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> My understanding is that a device that converts heat into power would violate thermodynamics. isn't a coal burning steam engine converting heat into power? p
by jjtheblunt 3y ago
> My understanding is that a device that converts heat into power would violate thermodynamics.
isn't a coal burning steam engine converting heat into power?
perhaps the violation applies if requiring efficiency in the conversion?
- Qwertious 3y agoSteam engines operate off the temperature gradient - the water (cool stuff) is turned into steam (hot stuff), which expands 16x and creates a huge pressure spike that pushes the piston/turbine.
- urban_winter 3y ago> steam (hot stuff), which expands 16x 1600 times. Gas at room temp occupies 24 dm3/mole.
- semi-extrinsic 3y agoLet's be precise. When we say "convert heat to power", what we mean is actually "if we have some energy flowing from a heat source to a heat sink, we can extract a percentage of that energy as useful work, like turning a steam turbine to produce electricity". Carnot proved in 1824 that the maximum theoretical efficiency is purely a function of the hot and cold temperature (in Kelvin): Eff = (T_hot - T_cold)/T_hot So for instance a thermoelectric generator operating between 25 °C and 5 °C has a maximum efficiency of Eff = (298 - 278) / 298 = 6.7%
- someplaceguy 3y ago> So for instance a thermoelectric generator operating between 25 °C and 5 °C has a maximum efficiency of > Eff = (298 - 278) / 298 = 6.7% Does that mean a thermoelectric generator operating at a minimum of 0K has a maximum efficiency of Eff = (N - 0) / N = 100%?
- 11101010001100 3y agoOr just (2*N-N)/N.
- someplaceguy 3y agoAccording to the formula you'd have to divide by 2*N.
- 11101010001100 3y agomy mistake!
- tullianus 3y agoYes, although in practice you will have issues sinking heat at 0K without using additional energy to do so, since that's below the radiation sink temperature of space (~2.73K).