A novel portable pneumatic power source using phase transition at the triple point

This study is concerned with the development of a novel portable pneumatic power source applicable to portable applications such as wearable actuator and rescue robot etc. Dry ice is chosen as a source of power for the pneumatic power source because it is non-poisonous, easy to obtain and it expands 750 times in volume after being vaporized into gas. When dry ice is stored in the confined pressure container, it begins to liquefy after the pressure reaches the triple point (0.52MPa (abs), -56.6 degrees C). During this process the pressure remains constant until all dry ice melt into liquid. When the state remains at the triple point, the pressure does not decrease even though the gas is released from pressure container. By using this physical property of carbon dioxide, and by controlling the heat transfer from the surroundings into the pressure container, a noiseless, large capacity and portable pneumatic power source is developed.