An energy-saving system adapted a plant factory including a heat exchanger, a first supply device, a second supply device, a power generating unit, and a cultivation area. The first supply device provides a heat exchange medium to the heat exchanger. The second supply device provides a liquid carbon dioxide to the heat exchanger. The liquid carbon dioxide flowing through a heat exchanger is converted to a gaseous carbon dioxide. The power generating unit is connected to the heat exchanger, which includes a turbine and a generator. A kinetic energy is produced to the generator by using the gaseous carbon dioxide to drive the turbine, so as to produce an electrical energy by the generator. The cultivation area is connected to the power generation unit. The gaseous carbon dioxide through the power generation unit is transported to the cultivation area in order to supply plants in the cultivation area for photosynthesis.一種用於植物工廠的節能系統包括:熱交換器、第一供給裝置、第二供給裝置、發電單元以及栽培區。第一供給裝置提供熱交換介質至熱交換器中。第二供給裝置提供液態二氧化碳至熱交換器中。液態二氧化碳流經熱交換器後轉變為氣態二氧化碳。發電單元連接至熱交換器,其包括渦輪機與發電機。所述氣態二氧化碳驅動渦輪機產生動能至發電機,進而產生電能。栽培區連接至發電單元。經由發電單元後的氣態二氧化碳被運送至栽培區中,以供應栽培區中的植物進行光合作用。10、20、30、40、50、60‧‧‧管路10a、20a‧‧‧入口10b、20b‧‧‧出口100‧‧‧節能系統102‧‧‧控制單元104‧‧‧第一供給裝置106‧‧‧第二供給裝置108‧‧‧熱交換器110‧‧‧發電單元112‧‧‧空調單元114‧‧‧電熱裝置116‧‧‧儲熱裝置118‧‧‧栽培區120‧‧‧警示單元
