reasons not to use high-performance diesels

diesels make more power and with better economy than gas/petrol engines per #/BTU or whatever you want to measure it by.

A petrol can make more power with less capacity thats its only claim to fame and that only works to a certain size 'cylinder' hence we dont have large petrol engines do we

 

Only 4000 HP.

http://en.wikipedia.org/wiki/Pratt_&_Whitney_R-4360_Wasp_Major

 

ok
I should have said certain size cylinder..

 

No. You should have said turbine ....

 

I dont get that?
are you saying a diesel powered turbine is more efficient that a gas piston engine?

 

Turbines run kerosene, JP4. Something like diesel. But, more expensive.

And yes, turbines are efficient, and expensive.

Diesels are usually more efficiently applied to a project. But, turbines, especially combined cycle turbines, can be more efficient.

 

So, if you took one of those fancy DE systems and replaced it with an efficient combined cycle turbine, you could see significant savings.

For our purpose let us imagine a 800 hp equivalent. 90 foot catamaran yacht.

The DE system with a good Diesel can exceed .40% thermal efficiency. And about 94% electric efficiency - more expensive this way.

The Combined Cycle Turbine can achieve 55% efficiency times .94 on the electric.

.52% vs. .38% I think the engine weights would be close to the same. But, I expect the Combined Cycle to be heavier.

The electric can achieve 96%. And the turbine can probably be tweaked to 60%.

Augment with some solar panels, and we start the old argument all over again about cost vs. affordability.

 

My understanding is the efficiency of gas turbines typically drops significantly at part load.

 

and creating electricity to power an electric motor to power a shaft is about 30% less efficient than having that same engine coupled to the shaft