You're right Harry it's more rigorous to define the COP as the ratio of output power to input power. Note that for heat pumps it is often used even more rigorously to describe the ratio of output (moved) thermal power to input mechanical power, i.e. taking the motor or engine's efficiency out of the equation.
IMHO one can use both definitions provided one defines clearly the _system_ under study (heat pump alone, or motor+ heat pump combination, commercially called "heat pump") Michel ----- Original Message ----- From: "Harry Veeder" <[EMAIL PROTECTED]> To: <vortex-l@eskimo.com> Sent: Friday, March 09, 2007 7:16 PM Subject: Re: [Vo]: Proof of capturing ambient temperature energy > Michel Jullian wrote: > > >>> >>> COP is the ratio of output power to input power. >>> >>> Harry >> >> Same thing actually: Eout/Ein = Pout*t / Pin*t = Pout/Pin >> Jed's COP=1.2 example was given in terms of energy (1200 joules out / 1000 >> joules in), my COP=4 example was in terms of power (1000 watts out / 250 >> watts >> in). >> >> Michel >> > > The practical significance of the two ratios is very different. > Eout/Ein says nothing about the rate at which energy needs to be > supplied to the system to maintain the ratio. > > e.g. 1000 joules in per second and 1200 joules out per minute > is not the same as 1000 watts in and 1200 watts out. > > Harry >