Tea drinkers:

Most people use water kettles, either stovetop or electric. Some of us use realtime hot water dispensors, which are sometimes a function of coffee machines but in some rare cases they are dedicated stand-alone units.

Pros and cons to each:

stovetop water kettle on ⌁electric stove:
— slow to boil and brew
— wasteful/lossy, esp. if not induction (fuel→heat energy→steam→turbine→AC power→grid transmission→conversion back to heat energy)
— no temp control (green tea drinkers must wait for water to drop to 80°C)
+ BifL: never breaks down and generally outlives you

stovetop water kettle on 🔥gas stove:
— slow to boil and brew
+ energy efficient (fuel→transmission→heat energy); more heat loss on the stove than with electric, but still much less loss than all the electric stages
— …but all city gas pipelines are inherently leaky and unburnt gas is 25× worse for climate than CO₂ (OTOH, this leakage happens wheter you consume gas or not)
— no temp control (green tea drinkers must wait for water to drop to 80°C)
+ BifL: never breaks down and generally outlives you

⌁electric water kettle:
+ fast to boil (1m 20s to boil 25cl in my kitchen)
— …but slow to brew (brewing cannot start until all water is boiled)
— wasteful/lossy (same chain of energy losses as stovetop electric but less waste between the wall and the water)
± /some/ kettles have temp ”control”, but you have to watch it. Some exceptional units can be set to shutoff at 80°C.
+ BifL: never breaks down?

hot water dispensor (⌁electric):
— slow to boil (1m 50s according to YT video X2VdGK2t5vo)
+ …but overall faster to brew because the infusion begins instantly, and this is what matters. So what if it takes 30s longer for hot water if brewing is 1m 20s ahead of the kettle method?
— wasteful/lossy (same chain of energy losses as stovetop electric but has the least energy waste between the wall and the water as the water passes through a small heated pipe; OTOH some energy is used on the pump)
+ all appliances have true temp control, so green tea can be instantly infused with 80°C water automatically and without excessive heat
— non-BifL; it breaks! The usual electro appliance shitshow: complex design; no service manuals; no wiring diagrams; undocumented commands; booby-trapped; spring-loaded… self-destructs when disassembled; spare parts cost more than a new unit [if you can find them] because they bundle several parts together instead of selling individual components… the market seems to have abandoned the dedicated (water only) hot water dispensors

My question: after boiling water in an electric water kettle, I poured it into a glass with a meat thermometer, which went up to ~88°C. Where did the other 12 degrees go? Is it normal for water to fall so rapidly in temp, or is my thermometer dodgy?

  • Zwiebel@feddit.orgEnglish
    2·
    2 months ago

    Here: https://archive.is/bpbp6
    Theoretical Energy for 1l is 100Wh, so the kettle is within margin of error of 100% efficiency in this study. 100/350≈0.29 so 29% efficiency for the gas stove
    Yes this is from the wall.

    Losses in electricity transmission seem to be ~2-10% in the EU: 1000089007

    Now calculation the loss of the electricity generation of the energy mix sounds like a pain in the butt, so I’m just gonna take only gas power plants:

    Gas power plants vary from 30-60%: https://www.pcienergysolutions.com/2023/04/17/power-plant-efficiency-coal-natural-gas-nuclear-and-more/

    So I get a worst case for the electric kettle of 27%, assuming an old gas power plant at 30% and 10% transmission loss to your home.
    And a best case of 59% with a new gas plant and 2% transmission loss.
    But since the other power generation methods also lie on the lower end I’d take the worst case

    Gas loss (here called UFG) is 0.5% in the EU and 1.8% in the US. That gives us a worst case of 28% for the gas stove

    I have to retract what I said initially, this seems a lot closer efficiency whise.
    For the greenhouse gas emissions, the electric kettle should pull ahead in the future as renewables take over

    • plantteacher@mander.xyzOPEnglish
      2·
      2 months ago

      I appreciate the research and references.

      For the greenhouse gas emissions, the electric kettle should pull ahead in the future as renewables take over

      Perhaps in most regions outside of populist-rightwing-controlled regions, that will be the case. ATM I am not in the US but still they are tearing down the nuclear power plants and building 3 new natural gas fired plants. So progress is moving backwards where I am.

      Centralised gas burning would be more efficient than burning it on a domestic stove, but hard to grasp that the difference would be enough to exceed conversion and transmission losses. Worth noting that there are a couple ways to get hot water from gas:

      • simple pot on stovetop
      • water runs through a coil of fire-heated pipe inside an insulated box – aka a tankless combi boiler

      The 2nd option would not give boiling water, as I would not want boiling water to run through the domestic pipework, but I wonder how a small tankless gas-fired tea water appliance might do as far as increasing the gas efficiency, should it be invented.

      In any case, if electric-fueled heat were generally efficient, I would expect the gas-fired combi boilers to be much less popular. Though note as well that economy is not closely tied to efficiency. Natural gas cost per kWh is much cheaper in my area than electric cost per kWh (by a factor of 2 I think).