3 ms·

Great graph. The proposed tech is aiming to replace non critical part which is already 90% efficient, but takes extra volume in the car.

by tener 5y ago

upofadown 5y ago
Compression/liquefaction doesn't really have an efficiency. It is just a dead loss of energy. So you really need to know the assumptions to know what the 90%/65% is of. I suspect it is the same for the other percentages thrown around on that diagram. ... and why doesn't the H2 vehicle do regenerative braking?
- shaded-enmity 5y ago
  Probably because you'd need a battery to store the energy generated via braking thus eliminating much of the environmental benefit.
- SigmundA 5y ago
  Any loss means efficiency below 100%. If it takes 1kwh of electricity to compress 10 kWh of hydrogen (assuming 100% conversion back into electricity in the fuel cell, which its not) then your efficiency is 90%. This is applied to all steps, electrolysis, compression, transport, and fuel cell conversion back to electricity. Current fuel cells cannot put out enough burst power to acceleration nor can they accept electricity in reverse to generate hydrogen so all current fuel cell vehicles use a traction battery that is charged by the fuel cell, they are basically series hybrids. They also typically have lower acceleration because the small traction battery + fuel cell cannot supply as much power as a much larger full EV battery.
- tener 5y ago
  Regenerative braking works for electric cars because it is super easy to convert movement into electric energy. This isn't true for most other sources of energy H2 and petrol included. Reversing combustion is kind of hard and takes up big chunk of the linked graph.
  - Gibbon1 5y ago
    Fuel cells are crappy in that the reaction isn't reversible. Where Batteries and electric motors are nearly fully reversible. And fuel cells are only efficient when compared to heat engines. But subpar when compared to batteries.

Great graph. The proposed tech is aiming to replace non critical part which is already 90% efficient, but takes extra volume in the car.

by tener 5y ago

Great graph. The proposed tech is aiming to replace non critical part which is already 90% efficient, but takes extra volume in the car.

upofadown 5y ago

Compression/liquefaction doesn't really have an efficiency. It is just a dead loss of energy. So you really need to know the assumptions to know what the 90%/65% is of. I suspect it is the same for the other percentages thrown around on that diagram. ... and why doesn't the H2 vehicle do regenerative braking?

shaded-enmity 5y ago
Probably because you'd need a battery to store the energy generated via braking thus eliminating much of the environmental benefit.
SigmundA 5y ago
Any loss means efficiency below 100%. If it takes 1kwh of electricity to compress 10 kWh of hydrogen (assuming 100% conversion back into electricity in the fuel cell, which its not) then your efficiency is 90%. This is applied to all steps, electrolysis, compression, transport, and fuel cell conversion back to electricity. Current fuel cells cannot put out enough burst power to acceleration nor can they accept electricity in reverse to generate hydrogen so all current fuel cell vehicles use a traction battery that is charged by the fuel cell, they are basically series hybrids. They also typically have lower acceleration because the small traction battery + fuel cell cannot supply as much power as a much larger full EV battery.
tener 5y ago
Regenerative braking works for electric cars because it is super easy to convert movement into electric energy. This isn't true for most other sources of energy H2 and petrol included. Reversing combustion is kind of hard and takes up big chunk of the linked graph.
- Gibbon1 5y ago
  Fuel cells are crappy in that the reaction isn't reversible. Where Batteries and electric motors are nearly fully reversible. And fuel cells are only efficient when compared to heat engines. But subpar when compared to batteries.