Energy efficiency of solar illuminated vertical farms with different illumination strategies

Abstract

Energy efficiency of a solar illuminated vertical farm is investigated considering different illumination scenarios. The analysis considers the energy consumed by a typical vertical farming facility for heating, cooling and lighting with and without ventilation. Different illumination scenarios consider utilizing fluorescent reflectors converting green light, which is reflected by green leaved produce, to red to increase photosynthetic production, IR filters preventing solar wavelengths, which do not contribute to photosynthetic growth, to enter the facility to reduce cooling load, and light emitting diodes used as a means of complementary/main lighting. Through analyzing 5 different scenarios where these technologies are used in different combinations, the contribution of each technology is identified for 22o, 41o and 60o latitudes in the Northern Hemisphere. It was found that using IR filters is the most effective means of increasing energy efficiency, whereas the impact of using fluorescent coating to energy efficiency is limited in presence of supplementary light emitting diodes illumination. Relying solely on light emitting diodes yield a significant increase in energy consumed to grow per kg of crop. High production rate can be achieved using solar illumination with IR filters, fluorescent coatings and supplementary LED lighting with ventilation that can lead to energy savings of 22 %, 28 %, 29 % with respect to solely relying on LED illumination for 22°N, 41°N, 60°N, respectively. Whereas the corresponding savings, when no ventilation is used are 19 %, 18 %, 13.6 %, for 22°N, 41°N, 60°N, respectively.