I wonder if anyone's experimented with using rockets to charge something like a flywheel battery or reservoir for hydro power. A 777's engine puts out tens of megawatts using a less refined fuel than rockets use. What if you hooked a rocket full of RP-1 to a pump to haul water from a river to a dam? This is probably nonsense.
A 777 engine is actually far more fuel efficient than a rocket engine. Take a look at specific impulse [0] for different engine types. A rocket is optimised to be very light and to use its own oxygen supply. A normal jet engine can be heavier and use the air as an oxidizer. Much more efficient for power production in a CCGT.
Rocket engines are actually very efficient, especially in vacuum. Very high expansion ratios can be achieved that converts almost all the heat into jet kinetic energy.
