How does its energy density compare to existing liquid fuels? Diesel engines have a thermodynamic efficiency of ~42% in optimal conditions - usually it's less.

How does its energy density compare to existing liquid fuels? Diesel engines have a thermodynamic efficiency of ~42% in optimal conditions - usually it's less. Large marine units approach 50%, but the fuel they use is only technically liquid. EDIT: I just noticed you were asking about density, not efficiency. I suspect it's much less than liquid fuels, which derive most of their energy from burning the hydrogen in them.