For a heat pump dumping heat a couple C above ambient (typical of heat pumps which is why people coming from furnaces complain that the air coming out isnt hot) that’s
n = 1 - 298/300 = 1-0.9933 = 0.67%
That means you’d need a machine that is more than 99.33% efficient to get any work out of that heat difference. For comparison, an engine losses 15-30% of energy just from the friction of polished metal cylinders and cams gliding close to another polished metal wall with a layer of oil in-between. The metal isn’t even touching.
Actionlab just did a video on Carnot a few days ago.
So couldn’t we use a heat pump on the few degree above ambient waste heat to then do real work with it?
Carnot is 1 - T(coldside)/T(hotside) in Kelvin.
For a heat pump dumping heat a couple C above ambient (typical of heat pumps which is why people coming from furnaces complain that the air coming out isnt hot) that’s n = 1 - 298/300 = 1-0.9933 = 0.67%
That means you’d need a machine that is more than 99.33% efficient to get any work out of that heat difference. For comparison, an engine losses 15-30% of energy just from the friction of polished metal cylinders and cams gliding close to another polished metal wall with a layer of oil in-between. The metal isn’t even touching.
Actionlab just did a video on Carnot a few days ago.
https://youtu.be/lGbrQJO3E_4