Numerical simulations on potential application of ground source heat pumps with vertical ground heat exchangers in Bangkok and Hanoi

Abstract

Southeast Asian countries have experienced fast economic growth for several decades. This rapid growth has been accompanied by an increased energy demand per capita. Ground source heat pumps could be a solution to improve energy efficiency. However, there are several concerns with the introduction of this technology. Unlike in four-season countries, where a seasonal balance between cooling and heating demand exists, the use of ground source heat pumps in Southeast Asia is primarily for cooling. The temperature difference between the ground and air is also small. In this paper, we evaluate the first thermal response test results ever performed in Southeast Asia at sites in Bangkok and Hanoi. Borehole heat exchanger models were established on the basis of the apparent thermal conductivities according to the thermal response test results. The borehole heat exchanger models were then used to evaluate the five-year performance of a ground source heat pump in a typical small-sized detached office building under specific climatic conditions. The increasing borehole heat exchanger temperature is unavoidable because of the absence of heat extraction. Consequently, the coefficient of performance decreasing, along with the increasing power consumption, over time. Yet, the results indicating that the ground source heat pump can still provide good thermal performance. We also evaluated the effect of the number of boreholes on the ground source heat pump performance. The results indicate that the maximum coefficient of performance can be relatively improved by 16.1% and 14.9% in Bangkok and Hanoi, respectively, using 10 instead of 6 boreholes.