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Current fuels cells like in the Mirai have a peak efficiency of around 65% all the way down to around 40% at full power. A lithium battery is nearly 100% effic

Current fuels cells like in the Mirai have a peak efficiency of around 65% all the way down to around 40% at full power. A lithium battery is nearly 100% efficient. They both run through an inverter and electric motor so those efficiencies are the same.

modshatereality 5y ago
100% efficient? their capabilities degrade over time, and they are basically toxic waste when they are to be disposed of.
- SigmundA 5y ago
  Their capacity diminishes not their efficiency and they are 80-90% recyclable. Efficiency is how much power is put in vs how much you get out.
xorcist 5y ago
Well, of course. If you have a battery, then use the battery. Many practical uses keep a complementary battery for extra capacity for this reason. But the use cases are different. A fuel cell is efficient compared to pretty much every other form of generating electricity from energy stored in a fuel that we know of.
- SigmundA 5y ago
  The point is if you have electricity then converting to hydrogen, compressing transporting and turning back into electricity in a fuel cell is much less efficient than just charging a battery. Why would you do that? You could argue energy density, but looking at current fuel cell vehicles like the Mirai shows the have only a slim advantage in range dues to the weight of the fuel cells, high pressure tanks and tractions batteries and extra structure to protect the tanks.
  - xorcist 5y ago
    Energy density is indeed it. Not much to argue about, it carries several times more energy per weight than any battery, and is several times cheaper too. The Mirai is a proof of concept, not a typical use case.
    - SigmundA 5y ago
      When counting storage tanks, fuel cells, buffer batteries and protective structures no hydrogen doesn't really seem to have density advantage. The electrons in the battery are very light and energy dense but the battery to hold them and return them as useful current is not, same for hydrogen. What hydrogen fuel cell car is not a proof of concept?

modshatereality 5y ago

100% efficient? their capabilities degrade over time, and they are basically toxic waste when they are to be disposed of.

SigmundA 5y ago
Their capacity diminishes not their efficiency and they are 80-90% recyclable. Efficiency is how much power is put in vs how much you get out.

xorcist 5y ago

Well, of course. If you have a battery, then use the battery. Many practical uses keep a complementary battery for extra capacity for this reason. But the use cases are different. A fuel cell is efficient compared to pretty much every other form of generating electricity from energy stored in a fuel that we know of.

SigmundA 5y ago
The point is if you have electricity then converting to hydrogen, compressing transporting and turning back into electricity in a fuel cell is much less efficient than just charging a battery. Why would you do that? You could argue energy density, but looking at current fuel cell vehicles like the Mirai shows the have only a slim advantage in range dues to the weight of the fuel cells, high pressure tanks and tractions batteries and extra structure to protect the tanks.
- xorcist 5y ago
  Energy density is indeed it. Not much to argue about, it carries several times more energy per weight than any battery, and is several times cheaper too. The Mirai is a proof of concept, not a typical use case.
  - SigmundA 5y ago
    When counting storage tanks, fuel cells, buffer batteries and protective structures no hydrogen doesn't really seem to have density advantage. The electrons in the battery are very light and energy dense but the battery to hold them and return them as useful current is not, same for hydrogen. What hydrogen fuel cell car is not a proof of concept?