Geothermal Heat Pump and Energy Recovery Applications
ASHRAE Technical Committee 6.8

Scope of TC 6.8

TC 6.8 is concerned with all equipment and systems which collect, store and utilize geothermal energy or fluids for the purpose of heating and cooling, and with the development and application of heat pump systems and heat recovery by refrigeration cycles including system design, operation, and performance (product design of unitary heat pumps and equipment components is excluded).


The ASHRAE Handbook is published in a series of four volumes, one of which is revised each year, ensuring that no volume is older than four years.

TC 6.8 is responsible for the following handbook chapters:

HVAC APPLICATIONS: Geothermal Energy
The use of geothermal resources can be subdivided into three general categories: high-temperature (>300°F [>150°C]) electric power production, intermediate- and low-temperature (<300°F [<150°C]) direct-use applications, and ground-source heat pump applications (generally<90°F [<32°C]). This chapter covers only direct use (including wells, equipment, and applications) and ground-source heat pumps. Design aspects of the building heat pump loop may be found in Chapter 9 of the ASHRAE Handbook HVAC Systems and Equipment.

The ASHRAE HVAC APPLICATIONS HANDBOOK may be purchased from the on-line bookstore by clicking on the highlighted text.

HVAC SYSTEMS AND EQUIPMENT: Applied Heat Pump and Heat Recovery Systems
A heat pump extracts heat from a source and transfers it to a sink at a higher temperature. According to this definition, all pieces of refrigeration equipment, including air conditioners and chillers with refrigeration cycles, are heat pumps. In engineering, however, the term heat pump is generally reserved for equipment that heats for beneficial purposes, rather than that which removes heat for cooling only. Dual-mode heat pumps alternately provide heating or cooling. Heat reclaim heat pumps provide heating only, or simultaneous heating and cooling. An applied heat pump requires competent field engineering for the specific application, in contrast to the use of a manufacturer-designed unitary product. Applied heat pumps include built-up heat pumps (field- or custom-assembled from components) and industrial process heat pumps. Most modern heat pumps use a vapor compression (modified Rankine) cycle or absorption cycle. Any of the other refrigeration cycles discussed in Chapter 2 of the 2009 ASHRAE Handbook—Fundamentals are also suitable. Although most heat pump compressors are powered by electric motors, limited use is also made of engine and turbine drives. Applied heat pumps are most commonly used for heating and cooling buildings, but they are gaining popularity for efficient domestic and service water heating, pool heating, and industrial process heating.

The ASHRAE HVAC SYSTEMS AND EQUIPMENT HANDBOOK may be purchased on the on-line bookstore by clicking the highlighted text.

Comment on the Handbook: ASHRAE welcomes your comments on the Handbook or a specific Handbook chapter.  To submit a comment about any aspect or part of the Handbook series, you can use the Handbook Comment Form.

Review a Handbook Chapter: To provide your feedback about a specific Handbook chapter, you can answer the brief survey questions on the Handbook Chapter Review Form.


Technical committees develop and sponsor technical sessions at the winter and annual conferences. Information about their future technical program is discussed at each TC meeting and at the TC’s Program Subcommittee meeting

ASHRAE publishes papers and transactions from presentations at its conference events. In addition, ASHRAE records most of the seminar sessions from its conferences on DVD. These DVDs are ideal for use at chapter meetings, in university courses, or company lunch and learns. Products available from the most recent conference may be found here.



Technical Committees are responsible for identifying research topics, proposing research projects, selecting bidders, and monitoring research projects funded by ASHRAE. Information about their specific research program is discussed at each TC meeting and at the TC’s Research Subcommittee meeting.

TC 6.8 is sponsoring the on-going research project:
The objective of this project is to provide improved design data and design tools for SWHP systems. The scope includes collection, interpretation, and collation of design data; experimental measurement of convection coefficients on submerged heat exchanges, and development of design tools.


1890-RP: Minimum flow velocities for purging air and debris from hydronic piping systems 

Status: Active Research Project

Start date: April 1, 2023

Duration: 18 months

Description: The objective of this research will be to experimentally determine the required purging velocities for removal of solid objects and air from hydronic piping.  The results will be presented in one or more tables showing the minimum purge velocity required for various materials, various pipe sizes, and in both horizontal and vertical orientations, including testing of a u-bend loop for ground-source heat pump systems.


RTAR-1953: Evaluation of the costs and benefits of integrating ground source heat pumps (GSHPs) with thermal energy storage (TES) for residential and commercial buildings

Status: Research Topic Acceptance Request (RTAR-1953) submitted to the ASHRAE Research Administration Committee (RAC)

Description: This research is to evaluate the costs and benefits of options for integrating TES with GSHP for residential and commercial applications. Integrated TES and GSHP can enable flexible electric demand, reduce energy cost, and enable building decarbonization, all without occupying floor space and compromising thermal comfort. This evaluation will use high fidelity computer simulations and available case studies. The results will provide guidance for designing integrated GSHP and TES system, which can be included in the ASHRAE Handbook.


ASHRAE writes standards for the purpose of establishing consensus for: 1) methods of test for use in commerce and 2) performance criteria for use as facilitators with which to guide the industry. ASHRAE publishes the following three types of voluntary consensus standards: Method of Measurement or Test (MOT), Standard Design and Standard Practice. ASHRAE does not write rating standards unless a suitable rating standard will not otherwise be available. ASHRAE is accredited by the American National Standards Institute (ANSI) and follows ANSI's requirements for due process and standards development. Standards may be purchased at the ASHRAE Bookstore.

TC6.8 is the cognizant committee for Standard 194.
Std.194: Method of Test for Direct-Expansion Ground Source Heat Pumps

Other Activities

TIP: If MTG involvement add here otherwise leave blank.

TC 6.8 participates in a Multidisciplinary Task Group:

Avoided Sources of Energy Consumption Due to Waste Heat Recovery and Heat Pump Technologies
MTG.ASEC will coordinate development of credible quantification methodologies of the avoided electric power generation and/or primary energy consumptions resulting from the application of heat pump and waste energy recovery technologies.


ASHRAE Technical FAQs are provided as a service to ASHRAE members, users of ASHRAE publications, and the general public. While every effort has been made to ensure their accuracy and reliability, they are advisory and provided for informational purposes only, and in many cases represent only one person’s view. They are not intended and should not be relied on as an official statement of ASHRAE. Technical questions not addressed may be submitted to the ASHRAE Technical Services department at

TC 6.8 is cognizant for the following FAQ:

Where can I find information on geothermal energy and ground source heat pumps?