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Comment by ajarmst | Hacker News Reader

Maybe you don't, but most people care---a lot---about the temperature of their dwelling (yes, to the resolution of a degree or so). And your friendly neighborhood microbiologist will be happy to discuss the implications of fridge temperature irregularity.

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And your friendly neighborhood electrical engineer will insist on having that discussion before finalizing a design for a fridge controller.

Yes, it's important o keep a fridge in certain temperature bands. But there;s a lot of timing leeway in those bands, and it's exploitable as a form of energy storage.

I have a five year old fridge whose defining features include a compressor that runs pretty much all the time at a lower current draw to reduce overall energy use (and keep it quieter).

An electrical engineer I believe designed that part of the system...

I don't think the microbiologist will object if the fridge is too cold for part of the day... it's not like we're storing the microbiologist's cell cultures.

We already waste a great deal of food. Having it too cold will damage food, as will too hot. Older fridges used a sawtooth cooling pattern (on/off) but newer ones, with fancier motors, have might tighter regulation. I'm sceptical of how much energy can be scavenged.

I'm sure with enough IoT you could delay motor start +/-30s across a region to smooth the tip of a load spike, but it sounds very complicated. How would end users be compensated for such a tiny shift in load? Isn't instaneous power demand a martingale process?

It sounds like it would be easier and cheaper to have a few batteries.

I wasn't suggesting making it so cold as to damage food. I also wasn't arguing against batteries.

If you were suggesting a refrigerator to run the cooling in the night so much so that it'd be able to sustain a safe temperature for many hours while conserving energy in the day, then yes, you were suggesting making it so cold as to damage food - a few degrees difference isn't sufficient to achieve what you want, and if your temperature fluctuates more than 3-4 degrees then the food either gets unsafely warm or gets frozen/damaged.

I wasn't suggesting that, no.

I was just generally arguing against the parent proposition as well.

Well, if you're a skeptic as to how much can be saved, you might want to look at the many "smart grid" studies, because this has been a hot topic for a while and is already implemented to a small degree.

Both of these problems can be solved by shifting the energy storage into a medium other than air: refrigerant. Store the compressed refrigerant in an insulated tank and use as needed. It's no different in principle from storing hot water in an insulated tank. Shift the load off peak.

> Store the compressed refrigerant in an insulated tank and use as needed

Congratulation, you just re-invented the wheel. Do you really fridge builder are that dumb ?

A lot of the power that a fridge consumes is related to the defrost of coils. I don't care when my fridge heats up the coils, so that would be an easy load shift for a fridge that would not change the interior temp one bit.

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