Potential reduction in water consumption of greenhouse evaporative coolers in arid areas via earth-tube heat exchangers

Abstract

This study aimed to explore the potential of developing a novel cooling system combining a greenhouse and an earth-tube heat exchanger (ETHE). In this system, greenhouse air is circulated through the underneath soil mass to use the deep-soil cooling effect. This was achieved through the following steps. First, soil temperature profile inside and outside the cultivated greenhouse was monitored for almost one year to study the possibility of using deep-soil coldness for cooling the greenhouse air. Second, a prototype ETHE was built to practically investigate the potential reduction in air temperature as the air flows inside the deep earth pipes. Third, a prototype greenhouse was erected to study the ETHE concept. Results from the first experiment revealed that soil temperature at a soil depth of 2.5 m inside the greenhouse offers good conditions to bury the ETHE. The soil temperature at this soil depth was below the maximum temperature (32°C) that most greenhouse crops can withstand. Results from the prototype ETHE showed a slight reduction in air temperature as it passed through the pipes. From the prototype of the integrated greenhouse and ETHE system, reduction in air temperature was observed as the air passed through the ETHE pipes. At night, the air was heated up across the ETHE pipes, indicating that the ETHE was working as a heater. We concluded from this study that greenhouses in arid climates can be cooled using the ETHE concept which would save a large amount of water that would otherwise be consumed in the evaporative coolers. Further investigations are highly encouraged.

Implementation and Performance Evaluation of a Community-Scale Adobe Evaporative Cooling Chamber for Vegetable Preservation

“…Daily water consumption was 100 L for a 1.28 m 3 EC, 2100 L for an EC sand store, and 325 L for a 2-ton EC [4]. This is an opportunity to develop solutions to reduce the amount of required water or for collective problem-solving to enhance efficiency, such as the use of the underground soil cooling effect [16,25] or the soil itself as a construction material.…”

Hourly Simulation of an Earth-to-Air Heat Exchanger in a Low-Energy Residential Building

“…Numerous studies confirmed that considerable energy savings in buildings can be obtained when using that solution. This relates to space cooling [35,36], heating [37,38] and both these modes, especially in the moderate European climate [39,40]. Therefore, the second important direction of research is the assessment of the effectiveness of the solutions applied in buildings in terms of energy, economic and environmental effects.…”