An energy storage device includes a phase-change energy storage tank, a first liquid inlet pipe, a first liquid outlet pipe, a second liquid inlet pipe, a second liquid outlet pipe, and a pipeline. The phase-change energy storage tank includes a first housing and a second housing disposed in the first housing. The second housing includes a liquid inlet, a liquid outlet, a feeding hole, and a discharge hole. The first housing includes a thermal insulation material. The second housing includes a phase change material. The liquid inlet and the liquid outlet are disposed on two ends of the second housing, respectively. The phase change material is introduced to and discharged out of the second housing via the feeding hole and the discharge hole, respectively. The first liquid inlet pipe, the phase-change energy storage tank, and the first liquid outlet pipe are connected sequentially to form an energy storage unit.