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Better Overall Performance from Turbocharged Systems:
During cruise and under modest load, turbocharged systems are wasting power through exhaust restriction with only nominal gains in overall performance. Likewise with onboard electrical generation systems, the mechanical charging subsystem is wasting power by continuous rotation without any gain after electrical storage subsystem is fully charged (alternator, belt and pully subsystem).
The cool side output shaft (compressor side) of most modern turbocharged systems has enough surplus rotary power to drive the electrical charging subsystem (alternator). Since modern internal combustion engines use belts and pullies to drive the electrical charging subsystems, overall:
The net power output would be enhanced by driving the alternator (electrical power charging subsystem) from the compressor output shaft of the turbocharger.
This would also apply to the combustion engine systems under maximum load (maximum acceleration in the case of race cars) as it is generally accepted that the belt and pully driven alternators drag as much as 30 horsepower from a combustion engine, even when the batteries are charged. The inefficiencies of the belts and pullies are eliminated. The inefficiencies of the modestly loaded turbocharged system are improved in the overall net power generated.
Additional features / advantages:
Savings in parts count and manufacturing costs (lower bearing count, eliminated belts and pullies, etc.).
Reduction in size and weight of the overall system and
if coupled with "one wire" alternator subsystems, further savings may be realized.
Alternator may be cooled via airflow in the induction system.
Gains in reliability through reduced lateral loading of alternator bearings.
Engineering considerations:
A redesigning of the alternator for much higher RPM of the turbocharger ... possibly using a simple rotating magnet close to the centerline of rotation with fixed pickup coils (ala magneto).
Any modest reduction in performance of the turbocharger through reduced airflow boost during heavy loading (maximum acceleration) might be offset by maintaining RPM for the next demand cycle (flywheel effect of the more massive rotating turbocharger parts with added alternator rotor).