A powertrain system comprises a compressed air supply apparatus, a compressed air engine, a rotary power conversion apparatus and an electrical power conversion apparatus. The compressed air engine is configured for extracting energy from compressed air. The compressed air engine receives compressed air from the compressed air supply apparatus and produces rotary power through extraction of energy from the compressed air. The rotary power conversion apparatus is connected to the compressed air engine and is configured for converting the rotary power of the compressed air engine to electrical power of a first specification. The electrical power conversion apparatus is connected to the rotary power conversion apparatus and is configured for converting the first specification electrical power to electrical power of a second specification different than the first specification.