• Toto@lemmy.world
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    3 days ago

    Wish they gave the current energy density of lithium batteries for comparison.

    • JohnDClay@sh.itjust.works
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      2 days ago

      Here’s a neat comparison of how different chemistries preform. Higher up is higher energy per weight.

      comparison

      Looks like this is pretty old though

    • eltrain123@lemmy.world
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      3 days ago

      It’s a range, but LFP is generally in the 90-160wh/kg and NMC (lithium manganese cobalt oxide) tops out around 275 wh/kg.

      It’s not quite double, but doubles the density of most mass manufactured cells. Time will tell if it gets to scale, but it’s a step in the right direction.

      • Toto@lemmy.world
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        3 days ago

        Feeling stupid: doesn’t this mean more energy per kilogram is possible with Na cells?

        • deegeese
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          2 days ago

          Isn’t most of the weight with hydrogen coming from the high pressure tank and gas regulator?

          My impression is that the gas is light but whole system hydrogen is pretty heavy.

          edit: Did some more reading. Hydrogen is still competitive on a Wh/kg basis, but worse on a Wh/L basis. Larger tanks are harder to fit in passenger cars than batteries and hydrogen’s poor whole system efficiency has kept fuel prices high while lithium batteries and solar power keep getting cheaper.

          • humanspiral@lemmy.ca
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            2 days ago

            H2 to get weight of tank down and highest density can be liquified. This works best by far for aviation that refuels right before takeoff. Can work for commercial boats as well. Costs more energy to liquify than compress.

            • deegeese
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              2 days ago

              This makes hydrogen even more expensive and pushes it further into niches which need maximum range at any cost.

              • humanspiral@lemmy.ca
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                2 days ago

                Renewable h2 can be cheaper than gasoline or kerosene. Even with liquifaction. Has to use behind the meter or wholesale renewables instead of fixed utility pricing with transmission costs.

                Planes typically spend 100x in fuel over lifetime compared to price of plane

                • deegeese
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                  2 days ago

                  Where are you finding this cheap renewable H2?

                  Or is this a theoretical future development?

                  • humanspiral@lemmy.ca
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                    2 days ago

                    Making h2 at less than $2/kg from renewables is achievable today. 300 bar at $2. Lh2 at $2.50.

                    Sales prices are much higher because capacity is still low, and toyota bundles some free to its fcev customers, and sales volumes are low such that a high profit margin is required to pay for filling infrastructure.

                    $2/kg is equivalent range in a fuel cell compared to 1$/gallon gasoline. That is much less than refinery sales prices of gasoline or diesel.

                    Consumer prices have chicken vs egg problem.

                  • EldritchFeminity@lemmy.blahaj.zone
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                    2 days ago

                    I’m assuming the concept they’re thinking of goes something like: Using renewable energy like solar and wind to convert water (or some other source of H2) into liquid H2 for the increased energy density compared to charging lithium batteries or equivalent with those same renewables.

                    There’d be tons of energy loss along the way, but since renewables are effectively “free energy,” I can see that it would work in theory.