Co-simulation for thermodynamic coupling of crops in buildings. Case study of free-running schools in Quito, Ecuador

Abstract

Rooftop farms can improve a building's thermal and energy performance, especially for uninsulated free-running buildings. The non-refurbished educational building stock lacks indoor comfort related to temperature and high CO2 concentration, and could benefit from the thermal insulation, food security and social cohesion provided by rooftop farms. However, to assess the adequacy of such strategies, building energy simulations need to include the thermal effect of plants. This study develops a novel co-simulation to leverage the transient flow exchange between crops and buildings by incorporating the plant's heat and mass balances in building simulation. This co-simulation allows an online closed-loop computation using Energy Plus for building energy modelling and MATLAB for crops modelling. The latter solves three agronomical sub-models: 1) crop's growth, 2) energy balance, and 3) net photosynthesis. This dynamic crop's growth function reflects how crops development affects heat, mass and CO2 flows. This co-simulation was first applied to assess the thermal coupling of three rooftop farm systems in two free-running archetype schools in Quito, Ecuador. The assessed rooftop farms were: edible green roofs, hydroponic rooftop greenhouses, and thermally integrated rooftop greenhouses. Results showed that rooftop farms are adequate to improve thermal comfort conditions and air quality in classrooms and diminish thermal demand. Integrated rooftop greenhouses achieve the best overall performance with a 42% decrement in thermal load, a 0.7 °C increment in indoor temperature, and a 40% reduction in hours exceeding CO2 concentration limits, despite a 2.94 kWh/m2 rise in electricity demand.