Bulbs in Fridges

[Paulh_Boats]

We're actually only looking at 72days of the year which when we'd need to use alternative cooling.

Maybe that explains how our grandparents coped with a larder with outside air vents top and bottom!  We could be reinventing the wheel 

[martin]

my aged granny had a traditional larder (north facing) with a perforated zinc "top window" - it had a marble slab, and she quite happily lived for many years without a 'fridge - from memory the only noticeable difference was that once in a while there'd be a few milky floaters in tea in the height of summer - I doubt it did her much harm as she made 95!
It does make me think that fridges/freezers are firmly in the "luxury" department - we CAN very easily "do without"

[EccentricAnomaly]

On the other hand, if a fridge/freezer allows fewer car shopping trips then they may well be worthwhile. 

Aged grannies probably got fresh produce every couple of days.  Larger households probably contributed to making this more efficient by increasing the rate at which produce is used and the chances that some member of the household would be out in the vicinity of a shop anyway.

Putting an already-efficient chest freezer in such a cool store should be very efficient as there's less heat to leak in and the heat pump has a smaller thermal hill to push what does get in back up again.  With intermittent off-grid power this would be particularly valuable as the freezer contents would warm up more slowly so there'd be more choice as to when the freezer is run allowing a larger proportion of use when the sun's shining or the wind is blowing.  Running a fridge or freezer off batteries is madness given that the energy density of thermal storage is nearly as great as that of batteries but a lot cheaper.

[EccentricAnomaly]

Looking at this data: http://www.rothamsted.bbsrc.ac.uk/broom/weather/nweathermenu.php (between Newmarket and Bury St Edmunds).

There were 78 days in the year when the grass temperature stayed above 10°C which matches pretty well with what Ivan found.  On average, the minimum grass temperature was 1.9°C below the minimum air temperature.  There were, however, 39 days when the minimum air temperature was lower than the grass temperature.

[Ivan]

I agree - larders are a good idea - but convincing 59million people in the UK that they're worthwhile is probably going to be difficult, and also difficult (perhaps I should say 'costly' rather than difficult) to engineer into many houses. Mostly, the problem is people's reliance on the refrigerator, and the habit of using fridges.

I did wonder a few years ago, about using a hole in the floor leading to boxed volume in my underfloor area (cold), with a rack containing goods for refrigeration that slides up and down as required.

If it was cheap to convert existing fridges with minimum of fuss (2 insulated micropipes, small pump and controller) I can see potential uptake.


Here's another take on it:
The other thing we've not factored in is thermal mass. If it were possible to include an element of thermal mass in the system (eg insulated cold storage (eg insulated tank of water outside the house), then you could store several days' worth of 'coolth'. Anyone got any figures for daily kWh consumption of fridges? My (old) Fridge/freezer consumes about 1kWh/day of electricity. The compartments are equal size, but the fridge gets opened more often than the freezer- let's say 0.5kWh per day is for fridge. Let's say CoP is 3 (I've no idea what an average fridge CoP is), then that's 1.5kWh/day of heat that needs to be removed. I suspect I've over-estimated, and in fact the freezer takes a greater proportion of the overall energy consumption.

10litres of water, if frozen will store 1kWh of 'coolth' through change-of-state (ie will require 1kWh of heat to change back to a liquid). So 100litres of water will store 10kWh of 'coolth' plus the energy to heat it up to 10C adds another 0.1kWh. So if we get a night below freezing, and we have sufficient radiator area, we can store 11kWh of 'coolth', which equates to over 7days refrigeration (USING A BOG STANDARD REFRIGERATOR ). Of course, this won't help in the summer, greatly.

[martin W]

Hi Ivan,

only have data on a Bosch Fridge Freezer - about 1.2KWH per day in winter and 1.8KWh day in summer. I wounder if if it worth sealing the back of a fridge / freezer to some insulation and then open the back up (vent lower and top) to the outside. Would this increase the efficency?  How about 12" of solid insulation around an exisiting fridge?

just musing...

[Ivan]

My first thought is that letting the cold outside air get directly to the cooling fins on the back can only be a good thing. In fact, for years, I ran my freezer in the garage during the winter, and off during the summer. My current freezer is in the porch - which is usually around 10C cooler than the rest of the house during winter, and about the same during summer (we leave the door open to gain the extra heat).  However, I noticed in the manual of the new freezer, it says you must not use it when ambient air temperature is below 10C. Not sure why - maybe it's to do with condensation inside the body which would cause rust? Maybe it will interfere with the 'hot' side of the refrigeration cycle?

The insulation around the freezer is also a good idea (as long as there is good air flow to the back of the freezer). However, I found on my old freezer, that the return pipe from the cooling fins passes along the right hand side of the unit - obvious as it's very hot. So insulating this bit will actually make it less efficient - which doesn't seem logical at first.

My old freezer used around 1.25kWh/day. My new one uses 0.25kWh. The most striking difference is the thickness of the walls - extra insulation.

[kristen]

"it says you must not use it when ambient air temperature is below 10C"

Is it because the refrigerants they use now are designed to operate, optimally,at room temperature?

[alfie]

Quote ''A modern electronic temperature control (typically with a display) would have to use some power, but only a very little - probably too little to show on a simple/cheap/retail "meter-plug". So not zero, just too little to measure with the tools at hand''

My inverter switches to standby  when the demand falls below 15 watts.  so when I say the fridge uses no power when not cooling I really mean it. 

[guydewdney]

Can someone please tell me how I can store this woolly mammoth? I have just clubbed it over the head with my trusty all organic wooden club - which I chewed from the round with my teeth (no tools - see) and its started to go rotten. The sabre tooth tigers are circling at the edge of the fire light.... help!





Oh - sorry - this isnt the caveman forum? I got confused -typing on my laptop, made of plastic, copper, silicon, gold, silver......

[Amy]

How can I be sure the light goes out when I close the door?
My brake lights never work when I get out to check them.