Understand the Potential of Community Heat Pump Systems

Scenarios where Community Thermal Energy Networks (CTENs) Work

Certain types of buildings or communities of buildings might be able to derive more benefits from a community thermal energy network using heat pumps than others. For CTENs to make the most sense, there should be a variety of heating and cooling loads required for the building or set of buildings. Such scenarios include mixed used developments, hospital/healthcare campuses, higher education campuses, and others. Additionally, for CTENs to work, the buildings or campuses must be in proximity to a viable thermal resource. These resources could include land for boreholes/ground coupling, water pipes, sewer mains, waste heat from a datacenter or industrial facility, or even surface water like rivers, lakes or ponds. 

Understanding Your Community’s Potential

New York City Department of Design and Construction (NYC DDC) provides a thorough overview of how geothermal systems can work in urban environments including benefits and design considerations. NYC DDC also developed practical design and installation guide [PDF]; although the guide is written specific to NYC, its guidance and approach can be applied to any urban environment.

CTENs don’t necessarily have to depend on drilling wells into the ground to access thermal resources. In some instances, tapping into water mains can provide necessary thermal resources for CTENs. This document provides examples of heat pump systems that have achieved cost savings or other advantages by tapping into water mains [PDF]. In one example, an elementary school tapped into a local water main. In another example, cities were able to harness lake water to provide a district cooling system. The document also notes that infrastructure improvements to municipal sewer districts can occur during the CTEN implementation and indicates that this model can be viable to achieve energy equity goals. 

In general, facilities or campuses interested in determining viability have several factors to consider. First, assessing the thermal loads that you want the system to offset will be key. CTENs can offset loads from space heating and cooling (HVAC), water heating, and some industrial processes requiring low-grade heat. Assessing these loads -- when they occur, at what magnitude, and their seasonal differences -- will be a key piece of information in analyzing if a CTEN will be suitable. A good first step is to inventory HVAC and hot water equipment in all of the buildings of interest. 

Second, building owners/operators and project developers will need to determine what types of system capabilities they are looking for to address those thermal loads. A variety of system configurations are available and each come with strengths and weaknesses. This study documents the benefits of 5th generation district heating and cooling systems [PDF] and also surveys 5th generation systems in Europe.

And, third, the potential project will need to assess available thermal resources. This document provides a technological overview focusing on a survey of existing systems and addresses the prevalence of various heat sources and refrigerants. In European systems, sewage water and ambient water [PDF] are the most prevalent thermal resources. This document also has an informative breakdown of various characteristics of typical heat sources . Each project will have to consider thermal resources available as well as factors such as temperature, stability, and proximity to urban areas.

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