Self-contained power source for railcars

A bidirectional power source, comprising:

• an air turbine selectably coupled to an air brake system of a railcar, wherein the air turbine comprises a generator, wherein the air turbine converts mechanical energy received from pressurized air of the air brake system to electrical energy by way of the generator;
• and
• an energy storage system, wherein the energy storage system is electrically coupled to the generator, wherein the bidirectional power source is removably attachable to the railcar.

A method for charging an energy storage system coupled to a railcar, the method comprising:

• causing, by a controller, a pneumatic valve to open when an air pressure of an air brake system of the railcar is at or above a predetermined level, wherein causing the pneumatic valve to open provides pressurized air to an air turbine from at least one of the air brake system or an exhaust pipe of the air brake system of the railcar, wherein the air turbine is coupled to the railcar and comprises a generator that converts mechanical energy from the pressurized air to electrical energy for charging the energy storage system.