If a machine is never 100% efficient transforming energy into work because part of the energy is converted into heat, does it mean an electric heater is 100% efficient? @showerthoughts@lemmy.world

  • Admiral Patrick@dubvee.orgEnglish
    595·
    9 months ago

    Technically, yes. Even the internal resistances outside of the heating elements eventually radiate into the space. Since the purpose is space heating, it’s not a waste product and they can be roughly considered 100% efficient.

    The reason heat pumps are more efficient (i.e. around 300% or more) is not that they create more heat from the same amount of energy but because they concentrate and move existing heat from one source to another.

    • LastYearsPumpkin@feddit.chEnglish
      183·
      9 months ago

      This is correct, but it’s also, it’s only 100% of the heat at that point in the circuit.

      Technically, using natural gas to make electricity, then sending that electricity to an electric heater would be less efficient than burning that natural gas for heat at the source.

      So it depends on where you start counting from.

      • Admiral Patrick@dubvee.orgEnglish
        14·
        9 months ago

        True, and also the transmission losses between the power plant and your outlets are also factors. I just treated the question like a high school physics one where you’re allowed to disregard air resistance. lol

      • Admiral Patrick@dubvee.orgEnglish
        11·
        9 months ago

        I’m honestly not clear if the visible portion eventually turns to heat or not (in a reasonable timeframe anyway), but the bulk of those emissions are in the infrared spectrum which you will feel as heat or will be absorbed by other objects which will radiate the heat through convection.

        That’s why I said “technically” and “roughly” in regards to 100% efficiency. I’m answering a shower thought in an ELI5 kind of way, not writing a thesis.