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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
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
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.
||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...
||// a typical big fridge/freezer uses about 2.0 kWhr//
||Is that 2kW? Or 2kWhr/day, or what?
||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.
||// Is that 2kW? Or 2kWhr/day, or what?//
||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.
||Did you really mean that?
||If the pipe bursts, do you get a golden