A hot-water supply and heating system includes: a first pump that circulates a first heat medium between a heat source unit and a heat-medium heat exchanger; a second pump that causes a second heat medium to flow between a load-side device and the heat-medium heat exchanger; a first temperature sensor that detects a primary fluid temperature that is a temperature of the first heat medium that flows out of the heat source unit; a heat-source-unit controller; and a pump controller. The heat-source-unit controller transmits information indicating the heating capacity of the heat source unit reaches an upper limit value to the pump controller, when it is determined that the primary fluid temperature is lower than a target temperature and the heating capability of the heat source unit is equal to the upper limit value. The pump controller reduces an operation frequency of the second pump when receiving the above information.

A fluid-based system for use in heating and/or cooling. In particular, the system may have a fluid heating device, which may be a solar fluid heating device, configured to heat a fluid. Heat from the heated fluid may be transferred to one or more cooling subsystems or heating subsystems. A cooling subsystem may be an absorption cooling subsystem, for example, wherein heat may cause phase change of a refrigerant. A heating subsystem may include a storage tank through which heated fluid may be circulated to heat the storage tank. A system of the present disclosure may include multiple cooling and/or heating subsystems for cooling and or heating a variety of different environments, objects, or materials.

A system and method for providing domestic hot water and/or space heating within a building. The system comprises at least one storage vessel comprising a removable cover, wherein an internal volume of the storage vessel is fluidly connected to a source of sewage and/or wastewater from one or more buildings, a water-source heat pump, at least one solar thermal collector, at least one heat transfer circuit. The at least one heat transfer circuit includes at least one fluid line containing a heat transfer fluid, and a controller for controlling an operation of the system. The system has an operation mode in which the controller of the system is configured to connect the at least one solar thermal collector to the at least one storage vessel via the at least one fluid line. The system stores a heat output from the at least one solar thermal collector in sewage and/or wastewater.