Performance assessment of sustainable cooling strategies in canarian Greenhouses: Evaluating earth-to-air heat exchanger and rock-bed systems

Greenhouse cultivation plays a vital role in enhancing food security, particularly in arid and semi-arid regions. However, maintaining optimal microclimatic conditions for crop growth during the summer months poses significant challenges. These conditions often require intensive cooling, which is typically reliant on fossil fuel-based energy sources. This increases costs and environmental impact, highlighting the need for sustainable, energy-efficient cooling solutions. This study evaluates the performance of two passive, sustainable cooling strategies, Earth-to-Air Heat Exchanger (EAHE) and Rock-Bed System (RBS), which exploit subsurface thermal properties to control the canarian greenhouse microclimate. A comparative experimental study was conducted using two identical greenhouses equipped with either EAHE or RBS, alongside an uncooled control greenhouse. Lettuce was cultivated in all three, and microclimatic parameters, system efficiency, and crop performance were monitored. Results indicate that at 2:00 PM, average air temperatures at 1.5 meters were 29°C (RBS), 31°C (EAHE), and 40°C (control). Correspondingly, crop yield increased by 47.97% with RBS and 39.45% with EAHE compared to the control. The RBS greenhouse produced the highest plant growth metrics, 23 cm in height, 304.82 g in biomass, and 34 cm in diameter, followed by EAHE (21 cm, 287.28 g, and 31 cm), while the control greenhouse recorded the lowest values (19 cm, 206.14 g, and 19 cm). Both systems demonstrated superior energy efficiency: EAHE consumed 117.6 kWh/year and RBS 235.2 kWh/year, significantly lower than conventional systems (345.6–691.2 kWh/year). EAHE reduced CO 2 emissions by 3.8 tons annually (190 tons over its lifespan), with RBS achieving comparable reductions. These findings establish EAHE and RBS as viable, sustainable cooling alternatives that improve greenhouse productivity while minimizing energy use and environmental impact.