Nice to see Ricardo Engineers mentioned here. Sir Harry's company is one of the leading development sources for thermo-machinery and now-a-days energy use. Recommend his autobiography.
First some background:
A long time ago my graduate paper in electrical engineering was on hybrid propulsion... long long before it became popular. The idea proposed was a directly coupled turbine and permeant magnate brushless alternator / flywheel assembly producing wild voltage and frequency power which was converted electronically and powered PM motors. The turbine was operated in a pulse mode (pulse turbine) with PWM fuel control which could be turned off or on as power demand required. The motors on the load could act as generators for regeneration such as braking in a land vehicle. Basically feeding power back to the power plant which could be stored in a flywheel in combination with the rotating mass of the turbine wheel and generator.
The PWM fuel control was developed by my very good friend and mentor Warren Boardman at Marquardt Corp in 1957 for use in pulse rockets.
Warren invented pulse rockets, Pulse width modified fuel control, spy satellites, multiple reentry technology then known by the acronym, PAT-C, PAT-C standing for position, attitude and trajectory control also, fortuitously matched President Roy Marquardt’s wife’s name, Patsy. Warren and Marquardt pioneered many other important technologies... actually have a video of running a small diesel engine on a pulse rocket injection system as a test bed back in 1957... the fundamental of modern modern pulse width modulation PWM electronic control fuel injection. Warren by the way never got much credit as much was classified. The bigger project was developing the digital electronic control in the analog age... although transistors had been developed by Bell labs in the early 1950's by John Bardeen and Walter Brattain using germanium doped crystals... applications only developed slowly. It took about 200 engineers to do the engineering development of the pulse rocket... after Warren's Advanced Development group proved the concept.
It was PWM control ideal applied to the situation as it could minimize chemical energy consumption and control such to very fine limits... actually without it Apollo would not have been possible (Warren did the initial flight profile concept and convinced the newly formed NASA of it which resulted in the success you know so well... very interesting story as is the spy satellite or "Mount Palomar in the Sky"). Interestingly, the smallest rockets controlled the program literally and figuratively... not the big main engines. Actually, many of the diesel and spark ignited electronic fuel controls now-a-days are based on this fundamental technology. It has become universal in efficiency of any streaming but incrementally variable process control... where fine control is necessary.
Unfortunately, the motor technology when I did my studies was not quite there. We had sumarium cobalt magnets and built motors with them. This had been used in some satellite and missiles of various types. However, the problem was usually heat transfer out of the stator. Much later in the late 1980's and early 1990's Joe Denk at Allied Signal invented his toothless motor technology which solved the problems of increasing magnetic density of the machine and cooling it. But I had moved on.
However, I think an energy system like this would be very applicable now-a-days in land based vehicles and any start and stop operation. But for boats I don't know. Generator systems typically produce to relatively stable power loads... and the propulsion systems the same. As pointed out before its not a start and stop situation... just one big constant energy draw... .
However, the idea of combining the flywheel somehow with the energy production of the yacht as a means of roll stabilization does have much merit. These functions could be combined with the somewhat variable load needed for electrical supply. Actually and interestingly, roll control and space attitude control are similar where a limit cycle and energy input minimization situation are paramount. Here is a demo of gyroscopic roll stabilization on the Wally Ace... towards the last 1/3 of the video. WallyAce 26m from Motor Boat & Yachting - YouTube
But the idea of PMW control does provide the improvements in fuel consumption of the diesel and spark ignited engines with electronic injection now so universal the industry.