Dear Mr. Ajit,
Nice to note that you are interested in Mechanical Design stuff, I have this Free-piston Stirling machine which is an external combustion engine unlike the petrol diesel & the jet engines which are all internal combustion engines. So, this external engine’s peculiarity is that it would run on the sun’s heat/energy and produce electricity from dawn till dusk FREE.
You could involve yourself in the study & design of such machines as your course work and take it up as a project work. Think about this and let me know.
Stay well
Regards