Grouting for vertical geothermal heat pump systems: Engineering design and field procedures manual. Final report

Technical Report · Mon Dec 01 04:00:00 EST 1997

OSTI ID:354799

Grouting of the vertical ground heat exchanger is important for environmental and heat transfer reasons, and is generally accomplished by the placement of a low permeability material into the annular space between the borehole wall and the pipes suspended in the borehole. Backfilling is the practice of placing drill cuttings or other materials into the annular volume, with no specific effort directed toward creating a hydraulic seal. State and local regulations dictate the need for grouting versus backfilling. This manual concentrates on the technical aspects of grouting, including the environmental issues related to grouting, the thermal characteristics of different grouting materials and how the design must account for those, and the practical aspects of grouting for the field technician. Formation conditions are presented where grouting is necessary to assure the quality of the potable water source, while other conditions are cited where only portions of the borehole need to be grouted. Thermal properties of several grouting materials, both bentonite-based and cement-based, are provided as input data to the calculation of borehole thermal resistance. A procedure is provided for the designer of a vertical ground heat exchanger to calculate borehole thermal resistance, and techniques are described to utilize those values in commonly used commercial design software packages. Several sets of field verification data are presented which indicate that the borehole thermal resistance design data are relevant and important in the performance of the vertical u-bend heat exchanger. Finally, procedures are described for the field technician for mixing equipment, pump, and tremie pipe selection. Methods to estimate the volume of grout required for a job are provided. Recommended field procedures for tremie installation and the grouting process are also provided.

• Research Organization: Electric Power Research Inst., Palo Alto, CA (United States); Northern Geothermal Support Center (United States)
• Sponsoring Organization: Electric Power Research Inst., Palo Alto, CA (United States)
• OSTI ID: 354799
• Report Number(s): EPRI-TR--109169
• Country of Publication: United States
• Language: English

Related Subjects

15 GEOTHERMAL ENERGY
BENTONITE
CEMENTS
GEOTHERMAL WELLS
GROUND SOURCE HEAT PUMPS
GROUTING
MANUALS
RECOMMENDATIONS
SEALING MATERIALS
THERMAL CONDUCTIVITY