts. I heard this or BBC R4 this morning without any correction from the interviewer. Refreshing but a very slow change in public attitude.

People will only make real changes to their lives if they are scared enough. That's a Catch 22 thing.