Energy Performance Evaluation of Shallow Ground Source Heat Pumps for Residential Buildings

Archan Shah,Moncef Krarti,Joe Huang

doi:10.3390/en15031025

Abstract

This paper evaluates the energy performance of shallow ground source heat pumps using the state-of-art whole building energy simulation tool. In particular, the paper presents a systematic and easy to implement approach to model the energy performance of shallow and helical ground heat exchangers and assess their energy efficiency benefits to heat and cool buildings. The modeling approach is based on the implementation of G-functions, generated using a validated numerical model, in a state-of-art whole building energy simulation tool. Both the numerical model and the simulation tool are applied to assess the energy performance of various shallow geothermal systems designed to meet heating and cooling needs for detached single-family homes in California. Specifically, a series of sensitivity analyses is conducted to determine the energy performance of the shallow geothermal systems in 16 locations representing all California climate zones. It is found that the suitability and the efficiency of the shallow geothermal systems vary widely and depend on several factors including their design specifications as well as the climate conditions. Compared with conventional air-to-air heat pumps, the shallow ground source heat pumps can be more energy efficient in most climate zones in California except those locations with extreme weather conditions resulting in either heating or cooling only operation. Moreover, configurations of shallow ground source heat pumps with 16 boreholes with 6.7 m (22 ft) depth are found to be cost-effective in several California climate zones.

Highlights

Ground medium with its deep temperature that remains constant throughout the year has a large capacity to store heating and cooling energy
The results indicate that a 50% increase in soil thermal conductivity results in a 10% reduction in S-ground source heat pumps (GSHPs) cooling energy consumption for a house located in Long Beach
These G-functions are implemented in a whole-building simulation tool to determine the energy performance and cost benefits of shallow ground source heat pumps (S-GSHPs) to heat and cool buildings

Summary

Introduction

Ground medium with its deep temperature that remains constant throughout the year has a large capacity to store heating and cooling energy. The ground is used as a heat source and sink for ground source heat pumps (GSHPs) to heat and cool buildings [2]. GSHPs transfer heat from the ground medium to the building during heating modes but operate in reverse by extracting heat from the building indoors to release it into the ground during cooling modes. GSHPs utilize renewable energy stored within the ground medium to meet the heating and cooling needs of buildings. GSHPs have several advantages when compared with conventional mechanical heating, ventilating, and air conditioning (HVAC) systems [2,3]. Some of these advantages include lower operating and maintenance costs, quieter operation, and low environmental impact. It is estimated that GSHPs use one unit of electricity to transfer five times the equivalent heat units from the ground [3]

Objectives

Findings

Discussion

Conclusion