this post was submitted on 25 Sep 2024
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What are these “heat pumps” ? Is that like a heater or an AC?
It's a reverse-cycle AC if you've heard the term. Basically, an AC that can can run in reverse, heating the room.
It's the most efficient form of heating and cooling that we have, since it doesn't create energy, but instead moves it (so its efficiency is greater than 100%).
It takes less energy to move heat than it does to produce it. A heat pump basically runs an air conditioner backwards, so rather than moving heat from inside a structure to outside, it moves heat from outside to in. With the right units, this works even in cold weather for the same reason a freezer gets warm on the outside - it's moving heat from inside the (freezing) unit out.
Geothermal energy takes this concept a step further by putting the outside unit underground. Underground temperatures are more stable and moderate, so it's easier (more efficient) to expel/collect heat, but also much more involved to install.
It's what different parts of the world call a reverse cycle, split system air conditioner.
On individual scale, precisely that - a split type AC with one half indoors (or in a water tank) and the other half in an outdoor environement (air, water or ground).
If you're extracting heat from the environment, the machine lets the working fluid evaporate into the outdoor heat exchanger and compresses it back into the indoor heat exchanger. If you're cooling your premises - reverse that.
However, on a city scale, it's like "you've got a lot of sewage at 30 C" -> "your heat pump is a large building" -> "your sewage outflow is now at 10 C, but your underground heat reservoir gets charged to 140 C (stays liquid because of water column pressure), and you spend much less energy pumping the heat than you would spend heating the water directly".
Air conditioners are exactly a heat pump. As are refrigerators. The only difference is that it's turned around so the hot side is inside.
The typical heat pump setup (in the US) is not reversible. That means you would also have the AC heat pump next to it, capable of moving heat in the other direction.