Refrigerators and freezers, or combinations of the two, are basically heat pumps. In the guts of the machine, there is a condenser. Increasingly, these are now compact, fan-assisted units.

What I propose, is an increase in the size of the condenser, about 1/3rd. This should be within a chamber. The chamber should be water-tight and have standard inflow-outflow fittings. The dead volume of the system should be relatively small, in the order of 1-5 liters. Then, in the kitchen environment, the freezer should be plumbed in upstream of other appliances.

Ideally, this should be upstream of the cold water inlet of a on-demand boiler. However, simply using it to warm the cold inlet of the dishwasher or washing machine will also help. That's the good thing, it's got standard fittings, it's adaptable, and you don't have to use it right away.

So what's the advantage? Well, a typical big fridge/freezer uses about 2.0 kWhr. So. By running the hot coolant through cool water we should gain a bucketload of efficiency. Say 20% less motor-on time? 2.0kWhr per day is worth about 20c. So a total running cost of 365*0.2 is about $73 per year and a saving in the region of $15. BUT fridges are around for ages, and electricity isn't coming down in price any time soon. AND, it should reduce the cost of heating water elsewhere... Say 0.4kWhr is recovered from the freezer and offsets the resistive heating used in washing machines/dishwashers. (I'm guessing that washing machines and dishwasher activity will, to some extent coincide) so that's another $2, then, if the house is air conditioned, you can take the combined saved loads off the cost of cooling most A/C units run about a 9:1 ratio of electricity input to heat moved, so $15+$2/2 (for only needing cooling half the year) divided by 9... nearly 1 additional dollar! it's the gift that keeps on giving. Well, it would if electricity were 30c per kWhr at least.
-- bs0u0155, Aug 21 2012

Thermal busbar Thermal_20busbar
My more ecumenical version. [Loris, Aug 22 2012]

Like most such, the problem with this is that houses/kitchens are not built as complete units.

Theoretically there are lots of ways to improve efficiency using combined heating/cooling, but executing them in a real world environment remains impractical.
-- MechE, Aug 21 2012


ah, but nowadays, fridges are plumbed in for all that ice-making jiggery pokery. So there's ALREADY a gold water feed. All you need is a one coming FROM the unit to another..... some tubing...
-- bs0u0155, Aug 21 2012


// a typical big fridge/freezer uses about 2.0 kWhr//

Is that 2kW? Or 2kWhr/day, or what?
-- MaxwellBuchanan, Aug 21 2012


I think it needs to be rigged so that the intermittent heat sinks (washers, etc) can accept the waste heat, but it can still be rejected even if they're not used.

Making the different units interface in a standard manner is also desirable.

See link for my version.
-- Loris, Aug 22 2012


// Is that 2kW? Or 2kWhr/day, or what?//

2kWhr per day.
-- bs0u0155, Aug 22 2012


Bleh! You do realise that kWhr per day expands to joules/second*hour/day? Your last paragraph would be much easier to follow if you just stuck to watts, and left out the dollars.
-- spidermother, Aug 22 2012


// a gold water feed. //

Did you really mean that?

If the pipe bursts, do you get a golden shower?

Don't answer that …
-- 8th of 7, Aug 22 2012



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