ECO kettle - I don't get it

stanstedpete

More like 99.99% - where else is the energy going to go?

danmc_82

No where near 99.99%, look it up.

Energy is used up as sound and light.

EarthRod

There seems to be some confusion regarding AC power dissipated in an inductive load such as an electric heater.

There are several different equations relating to types of power, ie resistance, impedance and reactive. Under a resistive/reactive load (for example an electric heater) the power is a function of the circuit's total impedance (Z) and not just it's resistance (R).

So, total power in an AC circuit, such as an electric heater, both dissipated as heat and absorbed by impedance is measured in VA (Volt/Amps) and not Watts.

Only power dissipated is measured in Watts, but that does not take into account the phase angle created by an inductive load.

That is why there is no such thing as 100% efficiency, not even close - in fact nowhere near! There are other losses to take into account.

Sorry for the technical crap - but things are not as simple as they seem.

danmc_82

^^^^ Finally someone who agrees My explanation was a bit more simple

stanstedpete

My electric heater doesn't make any sound.

Light and heat are the same thing - simply different frequencies.

stanstedpete

Let's keep it simple - we're not all physicists. If the energy put in doesn't come out as heat, in what form does it come out, and where does it go?

stanstedpete

Of course, it all depends where you draw the boundaries:

Energy conversion efficiency of electric heaters is 95%? Shouldn't it be a 100%?

danmc_82

I rest my case

stanstedpete

You were right when you said that an electric kettle isn't 100% efficient, because not all of the heat generated fulfils the intended purpose of boiling the water - energy is lost to the environment through radiation, convection, as steam and as sound.

In the case of a space heater the intended purpose IS to heat the environment - therefore the efficiency of the heater is virtually 100%. Even though some of the electricity used heats the heater itself, this stored heat is released to the environment when the electricity is switched off (in a system where the electricity is never switched off it becomes an infinitely small percentage).

Whilst an ordinary space heater can never output as heat more than 100% of the energy input in the form of electricity, a heat pump can - in a well-designed system the heat output can be 3 to 4 times the electricity input and the theoretical limit is even higher.

The real question, given the subject of this thread, is whether it would be possible to make a highly-efficient kettle (or equivalent) using heat pump technology?

danmc_82

That doesnt make sense, how can a heat pump produce more heat than electricity going in? You either have one or the other.

And even if it did, it doesnt make the unit 100% effecient. How much sound is produced?

Regarding the space heater, what about electrical current producing magnetic waves as it travels down the copper wire, and you say theres no sound, there always is with electrical and mechanical devices. Even if its not audio-able to you.