Abstract
Given the substantial energy use for space cooling in buildings, integrating energy-efficient and sustainable cooling systems into buildings has become increasingly more important. Even though the cooling potential of a near-surface earth-to-air heat exchanger (EAHE) with grass cover was demonstrated in previous studies, the energy savings and environmental benefits resulting from using the EAHE have not yet been quantified. Therefore, in this study, we quantify the energy savings resulting from using a near-surface earth-to-air heat exchanger (EAHE) with grass-covered ground as a precooling unit in hot desert climates. The outlet air conditions of the EAHE during 9 months of the year (March to November), where space cooling is required, are predicted using a 3D transient CFD model, which is validated against field measurements. The EAHE is fabricated from a 1 mm thick aluminum tube with a diameter of 0.15 m and a length of 21.5 m, buried 0.4 m deep. The results showed that the EAHE can cool ambient air by up to 8.5 °C at an air flow rate of 607 m3/h, corresponding to a cooling capacity of 1700 W and a COP of 17. The daily average cooling capacity of the EAHE is about 560 W for an average operation period of 15.1 h per day. When used as a precooling unit for conventional cooling systems, the highest estimated monthly energy savings is 115 kWh, and the estimated annual savings is 741 kWh.
Highlights
The built environment accounts for a considerable portion of the worldwide energy use and greenhouse gas emissions, with a significant increase every year [1]
In ground cooling systems, ambient air is passed through tubes buried under the ground, where heat transfer occurs between the soil and the air in the tubes, and according to the season and time of the day, the air temperature could increase or decrease [7,8]
The objective of this study is to quantify the energy savings resulting from using a near-surface earth-to-air heat exchanger (EAHE) with grass-covered ground as a precooling unit in Doha, Qatar, which has a hot desert climate according to the Köppen climate classification
Summary
The built environment accounts for a considerable portion of the worldwide energy use and greenhouse gas emissions, with a significant increase every year [1]. Between 1990 and 2016, the worldwide energy consumption for space cooling in buildings more than tripled [2]. One energy-efficient approach is using the ground as a heat sink to lower the ambient air temperature for space cooling [4,5]. In ground cooling systems, ambient air is passed through tubes buried under the ground, where heat transfer occurs between the soil and the air in the tubes, and according to the season and time of the day, the air temperature could increase (during winter) or decrease (during summer) [7,8]. A number of recent studies have investigated ambient air cooling using earth-to-air heat exchangers (EAHE), including numerical [9,10,11,12] and experimental examples [13,14,15,16], with the burial depth of the EAHE ranging from 1.5 to 5 m
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