Systems, methods, and apparatuses are directed to monitoring a capacity at which an engine is operating, the engine comprising a turbocharger. It can be determined whether the engine is operating above a threshold capacity. If the engine is operating above a threshold capacity, a closed-loop thermal cycle working fluid can be heated with heated air from the turbocharger. If the engine is operating at or below a threshold capacity, the working fluid can be heated with exhaust from the engine. The heated working fluid can be directed to a turbine generator, which can generate electrical power.