4 ms·

I'm surprised they even got it to boil. I would have expected the heat to escape faster than it's added before reaching the boiling point. That aside, 60 W * 36

I'm surprised they even got it to boil. I would have expected the heat to escape faster than it's added before reaching the boiling point. That aside, 60 W * 3600 s = 216 kJ. With ideal thermal insulation, that would be enough to boil about 600 ml of water. If they only managed to boil enough for a single cup (~300 ml), that's a rather inefficient setup they're using.

pitaj 5y ago
Yeah I'd suspect slowly charging up a battery with the bike generator and then quickly discharging the battery to boil the water would be quite a bit more efficient.
- dylan604 5y ago
  If it takes an hour to charge the battery or an hour to boil the water, it still takes an hour. Based on the previous comment of generating 60W, how much battery charging will that do? I'm really asking as I don't have the info at hand to do the maths. I'm assuming choice of battery comes into play.
  - foxyv 5y ago
    I think that what they are saying is, if we remove the heat losses from the 1 hour boiling time and instead boil it in a burst of 5 minutes using a battery you would need significantly less energy overall. As a result, using a battery instead of directly utilizing the bicycle's electricity, would take significantly less time.
- KennyBlanken 5y ago
  Internal resistance of the battery would be a significant problem, you'd need a fairly sizeable battery, and most lithium ion cells have a maximum discharge rate of around 1-5C unless they're high-discharge-rate cells which are usually more expensive and lower capacity. Using a vacuum flask would dramatically lower heat loss.
  - dahfizz 5y ago
    The kettle used was vacuum insulated.
  - mardifoufs 5y ago
    Some cheap lipo cells can get you a sweet 60-120C discharge rate with a pretty okay capacity. They are also widely available on the used market, usually sourced from EV batteries or energy storage packs. But yes, for the typical 18650/cylindrical li-ion battery, this wouldn't be especially feasible at all

pitaj 5y ago

Yeah I'd suspect slowly charging up a battery with the bike generator and then quickly discharging the battery to boil the water would be quite a bit more efficient.

dylan604 5y ago
If it takes an hour to charge the battery or an hour to boil the water, it still takes an hour. Based on the previous comment of generating 60W, how much battery charging will that do? I'm really asking as I don't have the info at hand to do the maths. I'm assuming choice of battery comes into play.
- foxyv 5y ago
  I think that what they are saying is, if we remove the heat losses from the 1 hour boiling time and instead boil it in a burst of 5 minutes using a battery you would need significantly less energy overall. As a result, using a battery instead of directly utilizing the bicycle's electricity, would take significantly less time.
KennyBlanken 5y ago
Internal resistance of the battery would be a significant problem, you'd need a fairly sizeable battery, and most lithium ion cells have a maximum discharge rate of around 1-5C unless they're high-discharge-rate cells which are usually more expensive and lower capacity. Using a vacuum flask would dramatically lower heat loss.
- dahfizz 5y ago
  The kettle used was vacuum insulated.
- mardifoufs 5y ago
  Some cheap lipo cells can get you a sweet 60-120C discharge rate with a pretty okay capacity. They are also widely available on the used market, usually sourced from EV batteries or energy storage packs. But yes, for the typical 18650/cylindrical li-ion battery, this wouldn't be especially feasible at all