Do, Sung Lok (2014-05). Development and Application of a Ground-Coupled Heat Pump Simulation Model for Residential Code-Compliance Simulation in Texas. Doctoral Dissertation.
The intent of this study was to improve residential energy efficiency in Texas by developing an improved tool for home builders and code officers to use for evaluating their designs. It was achieved by developing a new ground-coupled heat pump (GCHP) model for residential systems to be used with the DOE-2.1e simulation program. To accomplish this, this study investigated closed-loop ground heat exchanger (GHX) models, including horizontal, surface water, and vertical GHX models. This study selected a case-study house in Texas which has a custom-built GHX using a combination of a horizontal GHX and a surface water GHX. This study developed a custom-built GHX model for the case-study house to calculate the entering water temperatures (EWTs). The custom-built GHX model was then validated using the measured EWT data from the case-study house. The results showed the monthly average EWTs differences between the measured and calculated EWTs were observed to be about 2.2 F during the heating season and about 3.2 F during the cooling season. Therefore, this study concluded the slightly over-estimated EWTs were acceptable considering the other uncertainties of the field conditions. In addition, a vertical GHX DOE-2.1e model was developed by using the DOE-2.1e FUNCTION command. The g-function values approximated in this study was used for the vertical GHX DOE-2.1e model. To develop a new DOE-2.1e GCHP simulation model, this study then incorporated the vertical GHX DOE-2.1e input FUNCTION within an air-source heat pump (ASHP) simulation module by modifying existing DOE-2 calculation algorithms. To evaluate the new DOE-2.1e GCHP model, this study also developed simplified residential ASHP/GCHP base-case models for Houston and Dallas, using DOE-2.1e, eQUEST, IC3, REM/Rate, and EnergyGauge. The DOE-2.1e simulation results were then compared against the other programs to verify the accuracy of the new DOE-2.1e GCHP model. The comparison showed good agreement in the total site energy use within 3.3 MMBtu/yr (5.3%) differences. In addition, the simulation results showed the GCHP system benefits: for the total site energy savings, 9.7% in Houston and 13.1% in Dallas, and for the heating plus cooling energy savings, 27.3% in Houston and 35.3% in Dallas.