A Heat-trading Network is a type of district energy system that allows the sharing of heat between a LTHW system and a chilled-water system that serves multiple buildings. Low-temperature Hot Water (LTHW) is a design characteristic of a district energy system that uses low-temperature hot water (between 120oF and 250oF) to deliver heating energy to buildings. Hot water uses less energy and reduces heat losses in the distribution system relative to traditional steam-based systems. In a LTHW system, supply water is distributed via the piping network at temperatures lower than steam. This temperature is closer to the temperature of the surrounding area (e.g. the ground) which reduces the heat loss in the distribution system. LTHW systems also enable the integration of high-efficiency equipment and renewable heating sources, such as heat pumps, heat recovery chillers, solar-thermal arrays, and ground-source heating wells, allowing the system to move and reuse heat instead of making it twice.

Benefits

• Unlocks numerous renewable technologies including ground-source heating, heat recovery, and thermal energy storage.
• Heat-trading Networks use significantly less water and have lower operational, maintenance, and fuel costs relative to traditional district energy systems and/or building-level equipment.
• Provides a path to campus-wide electrification allowing the campus to benefit from the rapid decarbonization of the electricity and the cost declines of wind and solar.

Challenges

• Retrofitting existing district energy systems and/or connecting stand-alone buildings may require significant capital investments.
• Where distribution piping is required, there can be significant physical disruptions to the campus during installation.
• While total input energy will be dramatically lower, Heat-trading Networks will increase campus reliance on electricity.