I’ve been thinking about the refrigerator. You’re probably not going to like this one, because as I did here and here, I am again going to wind up being contrary to what seems like common-sense green thinking.
The winter before last, my fridge compressor was broken for ten days (aside: good luck getting warranty service from Amana, Inc.) This was inconvenient, but we managed to keep the fridge functioning pretty well as an icebox. I filled three or four big tupperware containers with water, and rotated them from outdoors (where they froze to ice) to the fridge compartment (where they chilled the fridge, and melted). This is not a novel idea: my new heroes over at Experiments In Efficiency started living without a fridge altogether last year, using this same strategy in the winter (they put their food in a cooler, but same idea.)
During that broken-fridge episode, I started to feel that it was absurd to use electricity to keep things cold in New England, in winter. It seems there is no shortage of natural coldness available right outside, and that we should not be using electricity to make more.
But deeper thought shows things aren’t quite so simple. In fact, there is no “abundant cold”. Cold, indeed, does not exist– only the relative lack of heat exists. To “make” something colder, you have to move its heat somewhere else. The fridge cools its interior by moving heat to the room outside. Of course it also generates some extra heat in the process, exactly equivalent to the amount of electricity it uses. In effect, the fridge (like all electrical appliances) is a space-heater that happens to do something else handy along the way.
In other words, when you have the fridge plugged in, it pulls heat from the inside and puts it in the kitchen. As the heat seeps back in, the fridge pumps it out again. Each time, it adds a little “waste” heat. But in winter that’s not really wasted, since it helps keep the house warm, which you want also. As a way to heat the house, it’s not as efficient as using the furnace– unless I’m only trying to keep a couple rooms warm, in which case, it’s actually more efficient and cost-effective to “heat” the kitchen with the fridge than heat the whole house with the furnace (previous post on that concept.)
Now, consider the alternative strategy: unplugging the fridge and rotating containers of water outdoors to freeze. What this seems like is bringing a valuable commodity (cold) from a place where it is naturally produced (outside) to a place you want it (the fridge.) What it actually is, though, is taking a valuable commodity (heat) from a place you have produced it and want it (the house) and disposing of it in a place where it is useless (outdoors).
I know. This seems like whacknut thinking. But ponder it. Each time I brought in a tub of ice, and let it melt in the fridge, it drew heat from the fridge interior, which in turn drew heat from the kitchen, which ultimately was replaced by heat from the furnace. So the end product was a tub of water with a lot more heat than it started with when frozen. And then what? I took the tub and put it outside to cool off. I took perfectly good heat from the house (contained in water) and purposefully tossed it outside. And repeated for a week. (And this doesn’t even consider the heat-losing effect of opening the front door all those extra times to bring water in & out…) Really, this is wasteful in the same as filling the toilet tank with cold water, warming it to room temp, then flushing it down the sewer.
So it comes down to this: In winter, is it better to (a) unplug the fridge, make heat with the furnace, then throw the heat outdoors, or (b) run the fridge with electricity, but keep the heat it produces indoors? No longer such an easy question. And answerable only in considering that heating with a furnace is 2-3 times a more efficient use of fossil fuels than using them to generate electricity. So again, roughly, I’ve decided that if I’m only trying to keep 1/2 or 1/3 of my house warm, then electricity is as or more efficient than the central oil heat. And so long as that’s the case, it’s as or more efficient to keep the fridge plugged in.
There are two ways I can think of to short-circuit this whole problem and make the fridge actually efficient.
1) Bring ice/snow in from outside for the fridge, but after you’ve melted & warmed it up, don’t just toss it back outside with its heat. But this means you have to keep all that melt water in the fridge till spring… which starts to become unwieldy…
2) Run the fridge directly from fossil fuel in winter. This isn’t a loony idea. Propane fridges have been around forever. I’ve used them. They work great. Here’s one that can run off either propane OR electric. That fridge uses either 3.9kWH/day of electricity, or 1.1lbs of propane. As 1.1 lbs of propane contains about 6.9kWH of energy, at first glance it appears more efficient to use electricity– but only if you ignore the horrible efficiency of electrical generation in the first place. It takes about 12kWH worth of coal to generate that 3.9kWH of electric… the rest of the coal energy goes up the generator smokestack as wasted heat. Whereas, if you run the fridge with propane, every single kilowatt of energy it uses will ultimately stay in the kitchen as heat. Nifty, huh? Then in the summer you might want to switch back to electric.
Okay, bring on the rants.
P.S. Possibly the best thing about a propane fridge: No moving parts. No compressor. I wouldn’t have had to deal with Amana, Inc. and live without a fridge for a week in the first place…