Utilization of Earth-to-Air Heat Exchanger to Pre-Cool/Heat Ventilation Air and Its Annual Energy Performance Evaluation: A Case Study

Chong Zhang,Liao Li,Wenjie Gang,Feifei Wang,Jinbo Wang

doi:10.3390/su12208330

Abstract

An earth-to-air heat exchanger (EAHE) system utilizes the low-grade thermal energy of underground soil to warm up and cool down the flowing air within an underground buried pipe. Integrating the EAHE system with building ventilation can reduce the energy demand for conditioning ventilation air. The main purposes of this paper are to estimate the year-round energy-saving potential of the EAHE-assisted building ventilation system and provide its design guidelines in a hot-summer and cold-winter climate. A steady-state heat transfer model was proposed to calculate the outlet air temperature of an EAHE and further identify its ability to preheat and precool ventilation air. Influences of depth, length, and diameter of a buried pipe on the year-round thermal performance of the EAHE system were evaluated. The results show that considering the compromise between thermal performance and construction costs of the EAHE system, a depth of 5 m and a length of 80 m are recommended. The EAHE system can provide a mean daily cooling and heating capacity of 19.6 kWh and 19.3 kWh, respectively. Moreover, the utilization of the EAHE system can reduce by 16.0% and 50.1% the energy demand for cooling and heating ventilation air throughout the whole year.

Highlights

Nowadays, approximately 30% and 36% of the total energy use in China [1] and the world [2] is generated by the building sector during its whole life cycle, respectively
Great efforts have been devoted toward the research and development of sustainable and high-performance buildings, in terms of improving building design guidelines [3], using advanced energy-efficient devices [4], enhancing the thermal performance of windows and walls [5,6], adopting a data-driven approach to achieve performance prediction and optimal control [7], taking advantages of renewable energy sources [8], improving indoor thermal comfort [9], integrating the thermal energy storage [10], etc
The results show that the earth-to-air heat exchanger (EAHE) system can provide an average preheating potential of 14 ◦C for the heating condition, and the maximum COP is up to 16.3

Summary

Introduction

Approximately 30% and 36% of the total energy use in China [1] and the world [2] is generated by the building sector during its whole life cycle, respectively. The building sector has been recognized as a significant portion for reducing global energy use and greenhouse gas emissions. Building ventilation is essential for both residential and commercial buildings to satisfy the requirements of indoor air quality and thermal comfort [11]. The minimum ventilation requirement may lead to a large amount of energy consumption for conditioning ventilation air to the required conditions. Over the past several decades, better building design and emerging technologies have been constantly developed to reduce the energy demand of building ventilation

Methods

Results

Conclusion