Evaluation of a novel greenhouse design for reduced cooling loads during the hot season in subtropical regions

Abstract

Greenhouses provide an optimized growth environment for plants. However, providing this environment is energy intensive. In subtropical regions, most of this energy is to cater for the required cooling. The cooling demand is mainly attributed to the entry of excess solar radiation and heat gain through the greenhouse walls. This study proposes a thermally insulated greenhouse that allows the entry of optimum solar radiation levels through negative linear Fresnel lenses located in its roof. The lenses distribute the solar radiation over the plant rows. The performance of the proposed greenhouse in terms of providing the required levels of solar radiation for plant growth and the reduction in cooling load were assessed using ray tracing simulations and cooling load calculations. The results showed that the recommended optimum amount of solar radiation required for tomato growth can be achieved during the hot season inside the proposed greenhouse. In comparison to a conventional greenhouse, the monthly cooling load of the proposed greenhouse was about 80% less. Therefore, the proposed greenhouse can achieve the benefits of a closed greenhouse while overcoming the high cooling demand drawback, in subtropical regions.