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Comment by lawlessone | Hacker News Reader

This is a bit of tangent but could the heat from fridges be harvested?(maybe it already is by some companies?) Would it be worth it?

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If I remember from my engineering classes, the efficiency is based on temperature differential and the differential between the hot part of the refrigeration cycle and the ambient temperature I don't think is that high.

The house of the year 3000 might vent the waste heat into the water going into the water heater saving a little energy for your shower. It might time running the fridge compressor to when you make your coffee so it can use the waste heat to help heat up the water. Probably not cost effective until robots are building all the houses. Too many little pipes to run all over the place.

In winter by fridge vents hot air into my house. Unfortunately it also does it in summer ...

My house of the year 2024 already has a hot water tank that is using a heat pump to extract the heat from the ventilation air before it is sent out of the house. When you live in a cold climate this makes tons of sense.

Cold air enters the house, gets heated up to 22°C by a heat pump, circulates through the house, then gets drawn into the ventilation system where it is cooled back down to around 2 °C before going out of the house, and the extracted heat is upgraded to 60°C hot water. There is an electric heater taking the water further up in temp.

Our system is a retrofit, it draws around 1.2 kW peak and only provides hot water. For new builds, the bigger units drawing ~4kW peak are used, which provide both hot tap water and subfloor heating by water circulation.

I knew about the heat and cold recapture devices that allow for ventilation without a lot of thermal loss but I had no idea they made ones to heat water like that. Awesome.

Maybe - do you have a need to ship something that needs to be kept warm (not hot!) from/to someplace that also needs to ship something that needs to be kept cold? I can't think of anything like that but I'm sure it exists. However the logistics of getting that supply chain and the medical supply chain next to each other is hard.

>do you have a need to ship something that needs to be kept warm (not hot!) from/to someplace that also needs to ship something that needs to be kept cold?

Burritos and ice cream :-)

Burritos need to be kept hot, not warm. The warm is great temperature to breed harmful bacteria.

Warm is also great for useful bacteria, like lactobacillus. I keep my ginger bug mother jar in the cabinet above my fridge.

So almost totally OT question here. Last week I was cleaning out some bottles that had held home made ginger ale (I had filled the bottles with water after drinking) and I noticed that one of them had a goopy, SCOBY-like structure floating in it. Was that the ginger bug?

Never made ginger ale from a mother, always used fresh ginger, but I should try it some time.

Drinks and towels for first class?

Live animal + tissue sample? Is that anything?

We barely even harvest heat waste from Nuclear reactors...

It's not going to be economically viable to harvest heat waste from a fridge.

I don’t think the hot side gets hot enough for it to be a particularly useful heat, but it does help heat the space that the fridge is in. The rest of the fridge is cooling the surrounding space though, via whatever heat leaks in through the insulation and particularly whenever you open it.

I’ve sometimes wondered whether somehow having the hot side go outside (like with a heat pump) would make sense during the summer, so it acts as part of the air conditioning.

> I’ve sometimes wondered whether somehow having the hot side go outside (like with a heat pump) would make sense during the summer, so it acts as part of the air conditioning.

It would, but then the house needs to be build around the fridge. No moving the fridge to clean behind it. No trading it in for a different model. When it breaks you have to get a technician out for a few hours labor - there is no option to go to home depot and bring home a new one.

I don’t imagine it being quite that inflexible if it became popular, but a replacement would need to be hooked up to refrigerant lines like a mini-split system. That’s going to be a more expensive install or replacement.

It would be quite inflexible now when it’s custom and there’s no standard for such things.

It would have to be - the size of many of the parts need to be matched, so any change means a lot of changes (either that or the system is less efficient than what we have today). Also refrigerants keep changing as we discover less harmful ones, and often they are incompatible with the old so tear out the old pipes which otherwise should last a lifetime just because they are contaminated (or the wrong size)

Only to warm things up, not to cool them down.

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