> a tank of compressed air is lighter than batteries
Joule for joule, it's not. The best compressed air tanks you'll find roughly reach lead/acid batteries in energy/weight (~100kJ/kg). Lithium-Ion batteries have 4 to 9 times the energy density.
Indeed. Also the mechanism to capture compressed air when braking would be in addition to the electric motor, which is needed in any event, and can charge batteries when braking. So yeah, upon reflection, just a Bad Idea.
Joule for joule, it's not. The best compressed air tanks you'll find roughly reach lead/acid batteries in energy/weight (~100kJ/kg). Lithium-Ion batteries have 4 to 9 times the energy density.