When ASHRAE’s original book on ground-source heat pumps was published 17 years ago, such systems were used mainly in residential settings and designers who used them were seen as risk takers.
Today, the technology is much more widely used having been recognized for its benefits. The lessons learned during that time are incorporated in a newly published book from ASHRAE, “Geothermal Heating and Cooling: Design of Ground-Source Heat Pump Systems (GSHP).” The publication is a complete revision of “Ground-Source Heat Pumps: Design of Geothermal Systems for Commercial and Institutional Buildings,” published in 1997 and recognized as the primary reference for non-residential GSHP installations.
The new book was written by Steve Kavanaugh, professor emeritus at the University of Alabama, and Kevin Rafferty, a consulting engineer, Klamath Falls, Ore. Both have spent the last 25 years focused on geothermal/GSHP work.
“One of the realities of the GSHP industry is that, to some degree, it has been a victim of its own success,” says Rafferty. “Years ago the struggle was to simply get design teams to consider using the technology. Though this is still an issue in some areas, nationally it is far less of an issue than 20 years ago. There is now fairly wide recognition of the benefits of GSHP systems, particularly on the part of building owners in the schools and office building sectors, where the technology has achieved its highest penetration rates. However, there also is a widely held view that anything bearing the name ‘geothermal,’ ‘ground source’ or ‘earth energy’ will produce the desired high-efficiency/low operating cost. As a result, poorly designed systems are often installed and building owners expectations are unmet.”
The book provides benchmarks, design strategies and information necessary for engineers to configure the most efficient and cost-effective systems and avoid problems such as inefficient pumping, high-cost ground loop designs, inadequate outside air provisions, unnecessarily complex control schemes and other common design errors.
In addition to cost and performance data, Kavanaugh provides building owners and their architects the information necessary to ask the right questions and accurately evaluate potential engineering consultants. The net effect is a more cost-effective and efficient design and satisfied building owners.
“GSHP produces superior HVAC system performance and when properly implemented can be cost competitive with many (but not all) conventional systems,” says Rafferty. “They can be operated with simpler controls than traditional HVAC systems, and also can reduce equipment building space requirements, reduce duct work requirements and eliminate the need for external building mechanical equipment.”
As part of the revision, seven of the original eight chapters and appendices were completely rewritten and now include coverage of close-loop ground (ground-coupled), groundwater, surface water, GSHP equipment and GSHP piping. Additional information on site characterization has been added including a new hydro-geological chapter. The final chapter was replaced and the new section contains results of recent field studies, energy and demand characteristics and updated information to optimize GSHP system cost.