Thanks Mike
I am going to bear all this in mind next time I get to talk to someone about fuel cells – armed with questions about weight and dynamic properties.

Fuel cell/electric motor pairings are more efficient than turbines, but only at the cost of using huge amounts of precious metals. Also as there is a small lag in fuel cell output, you either have to store that energy in a battery (more lithium) or dissipate it. Thus the cost is higher, and you are having to continually accelerate and brake a lot more weight, which is often the largest use of fuel anyway. In the meantime, a simple hydrogen turbine is very low weight, and heat engines are getting more and more efficent.

Of course as hydrogen is a totally green energy source once production is ramped up, some wastage will be acceptable in either of the above, and then lower system cost will probably dominate.

Morning Mr Bryant
Oh dear, are fuel cells that inefficeint?
Part of the naivety I mentiond to Steve Kurt, was that I assumed that the second law of thermodynamics put heat engines at a disadvantage compared with fuel cells.

Morning Mr Kurt
I was like you, and realised I was fuel-cell-naive after I heard about this research.
Clever stuff.