Abstract: An energy carrier system is provided that produces ammonia with high efficiency and that further produces hydrogen as final product and uses the hydrogen as energy. An energy storage transportation method is further provided that is carried out by using energy carrier system. The energy carrier system includes nitric acid production device, an ammonia production device, and hydrogen production device. The nitric acid production device includes a photo-reactor, a gas supply unit that supplies photo-reactor with gas to be treated containing a nitrogen oxide, water, and oxygen, and light source disposed in the photo-reactor. The light source radiates light including ultraviolet of a wavelength shorter than 175 nm. The energy storage transportation method includes nitric acid production step of producing nitric acid from a nitrogen oxide, ammonia production step of producing ammonia through reduction of nitric acid, and hydrogen production step of producing hydrogen through decomposition of the ammonia.