# Convert heat from heat pump into energy

I've learned that a heat pump transfers the energy from the hot side to the cold side.

Instead of transferring heat to the cold side, is it possible to convert it into electrical power, as with a steam turbine? Could an air conditioner produce power instead of releasing hot air?

My guess is that the energy transferred is much less than the energy needed to compress the gas that transfers the heat.

• "Could an air conditioner produce power instead of releasing hot air?" Don't you mean a heat pump? Commented Jun 27, 2019 at 15:40

Could an air conditioner produce power instead of releasing hot air?

I’m going to assume you meant heat pump and not air conditioner since hat is the title of your question.

In theory you could use a heat pump to operate a heat engine that produces electricity. But the very best you can do is to connect a Carnot heat pump to a Carnot heat engine. Because the Carnot heat pump and heat engine are the most efficient possible.

Let's say the Carnot heat pump uses electrical energy to move heat from a low temperature reservoir to a high temperature reservoir. This heat is then taken from the high temperature reservoir as the input to a Carnot heat engine, produces electrical energy as its output while rejecting heat to the lower temperature reservoir. That heat can then be the heat input to the heat pump and so on. The electrical energy output of the heat engine will equal the electrical energy input to the heat pump. The net electrical power produced will be zero.

My guess is that the energy transferred is much less than the energy needed to compress the gas that transfers the heat.

If I understand what you are saying correctly, your guess is correct. The scenario described above involves the most efficient heat pump and heat engine possible, and results in a "break even" regarding the electrical energy needed and the electrical energy produced. In reality this possibility doesn’t exist as it would constitute a perpetual motion machine (continual circulation of heat). For all real heat pumps and heat engines, you will need more electrical energy to operate the heat pump than you can produce with the heat engine.

Hope this helps.

• Doesn't the operating principle of an air-conditioner the same as a heat-pump? Commented Jun 28, 2019 at 7:29
• Yes but the goals are different. The goal of the AC is to remove heat from a low temperature environment while the goal of the HP is to add heat to the high temperature temperature environment. I interpreted your question as using the heat delivered by the HP to operate a heat engine to produce electrical power. So it just made more sense, for me anyway, to refer to the HP instead of the AC. You can say either one, but your title said HP. Should be consistent Commented Jun 28, 2019 at 9:01
• I should add that the design of actual ACs and HPs are somewhat different in order to achieve rhe different goals. You can’t just take a window AC and turn it around and have an optimal HP Commented Jun 28, 2019 at 9:10