Technology Type

A hot water network is a thermal energy distribution system that circulates pressurized hot water (typically 50-80°C) through insulated supply and return pipelines to deliver heat from central generation points to multiple end users, with circulation pumps maintaining flow and heat exchangers transferring energy at consumption points.

Key Components

• Hot water generation units (boilers, heat exchangers)
• Supply and return pipelines
• Circulation pumps
• Expansion vessels
• Heat substations
• Control valves and sensors
• Heat meters

Operating Characteristics

• Closed-loop circulation system
• Temperature difference between supply and return
• Pressure maintenance for system stability
• Variable flow rates based on demand
• Heat transfer through substations to end users

The system provides efficient heat distribution for district heating, commercial buildings, and industrial processes while maintaining consistent temperature control and allowing for heat recovery.

The exemple presented in the illustration is the district heating system in St. Paul. Hot water is generated at the central plant as well as satellite facilities, then circulated through underground pipes to buildings connected to the hot water system. Customers use the hot water to heat interior spaces, heat domestic hot water, melt snow on pavement, and for industrial processes. Once a customer building draws the energy it needs, the water is returned to the central plant for reheating then recirculated through the closed-loop piping system. The system circulates a volume of one million gallons of water per hour, with a supply temperature of 250 °F in the winter and 180 °F in the spring, summer, and fall. The system’s reliability has exceeded 99.99 % since service began.