A building heating/cooling system utilizing pumped secondary fluid, comprising: a heat exchanger having a first thermal energy fluid inlet port and a first thermal energy fluid outlet port; a fluid actuation device assembly including at least one secondary fluid pump set and a fluid actuation device, the fluid actuation device being configured to be driven to rotate by a pressurized thermal energy fluid and said at least one secondary fluid pump set being configured to be driven to rotate by said fluid actuation device, characterized in that an outlet of said fluid actuation device assembly is connected to the first thermal energy fluid inlet port of the heat exchanger; and a secondary fluid flowpath structure including at least one flow guide plate for guiding said secondary fluid from an interior of a building through the fluid actuation device, through the heat exchanger and back towards the interior of the building, wherein said components are configured to be installed in the building, and the building is a closed type or semi-open building, wherein said pressurized thermal energy fluid is supplied to said fluid actuation device assembly from an external source, passes through the fluid actuation device, passes through said heat exchanger to exchange thermal energy with said secondary fluid, and then is output to an exterior location, and wherein said secondary fluid is pumped by the at least one secondary fluid pump set configured to be driven by said pressurized thermal energy fluid to flow past the heat exchanger and exchange thermal energy with the pressurized thermal energy fluid in the heat exchanger, and then enters a temperature differentiation body space in the interior of the building, wherein a part of the secondary fluid returns as reflux to a secondary fluid inlet port of the building, then again being pumped by the secondary fluid pump set thereby forming a reflux circulation of secondary fluid. a heat exchanger having a first thermal energy fluid inlet port and a first thermal energy fluid outlet port; a fluid actuation device assembly including at least one secondary fluid pump set and a fluid actuation device, the fluid actuation device being configured to be driven to rotate by a pressurized thermal energy fluid and said at least one secondary fluid pump set being configured to be driven to rotate by said fluid actuation device, characterized in that an outlet of said fluid actuation device assembly is connected to the first thermal energy fluid inlet port of the heat exchanger; and a secondary fluid flowpath structure including at least one flow guide plate for guiding said secondary fluid from an interior of a building through the fluid actuation device, through the heat exchanger and back towards the interior of the building, wherein said components are configured to be installed in the building, and the building is a closed type or semi-open building, wherein said pressurized thermal energy fluid is supplied to said fluid actuation device assembly from an external source, passes through the fluid actuation device, passes through said heat exchanger to exchange thermal energy with said secondary fluid, and then is output to an exterior location, and wherein said secondary fluid is pumped by the at least one secondary fluid pump set configured to be driven by said pressurized thermal energy fluid to flow past the heat exchanger and exchange thermal energy with the pressurized thermal energy fluid in the heat exchanger, and then enters a temperature differentiation body space in the interior of the building, wherein a part of the secondary fluid returns as reflux to a secondary fluid inlet port of the building, then again being pumped by the secondary fluid pump set thereby forming a reflux circulation of secondary fluid.